From Earth to Orbit: An Assessment of Transportation Options (1992)

Current U.S. Earth-to-orbit launch vehicles are based on 25-to 40-year-old technology. The infrastructure to support the vehicles is deteriorating, inefficient, highly specialized, and expensive to operate. Even the Shuttle launch complex, which is the most modern, was adapted from facilities built for the Apollo program.

Many U.S. launchers began as military designs. As a consequence, adaptation became the philosophy for U.S. space launchers. Because many vehicles were never intended for their present role, they often are marginal in meeting their mission requirements. This has produced a tendency to treat each vehicle/payload combination as a custom assembly that must be coaxed into orbit by optimizing and adjusting the available margins, even at the expense of schedule, flexibility, and reliability. Customized payloads, in turn, can easily tie up a launch pad for up to one-half a year, blocking any other vehicle from launching at that site.

With the 1970s decision to channel all launch requirements to the Space Shuttle, advances and improvements that might have been expected in expendable launch vehicle systems were deferred until after the decision was reversed in 1986.

These vehicle and infrastructure shortcomings were largely hidden as long as the United States had a near monopoly on space launch capability, but they have now emerged as severe detriments to the health of the U.S. space launch industry from the perspectives of global competitiveness and the ability to meet national needs. This can be seen in the commercial arena where U.S. launch system manufacturers are losing ground to international competitors, such as Arianespace. The Committee believes that a one-third to one-half reduction in launch and operations costs is required if the United States is to remain competitive in the launch vehicle market.¹ This is second in importance only to reliability. In a market where policy pricing is clearly at work, the U.S. government may have to rethink its policies. The

United States should look at successful overseas operations such as the French Ariane and former Soviet Union (FSU) programs to see what can be learned.

To ensure the future vitality of the U.S. space program, current facilities must remain functional. Therefore, rebuilding of our complete space launch system should be initiated. However, the nation needs a "clean-sheet" approach rather than being handicapped by trying to completely modify the existing infrastructure to accommodate new vehicles as well as current ones. Modification of existing facilities would not allow a completely new way of doing business that the Committee believes is essential for a new launch system.

The most effective way to initiate the "clean-sheet" approach is through the coordinated development of a new class of launch vehicles that are robust and reliable, along with new processing and launch facilities that are flexible and implement a launch philosophy based on integration, transfer, and launch (ITL),² payload encapsulation,³ and multiuse capability. The key to achieving these objectives is a change in the entire launch culture and philosophy.

Details of the desirable characteristics of a new launch vehicle and its supporting infrastructure, along with the launch philosophy are discussed in the following sections. Additional detail is provided in Appendix A.

Space launch vehicles have no utility without adequate terrestrial facilities and processes to enable and control a launch. As noted, the close historical tie between the launch vehicle and the infrastructure supporting it resulted in special-purpose, single-use facilities and systems dedicated to specific vehicles and not available to others. Current processes and payload preparation philosophies require a lengthy time on the launch pad, and in the event of damage or other problems on a pad, rapid recovery is not possible. At times, insurmountable difficulties arise if it is necessary to change from one payload to another, and the small number of available pads for each type of launch vehicle on both the East and West Coasts greatly restricts scheduling flexibility. In addition, most launch facilities are in a deteriorated condition, particularly on the East Coast, and pose the potential for safety problems and schedule slips.

Beneficial effects of a modern system should include a material improvement in the throughout capacity of the U.S. launch infrastructure and better utilization of the costly personnel associated with operation of launch sites. Some of these improvements can be made

to existing facilities, but the full benefit will not be achieved until these concepts are applied to a vehicle designed from the beginning to be operated in such an environment.

The United States should undertake extensive design of new East and West Coast launch facilities as soon as possible. Given that U.S. investments inevitably will be spread over many years because of budget pressures, it will be necessary to phase in a modern launch system. Preliminary designs and costing are required to demonstrate the feasibility of the various infrastructure proposals. Replacement of facilities can be implemented over time, and with initial capabilities limited to existing and near-term vehicles and flight rates, and with planned growth for future vehicles as requirements dictate. However, the new facilities must be flexible enough to deal with a range of payloads and launch vehicles, and must take full advantage of the dramatic gains in automation and electronics in recent decades.

