Putting the ISS to some use at last. Maybe.

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Winston Blake
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Post by Winston Blake »

Paolo wrote:The author writes this...

"As any student of celestial mechanics can tell you, if you want to go somewhere in space, the best policy is to go directly there and not stop along the way, because stopping is a waste of precious fuel, time and treasure. Which is a pretty good description of the ISS, parked as it is in constant low Earth orbit. "

...then contradicts himself by writing this...

"The ISS is already in space; the amount of thrust it needs to go farther is a lot less than you might think."

If you're going to argue that orbital launches are great, it's kind of silly to argue that waylaying in orbit is dumb.
I don't see the problem. The second quote states that going from orbit to elsewhere is surprisingly easy, but doesn't say that it's a better option than going there directly.

I'm pretty sure he's alluding to the old saying that in terms of delta-v, 'once you're in orbit, you're halfway to anywhere'. This doesn't contradict the fact that it's a waste of delta-v to build up speed, then slow down and dock to a station, then build up speed again and then slow down at the destination.

However I can see how it could be useful to stop in orbit if you use your biggest launch vehicle to launch its max payload in fuel up there. You can then launch a max payload-worth of dry spaceship and combine the two in orbit, thus getting a big ship without a big new rocket.
Paolo
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Post by Paolo »

Winston Blake wrote:I'm pretty sure he's alluding to the old saying that in terms of delta-v, 'once you're in orbit, you're halfway to anywhere'. This doesn't contradict the fact that it's a waste of delta-v to build up speed, then slow down and dock to a station, then build up speed again and then slow down at the destination.
The delta-v required to maneuver in LEO is negligible (an order of magnitude less at least) compared to the 8 or so km/s you need to get there in the first place. You can cut this down considerably by timing your launch such that you intercept at final velocity the ISS or some other destination.
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Winston Blake
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Post by Winston Blake »

Paolo wrote:The delta-v required to maneuver in LEO is negligible (an order of magnitude less at least) compared to the 8 or so km/s you need to get there in the first place. You can cut this down considerably by timing your launch such that you intercept at final velocity the ISS or some other destination.
Yeah but if you're going to Mars or something, surely you don't need to 'get to LEO in the first place'. You can just plan to go hyperbolic ASAP. Also, adding launch timing requirements sounds like a disadvantage to me.
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