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10 Launch Vehicle Technology for Small Spacecraft BACKGROUND AND STATUS It is well recognizes! that a credible space launch capability is the cornerstone of the U.S. space program. This capability must provide the ability to deliver payloads in a reliable, safe, and flexible manner at low cost. For small spacecraft, the launch cost is a significant portion of the total life-cycle cost. Therefore, as the emphasis on smaller and less expensive missions increases, attention must be given to reducing the cost to deliver small systems to space. , ~ Today, the United States possesses a mixed fleet of launch vehicles that could be used to launch small spacecraft. These include expendable launch vehicles; a manned, partially reusable transportation system; and a newer class of small payload launch vehicles. With the exception of a few of the small payload launch vehicle concepts, most of the existing fleet of vehicles are either variants of military ballistic missiles upgraded into versions capable of space launch or use technologies that date back to the 1970s. All current launch vehicle systems are expensive to build and operate. Moreover, even though some of the new, small payload launch vehicles have potential for operational flexibility (i.e., the ability to change payloads in minimum time before launch), the majority of the launch vehicles lack this attribute. In addition, recent policies issued by DoD and the Administration to allow a limited use of excess ballistic missile assets for space launch vehicles and the more aggressive entry of foreign competition, have raised new, but mixed, reactions among U.S. producers of launch vehicles and launch services (DoD, 1993a; DoD, 1993b; DoD, 1993c). SMALL LAUNCH VEHICLES Several U.S. launch vehicles are listed in Table 10-1. These vehicles are well suited to launch small spacecraft (600 kilograms or less), but are in various states of design, development, and use. Specific information on availability and capabilities of the launch vehicles can be obtained from the companies involved. 75
76 Technology for Small Spacecraf! TABLE 10-l Representative U.S. Launch Vehicles COMPANY LAUNCH VEHICLE Orbital Sciences Corporation EER Systems E-Prime Aerospace Lockheed Missiles & Space Company CTA Launch Vehicle Services (formerly International Micro space Inc.) PacAstro American Rocket Company Pegasus, Taurus Conestoga Eagle LLV1, LLV2, LLV3 Orbex PA Aquilla Many of the vehicles have several variants. Although there are exceptions, most of these vehicle designs incorporate a combination of stages previously used for ballistic missiles, orbit insertion, or sounding rockets. They are heavily oriented to the use of solid rocket propulsion rather than the mix of solid and liquid propellant stages usually used for medium- and heavy-lift launch vehicles. Most of the small launch vehicles have been developed as innovative commercial ventures with some government investment. In some cases, the government has provided minimal support and then served as an "anchor customer," allocating a limited number of launches for the government payloads. in this sense, the government has played a key role in encouraging development of a commercial launch industry for the small launch vehicle market. Orbital Sciences Corporation is the only company that has actually launched payloads to orbit (using Pegasus and Taurus), and, at this writing, only Orbital Sciences Corporation and PacAstro have firm contracts for future launches. Lockheed Missiles and Space Company has scheduled the first launch of the LEV! for November 1994. American Rocket Company uses a hybricI-rocket approach with a solid fuel and liquid oxidizer and has successfully conducted several short-duration, static firing tests of a motor producing ~12,500 kilograms of thrust (Boyer, 1993~. Because of several attractive operational, safety, environmental, ant! cost benefits associated with hybrid rockets, there is interest within both DoD and NASA in carrying hybrid-motor technology to a point of maturity to assess its true potential. The American Rocket Company was one of the companies recently selected by DoD to receive Technology Reinvestment Project Funds over 24 months to further develop a Il2,500- kilogram thrust hybrid-rocket motor. The other companies involved in the Technology Reinvestment Project award includes Martin Marietta, United Technologies Corporation, U.S. Air Force Phillips Laboratory, U.S. Air Force/30th Space Wing, ant} U.S. Air Force/6595 Test and Evaluation Group. The 1994 NASA Appropriation Bill also contained language specifying continued investment in hybrid-rocket technology (U.S. Congress, 1993~.