The Committee does not expect immediate cost savings from the new methodology. It will require large, up-front investments for such items as launch pads, payload facilities, and modern vehicles. Many of the same checkouts will have to be performed, even though automation and better facilities may reduce personnel needs. The new processes will not apply to all systems immediately; the adjustment will be gradual. The Committee does, however, expect a substantial improvement in the potential launch rate, possibly a several-fold gain, as pads are freed up and as integration is simplified. In the Committee's opinion, no other space-related innovation would offer the country as much of a gain in capability as inexpensively and as quickly. The Committee believes that these changes are necessary and will benefit the competitiveness of the U.S. civil launch industry as well as help meet the needs of the National Aeronautics and Space Administration and the Department of Defense.

A long-term commitment to a new family of vehicles with many common components and a new, flexible support infrastructure is vital to the U.S. civil and military space program. Through improved design concepts and more effective launch operation procedures, it should be possible to obtain lower costs per pound of payload to low-Earth orbit, to provide competitive services to users, and to effectively meet national needs.

The key elements are reliability, flexibility, operability, robustness, and improved launch turnaround rates as discussed below.

Reliability: Reliability can be improved by incorporating active redundancy⁴ and by not operating at the limit of capabilities. Greater automation in manufacturing, ground

handling, and checkout can reduce the human errors that have contributed to many processing failures in the past. Higher reliability means not only enhanced safety but also lower costs to the user in the long term. In the commercial market, higher reliability can result in lower payload insurance costs.

Flexibility: The vehicle design should be simple, with standard payload interfaces. It should possess growth capability and have multipad launch capability. Presently, the United States cannot react expediently to national emergencies because of inflexible vehicles, processes, and facilities. Important aspects of flexibility are payload and vehicle compatibility, payload encapsulation, and design modularity.

• Payload and vehicle compatibility. The ability to switch payloads rapidly is essential. Under existing systems, each payload and vehicle combination is unique. Designs of most vehicles result in requiring dedication of a specific vehicle to a specific payload very early in the manufacturing cycle for the vehicle. This is especially true for the Titan IV. The lack of modularity of U.S. expendable launch vehicles (ELVs), with the exception of the Delta II and Atlas II with small strap-on solids, severely limits matching of payload performance needs with ELV capabilities.

• Payload encapsulation. Little attention is currently being paid to the need for the encapsulation of payloads to facilitate processing at the launch facility. This is not only a payload design consideration, but is also a design consideration for the launch vehicle and the infrastructure.

• Modularity. Efficient vehicle production is difficult in an environment of continuing vehicle design changes to match payload needs. A modular approach with standardized elements that could be selected to meet payload needs could yield greater production economies. Costs can be reduced through use of basic modules or elements in assembling vehicles with different performance capabilities.

Operability: Payload changeover constraints, a lack of performance margin, a need for considerable and multiple testing, extensive paper checkoff systems, and a lack of continued, automated health monitoring cause poor operability in current U.S. ELVs. These problems are further compounded by an obsolete launch infrastructure, resulting in an extended amount of time to reschedule flights when payload problems arise, which makes it difficult to schedule future launch opportunities. Being unable to guarantee launch opportunities is a serious detriment to commercial users.

Robustness: The early missiles that evolved into current medium and heavy launch vehicles were designed to optimize performance. Saving weight and maximizing performance have resulted in the current relatively fragile U.S. vehicles, which are susceptible to potential ground handling damage, weather-related launch delays, and unanticipated in-flight failures due to conditions that may only slightly exceed design specifications. Robustness can be built into a vehicle by designing for, and maintaining, excess performance margin. Designing for more extreme environments would reduce holds due to weather and also provide extra margin for unknowns or unsuspected design frailties.

Improved Launch Turnaround Rates: The current approach to installing and processing the payload while the ELV is on the launch pad severely constrains launch pad turnaround rates. An example of this problem may be found in the Titan IV launches from Vandenberg Air Force Base. Only two launches per year are normally planned due to the extended time required for on-pad integration and payload processing. Obviously, this is not an efficient method of launching space vehicles. To provide higher launch rates, both the vehicles and the launch complex should be designed for ITL (integration, transfer, and launch) operations, with off-line integration and processing of the ELV and the payload.

