SpaceX has carried outa successful test of its Launch Abort System (LAS) for the CrewDragon spacecraft. The test, which took place at Space Launch Complex40 of the Cape Canaveral Air Force Station represents a major stoptowards getting the spacecraft human rated under the Commercial CrewTransportation Capability (CCtCap) contract. NASA hopes thatcommercial spacecraft such as the Crew Dragon will return mannedspacecraft launches back to American soil sometime in 2017.
An operational LAS is avital safety element for any manned spacecraft. In use since theearliest days of human spaceflight, an LAS is designed tocarry the command capsule and the astronauts contained within safelyout of harm's way should there be a failure of the launch vehicleeither on the pad, or early in the ascent phase.
Unlike previousiterations of escape systems such as those used over the course ofthe Apollo missions and the system being designed for Boeing's rivalCST-100 spacecraft, the Crew Dragon LAS does not take theform of a rocket tower. A rocket tower escape system is designed tosit atop a spacecraft and fire in the case of an emergency, liftingthe capsule away from the launch vehicle. In the case of NASA's Orionspacecraft and CST-100, the LAS completely covers the commandcapsule.
Whilst therocket tower represents the traditional and proven approach to LASdesign, it also poses a potential threat to the safety of the crew.For example, if during the Orion spacecraft's maiden flight inDecember last year the LAS had failed to separate from the commandcapsule, it would have rendered the spacecraft's parachute systemredundant. If such a fault were to occur during a manned flight, itwould likely result in the deaths of the entire crew upon re-entry.
SpaceX has decided toeschew the traditional rocket tower in the design of the Crew Dragonspacecraft. Instead, the next generation spacecraft's escape systemcomes in the form of eight SuperDraco engines integratedinto the walls of the spacecraft itself, each of which is capable ofoutputting 15,000 lb (6,804 kg) of thrust.
The new systemsatisfies the requirements of the CCtCAP while posing a reduced riskto the crew should there be a malfunction. Furthermore, whilst therocket tower design is only operative for the first few minutesfollowing a launch, the Crew Dragon system can be used at any timebefore the spacecraft reaches orbit.
The pad abort test sawthe Crew Dragon spacecraft and trunk launched 5,000 ft (1,524 m) intothe air by its SuperDraco boosters, which over the course of a 6-second burn produced an impressive 120,000 lb (5,4431 kg) of thrust. Thecapsule had been fitted with 270 sensors, as well as a human dummy, also rigged with sensors, which the SpaceX technicians have lovingly named "Buster."
"There’s a lotof instrumentation on this flight – a lot," states HansKoenigsmann, vice president of Mission Assurance with SpaceX."Temperature sensors on the outside,acoustic sensors, microphones. This is basically a flyinginstrumentation deck. At the end of the day, that’s the point oftests, to get lots of data."
Upon reaching itsapogee, the spacecraft jettisoned its trunk, and soon after deployedtwo drogue parachutes, followed by three main chutes, under which theDragon gently splashed down in the Atlantic Ocean.
With the trialcomplete, the spacecraft will be transported to McGregor, Texas, whereSpaceX scientists will comb through the telemetry collected by thearmy of sensors installed aboard the Crew Dragon, and refurbish thecapsule for use in further flight tests.
For those hoping tocatch a replay of Buster's traumatic journey, you can check out thevideo of the LAS test below.
Source: NASA