Launch Vehicle Technology for Small Spa cecrafl There are many entries in the small launch vehicle market by international competitors, such as Australia's ALV; Israel's Shavit; China's Long March (ID); India's ASIA; Brazil's ELV; Italy's SMS; lapan's M-5 and Ill; Spain's Capricornio; and Russia's START-l, KOSMOS, and Surf (a vehicle built by the U.S./Russian company, Sea Launch Investors). Currently, only China and Russia are actively marketing their launch vehicles, but other countries are becoming more aggressive internationally. Today, the United States has a minimally demonstrated launch capability for spacecraft under 600 kilograms, with the promise of significant improvement. If many of the proposed U.S. vehicles become operational, then the capability and availability would significantly increase. However, it is still unclear whether the cost would decrease as a result of increased competition. In addition, the fate of domestic suppliers in the U.S. small spacecraft market is even more unclear when considering the number of potential international competitors. LOWERING COST OF LAUNCHING SMALL SPACECRAFT If there is to be an expancled small spacecraft market, there needs to be a lower- cost means of launching the spacecraft than exists today. A total launch cost of $5 million to $7 million was frequently cited by industry representatives and government officials during panel briefings as a threshold consiclered critical for an expanded market. This cost appears affordable for experimenters, innovators, and commercial and university users. However, none of the launch services listen! above is close to the target of $5 million to $7 million. Although spacecraft can be built for $2 to $5 million each, total launch costs, including the vehicle and flight operations, for existing small launch vehicles cost between $10 million and $25 million (Seitz, 1993ci. Use of Excess Missile Assets One approach uncler consideration by the Clinton Administration that will result in lowering launch costs for small payloads is to allow the use of excess missile assets. Although they are not technology issues, decisions regarding the authorization of the use of U.S. and Russian excess missile assets will have an impact on the nace of advanced - 1 ~ - r - technology development to reduce launch costs for small spacecraft. Some contractors contend that the goal of a total cost per launch of $5 million to $7 million could be achieved using excess missiles. The current U.S. Air Force/Martin Marietta multiservice launch system program using excess Minuteman assets should provide the basis for a reliable cost estimate. Policy recommended by DoD allows the general use of the existing missiles for suborbital requirements. Use for orbital requirements is highly restricted, and permission for use is controlled by DoD (DoD, i993a; DoD, 1993b; DoD 1993c). In spite of the potential to make launch more affordable for small payloads, there are some in the U.S. industry that believe such an action would have a negative impact on domestic commercial suppliers. The DoD-recommended policy is now under ooL)-recommenoeu 77
78 Technology for Small Spacecraft consideration by the National Security Council and the Office of Science and Technology Policy for recommendation to the President as a national policy. This study assumes that the goal of lowering the cost of space launches using systems developed specifically for that purpose will continue even if excess missile assets are used to support some portion of the requirements. Technology hnprovemen1;s Given the launch vehicle options discussed earlier, the problem is being able to provide launch services at a price that users are willing to pay. This appears to be in the range of $5 million to $7 million. With the exception of excess missile assets, today's market price appears to be about twice this desired range. Thus, a significant technology challenge exists to find ways to reach the clesired price. Even with a new design based on currently available technologies and those projected to be available in the next few years, the Pane! on Small Spacecraft Technology concludes that the likelihood of reaching this goal is very small. Also, little can be done from a technology perspective, to significantly reduce costs of existing small spacecraft launch vehicles except in operations as discussed in Chapter 2 of this report. . . Assuming a new launch vehicle approach, there are technologies that could be developed that can lower costs well below today's level. The following sections list technology recommendations to reduce the cost for future (~) expendable launch vehicles and (2) reusable launch vehicles. Technologies to Reduce the Cost of Future, Expendable Launch Vehicles ~e · · ~ - ~. Since propulsion and structures can account for 60 to 80 percent of the vehicle cost, it is not surprising to see attention for technology improvements focused in those areas. The majority of those addressing the pane! emphasized that propulsion was a key area for technology investment. It was suggested that future systems be designed for low cost, not high performance. This included component developments that use fewer parts and improved manufacturing processes, while still maintaining sufficient margins. In this regard, hybrid propulsion appears attractive from the view of safety and environmental compatibility. NASA and DoD have each been sponsoring several efforts to apply advanced manufacturing methods (e.g., precision investment casting, laser drilling, stereo lithography) to the manufacture of rocket components. The NASA Solid Propellant ~ This was also the finding in the 1987 Aeronautics and Space Engineering Board report Space Technology to Meet Future Needs and in its 1992 report From Earth to Orbit (NRC, 1987, 1992).
