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Express supply..
Now they can resupply in 6 hours, one assumes only if the orbit and pad are
in the correct relationships, it seems that its not that difficult after all. I'm sure the old reason for not doing this was due to excessive fuel use to achieve it in relation to the more leisurely way. Was or is this true, or was it just an excuse? Brian -- Brian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: __________________________________________________ __________________________________________________ __________ |
#2
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Express supply..
On Sun, 5 Aug 2012 09:51:17 +0100, "Brian Gaff"
wrote: Now they can resupply in 6 hours, one assumes only if the orbit and pad are in the correct relationships, it seems that its not that difficult after all. I think higher latitudes have more opportunities, because the Earth's rotation is drawing a smaller circle up that far north, and the distance between the pad and the orbit increases more slowly. You still need sophisticated avionics, and only the recent upgrade to the digital flight control system of Soyuz/Progress made it feasible. Brian |
#3
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Express supply..
On 8/5/2012 1:51 AM, Brian Gaff wrote:
Now they can resupply in 6 hours, one assumes only if the orbit and pad are in the correct relationships, it seems that its not that difficult after all. I'm sure the old reason for not doing this was due to excessive fuel use to achieve it in relation to the more leisurely way. Was or is this true, or was it just an excuse? the old obstacle for doing this was lower iss orbit. the iss orbital altitude was intentionally reduced to make it reachable by space shuttle. now, with shuttle out of the picture, the iss was transferred to a notably higher orbit, making it much easier to shoot progress ships straight to the iss. |
#4
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Express supply..
"Korben Dallas" wrote in message ...
On 8/5/2012 1:51 AM, Brian Gaff wrote: Now they can resupply in 6 hours, one assumes only if the orbit and pad are in the correct relationships, it seems that its not that difficult after all. I'm sure the old reason for not doing this was due to excessive fuel use to achieve it in relation to the more leisurely way. Was or is this true, or was it just an excuse? the old obstacle for doing this was lower iss orbit. the iss orbital altitude was intentionally reduced to make it reachable by space shuttle. now, with shuttle out of the picture, the iss was transferred to a notably higher orbit, making it much easier to shoot progress ships straight to the iss. Cite for that? Since August of last year to to now it's gone from about 382 kilometers to approximately 402 kilometers, a 20km boost. During the shuttle supported part of program height ranged from approximately 332 km to as high as 400 km. I'm not sure 402km is "substantially higher" And I'm not clear how that would make it easier for Progress (which would suffer similar upmass losses at higher altitudes). Thanks. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net |
#5
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Express supply..
JF Mezei was thinking very hard :
Greg (Strider) Moore wrote: During the shuttle supported part of program height ranged from approximately 332 km to as high as 400 km. This in itself isn't enough information. Consider the case where the 400km was achieved only while the shuttle was grounded, and during normal shuttle ops, the altitide varied much less above 332. And if they no longer have to let the ISS altitide drop to allow shuttle visits, it would mean fewer reboosts since the station would be staying at higher altitude where there is less drag. Average altitude might be a better metric to compare ISS during and after shuttle. And I'm not clear how that would make it easier for Progress (which would suffer similar upmass losses at higher altitudes). My guess is that it is fuel savings that are factored in of there need to be fewer reboosts. I seem to recall that the Shuttle was giving bigger reboosts to ISS than could be done with other means. Perhaps the average altitude was raised because the big boot ... er, boost ... wasn't available anymore. /dps -- Who, me? And what lacuna? |
#6
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Express supply..
On Fri, 10 Aug 2012 22:10:44 -0400, JF Mezei
wrote: With the higher ISS altitude, and the lowest acceptable progress altitude after launch, assuming worst case scenario for position of ISS at progress launch time, how long would it take for the progress to lap the station to get itself into the right position to raise orbit to ISS' and dock without delay ? aka: with the techniques used for the 6 hour launch-to-dock, what is the worst case scenario ? 7 hours ? 12 hours ? 24 hours ? If I recall correctly, it was reported it could be either a 6 hour rendezvous or a standard 50-ish hour rendezvous, but there wasn't any in-between. Brian |
#7
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Express supply..
On Fri, 10 Aug 2012 17:24:47 -0700, Korben Dallas
wrote: the old obstacle for doing this was lower iss orbit. the iss orbital altitude was intentionally reduced to make it reachable by space shuttle. now, with shuttle out of the picture, the iss was transferred to a notably higher orbit, making it much easier to shoot progress ships straight to the iss. I think the altitude difference has actually been pretty marginal since the Shuttle's return to flight in 2005/2006. They did let the Station get a little lower than normal for a couple of the real heavyweight flights like Kibo and S6, but that wasn't constant. There were several reports at the time of the launch that it was the new TsVM-101 digital flight computer (introduced on Soyuz TMA-01M in Oct 2010) that made this possible. Now that the TsVM-101 computer has a few flights under its belt, Russia was ready to try rapid rendezvous. Brian |
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