From: "Sean McCutcheon" <[EMAIL PROTECTED]> > What if there is a puncture?
If there is a puncture in the first inflatable? Trash it. How about in the second one? If the first one made it up, and stayed puncture-free long enough, a small puncture in the second one doesn't matter so much. You can poke a hole in a paper bag and still blow it up inside another paper bag, after all. And you're recycling the propellant gas anyway. You'll lose gas some in testing whether there's an unacceptable hole. But only really in the first inflatable. (Why worry? Gas for inflatables in a vacuum is a tiny fraction of total payload.) If the first and second inflatables both had serious punctures, you know what? You send up a third one.... The thing to understand here is that if you can gun-launch inflatables at $600/lb or less, you're outperforming even the cheapest orbital launch ever done (Russian retrofitted sea-launched ballistic missile at $1,800/lb, hidden subsidies unknown), and far outperforming most industrial launch. So you can afford failure. Imagine that - affordable failure. -m > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of > [EMAIL PROTECTED] > Sent: Thursday, April 08, 2004 1:23 PM > To: [EMAIL PROTECTED] > Subject: Re: The gun thing again > > > > An alternative would be to send up smaller spaces that connect together > like bubbles. I guess it really depends on what is considered small for > launching. If to objective would be to have a living/working space of say > a 10x10x10 feet, you could send it in a package as small as 4x4x4 and it > will include all the materials to expand it, seal it and prepare it for > the next one. If you build them with three hatches each, you can create > some great combinations! > > Joe L. > > > > > > Joe Latrell writes: > >> Having done some experiments in gun launching (nothing to orbit mind > >> you) there are a lot of factors involved that make it very > >> unattractive. Heat is a really big issue. > > > > I've read papers that suggest a dead-mass burden of about 15% for > > ablative shielding. I.e., in the same ballpark as reentry capsules. No > > showstopper, at least for the optimist. Launching from higher altitudes > > definitely helps, since even 14,000 feet gets you above over 25% of the > > atmosphere. > > > >> However, the geosync inflatable station is a great idea. Using a > >> transhab type design, you can launch a really big space station with > >> only a few launches, assemble it (self assembly?) and then get to work > >> building probes to wherever you want to send them. > > > > Engineering inflatables for gun launch is an interesting idea. There > > may be some kinks in it (as it were), but it seems ideal for solving > > many construction problems. If you perfected rendezvous, one approach > > that I think would be kinda cool is: > > > > 1. launch an inflatable > > 2. inflate it > > 3. launch another > > 4. rendezvous at some orifice > > 5. inflate the new one *inside* the current one > > (vent residual gas to a pressure tank, and > > reuse the gas for future inflation) > > 6. repeat from 3 until you have enough layers > > for whatever purpose desired. > > > > This is nice because it means you can build structures of considerable > > mass within small payload limitations, and because it's fault tolerant > > -- blow a launch or miss a rendezvous, and the relative cheapness of gun > > launch (amortized over many launches, anyway) means just planning for a > > few more launches than the absolute minimum. > > > > To Jack's questions: > > > >> > Sundry clever primates around the world .... > > > > Having met me recently, Jack, you know just how ridged a brow and > > prognathous a jaw you're dealing with, in talking to me. (Thanks for > > the back-shaving tips, by the way. ;-) > > > >> > OK, OK, I know. The gun thing won't work for orbital delivery of > >> stuff to build Europan probes because one can't shave the big bump > >> off of the resultant wobbling orbit ... or +- something like that. > > > > "The big bump"? If you mean that it starts out very elliptical, shaving > > the big bumps (which I'm better at now; my back isn't as red and sore as > > it used to be) amounts to circularizing the orbit. If you launch enough > > fuel into the same orbit as the original projectile, you can use it to > > circularize the orbit at perigee pretty efficiently, or even just head > > right on out of Earth orbit, I would think. (Joe? You're the guy who > > most recently did the orbital dynamics stuff, right?) > > > >> > However if one were to cant the trajectory of an equatorial gun back > >> a little to the west, a projectile could be delivered which would > >> "die" into a geosynchronous orbit. Granted, you'd only get one shot > >> per gun per day, but at say a ton per shot ... > > > > Um. Hm. I did some rough calculations a while back, looking at > > shooting straight up and using the Earth's rotation as free vector, and > > I remember coming up with an orbit out past the moon. But you're > > proposing something else, I realize. Still, I don't think you can get > > GEO without a burn, no matter what. > > > > Everything I've looked at suggests that you need a kick stage at the top > > just to avoid grazing the atmosphere on the backswing. Of course, it's > > also possible to coast up to a libration point, I suppose. But that's a > > lo-oo-ong way out there. And means a bigger gun. How much bigger? > > Haven't figured it out. Probably not too much smaller than what you'd > > need for Earth escape velocity. > > > >> > Then from this orbit, a finished product could be dropped and > >> > sling-shotted with Earth gravity assist to wherever. > > > > "Dropped"? In some sense (a sense that drove Newton crazy until the > > light bulb went on in his head) GEO is *already* "dropping" - in a > > circle. > > > > My impression is that slingshotting works with moons planets. > > "Dropping" *does* sort of make sense if you talk about the Sun-facing > > Sun-Earth libration point: drop it toward Venus, or rather give it a > > little shove at just the right time. Not sure where that point is in > > relation to the Van Allen belts, but if you're already rad-hardened for > > near Jupiter, maybe the Van Allen belts are negligible anyway. > > > > Joe! Help! I'm talking barely-informed nonsense, right? > > > >> >>From another of my cerebral railroad sidings - an inflatable Mylar > >> > geosynchronous space station would be a pretty handy toy too - at > >> say 95% gun delivered. > > > > Reasonable enough, to my mind. Some guy is working on slabs of plastic > > for shielding, good on the cosmic ray aspect because of their high > > hydrogen content. The stuff seems to perform as well or better than > > aluminum by almost every measure. My laminate-in-space inflatable > > scheme would seem to amount to the same thing, just different > > fabrication technique. > > > >> > I await the group's scorn. > > > > I say you get an I (Incomplete) on orbital dynamics, A for thinking > > creatively, D- minus for being so narrowly on-topic. But my GPA isn't > > much better on this list. What say the other committee members? > > > > -michael turner > > [EMAIL PROTECTED] > > > > == > > You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] > > Project information and list (un)subscribe info: http://klx.com/europa/ > > > > == > You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] > Project information and list (un)subscribe info: http://klx.com/europa/ > > > > == > You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] > Project information and list (un)subscribe info: http://klx.com/europa/ > > == You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
