Sierra Nevada’s Dream Chaser Met Milestones for 2010

SNC Dream Chaser Pressure Shell. (Credit: Sierra Nevada Corporation)

A Private Space Shuttle Replacement
Technology Review

The company reached all its development milestones for the Dream Chaser last year and is now finishing a battery of tests on the craft’s carbon-composite frame. The shell of the spacecraft must be able to endure heavy loads and intense vibrations. So the Dream Chaser frame has been mounted on an earthquake simulator in a lab at the University of Colorado in Boulder. So far, the design has performed as expected, says Mark Sirangelo, head of Sierra Nevada’s Space Systems division. At facilities in San Diego, the company has been testing the craft’s hybrid rocket motors. In the coming months, the company will put the two together to complete a full prototype, carry it into the air, and drop it to see how it flies….

Sierra Nevada, which also makes satellites, sensors, and other components, did not design the Dream Chaser from the ground up. In the 1970s, the Soviets tested a vehicle like it, known as the Bor-4. The crew of an Australian ship photographed it, and NASA used the image to reverse-engineer a similar craft. The resulting design, NASA’s HL-20, underwent significant development and testing and was intended to be a lifeboat for astronauts aboard the space station. But the HL-20 program lapsed.

Six years ago, a small aerospace company that Sirangelo headed, called SpaceDev, licensed the design from NASA and began to modify it, for instance adding the hybrid motors. The motors burn an unusual fuel: a combination of recycled rubber and nitrous oxide. This has almost the same energy density as conventional fuel but can be burned in a more controlled way and thus might be safer, though only multiple flights can prove whether it is. Sirangelo compares the system to a burner on a gas stove that can be turned to a lower or higher flame. The same hybrid motor was used in SpaceShipOne, which won the X Prize in 2004, and will also be incorporated in Virgin Galactic’s SpaceShipTwo, intended to fly tourists into suborbital space….

Everything on the Dream Chaser except the initial launch booster and the fuel cartridges is designed to be reused. Still, turning a profit will require flying multiple Dream Chasers 50 to 100 times each, and Sirangelo admits that he doesn’t know when that will occur. “We’re entering an unknown world,” he says. The company isn’t disclosing exact figures, but Sierra Nevada, a profitable company founded in 1963, has invested tens of millions of dollars in the project—more than the company received from NASA this year. Sirangelo says Sierra Nevada plans to continue to invest own money in the project. “If we don’t get to our milestones, we don’t get paid,” says Sirangelo. The company has applied for a second round of funding from NASA that will be given out later this year.

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Editor’s Note: Yes, the fuels “might be safer,” although the nitrous oxide tank explosion at Scaled Composites in 2008 indicates that it might not be superior to liquid fuel systems. There’s a belief among some in the space community, which the author seems to believe, that hybrids are inherently safer due to their design. This is certainly a claim that Virgin Galactic has repeated endlessly for years despite the three engineers killed in the Mojave accident.

The fact that nitrous oxide can ignite on its own doesn’t provide much comfort here. It’s interesting that Virgin Galactic is now talking about using different fuel and oxidizer in SpaceShipTwo. The official explanation is that this makes the ship more green.