The fixtures have three modes, each with a subtly different hue: White light is for general vision; a cooler blue-shifted light promotes alertness (useful in the morning, during mid-sleep emergencies or amidst the schedule shifts that regularly slam their 24-hour rhythms from Houston time to Moscow time); and a warmer red-shifted light triggers sleepiness (helpful at bedtime). And LEDs have the additional bonus of being lighter, cooler, more durable, less toxic and more energy-efficient than fluorescents.
Boeing and its subcontractors, who are still tinkering with the final design, expect to deliver 20 lamps in 2015—right when the station will be down to its last spare bulbs. In the meantime the National Space Biomedical Research Institute has funded the labs of neuroscientists George Brainard at Thomas Jefferson University and Steven Lockley at Harvard University to test the lamps' efficacy. Brainard is studying whether the lights indeed help people in simulated ISS sleeping quarters doze off faster. Lockley is investigating whether the lights—in combination with caffeine—help volunteers perform complex tasks during night shifts.
"We're sure they'll have an effect—we just want to see what kind of effect they'll have, and the size of the effect," says study collaborator Elizabeth Klerman of Harvard Medical School's Division of Sleep Medicine.
Klerman predicts the technology will one day be widespread back on Earth, perhaps illuminating hospital rooms, nuclear submarines, factories, classrooms or "basically anywhere you have indoor lighting and want people to be alert at certain times," she says. "Just because the world has been using fluorescent lighting for years doesn't mean it's the best."