This is the twelfth in a series of reports from the HI-SEAS simulated Mars mission. Read others in the series here.
It’s late March at Gale Crater, the landing site of the Mars Curiosity rover. And according to the Mars Weather site, temperatures haven’t made it above freezing for weeks.
It’s a cold spring for Curiosity after a surprisingly warm winter. But the engineers knew what they were getting into when they designed the rover. They knew its systems would need to endure temperatures colder than -150 degrees Fahrenheit, and that they would need to operate reliably without much time above a balmy 32 degrees.
The same basic principle applies to any future human habitats on Mars. But in addition to sporting systems that can withstand harsh, fluctuating temperatures, a habitat must also survive a journey to and a landing on the planet, keep its inhabitants protected from harmful radiation and a toxic atmosphere (or lack thereof), and maintain comfortable indoor temperatures.
Speaking from experience in a simulated habitat I can tell you: Shirtsleeve temperatures are preferred.
You’re hot then you’re cold
It’s summer on Mauna Loa, where our HI-SEAS simulated Mars mission is about to begin its fourth and final month. Lately, I’ve been wearing T-shirts throughout the day, but for much of the mission I was comfortable in sweaters and thick socks.
There were even a few days early on when I wore gloves and always had a mug of hot tea in my hands. What I’m getting at is this: there have been some serious temperature fluctuations inside our home.
In fairness, this project wasn’t designed to field test a habitat for Mars. Our main objective has been to test the effects of menu fatigue on a long isolation mission and to try novel food systems for a far-flung interplanetary outpost. Therefore, our habitat isn’t completely sealed off from the outside, nor is it under pressurization. At an elevation of roughly 8,000 feet, we essentially live in a tent.
That said, there are still some interesting lessons to be learned on the thermal design of this dome.
Habitat heat maps
Our crew geologist, Oleg Abramov, brought with him a camera that reads the infrared light emitted from objects—it’s essentially able to snap multicolored pictures of cool zones and hot spots.
One of Oleg’s goals at HI-SEAS has been to create thermal maps of the habitat. These maps, in the short term, could help improve the ventilation and insulation of this structure. In the long term, these sorts of images could the aid the design and construction of future habitats.
From Oleg’s maps, there have been some clear observations so far. The dome cover, which is made of two layers of vinyl with some insulation between, is roughly the same temperature as the air outside. Lights and electronics produce a noticeable amount of heat. Unsurprisingly, heat rises and makes the upper level of the habitat, where our bedrooms are found, warmer than the lower level. On cold days and in the mornings and evenings, we use space heaters that glow white hot in the pictures.
Click and drag, or scroll, to pan through this panoramic view of the habitat.
Click and drag, or scroll, to pan through this panoramic infrared view.
Design tweaks for real Mars
One particular suggestion that arises from these images is that vents in the bedroom could be placed in the ceilings to improve airflow, as it can get quite hot up there around midday. Ultimately, though, designers of future simulated habitats would do well to consider high degrees of automation and regulation—something that the HI-SEAS habitat has in small doses with a carbon dioxide sensor and a couple of temperature sensors that feed data to an automated ventilation fan at the top of the dome.
Numerous temperature sensors and various methods of circulating air throughout the entire habitat could regulate temperatures further. Additionally, it could be important to recycle heat from sources like machinery, electronics, and even people. Such a heat-redistribution system could be an energy-efficient way to maintain comfortable indoor temperatures.
But for now, the HI-SEAS crew does much of the temperature regulation ourselves, including switching over to T-shirts and shorts on particularly warm days. Over the past week or so, the weather on our version of Mars has borne a striking resemblance to that of Hawaii. Too bad there’s no beach in sight.