Originally Posted by
kangaroota
NASA are about to test fire 4 RS25 engines together producing 7 megatons of thrust.
My question is, how do you hold the assembly down and prevent damage to the engines straining against the thrust?
I doubt a couple of ratchet trailer tiedowns would cut the mustard.
Million pounds I'd suggest.
FWIW the Saturn V (first stage 5 X F-1 engines) totalling 7.5 million pounds of thrust was held down for several seconds on the launch pad prior to being released.
That was done by four relatively small, retractable hold down arms at the base of the vehicle so I'd expect the engineers these days could rig up something to hold down something with a bit less thrust..
There is video here of the first test firing of the Saturn V first stage (sorry for the breathless commentary):
There's video here with a much better commentary which gives the hold down arms a mention:
Edit to add: For clarity in the bottom video the hold down arms are hidden under the "small" quadrant shaped covers. The much large "levers" that swing up are the tail service masts that provided electrical connections, electrical power and other consumables etc to the first stage prior to launch.