UDRI Technologies to Enable Quick Reuse of Space Vehicles

A spaceship, newly arrived after fulfilling its mission in orbit, is inspected, repaired and returned to space – on the same day. Science fiction? Not for long. At the University of Dayton Research Institute, engineers are working to make FAST space travel an early 21st century reality.  FAST, or Fully-reusable Access to Space Technology, is an Air Force program comprising a number of technologies necessary to enable rapid return to space, said Tim Fry, a research engineer in the Research Institute’s Aerospace Mechanics division. UDRI is analyzing and designing thermal protection systems for that program.

In the 50 years since the first successful launch of a manmade satellite, the world’s space agencies have made enormous strides in their reach for the stars. But space missions are expensive, said research engineer Steve Olson. In order for rapidly reusable space vehicles to be viable, their launch costs must be significantly reduced from current shuttle launch costs. “The key to reducing those costs is to reduce turn-around time,” Olson said.

“We want to be able to fly space vehicles the way we fly airplanes,” added Fry. “Land them, inspect them, refurbish them and get them back out. Currently, it takes thousands of man hours to ready a shuttle for re-launch in terms of the TPS alone. We want to cut that time down to about eight hours.”

Olson and Fry are working on complementary programs that will facilitate rapid inspection and repair of thermal protection systems designed for shuttle-like spacecraft. Fry’s program involves developing TPS materials that can repeatedly withstand the extreme high temperatures, vibration and noise that space vehicles endure during launch and re-entry, as well as protection systems that lend themselves to swift repair and/or replacement.

“The heat shield is one of the most critical elements of a space craft, because it protects all the goodies inside,” Fry said. “And when one of those birds comes in at about Mach 20, it’s going to get hot – about 3,000 degrees Fahrenheit. That kind of heat is very damaging, even to materials designed to withstand it. Our goal is to develop material that can withstand those kinds of temperatures over and over and over again.”

In addition to materials development for TPS, engineers at UDRI are working with those at the Air Force Research Laboratory at Wright-Patterson Air Force Base, NASA and industry to develop entire heat-shield systems designed for quick repair. Current systems comprise ceramic tiles that are thick, fragile and time-intensive to refurbish, which also makes them quite costly, Fry said. “We’re looking at creating larger panels of protective material that will be lighter yet more durable. There are several issues to be addressed for this part of the program, such as how to attach the new system to an operational vehicle that has seals and seams and will be pitching and rolling and twisting and flexing in flight. As those pieces move, we need protective panels and seals that can accommodate for the movement as well as for thermal expansion.”

Fry said another challenge will be to find a way to mechanically attach TPS panels with a quick-release mechanism, rather than the bonding method currently used for shuttles. “We’ll want to be able to easily pop off damaged panels for repair or replacement – but we don’t want them coming off on their own during re-entry.”

Olson’s work involves the inspection side of rapid reusability. “We’re charged with finding a way to quickly yet thoroughly assess the condition of the thermal protection system,” he said. “While the TPS is critical to the protection of the space vehicle, it is itself extremely vulnerable to damage by orbital debris.”

Visual inspection for cracks, bolt failures or impact damage following a mission can take weeks, Olson said. To significantly reduce that time, researchers are developing an automated structural health monitoring system that will not only complete the same task in a fraction of that time, but perform the job more completely. “The automated system will use sensors to examine changes in vibration that flag potential trouble spots in minutes. It will also be able to detect a crack below a heat panel that could not be seen with the naked eye.”

Olson said the automated system can also be used to quickly re-certify spacecraft flight readiness after it has been repaired.

June 1, 2007