Launch Vehicle Technology for Small Spacecraft Integrity Program (S PIP) is funding industry programs to study manufacturing for reliability of nozzles, bond lines, and propellant. NASA and industry (notably McDonnell Douglas and TRW) have been jointly funding a low-cost, Tow-pressure propulsion approach that has the potential to lower production unit costs significantly. However, work is needed of sufficient scale to demonstrate the potential cost savings associated with advanced manufacturing techniques for a low-cost and highly reliable design. Except for solid rocket motors, launch vehicle structures have been fabricated, for the most part, from conventional aluminum materials. The higher strength composite materials have been avoided because of perceived higher cost. Advancer} manufacturing technologies could overcome this concern and perhaps result in reduced cost when compared with conventional metal structures. A large body of applicable launch vehicle technology has been developecl by several aircraft and spacecraft companies. For example, LTV, Boeing, Hughes Aircraft, and others have developer} advanced manufacturing techniques for structural components made from high-performance composite materials. Some government laboratories (Naval Research Laboratory and U.S. Air Force Phillips Laboratory) have developed composite structural components for spacecraft applications. These techniques may have application to launch vehicle structures. However, during this study the pane! identified no program for application of advanced composites to launch vehicle structures other than propellant tanks. For example, NASA has proposed the use of aTuminum-lithium alloys for the Space Shuttle's external tank. Proposals to use an aluminum-lithium alloy in launch vehicle structures have been made for some time, and tanks up to 45 inches in diameter have even been fabricated in technology programs. Another factor that tends to increase launch vehicle costs is the fact that the vehicles and their subsystems are manufactured from an extensive number of components that are inherently less reliable and more expensive than integrated components. Technologies to Enable Future Recoverable, Reusable Launch Vehicles The improvements in technology and operational approaches described earlier can drive costs down and deserve attention. However, the pane! believes that the desired range for launch cost ($5 million to $7 million) is not achievable with current and near- term systems. Even with newly designed expendable systems, the Tow costs desired will be difficult to attain. For cost reductions that are substantial, new systems must be considered that force a fundamental change in launch system design and operational culture. An approach, which long has been supported by space enthusiasts, is the fully reusable single-stage-to-orbit launch vehicle or some variant like a reusable two-stage-to- orbit launch vehicle. In the long term, the ability to decrease recurring costs via reuse and the introduction of appropriate aircraft industry-like operations to reduce infrastructure costs have a potential to offer a competitively low-cost launch service, especially for the small-payload portion of the market. It is not apparent that it would be economically feasible to develop a single-stage-to-orbit vehicle specifically to support the 79
80 Technology for Small Spacecraft small spacecraft market. However, the potential for a very low-cost launch system is sufficiently high that the enabling technology program should be supported. The technology required to support fully reusable single-stage-to-orbit or two- stage-to-orbit concepts is generally not very mature. Without the development of several enabling technologies, recoverable, single-stage-to-orbit launch vehicles are not possible. Some enabling technologies are . lightweight, high-temperature composite structures; aluminum-lithium alloy or composite cryogenic tankage; and thermal protection system materials with good moisture resistance; high specific impulse, low-weight, high thrust-to-weight tripropellant propulsion systems; flexible, lightweight guidance and control systems for launch and landing; on-board health-monitoring systems; ant} automated mission planning systems. Achievement of a reusable single-stage-to-orbit vehicle will require a substantial investment in these enabling technologies before a system development program can be initiated. However, because of the high potential payoff of a successful development, some level of technology support, especially in propulsion and materials, is advisable. The launch and recovery operational aspects were being addresses! in the McDonnell Douglas/BMDO Single-Stage-to-Orbit DC-X project. At the time of this report, announcements indicate the single-stage-to-orbit technology efforts will be continued under the auspices of NASA. ENVIRONMENTAL CONSIDERATIONS The preponderance of the launch vehicles being developed commercially to service the small payload market use existing solid propellant stages. Larger launch vehicles often have strap-on solic} propellant booster stages. At the same time, environmental regulations are increasing, and more ingredients, compounds, and substances have been restricted under various clean air acts. The exhaust product of most solid propellant rockets is hydrogen chIoricie, which is converted to hydrochloric acid in the presence of moisture and can prove toxic to ground vegetation and wildlife. Since the total quantity being emitted by current launches is small, this concern is not currently significant. But, if launch frequency increases, or regulations become more stringent, then it is possible that launch vehicles using today's varieties of solid propellant could be tightly controlled or stopped altogether in the future.
