Follow-up on Mojave accident [Update]

From what I have seen from the helicopter videos.and It is difficult to say for sure but It dose not look like they had or were using a bunker or
earth berms for protection during the tests...It is too early to tell
but I would be concerned that they might have been conducting this test while standing in close proximity.
Rocket Engine component testing is always dangerous.
No mater what type of engine it is.

Posted by Ed at 07/27/07 07:19:23

They have bunkers and earth berms, and they use them for hot-fire tests. But this was a cold-flow test, not a hot-fire test, so I imagine they had different safety protocols.

Posted by anonymous at 07/27/07 08:09:23

It's relieving to see the bunker structure survived the blast even though it was powerful enough to knock over a tanker.

Posted by alonzo at 07/27/07 08:15:38

I would consider even a cold flow test with an oxidizer dangerous.
after all all it takes is fuel and an ignition source.
if they were doing cold flow tests with nitrogen that would be much safer but even then you have high pressure gas.
My guess (and it is just a guess) is that these guys were standing in the vicinity of test while it was being conducted.
I also did not see berms.
As for the Bunker I guess is missed that in the video, or photos.
Alonzo you mentioned that it survived.
were did you see a bunker? the orange sea-can?

Posted by Ed at 07/27/07 08:54:10

Ed,

I think you have hit on something. Apparently, Rutan does not consider a cold flow test of room temperature nitrous oxide dangerous. He has been quoted in several articles saying so. The facts are not in yet, but this mindset might have to be modified.

He also has been quoted as saying, the cause of the explosion is unknown. But rocket experts know that nitrous oxide is also a monopropellent, with an Isp of 120.

If a large amount of nitrous oxide was mixed over the site, with the right amount of air, and some ignition source existed, could a sort of fuel-air bomb have been formed? I don't know, but it seems like a logical possibility. People have noted that the car roofs appear to have been pushed in from above. I hope the FBI and the FAA get to the bottom of this, so it can be avoided in the future. That is the important thing. I hope this does not turn into another legal circus.

Posted by Tony Rusi at 07/27/07 10:21:43

Tony, it will be interesting to see what the fall out is...now that Northrop
has bought them.
From what I have seen the overall impression I get is that it seems like the testing was "casual"
Not to say that they did not have a procedure in place, just that a proper risk analysis had obviously not been done.
I personally have several years of experience in this sort of thing, and my first thought when I heard of a cold flow test explosion with N2O was that they should have been treating this like a hot fire test. Bunkers and close proximity earth berms should have been used. It seems that cars were parked just out side the fenced test area. and
storage tanks were near by.
This is an oxidizer not an inert gas like straightforward nitrogen.
As for ignition could have been many thing static electricity, car ignition...cigarette lighter...who knows.
What should have been know though was to keep the area clear of people when conducting a test with oxidizer.
Burt has said it him self that they did this same test many times.
Tony having a cloud of N2O is entirely possible as I am sure if they were doing cold flow test that they would likely have been using quantities and pressure equivalent to what a hot fire test would use.
As tragic as this accident is...It looks like fatalities were avoidable had proper procedures been followed...But until all the info is in it is hard conclusively say. Right now I am just reading the situation as the facts present them selves.

Posted by Ed at 07/27/07 11:47:02

<i>If a large amount of nitrous oxide was mixed over the site, with the right amount of air, and some ignition source existed, could a sort of fuel-air bomb have been formed?</i>

N2O doesn't react with air. It's an oxidizer, not a fuel.

I'd (with little real basis) suspect organic contamination somewhere as a contributing cause.

Posted by Paul Dietz at 07/27/07 11:56:38

Let me start by saying that I offer my sincerest condolences to the family and friends of the people involved in this tragic incident. I also hope for a speedy and complete recovery for the injured.

I agree with Ed & Tony on many things listed in their posts.

There was mention of berms and a bunker, only for hot fire tests . . .

The area was blanketed by N20, the burn pattern pretty well shows that.

The thing that REALLY surprises me is that people, including Burt Rutan, are commenting about this being a "Safe Test" that has been done many times before. Also, I believe that the rhetoric being spewed about hybrids, specifically but not limited to Jim Benson, being "safe non-exploding" is causing a dangerous mindset to propogate.

Any propellant components should be treated with respect, and a thorough risk analysis of any test involving any/all component propellants.

These people were working with a powerful oxidiser. It should have been obvious that mixed with air, scrub brush, vapour from vehicle fuel tanks etc. and ANY source of ignition, that the results that occurred were predictable.

I hope that the inquiry into this finds that ALL preventive measures were being taken and that this was a really freak accident, but the pictures and anecdotal evidence looks really damning.

Since this is California, I can picture the lawyers flocking to the area already. I think this will be really bad for Scaled.

my $ 0.02 worth.

Posted by Buck.Bundy at 07/27/07 12:05:27

Another thing I noticed was that the driver side door on one of the cars appeared to be left open. Maybe the car had just pulled up? Maybe there was a static electricity discharge as the driver was getting out? Maybe the hot engine was enough of an ignition source? I hope one of the survivors can fill in the details here. They say the Apollo 1 fire was a "failure of imagination". No one thought a 100% oxygen atmosphere was dangerous. I don't think anyone would contemplate doing a cold flow test with 100% gaseous oxygen in this day and age. Maybe this was a larger amount of nitrous than had been used before? Paul of course is right, there would have to be something to burn. If there was some type of contamination as fuel, some type of residue must still be at the site. But can't hydrogen peroxide just explosively decompose? My dad told me about flour blowing up when flour dust mixed with air in busy flour mills. And I have heard of coal dust doing a similar thing. An expert I know has said that "adiabatic compression could trigger a detonation." (I hated that word, adiabatic, in engineering school!) Whatever it was, let's figure it out, and develop a safe procedure, and stick with it. Never again!

Posted by Tony Rusi at 07/27/07 13:15:34

I just read this from a CP news story.
I wonder if it will put the breaks on this deal!

"Aerospace and defence contractor Northrop Grumman Corp. owns 40 per cent of Scaled and recently agreed to acquire the rest of it. The deal is awaiting regulatory approval and should close next month.

Northrop Grumman spokesman Dan McClain said the company had no comment on the explosion. "

Posted by Ed at 07/27/07 13:31:50

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