Transatmospheric Vehicle

On April 6, 1987 the Greater New York Section of AIAA in conjunction with the New York Society of Security Analysts and the Space Commerce Roundtable Foundation sponsored a meeting at the Wings Club in New York City. The subject was the air- breathing hypersonic aircraft/space launch vehicle now under development. This projected experimental aircraft is officially designated the X-30. However, it has, up to now at least, been more commonly known as the Trans-Atmospheric Vehicle (TAV) or the National Aerospace Plane (NASP). It has also been referred to as the "Orient Express," thanks to President Reagan's use of that phrase in his 1986 State of the Union message. Likewise, one can find scattered references to it as "Cooper Canyon," the name of a now-declassified "black" USAF project.

By whatever name called, the project has become a major focus of aerospace research. Some $300 million has been earmarked for that purpose in the current fiscal year budget. Even more importantly, if the vehicle lives up to the expectations of its proponents it has the potential to revolutionize both long distance transportation on Earth and the launching of payloads into low-Earth orbit (LEO).

The speaker was Robert M. Williams, who is NASP program director at the Defense Advanced Project Agency (DARPA). Williams began his presentation by describing the X-30 as an experimental aircraft similar to the X-15. (Noting the numerical coincidence, he joked that it would be "twice as good.") He also referred to the fact that the TAV had recently received at great deal of attention, describing this as a "good news-bad news" situation. As previously noted, President Reagan referred to it in his State of the Union message. On that occasion the President emphasized the role of the system for intercontinental air transportation on Earth. Later Mr. Reagan presented a model of the X-30 to teacher-in-space runner up Judy Garcia. This time, as might be expected, he stressed its potential for launching payloads into orbit. In either case, what is in contemplation is an air-breathing vehicle capable of taking off from an airport runway and accelerating to speed of approximately twenty five times the speed of sound (Mach 25).

Williams then went on to describe DARPA. The basic function of this agency is to look out into the future. More particularly, its job is to try to predict where technology, and especially synergy in technology can take us.

He then commented that the managerial challenge in connection with the TAV, involving as it does a joint program between five agencies, is probably equal to the technical challenge. The program is headed by an inter-agency group organized pursuant to a memorandum of understanding. It is overseen by a steering group whose members include the technology heads of the armed services the heads of DARPA and NASA's Office of Aerospace Technology and General Abrahamson of the Strategic Defense Initiative Office (SDIO).

Williams himself runs the program management office that reports periodically to the steering committee. ("As infrequently as possible," according to Williams.) Under Williams are three deputies, a NASA official, an Air Force colonel and a Navy Captain. They are responsible for giving general direction top the program. Below them is a joint program office headquarters at Wright-Paterson Air Force Base. This organization consists of about sixty people who implement the program and manage its overall execution from day to day. Beyond that the "tentacles" (as Williams put it) extend to NASA, Air Force, Navy and university centers of research throughout the United States. There are probably about five hundred researchers currently participating in the program, if those employed by contractors are included, and this number is growing rapidly.

As of the time of Williams' presentation, major aerospace companies competing for selection as prime contractor for the airframe portion of the X-30 program included McDonnell-Douglas (with whom Martin Marietta is teamed), Boeing, Rockwell, Lockheed and General Dynamics. Competitors for prime contractor on the engine side included General Electric, Pratt & Whitney and United Technologies. Rocketdyne was also what Williams described as a "dark horse candidate," in the power plant competition having entered the program using their own resources. Williams implied the contest for both airframe and engine prime contractor was intense and close. He described it as "a horse race of the first magnitude, trying to get the best ideas of this country ***" as to what is the best way to move ahead with the TAV.

There are, according to Williams, five key technologies associated with the development of a TAV: Revolutionary, unrestricted air-breathing propulsion; next generation supercomputer aerodynamics structural and propulsion system design; high strength, high temperature lightweight and fully reuseable materials; high efficiency energy management; and intelligent control systems. All of these, however, have implications far beyond the TAV itself. The proposed aerospace plane has in fact become a driver moving American aviation technology forward along a broad front. The most important area is propulsion, with aerodynamics and materials not far behind.

