Three 8″x10″ photographs of the Manned Maneuvering Unit (MMU) developed by Martin Marietta (now Lockheed Martin). Photograph of the most popular image from the space shuttle era, taken during STS-41B in April 8, 1984, showing Capt. Bruce McCandless as the first human to fly untethered in space, using the Manned Maneuvering Unit (MMU).