CAPE CANAVERAL, Fla. — NASA’s quest for a rocket upper stage to boost its Orion deep-space capsule beyond low Earth orbit in test flights opens the door for an alternative human space launch capability that could impact the fledgling efforts to develop commercial passenger spaceships.

The agency issued a Jan. 9 call for sources of an Interim Cryogenic Propulsion Stage (ICPS) to be used during two demonstration flights of the Orion Multi-Purpose Crew Vehicle, designed to travel to destinations beyond the international space station’s orbit.

The first launch, slated for December 2017, would be unmanned, but the second, scheduled for 2021, would include astronauts. Both would likely entail test flights around the Moon.

“The real purpose of this solicitation is for us to look at available potential commercial in-space stages and evaluate those not only from a technical standpoint, but from a cost and schedule standpoint. The purpose is to go out to industry and say, ‘Hey, here’s what we’re trying to do. We know there are several stages out there, and can they meet these requirements?’” David Beaman, manager of the Space Launch System spacecraft and payload integration office at NASA’s Marshall Space Flight Center in Huntsville, Ala., told Space News.

Responses to the announcement are due Feb. 7. The agency plans to follow up its request for sources with a solicitation for proposals by Sept. 30, Beaman added.

NASA wants the first motor delivered to Kennedy Space Center, Fla., in 2016 and the second, which would have to meet human-rating requirements, four years later, the ICPS Sources Sought Solicitation shows.

The stages would fly on early versions of NASA’s planned Space Launch System, or SLS, a heavy-lift vehicle derived from space shuttle components. Purchased commercially, the hardware also could potentially be used on passenger-carrying systems for other programs, such as NASA’s Commercial Crew Program, which is focused on low Earth orbiting systems.

“We human-rate the system, not the specific elements of the system and so what we start with is a process that attempts to understand deeply what went into the design,” SLS chief engineer Garry Lyles said. “We’ll understand what standards they used to design to. We’ll understand what loads and capabilities are within the design, as demonstrated by the applications that they’ve used it for, and then we will fly it analytically on the SLS launch vehicle and apply the SLS loads and environments to that stage. We’ll look at the failure modes analysis that go with that stage, and understand those. We’ll look at how much redundancy it might have in some areas and what [are] the real probabilities of failures, and we will assess the whole vehicle as a human-rated system.

“Until we have the design data to be able to do that, I can’t estimate how big a job it’s going to be.”

United Launch Alliance, the Denver-based manufacturer of the Atlas 5 and Delta 4 unmanned rockets, already has an unfunded partnership with NASA to human-rate its two-stage Atlas 5 rocket.

Three of the four firms NASA is financially backing for development of commercial space taxis to low Earth orbit plan are using Atlas 5 launchers. The fourth firm, Space Exploration Technologies, or SpaceX, has its own Falcon 9 rocket, a two-stage launcher powered by liquid oxygen and kerosene Merlin engines. Lockheed Martin, meanwhile, plans to use Delta 4 for an unmanned Orion test launch targeted for 2014 (see related story, page 16).

ULA spokeswoman Jessica Rye said the company currently is not working on human-rating the Delta 4, but that the process would be similar to what already is under way in the Atlas program.

The Delta 4 flies with a Pratt & Whitney Rocketdyne RL-10B2 upper-stage engine that is slightly more powerful than the RL-10 variant that powers Atlas 5’s Centaur upper stage, and fits within the technical requirements outlined by the NASA solicitation.

“We’re not sure exactly what’s out there,” Lyles said. “It’s possible that we will have to make some modifications to anything that’s out there. How much, is the main question.”

NASA still intends to develop the J-2X as the second stage for operational SLS flights.

“We’re looking for a relatively small stage. Our initial launch vehicle capability is nominally 70 tons to a low Earth orbit. That gives us the potential ability to do beyond low Earth with the Orion crew vehicle with a relatively small stage and demonstrate the Orion in-space capability,” Lyles said.

“We think there’s potential stages out there that we can use without developing the big stage first, and then we will eventually evolve our in-space capability to do the complete exploration missions,” he said.

A commercially available, human-rated upper stage also presents the possibility of an alternative architecture for deep-space exploration.

“The human missions tend to be heavy missions and just doing a lunar mission takes a lot of energy to do it. We might find a stage that big, but we don’t know of one that’s out there. We’ll take a look at what we’ve got and evaluate what its applicability is to any future missions,” Lyles said.

For the first Orion test flight, NASA is looking to do a lunar flyby.

“That gives them an Earth-re-entry velocity that allows them to test the spacecraft,” Lyles said. “For the crewed mission, we’re thinking of possible high lunar orbit mission to provide some in-space time for the crew in the spacecraft to check out all of their deep space systems.”

SpaceX chief Elon Musk, for one, isn’t worried that NASA’s Orion test program will eat into efforts to develop commercial transportation systems to fly astronauts to and from the space station.

“I think this is really aimed at some variant of the (Atlas 5) Centaur upper-stage,” Musk wrote in an email to Space News. “I don’t think this affects the Commercial Crew program in any way.”