Turning first to propulsion, Williams displayed a graph which plotted altitude against Mach numbers. The message behind this chart, he said, was that "the faster you go, the fewer your options for propulsion." Indeed, for speeds above Mach 6 the only practical air-breathing propulsion system is the so-called "scramjet." It is this propulsion concept, therefore, that will be used for the NASP. Several systems are being looked at to accelerate the vehicle to the speeds necessary for the scramjet to operate. These include hydrogen turbojets, which have a very high ISP. Since all of these involve conventional technology, however, Williams did not included a discussion of them in his presentation, although he did mention them in the question period which followed.

A scramjet is a derivative of a conventional ramjet (described by Williams as "nothing but a tube flying through the air"). A ramjet flies so fast that the air in the tube is compressed, raising the pressure so that "if you squirt in some hydrogen" it will burn and provide thrust. The distinction between a ramjet and a scramjet is that in the former combustion occurs at subsonic speed. In a scramjet the internal geometry of the engine is changed to produce a phenomenon known as "swallowing the shock." This causes the air to flow through the engine at close to the speed of the airplane. For example, at speeds of Mach 25 in the outer reaches of the atmosphere (the speeds and altitudes at which it is hoped the TAV will be able to operate) the flow through the engine approaches speeds of 25,000 feet per second. (By way of comparison, the muzzle velocity of the 30-06 rifle cartridge, standard for the U.S. Army's in both World Wars, was on the order of about one-tenth this figure-2,700 feet per second.) At such speeds the only thing that will burn is gaseous hydrogen.

If it can be successfully developed, such a propulsion system, has, in addition to other applications, tremendous implications for putting payloads into Earth orbit. Williams described rocket propulsion as a system that requires us to "haul air through the air to get out there." By breathing its own air from the atmosphere the NASP will eliminate the need to carry oxidizer aboard the launch vehicle. Moreover, hydrogen burns very efficiently with air. Specifically, burning a pound of hydrogen with air will produce about 40 million foot-pounds of energy, vs. about 4 million foot-pounds for liquid oxygen. (Approximately 11 million foot-pounds of energy are needed to put one pound of payload into orbit.) For a vehicle launching Space Shuttle size payloads this would, he asserted, enable us to dispense with the solid rocket boosters and external tank. That in turn will permit compressing the takeoff weight of the vehicle by a very large factor.

During the question period that followed his formal presentation Williams stated that even assuming vehicle turnaround times of a few days to a week (and much shorter times may be possible) the impact on costs would (in his words) "blow your mind." He was understandably unwilling to commit himself to specific numbers. Nevertheless he indicated that if the NASP program was able to meet its technological goals launch costs on the order of $100/lb to LEO were a definite possibility. Such cost reduction would in turn have major effects space entrepreneurship and space industrialization.

While subsonic combustion ramjets involve very well known technology, supersonic combustion ramjets are another matter. The upper limits of a scramjet's speed are not really known yet. During the question period which followed his talk Williams was asked what he foresaw as the upper speed limit of an aerospace plane. He responded that calculations been made for speeds in excess of Mach 30. Williams implied that no fundamental limitations have as yet been encountered with respect to either propulsion or chemistry. The limiting factor, he half-humorously suggested, may be the point at which the airplane melts. The goal of the NASP program is to attain speeds with air-breathing propulsion which will enable the vehicle to achieve orbit. This is approximately Mach 25. Williams suggested, however, that the program would still be a success even if only lesser speeds could be attained. In particular, he noted that some form of rocket propulsion would be required for on-orbit and de-orbit manuevers in any case.

One part of the X-15 aircraft program, as originally planned, involved a so-called hypersonic research engine. The system, which would have been housed in a module sitting below the airplane, was in fact an actively cooled, gaseous hydrogen scramjet engine. Theoretically this engine could have attained speeds of Mach 7, faster than the airplane itself could handle. As a result the system was never flown. Combined with this was the decision to use rockets to go into space. As a result air- breathing propulsion technology languished. However, the legacy of the hypersonic research engine and other, similar, efforts has now been picked up by the NASP program.

Since the inlet ducts of a scramjet engine will be subjected to temperatures that will melt any known material, an active cooling system is necessary. While, of course, temperatures are enormously greater, the principle involved is essentially the same as that demonstrated in grade school science experiments where a flame is applied to paper containers filled with water. However, instead of water liquid hydrogen (as one option) is circulated around the engine to absorb the heat. Williams conceded that cooling systems for scramjet engines involved "exotic technology," but contended that the technology "appears to be doable to us at this point in time."

