by kovil » Tue Mar 20, 2007 7:44 pm
Here's a little about the ISS,
I'm curious, what drove the decision to place the ISS in its current altitude range (~220 statute miles, iirc)? Is it simply a tradeoff between atmospheric drag and ability to deliver payload? Placing the station in a 300+ mile high orbit, like that of the Hubble, would certainly reduce drag and hence reduce the number of reboosts needed. On the other hand, NASA already suffered a significant hit by putting the station in a 51.6 degree inclination orbit, and I'm guessing that reaching a higher orbit of that inclination would not be feasible without cutting payload capacity significantly. Would the space station have been placed higher had it been in a 28.5 degree inclination orbit? Also, I forget, how high can a manned station go before radiation exposure becomes unacceptable? I assume it's wherever the inner Van Allen belt starts...
In reply to:
because it has to be serviced by the russian's who launch from baikonur... in fact Mir was on the same altitude/inclination.
To elaborate a bit, it's because it has to be serviced by Soyuz rockets from Baikonur and Shuttles from Florida. The altitude is actually lower than what the Russians would prefer. It's more efficient to get to ISS from Baikonur (which is at 51 degrees north latitude, and it's not a coincidence that that's the same as the ISS's orbital inclination) so they can afford to fly a bit higher into that inclination. If the ISS is higher, it doesn't need to be reboosted as often. For this reason, while the Shuttle was unavailable for the last two years, they pushed the ISS into a higher orbit, out of the Shuttle's reach. They allowed it to drop back down in time for STS-114, of course.
So the orbit is basically the best compromise between Soyuz rockets from Baikonur and Shuttles from KSC.
The Russians actually originally intended Mir-2 (the core of which ultimately became Zvezda, during its greatly extended planning phase) to be in an orbit which Shuttles cannot achieve. It would've been a polar orbit, serviceable by Soyuz rockets launched from the far north site of Plesetsk. This was intended to resolve the problem of renting space from a foreign country after the breakup of the Soviet Union and the loss of Kazakhstan. But for a variety of reasons this never became a reality.
-------------------------------------------------------------
Understanding is a three-edged sword. -- Kosh
= = =
The bright spot that looks like it is inside the diameter of the Moon, may not actually be inside it. The Moon may oblate just enough to miss it, by atmospheric diffraction. It might be Venus. Tho it does look suspiciously like some kind of man-made object, plane or satellite. How far away is a real difficult row to hoe.
Here's a little about the ISS,
I'm curious, what drove the decision to place the ISS in its current altitude range (~220 statute miles, iirc)? Is it simply a tradeoff between atmospheric drag and ability to deliver payload? Placing the station in a 300+ mile high orbit, like that of the Hubble, would certainly reduce drag and hence reduce the number of reboosts needed. On the other hand, NASA already suffered a significant hit by putting the station in a 51.6 degree inclination orbit, and I'm guessing that reaching a higher orbit of that inclination would not be feasible without cutting payload capacity significantly. Would the space station have been placed higher had it been in a 28.5 degree inclination orbit? Also, I forget, how high can a manned station go before radiation exposure becomes unacceptable? I assume it's wherever the inner Van Allen belt starts...
In reply to:
because it has to be serviced by the russian's who launch from baikonur... in fact Mir was on the same altitude/inclination.
To elaborate a bit, it's because it has to be serviced by Soyuz rockets from Baikonur and Shuttles from Florida. The altitude is actually lower than what the Russians would prefer. It's more efficient to get to ISS from Baikonur (which is at 51 degrees north latitude, and it's not a coincidence that that's the same as the ISS's orbital inclination) so they can afford to fly a bit higher into that inclination. If the ISS is higher, it doesn't need to be reboosted as often. For this reason, while the Shuttle was unavailable for the last two years, they pushed the ISS into a higher orbit, out of the Shuttle's reach. They allowed it to drop back down in time for STS-114, of course.
So the orbit is basically the best compromise between Soyuz rockets from Baikonur and Shuttles from KSC.
The Russians actually originally intended Mir-2 (the core of which ultimately became Zvezda, during its greatly extended planning phase) to be in an orbit which Shuttles cannot achieve. It would've been a polar orbit, serviceable by Soyuz rockets launched from the far north site of Plesetsk. This was intended to resolve the problem of renting space from a foreign country after the breakup of the Soviet Union and the loss of Kazakhstan. But for a variety of reasons this never became a reality.
-------------------------------------------------------------
Understanding is a three-edged sword. -- Kosh
= = =
The bright spot that looks like it is inside the diameter of the Moon, may not actually be inside it. The Moon may oblate just enough to miss it, by atmospheric diffraction. It might be Venus. Tho it does look suspiciously like some kind of man-made object, plane or satellite. How far away is a real difficult row to hoe.