Sierra Nevada Details Drop Plan For Dream Chaser

LOS ANGELES —Bolstered by its recent second-round NASA Commercial Crew
Development Program (CCDev2) win to continue development of the Dream Chaser
spaceship, Sierra Nevada Corp. is revealing new details of its plan to conduct
full-scale drop tests in 2012 using the Scaled Composites-developed
WhiteKnightTwo mothership.

Sierra Nevada is one of the big winners in the second round of NASA’s CCDev
program, netting $80 million of the total $269.3 million payout aimed at
maturing concepts for private spacecraft to carry astronauts to the
International Space Station and other low Earth orbit destinations. Designed for
a maximum crew of seven, the Dream Chaser is a lifting body spacecraft based on
NASA’s HL-20 crew vehicle, and will launch on an Atlas V.

The atmospheric drop test of the full-scale vehicle, expected sometime in the
second quarter of 2012, will asses handling qualities as well as stability and
control during an unpowered descent to a conventional runway landing. The design
of the low-speed flight control system is being fine-tuned after drop tests of a
scale model were conducted in December at NASA Dryden Flight Research Center
from a helicopter hovering over the dry lakebed at Edwards AFB, Calif.

Preparations for firming up the drop test from WhiteKnightTwo, which will
take place from an altitude of 45,000 ft., follow last December’s announcement
that Virgin Galactic is supporting the Dream Chaser development. Virgin Galactic
also was included in Sierra Nevada’s CCDev2 proposal. The large, four-engined
carrier aircraft is in development for Virgin’s SpaceShipTwo sub-orbital space
tourism and science vehicle, but is being actively marketed for a range of other
“mothership” drop test roles.

New details of the Dream Chaser were revealed by Sierra Nevada Space Systems
Group at the recent American Institute of Aeronautics and Astronautics Space
Planes and Hypersonics conference in San Francisco. Integrated product team lead
Russ Howard says the vehicle’s hybrid rocket motor is undergoing further
development work following testing for CCDev, which included three static
firings in one day. “This included one vacuum start and a demonstration of a new
pressure feed system,” he says.

The rocket, fueled by a combination of hydroxyl-terminated polybutadiene
(HTPB) and nitrous oxide, is designed “for flexibility, as it can be stopped,
re-started and throttled to 100% for launch abort/escape, or 50% for fine
control in nominal maneuvers. We’re planning to throttle down as low as 50%, but
we have demonstrated thrust down to 30% and its been very stable,” Howard

The Dream Chaser is expected to have a cross-range capability of 1,700 km
(1,000 mi.) and with a subsonic lift/drag ratio of 4:0, a “landing will be
feasible on 7,000-foot runways,” he says. However, with launches currently
planned from Kennedy Space Center’s SLC-41 launch pad (and possibly SLC-39B
after conversion), the primary landing site is Cape Canaveral’s 15,000-ft. main

Beyond atmospheric drop tests, further development plans include an
un-piloted orbital test flight (OFT-1) boosted by an Atlas V, followed by a
crewed OFT-2. The system is aiming for initial operational capability in 2015.


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