Using Concrete to build space ships...

>
>> Those 3 one km diameter solar sail carriers would probably have a
>> lot less of mass than your small crew carrying space transporter.
>
>So what? The ship is quick to get to destination, can be reused
>multiple times, is versatile so that other missions are possible.
>The amortization of the ship is plausable.
>
>> Who is going to pay to get that into orbit and the fuel it will
>> need to reach an asteroid probably out of earths magnetic shields?
>
>I'm not claiming that they'll be free. You're the one making that
>claim.
>
>> The solar sails would need only little fuel.
>
>OK. From a previous post, we know that we can get 1 Newton of thrust
>from 212,750 m^2 of solar sail operating at optimum condition.
>
>You're proposing 3 1-km diameter solar sails. Each such sail would
>have 785,000 m^2 of sail. This would equal 3.7 Newtons of thrust.
>
>Let's say that the asteroids to be mined are somewhere between Mars
>and Earth. Their distance will vary between 250,000 km and
>78,000,000 km as they progress through their orbits. Let's say that
>we work with an average distance of 40,000,000 km for the cargo to
>travel.
>
>Recall that:
>Force = mass*acceleration
>Distance = 0.5acceleration*time^2
>
>Each solar sail puts out 3.7 Newtons. You have 3 sails.
>You need 200,000,000 kg of material.

I have 3 sails which carry say 12 prospector crafts each to the
asteroid. So we had 36 prospectors now.

Each of this prospectors would be able to get off 1 ton material with
each fare.

Since we are already at the asteroid there is no need for the sails to
transport the regolith/ asteroid materials, only if we would need
materials from other asteroids (water for instance) we had to use the
sails for that.

If the cycler would be done in space but near the asteroid, the
prospectors would carry their loads just off the asteroids to the
construction site.

So the 36 prospectors would do their work now. They dont need the
carrier sails for that. The carrier sails would be free, to go back to
earth, taking on new prospectors, molds or gear.

Frank