A related problem with the design of the NASP's propulsion system is calculating the flow of air through the "guts" (as Williams put it) of a scramjet engine. The NASP project has been able to make use of computational methods that are part of the legacy of the X-15 hypersonic engine program. However, to perform the calculations with the accuracy needed requires supercomputers that have only become available within the last five years.

Williams described a spaceplane as "the most integrated system ever to be attempted in aeronautics. In fact, we do not know were the engine starts and the airframe ends." For example, the "bottom" of the airplane will function as a compressor by generating the shock that compresses the flow going into the engine module and the "back end" of the airplane will form the nozzle of the engine. The engine will, in effect, be simply a combustor. This situation, he indicated has created "all kinds of turf battles" between the contractors working on the airframe and those involved with the engine. Each group asserts that it should be responsible for designing the bottom of the airplane. The design of the TAV is, Williams stated, "replete with these kinds of conflicts." It presents "a management challenge of the first order (just) to figure out who owns what." Similarly, the program has placed the space and aircraft divisions of the various aerospace contractors involved on a collision course because both have to cooperate in the design of the vehicle. This, Williams asserted, was something easier said than done. Indeed, he expressed the belief that the NASP will cause a fundamental change in the nature of aerospace institutions in this country.

Another major factor in the design of the TAV is computational fluid dynamics. Not only must pressure contours be calculated to a high degree of accuracy, but (as Williams put it) we must also "make sure that our calculations have some bearing on the real world." Twelve Cray supercomputers are being used in connection with the program at the present time, including the Numerical Aerodynamics Simulation Facility at NASA Ames.

An additional aspect of the aerodynamics of the NASP vehicle is energy management. Drag produced friction on the surface of an aircraft generates heat. At lower speeds this simply can be thrown away by radiating it into the atmosphere. Above Mach 3, however, it becomes advantageous to recapture the heat and use it. Specifically, it is contemplated that the TAV will use some of this drag-generated heat to preheat its hydrogen fuel before the fuel is introduced into the engine. This will result in increased thrust.

In addition to propulsion and aerodynamics, a major consideration in NASP development is materials technology. That is because one of the program's goals is to develop a truly reusable space launch system. Williams described this as meaning that "you can land that vehicle, roll it down the runway, roll it into a hanger, change out your payload, refuel and go again. No more tiles, no more refurbishing." Williams asserted that this "goal drives a whole slew of technologies, but the most important one it drives is reuseable metallic materials." According to Williams, "this program is moving high temperature, lightweight and reusable materials forward at a very rapid pace," with implications that go far beyond NASP. These materials will be the successors to the titanium alloys in use in the aerospace industry today.

Williams displayed a chart which plotted strength-to-weight ratios of various substances against temperature. Noting that all present state-of-the-art materials tend to fall off rather rapidly as temperature increases, he stated that the NASP program hopes to develop substances which will have at least twice the strength-to-weight ratio and increased temperature capabilities compared to present titanium-type materials. Among the techniques being investigated are rapid solidification and powdered metallurgy. Also under consideration are composite metallic materials produced from graphite or silicon carbide fibers using powdered metal as a matrix.

"Another exciting material," according to Williams is what he called "the next generation of carbon-carbon." Noting that carbon-carbon is used today on the Space Shuttle for thermal protection, he asserted that it was also possible to use it for structural components, and stated that this "next generation" would be able to accommodate high structural loads. In this connection he displayed a picture of an experimental turbine, constructed entirely out of carbon-carbon, that has been spun at speeds of 40,000 RPM. This turbine is was not intended as part of the spaceplane, but it may be used in the next generation cruise missile. However, Williams cautioned that a key problem was preventing the carbon from combining with oxygen and forming carbon-dioxide. When that occurs, as Williams noted, "it all goes up in smoke." He asserted, however, that new coating technologies were being developed to handle this difficulty.

