Part of the expense associated with deep-space mission derives from the inefficiency of chemical propulsion, the large amounts of fuel and propellant required to achieve mission-necessary delta-V, and the need to carry all consumables from the start of the mission.

We propose a new space transportation paradigm, which relies on the buildup of certain space “infrastructure”, to minimize per-mission cost. Making a comparison to 19th century travel across North America, this is similar to replacement of Conestoga wagons with the Trans-Continental Railroad.

The infrastructure we propose is a set of man-made space stations of man-modified natural celestial bodies (e.g., small asteroids), maneuvered into a set of useful orbits, and equipped with electromagnetic launchers (railguns) as well as human habitats, depot facilities, power systems and orbital maneuvering systems (e.g., electromagnetic thrusters). On each space station or asteroid, the railgun allows small mission vehicles (spacecraft) to achieve large delta-V’s in short time without consuming onboard propellant. The orbital maneuvering system (e.g., nuclear or solar-powered system of electromagnetic thrusters) allows the space station or asteroid to compensate for the delta-V’s so imparted, and adjust its orbit to achieve desirable parameters.

An object in an elliptical solar orbit tangent to Earth orbit at perihelion, but with semi-major axis ~ 1.66 a.u., has a natural orbital period of roughly 25.6 months - the interval between Mars mission opportunities from Earth. If the semi-major axis of the orbit can be rotated appropriately about the Sun every orbit, through the use of electromagnetic propulsion an gravitational assists from the Moon and Mars, etc., good rendezvous opportunities will be provided every orbit.

The railgun, combined with gravitational assists from Mars and aerobraking, and perhaps some residual delta-V provided by traditional means, offers an efficient and economic rendezvous technique for spacecraft departing the space station or asteroid for Mars.