Crew Return Vehicle (CRV)
The International Space Station (ISS) provides the world with an orbiting laboratory that will have long-duration microgravity experimentation capability. The crew size for this facility depends upon the crew return capability. The crews consist of three astronauts from Russia and the United States and other participating countries. The crew is limited to three because the Russian Soyuz TMA vehicle that will remain docked to the ISS can only hold three people. It is imperative that the crew members be able to return to Earth if there is a medical emergency or if other complications arise. A Crew Return Vehicle able to hold up to seven crew members was planned from the outset. This would have allowed the full complement of seven astronauts to live and work onboard the ISS.
The Crew Return Vehicle, or X-38, design used a lifting body concept originally developed by the U.S. Air Force in the mid-1960s. These wingless lifting bodies attain aerodynamic stability and lift from the shape of the aircraft. Lift results from more air pressure on the bottom of the body than on the top. Following the jettison of a deorbit engine, the X-38 would glide from orbit and use a steerable, parafoil parachute for its final descent to landing. The high speeds at which lifting body aircraft operate make it dangerous to land. The parafoil would have been used to slow the vehicle down and make it safer. Its landing gear consisted of skids rather than wheels. The skids worked like sleds so the vehicle would have glided to a stop on the ground.
Both the shape and size of the X-38 were different from the traditional Space Shuttle. The Crew Return Vehicle could have fit into the payload bay of the Space Shuttle. This does not, however, mean that it was small. The X-38 weighed 10,660 kg and is 9.1 meters long. The battery system, which keep its charge for nine hours, was to be used for power and life support. If the Crew Return Vehicle was needed, it would only take two to three hours for it to reach Earth.
The parafoil parachute, employed for landing, was derived from technology developed by the U.S. Army. This massive parafoil deploys in stages for optimum performance. A drag chute would have been released from the rear of the X-38. This drag chute would have been used to stabilize and slow the vehicle down. The giant parafoil?area of 687 square meters?was then released. It would open in four stages (a process called staging). While the staging process only takes 45 seconds, it is important for a successful chute deployment. Staging prevents high-speed winds from tearing the parafoil.
The spacecraft?s landing was to be completely automated. Mission Control would have sent coordinates to the onboard computer system. This system would also have used wind sensors and the Global Positioning System (a satellite-based coordinate system) to coordinate a safe trip home. Since the Crew Return Vehicle was designed with medical emergencies in mind, it makes sense that the vehicle could find its way home automatically in the event that crew members were incapacitated or injured. If there was a need, the crew would have the capability to operate the vehicle by switching to the backup systems.
Some of the technologies used for the creation of the X-38 came from many places and were not new. Combining these technologies with new ideas and capabilities created a vehicle that would have been be tasked with the mission of carrying home the crew of the ISS if there had been an onboard emergency. By utilizing technologies from the 1960s in the 1990s and by being fast, safe, and dependable, the Crew Return Vehicle would have provided peace of mind to all those living and working onboard the ISS.
The Crew Return Vehicle was cancelled in 2001 and the Soyuz TMA will continue to be used for the foreseeable future. This will limit the ISS crews to three.
