Space/Science — HabitableZone

Space/Science » in reply to Man-rating an existing rocket

re: Man-rating an existing rocket
gbaikie — (archived)

"Manned rockets must have a steady acceleration (3 G's) and make the transition between first stage engine cutoff and second stage ignition as smooth as possible.
That's a different rocket!!"

Ariane 5 has max of 4 to 5 gees.
Delta IV and Atlas V have about 5 to 6 gees
SpaceShipOne had 5 to 6 gees:
"The pilot experiences between about 5 or 6 g's of deceleration as he comes back into the atmosphere."
http://www.howstuffworks.com/spaceshipone1.htm

The emergency escape on these manned rockets has about 15 gees.

I wouldn't be surprised if SpaceShipTwo makes some effort at lowering the gees to 3-4, because there is not doubt that high gees are uncomfortable.
But I don't think a requirement on manned rockets should be less than 4 gees. It probably be good to have it less than 6 gees, though.

Another aspect is that getting crew to LEO is a fairly small part of getting crew and stuff to the Moon. For example Altair Descent module: 35,055 kg (77,280 lb).

Just to get the Altair Descent module to LEO will require 30 times more lift than a crew.
Now, Altair doesn't need to be designed to withstand very high gees for it's capability to operate in the lunar environment. You might want it to experience less gees than a crew getting to LEO.

But even if you had a crazy requirement of less than 3 gee to LEO for crew and the Altair that's still a small fraction of total mass needed to get to the moon.

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