October 30, 2013
Credit: Guy Norris
LOS ANGELES — Sierra Nevada is investigating the cause of a landing gear problem that forced the autonomous Dream Chaser engineering test article to veer off the runway on Oct. 26 at NASA’s Dryden Flight Research Center at Edwards AFB, Calif., during roll out after an otherwise “perfect” first free flight drop test.
The approach and landing test (ALT) was a key milestone event for the developers of the lifting body space vehicle, which is competing against conventional capsule designs proposed by Boeing and SpaceX for NASA’s commercial crew program.
For the test the Dream Chaser was lifted by a Sikorsky S-64 leased from Erikson Air-Crane to a launch altitude of 12,500 ft. At 11:10 a.m. Pacific time, the test team “performed a release which went perfectly,” says Sierra Nevada Space System’s Vice President Mark Sirangelo. “The flight lasted about a minute and it went perfectly right up until the end,” he adds.
Following release from overhead the dry lakebed and guided by its fully autonomous flight control system, the vehicle nosed down 50 deg. and glided for a straight in approach to runway 22L.
“The approach and landing worked as designed, the vehicle landed right on the centerline at the targeted touchdown speed of 160 knots at a descent rate of 1.5 feet per minute. It met all the test conditions,” says Sirangelo. The flight aspect was “an unqualified success” and represented the first free flight demonstration of a lifting body design based primarily on NASA’s HL-20, he says.
The landing gear, which consists of two main wheeled undercarriage legs and a single nose skid, was commanded to deploy as planned by the radar altimeter a few hundred feet off the ground, according to Sirangelo. However, the left main gear did not deploy correctly and, although the automated systems attempted to maintain a course down the runway, the Dream Chaser skidded off the runway and sustained damage. “It was not a great ending,” Sirangelo acknowledges, “but the main gear was borrowed from an F-5 and is not the planned gear.” Although the cause remains under investigation, he adds that “at this point it looks like one of the gear doors didn’t open properly. Although the vehicle was damaged, it is reparable and will likely fly again.”
However, it remains undecided whether a second free-flight glide test will be conducted, as was originally planned.
After the ALT series, Sierra plans to refurbish the Dream Chaser for a series of piloted flight tests that will involve towing the vehicle to higher release altitudes, possibly behind a C-17. The atmospheric test work is intended to clear the vehicle’s flight envelope prior to exo-atmospheric tests with an orbital flight test vehicle currently under construction for Sierra Nevada by Lockheed Martin. For operations to the International Space Station, the Dream Chaser is capable of carrying seven astronauts to orbit and has been designed to launch from Cape Canaveral atop a United Launch Alliance Atlas V 402.
While Sierra Nevada and NASA collected “a huge amount of data” about the flight test, Sirangelo adds the runway mishap also provided information about the Dream Chaser itself. “We learned how tough the vehicle was. After it came to a standstill I entered it and found the interior was pristine,” he says.