Ferry to the moon

Solar-electric propulsion for a fleet of lunar ferry vehicles may allow the creation of a permanent lunar base not long after the turn of the century with greater cost effectiveness than a fleet of chemically powered spacecraft. After delivery by the Space Shuttle to a 300-km earth orbit, the lunar ferry envisioned would travel in spiral trajectory to the moon under the power of 300-kW solar arrays and ten 30-kW Xe-ion engines; each of the solar arrays would be 12 x 61 m long. Each trip between the earth parking orbit and the moon would take about 1 year, so that a fleet of four ferries operating simultaneously could deliver 20 metric tons to a lunar base every 100 days.