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SpaceX Blast Investigation Suggests Breach in Oxygen Tank's Helium System (reuters.com)
Weeks after a SpaceX rocket exploded inexplicably, engineers at Elon Musk's company have traced the flaw to its source. Space today released the initial results of its investigation, in which it says that a breach in helium system in the Falcon 9's liquid oxygen system caused the sudden flare up. From a Reuters report: SpaceX, owned and operated by technology entrepreneur Elon Musk, was fueling a Falcon 9 rocket on the launch pad in Florida on Sept. 1 in preparation for a routine test-firing when a bright fireball suddenly emerged around the rocket's upper stage. "At this stage of the investigation, preliminary review of the data and debris suggests that a large breach in the cryogenic helium system of the second stage liquid oxygen tank took place," SpaceX said in a statement posted on its website. No one was hurt in the explosion, which could be heard 30 miles (48 km) away from SpaceX's launch pad 40 at Cape Canaveral Air Force Station. The cause of the accident is under investigation.
I would ASSume that the helium is used to pressurize the fuel and oxidizer tanks. Would be stored as a liquid to save space...
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No. The helium is used to pressurize the liquid oxygen tank and provide back pressure to the engines. Basically it's the gas that's used to shove the LOX down the fuel lines to the engines as fast as possible.
Also when you're listening to the com loop when you hear "Engine chilldown has begun, they're pumping through the engine.
The prior mishap was caused by one of the struts that holds these tanks to the inner walls failing.
This failure was caused by the tank itself bursting.
I'm suspecting they're going to have to reengineer the COPV helium tanks to be a bit tougher.
Yes Francis, the world has gone crazy.
That's not quite how it works. In zero g, just adding Helium pressure to a tank won't accomplish much. You either have to use some kind of pressurized bladder to force the liquid down (ok for thrusters, too big a weight penalty for the main engine fuel and oxidizer) or supply a small acceleration, say from auxiliary thrusters, to settle the liquid to the bottom of the tank prior to ignition. Then He pressure can push the liquid into the main pumps which, in turn, provide enough pressure to force the liquid into the engine against its internal pressure.