Customization of vehicles results in inefficient learning curves and generally higher system costs. A key element to meeting the above objectives is separation of the payload design from the vehicle design. This may cause some loss in performance because the vehicle is not customized for the payload, but the Committee believes that this cost would be relatively small and would be more than made up in the savings in efficiency, flexibility, and pad access.

Efficiencies in production are difficult to achieve when lack of a long-term commitment makes each year's production appear to be the final production run. Multiyear commitment for production has been shown to reduce costs, and other countries such as France, Japan, Germany, and Italy currently have multiyear funding for their space programs.⁵

As noted, it is essential that the new launch vehicle and the supporting infrastructure proceed in a coordinated fashion. The Committee realizes, however, that the new vehicles and associated launch facilities will not be available for several years. Meanwhile, the United States must deal with current vehicles and existing infrastructure. It is essential that the launch system approach described here be incorporated, to the extent practical, into existing launch facilities and the current family of launch vehicles.

The Committee believes that pad hold-down with engine shutdown capability and active redundancy⁶ are important characteristics that should be considered in the design of future launch vehicles. To implement them, the propulsion system must allow controlled shutdown on the pad and be throttleable.

Experience has shown that the initial few seconds after ignition tend to determine whether a rocket engine will or will not fail. For this reason, a rational way to prevent vehicle failure would be to hold the vehicle on the pad until all systems appear to be in order. In the event of a problem, a controlled shutdown on the pad can be executed, and vehicle and payload can possibly be saved. In this way, the vehicle reliability can be enhanced, although the mission will not be accomplished on time. Pad hold-down, generally for five seconds after ignition, makes it possible in the event of engine failure to shut down all engines and abort the mission on the pad.

Active redundancy requires throttleability and may require the use of an extra engine. Through active redundancy, the launch vehicle could complete its mission following failure of any one engine provided, of course, that the engine failure is benign, (i.e., does not destroy the vehicle). Such capability can be realized only if the remaining engines are capable of being throttled up to produce sufficient thrust to compensate for the lost contribution of the failed engine. The probability of a system failure, in this case meaning the failure of more than one engine, can be greatly diminished by the provision of active redundancy.

This increased reliability is at the expense of increased weight and the cost of the extra engine, but the enhanced reliability offers a reduction of the costs associated with launch failures. These include the cost of replacement of the launch vehicle and its payload, plus the lost utilization of the payload during the time required to reschedule the launch. It is difficult to reach general conclusions about the magnitudes of these costs, but it is probable that for many situations they are at least of the same general magnitude as the added engine costs.

The feasibility of active redundancy for liquid-fueled vehicles is strongly supported by a study⁷ which showed that a large fraction of liquid engine-system failures was noncatastrophic in the sense that the engine failure resulted in loss of thrust, but not in immediate destruction of the vehicle. For both ground and flight engines, the benign failure ratio (failures/engine flights) for liquid-oxygen/liquid-hydrogen propulsion systems is two percent, with no catastrophic failures. For other liquid systems (liquid-oxygen/hydrocarbons and hypergolics) the benign failure ratio is six-tenths of a percent and the catastrophic failure ratio is two-tenths of

a percent. While the number of both large and small solid rocket flight motor failures is small, they have all been catastrophic, rather than benign failures.⁸

Reliability should have top priority in the design of new systems, even at the expense of greater up-front costs and lower performance. The cost of failure in terms of time, money, and national prestige far outweighs the costs of built-in reliability. Improved reliability should be sought for all expendable launch vehicles (ELVs), many of which carry high-value cargo, as well as for manned vehicles.

The Committee believes that the advantages of enhanced reliability are significant and strongly recommends a careful evaluation of the advisability of including pad hold-down with engine shutdown capability and active redundancy in the first stage of the next generation of launch vehicles. Implementation in the upper stage is more problematic, but should be considered for specific systems where the costs and benefits can be quantified.

It should be noted that active redundancy is useful only for multiengine vehicles. For vehicles with a single engine and relatively small, low-cost payloads, other ways of improving reliability should be pursued, such as greater design margins, reduced performance requirements, more extensive system-level testing, and pad hold-down with engine shutdown capability at launch.