A fourth area of interest to the TAV program is hydrogen management, the efficient use of hydrogen. The X-30 will use hydrogen for many purposes in addition, of course, to propulsion. Hydrogen will be employed for cooling the nose, engine, equipment bay and the crew itself. Indeed, Williams noted that it has been humorously suggested that the best place to locate the crew compartment would be inside the hydrogen tank. Other contemplated uses of hydrogen on board the NASP include fuel cells for power and thrusters to stabilize the vehicle when it is outside of the atmosphere. (In the course of the question period Williams indicated that an advanced version of the thrusters used on the current STS is under consideration for this purpose.)

The NASP program has already given birth to one major advance in connection with the former, which has now been spun off and is proceeding independently. This is a new type fuel cell which is constructed entirely from ceramics and is far more compact than any fuel cell system presently in use. This system can convert hydrogen and oxygen to electricity with efficiency of approximately 75%, which is almost twice as efficient as today's automobile engines. According to Williams, this new type fuel cell could, in and of itself, result in a whole new generation of electric powered vehicles.

Additional benefits of hydrogen-fueled aircraft are independence from foreign oil supplies. Williams noted that while the general public has in recent years tended to forget about this problem the Department of Defense cannot afford so to do, and is actively studying alternatives to hydrocarbons as fuel sources. Hydrogen, he noted, can be obtained from a variety of sources, including natural gas, water and biomass. One proposal being put forth is to use genetically engineered bacteria to produce hydrogen. Hydrogen has the additional advantage of being non-polluting. Although it may produce some nitrous oxides at very high temperatures, its primary end product is water vapor. DARPA also believes that hydrogen is as safe as, if not safer than, conventional hydrocarbon fuels. Williams admitted however, that any proposal to use hydrogen immediately runs afoul of what he characterized as "Hindenberg syndrome."

The final major technology involved in the NASP program is advanced controls and avionics. The primary area of focus here is on active flight controls and orbital controls. However, according to Williams by creating such a focus for research and development the X-30 is driving American industry towards finding new applications in such areas as high speed integrated circuits, parallel processing computers and fiber optics.

Williams then proceeded to discuss the utility of an aerospace plane. He began by paying due deference to Mark Twain's observation that prophecy is a very risky business especially when it concerns the future, although he did not refer to it directly. None the less, he asserted that while the X-30 was an experimental vehicle it would provide enabling technology for a whole range of applications.

The follow-on technology to the X-30 will probably take several forms. Williams first discussed potential military uses. He stated that the TAV would have such capabilites as launch and recall from orbit on demand, unpredictable flight paths resulting from the ability to perform plane change manuevers in the upper reaches of the Earth's atmosphere, on-orbit loiter, and the ability to and use multiple launch and recovery sites. Williams suggested there were also military applications for X-30 derived vehicles designed to cruise within the atmosphere.

Williams turned next to NASP-technology-based civilian launch vehicles. In the question period that followed his talk Williams was asked if he personally had any ranking of priorities in the post X-30 development of the TAV as between military vehicle, civilian space launch system and hypersonic airliner. Williams responded that the top priority, beyond any question, was the space launch system. The reason for this was the potential an air-breathing launch system could have on launch- cost reduction. For the same reason, as Williams stated during his formal presentation, the number one priority within the launch vehicle segment of the NASP program was cost reduction, especially keeping life cycle costs down. As previously indicated, particular areas of focus are reusability, utilization (rapid turn around), elimination of large scale ground infrastructure and logistics "tail" and greater efficiency resulting from the use of air-breathing propulsion. The hope, as he expressed it, is to transfer space launches from "spectaculars" to routine operations. If this connection Williams suggested that it might be possible to take off from New York City's Kennedy Airport and go directly into orbit.

However, there will be differences between the NASP and an ordinary airplane. For example, during the question period someone asked if landing the TAV like a conventional aircraft would provide sufficient cool-down time for the vehicle's skin, and if not, would the need for special handling requirements on the ground impact on the ability of the aerospace plane to make a quick turnaround. Williams indicated that the answer to this question was not yet known, and would depend on heat dissipation capability. The program's goal is to avoid anything that would significantly impact turnaround time. In particular, an attempt will be made to avoid materials such as the tiles used on the present STS which have a resident heat load. He commented though that "I suspect that you're going to have to handle a fairly hot vehicle."

The launch vehicle segment of the TAV program has been fortunate to have received the support of several important groups. These include the National Commission on Space (NCOS), which recommended that this project receive the highest level national priority.

