Crew Return Vehicle
[2][citation needed] A number of studies have attempted to assess the medical risks for long-term space station habitation, but the results are inconclusive, as epidemiological data is lacking.
[2] Because of its potential use as a medical evacuation method, the CRV design was required to address a number of issues that are not factors for a standard crewed space vehicle.
Additionally, depending on the nature of the injury, it may be unlikely that the patient could be placed in an environmentally contained space suit or minicapsule, therefore the CRV needs to have the capability to provide a "shirt sleeve" environment.
[7] The idea of using a Russian-built craft as a CRV dates back to March 1993, when President Bill Clinton directed NASA to redesign Space Station Freedom and consider including Russian elements.
[12] However, in 1995, a joint venture between Energia, Rockwell International and Khrunichev proposed the Lifeboat Alpha design, derived from the Zarya reentry vehicle.
The reentry motor was a solid propellant, and maneuvering thrusters utilized cold gas, so that it would have had a five-year on-station life cycle.
[15] The CRV design concept incorporated three main elements: the lifting-body reentry vehicle, the international berthing/docking module, and the Deorbit Propulsion Stage.
[14] The Deorbit Propulsion Stage was designed by Aerojet GenCorp under contract to the Marshall Space Flight Center.
The module was designed with eight 100 lbf (0.44 kN)-thrust rocket engines fueled by hydrazine, which would burn for ten minutes to deorbit the CRV.
Instead, the CRV was to have a "virtual cockpit window" system that used synthetic vision tools to provide an all-weather, day or night, real-time, 3-D visual display to the occupants.
The ram-air inflated parafoil used in the flight test program was the largest in the world, with a surface area of 7,500 sq ft (700 m2).
[22] NASA's plans for the development program did not include an operational test of the actual CRV, which would have involved it being launched to the ISS, remaining docked there for up to three months, and then conducting an "empty" return to Earth.
Three independent review groups, as well as the NASA Office of Inspector General, expressed concerns about the wisdom and safety of this plan.
Furthermore, funding of the CRV program was tied to Administration justification of the mission of the ISS: By March 1, 2002, the President shall submit to the Committees on Appropriations of the House and Senate a comprehensive plan that meets the following terms and conditions: First, a clear and unambiguous statement on the role of research in the International Space Station program.
[24]On April 29, 2002, NASA announced that it was cancelling the CRV and X-38 programs, due to budget pressures associated with other elements of the ISS.
One of the key missions for the OSP, as defined by NASA in 2002, was to provide "rescue capability for no fewer than four Space Station crew members as soon as practical, but no later than 2010."
None of the existing hardware (such as CMs in Museums) was thought to be usable, because of age, obsolescence, lack of traceability, and water immersion.
Although the flight hardware would be less expensive, and its impact on the Expendable Launch Vehicles would be minimal (it's just another axisymmetrical payload), the landing sites for the CRV may drive the Life Cycle costs high.
By adding a Service Module (smaller than the one required to go to the Moon), orbital cross-range of 3000 to 5,000 ft/s (1,500 m/s), might be gained, and the number of landing sites radically reduced.
To make them more compatible with the needs of the ISS, Energia was contracted to modify the standard Soyuz TM capsule to the TMA configuration.
[34][35] The main modifications involve the interior layout, with new, improved seats to accommodate larger American astronaut anthropometric standards.
[36] A series of test drops of the improved capsule were made in 1998 and 1999 from an Ilyushin Il-76 cargo plane to validate the landing capabilities of the TMA.
Operated in this configuration, the TMA had a lifespan of about 200 days before it has to be rotated out, due to the degradation of the hydrogen peroxide used for its reaction control system.
In 2008, NASA began administering a program (CCDev) to fund development of commercial crew transportation technologies.
The first round of recipients in early 2010 included Boeing for its CST-100 capsule and Sierra Nevada Corporation for its Dream Chaser spaceplane.
Further proposals submitted at the end of 2010 for a second round of funding included Orbital Sciences Corporation for its Prometheus spaceplane and SpaceX for developing a launch abort system for its Dragon spacecraft.
