A laboratory facility under development by the European Space Agency (ESA) for use in conjunction with the NASA SPACE SHUTTLE in the 1980s. It consists of two basic elements: a pressurized manned laboratory (in which up to four scientists can work in a "shirt-sleeves" environment), and an external unpressurized platform or pallet which carries instruments that require direct exposure to space. Other possible configurations include a full-sized pressurized laboratory and a full-sized pallet operated from within the Shuttle orbiter's crew compartment.
In a typical mission, Spacelab will be carried into orbit in the Shuttle cargo bay, the cargo-bay hatches will be opened to expose it to space (the laboratory remains attached to the Shuttle) for the duration of the working period (one to four weeks) and, finally, the hatches will be closed for re-entry and landing. Spacelab will thus be a re-usable facility which can be modified and equipped specially for each mission. It will therefore be cheaper and more effective than SKYLAB.
