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Evaluation of the National Aerospace Initiative (2004)

Chapter: 3 Access to Space

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Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
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3
Access to Space

CURRENT OPERATIONAL CAPABILITIES

Access to space is an international capability, with many of the world’s countries possessing very capable vehicles. A partial list of countries and their vehicles follows:

United States

Atlas, Delta, Pegasus, the space shuttles of the Space Transportation System, Taurus, and Titan

France

Ariane

Russia

Proton and Soyuz

Ukraine

Zenit

China

Long March

Japan

H-2

Some of these rockets can lift about 18,500 kg to low Earth orbit (LEO), and several are crewrated. A space shuttle can put about 29,500 kg into a due east LEO. Raw lift performance is not the issue. The issues are cost, reusability, reliability/availability, responsiveness, and turnaround time to put assets into space.

The U.S. space launch capability has evolved over nearly 50 years in response to the requirements of military, intelligence, civil space, and commercial users. The U.S. military and intelligence communities have required relatively low launch rates of uncrewed spacecraft to a variety of operational orbits, ranging from low Earth to geosynchronous. Civil space users have also required only low launch rates. So far, commercial users have implemented only uncrewed spacecraft at low launch rates into Earth orbits.

The proliferation of terrestrial fiber optics and increasingly capable and longer life satellites (both commercial and military) have tended to reduce launch rates, thereby inhibiting large new investments in launch vehicles and associated infrastructure. In recent years, fewer commercial launches and foreign (often subsidized) competition have made domestic uncrewed launch suppliers much less economically viable than had earlier been predicted (Antonio, 2003).

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

However, partly owing to the planned evolution of expendable launch systems by the Air Force, the U.S. government currently has available three families of expendable rockets: the soon-to-be-retired Titan IV and the about-to-be-flown Delta IV Heavy for heavy lift, and the old and new families of Delta and Atlas vehicles for medium lift. In addition, two small launchers (Taurus and Pegasus) provide on-orbit delivery of lighter spacecraft. These systems are completely expendable, will support only low launch rates, and are not crew-rated. The medium- and heavy-lift launchers also operate exclusively from two highly vulnerable Florida and California coastal locations, and one of the boosters (the Atlas V) incorporates a Russian-designed and -manufactured liquid main engine.

Our nation has relied for more than 20 years on the only crew-rated reusable launch vehicle (RLV) in the world, the Space Transportation System (the shuttles). Now, two catastrophic failures in 113 flights have reduced the shuttle fleet to three, which are grounded until corrective actions can be implemented, and have severely limited the shuttle manifest. Currently, crew access to the International Space Station (ISS) depends on the Russian space program to provide limited capability with expendable launch vehicles and crew modules. If the ISS is to be completed and to have the full crew complement, the space shuttle will have to be brought back into service or there will have to be an extended delay until a replacement vehicle is available.

This chapter contains at various points 34 findings and 26 recommendations.

PLANNED CAPABILITY

Both the Air Force and NASA are beginning to pursue new capabilities to satisfy their respective mission needs. While potential new systems may differ considerably and are not yet fully defined, many of the underlying technologies are expected to be similar. As stated earlier, raw lift performance is not the issue. The issues are cost, reusability, reliability/availability, responsiveness, and turnaround time to put assets into space. NAI has targeted these issues in its access-to-space (ATS) pillar with a three-phase program of increasingly demanding requirements. Vehicle and supporting system characteristics and, by implication, NAI technology timelines are illustrated in Figure 3-1.

The ATS pillar has identified the common technical efforts and provides a mechanism for cooperation, sharing, and advocacy of these technologies. Included are reusable rocket propulsion, tanks, and airframes; thermal protection systems (TPS); integrated vehicle health management (IVHM); quick turnaround operations; hypersonic air-breathing propulsion; and many others. NASA and Air Force planning are discussed next.

NASA Planning

Future NASA missions are planned to include human spaceflight and logistical support for the ISS, Earth and space science, astrophysics, and exploration of the solar system. In addition, NASA may seek to develop a new launch capability for very heavy lift to facilitate both crewed and uncrewed exploration of the solar system. Until recently NASA had been funding the development of an orbital space plane (OSP), which was to become operational before the end of this decade. Initial capabilities were intended to satisfy ISS crew rescue requirements. Crew transfer capability (Earth to LEO) was planned as a follow-on spiral development. The OSP was to be launched on an existing expendable vehicle modified to become crew-rated. It should be noted that since the OSP was a current vehicle development program and not a technology development program, it was not considered part of NAI. It is only mentioned here for the sake of completeness regarding future planned capability and for its potential to compete for limited NASA resources. However, the vision articulated by President George W. Bush on January 14,

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

FIGURE 3-1 NAI phased approach to space access. Potential system payoffs and requirements. SOURCE: Sega, 2003.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

FIGURE 3-2 Integrated space transportation plan influenced by Presidential Vision announcement of January 14, 2004. SOURCE: Rogacki, 2003.

2004, called for the cancellation of the OSP in favor of a crew exploration vehicle (CEV) to be developed and tested by 2008.1

Like its predecessor, the CEV is initially planned to satisfy the ISS crew transport and eventually the ISS crew rescue missions. By any measure, the CEV development schedule is very aggressive. Compounding the obvious issues of funding and schedule is the apparent requirement (articulated in the Presidential Vision) to use this same vehicle to provide a crewed capability to destinations beyond low Earth orbit. It is assumed that the CEV will not fall under the NAI umbrella, but, like the OSP, it could compete for NAI resources within a tightly constrained NASA budget. This problem could be exacerbated if NASA finds that much of the CEV technology development is NASA-unique—an example would be technologies to support the beyond-Earth-orbit capabilities that would not be needed by the Air Force—and would therefore have to be funded at the expense of other common technologies sponsored by NAI. The President’s Vision calls for retiring the space shuttles in 2010. After that, cargo up-mass and down-mass capability to the ISS will have to come from adapting evolved, expendable launch vehicles (EELVs) to the cargo mission, utilizing future European and Japanese cargo vehicles, or developing a new U.S. cargo capability (Williams, 2000). In parallel, NASA is developing next-generation launch technology (NGLT) to enable a decision on a rocket-based reusable launch system by 2008. Air-breathing hypersonic technology is not baselined for any near-term space access application but is under consideration for a long-term, crewed launch vehicle (Rogacki, 2003). Detailed plans and roadmaps for these new development programs (other than NGLT) were not available to the committee at the time of this writing. The top-level timelines for these activities are shown in Figure 3-2.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

FIGURE 3-3 Military space plane system architecture. SOURCE: Koozin, 2003.

Air Force Planning

The Air Force’s increasing emphasis on missions such as Prompt Global Strike (PGS), Operationally Responsive Spacelift (ORS), and Space Control (SC) may require both rapid-launch, expendable systems and reusable launch systems capable of turnaround times measured in hours rather than weeks or months. A concept for satisfying many of these requirements is shown in Figure 3-3. A potential access-to-space element of the architecture includes a two-stage-to-orbit (TSTO), reusable space operations vehicle (SOV) (booster) mated with either an expendable or a reusable upper stage. The associated development schedule for these vehicles is shown in Figure 3-4.

The Air Force may find a low-cost, time-responsive, expendable vehicle to be a cost-effective solution to meeting certain mission requirements. Upgrades to the current fleet of expendable vehicles may also prove beneficial. However, as demand for a responsive launch capability and the corresponding launch rates increase, reusable launch systems become more attractive, both operationally and economically. The propulsion system for both expendable and reusable systems will remain rocket-based in the near- to mid-term (2004-2018) owing to the immaturity of air-breathing engine technology. It is hoped that near-term demonstration vehicles (e.g., RASCAL and FALCON) will help to advance air-breathing engine technology and should provide data to help determine the feasibility of scaling these engines for medium to heavy lift vehicles.

Because air-breathing hypersonics technology is not baselined for any near-term space access concept but is being considered for longer-term designs (Rogacki, 2003), the committee’s assessments in this chapter focus on rocket-based launch vehicles. The assessment of air-breathing-based launch vehicles is restricted to comments on the feasibility of the basic technology and on the data needed for deciding if air-breathing engines can be applied to launch vehicles for medium and heavy loads.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

FIGURE 3-4 Military space plane roadmap. SOURCE: Sponable, 2003.

Finding 3-1. The United States will continue to rely on rocket-based systems for access to space for at least two more decades. The current expendable rocket families provide adequate lift capability for scheduled uncrewed launches to Earth orbit but will not support emerging military needs for rapid-rate, time-responsive launches. The two latest versions in the expendable rocket families utilize a new U.S. engine (RS-68) of undemonstrated reliability and an engine available only from a foreign supplier (RD-180.) The only reusable launch capability, NASA’s Space Transportation System, is scheduled to be retired by the end of the decade. Owing to the loss of the shuttle Columbia and the resulting Presidential Vision announcement, the plans for crewed flights are undergoing extensive revision. That said, it is anticipated that human flight will be accommodated by the development of a CEV fitted atop a (yet-to-be-defined) booster. Compounding the obvious funding issues are the CEV multimission requirements, the aggressive schedule, and the likely desire to make the CEV compatible with both the Delta and Atlas families of expendables. Although not a part of NAI, the NASA-unique nature of the CEV and resulting demand on the NASA budget may affect NASA’s ability to participate in NAI-sponsored technology development programs. The CEV booster might be further augmented and/or replaced in the next decade by a rocket-based, reusable launch system. Robust, reusable access to space will require a phased flight-test program to demonstrate reliability, affordability, and responsiveness relative to expendable systems. Airbreathing hypersonics technology is being considered for crewed and/or uncrewed launch systems in about two decades.

