DRS. Werner Von Braun and Ernst Stuhlinger have advocated a rather interesting concept for travel to Mars. The trip would involve transport in three separate vehicles. The first, a conventional liquid or solid fueled 3-stage vehicle, escapes from the Earth's atmosphere and terminates at an orbiting space station 1000 miles from the Earth's surface. The second vehicle, the space cruiser, leaves the satellite orbit and enters an orbit 600 miles above Mars. The third vehicle, the landing vehicle, would be detached from the space cruiser, reduce its orbiting speed by rocket power and enter a downward trajectory thru the Martian atmosphere.To return, the landing vehicle would leave from Mars to the orbiting cruiser, the crew transfer to it, and begin the return flight to the Earth's satellite. Return to the Earth is made in the crew-cargo portion of the third stage rocket that made the trip from Earth to its satellite.The space cruiser would of necessity be assembled at the orbiting space station and due to the large investment in fuel for the commuter rockets to transport the component parts for both the space station and the cruiser, lightweight construction is an absolute necessity. Because the largest part of the weight of the space cruiser will be taken up by fuel, the investigation of a suitable propulsion system is imperative.