Williams also noted that development of a NASP-related launch vehicle has become important because international competition in this arena is about to intensify. He specifically mentioned the French HERMES (rocket powered), the British HOTOL (air-breathing) and West German SANGER-II (air-breathing booster, rocket powered orbiter combination) systems. He also stated that the Japanese under the auspices of their Ministry of Technology and Mitsubishi Heavy Industries were considering the possibility of an air-breathing launch system. What was particularly notable about the last three projects, according to Williams, was that they were being put forward by countries that he described as "have nots" in the space launch area. He suggested that it was significant that countries which do not have a large investment in rocket launch infrastructure are considering the air-breathing propulsion option.

(As an aside, there was little specific mention of the TAV at the May, 1987 Princeton Conference on Space Manufacturing, which the writer attended. However, there seemed to be a widespread feeling that truly efficient launch systems must avoid the necessity of carrying all of the energy needed to get into orbit aboard the vehicle. Air-breathing systems obviously lend themselves to this objective, at least to some extent.)

In response to a question as to the amount of payload that the TAV would be able to carry into orbit, Williams stated that since the X-30 was an experimental research vehicle the only thing planned to be carried into orbit by it was an instrumentation package. It was not intended, for example to supply payload to the space station. The payload capability of the follow on launch vehicle has not yet been defined. He noted, though that extensive studies on this subject are currently underway, including the National Space Architecture Study. The current outlook of the latter study, Williams indicated, is that the country should adopt an unmanned heavy lift launch vehicle for putting very heavy payloads into space and a manned system for situations where flexibility or recallability was desired. The latter is expected by Williams to be a derivative of the NASP.

Coming finally to the "Orient Express" part of the NASP program, Williams noted that the White House's Office of Science and Technology Policy had considered the direction that the nation should be taking with respect to its R & D goals. The study looked in particular at the area of high speed transportation. The White House staff endorsed pursuit of research in the area of trans-atmospherics and hypersonic propulsion systems.

Williams also commented that the Orient Express concept had been taken out of context. He reiterated that the X-30 will be an experimental vehicle and will not itself be a hypersonic transport. However, it will develop the technology applicable to an Orient Express. He also noted that, while a hypersonic transport was a major focus of the NASP program, it was only one of many focuses.

Williams described the Orient Express as a vehicle that would operate off of conventional runways using liquid hydrogen or perhaps liquid methane fuel, flying at very high altitudes over ranges typically in excess of 3,000 miles. At block speeds of Mach 6, almost anyplace in the world would be within two hours of Los Angles. He also commented that for a system designed to be capable of attaining speeds of Mach 25 block speeds of Mach 6 would not be difficult to achieve.

The motivation for developing such an aircraft can be found in industry and Commerce Department studies looking at the economic impact of increased speeds on air transportation. These project vast increases in revenue passenger kilometers in the Pacific Rim area. In particular, one Commerce Department study suggested that by the year 2000 the Pacific Rim countries will constitute the world's economic center. This may justify the establishment of a new high speed transportation system to service these routes.

Combined with this is the fact that 80% of the direct operating cost of an aircraft is attributable to fuel. Moreover, the curve of cruise efficiency (the equivalent of miles-per- gallon) vs. Mach number is U-shaped. The lowest efficiency is found at speeds slightly in excess of Mach 2, or approximately the speed of present day supersonic transports such as the Concorde. At speeds of Mach 6 or Mach 8 projected fuel efficiency equals that of present day high-efficiency air transport systems such as the Boeing 747. At such speeds overall productivity will also vastly increase because aircraft can fly two round trips per day over transpacific distances. (In contrast with a single one-way trip for current airliners.) These factors may combine to make hypersonic transports economically viable.

Williams also discussed the environmental implications of the TAV, with particular emphasis on current concerns over depletion of the ozone layer. He displayed a chart showing ozone distribution as a function of altitude. The main point, according to Williams, is that the ozone shield, the protective layer that keeps out ultraviolet radiation exists mainly at altitudes of 60-80,000 feet. He noted that the main environmental objection to a U.S. supersonic transport was that it would cruise at those altitudes and the nitrous oxide it would emit would cause the ozone layer to deteriorate. It is hoped that NASP-derived aircraft, on the other hand can operate at altitudes of approximately 120,000 feet. At that level the ozone content of the atmosphere is relatively low. Not only that, but according to Williams, studies indicate ozone levels will remain stable despite such operations. While some ozone depletion will occur, high altitude radiation will reestablish the loss. He cautioned, however, that this was only a "first look" and that confirmatory investigation was needed.

