

A failed strut caused the SpaceX rocket explosion - btmills
http://www.theverge.com/2015/7/20/9004463/space-x-falcon-9-rocket-explosion-cause-explained

======
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?

~~~
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?

~~~
Nadya
A pressure vessel does a bit more than a tank. While a tank may house
liquids/gasses, it typically does not regulate or maintain a certain amount of
pressure that is different from the natural, ambient pressure.

Anyways - perhaps it was my misreading or an edit after-the-fact by the parent
(can posts even be edited on HN after responded to? I haven't tested or taken
particular notice of it), they seemed to be confused that the statement
switched from talking about an oxygen tank and then a helium tank (as if both
were the same tank) and were confused about which gas the tank contained, when
in fact there are 2 containers and not 1 with the gas being mixed up. I was
simply clarifying that. There is a helium pressure vessel and an oxygen tank -
not an oxygen tank that is later called a helium tank.

I don't remember seeing the question appended at the end when I responded:

 _> is the helium tank inside the oxygen tank?_

------
keithwhor
Elon Musk has played KSP. He should've known you can never have enough
struts... ;)

~~~
Maxious
The /r/spacex automoderator was set to report KSP references...
[https://www.reddit.com/r/spacex/comments/3dyvta/rspacex_crs7...](https://www.reddit.com/r/spacex/comments/3dyvta/rspacex_crs7_failure_investigation_teleconference/cta31bw?context=1)

------
mesozoic
I'd find it very interesting to know how they diagnose a problem like to such
a specific cause this when most of your physical evidence has disintegrated.

~~~
agildehaus
They had 0.893 seconds of data, some of which was from the accelerometers
surrounding the LOX tank exterior.

That accelerometer data allowed them to acoustically triangulate the sound of
the strut breaking. I think they even know which one.

------
modeless
Why isn't this on the front page with 24 points in an hour? I know HN cares
about this news.

~~~
greglindahl
A reddit thread made the front page instead. Because we all come here to read
reddit.

~~~
modeless
To be fair, the reddit thread is much better than any press article including
this one. However that doesn't explain why this one didn't rise up since it
was posted hours earlier and had plenty of votes. I've seen other The Verge
articles fail to reach the front page before. I suspect The Verge links get a
pretty severe ranking penalty automatically applied. I don't know why, though.

~~~
greglindahl
When something like this gets a lot of votes, I always imagine that the mods
will notice and then link something better, like
[http://www.spacex.com/news/2015/07/20/crs-7-investigation-
up...](http://www.spacex.com/news/2015/07/20/crs-7-investigation-update)

If I wanted to read a reddit thread, I know where to find it.

