NASA's exploration requires research into how light affects both humans and plants: John Glenn’s first trip into Earth orbit lasted just under five hours, but today, astronauts regularly stay six months or longer on the International Space Station. Experiencing over a dozen sunrises and sunsets each day means an astronaut’s biological clock tends to be in the wrong time zone. And for longer deep space missions, NASA needs to develop ways to grow food without relying on sunlight.
NASA's lighting research, however, has had benefits far beyond space. It has helped develop biologically oriented LED technology for everyday life on Earth – giving people better rest and helping plants grow.
Lightbulb Moments
From 1997 to 2017, the National Space Biomedical Research Institute (NSBRI) looked into how long-duration spaceflight affected people, funded with grants from NASA’s Johnson Space Center in Houston. One area of interest was light sources and how they affected brain activity. NSBRI funded two professors, Thomas Jefferson University’s George Brainard, and Harvard Medical School’s Steven Lockley, to learn more.
Lockley and Brainard’s research found that exposure to excess blue light at the wrong time could throw off people’s body clocks. This happened because the body’s production of melatonin, a key hormone for managing circadian rhythms, was inhibited when certain wavelengths of blue light hit photoreceptors in the eyes.
When the fluorescent lighting fixtures on the space station needed to be replaced in 2011, NASA looked to the growing field of solid-state light-emitting diodes (LEDs). Solid-state means that there’s no physical reaction creating light, unlike an incandescent bulb or fluorescent plasma. In creating a new lighting system, the findings of the NSBRI’s research played a big role.
“When NASA started looking into [LED fixtures], the industry didn’t even have standards for solid-state lighting. They didn’t have any information, certainly not a lot of research on large-scale implementation of circadian lighting,” said Toni Clark, testing lead for spacecraft lighting at Johnson.
Researchers at Johnson and engineers at NASA’s Kennedy Space Center in Florida worked together on the Solid-State Lighting Assembly (SSLA) for the space station. The lamp module was primarily built by Bionetics Corporation, which also had labs and manufacturing facilities onsite at Kennedy. The new lighting modules, installed in 2016, consumed far less energy and emitted far less heat than previous fluorescent lighting on the station. In addition, they changed color, temperature, and intensity in a 24-hour cycle, in accordance with the NSBRI’s circadian lighting research.
The change paid off. Astronauts reported feeling better-rested. Other LED modules helped in plant growth experiments on the space station, with the lights providing the right wavelengths for photosynthesis.