Interplanetary transfer method

Abstract

A method for increasing the payload that can be delivered by a given launch vehicle to a selected target in an interplanetary space mission, without increasing the transfer time to reach the target. In accordance with the disclosed method, a conventional multi-stage launch vehicle is used to accelerate a payload spacecraft to near earth's escape velocity. Then the spacecraft is separated from the upper stage of the launch vehicle and is further accelerated by applying a velocity impulse with an onboard propulsion system into a transfer trajectory that takes the spacecraft to the target planet. Because the upper stage of the launch vehicle is not accelerated into the same transfer trajectory, a larger payload mass can be delivered to the target planet without increasing the transfer time. Alternatively, the transfer time can be reduced without decreasing the payload mass or changing the launch vehicle configuration. In another disclosed embodiment of the method, multiple spacecraft are launched by the same launch vehicle, placed in separate trajectories to one or more destinations, and then separately placed in different final trajectories, such as different orbits around the target planet. In yet another disclosed embodiment of the method, an additional velocity impulse is provided by onboard propulsion as the spacecraft nears an intermediate target planet, to reduce transfer time in a mission that includes a powered planetary swing-by.