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#11
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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..... |
#12
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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. |
#13
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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 |
#14
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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 |
#15
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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 |
#17
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On the lasting importance of the SpaceX accomplishment.
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#18
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On the lasting importance of the SpaceX accomplishment.
In article 32fbdc15-236e-4bbe-a95a-
, says... ..... 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. So now you're an expert in structural fatigue? This could be an issue, but considering the loads experienced by the modules during launch, I'd think it would take quite a long time for such small loads to cause the sort of fatigue you're talking about. Please remember that ISS is in orbit and is experiencing microgravity conditions. This is compared to the 3 or so g's (plus a lot of vibrations) experienced by those same modules during launch. 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. You're speculating here. You have not done the analysis. Cite? 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 So where are the square holes in the structures on ISS? Besides, space (specifically microgravity) is *not* a challenging environment for structures. *Launch* (especially aboard the space shuttle) is a challenging environment for a structure which otherwise will experience microgravity conditions. Jeff -- " Ares 1 is a prime example of the fact that NASA just can't get it up anymore... and when they can, it doesn't stay up long. " - tinker |
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On the lasting importance of the SpaceX accomplishment.
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