AW&ST:
Orbital Test Vehicle: Reusable Spacecraft
Apr 21, 2010
Colorado Springs
A U.S. Air Force Space Command flight test of the X-37B Orbital Test Vehicle, scheduled to launch April 20 from Cape Canaveral AFS, Fla., atop an Atlas 501, will serve as an “on-orbit” demonstration of space vehicle technologies as well as pioneer reusable spacecraft operations.
Originally a NASA program, the X-37B’s exact mission has been increasingly cloaked in secrecy since it was taken over by the Air Force, which initially worked the program in conjunction with the Air Force Research Laboratory and Defense Advanced Research Projects Agency (Darpa). The 29-ft.-long, 15-ft.-wingspan vehicle resembles a small space shuttle in overall form, and was designed to test human spaceflight technologies under NASA before transitioning to Darpa in 2004.
Although it was dropped in 2007 from the Scaled Composites WhiteKnightOne mothership for atmospheric glide, approach and landing tests to Edwards AFB, Calif., the 11,000-lb. X-37B has not flown into space until now. With just inches to spare within the 5-meter (16.4-ft.) fairing of the Atlas vehicle, the OTV will be launched by the 45th Space Wing into an orbital mission that could last as long as 270 days before the spacecraft autonomously recovers to a landing at Vandenberg AFB, Calif. Defense officials indicate, however, the first mission will be considerably shorter than this.
In the April 22 mission led by the Air Force Rapid Capabilities Office, which expedites development and fielding of select Defense Department weapon systems, the initial test of the OTV will be focused on the performance of the vehicle itself. “Technologies to be tested include advanced guidance, navigation and control; thermal protection systems; avionics; high-temperature structures and seals; conformal reusable insulation; and lightweight electromechanical flight systems,” says the Air Force. “The X-37B will also demonstrate autonomous orbital flight, reentry and landing. The platform will be used for long-duration space technology experimentation and testing,” it adds.
Follow-on flights, set for an unspecified time frame, will begin to focus more on testing of spacecraft technology and deployable payloads that the OTV will carry in its cargo bay. In its original NASA guise, the bay measured 7 X 4 ft., though it is not known if the Boeing Phantom Works-built vehicle has been significantly modified in this regard since moving into the defense realm.
In its most informative statement, the Air Force says the OTV will provide “a flexible space test platform to conduct various experiments and allow satellite sensors, subsystems, components and associated technology to be efficiently transported to and from the space environment. This service directly supports the Defense Department’s technology risk-reduction efforts for new satellite systems. By providing an ‘on-orbit laboratory’ test environment, it will prove new technology and components before those technologies are committed to operational satellite programs.”
What remains unknown are the types of on-orbit experiments that will be conducted by the OTV, the new sensors that will be tested and the extent to which the OTV operation itself will be used to demonstrate reusable, fast-turnaround missions being sought by advocates of operationally responsive space.
Editor's Note: When this week's magazine was published, the X-37B mission was scheduled for April 20. As of today it is scheduled for April 22 and changed to that date above.