How many NASA engineers does it take to change a lightbulb?

The question is no joke to NASA, which is investing $11.4 million to change out aging fluorescent lights in the International Space Station's U.S. On-orbit Segment. When NASA began considering the replacements, doctors realized they had an opportunity to tackle an entirely different problem: astronaut insomnia.

Sleep deprivation's fuzziness is an annoyance on Earth but dangerous in space. Although their schedule allows for 8.5 hours of shut-eye a day, astronauts average barely six hours, says NASA medical officer and flight surgeon Smith Johnston. A combination of floating, noise, variable temperature, poor air circulation, backaches and headaches, and a new dawn every 90 minutes confuses circadian rhythms. NASA hopes to fix at least part of the problem with new lamps.

Sleep scientists have found that when specific light receptors in our eyes are exposed to a particular wavelength of blue light, we feel more alert because the brain suppresses melatonin, a key hormone in regulating sleep. In contrast, red-spectrum light lets the melatonin flow.

The new lamps, from Boeing, comprise a rainbow of more than 100 LED bulbs cloaked by a diffuser, so they appear to be a single panel of white light, says Debbie Sharp, a Boeing senior manager. The fixtures have three modes, each with a subtly different hue: white light is for general vision; a cooler, blue-shifted light promotes alertness; and a warmer, red-shifted light triggers sleepiness. Boeing and its subcontractors expect to deliver 20 lamps in 2015.

In the meantime, scientists at institutions such as Harvard Medical School and Thomas Jefferson University are testing the lamps' efficacy.

The technology could one day be widespread back on Earth, perhaps illuminating hospital rooms, nuclear submarines, factories or classrooms. “Just because the world has been using fluorescent lighting for years doesn't mean it's the best,” says study collaborator Elizabeth Klerman of Harvard.