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Slingshot Smile

 "Jeff Davis" writes:
> NASA is putting money into Momentum-eXchange/Electrodynamic Reboost 
> tether technology -- MXER for short -- an innovative concept that if 
> implemented would station miles and miles of cart-wheeling cable in 
> orbit around the Earth. Then, rotating like a giant sling, the cable 
> would swoop down and pick up spacecraft in low orbits, then hurl them 
> to higher orbits or even lob them onward to other planets.

Reminds me of an April Fool article I circulated ten years ago. This smile
comes courtesy of Amsat-UK

Begin quote

Phase-3E News
Embargoed for automatic release at 0001 utc 01Apr93

With hardware plans for Phase-3D now more or less stabilised, Amsat thoughts
are turning to Phase-3E and the conceptual design phase is near enough to
completion to be published.

Current plans are for a bi-modular system comprising earth-orbit and inter-
planetary modules linked by a tether. The composite will take the usual GTO
launch by Ariane V601 and, once deployed from the launch vehicle, the modules
will be separated by a simple spring mechanism to the extent of the tether
(264 feet). Now we come to the interesting bit because in the past the Phase-3
series have fired kick motors at apogee for orbit changes ... not so this time
(not yet anyway). Magnetic theory says that if a current is passed through the
tether at perigee (where the Earth's magnetic field is strongest) then an
electric motor effect will take place and the composite will spin. This effect
will cause a cycle whereby alternating modules will pull their partner up in
altitude by the length of the tether and, at a composite spin rate of 20 rpm,
this should result in a rise of perigee altitude of (30 min x 20 rpm x 264 ft)
90 miles per perigee pass. So in five days (10 orbits) the composite will have
a relatively safe perigee altitude of a thousand miles or so (still at about
seven degrees inclination).

At this point the tether control electronics will be put into pulse (rather
than constant current) mode and work with the onboard magnetometer unit in
order to increase the spin rate and change its direction. Once enough inertia
has been developed, the far-end module will cut itself free and centrifugal
force will fling it into a trans-Uranus-injection flight path; interaction
from the module release will also affect P3E's orbit, raising perigee by
another thousand miles or so. Only after the interplanetary module has been
released will the standard kick motor be fired to place P3E into its final
orbit; it doesn't have enough delta-v to propel the mass of both modules.

The EARTH-ORBIT MODULE will then deploy a space mirror along the tether. Spin
rate is expected to be low due to the low mass of the mirror, 10 rpm is
expected and, since the mirror will be polished on both sides, reflection of
light towards Earth is expected to occur 20 times per minute. Thus visual
observations can be used as well as doppler ranging in order to determine the
final orbit characteristics (a sort of phantom flasher); a by-product of the
effect means that some solar panels (which would have been in shadow) will
receive extra illumination. The Earth-orbit module will contain all the usual
bits, transponders on all the usual bands etc. but the tether will also be used
to enhance operations in two ways. Firstly, as already explained, as the tether
rotates it cuts the Earth's lines of magnetic force and in the un-pulsed mode
it acts as a generator, thereby providing a power source to augment that
provided by the solar cells. Secondly, the tether will be end-fed through a
specially developed hybrid ATU and cavity system allowing it to be used for a
new transponder, denominated mode-Z, which will receive between 3.7 to 3.8 MHz
and retransmit between 1.9 to 2 MHz enabling Amsat-UK 80m nets to be heard
world-wide. The mirror unit can also be configured as a solar sail to adjust
orbit characteristics in case Solar and Lunar gravity effects adversely affect
the orbit (as happened with Oscar-13).

In the meantime the INTERPLANETARY MODULE will proceed autonomously and carry
out its own series of experiments. In the near-Earth phase of its mission it
will transmit telemetry and make measurements of the spatial environment as an
aid to planning for future missions. Once it has travelled about 20 million
miles it will switch over to SETI mode (also known as pseudo-DOVE mode) and
transmit a peace message for the rest of its interplanetary cruise. Sponsors
are still required for this mode, payment required in Escudos, Bolivars, or
any other foreign currency convertible in Switzerland. On arrival at its
destination it will go into orbit and, since power will be limited, transmit
telemetry twice per orbit (using 300bps packet). In addition to information
about its local environment, rf occultation and doppler data will enable you
to measure and determine many things about Uranus. Piles of data are expected.

End quote. 
Remember this was written in 1993 !!! Amsat-UK beats NASA again

Richard W L Limebear G3RWL
FOC # 1188

          So many beautiful girls ..... (sob) so little time
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