What Size will the Swarm of Robotic Spacecrafts be?

Length l of the robotic swarm (before inverted aerobraking) is:

All values are counted into the direction of the robotic swarm, i.e. all are positive (with the possible, but not very useful exception of initial velocity).

To compute l, take the point of view of the robotic swarm, i.e. subtract the speed of the robotic swarm from all given velocities. The speed of the robotic swarm is therefore zero in our new coordinate system. The space ship has an initial velocity of the speed of the kinetic fuel (in earth based coordinates) coming towards the swarm, minus any forward velocity the space craft got from going to orbital height. The space craft is then decelerated (a becomes negative) to its final velocity. During this time, the space ship travels a distance of l in relation to the swarm. Hence l is the necessary length of the swarm.



Remember that a final velocity of more than 80% the speed of the kinetic fuel becomes more and more inefficient (see ImpulseTransfer).


Estimating the necessary number of robots in the swarm is more difficult, because it depends on how long before impact on the aerobrake kinetic fuel can be put in space, and at what speed (speed in relation to the swarm). Which in turn depends on the capabilities of the aerobrake and its needs to create and maintain the plasma shield and the strength of the plasma shield.

How to turn kinetic propellant into gas / plasma before impact? Project Orion told me not to worry too much about creation of the protective plasma layer. So wether to use pulsed or continuous impact is not as important as I feared. But it also confirmed my opinion that a pusher plate / heat shield can not withstand impacts of solid particles (see cite of shrapnels from duds).

So far I have basically two ideas I consider to be realistic:

  1. Go for extremely small pellets of solid propellant, something like snow flakes. Such snow flake should be able to survive in space for several seconds, minutes or even longer. Building a relatively small number of robotic vaccum snow cannons should be possible. But how coherent could one make the stream of snow flakes? How fast will those snow flakes drift apart while flying towards the space ship? And how thick a plasma shield do you need to reliably vaporize a 12 km/s snow flake? (Which - as I was told - would kill me instantly if it would impact on me. Certainly without wearing a bullet proof west, maybe even with wearing one.)
  2. Use a lot of small and cheap robotic space ships, each of which blows a small cloud of gas onto the space ship as it passes by (click here for a simple animation of that). This would surely work and is therefore currently my favorite idea.

(Still a lot of work to do here ...)