Abstract: A centrifugal propellant depot positioned in outer space for storing and transferring cryogenic liquid propellants to and from transfer space vehicles which are adapted to transport cryogenic liquid propellants to the depot to receive the liquid propellants stored in the depot. The depot includes a plurality of contra-rotatable torus-shaped hollow storage tanks adapted to receive cryogenic liquid oxygen and hydrogen propellants that are carried in gas/liquid phase separation by rotational gravity. Transport rail members transversely bridge the storage tanks. A central docking hub is coupled to the transport rail members and disposed centrally of the rotating storage tanks. The docking hub may receive a transfer space vehicle on either of two opposing sides of the hub for transfer, via a transfer vehicle coupled to the rail members, outwardly to the storage tanks.

Abstract: A method of navigating an airborne vehicle using observation of linear features such as roads, railroads, rivers or the like. Maps of linear features in several discrete areas along an intended flight path are prepared and entered into an on-board computer memory. The vehicle typically uses an inertial navigation system during flight from the origin to the first mapped area. Imaging sensors and on-board processing detect linear features as the vehicle approaches or passes over them. The sensed feature pattern network is compared to the reference mapped feature network to update the inertial navigation system to generate guidance commands. Frequent updates at other mapped areas keep the vehicle on course. This system is also capable of navigation updates from single linear features when the flight path is fairly well known, and of tracking a linear feature for terminal guidance. In these cases, only a small number of feature parameters need to be stored, rather than an area map.