NASA recently detailed what it called an inexpensive, possibly automated rocket launching system that uses a towed glider to send payloads into low Earth orbit.
NASA's Dryden Flight Research Center Towed Glider Air-Launch Concept would use a glider that would be towed to an altitude of 40,000 feet by a large transport aircraft such as a 747. A rocket would be slung under the belly of the glider and launch after the craft reached its desired altitude.
"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 empty glider will return independently of the tow aircraft to the runway to be used again," NASA stated.
NASA says air launch systems could save as much as 25% over vertical ground launches, according to Defense Advanced Research Projects Agency studies.
"It's a real estate problem," said Gerald Budd, a NASA Dryden business development and towed glider project manager in a statement. "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 a 24-foot wingspan, twin fuselage proof-of-concept glider model being constructed by NASA Dryden that will fly later this year, towed aloft by one of Dryden's unmanned aircraft.
A similar launch system is being developed by entrepreneur Paul Allen and Burt aerospace designer Burt Rutan. Their Stratolaunch Systems craft, announced in 2011 has three components:
- A carrier aircraft, developed by Scaled Composites, the aircraft manufacturer and assembler founded by Rutan. It will be the largest aircraft ever flown.
- A multi-stage booster, manufactured by Elon Musk's Space Exploration Technologies;
- A state-of-the-art mating and integration system allowing the carrier aircraft to safely carry a booster weighing up to 490,000 pounds. It will be built by the Dynetics aerospace engineering firm.
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