Design

of an

Interplanetary Cycler

This is a notebook for the design of a long-term ship to fly a continuous orbit between Earth and Mars or the asteroid belt.

There is also a design notebook for the orbit and the orbital simulation.

If I get really ambitious (or someone helps), we could simulate a Cycler so you could move about or even "live" on the ship: maybe a Mutli-User Virtual Environment (like these links to software) or something ...

Assumptions

Humans need some gravity for long-term health or comfort. This is not proved, but is a useful (and fun) constraint on the design. This assumption might be invalidated by some sort of hibernation.

Working Facts

Humans can't take more than about 4 RPM (awake).

Gravity must be at least 1/3 g to make liquids behave.

The standard acceleration of gravity (on Earth) is
(1) g = 9.80665 m/s²
from NIST Reference on Constants, Units, and Uncertainty

Centrifugal force is

(2)   F = m
v²
r
   = m
4π²r
T²
where m is mass, v is velocity, r is (turn) radius, and T is rotational period.

Ship Design

Arm Length

Our basic design is a central ship with two habitation modules at the end of long arms. The whole structure rotates to provide (pseudo)gravity in the habitation modules. Here is the calculation for the length of each arm.

Divide centrifugal force, Eq (1), by mass to get acceleration and set it equal to the fraction of Earthly gravitational acceleration (2) giving

f g =
4π²r
T²
where T is rotational period, r is the length of an arm, and f is the fraction of gravity we want to have. Multiplying by T² and dividing by g, we get
(5)   f T² =
4π²r
g
Our constants are nearly unity (π²/g = 1.0064), so as an approximation, we can write f T² = 4r. The following form uses this approximation.

T rotational period (s)
rotational speed (rpm)
f fraction of gravity (Currently hardwired at 1g.)
r length (m)

In comparison, the Eiffel Tower is 300 m, the Petronas Towers are 452 m, and the CN Tower is 553 m. So building a connecting arm under (static) tension should be no problem. (Maneuvering and acceleration stresses are another matter.)

Reference Links

The Lunar Institute of Technology has designs for an Explorer class star ship. We may be able to use information about consumables, mass, design, etc.

Up to my Interplanetary Cycler home page.

This page was created 22 January 2004 by Paul E. Black.

This page was last updated 20 June 2006.

This page's URL is http://www.geocities.com/p.black/Cycler/shipNotebook.html.

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