Private spaceflight company, SpaceX, has today announced the root cause of a costly explosion last year.
The Falcon 9 rocket’s fuelling process incorporates a supercooled liquid oxygen, which is chilled to temperatures lower than any other rocket in the industry.
On this occassion, during this fuelling, a series of composite overwrapped pressure vessels (COPVs) inside the second stage liquid oxygen tank began to buckle.
Liquid, or even solid oxygen was then able to build up within these buckles. It is suspected that when subjected to pressure, the built up oxygen ignited the carbon fibre overwrap of the pressure vessel.
After reviewing a large amount of telemetry covering a small 93 millisecond period of time, SpaceX was able to conclude that this series of events caused the catastrophic Falcon 9 explosion in September last year.
Changes to SpaceX Falcon 9 refuelling process planned
Over the course of the investigation into the cause of the incident, SpaceX worked with the Federal Aviation Authority (FAA) and Nasa.
SpaceX conducted further tests which replicated the failure model in controlled conditions.
The company promised to make changes to its fuelling process in order to avoid this happening again in the future.
“In the short term, this entails changing the COPV configuration to allow warmer temperature helium to be loaded, as well as returning helium loading operations to a prior flight proven configuration based on operations used in over 700 successful COPV loads,” SpaceX wrote in a post.
“In the long term, SpaceX will implement design changes to the COPVs to prevent buckles altogether, which will allow for faster loading operations.”
Return to flight
Alongside the announcement of these findings, SpaceX also announced that it would aim to conduct its return to flight in just 5 days time, on the 8th of January.
A Falcon 9 rocket is planned to carry a series of Iridium NEXT satellites, launched from Vandenberg Air Force Base in California, before it attempts a first stage booster landing at sea.
This flight would then be followed by another planned Falcon 9 launch approximately a week later from Florida for Echostar.