
Falcon Heavy’s 3 first stage cores have all completed testing - diggernet
https://twitter.com/SpaceX/status/903820580012474369
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smegel
Will they do a hold-down test with all three boosters strapped together? As
that may incur that risk of non-synchronized ignition "side-effects".

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wereHamster
Isn't the rocket usually strapped down to the launch pad until all engines are
confirmed working properly? What would these side effects be?

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smegel
If one engine starts even a fraction of a second too late, it will suck up the
exhaust from the other engines with predictably mission ending consequences.

I might totally wrong, but I don't think the engine are brought up to full
throttle in a normal launch while it is still strapped down. In a hold down
test, they are. I am just wondering if they are going to to risk possible
synchronization issues in a hold down test, which effectively doubles the
chance they will encounter a problems vs doing it once at launch.

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nkoren
Falcons are held down at full throttle for three seconds prior to launch, to
ensure that everything is working perfectly before letting go. (They've
aborted during this period in the past, although that was a long while ago.)
As far as I know, this is unique among launch vehicles. I presume (but do not
know for certain) that they will do the same for the heavy.

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JshWright
Well, they're held down as they are throttling up. They aren't at full
throttle the whole time.