Recommendation 3-1. The Air Force and NASA need to strike a balance between vehicle development programs and the NAI-sponsored technology development programs. Both organizations should continue to invest in basic and applied research, technology development, demonstration,

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

and implementation leading to new rocket-based capabilities. These investments should address both expendable vehicles and technology appropriate for deploying and operating reusable, rocket-based launch systems. Of near-term importance is the need to ensure the reliability and availability of the propulsion units used by the latest Delta and Atlas expendable boosters. Technologies developed under NAI sponsorship should be infused into the RS-68 under a component improvement program aimed at accelerating the near-term maturation of that engine. The question of assured availability of the Russian-built RD-180 used by the Atlas should be revisited in light of the potential increased demand following the loss of Columbia and the ensuing Presidential Vision announcement.

TECHNICAL FEASIBILITY IN NAI TIME FRAME

This section follows the taxonomy in the draft NAI plan for access-to-space S&T (DDR&E, 2002). It summarizes, in table form, the technical feasibility of each major technology area and its constituent technologies. The committee was hindered in its evaluation by the uncertainty surrounding budget projections. Consequently, the following subsections evaluate the various constituent technologies on the basis of their current maturity and their potential contribution to the overall NAI objectives of cost reduction, launch availability, and increased mission reliability and safety. An individual table is devoted to each NAI-designated vehicle system:

  • Airframe

  • Propulsion

  • Flight subsystems

  • Launch operations

  • Mission operations

  • Software

Each table further divides the vehicle system into major technology areas, which are in turn broken down into the constituent technologies defined (for the most part) by NAI. The tables provide the committee’s assessment of (1) the current maturity of the constituent technologies, (2) the impact of the constituent technology on the major technology area, (3) the likelihood of achieving the desired results, and (4) the overall criticality of the major technology areas. Both the impact and criticality evaluations are based on the committee’s estimate of their contribution to the overall NAI goals—economics, safety, reliability, responsiveness, performance, or benefit to the industrial base. Impact was described as negligible, little, moderate, significant, or extreme. Maturity levels, from 1 to 5, are not to be confused with TRLs; rather, they correspond roughly to the DoD S&T categories:

  1. Basic research,

  2. Applied research,

  3. Advanced development,

  4. Demonstration/validation, and

  5. Engineering and manufacturing development.

According to the committee, constituent technologies with low maturity levels, high impact, and low likelihood of achievement should be afforded special attention if they lie within a major technology area with high criticality. Conversely, technologies with high maturity levels, low impact, and high likelihood of achievement should retain the current level of attention or less, depending on the criticality of the major technology area. The assessments in these tables should

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

help to determine if appropriate attention is being paid to the development of technologies supporting NAI goals.

Finding 3-2. The committee assessed the technical feasibility of NAI technical objectives by examining the main technical challenges and evaluating the NAI response to those challenges. The committee’s assessments are summarized in a set of tables corresponding to the NAI taxonomy.

Finding 3-3. The committee was hindered in its evaluation of financial feasibility by the uncertainty surrounding budget projections.

Recommendation 3-2. NAI should compare its current and projected resource allocations with the information contained in this report to assure appropriate attention is devoted to technologies with the best payoff in terms of costs, benefits, and risk.

Airframe

Depending on their configuration, the airframes of launch vehicles can serve several purposes, including thermal protection; enabling favorable lift-to-drag and thrust-to-drag ratios; housing and protection of onboard electrical equipment, pumps, feed systems, and engine systems; and fuel storage. The airframe is expected to be fully active in aerodynamic control of the vehicle. The external uncooled sections of the airframe may easily experience recovery temperatures in excess of 4000°F at Mach numbers of 8 and above (NRC, 1998). Compounding the mechanical and thermal loads on the airframe are the formation and movement of strong shock waves on the surface of the airframe; hot gas-solid (catalytic) chemical reactions on the surface; and unsteady boundary layers with flow separation. Several challenges must be overcome to operate the airframe effectively and efficiently in a complex aerothermodynamic environment. These challenges include extreme thermal, vibrational, and dynamic loading, and reliability, maintainability, and survivability, along with their impact on maintenance operations. Component and subsystem development leading to space launch capability faces challenges of accurate and efficient simulation and integration (for design), experimental testing (ground and flight), and, most critical, scalability.

Table 3-1 captures the primary technology issues for airframes supporting space launch. First, the committee found that none of the identified technology areas was fully matured. Second, it rated relative criticality as “high” in three of the four major technology areas and as “medium” in the fourth. Third, the thermal protection technologies and design and analysis tools were rated “low” or “medium” with respect to the likelihood of achieving their goals. Further development of the technologies may be costly and risky and will require a multidisciplinary research and development (R&D) framework to ensure system-level optimization. Ongoing and planned R&D activities in each of the three technology areas rated with “high” criticality are summarized below.

Thermal Protection

Three research areas with high-payoff potential have been identified and are summarized in the findings below.

Finding 3-4. The integrated high-payoff rocket propulsion technology (IHPRPT) program has a materials system component that addresses oxygen-compatible superalloys and metal matrix composites (MMC) for liquid oxygen turbopump housing (Brockmeyer, 2003).

Finding 3-5. The IHPRPT program has a three-component ceramic matrix composite (CMC)

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

TABLE 3-1 Status of Technologies for the Airframe System

NAI-Defined Technology Areas

Committee Evaluations

 

 

Constituent Technology Ratings

Major Technology Area

Constituent Technology

Current Maturity Level (1-5)

Relative Impact on Major Tech Area (Negligible, Little, Moderate, Significant, Extreme)

Likelihood of Achieving in Time Frame (Current Funding Level) (Low, Medium, High)

Relative Criticality of Major Technology Area (Low, Medium, High)

Thermal protection

Materials

3

Extreme

Medium

High

 

Leading edges

3

Extreme

Medium

 

 

Control surfaces

4

Significant

Medium

 

 

Acreage surfaces

3

Extreme

Low

 

 

Seals

2.5

Significant

Low

 

 

Hot structure

2

Significant

Low

 

 

Active/passive cooled CMC

2.5

Significant

Low

 

Propellant tanks and feed systems

Reusable metallic

3

Significant

Medium

Medium

 

Reusable cryo composites

1

Significant

Low

 

 

Insulation

4

Significant

High

 

 

Leak detection

4

Moderate

High

 

Integrated structures

Isogrids

3

Moderate

Medium

High

 

Highly integrated subsystems

3

Significant

Medium

 

Design and analysis tools

Integrated design environment (modeling)

2

Extreme

Low

High

 

Vehicle CFD/aerothermal

2

Extreme

Low

 

 

Structural design

3

Moderate

Medium

 

 

Cost and safety analyses

2

Moderate

Low

 

materials initiative addressing thermal protection for bearings, nozzles, thrust chambers, gas generators, hot gas ducting, and turbomachinery (Brockmeyer, 2003).

Finding 3-6. The NAI and the NASA NGLT programs have identified critical and enabling airframe technologies for far-term development and use (McClinton, 2003).

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

Recommendation 3-3. The potential for high payoffs exists in each of these technology research areas, and NAI should continue to support them.

Integrated Structures

The National Aerospace Plane (NASP) and X-33 programs resulted in several advances in integrated structures. Much, however, remains to be mastered to ensure the reliability, safety, and short turnaround time of full-scale systems. Although integrated structures are one of the largest single contributors to improving vehicle mass fraction, very little experience exists in developing approaches and validating techniques for the engineering and manufacture of full-scale integrated structures.

Finding 3-7. The experience base of highly integrated structure, components, and subsystems is very shallow, and much time is required to develop new materials and integration techniques.

Recommendation 3-4. Research should concentrate on the development of (1) tools for the automated optimization of configuration, (2) design processes, (3) material characterization, and (4) testing to validate techniques and processes that enable highly integrated structures. NAI should recognize the time-intensive nature of this research and ensure that the effort is integrated into the overall NAI timeline.

Design and Analysis Tools

Model development is a component of the R&D program managed by NASA in its NGLT program. Design and analysis tools in support of two large areas of research remain underdevel-oped. The first is the hypersonic reentry environment. These tools would be applicable for either a rocket-based or air-breathing reentry vehicle. The second area is the flow path environment for air-breathing hypersonic propulsion, both turbine and nonturbine. The need for robust and high-fidelity design tools and for ground-based testing to verify and validate these tools is well documented.

Finding 3-8. Some examples of numerical tools correlated to national ground testing facilities can be found. In general, numerical tools have not been validated by test data (Candler, 2003; Holden, 2003).

Recommendation 3-5. NAI should support programs to validate numerical tools using ground-based and/or airborne testing.

Summary

Lightweight reusable fuel tanks and highly integrated structures are significant contributors to increasing the overall system margin and the payload fraction of launch vehicles. Since the 1970s, NASA has been performing R&D on hypersonic airframe integration, with intermittent progress. The X-30 NASP exemplifies NASA’s involvement in this area. Key airframe technology shortfalls were identified and risk assessments were made following NASP (McClinton, 2003). The NGLT value stream process—which is an interactive, multidisciplinary process to guide technology development—appears to be mature. Detailed work breakdown structures and various technology shortfalls are identified (McClinton, 2003). However, funding levels were not available to the committee. Generally, these programs have a goal of safe, affordable access to space while supporting DoD’s recently elevated interest in Global Strike, Global Response, and Responsive Access to

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

Space. Some airframe technology metrics, technology readiness levels, technology gaps, and value streams have been established. A disciplined technique called goals, objectives, technical challenges, and approach (GOTChA) has been used to identify and map some technology development targets (DDR&E NAI, 2003). This technique was used to generate a state-of-the-art development plan. However, no detailed GOTChA was observed for the other 17 constituent technology areas listed in the second column of Table 3-1.

Recommendation 3-6. Congruent roadmap taxonomies with consistent metrics and TRL goals should be established between the NASA NGLT program and the NAI GOTChA results.

Recommendation 3-7. Project-level descriptions of airframe technology development approaches should be developed, integrated, and facilitated across government, industry, and university participants.

