Re: SubOrbital Towers..

From: Amara Graps (
Date: Sat Mar 18 2000 - 10:17:32 MST

From: Spike Jones <>, Thu, 16 Mar 2000

>Mars would be good for an isosynchronous cable tho.

??!! Really? Why?

Did you forget about Phobos?

I calculated where is the location of Mars synchronous orbit:

r = ( (T^2 G M_m) / (4 pi^2) )^{1/3} meters

T = rotation period of Mars = 24.6 hr
M_m = Mars mass = 6.4x10^{23} kg
G = gravitational constant

and so, if I made no mistakes, I get:

==> r = 2.0x10^7 meters = 5.9 * R_mars

(R_mars = Mars radius = 3.4 x10^6 meters)

Phobos orbits at 2.76 * R_mars, (i.e. well inside of
the planet's synchronous orbit radius), with a period of .3 days.

Do you have a plan to move Phobos' orbit?

And when one looks at the "near-Mars" orbital environment, it is a
good idea to keep the Mars dust rings at the back of your mind.

You may be wondering: What are those dust rings?

The Martian dust rings have the dubious distinction of being the
longest studied planetary rings whose existence still has to be

(If you search on "Mars Dust Rings" in NASA ADS, you'll find many
many theoretical papers.)

These (hypothetical) rings are caused by the continuous bombardment
of the Martian moons: Phobos and Deimos by the interplanetary flux
of micrometeroids, which produce ejecta, a part of which can form
tenuous rings of ~10-100 micron sized particles, and those rings
could live thousands of years in circummartian orbits.

The rings are located in roughly the same orbits (the rings are
skewed a bit off-center) as Phobos and Deimos (Deimos orbits at 6.9
* R_mars).

Therefore, your tower in Mars synchronous orbits looks to me that it
is in a bit of danger from Phobos and its hypothetical ring.


Amara Graps | Max-Planck-Institut fuer Kernphysik
Interplanetary Dust Group | Saupfercheckweg 1
+49-6221-516-543 | 69117 Heidelberg, GERMANY *
        "Never fight an inanimate object." - P. J. O'Rourke

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