guest blogger john hare
With the information from Bob Steinke, I was able to prove to myself that the retro station concept wouldn’t work for Mars return even with two Lunar passes and one Earth pass. It may still be of interest to some NEO return missions that are really tight on the mass budget.
The lines in black represent the flight path of the attempt to save the concept with a double Lunar flyby using the Earth to focus the second pass. The red represents what is possible with a minor retro burn at perigee. A 400 m/s burn can capture a Mars return vehicle to a highly eccentric orbit. The burn to capture is not shown in the same capture plane to leave room in the cartoon, not because it is in the correct orientation.
The question is, can a 400m/s capability be given to the craft without excessive mass ratio penalty for the there and back?Â The required propellant will mass a substantial fraction of a heatshield that would return the craft to the Earth’s surface. It will also have to be accelerated from Mars or other point of interest at the cost of more propellant. Since some or all of that propellant probably comes from Earth, the initial mass requirements get quite interesting.
My next thought is a very small refueling tanker or tug Â in Earth orbit that accelerates toÂ dock with the return vehicle in time to make a capture burn intoÂ HEEO. That will take a 4,000 m/s tanker/tug Â burn,Â rendezvous, and 400 m/s braking burn in roughly 45 minutes. That would require aÂ Â rendezvous and docking time so far unheard of in real space operations.