Up a creek without a paddle? Not if you're an International Space Station astronaut with a CRV. That's short for Crew Return Vehicle, and it's being developed following an innovative approach in the X-38 program. The CRV will perform three specific roles:
- A lifeboat if the space station becomes uninhabitable;
- An ambulance if a crewmember becomes sick or injured; and
- A way home if the space shuttle is unavailable.
The CRV is a 30-ft (9.1-m) long spacecraft that will be moored on the station and will carry up to seven crewmembers safely back to Earth. Designed to replace the three-person Soyuz vehicle used in early space-station operations, it is completely autonomous, can carry the entire station crew, has significant cross-range capability, and can make ground-based, low-speed, soft landings at predefined sites around the world by use of a large parafoil.
In response to Administrator Dan Goldin's challenge to build a new spacecraft to transport humans in a better, faster, cheaper way, engineers at NASA's Johnson Space Center conceived the X-38 program to solve the technical issues associated with the development of the CRV. The X-38 program relies on a series of low-cost, unpiloted development vehicles to perform flight demonstrations of innovations to be incorporated into the CRV. Paramount among the innovations is the parafoil and its control mechanisms. The proper selection of innovations makes it possible to build and test the prototype CRV quickly; as a result, the experience needed for designing and building the CRV can be gained early in the development cycle. A total of five vehicles will be used to test various parts of the eventual CRV mission.
The first of the X-38 vehicles successfully made its maiden flight in March 1998 at Dryden Flight Research Center. Launched from Dryden's venerable B-52 mother ship at an altitude of 23,000 ft (7 km), the vehicle known as V131 deployed a drogue parachute and parafoil on cue and glided to a soft landing on the Precision Impact Range Area at Edwards Air Force Base. The flight marked the first time a parafoil of this size (larger than the B-52 wing area) had been deployed from an aerodynamic-lifting-body aircraft. Although some minor problems were encountered, the test demonstrated the feasibility of the parafoil concept.
Like the familiar wedding couplet - "Something old, something new" - the X-38 blends proven technology with state-of-the-art technology. The basic lifting body shape is derived from the X-24A program tested at Dryden in the 1960s and 1970s. Data on re-entry aerodynamics and heating were recovered from flights in the X-23 program undertaken by the Air Force in the mid-1960s. Flight-proven components from the space shuttle have been used to reduce risk wherever possible. Conversely, the parafoil, electromechanical flight surface actuators, and fiber-optic systems are all examples of emerging technology being used to augment CRV capabilities. The use of the parafoil provides a low-speed, soft-landing capability without the need for a pilot or a prepared runway. Unlike traditional hydraulic actuators, the electromechanical actuators afford a leak-free, non-freezing capability for the intended three-year stay of the CRV at the station.
To increase the likelihood of a successful X-38 program, the Johnson Space Center X-38 team has enlisted several partners. In addition to providing the B-52 launch capability, Dryden has assisted with flight controls and flush air-data systems advice, and general flight-test and range-safety expertise. Pioneer Aerospace Corporation has led the development of the parafoil, and the Army has provided test facilities at Yuma Proving Ground. In an example of an international cooperative effort, the European Space Agency and the German National Space Agency will provide several components for the first space flight of the X-38, to be launched from the Space Shuttle in November 2000.
Ideally, the CRV will never be used for a real emergency. However, the recent problems with the Mir space station illustrate the need for a way home, just in case. The CRV will be there for astronauts in case they need it.
This work was done by John F. Muratore of Johnson Space Center and Christopher J. Nagy of Dryden Flight Research Center. DRC-98-90