Using Concrete to build space ships...

>> Part of my proposal was using a solar sail carrier craft to
>transport
>> smaller prospectors and their payload.
>> The prospectors would fly but mainly between carrier and asteroid.
>
>Where will the solar sails come from? How many would you need?

I would use three, as Columbus did when discovering America.

Each of them carrying a fleet of smaller crafts stacked in its center
magazine docking station.

>
>> So for the building phase transportation would be cheap.
>
>It will be cheap if you somehow manage to get untold thousands of
>these 1 km in diameter solar sails into oribt, and then to the
>asteroid. Who's going to pay to get them into orbit?

Those 3 one km diameter solar sail carriers would probably have a lot
less of mass than your small crew carrying space transporter.
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?

The solar sails would need only little fuel.

Has the small manned transporter radiation shielding?
How is this accomplished? Which mass will this craft have?

>
>> As the building material transportation would be cheap we could
>build
>> the cycler on the earth-sun libration region were the sun and earth
>> gravitation outweighs each other.
>
>I think you still need to demonstrate that building material
>transportation will be cheap rather than just asserting it will be
>so.

Wouldnt you say, that a space craft which can have a constant thrust
of 7 Newton all the time if needed without using fuel at all could
move cheap?

>
>Also, I'm unclear as to the advantage of hauling all of this
>material back to L1. Why do so?
Libration points are thought to be less demanding for station holding
although the L1 libration point is thought to be more unstable than
others.
The reason I proposed it was the slingshot effect you rebuffed.

>

>How much energy is required to
>>maintain position at L1?
It would be less than in an orbit I think.
Solar sails can hold position in space, at least in the inner planets
area. There is no need to determine energy requirements since they
are able to hold position using free energy through photonic pressure.

>
>> So we have gravity assisted slingshot propulsion for free
>acceleration
>> of the cycler available which could be additional supported through
>> the cyclers thrusters. Just doing the first push and the craft will
>> start accelerating.
>
>Accelerating is fine, but you need both directional control and
>control over the magnitude of acceleration. There is a limit to how
>much momentum exchange one can realize from a slingshot.

When you have a standstill you can point the craft in any direction
you like just use the thrusters as long as needed to get it going.
Could you do that with a fast moving mountain of asteroid?
With that kind of inertia?

Probably it will be hard to change direction at all with such a huge
mass.

>
>I haven't seen any calculations that claim that you're going to get
>over 4 km/sec boost in velocity. Can you provide some info on this?

I didnt do that calculations. Could you prove that it is not
possible? Than go ahead.

>
>> The standstill which you see as a disadvantage has the advantage
>> that you need a lot less energy to point to the exact orbit youll
>> like as you would need to change the inertia of a fast moving
>> asteroid already influenced through earth gravitation when we
>> would get to it.
>
>Can you reword this because I'm not sure of what exactly you're
>trying to say.

I tried that above.

>
>Your 200,000 tonne cycler will have to increase it's velocity by
>4.3km/sec to get to a Mars orbit.
>
>KE = 0.5 mv^2 ------> 0.5 * (200,000,000 kg)(4,300 m/s)^2 = 1.85 *
>10^15 Joules
>
>Now let's find an asteroid of 4,000,000 tonnes mass. TWENTY TIMES
>HEAVIER. It is moving at a velocity of 4 km/sec in a nearby orbit.
>It will need a delta-v of 0.3 km/sec in order to get into the cycler
>orbit.
>
>KE = 0.5 (4,000,000,000 kg)(300 m/s)^2 = 4.5 * 10^14 J.
>
>You'll need TEN TIMES more energy to get your cycler into the proper
>orbit than it would take to get a asteroid that is TWENTY TIMES more
>massive into the same orbit.

You did not account for the energy won through the gravitational
slingshot on the cyclers side.
You also just seem to state that no change of direction of your
asteroid is needed. I doubt that. Just adding delta-v wont do the
trick.

>All of that EXCESS mass can serve as reaction mass in a mass driver
>in order to change the orbit. Or if it is ice, then that can be
>burned as rocket fuel. We don't need to send up fuel from Earth to
>bring the vessel (or asteroid) into a cycler orbit. The asteroid
>provides the fuel. It's free.

I am with you on this but am a bit uncomfortable with throwing rocks
out for propulsion. But using water for steam propulsion or making
fuel off it would be fine for me.

Frank