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Sunday, May 28, 2000
Citizens Advisory Council on National Space Policy February 16, 1994 In September of 1993 the Delta Clipper DC/X space ship successfully completed its mission: it was the first time a rocket ship has twice flown and twice landed vertically. This is a revision of a report to Congress prepared shortly after that flight. This report examines what was achieved and what we should do next. WHAT WAS ACHIEVED DC/X made a significant achievement, in no way belittled by asking precisely what it means. First, this DC/X flight demonstrated the technical feasibility of VTOL (Vertical Takeoff, Vertical Landing) rocket flight. Second: the second flight took place less than a month after the first VTOL flight. While a 24 day turnaround time would be disastrous to an airline, it is revolutionary to space flight operations and moves us toward the ultimate goal of turnaround times measured in hours, not days, weeks, or months. Future flights will demonstrate those dramatically shortened turnaround times. Third: the DC/X program showed that space programs need not take many years and many billions of dollars, and need not have enormous management and supervisory organizations; that we can build flying hardware in less than two years. Often repeated analyses show that for every year a program is stretched out the costs go up by a third compounded; the ability to complete programs in a short time is critical to bringing down the costs of space operations. WHAT WASN'T ACHIEVED Critics call the DC/X program a stunt. There is a sense in which they are right, but it is an unfair criticism: most of those who say DC/X is a stunt opposed the entire Single Stage to Orbit (SSTO) concept on the grounds that: 1. VTOL is impossible for rocket ships. 2. Short turnaround times are impossible. 3. You can't build flying hardware in under 5 years and for less than billions of dollars, because you must have a large design team to study all problems and devise solutions before you begin to make hardware. DC/X was therefore necessary as a demonstration that those particular objections were wrong, and now that they are out of the way we can get on with what we set out to do. Unfortunately, DC/X was not the SSX concept proposed by General Graham, Max Hunter, and myself to the National Space Council in February, 1989. SSX was intended to be a single stage to orbit (SSTO) X-program, not a Single Stage Rocket Technology (SSRT) capability demonstration. There are a number of reasons for the transformation from SSTO to SSRT; that discussion is omitted from this version of the paper. The important thing is that funds were limited. The program was assigned to the Strategic Defense Initiative Office (SDIO). For organizational reasons, SDIO thought that any ship they developed would have to meet some operational mission requirement; that it would be a prototype, not an X vehicle. That meant it needed a payload. The only way to assure a payload was to design for a number of contingencies. For single stage ships, the only way to add payload is to make the ship bigger; for every pound of payload you add, you must add 10 pounds to the gross liftoff weight. If you're trying to allow for contingencies, the ship design weights go up very fast. Worse than that, it soon becomes clear that you'll need new engines. Engine development programs are as expensive as spacecraft development programs. There wasn't anywhere near enough money to try for an experimental space ship and simultaneously to develop new engines for it. The requirement for a payload eliminated the original SSX; and since a full sized ship with payload wasn't possible, the program office opted for a demonstration model. The result was a shift from SSTO -- a Single Stage to Orbit ship -- to SSRT, Single Stage Rocket Technology. What was an X ship became a technology study, thus giving critics of DC/X a reason to call the entire program a stunt. Neverthe less, DC/X accomplished a great deal. WHAT WILL BE ACHIEVED Flight tests of DC/X must continue. There are many aspects of rocket flight dynamics that we now know only from simulations; in particular rotation of the vehicle along the axis of flight needs to be tested. There are plans to demonstrate landing with one engine out. DC/X may well become the first space ship to fly twice in one day. This will be an important milestone. WHERE DO WE GO FROM HERE? It wasn't a stunt, because it demonstrated that there are no real barriers to building a true SSX-1: a space ship experimental that will go to orbit. The key here is to understand the nature of X programs. X Programs From 1943 to roughly 1970 the United States conducted a highly successful series of programs designed to develop significant new aerospace technologies. They started with the X-1, the first airplane to fly faster than sound, and went on from there. For years we repeatedly built X planes which flew higher and faster than anything in the world; which found new technologies of fuel efficiency, aircraft performance, maneuverability and control dynamics. The payoffs were great: during that era and into the decade that followed the effective termination of the X airplane programs, US aerospace