“We have plans to do a pad abort test in the coming months,” Sirangelo says. “Our vehicle has no black zones right now for abort from launch to orbit, and we can abort to a runway anywhere along the way. . . . None of the three of us has done any abort tests so far, and we need to all do that. We have that planned to retire that risk, not as one of the milestones but as work that we're doing separately.”
Those hybrid engines, also mentioned in the source-selection document as a technical risk, are based on the rockets that powered the Scaled Composites SpaceShipOne in its successful bid for the $10 million Ansari X Prize, and those planned for Virgin Galactic's SpaceShipTwo suborbital vehicle. Sirangelo says the Dream Chaser versions have been test-fired and restarted, including in vacuum, and should have no problem meeting the test-fire milestones in the CCiCap plan.
Despite the lower NASA funding, Sierra Nevada plans to go ahead with its bid to fly NASA astronauts to the International Space Station, starting before the end of the year with an autonomous drop test and landing with a full-scale engineering article that has already undergone captive-carry tests. Ultimately, Sirangelo and his corporate colleagues believe, the capabilities of their vehicle will outweigh today's risks.
“With the hybrid motors, if we don't use them on abort, they give us a tremendous capability to fly on orbit,” he says. “So we can actually go up to several hundred miles above the space station and do work. That's a really robust capability that allows us to consider potential servicing missions for things for NASA for other purposes, and to use the vehicle for other purposes.”
Also on the list of potential advantages of the Dream Chaser over the Boeing and SpaceX capsules is the high level of reuse Sierra Nevada expects from each vehicle—25-30 missions each, according to Sirangelo. The optimistic outlook for the Dream Chaser's commercial potential is shared by Gerstenmaier and the CCiCap source-selection board that advised him.
“These significant technical advantages could result in a larger customer base for [Sierra Nevada] than a capsule design and more capability for users,” Gerstenmaier writes.