Landing a capsule on a huge airbag?

When a stuntman jumps off of a build, he lands on a large airbag. The
idea of having a reusable capsule land on a huge airbag seems interesting.
If the capsule has some lift (like Apollo) and a parafoil, it seems
we could get a capsule to do a pinpoint landing and even flare at the
end. This should be gentler on the people and avoid the salt water
corrosion problem of landing in water.

You would of course want 2 parafoils, 2 computers, 2 differential GPS units,
etc. 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. It might not be reusable if it missed, but the people
should survive. People survive car crashes with less deceleration
protection than a form fitting couch.

As long as the crumple zone is made of things you needed anyway, it
should be lighter than landing rockets, landing gear, or a large parachute.

Does a crumple zone seem reasonable?
Is the pinpoint landing the only big problem with this?
Could it be done reliably?

- Vince

Vincent Cate wrote:
When a stuntman jumps off of a build, he lands on a large airbag. The
idea of having a reusable capsule land on a huge airbag seems interesting.
If the capsule has some lift (like Apollo) and a parafoil, it seems
we could get a capsule to do a pinpoint landing and even flare at the
end. This should be gentler on the people and avoid the salt water
corrosion problem of landing in water.

You would of course want 2 parafoils, 2 computers, 2 differential GPS units,
etc. 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. It might not be reusable if it missed, but the people
should survive. People survive car crashes with less deceleration
protection than a form fitting couch.

As long as the crumple zone is made of things you needed anyway, it
should be lighter than landing rockets, landing gear, or a large parachute.

Does a crumple zone seem reasonable?
Is the pinpoint landing the only big problem with this?
Could it be done reliably?


Or alternately. carry the airbag with you, like Mercury.

Brett

On 19 Sep 2003 08:22:53 -0700
(Vincent Cate) wrote:

When a stuntman jumps off of a build, he lands on a large airbag. The
idea of having a reusable capsule land on a huge airbag seems interesting.
If the capsule has some lift (like Apollo) and a parafoil, it seems
we could get a capsule to do a pinpoint landing and even flare at the
end. This should be gentler on the people and avoid the salt water
corrosion problem of landing in water.

You would of course want 2 parafoils, 2 computers, 2 differential GPS units,
etc. 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. It might not be reusable if it missed, but the people
should survive. People survive car crashes with less deceleration
protection than a form fitting couch.

As long as the crumple zone is made of things you needed anyway, it
should be lighter than landing rockets, landing gear, or a large parachute.

Does a crumple zone seem reasonable?
Is the pinpoint landing the only big problem with this?
Could it be done reliably?

I think it would be better if the airbag was attached to the spacecraft. Wasn't this the issue with John Glenn's heat shield? That instruments suggested that an airbag had dislodged the heatshield?

The airbag would only have to be a metre deep or so to significantly reduce the G load at impact. And they are light, and they have been known to work: Pathfinder.

How about using a contact probe to trigger the bag inflation? Perhaps the sequence could be:

1. Drop the heat shield
2. Deploy the contact probe
3. Fire the airbag when the probe detects the surface.
----
Michael Smith
Mail address and GPG key available from www.netapps.com.au

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.1 (GNU/Linux)

iD4DBQE/bZxoVBAeZyhLJFgRAvwMAJjtUTab00CCuIM6z+FUEhEp6Hr5AJ 4x8MQN
/MpkFoXsJAIbLbj5OWMi7w==
=x/LK
-----END PGP SIGNATURE-----

Vincent Cate wrote:

When a stuntman jumps off of a build, he lands on a large airbag. The
idea of having a reusable capsule land on a huge airbag seems interesting.
If the capsule has some lift (like Apollo) and a parafoil, it seems
we could get a capsule to do a pinpoint landing and even flare at the
end. This should be gentler on the people and avoid the salt water
corrosion problem of landing in water.

You would of course want 2 parafoils, 2 computers, 2 differential GPS units,
etc. 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. It might not be reusable if it missed, but the people
should survive. People survive car crashes with less deceleration
protection than a form fitting couch.

As long as the crumple zone is made of things you needed anyway, it
should be lighter than landing rockets, landing gear, or a large parachute.

The Soviets/Russians always seemd to get by with terminal rockets.
Are our margins so tight that we can't consider that?

Does a crumple zone seem reasonable?
Is the pinpoint landing the only big problem with this?
Could it be done reliably?

- Vince

It means intolerance to *very* small landing errors. That's why we
used to land on water. One piece of the Pacific's just as soft as
another....

Vincent Cate wrote:
When a stuntman jumps off of a build, he lands on a large airbag. The
idea of having a reusable capsule land on a huge airbag seems interesting.
If the capsule has some lift (like Apollo) and a parafoil, it seems
we could get a capsule to do a pinpoint landing and even flare at the
end. This should be gentler on the people and avoid the salt water
corrosion problem of landing in water.

You would of course want 2 parafoils, 2 computers, 2 differential GPS units,
etc. 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. It might not be reusable if it missed, but the people
should survive. People survive car crashes with less deceleration
protection than a form fitting couch.

