Space Forum / Space Flight / March 2006

Cray74@gmail.com wrote:

Sun-"light" and star-"light" implies you are thinking of photonic
energy in and near the visible spectrum, and photovoltaics harvest and
conversion. There are several other useful energies in space, at least
in the inner solar system.

The solar wind is energetic enough that solar sails are contemplated.
The solar wind is a very broad spectrum of radiation and particles
blasted from the sun.

Aside from solar photovoltaics, thermal differences between sun exposed
and shaded are 500 degrees F of difference, which can power
thermoacoustic, stirling and kalina cycles for abundant power
generation. Technically this is the infrared spectrum and close to
visible, but it is not lumenous electronic energy harvest per se as PV
is.

The state of zero gravity allows for flywheel generation of power
through the Faraday Disc, alternately known under the names of
Homopolar Generator, Unipolar Generator, or by Nikola Teslas 1889
patent name "Dynamo Electric Machine".
http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=406968

Some force is required to initialize the homopolar generator, which may
be any of those above, but quite large electrical forces can be
extracted back out of the kinetic motion.
http://en.wikipedia.org/wiki/Homopolar_generator

http://en.wikipedia.org/wiki/Image:Homopolar_anu-MJC.jpg
"The worlds largest (500MJ) homopolar generator, was built by Sir Mark
Oliphant at the Research School of Physical Sciences and Engineering,
Australian National University. It was used as an extremely high
current source for experimentation from 1962 until its disassembly in
1986. It was capable of supplying currents of up to 2 megaamperes."

Gravitation force might be classified as "solar", loosely, as without
the sun there wouldn't be any objects in the "solar system", nor life
to know about it in any case. Gravitation is useful energy if near
massive objects, and tidal forces can be harvested for energy.

Spinning planets often have magnetic fields, as does the sun itself,
and these fields represent a reserve of energy to be tapped as large
bipolar generators. Tethers can generate energy from these magnetic
fields, although they are required to be inside an appreciable rotating
magnetic field to be useful. Again, spinning planets are an artifact of
being caputured in orbit by a sun, so ultimately the energy is some
kind of "solar" energy, of a
kinetic-gravitational-tidal-electromagnetic form.

There's a lot of kinetic energy in space from assorted sized objects in
motion. It is not "free", but none of the others are free any more than
energy from the Hoover Dam is free. You have to make investments to
harness kinetic energy, just as you make investments in PV or any of
the others.

Think of space as a vast Sahara desert with oases, each with their own
fountain of energy. If you know enough you can move between them
refilling your goatskin jugs with refreshing loads of energy of the
kind most useful to you, although you may have to go through a
conversion process from one type of energy to another before your
goatskin is properly topped off.

Solar, as in PV, is not so limited. You power is 1.3 times greater than
through the atmosphere on Earth, and you are high noon from dawn to
dusk getting peak power. At lEO, where the day-night cycle is 90
minutes, you get 3.5 times the power every 24 hours as you do on the
Equator. At GEO you get 7 times the energy in 24 hours.

You called on another to describe explicitly the energy in space. Now
live by your own standards and describe this "nuclear reactor" of few
tons.

Each meter of LEO-to-Lunar space has 1.35 kilowatts of energy. The best
PV goes up to 30-40% efficiency. Solar thermal probably goes up to 60%
efficiency. A hybrid solar PV-Thermal probably could achieve 90%
efficiency. The most plentiful thing in SPACE is SPACE. You can use all
the space you want: acres and acres, front-back-sideways-up-down.

There's nothing clumsy about PV. Mass is mass and it all obey's
Newton's physics, whether it be PV or mysteriously vague "nuclear
reactor".

Acres of PV are nothing in space. Solar sails are predicted to be
square miles in size. Earthlings are boggled by size. Solar PV is
easier to make in space than it is on Earth. Crystals of flawless
perfect lattice can be grown meters in diameter. Thin sliver
monocrystalline wafers can be grown, drawn out for miles.

I would make one just like he said. I would use the homopolar generator
as the power supply and generate electromagnetic fields to deflect
charged ions. That's all they could deflect, but that's all I need them
to deflect. I would use solid mass material to sunward to shield solar
storms of hard radiation, and that's 99.99% of anything you need to
worry about. The heavy particle cosmic rays background stuff passes
right through the Van Allen belts and the atmosphere today, as if it
wasn't even there, so it's no different in space without those.

Not a bad suggestion. Not a great suggestion either. Nobody is going to
the outer planets for a while yet, and there's still a few hundred
thousand people to get launched to LEO-GEO-L-5 before anybody will be
heading out, so it's not relevent to anything we need to be talking
about for the next ten or twenty years.

Jupiter, Saturn, and their moons have plenty of gravitational,
magnetic, chemical energy to fill up the goatskins, and from there one
has a better view of the oases further out for refilling the gas tank.
It's premature to be worrying about how to deal with Uranus. Let's see
what the lost fifth planet left us in the asteroid belt first before we
decide what we don't have enough of and what we don't need more of.

Deep space is great for nukes, and we can take all their atomic wastes
off their hands, and save their next 20,000 generations of kids from
standing guard over their father's mistakes until the end of time.

Both true.

Or you stick your station on one end of a very long cable and some big
weight (e.g. spent stage, empty tankage, or something) at the other end of
the cable and you spin the combination.  This would seem to be a possibility
for something like a manned Mars mission, where you really don't want your
astronauts spending the entire trip to Mars in zero gravity.  It would be
better if they were still used to 1G upon Mars arrival, so that their
muscles were still in peak condition.

Jeff