Propulsion

The state of development of rocket propulsion vis-à-vis that of air-breathing propulsion points to the exclusive use of rocket propulsion in the near and medium term (2003-2015). By 2015, air-breathing propulsion may have advanced enough to put small assets (<500 kg) into LEO as the first stage of a system with a rocket-propelled second stage. Heavy lift (2,000-20,000 kg) with air-breathing propulsion will only mature in the far term (2025 and beyond). Turbine engines must be significantly scaled up in thrust and in Mach number capability if they are to support heavy-lift horizontal takeoff. Also, airframes must be developed with adequate support systems—TPS, structures, materials, controls, and so forth—to be viable. (Development of these support systems would also benefit rocket propulsion vehicles but might go beyond what is required by rocket systems.) The development work to enable a reusable, heavy-lift, air-breathing propulsion vehicle will be extensive, costly, and require basic research in many areas. Therefore, in the near to medium term, reusable, rocket-propelled, heavy-lift vehicles that take off vertically and land horizontally appear to be the best approach to meeting the access-to-space requirement. The assessment in Table 3-2 considers rocket-propelled vehicles and follows the taxonomy specified by the NAI program (DDR&E, 2002).

It should be noted that the NASA NGLT program not only targets reduced cost, faster turnaround time, and more reuse than the current shuttle capability but also specifies a lift capability of 30 to 50 metric tons. Only NASA has embraced this requirement. The cost reduction that might be realized from increased vehicle utilization will not materialize if NASA remains the only entity requiring this high-lift capability.

Finding 3-9. Only NASA specifies a requirement for a reusable, heavy-lift (~40 metric tons) space launch vehicle.

Recommendation 3-8. NASA should reevaluate its heavy-lift requirement. A trade study between high lift capacity and alternative approaches to meeting mission needs utilizing a common vehicle should be conducted, especially in light of the recently demonstrated ability to construct a large space structure, the ISS, in orbit. Adjusting the NASA lift requirement to match that of other users (e.g., DoD) would increase utilization and save billions of dollars for the development of a unique, low-flight-rate vehicle.

A TSTO approach with a liquid oxygen (LOx)/HC first stage and a LOx/liquid hydrogen (LH2) second stage appears to be the configuration baseline on which propulsion improvements are to be made. The goals are to reduce the failure rate, increase specific impulse (Isp), reduce hardware and

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

TABLE 3-2 Status of Technologies for the Propulsion System

NAI-Defined Technology Areas

Committee Evaluations

 

 

Constituent Technology Ratings

Major Technology Area

Constituent Technology

Current Maturity Level (1-5)

Relative Impact on Major Tech Area (Negligible, Little, Moderate, Significant, Extreme)

Likelihood of Achieving in Time Frame (Current Funding Level) (Low, Medium, High)

Relative Criticality of Major Technology Area (Low, Medium, High)

Propellants (oxidizer/fuel)

LOx/HC (O2 rich)

3/5a

Significant

Low

Medium

 

LOx/LH2

5

Significant

Medium

 

 

H2O2/HC

2

Little

Low

 

 

High-energy green fuels

1

Little

Low

 

Propellant management devices

Turbine pumps

3

Extreme

Low

High

 

Engine lines

3

Extreme

Low

 

 

Engine ducts

3

Extreme

Low

 

 

Engine valves

3

Extreme

Low

 

 

Cryo level sensors

4

Significant

Medium

 

Combustion and energy conversion devices

Chambers

3

Extreme

Low

High

 

Nozzles

3

Extreme

Low

 

 

Injectors

3

Extreme

Low

 

 

Gas generators

3

Extreme

Low

 

 

Preburners

3

Extreme

Low

 

Controls

Sensors

4

Moderate

Medium

Medium

 

Health management

2

Significant

Low

 

 

Software

4

Significant

High

 

 

Engine controls

4

Significant

Medium

 

Materials

O2-rich compatible

3

Significant

Low

High

 

High temperature

2

Significant

Low

 

a3 for U.S. propellant; 5 for foreign propellant.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

support costs, increase thrust/weight, and increase mean time between removals (reusable life) (DDR&E, 2002). The committee’s assessment of the technologies contributing to propulsion is presented in Table 3-2.

The Integrated High Payoff Rocket Propulsion Technology (IHPRPT) program has made progress in engine design, materials, and performance in support of the access-to-space goals—for example, the Rocketdyne LOx/LH2 engines, RS-68 and RS-83, and its LOx/RP engine, RS-84. In particular, their integrated powerhead demonstrations (IPDs) have shown significant progress toward longer operating life in an oxygen-rich environment, increased reuse, and reduced cost for LOx/LH2 engines. However, funding limitations have not allowed any investment in LOx/RP engine advances.

Propellants

Both LOx/HC and LOx/LH2 engines are the basic propulsion engines for today’s space access rockets. They are proven and reliable for single-time use (space shuttle main engines are “reusable,” albeit after inspection and refurbishment). To increase the Isp, O2-rich mixtures can be used. However, the temperatures and associated chemical environments created by an O2-rich environment degrade existing engine materials (the exception is the Russian-built RD-180, which still has not been built in the United States). Therefore, engine material development is required to realize the performance increase that can be obtained from O2-rich mixture ratios.

The Air Force is working on an H2O2/HC engine for payloads such as the space maneuvering vehicle (SMV), the modular insertion stage (MIS), and the common aero vehicle (CAV) (Kastenholz, 2003). This fuel combination requires material development to limit its reaction with engine materials. This work is ongoing but severely limited by funding. A decision needs to be made on whether to continue this development or to rely on improving engine performance using LOx/HC and LOx/LH2.

High-energy, green fuels (space propellants that are environment-friendly and nontoxic) are a long-term goal of the NAI access-to-space pillar. No work was reviewed on this subject. Fuels R&D work should be funded if their use is a goal of the program.

Finding 3-10. LOx/LH2 and LOx/HC engines run with oxygen-rich fuel mixtures can achieve better engine performance (Isp).

Propellant Management Devices

Reduced cost, chemical compatibility, higher operating temperature, lighter weight, and longer life (reuse) is needed for all propellant management devices. This can be achieved through design and materials advances. Since design and materials are coupled and funding for materials research is very limited, progress is slow. Certainly advances can and have been made through design alone, but to realize the required engine performance, sufficient funding must be allotted to advance materials as well.

The exception to this conclusion may be cryo-level sensors, which are currently in use. Their reliability can be improved, but that does not appear to entail a large development effort.

Finding 3-11. Advances in materials and design can reduce cost, increase chemical compatibility, enable higher operating temperatures, reduce weight, and increase the operating life of propellant management systems.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×
Combustion and Energy Conversion Devices

NASA and industry are addressing the development of engines using fuel-rich staged combustion (FRSC) and oxidizer-rich staged combustion (ORSC). These programs include advances in combustion devices, turbomachinery, engine systems, and model development (Boeing, 2001). This R&D initiative includes gas seal improvement, elimination of welds, hydrostatic bearings, and simplifying design by reducing part count. This suite of technology improvements should be available for scale-up in the 2010 time frame.

As with propellant management devices, reduced cost, chemical compatibility, higher operating temperatures, lighter weight, and longer operating life (reuse) are required of these devices. In addition, better mixing of the fuel and oxidizer is needed at the proper mixture ratios and flow rates. Significant additional funding is needed for materials development, design, and device testing to realize the engine performance goals on the planned schedule.

Finding 3-12. Advances in materials and designs of combustion and energy conversion devices are needed to reduce cost, increase chemical compatibility, increase operating temperature, reduce weight, and increase operating life.

Controls

Of all the engine components, controls (except for health management systems) require the least development. Increased reliability is the main goal.

On the other hand, the health management system, a key enabler of multiuse engines, is far from fully developed. New sensing methods and prediction algorithms are needed to predict the effects of crack propagation, vibration, mixture ratios, temperatures, and so forth on material health and longevity. Significant development is required in this area, coupled with reliable, low-maintenance designs that afford longer life (reuse) and shorter turnaround times.

Finding 3-13. Engine health management systems have the potential to make significant contributions to the goal of aircraftlike engine operations.

Recommendation 3-9. NAI should define and implement a plan to develop and test an engine health management system that, coupled with reliable, low-maintenance engine designs, will realize the goal of reuse with short turnaround times.

Materials

Advanced materials are the primary key to obtaining desired engine performance. Research, development, and testing of materials (and devices fabricated from these materials) are needed. Advances in ceramic matrix composites have been made, but further advances in these and other materials are necessary to make use of higher-energy fuels in reduced weight engines that function for 100 to 500 launches with minimum maintenance. Funding for materials development is too little to realize long-term NAI goals.

Finding 3-14. Advances in engine system materials are required to realize enhanced engine performance with multiple reuse and fast turnaround times.

Recommendation 3-10. NAI should define and implement a strong materials development and

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

test program that enables the use of oxygen-rich fuel mixtures and results in engine systems with increased margins, long operating life, and reuse with short turnaround.

Summary

Propulsion advancement is a key driver for increasing the payload fraction and reducing cost and turnaround time for launch vehicles. Funding and programmatic emphasis need to be devoted to this area to increase engine operating margins and reliability and thereby realize NAI program goals.

Flight Subsystems

Integrated flight subsystems are a key enabler of increased vehicle performance and operability. Future visions of aerospace vehicles in both the civilian and military sectors are based on plans that require wide-ranging evolutionary changes. In accessing space, the significant difference between future requirements for commercial/civil vehicles and those for the military space plane system is the military requirement for a responsive space lift capability (Sega, 2003). Flight subsystems are impacted strongly by the specific technology goals identified to enable this capability. For example, future military requirements will include aircraftlike operability—that is, activation for service within days and launch within hours; greatly expanded maneuverability over a larger operating regime; significantly enhanced reliability; and much lower operational costs—which will bring revolutionary changes in vehicle reusability, self-management, adaptability, intelligent systems, and modularization. Thus, for integrated flight systems, general access-to-space goals that include reliability, decreased cost, reduced weight, and increased operability will necessitate critical developments of flight subsystems.

