SpaceX has carried out a successful test of its Launch Abort System (LAS) for the Crew Dragon spacecraft. The test, which took place at Space Launch Complex 40 of the Cape Canaveral Air Force Station represents a major stop towards getting the spacecraft human rated under the Commercial Crew Transportation Capability (CCtCap) contract. NASA hopes that commercial spacecraft such as the Crew Dragon will return manned spacecraft launches back to American soil sometime in 2017.

An operational LAS is a vital safety element for any manned spacecraft. In use since the earliest days of human spaceflight, an LAS is designed to carry the command capsule and the astronauts contained within safely out of harm's way should there be a failure of the launch vehicle either on the pad, or early in the ascent phase.

Unlike previous iterations of escape systems such as those used over the course of the Apollo missions and the system being designed for Boeing's rival CST-100 spacecraft, the Crew Dragon LAS does not take the form of a rocket tower. A rocket tower escape system is designed to sit atop a spacecraft and fire in the case of an emergency, lifting the capsule away from the launch vehicle. In the case of NASA's Orion spacecraft and CST-100, the LAS completely covers the command capsule.

Whilst the rocket tower represents the traditional and proven approach to LAS design, it also poses a potential threat to the safety of the crew. For example, if during the Orion spacecraft's maiden flight in December last year the LAS had failed to separate from the command capsule, it would have rendered the spacecraft's parachute system redundant. If such a fault were to occur during a manned flight, it would likely result in the deaths of the entire crew upon re-entry.

SpaceX has decided to eschew the traditional rocket tower in the design of the Crew Dragon spacecraft. Instead, the next generation spacecraft's escape system comes in the form of eight SuperDraco engines integrated into the walls of the spacecraft itself, each of which is capable of outputting 15,000 lb (6,804 kg) of thrust.

The new system satisfies the requirements of the CCtCAP while posing a reduced risk to the crew should there be a malfunction. Furthermore, whilst the rocket tower design is only operative for the first few minutes following a launch, the Crew Dragon system can be used at any time before the spacecraft reaches orbit.

The pad abort test saw the Crew Dragon spacecraft and trunk launched 5,000 ft (1,524 m) into the 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. The capsule had been fitted with 270 sensors, as well as a human dummy, also rigged with sensors, which the SpaceX technicians have lovingly named "Buster."

The Crew Dragon capsule descending under three fully-deployed main parachutes (Photo: NASA, SpaceX)

"There’s a lot of instrumentation on this flight – a lot," states Hans Koenigsmann, vice president of Mission Assurance with SpaceX. "Temperature sensors on the outside, acoustic sensors, microphones. This is basically a flying instrumentation deck. At the end of the day, that’s the point of tests, to get lots of data."

Upon reaching its apogee, the spacecraft jettisoned its trunk, and soon after deployed two drogue parachutes, followed by three main chutes, under which the Dragon gently splashed down in the Atlantic Ocean.

With the trial complete, the spacecraft will be transported to McGregor, Texas, where SpaceX scientists will comb through the telemetry collected by the army of sensors installed aboard the Crew Dragon, and refurbish the capsule for use in further flight tests.

For those hoping to catch a replay of Buster's traumatic journey, you can check out the video of the LAS test below.

Source: NASA

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