Suborbital spacecraft may play an important role in training astronauts for orbital and deep-space missions.

Today, US astronauts (and their foreign counterparts) receive no training on rocket-powered vehicles prior to their first orbital flight. Whether they are pilots or payload operators, they are “thrown into the deep end of the pool” on their first space mission. Space agencies attempt to compensate, through extensive ground-based training and simulation, but the step up from ground-based training to actual flight is still enormous. Then, completing their mission, astronauts face a gap of many months or years before their next flight. Military and airline pilots have to meet regular “currency requirements,” but astronauts have no way to stay current in rocket-powered vehicles.

NASA has recognized the potential value of suborbital spacecraft for astronaut training. In 2008, NASA Administrator Mike Griffin said, “We could use commercial suborbital human transportation for early training and qualification of astronauts. If I could buy a seat to suborbital flight for a few hundred thousand dollars, why wouldn’t we have all of our new astros make their first flight in such a manner?” NASA never followed through on proposed studies of such training, however, perhaps because of budget overruns in other areas.

Commercial space companies are interested, however. XCOR Aerospace and Excalibur Almaz recently signed a memorandum of understanding that would open the door for XCOR to provide training for Excalibur Almaz astronauts using the Lynx spacecraft. If the idea catches on, suborbital spaceflight may become a standard part of the training toolkit for all future astronauts.

Such training could provide additional impetus for the development of a commercial spaceports near national space centers. It could be a particular boon to Texas. There has already been talk of establishing a suborbital spaceport at Ellington Airport, adjacent to NASA’s Johnson Space Center. Commercial suborbital spacecraft would be a useful supplement to the fleet of T-38 Talon jet trainers which NASA already has based at Ellington.

Excalibur Almaz Space Expeditions

Excalibur Almaz is marketing a commercial space capsule called the RRV, or Reusable Reentry Vehicle, based on the TKS capsule developed by the Soviet Union during the Cold War. The TKS capsule was intended for use with the Almaz (military Salyut) space station. It was tested in an unmanned configuration, but the Almaz program was cancelled before manned flights of the capsule were conducted.

Excalibur Almaz RRV (Reusable Reentry Vehicle) space capsule

Excalibur Almaz has purchased four TKS capsules, which it has upgraded to RRV configuration with new electronics, as well as two Almaz space stations. Excalibur Almaz believes it can use the capsules and space-station modules as part of a transportation system for flights to the Moon, libration points, asteroids, and deep space, as well as the International Space Station.

Suborbital spaceflight will be an integral part of the safety and education program to prepare  Excalibur Almaz crews for orbital and deep-space expeditions. Excalibur Almaz founder and chairman Art Dula says, “The XCOR [Lynx] flights will enhance the overall spaceflight experience of our program and help ensure that our passengers are both mission and medically qualified to fly in space.”

Past Projects

The idea of using suborbital vehicles to accustom astronauts to spaceflight prior to longer-duration missions is not a new one.

In the 1960’s, the United States Air Force realized that suborbital spaceflight would be valuable training for astronauts. At the time, the USAF expected that Air Force astronauts would soon be flying orbital vehicles such as the Boeing X-20 DynaSoar. As a result, it initiated a program to develop a suborbital aerospace trainer.

At first, studies focused on the North American X-15 rocketplane. In November 1960, North American Aviation presented a stretched, two-seat X-15 concept to the Air Force. The two-seat X-15 would be 14 inches longer and 354 pounds heavier than the single-seater. An uprated version of the XLR99 rocket engine would increase performance by 120 feet per second, permitting five minutes of weightlessness. The second cockpit would have dummy flight controls and an isolated life-support system to allow the study of alternative gas mixtures.

The concept was considered for several months but rejected in March 1961 because of cost. At the same time, however, the Air Research and Development Command directed that studies continue to determine the best type of vehicle for training astronaut candidates, or Aerospace Research Pilots as the Air Force called them.

To minimize costs, the Air Force hit on the idea of modifying existing jet fighters. Three Lockheed F-104A Starfighters were modified by adding an auxiliary rocket engine and reaction-control system. Wing tip extensions were added to increase the effectiveness of the RCS thrusters and the vertical tail surface was enlarged as well. The airframes were pulled out of the bone yard at David Montham Air Force Base, so the cost of raw material was very small.

Chuck Yeager piloting Lockheed NF-104 Starfighter astronaut trainer

The Air Force selected a 6000-pound-thrust Rocketdyne AR2-3 rocket engine that burned JP-4 and hydrogen peroxide and had a total burn time of 100 seconds. When started in flight, the engine allowed the NF-104 pilot to zoom-climb to altitudes above 120,000 feet. To save weight and increase maximum altitude, the NF-104 was a single seater. This was not considered to be a problem since the aircraft would be flown by student test pilots at Edwards Air Force Base, who were chosen from among the military’s top pilots.

Unfortunately, the NF-104 program suffered from accidents. In November 1963, an NF-104 piloted by Colonel Chuck Yeager suffered a pitch-up problem. Pitch-up is a loss of control that can occur when aircraft with a T-tail configuration (such as the F-104) are flown at high angles of attack. The NF-104 entering a unrecoverable spin. Yeager  managed to eject, but the aircraft was lost. After the accident, the Air Force placed angle-of-attack limits on the NF-104 that reduced the maximum altitude it could reach in a zoom climb and severely limited the NF-104’s utility as an aerospace trainer.

In December 1963, the development of the X-20 DynaSoar was canceled. It was becoming obvious that the politicians would not allow the Air Force to develop an independent manned space program, and the importance of an aerospace trainer diminished. Maintenance problems and diminished interest kept the NF-104 grounded until 1967. In 1968, the NF-104 finally became operational as a trainer at the Aerospace Research Pilots School in 1968, but in December, 1971, it suffered another accident. This time, a rocket engine blew up in flight. The aircraft was landed successfully, but there was structural damage to the fuselage and rudder. With no military manned space program to train for, the Air Force chose to retire the NF-104’s rather than repair the damage.

In 2002, X-Rocket LLC worked with XCOR Aerospace to study the concept of an aerospace trainer derived from the Russian MiG-21UM supersonic fighter-trainer. Unlike the NF-104, the MiG-21 derivative (called Archangel) would be a completely rocket-powered vehicle. The 13,000-pound-thrust turbojet would be replaced by four 5,000-pound-thrust XCOR rocket engines, allowing zoom climbs to 160,000 feet.

Archangel Aerospace Trainer (MiG-21 derivative)

The Archangel design incorporated substantial improvements over the NF-104. XCOR’s liquid-oxygen/kerosene rocket engines do not require constant maintenance, like the NF-104 engine, nor are they prone to explode. The MiG-21UM airframe is a two-seater, allowing an experienced instructor to train students who were not top military pilots. The airframe has a conventional tail, so is not subject to the pitch-up problem that plagued the F-104, and it has excellent spin recovery characteristics.

A feasibility study showed that the Archangel development could be completed with minimal risk. The required modifications to the airframe were extensive, however, and it was unclear whether the design actually provided a cost advantage compared new airframe from scratch. As a result, X-Rocket elected not to pursue development.

The Future

Flight simulators have come a long way in recent years, but there is still no substitute for flight experience. Simulators provide an incomplete substitute for the actual experience, at best, and negative training at worst.  To quote one former Shuttle command,  “Good in the simulator means bad in the airplane.” Space is a hazardous environment, and those who venture into deep space will want to use every tool available to prepare for it.

Written by Astro1 on June 27th, 2012 , Excalibur Almaz, Innovation, Space History, XCOR Aerospace

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