To a certain extent, the complacency is understandable. Although three separate resupply missions to the International Space Station – including CRS7 – have failed in the last 12 months, until this one, Space X had a seven-year run of near flawless launches. True, it has failed to effectively recover the Falcon 9 booster rocket first stage on its automated barge as intended, but that was a secondary aspect of each mission.
Related: Update: Here’s the full video of SpaceX’s CRS 9 rocket exploding after landing
“To some degree, I think the company became maybe a little bit complacent,” Musk said (via Space) to reporters earlier this week during a teleconference. “I think this is certainly an important lesson, and something we’re going to take with us into the future.”
During the chat, Musk also revealed what it was they believe went wrong during launch. The CRS7 rocket exploded just prior to the second stage separation and it’s thought likely to have been caused by an overpressure event in an oxygen tank. Those tanks contain cannisters of liquid helium, which is designed to be released as the O2 is burned off to maintain a constant pressure within the tanks.
Unfortunately, one of the struts holding one of the cannisters in place broke off when the space craft hit 3.2g of acceleration, sending it crashing into the interior of the tank. When the helium cannister ruptured, it dumped its entire contents into a near-full tank, causing it to over-pressurize and explode.
Since those struts are provided by a third party, we would imagine Space X will be using another contractor in the future.
