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Comment by rsp1984 | Hacker News Reader

rsp1984·

Can somebody properly explain the different stages of the explosion? Obviously there's the first explosion but then after about 3.5 seconds there's a second, bigger one.

What's exploding in the first boom and what in the second?

Then, about 12 seconds in, the "nose" is falling down and causing a 3rd explosion. Why hasn't the nose "co-exploded" already with the 1st or 2nd explosion?

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The first explosion is the smaller second stage igniting. The second, bigger explosion is the first stage exploding. The first stage has most of the mass of the rocket in the form of propellant and is what SpaceX lands on the barge after it separates from the second stage. The second stage is smaller and lighter, and puts the satellite into low earth orbit, or into its transfer orbit in the case of higher orbits (eg geostationary orbit).

The 'nose' falling is payload and its protective fairing. The idea of a fairing is to protect the the satellite from aerodynamic, heat and acoustic stress. It explodes because the satellite has propellant in it - certainly for its rcs system for attitude adjustment and station keeping, and it might have a main engine to help it reach orbit.

http://www.spacex.com/falcon9

http://www.spacex.com/news/2013/04/12/fairing

Just some wild guesses:

First explosion related to second stage (upper). Second explosion related to first stage's fuel igniting (I was expecting some much bigger, but likely there was already little oxygen left in that area and why it burned for so long. Third Explosion was the satellite's internal fuel (Hydrazine or something like it) detonating due to the fall damage and contact with the rest of the flame.

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