industry dominated the world market. Other governments have directly subsidized airframe manufacturers, making it very difficult for US firms to compete on price alone, and our airframe companies have lost market share, not only in foreign markets but in domestic as well. Thirty years ago it would have been considered silly for any free world airline to buy a passenger airplane from any but a US airframe company. There are many reasons for US loss of market share, but one of the main ones is the loss of the continual stream of new aerospace technology that once flowed from the X programs. The important thing to remember about X programs is that they were: small with tight management; willing to take risks for high payoff; relatively low cost; short term. They were not jobs programs, and they were not prototype programs. X planes typically had no payload: the X-1 carried Major Yeager and a short length of broomstick to enable him to latch the cabin door. X programs were designed to stretch the technology envelopes: show the way to new capabilities with existing or easy modifications of existing hardware; show what new developments were needed to reach the next technological plateau. Revival of the X programs would be one of the most significant investments in the future that the United States could make. X programs are not jobs programs, but they created jobs. SSX Now that DC/X has successfully flown it's time to think about what to do next. The DC/X Program Office under Colonel Pete Worden has proposed a new X ship. The DC/X was a 1/3 scale model of an orbiting ship. The proposal is for a second scale model approximately twice as large (and thus about twice as capable) as the DC/X. It would in effect be a sub-orbital reusable sounding rocket, single stage to 100,000 feet but not single stage to orbit. Advantages of such a program: it can certainly be done in a couple of years, at relatively low costs. It demonstrates technology, and gives engineering experience in building and flying single stage vehicles; and it gives experience in rapid turnaround of rocket ships. It can continue to develop flight data for vehicles of this type, and probably can be made to fly fast enough to generate date on thermal protection requirements. It does not require a new engine, and gives the working teams something useful to do while engine developments continue. It can be phased in with NASA efforts. Disadvantages: it has no great appeal to anyone. It doesn't do anything we can't already do, and there's no clear mission for it. X projects don't need missions, but X projects are designed to stretch the envelope; are bold steps toward new capabilities. This does not accomplish the classic mission of an X program, because it is not bold enough. It is difficult to see the X objective of this program, and I don't think it can be sold as an X project, because it doesn't take us far enough on a new technological plateau. The real disadvantage is that incremental approaches like this give our foreign competitors nearly as much information as they give us. The Japanese are not yet trying for SSTO, but with a second development like this one, it would be absurdly simple for them to use what we have learned to build their own. The French may not at this time be looking for a replacement for Ariane, but they can use spread sheets as easily as we can. In fact, both may have already been stimulated by the DC/X publicity. Long lead times to reliable space access take away much of the commercial and military advantages of developing that technology. If our goal is to recapture the market in space launch that we have lost to Ariane and others, then we need rapid development of new space capabilities. WHAT SHOULD WE DO? The Council recommends that DOD continue testing the DC/X, but immediately begin a follow-on SSX-1 with at least eight engines. It should be built to use existing RL-10 engines with minimum modification for altitude compensation. Major Design Criteria It must have the capability to survive loss of an engine on takeoff, and demonstration of this capability should be a major flight test goal. It must be designed for extremely rapid turnaround times. No compromises should be made in structural strength but the design size should be large enough to allow the fully fueled vehicle to approach or achieve orbit with sufficient fuel reserve to return. It must have thermal protection and retrofire and reentry capability. Achieving orbit will be unlikely, but it must not be made impossible by design. This is not an 'orbit or bust' program, but going to orbit with or without payload should be the goal. It must be designed to allow retrofit of the RL-35 engines now under development. We understand that orbit capability is highly unlikely with existing RL-10 engines; the goal is a design that would achieve orbit with better engines. We conclude that a properly designed ship retrofitted with the RL-35 engines should achieve orbit. The design should take into account that this ship can fly incremental missions and modifications can be made after well designed flight test programs. Early flights can incorporate safety equipment and structural reinforcements. Experience will indicate possible modifications to