On February 7, 1984, during the STS-41-B (the tenth NASA Space Shuttle mission and the fourth flight of the Space Shuttle Challenger), NASA astronaut Bruce McCandless II (b. 1937) made the first ever untethered free flight using the Manned Maneuvering UnitNotes 1. With a distance of 98 meters (320 feet) from the space shuttle, he also broke the spacewalking record.
McCandless became the first astronaut to maneuver about in space untethered, during this first “field” tryout of a nitrogen-propelled, hand-controlled backpack device called the Manned Maneuvering Unit (MMU).
Not long afterward, NASA discontinued such actions and decided to perform only tethered spacewalks for safety reasons. In 1994, NASA unveiled a new backpack called Simplified Aid for EVA Rescue, or Safer, and tested it with an untethered spacewalk, the fourth, and thus far last untethered extra-vehicular activity it has performed. Every astronaut at the International Space Station wears Safer, which is smaller and lighter than the manned maneuvering units, for use during an emergency.
In an interview, McCandless II has said that: “Flying out to a distance of 100 meters from the Shuttle was indeed fascinating and yielded a spectacular viewpoint. Alas, I had intended to yaw around 180 degrees, to face away from the Shuttle, to contemplate the beauty and emptiness of a space devoid of apparent man-made objects, but there was so much conversation over the three radio channels (Mission Control, the Commander, and Bob Stewart) that I forgot to do so. Unexpectedly, I got very cold while maneuvering at a distance from the Shuttle. On considering the problem it became apparent that the life support system was designed to maintain the comfort of a person working at a moderate level of physical exertion – and I was using only my fingertips on the controllers. Briefly shutting off the heat rejection subsystem (sublimator) solved that problem. Post-flight, the Flight Surgeon from Mission Control noted that my heart rate (as displayed on telemetry) was normal and constant throughout the EVA, confirming my feelings of being relaxed and in-control at all times.”
Breaking the spacewalking record – NASA film JSC-849
Narrated by the Commander and crew, this program contains footage selected by the astronauts, as well as their comments on the mission. Footage includes launch, onboard crew activities, and landing.
1st flight of the Manned Maneuvering Unit (MMU); Astronaut Bruce McCandless, the first human Earth-orbiting satellite, ventured out 320 feet (98 m) from the orbiter.
Commander: Vance D. Brand
Pilot: Robert L. Gibson
Mission Specialists: Bruce McCandless, II, Robert L. Stewart, Ronald E. McNair
Dates: February 3-11, 1984
Vehicle: Challenger OV-099
Payloads: PALAPA B-2/PAM-D, WESTAR-VI/PAM-D, IRT, MLR, ACES, IEF, RME, SPAS-01A, SSIP (one experiment), GAS (five experiments), and Cinema 360 camera
EVA: (MMU) tested Manned Maneuvering Unit
Landing site: Runway 15 at Kennedy Space Center, FL
- The Manned Maneuvering Unit (MMU) is an astronaut propulsion unit that was used by NASA on three Space Shuttle missions in 1984. The MMU allowed the astronauts to perform untethered EVA spacewalks at a distance from the shuttle. The MMU was used in practice to retrieve a pair of faulty communications satellites, Westar VI and Palapa B2. Following the third mission the unit was retired from use. A smaller successor, the Simplified Aid For EVA Rescue (SAFER), was first flown in 1994, and is intended for emergency use only.