Thermal and environmental control of spacecraft and astronauts during extravehicular activity requires the transfer of heat between various thermal sources and sinks. Solid/vapor heat pump technology utilizing a condensing/evaporating refrigerant holds considerable promise for space applications due to the variable temperature and variable load capabilities of these devices. In addition, solid/vapor adsorption systems involve no moving parts, may utilize non-toxic and non-flammable solid adsorbents and refrigerants, and are lightweight. This paper describes the fundamental operating characteristics of solid/vapor adsorption technology. The effects of (1) the choice of the specific refrigerant/adsorbent pair, (2) the thermal sink and source temperatures, and (3) the heat transfer characteristics of the adsorption beds on the performance of the system are described.