SpaceX is investigating the possibility that a leaky valve caused its Crew Dragon spacecraft capsule to explode on a test stand at Cape Canaveral Air Force Station in Florida, US, in April.
SpaceX, which is aiming to send US astronauts to the International Space Station by the end of 2019, suffered a setback when it was carrying out static fire engine tests of the Crew Dragon In-Flight Abort test vehicle. The final test resulted in “destruction of the vehicle”, but no injuries were reported.
Preliminary findings of the accident investigation team indicate that a leaking component allowed liquid oxidiser – nitrogen tetroxide – to enter high-pressure helium tubes during ground processing.
Space X said in a statement: “A slug of this nitrogen tetroxide was driven through a helium check valve at high speed during rapid initialisation of the launch escape system, resulting in structural failure within the check valve. The failure of the titanium component in a high-pressure nitrogen tetroxide environment was sufficient to cause ignition of the check valve and led to an explosion. It is worth noting that the reaction between titanium and nitrogen tetroxide at high pressure was not expected.”
SpaceX, which was founded in 2002 by Elon Musk and has its headquarters in California, manufactures and launches advanced rockets and spacecraft. The private company was checking the vehicle’s propulsion systems before a planned test of the in-flight emergency abort system.
SpaceX continued: “SpaceX has already initiated several actions, such as eliminating any flow path within the launch escape system for liquid propellant to enter the gaseous pressurisation system. Instead of check valves, which typically allow liquid to flow in only one direction, burst disks, which seal completely until opened by high pressure, will mitigate the risk entirely. Thorough testing and analysis of these mitigations has already begun in close coordination with NASA, and will be completed well in advance of future flights.”
Due to the test failure, SpaceX has rearranged its spacecraft assignments to stay on track for Commercial Crew Programme flights. The Crew Dragon spacecraft originally assigned to SpaceX’s second demonstration mission to the International Space Station (Demo-2) will carry out the company’s In-Flight Abort test, and the spacecraft originally assigned to the first operational mission (Crew-1) will launch as part of Demo-2.
In 2012, SpaceX’s Dragon spacecraft became the first commercial spacecraft to deliver cargo to and from the International Space Station.