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

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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

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.

"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.



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Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net

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