As long as the crumple zone is made of things you needed anyway, it
should be lighter than landing rockets, landing gear, or a large parachute.

Does a crumple zone seem reasonable?
Is the pinpoint landing the only big problem with this?
Could it be done reliably?

- Vince

How much weight for the capsule to carry it's own airbags?
(pictures a capsule inside an inflated lifting body.)

In article ,
Michael Smith wrote:
I think it would be better if the airbag was attached to the
spacecraft. Wasn't this the issue with John Glenn's heat shield? That
instruments suggested that an airbag had dislodged the heatshield?

Correct -- *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.)

The airbag would only have to be a metre deep or so to significantly
reduce the G load at impact. And they are light, and they have been
known to work: Pathfinder.

Unfortunately, contrary to popular mythology, the Pathfinder airbag system
turned out to be complex and quite heavy -- considerably heavier than
landing rockets. Crushable solids like aluminum honeycomb or balsawood
are actually rather lighter than real airbag systems. This was known in
the early 60s, but it keeps getting forgotten.

Even the Mercury airbag ended up much more complex than people had
expected, quite a difficult design and development problem. It needed
reinforcing straps to keep the skirt from tearing due to side loads, an
internal cable network to prevent the heatshield from banging around too
vigorously due to wave action after water landing, a layer of honeycomb to
protect the hull against the possibility of being hit by a heatshield edge
during touchdown, and crushable honeycomb under the couch for extra safety
margin. And a land touchdown with it would have been a traumatic event,
probably involving severe tumbling. It is very difficult to make such a
system cope gracefully with land touchdown with a substantial horizontal
velocity, i.e. due to wind; that's why it was rejected for Apollo (which
did originally have a land-touchdown requirement).

Mars Pathfinder used airbags not because they're a great landing system
(although there were hopes of that early on), but because they permit safe
unguided landings on very rough terrain. If, that is, the application is
an unmanned probe, which can simply cover itself in airbags and bounce and
roll for long distances before stopping. (Pathfinder bounced and rolled
for 2.5 minutes, covering about a kilometer. The first bounce was 18G.)
Oh, and further complexity had to be added to it for the MERs, because it
doesn't handle winds well, and the MER landings are at a different time of
day when winds are expected to be higher.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

JRS: In article , seen
in news:sci.space.tech, Vincent Cate posted at Fri,
19 Sep 2003 08:22:53 :-

You would of course want 2 parafoils, 2 computers, 2 differential GPS units,
etc. 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. It might not be reusable if it missed, but the people
should survive. People survive car crashes with less deceleration
protection than a form fitting couch.


Alternatively, design the vehicle with an internal crumple zone or air
mattress under each individual couch. This adds little mass.

The vehicle has one degree of reusability-importance and one degree of
impact-resistance; a passenger has a different degree of each. Design
for these appropriately.

Just consider the state of the car after a car-into-wall crash in which
a well-deployed airbag made the occupant into a minor medical case.
Normally, I believe, not reusable.

--
© John Stockton, Surrey, UK. Turnpike v4.00 MIME. ©
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
some Astro stuff via astro.htm, gravity0.htm; quotes.htm; pascal.htm; &c, &c.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

(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

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~
Vincent Cate Space Tether Enthusiast
http://spacetethers.com/
Anguilla, East Caribbean http://offshore.ai/vince
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~

You have to take life as it happens, but you should try to make it
happen the way you want to take it. - German Proverb

Dr John Stockton wrote:

The vehicle has one degree of reusability-importance and one degree of
impact-resistance; a passenger has a different degree of each. Design
for these appropriately.

Just consider the state of the car after a car-into-wall crash in which
a well-deployed airbag made the occupant into a minor medical case.
Normally, I believe, not reusable.


But cars are not designed for such. You could design such a car -
start with a VW Beetle and make sure front and backparts are easy
to separate and that you can attach a new front part.

--
Sander

+++ Out of cheese error +++

JRS: In article , seen in
news:sci.space.tech, Sander Vesik posted at
Thu, 25 Sep 2003 18:52:27 :-
Dr John Stockton wrote:

The vehicle has one degree of reusability-importance and one degree of
impact-resistance; a passenger has a different degree of each. Design
for these appropriately.

Just consider the state of the car after a car-into-wall crash in which
a well-deployed airbag made the occupant into a minor medical case.
Normally, I believe, not reusable.


But cars are not designed for such. You could design such a car -
start with a VW Beetle and make sure front and backparts are easy
to separate and that you can attach a new front part.

You remind me of a cartoon by one of the UK's great motoring
cartoonists.

A manifest veteran enthusiast in an open-top Jaguar was surprised and
disgruntled at being overtaken by a youth driving a small car consisting
of the front of a (FWD) Mini welded to the back of a (rear-engined) VW
Beetle. Two engines beats one.


However, I introduced the car to show that there exist circumstances
where the passengers are very much less harmed than the vehicle.

--
© John Stockton, Surrey, UK. Turnpike v4.00 MIME. ©
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
some Astro stuff via astro.htm, gravity0.htm; quotes.htm; pascal.htm; &c, &c.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.