Shuttle extravehicular activity (EVA). Astronaut Gregory Harbaugh (nearest camera) carrying astronaut Mario Runco during an EVA mobility test during Shuttle Mission STS-54. Harbaugh is carrying Runco along Endeavour's cargo bay in order to simulate carrying a large load. This is part of an on-going programme to evaluate EVA mobility and the ability of astronauts to work in a weightless environment. These tests will be of special use during construction and maintenance of a future space station. The experience will also be of use in designing future space suits. Mission STS-54 flew on 13-19 January 1993.