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Wanted, orbit calculations for a permanent Earth-Mars interplanetary shuttle.

Launcher poly Australia
Status Vaulted: Jan 26, 2015 04:30


the Earth Mars interplanetary orbits spaceships interplanetary shuttles


The concept to be investigated is of a shuttle station spacecraft with an elliptical orbit which would travel unpowered between the orbits of Earth and of Mars, always reaching Mars at the time when Mars was at the closest position in its normal orbit. For this to occur, the shuttle's orbital period would have to be exactly the same as that of Mars (about 2 Earth years). A calculation is wanted for such an orbit, perhaps with the ellipse extending beyond the Mars orbit, so the coincidence of positions would occur on only one leg of the orbit. The inner part of the ellipse would graze Earth's orbit on the other side of the Sun, but not necessarily coincide with Earth. While fuel would be needed each trip to move passengers and consumables onto and off the shuttle, fuel to position living and control structures would be needed only once. (ZBL#107).

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The Mars Free Ferry (MFF) (this is an interim posting to the Vault)

The basis of the Mars Free Ferry is an essentially unpowered space object moving continuously between the orbits of Earth and Mars. This might well be an elliptical Hohmann Transfer Orbit. Say you're an interplanetary trader, you have a container of widgets which you need delivering to Mars. You hire a space taxi to get the container up to Earth orbit (actually likely to involve several stages), and have the taxi match the orbit of the closest (in delta-V) of the 12 Mars Free Ferries, say the December one. Once there, you wire the container onto one of the shackle points of the MFF, and go home. Later, on Mars, your agent takes their space taxi up to the approaching MFF, unhooks and stows the container, and descends to the Mars Customs base. The MFF continues on its way. The MFFs are permanently in a space environment, and can resemble maybe a wired-together junkyard. In the yard there may, or may not, be one or more living modules, which will need supply with life-support stuff like oxygen and food, and have working equipment such as toilets and kitchens. Maybe the whole mess is spinning to provide artificial gravity. Maybe a radiation refuge. Obviously the MFF does not use any energy to continue in its elliptical orbit. If it has living modules, these will need life-support consumables, but not life-support equipment - that is already there. Essentially, the only delta-V you need for Earth-to-Mars or back is for the cargo or people at the transfer ends. All the spaceship mass etc travels for free. That said, the MFF will have minor costs for communications, maintenance, and possibly minor course correction for second-order perturbations to its orbit (maybe an external, slot-in minimum-thrust module), but these will be only minor. It appears that the delta-V needed to take advantage of an orbit which comes physically close to Mars may be excessive compared to the delta-V needed to coast along almost in Mars orbit to meet a Mars-orbital or Lagrange Point space-station. Maybe the space taxis might be unmanned for freight transfer. Brian Dodson's detailed analysis is attached.

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