big moving job

Ed Minchau wrote:

> At least now we know the maximum likely energy requirement for such a
> job. Suppose we are talking about a stony asteroid (density ~
> 5000kg.m^-3) with a roughly spherical shape 100m in diameter, sharing
> the same orbit with Ceres; about 2.6e9kg, so this gives about 1PJ for
> a delta vee of 1km/s, less than one billionth the energy required to
> move Ceres; this makes a mirror only a few tens of kilometers across.

Yes, a few million tonnes should keep you busy for a while.

Ok, lets make this a bit more exact.

Let's assume you use rocketry techniques (and/or massdriver).

The actual energy required depends on the amount of mass
in the exhaust and its speed.

Ok. Next step:

dV = Ve ln (Mi/Mf)

where dV = delta V
Ve = velocity of exhaust
Mi = Initial mass
Mf = final mass
The energy required is 1/2 * (Mi-Mf) Ve ^ 2

Note that delta V doesn't necessarily correspond to
the actual change in velocity (because of gravity),
its only a theoretical freespace acceleration
number.

These equations should work for rocketry or mass
drivers.