Bruce McCandless II (June 8, 1937 – December 21, 2017), American naval officer and aviator, electrical engineer and NASA astronaut, passed away this week at the age of 80.
During the first of his two Space Shuttle missions, McCandless made the first ever untethered free flight using the Manned Maneuvering Unit in 1984 and starred in one of the most memorable images of our time.
Career
At age 28, McCandless was one of the youngest astronauts selected by NASA in April 1966.
McCandless was a CAPCOM (Capsule Communicator) on Apollo 11 during the first lunar EVA before joining the astronaut support crew for the Apollo 14 mission, on which he doubled as a CAPCOM. (A CAPCON is the person who communicates directly with the crew of a manned space flight). He was backup pilot for the first crewed Skylab mission.
He flew as a mission specialist on two space shuttle missions. On STS-41-B in 1984, he performed the famous spacewalk and on STS-31 in 1990, he helped deploy the Hubble Space Telescope.
He was responsible for crew inputs to the development of hardware and procedures for the Inertial Upper Stage (IUS), Hubble Space Telescope, the Solar Maximum Repair Mission, and the International Space Station program.
Previously, as an officer at the Navy, McCandless flew fighter planes including the T-33B Shooting Star, T-38A Talon, F-4B Phantom II, F-6A Skyray, F-11 Tiger, F-9 Cougar, T-1 Seastar, and T-34B Mentor, and the Bell 47G helicopter.
The MMU
The Manned Maneuvering Unit (MMU) was an astronaut propulsion unit (not a backpack) which was used to perform untethered EVA (Extravehicular activity) around the space shuttle. The MMU was first tested in mission STS-41-B. It was used in two subsequent STS missions to retrieve three faulty communications satellites.
The MMU used 24 nozzle thrusters and nitrogen gas to maneuver the unit and the astronaut in space. Two aluminium tanks with Kevlar wrappings contained 5.9 kilograms of nitrogen each, enough propellant for up to six-hours of EVA. With a full propellant load, its mass was 148 kilograms.
The MMU was operated using fingertips to manipulate hand controllers at the ends of the MMU's two arms. Once maneuvered to a final position, an automatic attitude-hold function could be engaged, which freed both hands for work.
The MMU was retired from use after its third STS mission. It was judged too risky for further use and many activities planned for the MMU could be done effectively with the highly maneuverable shuttle and its robotic arms or with traditional tethered EVAs. For the International Space Station, NASA developed different tethered spacewalk approaches.
MMU Development
McCandless was instrumental in the design of the MMU and its earlier versions.
Even though various variations of the MMU were developed by NASA in the early years, most program managers thought it was too risky. Their worry — oft repeated in the shuttle’s early planning phase — was that a pressure-suited astronaut in the vacuum of space was “one system away from certain death.”
There was no clear scenario where an MMU based EVA would be absolutely required in a space mission. A scenario surfaced in 1982, when NASA made the decision to have astronauts capture the failed Solar Max satellite and repair it in the shuttle’s cargo bay. The MMU found itself a mission.
The idea of an astronaut floating in space without a tether scared the bejeesus of everyone. McCandless and Stewart strongly argued against using a tethered MMU — it could easily get tangled or wrapped around the external parts of the shuttle or around an astronaut. Besides, the MMU was intended to crawl at a few inches per second and the spacewalk would not extend too far from the shuttle. All systems on the MMU were redundant and could survive multiple failures. In case of a total failure, the shuttle could be maneuvered to scoop up a drifting astronaut.
The Spacewalk
On February 7, 1984, aboard STS-41-B, McCandless and Stewart performed the famous first untethered spacewalk; McCandless ventured out 320 feet (98 m) from the orbiter, while Stewart tested the "work station" foot restraint at the end of the Remote Manipulator System.
In an interview in 2015, McCandless said -
The day before my walk, we reduced the pressure and increased the oxygen in the shuttle to get the nitrogen out of my bloodstream, otherwise I’d get the bends.
I’d been told of the quiet vacuum you experience in space, but with three radio links saying, “How’s your oxygen holding out?” “Stay away from the engines!” “When’s my turn?” it wasn’t that peaceful.
It was a wonderful feeling, a mix of personal elation and professional pride.
From www.airspacemag.com/… -
The image of McCandless, small and alone against the black sky, struck an emotional chord with the public, and for the last 30 years McCandless has had to explain why, contrary to many people’s expectations, he wasn’t scared. “I still have a memory of comfort,” he says, based on his intimate familiarity with the device he’d helped to create.
Of his famous spacewalk, he wrote in 2015: "My wife [Bernice] was at mission control, and there was quite a bit of apprehension. I wanted to say something similar to Neil [Armstrong] when he landed on the moon, so I said, 'It may have been a small step for Neil, but it’s a heck of a big leap for me.' That loosened the tension a bit."
On Feb 9, both astronauts performed another EVA to practice capture procedures for the Solar Maximum Mission satellite retrieval and repair operation, which was planned for the next mission, STS-41-C.
Here is a video of the post-flight conference -
STS-31
In April 1990, McCandless was Mission Specialist 1 on the STS-31 mission, which launched the Hubble Space Telescope.
Other Videos
Epilogue
McCandless said he was most proud that, later in life, children came up to him to say they'd seen the picture. He hoped it would inspire the next generation of explorers. "I like to encourage folks to look at that and say, 'Well, I can do better than that.' "
Farewell. And Thank You, Sir.
- NASA Remembers Astronaut Bruce McCandless II — www.nasa.gov/...
- Bruce McCandless II wiki — en.wikipedia.org/…
- Bio at NASA — www.jsc.nasa.gov/…
- Manned Maneuvering Unit — en.wikipedia.org/...
- Untethered — www.airspacemag.com/…
- That’s me in the picture: Bruce McCandless, 47, in the world’s first untethered space flight, February 1984 — www.theguardian.com/...
- Bruce McCandless, Capcom for Apollo 11, visits Kennedy Space Center, discusses historic mission — www.spaceflightinsider.com/…
- Piers Sellers, NASA Climate Scientist and Astronaut - RIP — www.dailykos.com/...