Jumping the Gun.

--- In spacesettlers@yahoogroups.com, "Karell Ste-Marie"
wrote:
> Ok, so essentially the asteroid acts as the wall that prevents the
> driver itself to going in the opposite direction while the pebble
stays
> exactly in place (in greatly exagerated terms).
>
> Ok, I understand - however why does this cause the asteroid to
loose
> mass? Recoil?

Try this experiment. Go to an ice-rink, put on a pair of skates, go
onto the surface of the ice. Do not brace yourself in any fashion
and take an object into your hands and throw it. You'll notice that
the object moves away from you and you also slide back a little.

The reason you did this on an ice surface is because we've tried to
remove as much friction from the experiment as possible. In space,
you won't have this friction to deal with. The distance you slid
backwards was determined by the mass of the object you threw and the
velocity you imparted. This translated into your body, which had a
much higher mass, so the velocity was reduced and you slid backwards
at a slower rate than the object you threw away from you.

On an asteroid, let's say of millions of tons, each pebble would
weigh 100g to 1 kg. The velocity of launch might be on the order of
2 - 10 km/sec. When this is translated back into the more massive
asteroid, the velocity change will be slight, but because there is
no resistance against motion, the velocity will be real, measurable,
and constant. Over time, as pebbles are launched every second, the
velocity grows.

As you mine these pebbles from the asteroid and launch them into
space, the asteroid loses mass because it is where all of these
pebbles are coming from.

TangoMan