increase capability. Payload considerations should play no part in the ship design. This is a flight test X vehicle, not a prototype for a new operational ship. Classic X programs were not dependent on a single flight vehicle; having only one flight article inhibits tests that really stretch the limits of technological capability. We understand that political and budgetary factors may limit this program to one vehicle, and it may be unrealistic to ask for more; but we want to be on record as saying that you get far more than twice the benefit from having more than one flight test vehicle. Engine Development If it is decided that we must seriously accelerate the program for international competitive reasons, then extra resources must be found to develop new engines specifically tailored (thrust level, chamber pressures, large numbers of reuse, throttleability, altitude compensation) for SSTO vehicles. These should be designed for incorporation into SSX-1. Note that this engine development program would be a supplement to SSX-1 and conducted in parallel. New engines are necessary for an operational SSTO ship; an X program can be done without that expense. New engine development is a prudent investment in the future. COMPETITION IS HEALTHY, AND EXPERIENCE IS VITAL We are informed that NASA is, commendably, now interested in restarting the X programs, and in particular has become interested in Single Stage to Orbit capabilities. We applaud this. However, we believe that it is vital that the USAF/DOD and NASA programs be kept separate. There are many reasons for this. Briefly: although the original X programs had joint USAF/NACA management, in the past decade mixed management programs have not been highly successful. The organizational structures and mind sets of the two groups are entirely different, and attempts to merge them are unlikely to produce the kind of small, bold management teams that successful X programs require. This nation has lost the institutional capability of doing X programs. We must regain that capability; and the more independent X efforts there are, the better chance we will have to restore our dominance of aerospace. Some X programs will fail because of bad management. Some will succeed and in doing so will teach the proper management techniques and mind sets. Relearning how to do X programs is itself an experiment. Fortunately, what we have done we can aspire to. Two X programs will cost less per year than a single shuttle flight, and have much greater payoff. There must be many new X programs. They must not be merged. RECOMMENDATIONS AND CONCLUSION We recommend that the successful restart of flight testing of DC/X be used as a springboard to generate bi-partisan support for renewal of the X programs in general, and to start a DC/X follow-on meeting the design criteria given above. It should have the ultimate goal of reaching orbit, re-entering, returning to Earth, and flying again to orbit in the shortest possible time. The need for this program goes far beyond partisan politics. We recommend that this follow-on remain within USAF or DOD and not be merged with any existing or new NASA program. This should be an independent DOD effort. If legalistic reasons prevent an office within BMDO from developing an orbital capability, the program should be moved to another office within DOD. In a separate report we will give detailed and specific recommendations for NASA to consider in designing X programs. In particular, we believe that it is vital to the national interests of the United States that NASA continue to develop new space technologies, particularly rocket engine technologies; and that NASA phase out of being a operating agency and back to its historic and highly successful role in technology development. NASA should, indeed must, begin new X programs, and one of these should be an SSX (Stage to Orbit, Experimental) ship; that ship ought to be independent in conception and design from the DC/X follow-on. NASA engine development programs ought to be informed by requirements for SSTO engine technologies, and at least one such program should be dedicated to developing an engine specifically designed for a multi-engine SSTO vehicle with engine-out capability. While NASA can and should develop engines based on radical new technologies, the United States critically needs at least one SSTO engine based on existing technology and designed under conservative principles. We have previously discussed the military importance of routine access to the space environment. We note that SSTO in the hands of a potential enemy would be a threat to US access to space. Slow development of SSTO technology gives both military and commercial opponents opportunities to surpass the United States in space operations. We conclude that the United States currently has the opportunity to regain our historic dominance of the world aerospace market and that this can be done at costs comparable to or lower than what we are spending now. The key to all this is revival of the X programs in general, and in properly designed SSTO programs in particular. Jerry E. Pournelle, Ph.D. Chairman, Citizens Advisory Council on National Space Policy
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