Kalpana One design (was Rotating space colonies)

--- In spacesettlers@yahoogroups.com, Joe Strout wrote:
>
> On 9/30/10 2:58 PM, brooksn wrote:
>
> > If we capture asteroids then the constant distance is still there.
>
> True. But that requires a whole lot of energy. Even if the asteroid mass is negligible, you have the delta-V of getting to the asteroid and then getting back to Earth orbit, which must be provided entirely by the rocket equation. And of course we wouldn't want a zero-mass asteroid; but the more mass it has, the more energy (and >reaction mass) it will take to change its orbit.

But we aren't taking large asteroids from the asteroid belt, we are taking 5 to 10 meter asteroids that are passing by Earth, in fact they pass within the moon's orbit all the time. The amount of fuel needed to divert that small an asteroid just enough to enter the upper atmosphere for aerobraking, strap on a heat shield and you preserve more of the asteroid, is not very costly energetically. And then adjust the new elliptical orbit until you meet up with the ISS.

> Getting stuff to/from the Moon requires delta-V too, but you have
> options other than rockets to do it. In particular, for the large
> amount of mass you would be shipping FROM the Moon, you could use a Mass
> driver, which requires no reaction mass and doesn't rely on the rocket
> equation.

My understanding is that mass drivers require very large amounts of energy and infrastructure, which might reduce delta-V energy costs, but would likely explode the actual monetary budget.

> > Traveling on the moon from impact site to impact site and then launching
> > what you find from the lunar gravity seems more costly then finding an
> > NEA and capturing it.
>
> I don't see how. Again, you can move around on the lunar surface just
> by turning wheels. To change orbits in space requires rockets. We
> don't move things around on Earth using rockets, because they're
> horrendously expensive (no matter how you measure it) compared to simply
> pushing against the ground (or something bolted to the ground, such as
> tracks).

You have to travel to the location, mine it, then strap it to a rocket (or expensive mass driver) and then launch it. An asteroid can weight 100's of tons and can be captured easily by adjusting an already Earth crossing orbit. I doubt 100's of tons can be sent up from the moon for the same cost.

> > Though more available many volatiles are still
> > missing and only in concentrated form at the poles.
>
> True enough. But the majority of the mass you need to build a colony is
> radiation shielding. Any old regolith or slag will work for that. As
> Mike says, we'll probably end up using both, as well as materials
> launched from Earth. But I will bet that the vast majority of the
> material ending up in the first colonies will be lunar in origin.
>
> Best,
> - Joe

But the purpose of your base was to launch material into orbit, you need fuel for that and volatiles in particular. Regolith or asteroid scrap, radiation shielding will be the easy part. What should be the number one concern is cost, energetically and monetarily and I don't see how a new lunar base beats an ISS small NEA capture.

Brooks