Another important environmental concern is noise. Studies of this problem have shown that for planned TAV takeoff and climb modes overall engine pressure and jet velocity noise levels will be on the same order as conventional turbofan-type aircraft. The aircraft will transition from subsonic to supersonic flight while in a steep climb. This will cause the sonic boom to be propagated upward and away from the Earth's surface. Since it is planned that the TAV will cruise at very high altitudes, it is calculated overflight noise at ground level be about one-sixth that generated by present day supersonic aircraft. This will result not only from the distance of the aircraft above the ground but from the thinness of the atmosphere at such extreme altitudes. Williams admitted, however, that there will be a sonic boom on descent. He stated that it is not yet clear how strong this will be. In particular, it is not presently known whether this will necessitate that the aircraft make its descent over water. However, Williams noted that most of the routes over which hypersonic transport aircraft are expected to operate will provide opportunities for such overwater descents if required. He therefore asserted that, while the aircraft will not be silent, acoustics do not appear to present a serious drawback.

In response to a question Williams stated that it is too early to say how air transportation variants of the NASP might be integrated with national air traffic control system. Replying to another question, Williams admitted that the necessary infrastructure for hydrogen production and transport, especially to support operations of hypersonic airliners, still remains to be developed. He stated however that there are a number of different options in this regard. For example, Space Shuttle operations have already resulted in the production of hydrogen in larger quantities than ever before. He also pointed out that the United States has a very well developed natural gas pipeline system. Natural gas in its simplest form is methane (CH4). One potential method of obtaining hydrogen is by combining methane with water which produces carbon dioxide (CO2) and hydrogen. These factors might make possible the use of natural gas to produce hydrogen either at central locations or in situ on airports without the need for much additional infrastructure. However, the focus at present is on the development of the X-30 vehicle itself. It is hoped that as a spinoff the X-30 will drive the country towards thinking more of hydrogen as a major fuel source for aviation.

Turning from what he described as the "programatics," Williams proceeded to make some historical comparisons. He displayed a slide of the Bell XP-59A, the first manned turbojet airplane to fly in the United States. The X-30, Williams contended could be thought of as being analogous. He pointed out that the XP-59A had led first to jet fighter aircraft and then to the KC-135 tanker, which in turn gave birth to the 707 airliner. He believes that the NASP program will progress along similar lines. It will start with an experimental aircraft and then proceed to hypersonic cruise and/or space launch type applications. He envisions the scramjet having the same impact on the aviation community as did turbojet vis-a-vis the piston engine.

Williams then returned to the NASP itself and discussed the overall development schedule. Phase one of the program is complete. In 1989 a choice will be made between General Electric Pratt & Whitney and Rocketdyne as prime contractor for the engines. On the airframe side, the planning at the time of Williams' talk was for the program to downselect from five to two or three competitors in October of 1987. (As of the time this is uploaded the writer has not seen any report indicating this has in fact been done.) The major reason for this is to allow the airframe contractors to work more closely with those involved in the propulsion portion of the program. This in turn results from the need for integrated airframe and engine design previously alluded to. At this point each of the remaining airframe contractors will be alloted contracts worth about $35 million for the technology development phase of the program.

The most critical juncture in the program, however, will be what Williams called the "assessment milestone." This will be the point at which DARPA will have to first decide itself and then inform Congress whether we are ready to proceed with building the X-30 aircraft. At the point that the decision is made to build the vehicle, DARPA will cease to be responsible for program. The NASP will be turned over to the Joint Program Office which will oversee the development of the X-30 to flight configuration.

In the final part of his presentation, Williams discussed some of the financial applications of the NASP program. Total funding is $3.3 Billion. This will fund the development of one ground test and two flight vehicles. About $230 million will be spent on technology maturation. This part of the work is taking place mostly in government laboratories and small companies. In answer a question, Williams said that 1% of the total program budget was spent on looking at potential applications, civil and military, space and atmospheric, for the technology being developed. Some of this applications, he asserted, will see application sooner than the final vehicle.

