It is perhaps one of the best-known images of the 20th century. Floating free against the velvety blackness of space was Bruce McCandless II. For the first time ever, a human being was able to perform a spacewalk while completely untethered thanks to the Manned Maneuvering Unit (MMU), a jetpack-like device McCandless helped develop for over a decade. What is perhaps less well-known, but was unearthed during my recent processing of the Bruce McCandless II Papers, was the fact that, underneath the gold visor of his helmet, McCandless was wearing glasses.
It's comforting to realize that even larger-than-life figures like astronauts still suffer the same bodily indignities as the rest of us, something that Bruce McCandless knew all too well. In a 1990 memo, he recounted how he started to experience presbyopia around age 40. This happens when aging eyes gradually lose the ability to focus on nearby objects and is usually remedied with bifocal glasses, as his was. But when he first noticed that they didn't work nearly as well while conducting training underwater, his natural engineering instincts kicked in and he decided to fix it himself.
From an early age, McCandless' love of science and engineering was evident. As a junior at Woodrow Wilson High School in Long Beach, California, he came in first place in a statewide science competition, winning a full scholarship to the college of his choosing. He declined the prize and decided instead to attend the United States Naval Academy in 1954, following in the proud footsteps of his father and grandfather. There, he earned a bachelor of science degree, graduating second in his class and earning his U.S. Navy commission. In 1965, the young Naval aviator received a master of science in electrical engineering from Stanford University and, a year later, completed all the coursework for a PhD in plasma physics, though he left prior to completing his dissertation. To be fair, he had a pretty good excuse: At age 28, he was selected as the youngest member of NASA's Astronaut Group 5.
Astronaut Bruce McCandless II, October 1982. Credit: NASA Johnson Space Center.
Even within such a group of highly intelligent over achievers, McCandless' intellectual acumen stood out above the rest. Christopher Kraft, Jr., director of the Johnson Space Center, noted in a report that McCandless "…continue[s] to demonstrate his outstanding ability for technical excellence as an innovative and far-sighted officer… Technically, he is, without doubt, the most original thinker in the Astronaut Office. He routinely provides… the fresh perspective necessary to resolve complex issues involving hardware, software, and operational procedures." One example of McCandless' problem-solving inventiveness was the "McTether," a connection system that simplified and eased the ways in which astronauts could transport and use tools with spacesuit gloved hands without additional connectors. He received a patent for it in 1984 (#4,483,639) and it became a part of the standard tool kit on Space Shuttle missions.
The challenge with his eyesight began in 1978 while diving in the Marshall Space Flight Center's Neutral Buoyancy Simulator. Inside the giant tank was a mockup of the Hubble Space Telescope, allowing astronauts to practice repairs on the telescope under similar conditions to those experienced in space. As soon as he donned his pressure suit and helmet and submerged himself in the deep pool, things were distractingly blurry. McCandless knew that some of the visual distortion was caused by how light scatters in water but was convinced that another, unknown factor was at play. He initially brought the issue to NASA's Flight Medicine Division, who were unable to supply any answers.
This overall view shows STS-31 Mission Specialist (MS) Bruce McCandless II (left) and MS Kathryn D. Sullivan making a practice spacewalk in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool.
So, like any good scientist, he started investigating, hoping to find a solution. He theorized ultimately that the spherical shape of his bubble helmet resulted in what optometrists call a "minus lens effect." He contacted Dr. Jack L. Bridwell, a doctor of optometry, with his hunch. In the April 1984 issue of Optometric Management, Bridwell recalled the meeting: "I reviewed his data and confirmed that he had in fact solved the mystery. The curvature of the helmet when in water created a minus lens effect. With his scientific background and his engineering tenacity, McCandless consulted with all the necessary resources to become familiar with the lens maker's formula. He worked through the formula using the index of refraction for air versus that of water to reach his conclusions." The doctor prescribed new glasses that corrected for the distortion to be worn during underwater training. Problem solved! Well, for a while…
McCandless received his first flight assignment in 1984. As part of the STS-41-B mission, he would get to test the MMU that he'd devoted so many years to developing. A familiar obstacle soon became apparent: his glasses. For most of us, simple bifocals address the distances we encounter normally in daily life. While looking forward, the bottom part corrects near vision while the top corrects distance. We can easily adjust our heads in multiple directions while holding the line-of-sight constant.
As McCandless soon found, there was insufficient room to effectively do so inside of a helmet. This wasn't a concern during training in the Neutral Buoyancy Simulator as he only needed to see a short distance in front of him. The confines of the orbiter while in microgravity, however, meant that he needed to quickly alternate his field of vision between a variety of distances, including close and overhead. He called Dr. Bridwell again and, together, they came up with a solution: a binasal 15mm executive bifocal. In layman's terms: vertical bifocals.
Bruce McCandles II's sketch of his vertical bifocals invention.
They were narrow enough that, when the astronaut looked ahead, things appeared as they should. When he needed to view something up close, he could easily turn his head either left or right to see through whichever segment he chose. Additionally, it allowed him to see at a variety of elevation angles.
These were the very glasses he was wearing when, on February 7, 1984, he emerged from Space Shuttle Challenger's payload doors with the MMU on his back, into the vast expanse of space with no attachments. Bruce McCandless II's engineering prowess with both the MMU and his glasses made the seemingly impossible possible.
The Manned Maneuvering Unit (MMU) is a backpack propulsion device that gave astronauts mobility for extravehicular activities outside the Space Shuttle. It enabled them to maneuver within the payload bay or fly some distance away without needing safety tethers anchored to the vehicle.
The Bruce McCandless II Papers are now available for research at the Smithsonian's National Air and Space Museum Archives.
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