L1 to Mars: A Combined Robotic/Piloted Mars Mission

Mission scenarios for piloted Mars mission have traditionally consisted of a landing on Mars followed by a long stay time before the Earth–Mars planetary alignment would allow a minimum energy return. The long mission times increase both cost and risk, which need to reach levels below current projections before any such missions will be practical. An option that may eventually prove advantageous would be to orbit the spacecraft at the sun–Mars Lagrange point. Such a mission appears possible using bimodal nuclear thermal electric propulsion (BNTEP). The use of BNTEP can decrease round-trip mission times to Mars to one year, significantly reducing not only the cost, but also the risks from cosmic rays, solar flares, weightlessness, and isolation. Orbiting the spacecraft near the Lagrange equilibrium point , using high-performance electric propulsion systems driven by nuclear power, reduces the propellant mass (cost) required and the risk by shortening the mission time. Because is an unstable equilibrium point, little propellant is required to leave after parking at . Stationing the spacecraft also allows for the use of electric propulsion to enter and leave the equilibrium point. Leaving from using electric propulsion will also significantly shorten the transit time back to Earth, primarily because spiraling out from low Mars orbit will not be necessary. For BNTEP mission scenarios to become a reality, high-performance electric propulsion needs to be developed and high-performance bimodal nuclear thermal reactors need to be designed and tested.