Re: SPACE: Cycler orbits

From: Louis Newstrom (
Date: Wed Feb 20 2002 - 05:42:32 MST

From: <>

> In a recent news article, someone made mention of a cycler orbit between
> Earth and Mars. The idea was to put a manned space station in such an
> so that it would "cycle" between encounters with Earth and Mars. This
> be a low cost way to ferry people, equipment, and supplies between
> The cycler orbit would need only a small amount of fuel for minor
> corrections -- once the station was put into it.

This idea seems great at first, but there are two downsides:

1) It wouldn't cut costs. The energy needed to go half-way to mars and
then the rest of the way will be at least equal to the whole trip. The
extra fuel needed to precicely dock with the cycler station will probably
make such a trip MORE expensive than a straight shot.

2) At a distance half-way to mars, the cycler would have an orbit of 517.6
days. Doesn't sound bad. But, as a result, it would line up with earth
only every 3.4 years, and with mars only every 2.1 years. Assuming the
average (half) wait for any arbitrary launch time, a trip to mars via the
cycler would take 2.7 years. Since mars aligns with earth every 2.1 years,
the cycler would slow down such trips. And as I pointed out, without saving
any money.

The reason such stations have been proposed in the past is not to save money
or energy, but to allow inadequate ships to get to mars. Assume a ship
cannot carry enough food. The advantage of a cycler would be that several
unmanned ships could be sent to rendevous with the cycler. Then when the
manned ship goes, there will be an oasis with food along the journey.
That's the reason to consider cyclers.

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