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#21
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Expandable modules??
In article , nospam@
127.0.0.1 says... This is all very curious and interesting. Must be the ultimate do-it-yourself kit. First the hab will have to be off-loaded from the Dragon capsule, then what? Is it assembled within the station or from the outside with it attached to the arm? Once attached to the Tranquility node it's inflated, so I imagine there are extra air cylinders included with the 'kit'? Anyone know? I might need to fire off an email to Mr. Perrotto for clarification... Or you could just watch the video. http://www.nasa.gov/multimedia/video...html?media_id= 158539341 Jeff -- "the perennial claim that hypersonic airbreathing propulsion would magically make space launch cheaper is nonsense -- LOX is much cheaper than advanced airbreathing engines, and so are the tanks to put it in and the extra thrust to carry it." - Henry Spencer |
#22
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Expandable modules??
In sci.space.station message -
september.org, Thu, 17 Jan 2013 07:25:27, Jeff Findley posted: In article om, says... Question: if a detached module is ordered to open a valve to let the air out, could this provide enough delta-V to cause it to drop sufficiently to cause re-entry ? Since this module is to be empty, the amount f energy required to lower its orbit would be less significant than a full module. You'd have to "do the math". One big challenge would be to insure it was pointed in the right direction when it was deflated. If it's got enough delta-V to reenter, it would have enough delta-V to impact the station. Due to safety issues alone, I'm guessing it will either remain completely inflated or would be only partially deflated before being released by ISS. You should be able to work it out for yourself. I've seen and forgotten the necessary figures, but no doubt you can find them. I'll assume that it, inflated, is roughly equivalent to a 4m cube of mass 2.5 tonnes. Volume 64m^3, 64000 litres; air is 1.2g/L, so 77kg of air - mass of air is 3% of total. Exhaust velocity will be of the order of Mach 1, 760 mph, so if the nozzle is efficient the delta-V of the module will be 3% of that, about 23 mph. IIRC, the delta-V of the re-entry burn of a Shuttle was of the order of 225 mph. Such a module therefore cannot power its own re-entry, though it could lower the orbit to be noticeably below that of the Station. Now re-do that with the correct figures for the module and a better estimate of the nozzle efficiency! I suspect they'll leave it at least partially inflated so that it remains a "fluffy" structure which will reenter faster than if they deflated it completely and caused it to become more dense. It is the initial lowering of altitude which takes longest - think "scale height" - so the effect of an initial reduction of orbit size may be more useful than maintaining fullest fluffiness. But, as a pure physicist's guess, I suspect that a great deal of deflation in pressure will be needed before the cross-section of the module decreases much. -- (c) John Stockton, near London. Mail Web http://www.merlyn.demon.co.uk/ - FAQish topics, acronyms, and links. |
#23
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Expandable modules??
In sci.space.station message -
september.org, Fri, 18 Jan 2013 08:04:54, Jeff Findley posted: An instantaneous force of approximately 74,000 pounds on ISS *is* what would happen in real life if the inflatable part detached from the CBM. Not quite. If the whole inflatable part detached suddenly, there would be an instantaneous removal of that force from a part which is designed to handle that force and also (for convenience in construction and assembly) to handle zero force. The effect would undoubtedly be bad enough, but not as great an overkill as a punch of 74,000 pounds applied to a similar-sized arbitrary area of the surface of ISS. If only the distal half detached, the instantaneous force would be greater in the ratio of the cross-section of the module to that of the hatch. -- (c) John Stockton, nr London, UK. Mail via homepage. Turnpike v6.05 MIME. Web http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms and links; Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News. |
#24
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Expandable modules??
On 1/18/2013 4:19 AM, Brian Gaff wrote:
No doubt the t shirt will be along shortly! Brian Umm, T Shirt? What would you like to have it say? I'm quite a bit easier to stump than Henry. His residence must look like an AIAA research library. https://www.aiaa.org/ In my case all I can give you is : Hey Dave didn't RMFP again... ? ;-) Dave |
#25
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Expandable modules??
"Jeff Findley" wrote in message
... In article , says... In article , says... There is a new release on this. seems to me though that they will be keeping it closed off most of the time in case of disaster. "Disaster" is a harsh word that I would not use. If there was any chance of it experiencing a sudden structural failure, the forces on ISS would not be pretty. If that were a likely possibility, it wouldn't be allowed to be attached to ISS at all. Imagine this "worst case" scenario: Thanks. Now you've given Bob a whole new thing to go nuts over. That said, like you, I'm pretty confident that NASA and Bigelow have done their work. BEAM "comes undone" where the inflatable part attaches to the "solid disk" end. The diameter of this looks to be roughly the diameter of a CBM, whose outside diameter is approximately 80 inches. The area of a disk 40 inches in radius is pi*r-squared or approximately 5027 square inches. NASA spec'ed ISS internal pressure as sea level, or 14.7 psi. So the instantaneous force on ISS caused by the "solid disk" releasing is surface area times pressure or approximately 74,000 pounds. In other words, the worst case scenario structural failure of the BEAM pressure vessel would turn out to be a "very bad day" for ISS. Jeff -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net |
#26
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Expandable modules??
"Jeff Findley" wrote in message ... To top this all off, I'm not even sure that what I pose as a "worst case scenario" truly is the "worst case scenario". Other failure modes might prove worse, depending on the details. This is why NASA and Bigelow Aerospace employ aerospace engineers, because this truly is "rocket science". A massive leak appears in the side, which puts a torque moment on the module which then rips out the CBM port on the station side leading to massive depressurization. Then the station tumbles out of control and lands on the next Soyuz waiting to be launched, destroying it and the pad and killing the crew and backup crew during a photo-op. (my stab at worst case.) Jeff -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net |
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