Madsen Pirie

Dream Chaser, the spacecraft from Sierra Nevada Corporation, is being prepared for its test flights, Wired tells us.  This is one of three private sector competitors attempting to win NASA contracts to ferry astronauts to the International Space Station.  The entries from Boeing and SpaceX are both based on capsules, recalling the early days of the Mercury, Gemini and Apollo programmes.  Dream Chaser, by contrast, is more similar in concept to the Space Shuttle orbiters in that it will land on a runway.  There is a crucial difference, though, in that Dream Chaser is a lifting body, deriving its lift within the atmosphere from the shape of its body, rather than relying on wings as the Space Shuttle did.  Its hybrid rocket motors burn hydroxyl-terminated polybutadiene (HTBP) and nitrous oxide and can be stopped and restarted, unlike solid fuel rockets. Importantly, its reaction control systems use ethanol-based fuel, which is not explosively volatile, enabling the craft to be handled immediately after landing.  Its ablative thermal protection system is designed to be replaced in large groups, rather than laboriously tile by tile, and then only after several flights.  It will launch into space vertically atop a well-proven Atlas V rocket.

Given that NASA is likely to award two contracts in 2017 for man-carrying vehicles, there is a possibility that it will select one of the two capsule entries and award the other to Dream Chaser, thus covering two separate and very distinct concepts.

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