Mirrors versus diffuse reflection

In a message dated 6/5/01 4:15:19 AM Eastern Daylight Time,
hollroa@... writes:

<< Designing and building such a huge and complex magnetic confinement
system would be quite an achivement. But is it really likely to be easier
than simply reflecting the sunlight into transparent windows? I can see the
advantage of artificial lighting systems, when designing interstellar
colonies. But it is likely to be 200 years before we need them. In the
inner solar system, normal sunlight is plentiful and desperate measures
which involve huge glowing plasma's and complex containment systems are not
neccesary.
>>

There are benefits even if you stay in the inner Solar System, especially if
you want to mine the Asteroids, a fusion drive can get you around the Solar
System quite handily, then there is The Mars Run, an Island 3 sized cylinder
can provide luxury accomodations for 20 million passengers visiting Mars. A
lot is based on the Space colony simply being a place to live, like a fixed
city on Earth, but another purpose for building a space colony is to provide
transportation from point A to point B in the Solar System. Also fusion
reactors scale up quite nicely, one of the problems with fusion reactors
today is that we can't build them big enough for them to generate energy
efficiently.
Generally speaking, the larger the cross section of the fusing plasma, the
more efficient the reactor is, this is largely the result that the volume of
the fusing plasma increases as a cube function of the size of the reactor,
while the containment effort increases by the square of the size of the
reactor. The plasma on the inside of the fusion arc is contained by the
plasma on the outside of the fusion arc, only the outside plasma needs to be
contained by magnetic fields, but the interior plasma also produces energy,
so the thicker the cross section of fusion plasma, the more plasma there is
on the inside, and the more energy is produced in relation to containment
energy. Something the size of an Island three colony is a shoe-in for
producing a net energy surplus.
Most thermonuclear reactor designs produced to date are not that huge. The
ITER for example is only the size of a 10 story building, and most fusion
efforts are geared to achieving a breakthrough for a reactor of that size.
Creating a fusion reactor that is 20 miles long should be even easier
conceptially. The main difficulty is the economic resources that need to be
mustered to build it. If you talk to a fusion scientist, I'm pretty sure he
can come up with a working design. Changes are that the fusion powered Island
three could even beam surplus fusion power to Earth if in orbit. Large
structures are easier to build in orbit than on the ground as they require
less support material.

Tom Kalbfus