RFI: Calculated orbital decay rate of an unbooster ISS?

....Has anyone done any estimates of roughly how long ISS could remain
in orbit without any boosts from the Shuttle, Soyuz or Progress
resupply missions? The issue has come up over on a BSG group, and I
actually haven't been able to find anything on the NASA sites about
this.

OM
--
]=====================================[
] OMBlog - http://www.io.com/~o_m/omworld [
] Let's face it: Sometimes you *need* [
] an obnoxious opinion in your day! [
]=====================================[

OM wrote:
...Has anyone done any estimates of roughly how long ISS could remain
in orbit without any boosts from the Shuttle, Soyuz or Progress
resupply missions? The issue has come up over on a BSG group, and I
actually haven't been able to find anything on the NASA sites about
this.

Depends on where the station is within the reboost cycle, but IIRC it's
a minimum of 180 days.

On Jun 17, 4:13 pm, OM wrote:
...Has anyone done any estimates of roughly how long ISS could remain
in orbit without any boosts from the Shuttle, Soyuz or Progress
resupply missions? The issue has come up over on a BSG group, and I
actually haven't been able to find anything on the NASA sites about
this.

I seem to recall something about that from Post-Columbia days, when
some of the end-time scenarios were being sketched. I don't recall
that there were any numbers published, though.

/dps

Hard to say because if you really are going to not resupply the station, and
presumably not crew it, then you need to say if it will be controlled or
left to its own devices. I mean the Gyros would need de saturating for the
continuous attitude control. Power would suffer without it. If you manage
the gyros well, fuel usage could be quite low, nd drag kept as low as
possible.

If tumbling were allowed, I'd suggest some structural failure long before
you started to get burn up.

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"OM" wrote in message
...
...Has anyone done any estimates of roughly how long ISS could remain
in orbit without any boosts from the Shuttle, Soyuz or Progress
resupply missions? The issue has come up over on a BSG group, and I
actually haven't been able to find anything on the NASA sites about
this.

OM
--
]=====================================[
] OMBlog - http://www.io.com/~o_m/omworld [
] Let's face it: Sometimes you *need* [
] an obnoxious opinion in your day! [
]=====================================[

Jorge R. Frank wrote:

Depends on where the station is within the reboost cycle, but IIRC
it's a minimum of 180 days.

Once all eight solar panels are on it (there are six on it now), its
drag goes up, and it takes more reboosts to maintain altitude.
Mass also increases with the new modules that are being added to it, and
that doesn't help either with the reboost energy needed to maintain it
in orbit.
It was designed to use the Shuttle OMS burns to lift its orbit on fairly
frequent visits to it, and without further Shuttle missions to the ISS
after its retirement, it's going to be a bit hard-pressed to keep it
from reentering, as Progress cargo loads will need to be cut to give
them enough reboost fuel.
ESA's Jules Verne may be the only thing that keeps it viable in this
regard after Shuttle retirement.

Pat

On Wed, 18 Jun 2008 02:43:25 -0500, Pat Flannery
wrote:

Jorge R. Frank wrote:

Depends on where the station is within the reboost cycle, but IIRC
it's a minimum of 180 days.

Once all eight solar panels are on it (there are six on it now), its
drag goes up, and it takes more reboosts to maintain altitude.

....And then there's the 11-year cycle to contend with, which is what
helped kill Skylab early *and* helped kill CB Radio when the fad
finally started to decline thanks to all the skip killing local
traffic.

....So what do you say, Jorge? Worst case being ~160 days, then?

OM
--
]=====================================[
] OMBlog - http://www.io.com/~o_m/omworld [
] Let's face it: Sometimes you *need* [
] an obnoxious opinion in your day! [
]=====================================[

"Pat Flannery" wrote in message
one...


Jorge R. Frank wrote:

Depends on where the station is within the reboost cycle, but IIRC it's a
minimum of 180 days.

Once all eight solar panels are on it (there are six on it now), its drag
goes up, and it takes more reboosts to maintain altitude.
Mass also increases with the new modules that are being added to it, and
that doesn't help either with the reboost energy needed to maintain it in
orbit.


True, but higher density helps reduce the decay rate.


It was designed to use the Shuttle OMS burns to lift its orbit on fairly
frequent visits to it, and without further Shuttle missions to the ISS
after its retirement, it's going to be a bit hard-pressed to keep it from
reentering, as Progress cargo loads will need to be cut to give them
enough reboost fuel.
ESA's Jules Verne may be the only thing that keeps it viable in this
regard after Shuttle retirement.

Pat



--
Greg Moore
SQL Server DBA Consulting Remote and Onsite available!
Email: sql (at) greenms.com http://www.greenms.com/sqlserver.html

On Wed, 18 Jun 2008 02:43:25 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in
such a way as to indicate that:



Jorge R. Frank wrote:

Depends on where the station is within the reboost cycle, but IIRC
it's a minimum of 180 days.

Once all eight solar panels are on it (there are six on it now), its
drag goes up, and it takes more reboosts to maintain altitude.
Mass also increases with the new modules that are being added to it, and
that doesn't help either with the reboost energy needed to maintain it
in orbit.

No, but more mass reduces the number of reboosts needed.

On Jun 18, 3:43*am, Pat Flannery wrote:
Jorge R. Frank wrote:


It was designed to use the Shuttle OMS burns to lift its orbit on fairly
frequent visits to it, and without further Shuttle missions to the ISS
after its retirement, it's going to be a bit hard-pressed to keep it
from reentering, as Progress cargo loads will need to be cut to give
them enough reboost fuel.
ESA's Jules Verne may be the only thing that keeps it viable in this
regard after Shuttle retirement.

Pat

Incorrect. The shuttle OMS has never been used to reboost the ISS,
nor was the ISS designed for it. The shuttle SOMETIMES does an RCS
reboost when it has surplus propellant. The ISS was designed to be
reboosted by Progress provided propellant from the beginning with the
Progress or the SM engines being used. The ATV flights are a bonus,
they do reduce the number of progress flights but the ISS could
survive without them
BTW, ATV is the ESA's resupply vehicle, Jules Verne is just the name
of the first one.

Jorge R. Frank wrote:

Depends on where the station is within the reboost cycle, but IIRC it's
a minimum of 180 days.


Does this mean that in worse case scenario, the ISS would burn up 180
days after the last reboost ?

Or is this more of a case that with more than 180 days between reboosts,
the amount of delta V needed to bring it back to a normal orbit would
exceed a single Progress/Shuttle's reboost capability ?