Sierra Nevada Corp. will use folding wings and a pressurized/unpressurized “cargo trailer” with the Dream Chaser Cargo System it has entered in NASA’s second-round competition for unmanned vehicles to deliver cargo to the International Space Station (ISS).

The autonomous vehicle, a modification of the piloted vehicle the company proposed unsuccessfully for NASA’s commercial crew competition, would be able to launch on a United Launch Alliance (ULA) Atlas V as originally planned, or on Europe’s Ariane 5 initially.

Later it could also fly on the ULA Delta IV, Japan’s H-IIB or H-III launch vehicles, and perhaps on the SpaceX Falcon 9.

The lifting-body spaceplane’s wings would be folded in to fit within a standard Ruag 5-meter fairing for launch. Riding behind the windowless lifting body would be a smaller cargo module designed to carry both pressurized cargo and unpressurized payloads on three off-the-shelf Teledyne Brown Engineering Flight Releasable Attachment Mechanisms (Frams), according to Mark Sirangelo, head of the company’s Space Systems unit and a corporate vice president.

With the seats and other crew accommodation removed from the main vehicle, and a hatch between that pressurized cabin and the added cargo unit, the vehicle would be able to exceed all of the cargo-carrying requirements NASA set in its request for proposals for both pressurized and unpressurized cargo, including cargo return to a runway landing on Earth in the lifting body and ISS trash stowed in the separate cargo module for destructive re-entry.

The cargo-trailer unit would also carry solar arrays originally developed for the Orbcomm Generation-2 spacecraft Sierra Nevada builds, allowing the module to loiter in orbit for more than 10 days without station power, and for “months” if docked.

Reflecting its heritage as a crew vehicle, the cargo system would dock at a station pressurized mating adapter, and could provide station reboost from the position, according to Steve Lindsey, a former space shuttle commander who is the company’s senior director for space exploration systems.

The vehicle would dock autonomously with the space station, using flight-control software developed for the crew version. Sierra Nevada is completing work on its crew vehicle under an earlier NASA Space Act agreement, and would use much of the equipment developed for that purpose in the cargo variant.

The vehicle has a “unique” ability to return cargo from the ISS to a 1.5-g runway landing, Lindsey said. Because it doesn’t carry toxic hypergolic fuels, it can be unloaded very soon after landing, an advantage for delicate scientific samples and other payloads that need rapid attention on the ground.

“We believe that at the end of the day having a lifting-body vehicle in the fleet of capabilities for space is something that NASA will continue to see as a valuable benefit, and to their credit they continue to encourage us to do so,” Sirangelo said.

Editor's note: The SpaceX system was corrected to Falcon 9.