Link here https://t.co/3Is5Q8Q1gI. (I shared this yesterday, but forgot that this site spikes such links)
— Pinboard (@Pinboard) February 27, 2026
So. Many. Moving. Parts!…Maciej Cegłowski, aka Pinboard, at his SubStack Mars for the Rest of Us, with “A Primer on Long-Duration Life Support”:
Life support is the biggest technical obstacle to the human exploration of Mars.
This fact makes people mad, because there are all kinds of other obstacles that are fun to solve (orbital refueling, landing heavy payloads, making rocket fuel out of Martian air), and life support has a fun factor of zero. It is a thankless world of dodgy sensors, failing bearings, and bacteria trying to grow on absolutely everything.
But if we want to get to Mars alive, we need for this stuff to work.
Requirements
An astronaut in space needs 840 grams of oxygen, 2.8 kilos of water, and 1.8 kilos of dried food a day to stay alive. They also appreciate the little touches, like water to wash with (0.7 kg), fresh clothes (1.5 kg per week), wet wipes (0.2 kg/day) and a toilet (1.4 kg for canisters and wipes).On the output side, each astronaut exhales around a kilo of carbon dioxide and pees out a liter and a half of urine. They also produce a fairly small quantity of feces and menses (though many women opt to medically induce amenorrhea during space flight)…
On shorter missions like Apollo (~12 days) or Shuttle flights (~14 days) it makes sense to pack everything a crew needs with no attempts at recycling. In this paradigm, carbon dioxide can be scrubbed from the cabin air with disposable lithium hydroxide cartridges; everything else is carried along in the space version of a picnic basket.
On longer missions, trying to carry single-use supplies gets unwieldy. A crew of four on a 1,000 day mission to Mars would need 48 tons of consumables, about equal to the mass of the entire spacecraft. And even if mass were unlimited, there simply wouldn’t be enough room to fit everything on board.
So past a threshold of about 30 days, you have to make some attempt at recycling…
Food
Food may be my favorite technical barrier to Mars travel, because everyone assumes it has been solved, or that it is easy to solve, while the people working on it mop the sweat from their brow during the day and try keep the shaking in their hands from rattling the ice cubes in their whisky glass at night.Astronauts have hated space food ever since the first meat cubes came back uneaten from Project Gemini. Even on the ISS, where fresh foods are often available, getting crews to eat adequately is a struggle. Whether it’s because the stomach senses satiety differently in zero gravity, or because the space station smells like a toilet, crews have historically consumed only 80% of their rations.
On a multiyear mission, such a calorie level would lead to malnutrition and embarrassing deficiency diseases like space scurvy. So we need to come up with ready-to-eat meals that are nutritious, storable for five years without refrigeration, and appetizing enough that a crew can eat them for a thousand days without wanting to murder each other.
These kinds of meals don’t exist. Their closest equivalent is the military meal ready-to-eat (MRE). But as any soldier or prepper will tell you, an MRE is not something you can subsist on. The meals are not nutritionally complete, and soldiers’ own backronym for the combat ration (meals refusing to exit) sheds light on a notorious shortcomings. Defense department guidelines stress that soldiers should not be fed MREs for more than 21 days at a time…
Much more information, and useful charts, at the link. (I am mildly fixated on the fact that astronauts use the same indicator for discarding their disposable undergarments that my teenager brothers used to decide when to change theirs.)
Excellent Read: <em>Mars, Beyotches!</em>Post + Comments (32)
