Power with a push

A couple of posts ago we noted that we'd probably need something on the order of 1 Terawatt of power to accelerate the ship. If we get beam this power from the solar system, e.g., using masers or lasers we'll get a bit of momentum with it as well. If we just absorb the power then the force on the ship is

    F = P/c

where P is the power of the beam and c is the speed of light. For 1 Terawatt we get

    F = 1012 / 3x108 Newtons = 3000 Newtons

This about 1% of the total force needed to accelerate our vessel. So if we just ramp up the power a bit we can push our ship this way. We get an extra factor of two if we reflect the incoming beam rather than absorbing it.

However while this works nicely accelerating our ship, without a comparable beam at our destination it won't work to slow down. So for an established interstellar pathway this might be something to consider, but it's not going to do the trick for exploration. We can use the beam to speed up, but we'll need something else to slow down.

One approach here is to have sent a dummy mirror out in front of our vessel simply to reflect the beam back. The dummy mirror needs a mass comparable to the vessel and thus doubles all of the energy requirements, but we might be able to use it as a probe to explore a further star system since it will end up travelling at a good fraction of c.