From Scott Lowther's USSP01 description of this wonderfully simple craft;

USSP-01-01: Two Man Space Taxi

Many early manned planetary mission studies involved the use of flotillas of spacecraft, sometimes flying relatively closely, sometimes spaced out by days or weeks. Since many of these manned spacecraft were nuclear powered, the ships couldn’t easily get too close to each other. For spacecraft like the atom bomb-powered Orion vehicles, fine maneuvering would be a virtual impossibility. Thus ships could rendezvous, but actually docking them might well be impossible.

The Astronautics division of General Dynamics designed a solution in the form of “Space Taxis.” At least two versions were put forward, a one-man and a two-man design. These were simple pressurized cylinders with hemispherical endcaps equipped with hatches, docking features, life support systems and a propulsion system. Details on the two designs are lean in the available literature, but it is clear that the taxis were extremely simple and lightweight. They were designed only to provide ship-to-ship transport over a short distance and for very limited durations. They were not required to provide re-entry protection, radiation shielding or even toilet facilities.