Dream Chaser test plan outlined by Sierra Nevada
BY STEPHEN CLARK
Posted: May 9, 2012
Sierra Nevada Corp., one of the firms vying to build a commercial space taxi for NASA, plans a series of automated and piloted atmospheric flight tests of its lifting body Dream Chaser spacecraft beginning this summer, ultimately leading to an orbital demonstration mission in 2016, according to company managers.
Using a combination of public and private funding, Sierra Nevada is developing the Dream Chaser to carry up to seven astronauts to the International Space Station and back to Earth. NASA has promised the company $125 million so far, with the bulk of the money already awarded to Sierra Nevada upon completion of predetermined development milestones.
"Our mission is very specific: to take crew and cargo to the International Space Station and to low Earth orbit," said Mark Sirangelo, Sierra Nevada's executive vice president and chairman of its space systems division.
Sierra Nevada has provided the Dream Chaser program with "tens of millions" of dollars in internal funding, but less than NASA's total investment, according to Sirangelo.
The remaining NASA funds will be released after the Dream Chaser's preliminary design review, scheduled for late May, and captive and free flight tests over Colorado and California.
"We've made amazing progress without a lot of money," Sirangelo said.
The Dream Chaser is based on the HL-20 lifting body concept studied by NASA's Langley Research Center from the late 1980s to the early 1990s. Launching into orbit on top of a United Launch Alliance Atlas 5 rocket, the spaceship will dock with the International Space Station and can stay there for more than six months. At the end of its mission, the craft will enter the atmosphere and make a piloted touchdown at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida.
"You want to work backwards in the space industry and make sure you can land before you take off," Sirangelo said.
Steve Lindsey, Sierra Nevada's director of flight operations, said the captive carry test would verify the Dream Chaser's stability hanging underneath a helicopter, check its hang angle, drogue parachutes, and test the Sky Crane's lift capability.
Lindsey, a former space shuttle commander, said the test vehicle will be returned to Sierra Nevada's factory to receive flight control systems and a main landing gear modified from the U.S. Air Force's F-5E Tiger fighter jet. Dream Chaser's nose gear is a custom-designed skid.
Dream Chaser's space missions will use a new landing gear with electric actuators, Lindsey said.
Sierra Nevada will ship the engineering article to Edwards Air Force Base, Calif., this summer for another series of captive carry tests before ultimately releasing the craft for an automated landing. According to Lindsey, the drop tests will be performed from a CH-53 Sea Stallion or CH-47 Chinook helicopter provided by the U.S. military.
"The drops will be a straight in approach from as high as we can get," Lindsey said. "I'm hoping about 17,000 feet or so, straight into the main runway at Edwards for approach and landing."
Lindsey said the plan is to land the Dream Chaser on Runway 22 at Edwards, the base's primary concrete landing strip used by the space shuttle.
"Part of the reason we're doing this testing is because we have so many aerodynamic uncertainties with the vehicle," Lindsey said. "The shuttle had a nominal 20-degree glideslope. We're about a 23-degree glideslope, so a little bit steeper. We'll fly 300 knots down on final [approach], just like the shuttle did, and do a preflare at 2,000 feet, just like the shuttle did, drop the gear at 200 or 300 feet, just like the shuttle, and touch it down roughly at 190 knots on the runway, just like the shuttle did."
Sierra Nevada has also constructed avionics and flight control laboratories, plus a Dream Chaser flight simulator to practice landing the spacecraft on a runway.
The free flight test, expected in late summer, is the last milestone Sierra Nevada must complete under its ongoing agreement with NASA. The firm proposed continuing Dream Chaser's development through at least May 2014 in NASA's next round of funding.
Beyond the free flight test this summer, Sierra Nevada says further flights are contingent upon winning a monetary award from NASA.
NASA expects to award multiple companies between $300 million and $500 million in August. The agreements will run for approximately 21 months, followed by an optional period in which the space agency could select a single provider to continue with flight testing and crew transportation services.
Sierra Nevada says it can build three to five Dream Chaser spacecraft to be based at the Kennedy Space Center. The company is seeking state incentives and agreements with NASA to acquire former shuttle infrastructure at the space center, officials announced last week.
Lindsey hopes to fly the Dream Chaser for manual landing tests as soon as 2014. The former shuttle astronaut could also pilot the spacecraft on its first test flight to orbit.
Testing of the Dream Chaser's suborbital vehicle will include firings of the ship's hybrid rocket motors. Two of the non-toxic motors, derived from Sierra Nevada designs used on the SpaceShipOne and SpaceShipTwo space tourism vehicles, will adjust the craft's orbit in space, return it to Earth, and propel the Dream Chaser away from danger during a launch mishap.
"We're going to have our hybrid motors on the [suborbital vehicle], and we're going to use the motors to accelerate us up into the supersonic regime to get data there," Lindsey said. "The last thing we do with that vehicle, when we're done with all the pilot-in-the-loop testing, is we're actually going to put it on a simulated Atlas 5 and do a pad abort to a runway landing autonomously."
An unmanned orbital test flight and a crewed mission into orbit will follow in 2015 and 2016, according to Sierra Nevada.