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From: dietz@SLB-DOLL.CSNET (Paul Dietz)
Newsgroups: net.space
Subject: Phobos to Earth Via Skyhook
Message-ID: <8601071449.AA14192@s1-b.arpa>
Date: Tue, 7-Jan-86 08:56:40 EST
Article-I.D.: s1-b.8601071449.AA14192
Posted: Tue Jan  7 08:56:40 1986
Date-Received: Wed, 8-Jan-86 23:43:07 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
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Using the data on Kevlar and on Phobos's orbit, I got the following
numbers:  a 3000 km long kevlar cable stretched out from Phobos will
accelerate payloads to ~ 1 km/sec after escape from Mars's gravity
well.  Even with a safety factor of 2, the cable will have a taper
of less than 2:1.  A cable 7500 km long will accelerate payloads
to 3.1 km/sec after escape, and will have a taper of 25:1 with a
safety factor of two.  Injection into a Hohmann orbit from Mars to
Earth would require 2.63 km/sec velocity change if Mars and Earth
were in circular orbits and in the correct positions (they aren't, but
I'll ignore that).  However, such an injection would require a velocity
change nearly parallel to the ecliptic; Phobos's orbit is inclined
25 degrees.  The direction of the orbit can be modified by throwing
the payload into a Mars intersecting orbit and using the subsequent
encounter to fix the orbit's inclination.