Table 3-3 summarizes the committee’s evaluation of the flight subsystems.

Power

Generation. Current power generation systems (hydraulic, electric, and pneumatic) are heavy and inefficient. Several layers of redundancy, necessitated by low reliability, contribute to weight. These systems also require excessive maintenance between flights and are not designed for automated maintenance. Also, some power generation systems use toxic fuels.

NAI Phase I efforts already focus directly on heavy and unreliable hydraulic systems. Phase II will give special attention to increasing the robustness and decreasing the weight of power systems, with a focus on flightworthy hardware in preparation for an eventual Phase II flight test. The committee believes the power system should be a high priority. DoD has already identified it as a key enabling technology (DDR&E, 2002).

Storage. Energy storage is a part of the power system that is also receiving significant attention under Phase I. By Phase II, a less complex system is envisioned—one that includes advanced fuel cells and conformal batteries with decreased maintenance. Phase III is expected to include innovations in battery chemistry that will further increase life and reduce material toxicity. With such a high priority given to this constituent technology so early in the plan and in light of known development objectives, success is likely.

Distribution. Phase I advances in power distribution correlate with those in power generation. Phase I is also introducing a distributed power architecture and, potentially, fault-tolerant photonic

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

TABLE 3-3 Status of Technologies for Flight Subsystems

NAI-Defined Technology Areas

Committee Evaluations

 

 

Constituent Technology Ratings

Major Technology Area

Constituent Technology

Current Maturity Level (1-5)

Relative Impact on Major Tech Area (Negligible, Little, Moderate, Significant, Extreme)

Likelihood of Achieving in Time Frame (Current Funding Level) (Low, Medium, High)

Relative Criticality of Major Technology Area (Low, Medium, High)

Power

Generation

4

Extreme

High

High

 

Storage

3.5

Extreme

High

 

 

Distribution

4

Extreme

Medium

 

 

Photonics

1

Moderate

Low

 

Actuation

Photonics

2

N/A

Medium

Medium

Vehicle management

Adaptive GNC

2

Moderate

Low

High

 

Sensors

3

Significant

Medium

 

 

Hardware obsolescence planning

3

Significant

Medium

 

Thermal cooling

Materials

4

N/A

High

Low

Vehicle health

Sensors

3

Extreme

Medium

Medium

 

Prognostics

2

Significant

Low

 

Autonomous control of flight mechanics

 

2

N/A

Low

High

OMS/RCS

Propellants

3

Significant

Medium

Medium

 

Ignition systems

3

Significant

Medium

 

NOTE: GNC, guidance, navigation, and control; OMS, orbital maneuvering systems; RCS, reaction control system.

controls. Power distribution, particularly with photonic control, is not as well developed as power generation and storage.

Photonics. In Phase I, which is relatively short, NASA and AFRL will attempt to exploit current subsystem technologies. Reliable photonics for vehicle management is a 6.2 research effort, so photonics is not expected to be available until at least Phase II. Ground demonstrations are designed to validate the reliability of flight-critical optic sensors for optically controlled power switching. Not only must the key technologies be matured, but photonic optics must be integrated with the vehicle management system. Flight test will ultimately be dependent on the critical reliability of the

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

photonic vehicle management system (VMS). NAI is relying heavily on the successful development of photonic technologies (DDR&E, 2002).

Finding 3-15. In the near term, the control of power generation, storage, and distribution depends on currently available technologies. Future capabilities will rely on the integration of photonically controlled power generation, distribution, management, and actuation systems coupled with the photonic VMS.

Actuation

Consistent with the evolution of power systems, Phase I is beginning a shift from hydraulic to electric actuation systems. Integrating power and actuation should reduce risk in the overall system. Demonstration of increased reliability in actuating components (including aero surfaces and thrust vector control) is also expected be accomplished in Phase I. Fiber-optic components and sensors for control will be introduced in Phase II. Investments are expected in technologies to improve motor efficiencies. Phase III goals target efficient, long-life components.

Vehicle Management

As noted in the draft access-to-space S&T plan (DDR&E, 2002), Phase I focuses on tailoring state-of-the-art aircraft technology and adapting it for reusable lift vehicles and space environments. Ground demonstrations are used to assess system-level components. As such, a number of programs in the vehicle management system (VMS), integrated vehicle health management (IVHM), and guidance, navigation, and control (GNC) will be brought together and validated in a simulation environment. This is expected to establish GNC technologies that will lead to fully autonomous systems. The initial phase relies on off-the-shelf components. However, 6.2 research in this same time frame includes development of a reliable photonic vehicle management system for data acquisition, dissemination, computation, and control. By Phase II, the vehicle management system is to be integrated with a vehicle health monitoring system having sensors, intelligent algorithms, and software for prognostics and diagnostics at a subsystem level. As components degrade, the VMS/IVHM system will identify performance penalties and implement adjustments. This is a revolutionary development program and, again, will rely on a photonically integrated architecture with validation using high-fidelity, ground-based simulation. A photonic VMS will also bring decreased weight and improved reliability. “Building” the VMS system involves information technology and advances in computational capability, both of which have received a lot of attention and achieved incredible progress in a wide range of commercial activities.

Finding 3-16. NAI applications will benefit (technically and, possibly, in terms of reduced costs) by exploiting computational (both hardware and software) developments in the commercial sector.

Recommendation 3-11. NAI should assess its current vehicle management system development program to ensure that technology available in the civilian sector is leveraged as much as possible.

Advanced GNC is required for integration with the VMS system. However, Phase I expectations are more modest: a fault-tolerant system and validation of tools for GNC design. Investments in Phase II are planned to support the development of intelligent and adaptive VMS systems, including 6.2 research in autonomous and adaptive GNC. Ground demonstrations and simulation will integrate the VMS with advanced flight GNC and will incorporate photonic VMS. Correspondingly, adaptive GNC implies real-time mission planning and replanning. Ground-based simulation

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

and flight testing will validate the integrated adaptive system. This integrated, intelligent, adaptive photonic VMS-GNC technology is universal across the three NAI pillars. Any delay in the research and/or technology development timeline will have impacts across all three pillars.

Reliable optic sensors for control of the VMS system are flight-critical components. They must be fully mature and reliable if they are to be integrated into the VMS.

The hardware developed for future flight systems is expected to have longer life, with less maintenance and a longer time between failures. A modular framework supports these requirements and allows component elements to be updated as needed. A response to hardware obsolescence should be incorporated into the system/component development plan.

Finding 3-17. Integrated, intelligent, adaptive photonic VMS-GNC technology is universal across the three pillars of NAI. Any delay in the research and/or technology development timeline will have impacts across the entire NAI program. These systems will in large part be validated for flight using ground-based simulation tools.

Recommendation 3-12. The development timelines of the VMS-GNC program should be evaluated to ensure that the technology is ready whenever it is needed to achieve an integrated system and flight test within a decade.

Recommendation 3-13. Programs for vehicle simulation tool development should be periodically evaluated to ensure that they keep pace with the hardware and component development programs.

Thermal Cooling

Thermal cooling for local and distributed power systems is noted as a critical R&D area in the draft NAI plan for access to space (DDR&E, 2002). Thermal control is required to maintain reliability of high-temperature components including the electronics. By Phase III, a matrixed thermal management architecture is anticipated with high-performance active/passive thermal management. Although thermal cooling is a significant issue, R&D in other technology areas is more critical. Thus, in the context of flight subsystems, thermal cooling technologies can be effectively leveraged from other R&D programs.

Vehicle Health

Similar to the engine health monitoring discussed in the section on propulsion, a vehicle subsystem health management system to continuously monitor, diagnose, and prognosticate the vehicle status will be critical to improving vehicle availability. Initially, in Phase I, the ground demonstration for VMS and IVHM will integrate critical GNC technologies with flight information, with a focus on the robustness and reliability of the health monitoring systems. Ground demonstrations will then incorporate the integrated IVHM system in preparation for flight test. The IVHM system is designed to monitor the health of the power, actuation, and other subsystem components and then integrate the information into the VMS. However, sensor development is necessary to meet the requirements of the VMS/IVHM system.

Prognostics capability also relies on component sensors (hardware), plus intelligent and adaptive algorithms (software). Once implemented, the VMS/IVHM system must meet reliability and performance specifications.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×
Flight Mechanics and Autonomous Control

Flight mechanics, encompassing the control, navigation, and guidance of vehicles, is noted by NAI as a critical R&D area. It impacts operability and, to some extent, reliability as well, particularly with expanded flight regimes. Planned ground tests in Phase I include the modeling and simulation of autonomous flight mechanics capabilities in a virtual environment. This is also an area designated for 6.2 research in Phase II. Flight mechanics modeling is also critical to the development of the VMS/IVHM system—for example, in development of the prognostics capability. Responsive autonomous mission planning and replanning imply flight mechanics as part of the advanced, adaptive GNC system. By the Phase II flight test, a real-time autonomous/ adaptive GNC system that relies solely on vehicle information will incorporate flight mechanics algorithms. This capability will include abort contingencies and real-time response. A significantly advanced software validation and verification program must also be in place as early as possible. By Phase III, a sophisticated integrated system is planned to incorporate nanotechnology for computing.

Orbital Maneuvering System/Reaction Control System

The elimination of toxic propellants is a high priority. A shift toward more electric-actuation systems also reduces the operational burden by eliminating costly and potentially unsafe maintenance requirements. The evaluation of ignition systems is based on an overall integrated OMS/RCS system actuation, control, and reliability assessment.

