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#21
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On the lasting importance of the SpaceX accomplishment.
On Jul 14, 5:52*am, Thomas Womack
wrote: In article , Fred J. McCall wrote: I'm sorry, but that displays a degree of insanity that I just find impossible to believe. *Suppose it comes down on Paris or London. *How many people does it kill, what does it destroy, and what does all that cost once all the liability suits are settled. *You're talking almost a million tons of stuff coming in at reentry velocities. If the Space Station weighed a million tons then we've already won. It weighs four hundred tons; a rock that size comes in at interplanetary velocity most years, mostly burns up, and is noticed only in internal publications of ballistic-missile defence organisations. *There's an atmosphere in the way; almost everything burns up almost entirely, and the rest hits no harder than a component falling off a plane at takeoff. ISS would have been cheaper as a US-only effort. *Almost every major program costs more if you involve other governments. It would have been very much cheaper, yes, because it wouldn't have happened; it escaped cancellation as being a reasonably impressive way of keeping Russian rocket scientists from departing en-masse. Tom the re entry speed of a asteroid is normally very fast and most of it burns up the re entry speed of ISS modules will be far slower, and structural parts stronger than a asteroid as such a out of control ISS is a much larger hazard than a asteroid, espically since the ISS ground track is over the most populated part of our world |
#22
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On the lasting importance of the SpaceX accomplishment.
On 14/07/2012 14:52, Thomas Womack wrote:
In , Fred J. wrote: I'm sorry, but that displays a degree of insanity that I just find impossible to believe. Suppose it comes down on Paris or London. How many people does it kill, what does it destroy, and what does all that cost once all the liability suits are settled. You're talking almost a million tons of stuff coming in at reentry velocities. If the Space Station weighed a million tons then we've already won. It weighs four hundred tons; a rock that size comes in at interplanetary velocity most years, mostly burns up, and is noticed only in internal publications of ballistic-missile defence organisations. There's an atmosphere in the way; almost everything burns up almost entirely, and the rest hits no harder than a component falling off a plane at takeoff. ISS would have been cheaper as a US-only effort. Almost every major program costs more if you involve other governments. It would have been very much cheaper, yes, because it wouldn't have happened; it escaped cancellation as being a reasonably impressive way of keeping Russian rocket scientists from departing en-masse. Tom Re-entry is an interesting subject alright - comparing a nearly circular orbit re-entry like the ISS or other (man made) satellites with a much more direct straight-into the atmosphere entry like Shoemaker-Levy. Velocities and angles and rates of burning up - makes my head spin with all the possibilities. -- T |
#23
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On the lasting importance of the SpaceX accomplishment.
On Fri, 13 Jul 2012 20:55:55 -0700 (PDT), bob haller
wrote: lets not forget that the stations modules have a finite lifetime. you can replace all sorts of parts on a old car but that doesnt make it new, and breakdowns on old vehicles are to be expected. So do B-52s, KC-135s, T-38s and P-3s, all of which are still in active military service over 50 years after they were delivered. so unless all parties involved are prepared to begin replacing entire modules one day something critical will beak down with possibly disasterous results. Ah, Bob. This wouldn't be sci.space without one of your "THEY'RE ALL GONNA DIE!" fear-mongering at least once a week. the station is now past its design life....... Nope. 2015. 15 years guaranteed on-orbit life, which is more of less through 2015. But most of the hardware is directly descended from Freedom designs, which were specced for 30 years. On the Russian side, there's not much difference between the ISS modules and Mir modules, and Mir went a decade past its design life, only really be hampered by careless fires set off inside and by the Russians ramming it with a Progress freighter in a very-poorly conceived budget-saving demo. et it age gracefully and not run it till it kills. Of course, it can and almost certainly will be periodically inspected by astronauts and cosmonauts to make sure nothing is about to "kill", and if a show-stopper appears, then it can be deorbited. But if it is earning its keep, there's no reason to deorbit it prematurely. incidently a out of control station will tumble shedding modules as it tumbles, spreading them over its entire ground track . many parts will survive re entry, the ground track is mostly over populated areas... That's why Station has two independent control methods... The USOS's side and the Russian side's. That doesn't include Progress or ATV, which can also do the job. ISS is not SkyLab. a station breaking up will cause mass panic, espiically if modules and parts start coming down in populated areas........ 90% or so chance it would come down at sea or in unpopulated areas (deserts), though. Brian |
#24
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On the lasting importance of the SpaceX accomplishment.
lets not forget that the stations modules have a finite lifetime. you can replace all sorts of parts on a old car but that doesnt make it new, and breakdowns on old vehicles are to be expected. So do B-52s, KC-135s, T-38s and P-3s, all of which are still in active military service over 50 years after they were delivered. Brian if the modules could be returned to earth and completely refurbished this is true. in the case of military jets only the airframes havent been changed. all other parts have perodically upgraded or totally replaced..... |
#25
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On the lasting importance of the SpaceX accomplishment.
