[themoogle]

"The SpaceX explosion on June 28th was caused by a failed strut in the rocket's upper stage liquid oxygen tank, SpaceX chief executive officer Elon Musk said today. The strut was one of several hundred used to hold together the helium pressure vessels in the tank......"

Goes from saying Oxygen tank to helium tank... wait what? is the helium tank inside the oxygen tank?

[agildehaus]

Yep. Here's a photo from inside the LOX tank during a previous flight:

http://i.szoter.com/741dc2bcf5762a48.jpg

The two arrows point to the struts holding down a helium tank.

[Nadya]

It's a liquid oxygen tank with a helium pressure vessel in the liquid oxygen tank. Nowhere does it say helium tank.

[seanflyon]

It seems like you are drawing a distinction between "tank" and "pressure vessel", could you explain what the difference is?