Launch Vehicle Technology for Small Spacecraft Technology programs are currently sponsored by the U.S. Air Force Phillips Laboratory with Thioko! and Aerojet to develop solic! propellants using scavengers2 or using solution-propellant processing to eliminate or minimize hydrogen chloride exhaust compounds. These propellants are referred to as clean propellants. Currently, ammonium nitrate-based clean propellants that contain no chlorine are available, but severe manufacturing problems exist, because the propellants are hygroscopic.3 Rocket-motor manufacturing must be in a controlled, low-humidity environment, and the motor system must be hermetically sealed through the entire storage life of the rocket motors. Ammonium dinitramide propellant eliminates the problem of hydrogen chloride from the combustion products. However, the ammonium dinitramide manufactured in the United States is extremely expensive and has not been manufactured on a large scale (Pak, 19931. The Office of Naomi Research has funded Thioko! and Chemical Systems Division of United Technologies Corporation to manufacture ammonium clinitramide ant} evaluate the product. Additionally, the solid propellant industry is doing small-scale, corporate independent research and development- sponsored work on ammonium nitrate and ammonium clinitramide propellants. The ammonium clinitramide technology is in the very early research phase. The hybrid-rocket system described earlier has the added advantage of producing environmentally acceptable propellant exhaust inherently. Unlike a conventional solid propellant, the hybrid fuel does not contain any ingredients that will form environmentally harmful exhaust products. These systems have the potential for providing a new, low-cost technology approach coupled with operational safety and environmental features. PRIORITIZED RECOMMENDATIONS In order to enhance technology for small spacecraft launch vehicles, the pane! makes the following recommendations. I. Hybrid rocket motors that simulate operational requirements, thrust level, and burn duration for small launch vehicles should be manufactured and tested to demonstrate readiness for application. 2. Although the Pane! on Small Spacecraft Technology believes it has identified several areas with potential for reducing small spacecraft launch vehicle costs, the pane! was not able to identify a technology program that would achieve the desired cost of $5 million to $7 million per launch. The panel, therefore, recommends that NASA conduct a study of proposed, new launch vehicles targeted for the small payload 81 2 A scavenger is a propellant additive that will continue with chlorine to reduce or eliminate hydrogen chloride. 3 "Hygroscopic" means readily taking up or retaining water.
82 Technology for Small Spacecraft market; with a goal of $5 million to $7 million per launch; to determine the cost benefits associated with the introduction of new technology, including unique concepts, new hardware designs, new materials, and manufacturing methods. This study should also include consideration of support for launch and mission operations. NASA should initiate advanced demonstration programs for promising concepts identified in the study, especially in propulsion technology. These demonstrations should be carried to the point that will allow decisions for system development to be made by either the government or commercial ventures. 3. The ongoing Solid Propellant Integrity Program should be supported with increased consideration toward those solid propulsion units used in commercial small launch vehicles. Such action will help the commercial sector maintain or improve reliability. 4. Development of advanced manufacturing methods directed toward producibility and cost reduction of small spacecraft launch vehicles should be continued. This should include potential application of advanced composites. 5. Scavenged and solution propellants are possible near-term solutions to potential environmental limitations of propellants and should be scaler! up and qualified for use. 6. A program to characterize the ammonium dinitramide-based clean propellants should be funded. If the results are positive, a program to develop a pilot plant to scale-up the manufacture of ammonium dinitramide shoulc! be funded. 7. NASA should initiate technology efforts in support of a reusable single- stage-to-orbit vehicle for small spacecraft where appropriate, to ensure the availability of the enabling technologies on a realistic time scale.