WASHINGTON — Sierra Nevada Corp., looking to rebound from a failed commercial crew bid, said March 17 it has proposed to NASA a variant of its Dream Chaser vehicle for shuttling cargo to and from the International Space Station.

At a press conference during the Satellite 2015 conference here, company officials offered details of its Dream Chaser Cargo System, based on the Dream Chaser vehicle the company had been developing for NASA’s commercial crew program.

“We believe that it’s the best cargo system that currently exists or will exist, because it’s capable of meeting all of NASA’s cargo requirements in the same system,” said Mark Sirangelo, corporate vice president and head of Sierra Nevada Space Systems.

The cargo version of Dream Chaser features two major design changes from its crew version. Sierra Nevada plans to develop a small cargo module attached to the aft section of the winged vehicle. This cargo module, equipped with solar panels, will accommodate both internal and external cargo.

Mark Sirangelo, head of Sierra Nevada Space Systems, discusses the company’s Dream Chaser cargo vehicle at a press conference in Washington on March 17. On the podium is a model of the vehicle. Credit: SpaceNews photo by Jeff Foust
Mark Sirangelo, head of Sierra Nevada Space Systems, discusses the company’s Dream Chaser cargo vehicle at a press conference in Washington on March 17. On the podium is a model of the vehicle. Credit: SpaceNews photo by Jeff Foust

The Dream Chaser’s wings will also be able to fold up for launch. This allows the vehicle to fit within payload fairings 5 meters in diameter currently used by the Atlas 5 and Ariane 5 launch vehicles. The crewed version of Dream Chaser, by comparison, was not designed to be encapsulated in a fairing and thus did not need foldable wings.

This vehicle, company officials said, meets or exceeds all the requirements NASA laid out for the Commercial Resupply Services 2 (CRS-2) competition for transporting cargo to and from the ISS. The vehicle can transport 5,000 kilograms of pressurized cargo and 500 kilograms of unpressurized cargo to the station. It can bring back 1,750 kilograms of cargo within Dream Chaser, and dispose of an additional 3,250 kilograms in the cargo module, which jettisons and burns up on re-entry.

“There’s an important sweet spot in the amount of cargo you can bring up to the space station as well as return,” said Steve Lindsey, senior director of space exploration systems at Sierra Nevada. Cargo vehicles, he said, should be large enough to minimize the number of flights needed to keep the station supplied, but not so large they are difficult to operate. “We think we’ve hit that.”

Sierra Nevada also hopes to convince NASA that Dream Chaser’s unique design — it is the only vehicle competing for the CRS-2 contracts that can land on a runway — makes the system worthwhile. “There are many capsules in the world, but there’s really one vehicle like Dream Chaser,” Sirangelo said. “We believe in a mixed fleet.”

The CRS-2 competition is a fallback for Sierra Nevada after it lost to Boeing and SpaceX for commercial crew contracts NASA awarded in September 2014. The company filed a protest with the U.S. Government Accountability Office regarding those contracts, but that protest was denied in January.

Sirangelo said that the cargo version of Dream Chaser benefits from several months of additional work the company did between the deadlines for the commercial crew proposals in January 2014 and the CRS-2 proposals in December. “We have continued to improve the vehicle,” he said. “The areas that were of concern we have addressed.”

While developing the cargo version of Dream Chaser, Sirangelo said that the company has not abandoned plans for a crew version. “While we’re leaning forward on the cargo autonomous version here, everything that we’re doing in this vehicle is transferable to a future crew vehicle,” he said.

Although Sierra Nevada lost the NASA commercial crew competition, it is still working toward the final milestone of its earlier commercial crew award from NASA, a second glide test of a Dream Chaser engineering test vehicle. That glide test is planned for later this year, Sirangelo said.

Sierra Nevada joins at least four other companies in the CRS-2 competition. On March 12, Lockheed Martin announced it submitted a CRS-2 proposal, offering a system that includes a reusable space tug. Boeing and Orbital ATK said in December that they also submitted CRS-2 bids.

SpaceX, which, like Orbital ATK, has contracts today to transport ISS cargo, had previously declined to confirm that they also bid on CRS-2. However, SpaceX President Gwynne Shotwell, speaking at a luncheon at the conference March 17, tipped the company’s hand.

“Oh, most definitely,” she said when asked if the company bid on CRS-2. That proposal involves the use of SpaceX’s Dragon spacecraft, but Shotwell did not provide additional details.

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...