Launch Operations

In the launch operations arena attention has been concentrated on work site safety, environmental compatibility, and reductions in vehicle-unique operations, with a corresponding reduction in the overall number of operations and their labor intensiveness. “Aircraftlike operations” has become the mantra of those hoping to instill a new, cost-effective method of performing launch operations. By almost every metric, the process of planning, preparing, and launching a rocket is vastly more expensive and cumbersome than similar activities for even the most notoriously complex and archaic aircraft.

Launch vehicles operate in a much more demanding environment than that in which typical aircraft operate, and they must achieve a much higher level of performance. By any measure (e.g., weight, cost, payload fraction), the threshold of adequate performance forces the designer to narrow the gap between the acceptable operating point and the ultimate physical limit. It is for this reason that launch systems are designed with much smaller operating margins. This lack of margin in launch vehicles (as compared with more forgiving aircraft) is recognized as the fundamental reason for the great disparity in operating costs. Consequently, it is advances in the basic design and engineering of each vehicle that will eventually result in the biggest savings in launch operations. Adding robustness to the vehicle will allow mission planning, ground processing, and flight operations to more closely achieve the efficiencies that new technologies will enable. Because some of the biggest launch process drivers are unique to specific launch vehicles, it is difficult to imagine a complete set of generic areas where advances (cost reductions) can be made independent of the vehicle configuration. Indeed, the processes and technology thrusts must be traceable and scalable to the envisioned vehicle.

It seems that NAI has recognized this fact. It has embarked on a series of technology investigations to enhance the operating tempo and reduce the costs of traditional launch processes.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

TABLE 3-4 Phase I and Phase II Technology Goals for Various Launch Activities

Activity

Baseline (STS)

Phase I Goals

Phase II Goals

Propellant management

3 hours

2 hours

1 hour

System assembly

~4 months

24 hours

4 hours

Launch pad operations

2-3 weeks

24 hours

4 hours

System refurbishment

100,000 man-hours

7,500 man-hours

1,200 man-hours

Mission operations

100s of people

30 people

15 people

Range reconfiguration

48 hours

24 hours

12 hours

 

SOURCE: DDR&E, 2002.

The overall ATS [access to space] goals are 7-day turnaround time and $10M marginal sortie cost for Phase I and 1-day turnaround time and $5M marginal sortie cost for Phase II. The thrust areas include propellant management, system refurbishment, system assembly, launch and pad operations, mission operations and range operations. Reference data, based on information obtained from the NASA Kennedy Space Center (KSC) for the space shuttle system, was used as baseline capabilities in the six areas for a reusable launch system. The NAI ATS Operations Technology portfolio only addresses improvement from operations technology enhancements and allocates process improvements to be investigated during system design & development. (DDR&E, 2002)

Top-level goals are depicted in Table 3-4. Additional Phase I goals copied from the draft plan require the launch operations to be accomplished in 24 hours. Six hours are allotted for damage assessment and an unspecified number of hours for refurbishment. Operations identified as labor-intensive include postflight inspection procedures, high-maintenance acoustic suppression systems, elaborate exhaust management systems, and umbilical inspection/refurbishment/checkout. Approaches to meeting these goals include durable, energy-absorbing materials, nonpyrotechnic hold-downs, fly-off disconnects, and intelligent sensor and inspection systems (DDR&E, 2002).

Another Phase I goal is to accomplish mission operations with no more than 30 people. NAI says that the approaches to overcoming the challenges are advanced control and monitoring systems, enhanced decision models, advanced weather instrumentation, rapid mission planning, simulation and certification, and operations control center simulation.

Several programs are under way to explore methods and procedures for reaching these goals. Objectives defined by AFRL for the integrated high-payoff rocket propulsion technology (IHPRPT) program are to develop affordable technologies for revolutionary, reusable and/or rapid response military global reach capability; sustainable strategic missiles; long life or increased maneuverability; and high-performance tactical missile capability. IHPRPT includes specific goals for launch operations in 2015, 2020, and 2025, with reductions in operations costs from 15 to 45 percent for expendable launchers and from 2- to 20-fold for reusables (DeGeorge, 2003). DARPA’s RASCAL program is attempting to demonstrate a launch cost of $750,000 per mission on a recurring basis (~$2,000 per pound to orbit) (Singer, 2003). NASA’s NGLT X-43 demonstrations are primarily engine focused but are also proposed for enabling durable, intelligent TPS, an all-electric launch system with health management, and a space-based launch tracking system (Lyles, 2003).

The NAI programs and plans for launch operations are assessed in Table 3-5. The evaluation of all but one of the technology areas can be applied to either a vertical or a horizontal takeoff vehicle. The evaluation of the Automated Ops technology area is based on a vertical launch vehicle. It is assumed that achieving or approaching these goals would result in reducing marginal sortie costs. Reusable launch vehicle (RLV) marginal sortie costs are a legitimate target of the NAI ground operations research. It is the goal of NAI to reduce the marginal sortie cost for a reusable launch

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

TABLE 3-5 Status of Technologies for Launch Pad Operations

NAI-Defined Technology Areas

Committee Evaluations

 

 

Constituent Technology Ratings

Major Technology Area

Constituent Technology

Current Maturity Level (1-5)

Relative Impact on Major Tech Area (Negligible, Little, Moderate, Significant, Extreme)

Likelihood of Achieving in Time Frame (Current Funding Level) (Low, Medium, High)

Relative Criticality of Major Technology Area (Low, Medium, High)

Weather prediction

Winds aloft

4

Little

High

Medium

 

Lightning prediction and control

2

Significant

Low

 

Automated ops

Umbilical

3

Significant

High

High

 

Hypergolic fuels

2

Significant

Medium

 

 

System calibrations

4

Moderate

High

 

 

Ground and range ops design and analysis tools

4

Moderate

High

 

Integrated range network architecture

Onboard range safety

4

Extreme

High

Medium

Responsive reconfiguration

3

Moderate

Medium

 

Intelligent inspection

TPS acreage

1

Extreme

Low

High

 

Health management

2

Significant

Low

 

Security unauthorized penetration

Physical

 

N/A

 

Low

Electronic

 

N/A

 

 

system from approximately $300 million per sortie to $10 million per sortie (DDR&E, 2002). A majority of the reduction comes from a reduction of manpower for supporting flight and ground operations and the elimination of expendable elements and hazardous operations.

Finding 3-18. NAI defines the RLV marginal sortie cost to include salaries for all manpower during flight operation and ground turnaround operations, range costs, and propellant and other consumable costs. Although marginal costs are an important metric for the cost effectiveness of a system, marginal costs alone do not provide adequate insight into the cost of ownership. Total life-cycle costs combine marginal costs with the cost of money and the cost of acquisition, providing greater appreciation of system affordability. The attempt to reduce ground operation costs through the development of highly automated systems could require sizable expenditures. The cost effectiveness of such an investment is a strong function of flight rate and may not be justified when considered in the light of total life-cycle costs.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

Recommendation 3-14. NAI should evaluate all potential cost-saving ground operations technologies against a cost model that includes nonrecurring acquisition costs and the cost of money.

Recommendation 3-15. NAI should evaluate the anticipated advantages and disadvantages of both reusable and expendable launch systems against a total cost model that includes nonrecurring acquisition costs, the cost of money, and other operational advantages.

NAI has planned an Operations Technology Roadmap encompassing six broad technology areas that are considered traditional cost drivers. Two ground demos and one flight demo are planned through FY 2014. Appendix D provides a brief summary of currently planned demonstrations. Significant results from system-level ground demonstrations that would be applicable to a wide range of potential vehicle configurations are unlikely. Although individual technology demos are useful, system-level ground demonstrations are costly. Going through the effort to combine individual technologies into a system-level demo might not be a cost-effective use of resources this far in advance of the known operational configuration.

Finding 3-19. It is difficult to show launch operations traceability and scalability without a further definition of the eventual vehicle configuration.

Finding 3-20. It is likely that a favorable cost/benefit ratio can be achieved by designing robustness into the vehicle.

Finding 3-21. The committee was not presented with evidence to validate the vehicle touch labor, marginal sortie costs, and turnaround time goals. It is not clear that achieving these goals will result in the most cost effective and operationally relevant launch capability, especially when considering the nonrecurring costs.

Finding 3-22. Traceability from ground demonstration to operational system is difficult without a clear understanding of the operational vehicle’s final configuration.

Recommendation 3-16. NAI should evaluate the cost/benefit ratio of the two ground demonstrations. Consider concentrating resources on the flight demo.

X-42

The X-42 is envisioned to be a flying testbed for validating selected technologies developed since the late 1980s. Of the numerous test programs initiated over the last two decades, only one (the DC-X/A) has made it to flight status. Consequently, a significant investment in technology has gone untested in flight. NAI plans to correct this situation using the X-42 flight test vehicle.

In addition to being an environment simulator for airframe and flight subsystems technologies, NAI advertises that the X-42 will be used to evaluate improved technologies and approaches for fighterlike operability in a military space plane (MSP) type system. If designed properly, it can also be used as a payload integration testbed, enabling flight testing of the next generation of air-breathing propulsion technologies.

Flying demonstrators are ideally very traceable and scalable to a follow-on operational system. As envisioned today, X-42 would be scalable to the second stage of a TSTO space plane. Scalability ensures that component technologies will be developed and flight tested in environments relevant to the operational end system. NAI believes that the subscale nature of the X-42 and its ability to launch from the ground greatly simplify the complexity of the system—that is, subscale existing

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

engines are adequate, flight lasts only 10-20 minutes, reaction control system (RCS) usage is limited, there are few or no auxiliary power units (APUs) and no need for on-orbit subsystems, and so on (DDR&E, 2002). It is reasonable to expect that a ground-launched test vehicle will simplify the effort as compared with an air-launched vehicle by eliminating the carrier aircraft restrictions, interface complications, and aerodynamic interference issues. Unfortunately, past experience has shown that the subscale nature of the X-42 will bring very little simplification to the vehicle. In fact, it will most likely introduce an entire new set of complexities related to scaling (e.g., thrust to weight differences). Furthermore, hanging a test engine on a test vehicle is contrary to standard and prudent flight test practice.

