Our Solution are these glasses:
Public Innovative Solution Description
In space, there is no earth rotation and therefore no day-night rhythm and no real day for astronauts. This causes the astronauts' internal clock to get mixed up. We developed a pair of glasses that solve this problem by imitating the natural sunlight with LEDs. Our glasses can also delay and advance the internal clock through properly light pulses, which is useful when the astronaut needs to be awake and concentrated at a time at which he would actually sleep.
Problem Identification - Part One - Problem Overview
Due to the earth's rotation, there is a natural day-night rhythm on Earth. This rhythm, or rather the light associated with it, is the most important zeitgeber* for the human endogenous circadian (i.e. circa = approximately; dia = daily) clock. In space, there is no earth rotation and therefore no day-night rhythm and no real day for astronauts. Under these circumstances, the astronauts’ circadian rhythm cannot stay entrained**, which is a problem.
There are already many studies on problems with the circadian rhythms in spaceflight. The consequences of a disrupted circadian rhythm are concentration problems, poor productivity, bad sleep and generally an impairment of the astronauts' health. These consequences represent a major safety risk and can affect the success of their mission. In addition, long-term consequences are impaired glucose regulation and metabolism, increased risk of coronary heart disease and increased breast and prostate cancer risk
*a rhythmically occurring phenomenon that acts as a cue in the regulation of the body's circadian rhythms.
**synchronised with the environment
Problem Identification - Part Two - Detailed Solution Description
Light is the most important zeitgeber for the human internal clock. We have talked to several experts who have informed us that humans need light with the right color temperature at the right time of day to stabilize/entrain their circadian rhythm. This is based on evolution and the color gradient of natural sunlight.
The proposed color gradient to entrain the circadian rhythm: From 6 am to 12 o´clock, the warm white light with a color temperature of 2700K rises to the 6500K cold-white light. Due to the constant increase in color temperature, the astronaut has a good start into the day. In the following hours, productivity and concentration are on a high level. From 4 pm to 9:30 pm, the color temperature slowly drops back to the initial 2700K. This will prepare the person for falling asleep. For these exact values, we have talked to experts(Dr. Philip Novotny, Prof. Till Roenneberg, Dr. Elizabeth Klerman) and used the German Standard DIN SPEC 67600. Scientific explanation: In the eye, there are intrinsically photosensitive retinal ganglion cells(ipRGCs). These process light information and send the information to the suprachiasmatic nucleus (SCN), which is in the brain. The SCN then regulates the circadian rhythm through hormonal and neural output. Warm white light supports the production of melatonin, which decelerates body functions and prepares the human being for bed. Cold white light (increased blue content), on the other hand, reduces melatonin production and promotes the production of the stress hormone cortisol. This causes the metabolism to get activated and the body is programmed for daily use. With this knowledge, we developed a pair of glasses, which transmits the light of the previously mentioned color gradient to the eyes of the astronauts. The glasses have on the inside per eye one LED with 2700K and one with 6500K color temperature installed. By dimming the individual diodes, any color temperature can be mixed together. Further, we have added a diffusor-film, which scatters the light and makes it look very natural and removes glare.
We designed the frame digitally and used a 3D-printer to print it. The glasses have a built-in Arduino Pro Micro, which is a small form factor microcontroller. The Arduino is powered by a battery and controls the LEDs over PWM pins, so that we are able to dim them. Since the microcontroller and the LEDs consume very little power, the battery lifetime is about 6 months. We programmed the Arduino so that it makes the LEDs glow at the right intensity at the right time. Now, the astronauts just need to wear a pair of these glasses each. To set the glasses to one’s individual needs, we have programmed an intuitive software, with which the astronaut can enter his desired wake-up time and sleep time. The software calculates at which time which color temperature is needed and transmits the data to the Arduino Pro Micro via USB.
The only existing solution for the disturbed circadian rhythm can be found on the ISS. There, the ceiling lamps have a similar color gradient, also to stabilize the astronauts’ circadian rhythm.
But this solution has two problems. Firstly, there is a loss of the light’s color information, which occurs when the light from the LEDs reflects on non-white objects before it reaches the eyes. The other problem is the missing individuality. The ceiling lights send the same light information to every astronaut onboard the ISS. This may be good on the ISS, because usually, every astronaut on the ISS, gets up at the same time and goes to bed at the same time. But on a future Mars mission, permanent vigilance will be needed, because somebody always must control the equipment and the machines, which cannot be controlled from the ground (unlike on the ISS). That means that different astronauts have differently entrained circadian rhythms, so that all around the clock, somebody is awake. In this case, every astronaut needs individual light interventions.
Our solution solves these problems. The light’s color information doesn’t get lost, because it doesn’t get reflected. And most importantly, the individuality of light exposure is given through the glasses. Now, every astronaut can always individually get the light he needs, independent from the others.
Further, the astronaut can also tell the program, whether he has trouble with getting up in the morning or trouble with falling asleep in the evening. Based on this information, the program can modify the color gradient in a way that these problems are also solved. If the astronaut has trouble with falling asleep in the evening, he would get the warm-white light earlier than normal. If he has trouble with getting up in the morning, he would get the cold-white light earlier than normal.
And there is still another use for the glasses: Every time a capsule docks or undocks onto the ISS, a part of the crew needs to be awake to monitor the docking. For that, their concentration and alertness should be on maximum level. However, these dockings can also happen between 10:30 pm and 6 am, which is when the internal clock is promoting sleep. Through properly light pulses with a duration of 6.5h and 6500K, the glasses can shift the circadian rhythm by two hours per day(Source: Czeisler CA, Duffy JF. Effect of Light on Human Circadian Physiology). So if the astronaut who needs to be awake during the docking wears the glasses for the three days in advance, his circadian rhythm will be delayed by six hours. As a result, his inner clock is now adapted to the late docking. After that, the circadian rhythm can be moved back again by one hour a day. The astronaut can set this procedure with the user interface, as well.
So, our glasses solve two problems with one product.
Through tests and evaluation by professionals/experts, we are sure that the entrainment and shifting work out in the described way.