NASA's share of the NASP program will increase by 50% in fiscal year 1988. This increase only relates to funding. The management structure will of the program will not change. The increase in NASA's share of the NASP vis-a-vis DoD was ostensibly due to the civil applications of the vehicle. Williams implied, however, that is was really an outgrowth of the debate over which agency's budget should be charged with the cost of paying for a replacement Shuttle orbiter. He suggested that, in effect, funds which DoD had planned to spend on TAV research were charged to the cost of the new orbiter and in return additional funds from NASA's budget were allocated to the NASP.

The funding for the TAV has been fully approved by both DoD and NASA. However, stated Williams, that Congressional approval fluctuates from day to day. This is in part attributable to the fact that the program must deal with some 47 Congressional committees. While Williams was necessarily restrained in discussing this aspect of aerospaceplane development, he did remark during the question period that the NASP program needed a patron on the Senate side. He also indicated that a dilemma existed in attempting to obtain political support. On the one hand, the NASP program office did not wish to raise high expectations by emphasizing the potential of the program and then have "to turn around and say 'look, folks, this is a tough, tough job.'" On the other hand, Congress tends to be reluctant to fund programs where no specific requirement is claimed to exist.

In conclusion, Williams reiterated that on the one hand the X-30 program was a technology development program, unconstrained by any operational requirements. On the other hand it represents an effort to focus the national technology base and laboratory structure on a specific vehicle. In this apparent dichotomy, he implied, lies the program's major strength.

Responding to a questioner who asked if he could say "with certainty at this point" that the TAV's propulsion system would be able to power a vehicle into low Earth orbit, Williams described the NASP as a "high risk-high payoff program." This is why DARPA has been selected to lead it. At the present time DARPA feels comfortable in saying that there are no technology barriers to achievement of the program's objectives. "At the same time," he stated "we are concerned about the engineering challenges that lie ahead." He indicated that if the program were subject to a very tight time schedule and a specific set of operational requirements DARPA would be a lot less confident. However, since it involves an experimental vehicle, the X-30 program has the advantage of being able to proceed at the pace at which technology develops.

In response to another questioner who asked about the design of the leading edge of the wing, Williams stated that the projected vehicle would have the ability to fly at subsonic speeds. In particular, it would be designed so as to have ferry capability as well as the ability to safely abort by doing a go- around in the event of an engine failure on takeoff. The space launch derivative will additionally be designed so that if the payload is sacrificed it will be able to re-enter, restart its engines and fly in the atmosphere to its destination.

The writer then asked Williams to comment the assertions by proponents of rocket propulsion that air-breathing space launch systems were impractical, or at least not cost effective. Williams reiterated his earlier remarks that what he called a "cultural conflict" existed in this area. He attributed this to the fact that people who have been making their living designing or building one type of system tend to experience "heartburn" when somebody else asserts that there is a better way of doing the same thing. Williams indicated, however, that a good indication of the true feelings of the aerospace industry towards scramjet powered launch vehicles is the investment by the Rocketdyne division of Rockwell of extensive amount of its own resources to investigate air-breathing propulsion. (According to Williams the head of that organization had jokingly offered to change its name to "Aerodyne.")

Williams told another questioner that the TAV will have a much higher lift/drag ratio than the Space Shuttle, which he described as a "flying brick."

Williams also stated that there were ample opportunities for other contractors who wished to participate in the aerospace plane program to do so. The subcontractor base is extensive and the list of participants in the program is constantly changing. Very little about the NASP program is classified. Even as to those areas that are classified, it is not difficult for companies or individuals who have the proper clearances. Companies that are interested should contact the program office. If a potential participant has something in particular that he wishes to talk about the program office will listen to a feasibility briefing and direct the applicant to the right prime contractor or agency.

A person attending the meeting commented that while the potential of the NASP was mind-boggling, one of the most massive problems associated with the program was the need to generate the necessary political support. In particular, this person posed the rhetorical question "if $3 billion is the cost of two experimental aircraft, what will be the cost of developing the potential applications?" He also remarked that among those present were "a bunch of pragmatists from Wall Street *** (who) want to know 'how do you make a buck on this program.'" As a result it was, this commentator believed necessary to "make it clear that the development of the technology itself is going to be very, very important to the country."