In Focus: The Swarm Option
The Advanced Aerospace Vehicle
Senior Administration officials recently told a congressional panel that the White House plans to decide in January 1986 whether or not to launch a comprehensive $500 million effort to establish the feasibility of an Advanced Aerospace Vehicle (AAV), also known as the aerospace plane. If the technical feasibility of such a vehicle is established at the end of the program’s first phase, the Air Force—in concert with other Defense Department elements and NASA—would, about three years from now, start the development of a prototype flight research vehicle, the X-31 (sic) , at an estimated cost of between $2 billion and $3 billion. Flight testing of the AAV might begin in the early 1990s, if the current schedule is maintained.
The initial funding approach to the AAV project, whose military portion is code-named “Copper Canyon,” envisions a cost-sharing arrangement involving the Defense Department—which would pay for about eighty percent of the cost—and NASA, whose share would cover the remaining twenty percent.
General Skantze credits AAVs with meeting a host of potential future requirements by SAC, TAC, MAC, and the unified Space Command. The US Navy has also formally expressed a long-term interest in the aerospace plane program. The central traits that attract the Pentagon to AAV, according to General Skantze, are that it responds “with the speed of an ICBM and the flexibility and recallability of a bomber.” In fact, the AAV is a “plane that can scramble, get into orbit, and change orbit so the Soviets can’t get a reading accurate enough to shoot at it. It offers strategic force survivability, [because a fleet of AAVs] could sit alert like B-52s.” Among the host of potential missions that such a vehicle could perform, one stands out from the military point of view, according to the AFSC Commander: “It could mean low-cost, reliable access to space—precisely what’s needed to open up the space frontier for routine operations.”
Forecasts about just how much AAVs might be able to lower the cost of delivering payloads to orbit vary at this time, but in general envision reductions from current levels that extend from twentyfold to about a hundredfold. According to James Tegnelia, acting director of DARPA, an air-breathing AAV could shed about 4,000,000 pounds compared to the rocket-propelled Space Shuttle’s 4,500,000-pound takeoff weight and still deliver roughly the same payload to orbit. The Shuttle carries along its own oxydizer; the AAV, by contrast, burns the oxygen in the air.
The AAV project, White House Science Advisor Dr. G. A. Keyworth II told the Congressional Aviation Forum recently, could serve a range of national interests that extends on the civil side from future hypersonic transports to space transports and in the military sector from vehicles serving in tactical and strategic missions to space launchers. Recent work by NASA, DARPA—the latter involving several Air Force laboratories—and industry has led to the realization that, in the civil transportation sector, AAV technology “may allow us to … literally skip a generation of aircraft and spacelaunch technology.”
According to DARPA’s Mr. Tegnelia, AAV technology is likely to branch out into two basic areas: vehicles that come under the heading of hypersonic aircraft—nicknamed the “Orient Express,” that would operate in the Mach 12 range at altitudes between 120,000 feet and 150,000 feet—and aerospace planes that reach speeds of Mach 26 and operate at altitudes of about 350,000 feet. The hypersonic transport sector might be subdivided into a lower-speed regime—below Mach 10—that uses methane as a fuel and systems that operate above that speed and that use liquid hydrogen.
Fanning the technical community’s optimism with regard to AAV technology are recent advances in three generic areas. One is the advent of such advanced materials as carbon/carbon composites that get stronger as they get hotter rather than weaker. That is the bane of metals, including even titanium. The new composites, which are used in ballistic missile reentry vehicles and the Space Shuttle, can withstand temperatures well above 3,000 degrees on a sustained basis.
Secondly, new approaches to ramjet/scramjet propulsion have been tested out, with encouraging results at speeds of about Mach 10. Lastly, revolutionary advances in simulating aerodynamic flowfields in three dimensions with the help of recent dramatic advances in computer capability virtually eliminate the need to design such advanced aerodynamic shapes on a trial-and-error basis.
