Oh crap: http://www.scaled.com/projects/tierone/gallery/ground_general/Rocket_Test_Fire_800 I'm sure more details will start to trickle out, but it seems that the incident centres around the Nitrous Oxide oxidizer the company uses in it's hybrid rockets... But I was always led to believe that Nox was pretty inoccuous stuff - I guess at pressure etc, that's not the case. From the pictures it looks like they where using the old test-stand (or one that is very similar) that they used during the SSOne dfevelopment: Whilst my heart goes out to the families of those dead and injured, I just hope that this is not going to bring about some knee jerk reaction to the whole alt-space industry that's building up. Space travel is dangerous, and to get to far with so little fatalities / accidents is a blessing, when compared to the early days of flight. My worry is that the whole area will be so burdened with extra regulatory stuff that whatever spark there was to do it faster, differently, cheaper & arguably better than the big governmental schemes will be stiffled.
NO2, well, pretty dangerous stuff tbh. Lots of bond strain, and it forms N2, which has a very strong triple bond, and we all know making strong bonds releases a lot of energy. Not to mention the fact that we just produced O2, which happens to be a fairly good oxidiser
Death toll has risen to 3 now. http://space.newscientist.com/article/dn12367-three-dead-in-california-spaceport-blast.html If nox is so dangerous, why use it? As Burt says in the article above, it's not classed as a harzardous material - and the reason they use (IIRC) is ease of handling... It's safer than using cryogenic oxidizers (LOX) Hell, they even used Nox in the 'Confederate Rocket' episode of Mythbusters, as it was deemed a safe, readily available oxidizer that was around at the time of the American Civil War.
But when you oxidise and already oxidised substance under pressured conditions there's no doubt it will turn explosive. That test rig photo looks obliterated though :|
They use NoX because it's redially available and failry cheap. The alternative is somthing like hydrogen peroxide which is what the Germans used in their rocket planes (Me163, etc). The problem is that if it gets out it eats everything including the pilots. in solid fuel rockets they ususlly use potassium permanganate or somthing like it which is much more stable, but harder to control since you can't throttle it. On the space shuttle they use liquid oxygen as the oxidizer which works fine, but it's a pain in the arse to handle cryogenic liquids. Given the alternatives, NoX continues to look like a pretty good option, especially for a small operation like this one. My guess is they had a leak in the oxidizer piping which allowed the fuel and oxidizer ro combust someplace they shouldn't have. This is stull a relatively new technology and these things will happen. No one is going to worry about the dangers of commercial spaceflight until someone they can relate to gets killed. Bunch of rich people paying $200k a pop? Meh, let them blow themselves up.
