Re: SPACE: Cycler orbits

From: Forrest Bishop (
Date: Wed Feb 20 2002 - 14:20:27 MST

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Subject: Re: SPACE: Cycler orbits

> Louis Newstrom writes:
> >> I'm not sure about the latter claim. After all, if the cycler station was
> >> more like a storage depot, each individual trip to it might use a lot less
> >> fuel than a straight shot to Mars. Why? The mass would be smaller for
> > the
> >> ship docking to the cycler station.
> >
> > Imaging a station that orbits in such a way that it goes near earth and
> > mars. (We'll call this the "cycle orbit".) Sending a ship to rendevous
> > with the cycler station is EXACTLY the same as putting the shp in the "cycle
> > orbit". You have gained nothing (energy-wise) by having a station already
> > orbiting at that same spot.
> I see. Good old laws of physics...
> >> The idea is, I think, to use the cycle more as a cheap way to ferry
> > supplies
> >> and maybe people back and forth. One can make several small trips to a
> >> cycler station -- rather than one big one to the station or the
> > destination.
> >
> > True. But the energy cost per item remains the same. You are just
> > dividing that energy cost among several trips.
> The total cost of all the trips might be the same or higher as one big trip,
> but the fact is we have small rockets right now and small payloads. It's
> kind of like the poor man's choice of buying one serving of rice at a time
> instead of a months' supply...
> > A similar but different scenario is to use an asteroid. Instead of
> > "landing" on the asteroid, you just get in the way and "crash" on the
> > asteroid. In this way, you don't have to expend the energy to match speeds.
> > (You just have to have enough padding to survive the crash.) This would
> > eventually change the asteroid's orbit after many crashes, but the time to
> > do that might be years or centuries.
> An interesting idea. We'd also have to know about the particular asteroid
> -- depending on the goals here. After all, Eros appears to be covered with
> dust and small rocks. Impacting it might result in a lot material being
> kicked up -- a hazard to many operations.

A variation on this is to sling loose regolith into the path of the oncoming spacecraft, a crude particle beam made of (sifted)
dust. G-loads are then much lower, delta v's may reach upwards of 1 km/sec depending on the accuracy of the slinger. The
spacecraft's ablation shield would have to be able to withstand this 'dust atmosphere' re-entry.


Forrest Bishop
Chairman, Institute of Atomic-Scale Engineering

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