Commercial crew candidate may clear milestone despite landing-gear failure
A last-minute mechanical failure that sent the Dream Chaser atmospheric test article skidding into the desert sand at Edwards AFB, Calif., with one wheel up may not disqualify . from collecting its final $8 million milestone payment under a Commercial Crew Development (CCDev) Space Act agreement.
Mark Sirangelo, who heads the Colorado company's space unit, says the lifting-body spaceplane prototype generated almost all the data expected during a 1-min. drop test from 12,500 ft., including the g-loading at touchdown that is a selling point for returning delicate scientific samples or injured space station crew to the runway landing unavailable to capsules.
“We actually were tracking about 30 different elements of the flight,” he says. “The g-loads were expected to be below 2, and they were below 2.”
will schedule a review session soon to determine if the drop test generated enough data to meet its milestone requirement in the second round of CCDev work, which would close out Sierra Nevada's $80 million CCDev 2 agreement. Overall, the company has won $125 million in NASA seed money for Dream Chaser development, and has invested a comparable amount of its own funds, according to Sirangelo (AW&ST July 2, 2012, p. 37).
“NASA was very pleased with the flight portion of Saturday's test of the Dream Chaser test article,” says Phil McAlister, director of commercial spaceflight development. “The vehicle performed very well and Sierra Nevada will have lots of test data to use for its future development effort. The anomaly experienced during the landing was unfortunate. However, NASA is confident that Sierra Nevada will learn from this test and continue to meet its remaining milestones.”
Sirangelo says the company is investigating the landing-gear issue that forced the autonomous engineering test article to veer off the runway Oct. 26 during rollout after an otherwise “perfect” first free-flight drop test.
The approach and landing test was a key milestone for the developers of the space vehicle. Based on NASA's old HL-20 lifting body, the Dream Chaser prototype is competing against conventional capsule designs byand for NASA's commercial program to deliver crew to the International Space Station. For the test, a S-64, leased from Erikson Air-Crane, lifted the test article to a launch altitude of 12,500 ft., and performed a drop “which went perfectly,” says Sirangelo.
“The flight lasted about a minute and it went perfectly right up until the end,” he adds.
Following release above the dry lake bed at Edwards, and guided by its fully autonomous flight-control system, the vehicle nosed down 50 deg., then flared up 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 kt., at a descent rate of 1.5 feet per minute,” Sirangelo says.
The flight aspect was “an unqualified success” and represented the first free-flight demonstration of a full-scale lifting-body design based primarily on NASA's HL-20.
Flight software commanded the landing gear, which consists of two main wheeled undercarriage legs and a single nose skid, to deploy as planned on cue from the spacecraft's radar altimeter “a couple of hundred feet off the ground.” However, the left main gear did not deploy correctly and while the automated systems attempted to maintain a course down the runway, the Dream Chaser skidded off the runway and sustained damage to the simulated thermal protection system that covered its composite pressure shell. The vehicle wound up upright off the runway with its deployed tire intact, although it was not clear if the vehicle had rolled over before that “because there was a lot of dust,” Sirangelo explains.
“It was not a great ending,” he acknowledges, “but the main gear was borrowed from an F-5 and is not the planned gear. . . . 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.”
Sirangelo says Sierra Nevada and NASA safety experts examined the Dream Chaser cabin shortly after the hard landing and deemed it and the vehicle's flight computers and other systems undamaged. If the data from the Oct. 26 test satisfies NASA and Sierra Nevada's engineers, it may be possible to skip a second autonomous drop test and move directly into piloted flight following repairs.
The piloted flight-test series will involve towing the vehicle to higher release altitudes, possibly behind a. The atmospheric test work next year is intended to clear the vehicle's flight envelope prior to an unpiloted orbital test in 2016, and a piloted flight to the ISS in 2017. is building an orbital-flight vehicle for Sierra Nevada at NASA's Michoud Assembly Facility.
For operations to the ISS, the Dream Chaser can carry seven astronauts, launching initially from Cape Canaveral AFS atop a United Launch Alliance Atlas V 402, although Sirangelo says his company is “agnostic” about its choice of launcher for the future. The fully autonomous orbital lifting body will be able to deliver cargo without a crew on board, perform satellite-servicing and other free-flying missions, and serve as a rescue vehicle for an expanded station crew, Sirangelo notes.
In a statement applauding the drop test, the Commercial Spaceflight Federation noted that the Dream Chaser landed on the same runway used by Enterprise, the atmospheric test article for NASA's space shuttle.
“We view Dream Chaser as being in a very similar position as the shuttle in its development, and this vehicle, for all practical purposes, is our version of Enterprise,” says Sirangelo. “It was really meant to fly just a few times to provide a lot of aero data, control data, understandings of how the vehicle would enter an approach, and really to understand the technical side of the vehicle design.”
Watch video of the Dream Chaser prototype's first flight on our OnSpace blog at: ow.ly/qkPuT