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Old June 3rd 06, 10:17 PM posted to sci.space.station
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Default Projected ISS reboost requirements?

wrote:
Dr John Stockton wrote:

For the present rate of drop of about 1 mm/s, the drag is equivalent to
about 0.05 micro-g; for M = 200 tons, that's 0.1 N implying 3 MN-s/yr.


So if the reboost is done with the Progress main engine with a nominal
Isp 305 s = Ve ~= 3,000 m/s that's 3e6/3000 ~= 1,000 kg/yr of
propellant, no? That seems low from what I remember of the Progress
fuel capacity, but I may be misremembering.

Remember, that fuel is also used for attitude control (progress are
normally tied into the ISS control system when docked) and the reboosts
are sometimes done with smaller, lower ISP engines.

According to http://www.skyrocket.de/space/space.html Progress M have
up to 850 kg of fuel in the refueling module, with a possible
additional 250kg of the progress' own fuel also available. Progress M1
can carry up to 1700 kg in the refueling module. In either case, they
can be launched with refueling tanks only partly loaded, to make room
for other cargo. Excess can also be transferred to the station (which
AFAIK was not loaded fully fuelled and currently has several thousand
KG of unused capacity).