Early artist rendering of the Towed Glider Air-Launch Concept, showing the towed glider following rocket launch. A notional tow aircraft is seen clearing the launch area. (NASA image) › View Larger Image
The 1/3-scale twin-fuselage glider that would be used to validate the flight characteristics of the Towed Glider Air-Launch Concept is pictured with and its DROID tow plane on the ramp at NASA Dryden. (NASA / Tom Tschida) › View Larger Image NASA's Dryden Flight Research Center is developing a novel rocket-launching technique called the Towed Glider Air-Launch Concept that could significantly reduce the cost and improve the efficiency of sending satellites into orbit.
The idea is to build a relatively inexpensive remotely or optionally piloted glider that will be towed to altitudes approaching 40,000 feet by a large transport aircraft. The glider will carry a booster rocket capable of launching payloads into low Earth orbit.
Engineers continue working trade-offs with launching the rocket either with the glider still in tow, or following release from the tow aircraft. Either way, after the rocket has launched, the glider will return independently of the tow aircraft to its base to be used again.
Gerald Budd, a NASA Dryden business development and towed glider project manager, displayed a 24-foot wingspan, twin fuselage proof-of-concept model of the glider that was constructed in NASA Dryden's model shop during a presentation at the Academy of Model Aeronautics' 15th Annual Expo in Ontario, Calif., in mid-January. The model will fly later this year, towed aloft by one of Dryden's small DROID – for Dryden Remotely Operated Integrated Drone – unmanned aircraft.
Early artist rendering shows the concept of operations of the Towed Glider Air-Launch Concept, beginning with the aero-tow of the glider carrying a rocket booster, launching the rocket, then returning to land independently of the tow aircraft. (NASA image) › View Larger Image Recent feasibility analyses done by independent contractors indicate that a performance gain of up to 40 percent may be realized by use of Budd's towed-glider technique over vertical launch of a similar-sized rocket from the ground.
Additionally, air launch of rockets has the potential to lower the cost of placing payloads to orbit through operational efficiencies that are simply not available through vertical ground launch, Budd explained. Cost savings may be as much as 25 percent, based on recent Defense Advanced Research Projects Agency studies.
Historically, air-launched rockets have been carried and dropped from underneath modified, existing aircraft, such as Orbital Sciences' Pegasus rockets that are launched from the firm's modified L-1011 "Stargazer" launch aircraft. Currently, a huge new custom-built carrier aircraft is under construction by Stratolaunch Systems, Inc.
Budd maintains the Towed Glider Air Launch Concept has the potential to realize the operational flexibility of a custom airplane, but without the price tag.
"It's a real-estate problem," said Budd. "You're limited in what you can fit underneath an existing aircraft. Launching off the top of a carrier aircraft is problematic from a safety perspective. Our approach allows for significant payloads to be carried aloft and launched from a purpose-built custom aircraft that is less expensive because of the simplicity of the airframe, having no propulsion system (engines, fuel, etc.), on board," Budd said.
This initial research and development effort is being funded internally by NASA Dryden at Edwards Air Force Base in California, and by NASA's Office of the Chief Technologist. Potential Department of Defense and industry partnerships are being explored.