Finding 3-23. A flight demonstration is long overdue. However, X-42 (and potentially the X-43 series) test objectives appear to be oversubscribed.

Recommendation 3-17. NAI should limit the claimed X-42 objectives to a more reasonable number. Likewise, if the X-43 series (discussed previously) includes enabling durable, intelligent TPS, an all-electric launch system with health management, and a space-based launch tracking system, as advertised by NASA (Lyles, 2003), then it, too, will be overburdened. Too many objectives will dilute the effectiveness of each objective, increase overall risk, and increase the probability of failure.

Finding 3-24. NAI has inherited a plethora of planned ground and flight demonstrations from all three military services and from NASA and DARPA. These demonstrations address various aspects of the technologies necessary to advance the NAI access-to-space pillar.

Recommendation 3-18. NAI should strive to ensure that all these demonstrations are clearly defined, make significant contributions to the engineering and scientific knowledge base, and are adequately funded to achieve the desired objectives.

Weather Prediction

Weather prediction and monitoring play a big role in safely launching and servicing spacecraft today. Upper-level winds, lightning, surface winds, and ceiling all play havoc on launch and landing days. In addition, military operations are going to demand systems capable of flying in more adverse weather. Therefore, the ability to predict weather conditions with great accuracy in unstable atmospheric situations will be required. These conditions will need to be known during vehicle ascent and also during descent from orbit. Some of these obstacles will be partially addressed by new vehicle design requirements (near-all-weather capability, adaptive avionics suites, etc.), but there will always be a need for predicting weather and induced lightning that could jeopardize the safety of the mission. Everyday work is also impacted by local weather conditions when lightning storms move into the launch area and all outdoor activity is curtailed. All of these demands point to the need for more accurate forecasting to be available to operators and mission planners in real time. The criticality of weather prediction has been rated at “medium” due to the potential mitigating effects of other operational techniques (such as utilizing multiple launch sites or inland launch sites and pad protection facilities.)

Automated Operations

Specific developments in this area tend to be vehicle-architecture-specific. For example, number of stages, stacking orientation, ground/air/rail launch, and other factors all influence the degree

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

of automation and the potential to automate. The NAI plan proposes to examine emerging system architectures for ground-handling requirements and approaches, including automated mating and assembly, component sensing and locating, and rapid ground power connections.

Umbilicals containing propellant, electrical power/signals, and cooling fluid connections require a significant amount of attention to maintain in reliable states. NAI intends to develop smart umbilicals to drive down the recurring cost and support high-tempo operations. These devices will automatically align themselves to the correct mating position and then perform a built-in test function. Nonpyrotechnic release technologies will be incorporated into the umbilicals to avoid the serial processing generally required when handling hazardous materials. Research into the automated handling of hypergolic fuels will also be initiated. The criticality value assigned to system calibrations is due mainly to the need to calibrate flight safety-critical landing aids. The overall criticality of automated operations has been rated “high” due to its significant contribution to manpower reduction and safety enhancements.

Integrated Range Network Architecture

Current range safety tracking and communication systems at the Eastern Test Range are based on 1950s technology. These systems, located near the launch site and spread many miles down-range, are very expensive to operate and maintain. Another hindrance is their inability to handle more than one launch vehicle in any 48-hour period. A space-based range architecture would provide a flexible network of tracking and communication links, enabling global launch operations. Furthermore, the only precision landing aid available at the Eastern Range is an antiquated microwave landing system used by the shuttle. Future RLVs will most likely incorporate a differential Global Positioning System (GPS) system owing to its lower costs, increased reliability, and growing acceptance as a global standard precision landing aid. NAI is planning improvements to ground sensors and instrumentation to alleviate the inflexibility of range tracking assets, increase their accuracy, and reduce operating costs. Several projects are planned to accomplish these tasks:

  • Passive metric tracking system,

  • Advanced landing systems using differential GPS,

  • Automated range resource management system,

  • Mobile launch head range system,

  • Integrated launch head air-sea surveillance system, and

  • Range dispersion monitoring system improvement.

Finding 3-25. Although large investments in range upgrades have been made over several decades, fundamental advancements in range functions and techniques remain elusive. NAI planning and resources appear to concentrate on improvements in existing systems. Real cost reductions will only come from a genuine paradigm shift in range operations.

Recommendation 3-19. NAI should continue to rethink the fundamental requirements and services provided by the range organizations. Experience gained in many years of military remotely piloted vehicle operations should be incorporated into the range concepts of operation.

Finding 3-26. The development of a secure advanced differential GPS landing aid will provide the most universal benefits applicable to all future RLVs.

Recommendation 3-20. NAI should concentrate appropriate resources to develop a secure advanced differential GPS landing aid.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

The criticality of integrated range network architecture has been rated “medium” owing to the paradigm shift required to produce significant cost savings.

Intelligent Inspection

Systems to detect and isolate component or system failure have been in use for many years. Integrated vehicle health management (IVHM) systems not only perform those functions but also should identify part degradation and assist in vehicle maintenance. They could also enable a system to mitigate a failure by reconfiguring itself well enough to continue the mission or safely abort. An often used example is the detection of an impending engine failure during a multiengine assent. Failing engines may be throttled back (or completely shut down) prior to failure and other engines throttled up to compensate. The IVHM system could also notify the vehicle management computer (VMC) to alter the flight trajectory into a more benign environment. Development of such systems could help increase system safety and mission reliability. It could also greatly reduce operation costs by driving down scheduled maintenance and inspection hours. This technology will show tremendous benefits if and when it progresses to the point of predicting a premature component failure by examining real-time sensor data. Reaching this level of sophistication will require a significant investment. If the technology succeeds in this task, other subtle questions may surface. For example, will the decision authority authorize the next flight if the IVHM predicts the failure of a critical component on the second flight? Questions such as this should be fully examined in the course of this research. If successful, the payoff for developing IVHM systems could be substantial. Autonomous systems with embedded knowledge enhance operability while reducing highly skilled touch labor and enhance safety of hazardous operations and greatly enhance the overall responsiveness of the system.

Automated postflight inspection is another avenue toward significant cost savings. Specifically, reducing the time and manpower required for the inspection of large-acreage TPS and cryogenic assemblies could reduce the turnaround time and recurring costs of any RLV. These vehicles typically endure damage from both launch and orbital debris. TPS must be revalidated prior to each flight. Automatic detection and evaluation of impact damage via a scanning sensor would be of great benefit. The criticality of intelligent inspection has been rated “high” due to a significant potential reduction in turnaround time and postflight manpower requirements.

Security

Space systems require protection against unauthorized penetration of both facilities and electronic systems.

Finding 3-27. Although the security of space systems is vitally important to successful operations, very little security technology is unique to the space operations arena.

Recommendation 3-21. NAI should harvest and incorporate advances in security technology and techniques from sources outside the traditional aerospace community.

The criticality of security has been rated “low” since the technologies generated elsewhere can be imported as needed.

Summary

Launch operations is a key driver for total space lift costs. However, spending in some areas should be gated until a clear understanding of the final vehicle configuration emerges. Other

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

technologies should be actively pursued to ensure they are ready when needed to realize the NAI program goals.

Mission Operations

The major NAI needs identified for mission operations are rapid mission planning (for the military), rapid response (for the military), on-orbit servicing and orbit transfer capability (both military and civilian), and affordable launch (both military and civilian). Affordable launch was discussed previously.

Rapid mission planning for military operations is required to respond effectively to threats. The need for situational awareness and for flexible systems that can adapt in near real time to changing mission requirements is increasing (Morrish, 2003). Space technologies for command, control, communications, computers, intelligence, surveillance, and reconnaissance (C4ISR) were identified as part of NAI but are beyond the scope of this access-to-space section. However, the ability to plan and launch missions effectively depends on global situational awareness and inputs from C4ISR. The ability to rapidly plan missions requires communications architectures matched to the situational awareness.

Efficient mission planning requires automated tools to trade off mission options. These tools must be capable of rapidly making complex trades between options for responding to threats. Tools are being used now by Operationally Responsive Spacelift (ORS) for long-range planning and launch vehicle requirements and evaluation. It is not clear if these tools are adaptable to real-time response planning—for example, which assets to launch in response to a given situation. NASA has extensive mission-planning tools for its missions, but these are either not designed for rapid response, or are extremely specialized to science missions. Mission planning tools must take into account surveillance and communications before the onset of hostilities, which space assets are capable of responsive launch and on-orbit checkout, the ability to launch on schedule (prehostilities), the ability to plan for persistent on-orbit presence, quick reconstitution of on-orbit assets, and quick launch to support tactical needs. These tools will need to be developed or upgraded from their current status.

Range tracking, that is the detection of the position and condition of vehicles during launch and landing, is currently a safety requirement. This function (see also “Launch Operations,” above) is currently tied to fixed range systems for launch vehicles, but there is a desire to make the tracking of launch and landing independent of fixed locations to provide flexibility in launch and landing location and to facilitate rapid response (Morrish, 2003). The NASA tracking and data relay satellite system (TDRSS) and the Global Positioning System (GPS) were identified as the basis for such systems. DARPA’s Responsive Access, Small Cargo, Affordable Launch (RASCAL) program includes an attempt to demonstrate this capability.

DARPA’s RASCAL also proposes to demonstrate 24-hour mission turnaround and 1-hour scramble with aircraftlike sorties. RASCAL is to demonstrate a system that can launch microsatellites into any Earth-centered orbit without requiring fixed, ground-based ranges. A goal is to demonstrate mobile operations from any coastal airfield with a 5,000-ft runway and a system that can adapt in near real time to changing mission requirements.

