Thursday 1 February 2007

That's Why They Call It "Rocket Science"

Deset, Devyat, Vosem, Sem... That countdown in Russki brings back memories of interesting weapons test tapes during the Cold War. I'm sure my Russki opposite numbers found some of our tests just as interesting.
This attempted launch though was of a civilian satellite, from Sea Launch using a Russian Zenit booster. From the looks of it, they had successful main engine start, then a loss of thrust just as the clamps were let go. The results, as can be seen, were spectacular, and Sea Launch's one and only launch pad is going to look distinctly second-hand. Of course, in the Rocket Biz, it's not a "failure", anything at all unexpected, from a transient sensor glitch to an Earth-Shattering Kaboom is an "anomaly".
Here's an example:

That was a liquid-fuelled Delta-II launch vehicle, with solid-fuel auxiliary boosters. Solid-fuel rockets are a pain, especially when you're near where one hits. You see, solid rocket fuel burns hot. It burns quite happily underwater, or soaked in foam, it contains its own oxidiser. It produces lots and lots of hot gasses that transfer the enormous heat to everything around it, melting glass, causing aluminium to burn, etc etc. A solid-fuel anti-ship missile doesn't really need its warhead going off to give you a Very Bad Day.
Having many tons of burning solid fuel raining down in lumps like that is not conducive to the good health of anyone outside a bunker.
Another view showing the size of the explosion, taken from further away, is available here. More Fun with Rocket Failures below - including a static structural test showing that the assembly wasn't quite strong enough.


Calamity Jane said...

Houston we have an anomaly ... anomaly, classic quasi-military understatement (and yes I know it was a Cape launch).

What always intrigues me with crash investigations of this nature is how in the name of Christmas can they determine after piecing together all the thousands of bits of debris, that it was a 17 foot crack in the SRB? And 17 feet? How could the pre-launch checks miss that?

David J said...

Sweet, sweet earth-shattering kabooms!

Ahem. I mean, thank you for that most enlightening exposition on the effects of the laws of physics.

Anyway, must go, my room looks like an anomaly has hit it.

Zoe Brain said...

Inspecting for voids and cracks in SRBs is difficult. X-rays can only do so much, MRI is probably better. But if a crack develops after inspection due to thermal stress... the way you find out is to have a teeny problem, then try to replicate the conditions, then find out the oopsie, and try again.
The burn rate of a sold fuel chunk depends on its surface area. If it has a crack or void, the surface area suddenly increases when the flame front hits it, and burn rate rapidly increases. This is otherwise known as an explosion.