SpaceX Moves Past Explosion With New Launch Plans (cnn.com)

SpaceX plans to resume launching rockets as soon as next week, after completing an investigation into a spectacular launch pad explosion that destroyed a rocket and a satellite in September. From a report on CNN: The news comes following an in-depth investigation into the explosion of a rocket from SpaceX's September mission. The company said in a statement Monday the botched launch was due to a failed pressure vessel in a liquid oxygen tank. The vessel buckled, causing liquid oxygen to accumulate. It believes this led to friction, sparks and the explosion. SpaceX conducted the investigation along with officials from NASA, the Federal Aviation Authority, the U.S. Air Force and the National Transportation Safety Board. The Federal Aviation Administration will have to sign off on the report and issue SpaceX a license to launch. SpaceX appears optimistic it will be launching rockets again soon.

Comments

Re:Hope this is true

[NoNonAlphaCharsHere]

Ten minutes after Challenger blew up, the other engineers I worked with and I were saying to each other: "Watch, it'll come down to some idiot middle manager screaming "Whaddya MEAN I can't ship on time???". The thing about Rocket Science is: IT'S FUCKING ROCKET SCIENCE!!! Shut the fuck up about your pulled-out-of-your-ass ship date!

Would be nice...

[Rei]

... to actually get to see a detailed breakdown of the cause of the last explosion, rather than having to piece it together from bits and pieces of what's been said so far.

So far, it seems that there was (expected) supercooled liquid oxygen seeped into the CF reinforcing fibers on the helium COPVs (as was expected), which was just above its freezing point. They then began loading cold helium. Had the oxygen stayed liquid, it would have squeezed out (expected behavior). Rather, the oxygen wasn't able to seep out fast enough, and the increasing pressure caused some of it to solidify, blocking the escape of oxygen from the CF. LOX is inherently unstable in contact with organics, including carbon fibre, and can detonate under high temperatures, high pressures, shocks, etc; it has to be handled gingerly. In this case, the pressure continued to rise as the COPVs filled, until the LOX reached a critical pressure and detonated - thus rupturing the COPV reinforcement, thus the COPVs, thus the second stage and destroying the vehicle.

That's what it sounds like happened. But it'd be nice to get that confirmed or corrected if inaccurate. If this is correct, there's a number of things they could do to remedy it; I'd think the most likely would be to fill the COPVs before loading LOX.

As a side note, I'm really uncomfortable with their plan to make IPS entirely out of carbon fibre. As they're finding out (and has others have found out in the past), it's really difficult to use LOX with composites. And perhaps most importantly, inconsistently difficult. And the failure modes can be catastrophic - instant explosive rupture at the point of failure. Aluminum is not only light, but (by pure coincidence) one of the easiest things to work with LOX, as the oxide layer does a good job protecting the metal (even still, aluminum can detonate in contact with LOX in the right temperature/pressure/shock conditions, but said explosions are only self-propagating under significantly elevated pressure conditions). Also coincidentally, aluminum-lithium is even more resistant to reaction with LOX than lithium-free aluminum alloys. Basically, rocket manufacturers have been "having it easy" working with LOX by virtue of making rockets out of aluminum. You give that up when you go to composites.

But.... it's their rocket company, I guess we'll see how it goes.

Re:Would be nice...

[Bruce Perens]

We probably have ITAR to blame for not being able to read the full report. You can make all the FOIAs you want, ITAR is always going to be the excuse because all of the details of using a COPV successfully in a rocket is for the moment a trade-secret of a US company which the country doesn't want to hand over to North Korea, etc.

Besides it being their rocket company, they are making every effort to optimize delta-V over weight when nobody else in their market is trying. Otherwise, they would be using metal tanks and not attempting a high-risk technology like densification. You're going to blow up a few rockets if you take those risks.

Re:Would be nice...

[Rei]

LOX is unstable in contact with most organics. To the point that with the exception of some fluoropolymers, it's generally considered that all organics have a critical pressure in which they'll spontaneously combust with LOX. For many organics that pressure is below atmospheric pressure (aka hypergolic). For most plastics it is above atmospheric pressure, but not tremendously so. This includes the epoxy binders used in composites.

Yes, CF is the standard abbreviation for carbon fibre.

The LOX is supposed to be squeezed out of the CF as the COPVs pressurize. The COPV are comprised of a non-permeable aluminum inner liner and a permeable carbon fiber overwrap that bears the load. By freezing solid, the LOX was unable to escape the overwrap as the pressure increased as the COPVs were filled, and was correspondingly pressurized inside of it.

The system was not "designed so that it has areas which are likely to detonate". The LOX was supposed to be squeezed out of the overwrap, not become trapped in it as SOX.

None of their statements that I've come across mentioned "heating". They did, however, mention that the solidification of the LOX led to a pressure buildup. I've read quite a few LOX handing guidebooks (for working on a project involving LOX), and LOX pressurized against carbon fiber is considered an explosion hazard. You don't even store LOX in composite containers in low pressure conditions long-term. You know the main differences between a LOX dewar and a LN2 dewar? The latter often has either no lid and/or contains plastic or composite or silicone components. The former always has a lid and does not contain (non-fluorinated) plastic or composite components, and rarely silicone (fluoropolymers are usually okay). Also some metals don't work with LOX either.

It's not a case of "you say detonation, I say combustion". The spontaneous pressure-induced reaction of LOX and CF is a detonation. The rocket as a whole however was primarily consumed by a deflagration (non-supersonic combustion) between LOX and RP-1.

Nowehere in anything that I've seen from them were "sparks" mentioned.

Your "sparks" and "temperature" comments are directly in contradiction to SpaceX's comments about the conditions causing the formation of SOX and preventing the egress of LOX from the overwrap.

Re:Good for SpaceX

[gman003]

You can have $70M of your taxpayer dollars used on his rockets, or you can have $160M of your taxpayer dollars go to Lockheed Martin and Boeing. Your choice.

So:
* Cheaper by 55%
* Built entirely in America
* Doesn't give money to a country we're sanctioning
* No design elements from the 1970s
* Company is doing innovative things to drive down costs even more in the future
* Slightly more likely to explode

Seems like a good thing to me.