LRV was an open rover for a crew of two, and a range of during one lunar day. One NASA study resulted in the Mobile Lunar Laboratory concept, a crewed pressurized rover for a crew of two, with a range of . The Soviet Union developed different rover concepts in the Lunokhod series and the L5 for possible use on future crewed missions to the Moon or Mars. These rover designs were all pressurized for longer sorties. If multiple bases were established on the lunar surface, they could be linked together by permanent railway systems. Both conventional and magnetic levitation (Maglev) systems have been proposed for the transport lines. Mag-Lev systems are particularly attractive as there is no atmosphere on the surface to slow down the train, so the vehicles could achieve velocities comparable to - or even higher than - aircraft on Earth. In essence any maglev on the moon would behave similar to a vactrain without the need to provide an artificial vacuum. One significant difference with lunar trains is that the cars would need to be individually sealed and possess their own life support systems. For difficult areas, a flying vehicle may be more suitable. Bell Aerosystems proposed their design for the Lunar Flying Vehicle as part of a study for NASA, while Bell proposed the Manned Flying System, a similar concept. Surface to space Launch technology Experience so far indicates that launching human beings into space is much more expensive than launching cargo. One way to get materials and products from the Moon to an interplanetary way station might be with a mass driver, a magnetically accelerated projectile launcher. Cargo would be picked up from orbit or an Earth-Moon Lagrangian point by a shuttle craft using ion propulsion, solar sails or other means and delivered to Earth orbit or other destinations such as near-Earth asteroids, Mars or other planets, perhaps using the Interplanetary Transport Network. A lunar space elevator could transport people, raw materials and products to and from an orbital station at Lagrangian points or . Chemical rockets would take a payload from Earth to the L1 lunar Lagrange location. From there a tether would slowly lower the payload to a soft landing on the lunar surface. Other possibilities include a momentum exchange tether system. Launch costs Estimates of the cost per unit mass of launching cargo or people from the Moon vary and the