DARPA has announced thesecond phase of its ambitious XS-1 program. The agency is seeking tomake access to space more regular and affordable by employing anentirely re-usable high-speed, sub-orbital automated spaceplane asthe first stage of its launch vehicle.

Upon reaching adesignated height, an expendable upper stage would separate from thespace plane, and insert a payload into low-Earth orbit (LEO). Thespaceplane would then autonomously land and be serviced for the nextlaunch.

Phase 1 of the programsaw DARPA award contracts to three companies, each ofwhich was paired with a launch service provider. Theteams were tasked with analyzing the feasibility of the project, anddesigning their own versions ofthe launcher.

"During Phase 1 ofthe XS-1 program, the space industry has evolved rapidly and weintend to take advantage of multiple impressive technological andcommercial advances," states Jess Sponable, program manager for theXS-1. "We intend to leverage those advances along with our Phase 1progress to break the cycle of escalating DoD space system launchcosts, catalyze lower-cost satellite architectures, and prove thatroutine and responsive access to space can be achieved at costs anorder of magnitude lower than with today's systems."

Phase 2 will integratestate-of-the-art technologies in combination with the advances madein Phase 1 of the program to design and fabricate a functioninglauncher roughly the size of a conventional business jet. Whereasmultiple contracts were offered in the first stage of the program,DARPA only envisions awarding a single commitment in Phase 2.

The second stage of theinitiative will have four primary technical goals.

Fly 10 times in a 10-day period (not including weather, range and emergency delays) to demonstrate aircraft-like access to space and eliminate concerns about the cost-effectiveness and reliability of reusable launch.

Achieve flight velocity sufficiently high to enable use of a small (and therefore low-cost) expendable upper stage.

Launch a 900 to 1,500-lb (408 to 680-kg) representative payload to demonstrate an immediate responsive launch capability able to support both DoD and commercial missions. The same XS-1 vehicle could eventually also launch future 3,000+-lb (1,361-kg) payloads by using a larger expendable upper stage.

Reduce the cost of access to space for 3,000+-lb payloads, with a goal of approximately $5 million per flight for the operational system, which would include a reusable booster and expendable upper stage(s).

According to DARPA thefinal design will make use of advanced heat-resistant materials,cryogenic tanks and modular subsystems that will combine to lower thecost and reduce downtime. Conventional rocket-based launch providerscan only offer a limited number of launch slots each year, and thelaunches are booked years before the launch time.

Even the Ariane 6,Airbus Safron Launchers' next-generation rocket, will offer only 12launches per year. Employing a reusable spaceplane has the potentialto provide cheaper, more flexible access to LEO. Beyond finding itsuses in the commercial sphere, the XS-1 project will be used toassure American military satellites can be launched more frequently.

Source: DARPA