Crew Dragon Launch Abort System
Crew Dragon Launch Abort System
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Crew Dragon Launch Abort System

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Crew Dragon Launch Abort System

The Crew Dragon Launch Abort System is designed to propel the SpaceX Crew Dragon spacecraft away from a failing launch vehicle. It is equipped with 8 SuperDraco engines, each capable of generating 71 kN of thrust.

The abort system has several modes, or procedures for performing an abort in different phases of flight, including a pad abort, an in-flight abort, and the ability to use the abort system to fly into a lower than expected orbit should a failure occur late in flight.

Traditionally, spacecraft like Apollo and Soyuz have utilized solid-fueled "puller" launch escape systems, with the main spacecraft beneath a protective fairing attached to the escape system. Once in space, the escape system and the fairing are jettisoned, with the spacecraft's mode of abort switched to using its orbital maneuvering thrusters or upper stages. Crew Dragon, however, has its abort system permanently attached to the sides of the spacecraft.

Part of the reasoning behind this design is that it was originally planned to land dragon propulsively using the launch abort system. These plans were dropped after skepticism from NASA and the cancellation of SpaceX's Red Dragon capsule. However, the capability was introduced on Crew-8, though only in the event of a parachute failure. Additionally, the ability to keep the abort system attached to the rocket throughout the entire ascent rather than jettisoning the launch escape system after stage separation allows for an abort capability in all stages of flight, increasing crew safety.

Crew Dragon's "trunk", or cargo bay, also plays an important role in the abort sequence. Rather than leaving the trunk with the rocket like Apollo or Soyuz, Dragon keeps the trunk attached during an abort for aerodynamic stability.

On 20 April 2019, Crew Dragon C204 was destroyed in an incident while testing its SuperDraco engines. A video leaked shortly after the incident shows the capsule exploding on a launch mount. NASA and SpaceX confirmed the explosion and stated that there were no injuries.

Following an investigation, SpaceX stated that the explosion was the result of a faulty valve. During a nominal ignition sequence, valves keeping helium inside COPVs (Composite Overwrapped Pressure Vessels) are opened, causing the helium to flow through one-way check valves into the propellant tanks, pushing the fuel into the combustion chamber.

In this incident, however, the one-way oxidizer valve had allowed nitrogen tetroxide (NTO) to leak back through the helium tube. When the helium valve was opened, the "blobs" of NTO inside the helium line were accelerated at high speeds, slamming into and nearly instantaneously destroying the one-way oxidizer valve. The internal titanium components of the destroyed valve were then exposed to the NTO, resulting in combustion and the loss of the vehicle.

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