NASA - Lighting in Outer Space - Learning Objectives

• What are the challenges in lighting space travel?
• What is Circadian Entrainment?
• What environments on earth simulate space travel?

Adjusting lighting for healthy Circadian System

Russian cosmonaut Sergey Ryazanskiy, Expedition 37 flight engineer, attired in a Russian Orlan spacesuit, is pictured during a session of extravehicular activity. 2013

The Key to Better Sleep in Space? Some Nice, Colorful Light

"Red-shifted light allows sleep, and bluish light wakes you up, so the next question is whether astronauts can sleep better and then perform better with wavelength-controlled illumination. By 2016, NASA plans to install the bulbs in the real crew quarters—and its astronauts can get some well-deserved shut-eye. ..." [1]

At-sea trial of 24-h-based submarine watchstanding schedules with high and low correlated color temperature light sources.

"United States Navy submariners have historically lived with circadian disruption while at sea due to 18-h-based watch schedules. Previous research demonstrated that circadian entrainment improved with 24-h-based watch schedules. Twenty-nine male crew members participated in the study, which took place on an actual submarine patrol. ... " [2] April 2015

Circadian System

The sun plays an important role in our wake and sleep cycles, know as your Circadian Rhythm.  Our ancestors evolved under the natural cycles of daylight and dark nights.

In artificial environments: outer space, Arctic research centers, and undersea natural light must be simulated with electric lighting.  Light is energy that influences mind and body - many chemicals in our bodies are controlled by light.  Melatonin is produced at night to direct our bodies to sleep. Exposure to blue tinted light can delay sleep for as much as two hours.

Bold Endeavors: Lessons from Polar and Space Exploration 

The recognition of our circadian system and external influences is fairly recent and much research continues today.  As Jack Stuster points out in his 1996 book, Bold Endeavors: Lessons from Polar and Space Exploration, the term circadian rhythms was coined in 1959  by Franz Halberg from the Latin circa (about) and diem (a day).  In 1982 scientists were discussing internal circadian rhythms and external zeitgebers (from the German for time givers).  
"Almost all physiological, psychological, and behavioral parameters, including body temperature, production of serum and urinary corticosteroids and electrolytes, cardiovascular functions, muscle strength, alertness, mood, and memory, follow circadian rhythms. Although circadian rhythms are generated internal to an organism, they are regulated by external cues, primarily the cycle of light and darkness. ... If the individual is isolated without access to any time cues, however, the sleep / wake cycle and body temperature rhythms drift toward later times each day and are expressed in free-running periods of 25.4 hours; at this rate an individual's sleep /wake cycle could drift nearly 10 hours per week in the absence of diurnal cues. ... The imposition of period and phase control by environmental cues is called entrainment. ... Earth and Mars have nearly identical rotation rates (twenty-four hours and thirty-seven minutes for Mars) Earth and Mars also share a similar sequence of seasons because their polar axis are tipped almost identically." [3]
Former Astronaut Jack Stuster concludes this chapter, Study Results,  with eight recommendations regarding sleep during long-duration space missions: schedules, tasks, zeitgebers, sleep hygiene, sleep chambers, exits, safety, shift work, and communication devices.

Circadian Brain

Brain Signals

Circadian Response Curve, blue light (480 nanometers) during the day, helps promote healthy sleep with melatonin production at night. Photopic vision, the ability to see colors, peaks in daylight (550 nanometers). Selecting lighting containing correct and varied spectral output becomes critical in artificial illuminated environments of space, Arctic, and undersea. 

Footnotes

1. Space Sleep http://www.wired.com/2015/06/sleeping-in-space/
2. At-sea trial of 24-h-based submarine http://www.ncbi.nlm.nih.gov/pubmed/25838419
3. Bold Endeavors: Lessons from Polar and Space Exploration  By Jack Stuster, 377 pages, Paperback Published 2011  http://www.anacapasciences.com/staff/jstuster/ 

Photo Credits

• NASA Astronaut By NASA
  
• International Space Station Sleeping Quarters Replica, by Photo Harry Gould Harvey IV
  
• Submarine (U.S. Navy photo by Mass Communication Specialist 2nd Class Amanda R. Gray/Released)160418-N-UD469-038  https://www.flickr.com/photos/usnavy/26456265871
  

Related Topics

Circadian System, Light Therapy, night lighting.