Advances in orbit operations are required by both the Air Force and NASA to increase capability (e.g., for the Space Control mission) and, in turn, reduce costs. Both are focused on moving and servicing space assets. DARPA currently has a program called Orbital Express (it is not part of NAI), which is targeted for demonstrating the technical feasibility of robotic on-orbit servicing, robotic fueling, and orbital replacement unit (ORU) replacement by 2006. Operationally Responsive Spacelift (ORS) requires an orbital transfer capability to reposition/boost orbital assets and perform spacecraft servicing. The AFRL Space Vehicles directorate is working on a military space plane,

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

which it defines as a space operation vehicle (booster), a space maneuver vehicle (a reusable transfer stage), a modular insertion stage (expendable for affordable space access), and a CAV (for Prompt Global Strike) (DDR&E, 2002).

DARPA’s Orbital Express, plus NASA’s planned work on an orbital maneuvering vehicle and its automated rendezvous and docking experience with the Russian Soyuz and Progress vehicles and others, make many of these technologies fairly mature. No funding has been identified for the XTV orbital transfer vehicle shown as part of NASA’s Space Architecture, but the Space Transportation System and Russian technology base should make crewed XTV operations mature. Most existing DoD assets are probably not serviceable, so on-orbit servicing technology would only be applicable to certain future assets that show some economic or performance advantage to being designed for on-orbit servicing.

The technology requirements for on-orbit operations are focused on autonomy and associated technologies to make autonomous systems work. Specific technology needs are identified in Table 3-6.

Finding 3-28. Mission operations are hindered by the long-lead planning, antiquated range processes and requirements, and the arduous overhead that is imposed on space mission operations. These obstacles stem from a combination of factors—some are from 40 years of heritage and others from vehicle-unique constraints imposed by current vehicle designs.

Recommendation 3-22. Consider mission planning, quick response, and on-orbit operations as prime requirement drivers in the next series of vehicle designs. Specifically focus on an integrated program to develop the technologies needed for faster, more affordable operations.

Software

All aspects of the National Aerospace Initiative rely heavily on the use of software for successful applications. These include the three NAI major pillars: hypersonics, access to space, and space technology. One cannot imagine any aspect of this initiative that could be successfully completed without the use of modern-day computers and software. In fact, the software aspects often are one of the most costly items of the system life cycle. It is imperative that NAI reduce software costs and software errors if the initiative is to be successful.

The widespread, pervasive use of software throughout all programs related to the NAI is both a blessing and a burden to the program. The blessing is that there is much current work under way throughout the country, both in industry and academia, that can be used in the program. However, many of these programs must be focused specifically on NAI problems for NAI to be completely successful. This should not be difficult to make happen considering the high-level visibility of the NAI. Software evaluations are provided in Table 3-7.

Open Architectures

The criticality of open architectures was ranked “medium” because of the large body of work both in industry and in academia to solve these problems. Many of the presentations given to the committee listed these areas in the late 6.3 category, with TRLs of 6 or above.

Modularity

The probability of achieving the NAI goals of modularity is ranked “high.” This is because much work on plug-and-play interfaces has already been done and is continuing. This work is in the late stages of development by industry and was covered in many of the presentations to the

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

TABLE 3-6 Status of Technologies for Mission Operations

NAI-Defined Technology Areas

Committee Evaluations

 

 

Constituent Technology Ratings

Major Technology Area

Constituent Technology

Current Maturity Level (1-5)

Relative Impact on Major Tech Area (Negligible, Little, Moderate, Significant, Extreme)

Likelihood of Achieving in Time Frame (Current Funding Level) (Low, Medium, High)

Relative Criticality of Major Technology Area (Low, Medium, High)

Rapid mission planning—mission-unique constraints and analysis

Integrated mission planning tools

2

Moderate

Medium

High

Mission unique constraints and analysis

1

Significant

Medium

 

Rapid mission response

Range tracking

3

Moderate

High

Medium

 

Launch and landing flexibility

2

Significant

Medium

 

 

Command and control

3

Moderate

Medium

 

 

Air traffic management

4

Little

High

 

On-orbit operations

Autonomous GNC

3

Extreme

Medium

Medium

 

Proximity operations

4

Significant

High

 

 

Grapple, soft dock

2

Moderate

High

 

 

Fuel/consumable transfer

2

Little

Medium

 

 

ORU transfer

1

Little

Medium

 

 

Orbit-assembly-compatible structures

4

Significant

High

 

 

Rapid sensor initialization

3

Extreme

Medium

 

committee. This does not mean that some additional effort is not required to make these interfaces suitable for aerospace applications, but they are currently well developed generally speaking.

Engineering Design Software

Multiple engineering design software issues are very critical to the success of the NAI. The good news, however, is that there is a large body of work under way in all areas of engineering software. Several organizations presented their work to the committee. The areas presented covered combustion flow and analysis, simulation of aero control, stability and autopilot design, hypersonic inlet and nozzle design, thermal structural design, and propulsion system design. Most of these areas were being studied in the late 6.3 research category with moderate TRLs.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

TABLE 3-7 Status of Technologies for Software

NAI-Defined Technology Areas

Committee Evaluations

 

 

Constituent Technology Ratings

Major Technology Area

Constituent Technology

Current Maturity Level (1-5)

Relative Impact on Major Tech Area (Negligible, Little, Moderate, Significant, Extreme)

Likelihood of Achieving in Time Frame (Current Funding Level) (Low, Medium, High)

Relative Criticality of Major Technology Area (Low, Medium, High)

Open architectures

Secure wireless communications

3

N/A

High

Medium

Modularity

Plug-and-play interface

4

N/A

High

High

Engineering design software issues

Combustion flow analysis

3

Significant

Medium

Medium

 

Simulation of aero control, stability, and autopilot design

4

Significant

Medium

 

 

Hypersonic inlet/ nozzle design

4

Significant

Medium

 

 

Thermal structural testing

4

Significant

Medium

 

 

Propulsion system design

2

Significant

Low

 

Quick modification

 

3

N/A

Medium

Medium

Verification and validation

Parallel processing

2

Little

Low

High

 

Prediction of vehicle performance

2

Significant

Low

 

Autonomous flight control (transportable)

Vehicle to vehicle transportability

2

Moderate

Low

Medium

 

Secure, wireless communications

4

Little

Medium

 

 

Automatic decision-making process

2

Significant

Low

 

 

Autonomous software for integration and test process

2

Little

Low

 

Software engineering

Reliable, error-free codes

2

N/A

Low

High

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×
Quick Modification

The committee was presented a reasonable amount of work addressing quick software modification of aerospace equipment and facilities. The work reported in this area had technology readiness levels of 5 and above and was therefore regarded as “medium” in criticality.

Verification and Validation

The relative criticality of software validation and verification (V&V) is ranked “high” because of the potentially catastrophic consequences of software errors and because of the extraordinary expense necessary to accomplish the task. Software verification is cumbersome and labor intensive. Research should not only concentrate on unique aerospace V&V issues but should also capitalize on the latest techniques being generated by the civilian software industries.

Autonomous Flight Control

Transportable, autonomous flight control has a number of critical areas to be addressed: vehicle-to-vehicle transportability, secure wireless communications, automatic decision processes, and software for autonomous integration and test processes. These areas are all in the early stages of applied research (6.2) with low TRLs. In particular, basic research should emphasize the automatic decision-making process.

Software Engineering

The software engineering area requires considerable work to develop reliable methods for generating and checking code. This is a very important area of research, with much work being done throughout the country, both in industry and academia. However, the state of development in this area is still judged to be low, and there are many opportunities for major breakthroughs if NAI gives it sufficient attention.

TECHNOLOGY EMPHASIS IN THE NEXT 5 TO 7 YEARS

Many areas of research require attention under the umbrella of the National Aerospace Initiative. This section delineates those that might be brought to bear on near-term applications (e.g., the military space plane or the next-generation launcher.) This is not to say that long-term technologies presented in the following sections should be discontinued—in fact, all technology presented in both groups must be pursued in parallel and given appropriate weighting.

Technologies having the greatest probability of enhancing the near-term goals of NAI are advanced materials for use in propulsion and thermal protection systems, electrical/hydraulic power generation and management, software transportability, integrated structures, and error-free software generation and verification. Furthermore, the development of computational analysis tools and methodologies should be emphasized—especially when coupled to test analysis and ground test facilities.

Propulsion research work should focus on all technologies contributing to engine reusability and reliability, such as the development of new engine materials that will support combustion of both hydrocarbon and hydrogen fuels. Additionally, advances in health management technologies would pay dividends in safety, extend engine life, and lower maintenance burdens.

Additional work in the materials area should focus on the needs of high-strength, LOx-compatible materials, lightweight durable thermal protection materials, and structural materials useful in

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

new airframe designs. Durability should be the prime consideration in the development of these materials. The need for this work was emphasized in an earlier National Research Council report on hypersonics (NRC, 1998). Additional materials research must be focused on the need for reusable fuel tanks.

Both the DoD and NASA will benefit by leveraging work being developed by DOE for electrical power management and control. In this general area, advances in intelligent sensors and vehicle system thermal control should be sought by the NAI. Multiple programs being supported by the DoD and other agencies might be applicable.

Finally, the coupling of high-performance computing (numerical analysis) with emerging capabilities in ground test facilities (diagnostics, analysis tools, and methodologies) appears to show great promise in reducing the cost of vehicle development.

Finding 3-29. Milestones depicting the start of operational vehicle full-scale development have been established. The goal of NAI is to develop the underlying technologies to a level sufficient to support the decision milestones. The committee was not given a clear policy specifying the desired technology development thresholds at the milestones. Underlying technologies must be ready for full-scale engineering development at the appropriate decision points delineated in the NAI time-tables—2008, 2015, 2018, and 2020 (Rogacki, 2003; Sponable, 2003). Significant flight test activity must also be completed prior to these decision points. Considering the short time between now and the end of Phase I in 2008, it is unlikely that the underlying technologies can be developed in time to meet the Phase I goals depicted in Figure 3-1.

