Boeing XS-1 Experimental Spaceplane artist concept

PHOENIX — The U.S. Defense Advanced Research Projects Agency is moving ahead to the next phase of an experimental reusable spaceplane program, but the agency’s expectation that the winning bidder shoulder some of the costs could cause some companies to reconsider participating.

DARPA announced April 7 that it was moving ahead to phase 2 of its Experimental Spaceplane 1 (XS-1) program, an effort to develop a prototype of a reusable first stage that, when combined with an expendable upper stage, could launch small and medium-sized satellites for less than $5 million.

DARPA awarded three phase 1 study contracts in 2014 to Boeing, Masten Space Systems and Northrop Grumman. Those study efforts are nearing completion, said Jess Sponable, DARPA XS-1 program manager, in a presentation April 7 at the Space Access ’16 conference here.

Under phase 2, DARPA will select one company to continue development of their design and perform a series of flight tests. “We have a funded flight demonstration and experimental program for the next phase of the XS-1 program,” he said.

DARPA has scheduled an industry day for phase 2 of the XS-1 program for April 29 at its Arlington, Virginia, headquarters. That will be followed by a formal solicitation in early May, Sponable said, with DARPA making an award early in fiscal year 2017.

The winning company will be responsible for developing a vehicle that can fly 10 times in 10 days, demonstrating reliable and cost-effective reusability. On at least one test flight the vehicle would carry an upper stage to launch a “representative payload” weighing between 400 and 680 kilograms, with the ability to later accommodate payloads weighing at least 1,350 kilograms. Those test flights would take place by 2020.

Phase 2 of XS-1 will be open to any bidder, and not just the three companies who participated in phase 1, Sponable said. “We felt the market was dynamic enough that we should not limit ourselves to three contractors,” he said, citing efforts by Blue Origin and SpaceX to develop reusable vehicles.

He added, though, that it will be more difficult for companies not involved in the initial phase of XS-1 to be competitive in phase 2. “We are looking for a level of detail in the response that will make it very difficult for some people to come in on the fly and respond,” he said.

Another factor that could affect who bids on phase 2 is funding. DARPA is planning to spend about $140 million on the development and flight tests of the vehicle. “That’s enough to pick someone and go,” Sponable said. “It’s probably not enough to fully fund what we have envisioned.”

DARPA plans to use its other transactional authority to contract with the winning company. “That implies cost-sharing,” he said, with that company contributing the additional funding above DARPA’s $140 million to carry out the program.

Sponable said he believes the current XS-1 contractors, and others who might decide to compete for phase 2, understand they’ll be expected to contribute to the program. But one company involved in phase 1 says they’re still weighing their options for competing for phase 2.

“For participation, we’re assessing the appropriateness of what Boeing might do,” said Craig Cooning, president of Boeing Network and Space Systems, during a media roundtable April 12 at the 32nd Space Symposium in Colorado Springs, Colorado.

“There was always going to be company participation, but the amount of company participation will be a little different” because the funding for phase 2 is less than what was previously expected, said Alex Lopez, vice president for global sales and marketing at Boeing Network and Space Systems.

Lopez suggested Boeing might ask DARPA to change some of the requirements to reflect that reduced funding. “One way or another we’re going to go forward with this program, but we’re working closely with DARPA to work on the expectations for the next phase.”

Sponable said that, despite ongoing reusable launch vehicle development efforts in the private sector, XS-1 was still relevant, in part because of its high flight rate. “We think flying 10 times in 10 days is something well outside the capability of either SpaceX or Blue Origin at this time,” he said. “We hope to spur them along and get them to think about how they can increase their flight rates.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...