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Space Forum / Space Flight / September 2003Landing 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 > 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. [quoted text clipped - 16 lines] > 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 > 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. [quoted text clipped - 16 lines] > 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 >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.  SignatureMOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer first ground-station pass 1651, all nominal! | henry@spsystems.net > 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. [quoted text clipped - 12 lines] > 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.... > 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. [quoted text clipped - 18 lines] > > - Vince How much weight for the capsule to carry it's own airbags? (pictures a capsule inside an inflated lifting body.) JRS: In article <9186edb5.0309190722.5848cb75@posting.google.com>, seen in news:sci.space.tech, Vincent Cate <vince@offshore.ai> 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. Signature© John Stockton, Surrey, UK. ?@merlyn.demon.co.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. > The vehicle has one degree of reusability-importance and one degree of > impact-resistance; a passenger has a different degree of each. Design [quoted text clipped - 3 lines] > 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. SignatureSander +++ Out of cheese error +++ JRS: In article <1064515956.607704@haldjas.folklore.ee>, seen in news:sci.space.tech, Sander Vesik <sander@haldjas.folklore.ee> posted at Thu, 25 Sep 2003 18:52:27 :- >> The vehicle has one degree of reusability-importance and one degree of >> impact-resistance; a passenger has a different degree of each. Design [quoted text clipped - 7 lines] >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. Signature© John Stockton, Surrey, UK. ?@merlyn.demon.co.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. |
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