SpaceX SN4 goes BOOM

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Marc_G

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Ooops. Yeah, that will buff right out.

This is a setback for sure. Bummed to hear this; was looking forward to the FAA approved test hops.
 

Reinhard

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The Starship SN4 prototype was planned to perform a "hop" flight test after the crewed Dragon mission, but after today's static test, that's not an option anymore. The test itself appears to have worked well, but before it got completely detanked, something happened.


The current group of new launch vehicles in development all share a common propellant combination, methane and LOX. Liquid methane and LOX are miscible. The end result is liquid explosive that is about twice as energetic as TNT and much more sensitive. So theoretically a rocket weighing in the kilotons, with most of that being propellant, can approach mushroom cloud territory (e.g. after a common bulkhead separating the tanks fails).

For comparison, other propellant combinations like LH2/LOX or RP1/LOX can also create big explosions, but to a lesser degree. Because the liquid temperature range of both propellants doesn't overlap, they can't be mixed well. This limits how much of the total available energy can be released in the form of a detonation.

Those are all theoretical worst case scenarios, but I still wonder what kind of safety distances we will be seeing when these rockets become operational.

EDIT: @Marc_G was faster:

Reinhard
 

OverTheTop

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I read that they had quite a few hot test fires on it, so hopefully it was useful enough to them even though they didn't get to fly it later in the year :(. The forces on those bulkheads must be enormous. Hopefully they will release what the problem was sometime.

SN5 is in work currently.
 

Peartree

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Scott Manley has a decent analysis of the explosion. The hot fire test was over. The explosion had nothing to do with the vehicle but was apparently caused by a bad disconnect device.

Scott Manley's YouTube video here

 
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