Low energy trajectories

Cargo could be inserted into low-energy trajectories. These trajectories will take longer then current Hohmann transfer orbits, but will save propellant and thus allow more payload. Low cost of transport will be vital in setting up a colony and in resupplying a semi-autonomous colony. It also allows for some items to be tradable without a tremendous transportation cost.

Methods

• Bi-elliptic transfers
• The Interplanetary Transport Network
• Using ion thrusters/solar sails/plasma sails

Disadvantages

• Such trajectories will take much longer then Hohmann transfers
• Low energy transfer orbits can only launch when Mars and Earth are in the correct orbital positions. Where as high energy trajectories can launch in larger time windows.
• This means cargo will be exposed to the harsh conditions of space for a longer period of time. New and ingenious methods will be needed to solve this for radiation or time sensitive cargo.