Landing a capsule on a huge airbag?

(Henry Spencer) wrote in message ...
With that, you don't really need the airbag. The flare maneuver handles
the landing deceleration, at least in principle.

It seems a reusable capsule would still need some kind of landing
gear to avoid damaging the heat shield. This would be extra weight
and also break the integrity of the heat shield. The air bag method
would not have either of these problems.

...The capsule would be reusable as long as it hit the airbag, and
have a crumple zone (like a car, Armadillo Aerospace, or Apollo seats)
in case it missed...

There have been proposals for capsules which simply use crushable shock
absorbers for land touchdown. The trick is that you build the capsule
somewhat oversize -- appreciably larger than the pressure hull inside --
so that there is room for a reasonably long shock-absorber stroke.

It seems there is a center of gravity problem. You want your weight
to be really low for stability during reentry.

Henry from another post:
... -- *after* reentry, the Mercury heatshield dropped down a few feet
on a fabric skirt, forming an airbag to reduce impact loads, mostly to
cover the case of an emergency land touchdown. (Apollo had its couches
mounted on an internal shock-absorber system for that case, while the
Gemini procedure for a land touchdown was to eject.)

That Mercury trick seems to solve the center of gravity problem but
I would rather have my heat shield firmly attached (I never understood
why it was not before). John Glenn's feared dislodgement could have
been real with that design. The Gemini method of ejection seats would
add a lot of weight and at least some additional danger.

Apollo's method seems to add the least chance of an additional bad
failure mode.

John Stockton in another post:
Alternatively, design the vehicle with an internal crumple zone or air
mattress under each individual couch. This adds little mass.

I like the idea of an air mattress under each couch that you inflate
after the parachute is open so that you have a low center of gravity
during reentry.

I am thinking of a capsule for a bunch of people (currently 11)
on a very short trip like 4 hours if all goes well and 8 hours if it
misses a connection with a GEO tether and goes back to Earth.
For this short time it would not need a lot of life support. So a
higher than normal fraction of the weight would be people. So keeping
their weight high during reentry might be bad.

-- Vince

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Vincent Cate Space Tether Enthusiast
http://spacetethers.com/
Anguilla, East Caribbean http://offshore.ai/vince
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You have to take life as it happens, but you should try to make it
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