The Air Force’s funds were added to the $173 million cooperative agreement between NASA and the Boeing Company signed July 14, and has shaped several facets of the X-37 reusable space technology demonstrator, according to NASA’s program manager for advanced space transportation.

Gary Payton, head of NASA’s series of X rocket research craft, told space.com that the Air Force wanted specific orbital capabilities added to the X-37’s mission profile and subsystems. "These included solar arrays and a vernier engine system," Payton said Tuesday during a review of the X-37 project at NASA headquarters.

The systems added to the five-week-old project allow the X-37, the only NASA X rocket currently in development that can orbit the Earth, to research several capabilities considered crucial to future military spaceplanes.

These include the ability to approach a satellite and conduct proximity operations and station-keeping, remain in space for weeks at a time, and have ultra-fine flight control for "precise aiming," Boeing X-37 project manager David Manley said.

The vernier rocket engine will allow on board computers to move the space vehicle in short, controlled motions that would be needed to approach a satellite and perhaps move about the craft in a tight circle for inspection.

Such a space capability is believed to be high on the Air Force's list for future generations of military spaceplane craft now in the research and study stage at Air Force Space Command in Colorado Springs, Colorado.

The large deployable solar panels that have been added to the craft as a result of the Air Force funding will also allow the X-37 to stay in orbit longer than original NASA plans.

The craft, 27.5 feet long and with a 15-foot wingspan, will be carried into space aboard NASA’s space shuttle in late 2002.

Once released from the payload bay of the shuttle, the X-37 will conduct a two-day space mission, deploy payloads or satellites for either NASA or the Air Force, and return to Earth, gliding back to either Edwards Air Force Base or Vandenberg Air Base, both in California.

With no pilot aboard, the X-37 will test 41 advanced space technologies that might be employed in future NASA, commercial, or military spaceships. On a second test flight from the shuttle in 2003, the X-37 will remain in space for 21 days and carry out rendezvous and station keeping operations with an as-yet unselected satellite.

The craft’s four foot by seven-foot payload bay will allow the vehicle to carry up to 500 pounds of research equipment or experiments. The Air Force and NASA are in negotiation as to what military experiments will be performed by the X-37.

Future versions of the craft might be lofted aboard expendable launch vehicles or air dropped from aircraft.

The project originated from an Air Force program to develop a Space Maneuver Vehicle (SMV), a reusable winged satellite that could perform a variety of military missions in space, including deployment of other satellites, weapons, anti-satellite devices, or inspection of enemy or hostile satellites.

A scale model of the X-37, called the X-40A, was dropped from a helicopter Aug. 11, 1998 above Holloman Air Base in New Mexico and landed under remote control on a runway. Additional X-40A model tests will be conducted to help verify the shape and flight control system of the full size X-37.

Both craft will use Global Positioning System (GPS) signals for guidance and control. Boeing and NASA will share the costs of the project on a 50-50 basis, Payton said.