Railroad Towns


Earth resonant cyclers that regularly pass through near Earth space may be the “Railroads” to the asteroid belt. Such cyclers will also regularly fly by earth resonant asteroids in the main belt. The main belt asteroids that receive frequent supplies from earth would be trade centers. I call these centers “Railroad towns”.

Pictured below are the first cyclers that occurred to me:

3.5 year cyclers serving 3.5 year asteroids, 4 year cyclers serving 4 year asteroids etc.

At fly by, both cycler and main belt asteroid are moving at the same speed, but different directions. So the taxis between cyclers and mainbelt asteroids have large delta V requirements. A Hohmann transfer orbit is much better in terms of delta V. But it had been my opinion that Hohmann transfer orbits were non-resonant with either or both departure and destination orbits. Fly-bys between non resonant orbits are rare. So I had thought the delta V penalty was a necessary evil.

Then I received a letter from Chuck Yokota. It read in part:

Consider a "railroad town" in an orbit with a period of 3.2 years. This would be tangent to the orbit of a cycler ship in a 2-year orbit, for minimum fuel transfers of the shuttles. It would have a synodic period of 1.45 years when it would want to meet another cycler ship. Imagine 8 "railroad towns" spaced out on the same orbit 0.4 years apart from each other. Every time the cycler ship reached the orbit, it would meet the "railroad town" 5 places behind the one it met before, rotating through all 8 in 16 years. If there were eleven of these cycler ships, with the long axis of their orbits evenly distributed in different directions from the sun, every town would meet a cycler ship at each synodic period, and every cycler ship would meet a town every orbit.

Not only do Yokota's cyclers require much less delta V at asteroid fly-by, there is also less delta V during Earth fly-by. With my cyclers, the smallest reachable orbit is 3.5 years which needs a 3.5 year cycler. Yokota reaches the 3.2 year orbit with a 2 year cycler.

                                                Earth fly-by delta V      Asteroid fly-by delta V

Hop 3.5 year cycler                  5.6 km/sec                       11.6 km/s

Yokota 2 year cycler                 4.1 km/sec                        4.5 km/s

Since fuel requirements grow exponentially with delta v, these differences are profound.

Another advantage is more frequent Earth fly-bys. Below is an animation of Yokota's cyclers.

Revised September 12, 2007

Susan Casan has graciously translated the above page: http://webhostinggeeks.com/science/clowder-railroad-ht


Some of My Other Space Pages
Hohmann Launch Window Schedule
Gives launch windows for hohmann orbits from one planet to another.
Includes a spreadsheet where you can input departure and destination planets
as well as apogees and perigees of parking orbits about the planets.
Trip times, synodic periods and delta vees are calculated.
Shotgun Orbital Sims
Delta Vee Map
A whimsicly illustrated delta vee map to some near earth destinations.
The Case For Asteroids
Kuck Mosquitoes
A way to retrieve asteroidal resources with unmanned spacecraft.
The Case For Venus
The Hohmann launch windows to Venus form a gigantic pentagon.
The Earth to Venus Hohmann orbit has a period of 4/5 years.
This makes a nice system of cyclers possible.
The Oberth Effect

Outside Asteroid Links


Near Earth Asteroid Orbital Elements

A JPL list of Near Earth Asteroids along with their orbital elements.

You can sort by period, semi-major axis, perihelion and other helpful criteria.


Near Earth Asteroid Close Approaches

A JPL list of Near Earth Fly Bys.

You can sort by miss distance, relative velocity and other helpful criteria.


Mining The Sky

A book by planetary scientist John S. Lewis about

asteroidal and other space resources


Rain of Iron and Ice

A book by planetary scientist John S. Lewis about

the danger of impact from Near Earth Objects.
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