December 02, 2013
Never deterred by past failures, the U.S. Defense Advanced Research Project Agency (Darpa) once again wants to develop a reusable-spaceplane launch vehicle to reduce dramatically the cost and time required to orbit satellites.
This time, the agency's goal with its new Experimental Spaceplane (XS-1) program is to demonstrate a reusable capability that can transition to industry for low-cost military and commercial satellite launches as well as hypersonic technology testing.
The agency usually hands off successful programs to one of the U.S. armed services, but “Darpa's XS-1 transition partner is you—industry,” program manager Jess Sponable told attendees at a proposers' day briefing last month. In addition to enabling lower-cost, more responsive launches of U.S. government satellites, Darpa sees the reusable first-stage technology to be demonstrated under the XS-1 program as key to recapturing a commercial launch market lost to foreign competitors.
The program goal is to fly an X-plane reusable first-stage to demonstrate technology for an operational system capable of launching 3,000-5,000-lb. payloads to low Earth orbit for less than $5 million per flight at a launch rate of 10 or more flights a year. This compares with around $55 million to launch that class of payload on the Orbital Sciences Corp. Minotaur IV expendable booster, which operates at a flight rate of around one a year, according Darpa.
Invoking the original designation of the first aircraft to break the sound barrier, the Bell X-1, the XS-1 would be a companion to Darpa's Airborne Launch Assist Space Access (Alasa) program to demonstrate an aircraft-based launch system capable of placing 100-lb. payloads into low Earth orbit for less than $1 million per flight, including range costs. Preliminary design contracts for Alasa were awarded to Boeing, Lockheed Martin and Northrop Grumman in 2012.
Previous attempts to develop a reusable launch vehicle have failed, the agency acknowledges, arguing that the late-1980s X-30 and late-1990s X-33 VentureStar never flew because the designs were technically unachievable with the technology available at the time. Darpa's last attempt at a reusable launcher was the Rascal (Responsive Access, Small Cargo, Affordable Launch) program of the early 2000s, aimed at placing 300-lb. payloads into orbit for less than $750,000.
Under development by Space Launch Corp. and Scaled Composites, Rascal was a specially designed Lockheed SR-71-size supersonic aircraft powered by four existing turbojet engines modified to high-Mach, high-altitude operation. After takeoff, the manned Rascal was intended to zoom-climb to 180,000 ft. and release an expendable upper stage, then return to a runway landing. Flight demonstrations were planned for 2006, but the program was canceled in 2005.