Finding 3-30. The United States has failed to sustain many X-vehicle programs through completion of their flight test phase. Consequently, many years of technology advances have been prematurely halted and remain unproven in flight.

Recommendation 3-23. DoD and NASA should develop time-phased, reusable, rocket-based flight demonstration programs to move these and other near-term, unproven technologies through flight test; specify and disseminate the technology readiness levels and specific exit criteria necessary to support the operational decision points; ensure that research is directed toward obtaining the specified data and that the demonstrations—both flight and ground—are structured to obtain the required information and data; concentrate on technologies that contribute to reusability; and fund multiple copies of each design to mitigate potential loss of the entire program if a single vehicle is lost.

Finding 3-31. Advances in lightweight, high-strength materials—especially TPS, energy storage, and engine LOx-compatible materials—can make significant contributions to mass fraction and reusability.

Recommendation 3-24. DoD and NASA should strongly support basic and applied materials research programs. They should focus materials research in support of reliable, reusable, long-life, low-weight TPS, energy storage, and rocket engine systems.

Finding 3-32. Rocket-based RLVs are technically feasible in the near future and may provide lowest life-cycle costs for responsive, high launch rate requirements.

Finding 3-33. Achieving aircraftlike operations will require higher margin, more robust vehicles, and more efficient ground operations than current launch systems, as well as automated flight planning operations.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

Recommendation 3-25. Adequate margin should be incorporated into all aspects of the next generation launch vehicle design. If necessary, payload capability should be sacrificed to achieve robust design goals.

Finding 3-34. Software is one of the most demanding and expensive aspects of any modern aerospace vehicle. Delays in software development ripple throughout the entire development process and significantly increase the overall cost of projects.

Recommendation 3-26. DoD and NASA should, through NAI, support a comprehensive research capability devoted to lowering the costs of aerospace software production. This research should concentrate on the safety-critical nature of aerospace software.

BUDGET SCENARIOS

The statement of task asks the committee to consider two budget scenarios for the development of NAI timelines: one that recognizes the current constrained Air Force budget, assuming no additional NAI funds are allocated, and one that meets the optimal NAI development timelines as developed by the committee. A rough order of magnitude estimate of the difference is also requested. The following paragraph addresses these requests only for the Air Force rocket-based access to space budgets.

Projected specific and related funding of AFRL space access efforts averages more than $100 million per year through FY 2009 without additional NAI-designated funds. This funding encompasses both upgrades to current expendable launch vehicles and technology for reusable systems. The NAI envisions a multiphase demonstration program with increasingly capable reusable vehicles available in 2009, 2015, and 2018. The development of these vehicles is not supported by current budgets. Additionally, while the first of these vehicles would essentially rely on current technology, the advances required for subsequent vehicles would require significant technology funding. The committee estimates that the first demonstration vehicle, the X-42, will cost $1 billion to $2 billion dollars and that subsequent phases will be increasingly expensive if they lead to an operational, high-rate, responsive launch system. In addition to the funding for the X-42, the committee believes it will be necessary to augment the space access technology budget by 100 to 200 percent to develop the requisite reusable systems capability for the Phase II and III systems.

LONG-TERM TECHNOLOGY AND PROGRAMS

Within the U.S. defense establishment, typical development periods from concept to initial operational capability (IOC) span 18 to 25 years (as they did for the C-17, F-22, FA-18 E/F, V-22, and others). Even the AIM-120 missile (AMRAAM), a relatively small system, took 12 years. This means that, with few exceptions, the concepts now emerging are close to what we can expect to be fielded—if and when the nation commits to improved spacelift capability and the improved effectiveness it provides to the LRS, ORS, and Space Control missions. Can these systems be developed faster and (consequently) cheaper? Yes. Will they be developed faster? Probably not without the impetus of a national crisis or some other cataclysmic precipitating event. Therefore, in the absence of unforeseen revolutionary technology advances, the fundamental difference between near- and far-term capabilities can be defined in terms of incremental advances in current research efforts. The results of this incremental process should not be underestimated. Slight changes in subsystem performance can drastically affect the vehicle configuration, operating characteristics, and consequently the life-cycle costs. A discussion of likely technology advancements follows.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

Engine performance will undergo modest improvements in the medium term. A little more Isp and thrust-to-weight ratio can be squeezed out of chemical engines by making the mixture ratios leaner and incorporating lighter weight materials. With higher sortie rates, IVHM should mature to the point of making genuine contributions to safety and lower recurring costs. Higher sortie rates will also tip the economic scales toward automating current labor-intensive mission planning cycles. Aircraftlike ground and flight operations will become reality if vehicles are consciously allocated and constructed with substantial margin. Improvements in TPS materials will most likely result in robust, precipitation-tolerant flight characteristics. Advanced TPS materials may also enable durable, sharp leading edges and the accompanying improvements in maneuverability and operational flexibility they bring. Large-scale, high-Mach turbines might advance to the point of viability for launching low or possibly intermediate size payloads. However, their utility for launching large payloads will be severely challenged considering the extraordinary development and operating costs of multistaged, multifueled, multiengined, extremely heavy, horizontal take-off vehicles. Finally, the most significant advance will likely be seen in the way software is produced. It is likely that the extensive, worldwide resources devoted to software generation can be leveraged to form a development environment capable of producing timely, error-free code.

The military space plane has a good chance of becoming the next revolutionary/transformational/ disruptive weapon system. Its development will only add to our already recognized dependency on space systems. Therefore, most space assets—including the MSP—will become valued targets in the eyes of our enemies. Concentrating on defensive maneuver, offensive engagement, and recovery from launch site attack will be necessary to counter the threat and capitalize fully on these emerging capabilities. The technology to produce an MSP currently exists or is very near term. Delaying the decision to field the MSP (while allowing other potentially useful technologies to mature) may or may not result in an overall lower cost system.

SUMMARY

The committee studied a variety of inputs and reference sources pertaining to the access-to-space pillar of the National Aerospace Initiative. Although NAI is chartered as a technology development effort, the pillar goals are expressed in terms of future operational system characteristics. This approach allows NAI to cast its net across a broad range of possible contributing technologies but necessitates the translation from system characteristics to technology objectives—a process open to some interpretation. Furthermore, without a clear understanding of the eventual system configuration, the specific system characteristics specified in the three-phase pillar could be difficult to justify and may result in expending resources on low-payoff technologies.

It is projected that the military space plane, as currently conceived, can perform the PGS, ORS, and Space Control missions in a very cost effective manner. The United States and several other countries currently possess the capability to develop the technology to produce this weapon system in the near term. However, over the last two decades, this country has lacked the conviction to demonstrate the underpinning technologies in flight. A flight demonstration is the next logical step to develop this transformational capability. It is yet to be seen if the emerging Air Force interest in these missions will produce tangible results.

Summarized in this chapter is the committee’s analysis and opinion of the NAI plan and the critical technologies that are required to enable the near- and long-term goals of the NAI. In general, the committee finds the NAI space access goals to be operationally relevant, technically feasible, and underfunded to meet the proposed schedule. This chapter has been prepared so that the NAI participants can compare these findings and recommendations with established plans and programs. The recommendations here are therefore intended to serve as input for evaluation.

Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
×

REFERENCES

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DoD (Department of Defense). 2000. Department of Defense Space Technology Guide, FY 2000-01. Available at http://www.defenselink.mil/nii/org/c3is/spacesys/STGMainbody.pdf. Accessed on January 6, 2004.


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Unpublished

Brockmeyer, J.W. 2003. Integrated High Payoff Rocket Propulsion Technologies (IHPRPT). Briefing by Jerry Brockmeyer to a fact-finding subgroup of the Committee on the National Aerospace Initiative. September 29.


Candler, G.V. 2003. Synthesizing Numerical Analysis Data to Design and Develop Hypersonic Engines and Airframes. Briefing by Graham Chandler, University of Minnesota, to the Committee on the National Aerospace Initiative. October 7.


DDR&E. 2002. National Aerospace Initiative. Access to Space Draft S&T Plan. Rosslyn, Va.: DDR&E. September.

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DeGeorge, D. 2003. Intersection of Air Force Propulsion S&T and the National Aerospace Initiative. Briefing by Drew DeGeorge, AFRL, to the Committee on the National Aerospace Initiative . September 3.


Holden, M.S. 2003. Requirements and Facilities for Ground Test of Full-Scale Scramjet Engines at Duplicated Flight Conditions from Mach 8 to 15. Briefing by Michael Holden, CUBRC, to the Committee on the National Aerospace Initiative. October 7.


Kastenholz, C. 2003. National Aerospace Initiative (NAI) Payloads. Briefing by Lt. Col. Chuck Kastenholz, AFRL, to the Committee on the National Aerospace Initiative. September 3.

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Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
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Suggested Citation:"3 Access to Space." National Research Council. 2004. Evaluation of the National Aerospace Initiative. Washington, DC: The National Academies Press. doi: 10.17226/10980.
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The National Aerospace Initiative (NAI) was conceived as a joint effort between the Department of Defense (DOD) and the National Aeronautics and Space Administration (NASA) to sustain the aerospace leadership of the United States through the acceleration of selected aerospace technologies: hypersonic flight, access to space, and space technologies. The Air Force became concerned about the NAI’s possible consequences on Air Force programs and budget if NAI program decisions differed from Air Force priorities. To examine this issue, it asked the NRC for an independent review of the NAI. This report presents the results of that assessment. It focuses on three questions asked by the Air Force: is NAI technically feasible in the time frame laid out; is it financially feasible over that period; and is it operationally relevant.

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