Thomas Womack wrote:
Fred J. McCall wrote: I'm sorry, but that displays a degree of insanity that I just find impossible to believe. Suppose it comes down on Paris or London. How many people does it kill, what does it destroy, and what does all that cost once all the liability suits are settled. You're talking almost a million tons of stuff coming in at reentry velocities. If the Space Station weighed a million tons then we've already won. It weighs four hundred tons; a rock that size comes in at interplanetary velocity most years, mostly burns up, and is noticed only in internal publications of ballistic-missile defence organisations. There's an atmosphere in the way; almost everything burns up almost entirely, and the rest hits no harder than a component falling off a plane at takeoff. And your big rocks are pretty solid. I expect that hollow "rocks" break up a lot earlier in their entry. -- I used to own a mind like a steel trap. Perhaps if I'd specified a brass one, it wouldn't have rusted like this. |
#26
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On the lasting importance of the SpaceX accomplishment.
On Sat, 14 Jul 2012 09:30:41 -0700 (PDT), bob haller
wrote: lets not forget that the stations modules have a finite lifetime. you can replace all sorts of parts on a old car but that doesnt make it new, and breakdowns on old vehicles are to be expected. So do B-52s, KC-135s, T-38s and P-3s, all of which are still in active military service over 50 years after they were delivered. if the modules could be returned to earth and completely refurbished this is true. It is true regardless. in the case of military jets only the airframes havent been changed. all other parts have perodically upgraded or totally replaced..... The airframes are likewise the only part of ISS modules that can't be changed. Pretty much everything else can be changed out. It was designed that way deliberately, Bob. Brian |
#27
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On the lasting importance of the SpaceX accomplishment.
......
The airframes are likewise the only part of ISS modules that can't be changed. Pretty much everything else can be changed out. It was designed that way deliberately, Bob. Brian Dockings of visiting spacecraft, thermal cycles during each orbit of Earth, reboost maneuvers and crew exercise can affect the space station's structural health. Without the ability to inspect the shell of the craft, like airplane engineers would do on Earth, NASA must use computer models to predict how cracks and deformities propagate in space. So theres no way to directly inspect the modules, a not anticipated issue may appear, similiar to the square window issues in the first commercial airliner. plus space is a very challenging environment |
#28
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On the lasting importance of the SpaceX accomplishment.
On Sat, 14 Jul 2012 12:48:44 -0500, Brian Thorn wrote:
On Sat, 14 Jul 2012 09:30:41 -0700 (PDT), bob haller wrote: lets not forget that the stations modules have a finite lifetime. you can replace all sorts of parts on a old car but that doesnt make it new, and breakdowns on old vehicles are to be expected. So do B-52s, KC-135s, T-38s and P-3s, all of which are still in active military service over 50 years after they were delivered. if the modules could be returned to earth and completely refurbished this is true. It is true regardless. in the case of military jets only the airframes havent been changed. all other parts have perodically upgraded or totally replaced..... And once again, Bob, you get it wrong. All of Above name aircraft have been through a continual process of inspection, IRAN, overhaul and rebuild for decades. About the only thing still original on a KC-135R (Especially after Pacer Crag) is the data plate. B-52s even more so, even though both types have relatively few hours on them for their ages - all that time spent on alert during the Cold War. The T-38s have also been through several complete rebuilds. The P-3s not so much, but they go through an intense (almost Space Shuttle) level of mandatory inspection and special maintenance (Such as fresh-water high pressure washdowns after each flight - the corrosion from flying over the oceans for all those years is a tremendous problem.) It's interesting that you didn't mention other contemporaneous types, the C-141B (Which got its wings flown off during Desert Shield/Desert Storm), and the Handley Page Victor (Supporting the Black Buck operations in the Falklands War did them in) It's not just the years, it's the mileage. How does this relate to the ISS? You can't pull a full inspection, taking apart the structure and performing Non-Destructive Testing on it. We don't have the knowledge base yet to be able to predict what the long-term effects of the space environment are going to be. Any predictions now are guesses, surmise, and prejudice. The airframes are likewise the only part of ISS modules that can't be changed. Pretty much everything else can be changed out. It was designed that way deliberately, Bob. What everybody seems to miss, or ignore, is that the ISS just being there is a vital part of long endurance spaceflight. If we can't build structures, power systems, environmental systems, and all the rest that can't be trusted beyond the next scheduled resupply flight, than anything like a mission beyond the Moon is right out. Mir was jack-legged together - the crew spent most of their time (Especially in the later years) working at not dieing. The Russians, and we, learned a lot, but not enough. ISS's history shows that we still have a lot to learn. That's going to be the big takeaway, not the Classic Space Nerd goals of large semiconductor wafers and Zero-G sex. -- Pete Stickney Failure is not an option It comes bundled with the system |
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On the lasting importance of the SpaceX accomplishment.
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