money is in short supply

Am 25.02.2011 18:14, schrieb Al Globus:
>
> On Feb 24, 2011, at 3:31 AM, Frank wrote:
>
> > How would I do this? [return the hull of a settlement built from an
> > NEO on site]
> > Lightweight, self deploying molds with attached ion propulsion and/or
> > solar-sails with "Roller-Reefing" attitude
>
> Do the calculation as to the mass of the solar sail needed for this.
>
The mass depends also on what you want to do with the solar sail.
If you need a really large one - or a smaller one, which is rather used for
energy production (to power the SEP-thrusters) and attitude control.

In this case the sail foils are solar cell foils thought to produce a
lot of electric energy to power
thrusters and the spacecraft operation.

Eric Drexlers idea of space fabricated and lighter solar sails might be
viable for a solar sail,
which is used for propulsion only. But it does not provide ample energy
for a power sucking
mission. A spacecraft which uses "Roller Reefing" with solar cells, is a
mobile solar power station,
able to provide more power as the ISS does now.

The sail foils used for the SSPS-spacecraft would just feature a mass of
32 kilograms.
Not so much, to give up the advantage of better production capacity on
Earth to save
a part of this 32 kg.

The solar foil material would be solar cell foil.
It is tested on The *Materials International Space Station
Experiment* ( **MISSE**). Figure 100 m2 per kilogram, 16,800
Watts/kg.

This foils for power production and attitude control would be available
in 1.5 micron CORIN polyimide thin film a-Si:H solar panels, 168 Watts/m2,
which would weigh about 32 kilograms for 3,120
square meters for a Ariane V-launcher-version of the SSPS-design and
produce
in this version 524 kWp DC electricity.
see also
http://nextbigfuture.com/2009/02/welsome-space-consortium-solar-space.html

Best wishes.

Frank