The Punch List
A running list of everything that still has to be invented, built, or proven before people can live off Earth. Numbered, kept, and never crossed off until it works.
Every construction job ends with a punch list. It is the list of everything that still has to be finished, fixed, or built before the owner will sign for the work. Nothing on it is optional. It doesn’t matter how good the rest of the job looks; until the punch list is closed out, the job isn’t done.
This is the punch list for living off Earth.
Every article in this magazine turns up something that may or may not exist yet — a machine, a process, a piece of equipment, a way of doing something we have not found anybody who has built and tested it. If it is out there already, we want to know, and we will say so here. Most of them aren’t glamorous. A pump-down tank for an airlock. A way to get rid of spent regolith. A beehive that works in a spinning room. They get mentioned once, in passing, and then the article moves on to the interesting part and the item gets forgotten.
Not here. Every one of them gets written down, numbered, and kept. What’s needed, why it’s needed, what’s hard about it, and which article turned it up. The list only grows. Nothing comes off it until somebody, somewhere, has built the thing and shown that it works.
Somebody needs to start working on this stuff now. If that’s you — if you’re building one of these in a garage or a lab or a company — tell us. We’ll close the item out with your name on it.
And if an item is wrong, write to us anyway. Some of these are stated as questions because we do not know the answer and are not going to pretend otherwise. Is this the only way to do it? Are there other options nobody here has thought of? If you know one, say so. This is the commissioning phase, and no job ever got signed off by the man who wrote the list.
John LangEditor
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PL-1
Lunar oxygen plant
- What’s needed
- A machine that takes regolith in one end and hands you breathable oxygen out the other — heat it with concentrated sunlight, run the reduction, capture the gas.
- Why
- Regolith is over forty percent oxygen by weight and the Sun is overhead for two weeks at a time. This is the single most-cited resource on the Moon and nobody has built the industrial version.
- What’s hard about it
- Everything after the chemistry. Feeding abrasive dust through a hot reactor without eating the machine. Sealing a furnace in vacuum. And the tailings: every ton of oxygen leaves you thousands of tons of spent, sintered regolith that has to go somewhere and be handled by something.
- Turned up in
- The Gas Nobody Budgets For
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PL-2
Airlock pump-down and gas recovery
- What’s needed
- A lock that pumps its air back into a holding tank before the outer door opens, instead of venting it to space.
- Why
- In a sealed habitat every airlock cycle throws away nitrogen you can never make again. The pump-down tank is the cheapest nitrogen mine there is.
- What’s hard about it
- Pumping a lock down to near-vacuum fast enough that people will actually wait for it, with a pump that runs for decades. Deciding how low is low enough, because the last few percent cost the most.
- Turned up in
- The Gas Nobody Budgets For
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PL-3
Martian atmospheric nitrogen separator
- What’s needed
- A compressor-and-refrigeration plant that pulls in Martian air, freezes out the carbon dioxide, strips the argon, and delivers nitrogen.
- Why
- Mars air is 2.6 percent nitrogen. It is the only free nitrogen feedstock in the inner solar system besides Earth, and a settlement that grows food needs it forever.
- What’s hard about it
- Six hundred pascals of inlet pressure means enormous volumes of gas moved for every kilogram delivered. Dust. Cold. And argon, which is nearly as abundant as the nitrogen and hard to tell apart from it by the cheap methods.
- Turned up in
- The Gas Nobody Budgets For
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PL-4
Whole-habitat leak detection
- What’s needed
- Instrumentation that finds a slow gas leak in a pressure hull before it becomes a big one, and tells you where it is.
- Why
- A habitat that loses two percent of its nitrogen a year is on a twenty-year clock. Nobody is going to fly a supply ship for a leak nobody has found.
- What’s hard about it
- A rotating hull with a hundred thousand joints, temperature swings, and no outside to sniff from. Telling a real leak from thermal breathing and airlock cycles.
- Turned up in
- The Gas Nobody Budgets For
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PL-5
Closed nitrogen loop for a sealed farm
- What’s needed
- A working waste-to-fertilizer chain — crew waste to ammonium, ammonium to nitrite, nitrite to nitrate, nitrate to crops — that runs unattended for years.
- Why
- The laboratory version exists in Europe. The version that feeds a crew of fifty for a decade without a PhD watching it does not.
- What’s hard about it
- Ammonia is both your fertilizer and a hazard in a sealed can. The nitrogen-fixing enzyme is poisoned by the oxygen you are also trying to make. One system being asked to do two opposed things.
- Turned up in
- The Gas Nobody Budgets For
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PL-6
A worm colony that ships and survives
- What’s needed
- A container, a starter feed, and a cocoon reserve that gets a working earthworm colony from Earth to a habitat alive, and restarts it after a crash.
- Why
- Worms build soil. No soil, no crops. The last closed-ecology experiment lost its pollinators and nearly lost its air; nobody has designed the worm bed as flight equipment.
- What’s hard about it
- Worms breathe through wet skin and drown in flooded dirt; they need something already dead to eat, which a sterile world does not have. Which species, in what numbers, alongside what else.
- Turned up in
- Top of the Loop, Bottom of the Loop
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PL-7
A beehive for a rotating room
- What’s needed
- A hive, forage plan, swarm plan, and lighting spec that keeps pollinators alive inside a sealed, spinning habitat.
- Why
- Most fruit, nut, and vegetable crops need a pollinator. Biosphere 2 lost every bee it had.
- What’s hard about it
- Year-round forage. Somewhere for a swarm to go. Ultraviolet in the light, because bees navigate by it and greenhouse glass blocks it. And whether a bee can fly straight through Coriolis forces no bee on Earth has ever felt.
- Turned up in
- Top of the Loop, Bottom of the Loop
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PL-8
Grow lights that let a plant sleep
- What’s needed
- Lighting and control that delivers Alaska-summer growth rates without the injury continuous light does to plants that never get a dark period.
- Why
- Light is the throttle on a sealed farm, and running it wide open damages the crop.
- What’s hard about it
- Every species has a different tolerance. The controls have to know the difference, and the power system has to live with the swings.
- Turned up in
- Light Is the Throttle
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PL-9
Wind for a sealed forest
- What’s needed
- Air movement inside a habitat that loads a tree the way weather does, so it builds wood that can hold itself up.
- Why
- Biosphere 2’s trees grew fast and weak under ducted circulation and fell over. Ducted air is not weather.
- What’s hard about it
- Making real gusts in a closed volume without wasting power or blowing the soil around.
- Turned up in
- Light Is the Throttle
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PL-10
A ground-based mass driver
- What’s needed
- A twenty-mile evacuated tube under a mountain, curving up to exit on the flank, that launches freight pods one after another on electromagnets — cargo only.
- Why
- Everything else in this magazine needs tonnage in orbit, and rockets are the wrong tool for boring freight.
- What’s hard about it
- Cooling the magnets. Keeping twenty miles of tube at vacuum. Opening the exit fast enough and closing it again. And the pod surviving the air at the top.
- Turned up in
- Out the Side of the Mountain
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PL-11
An orbital catch tug
- What’s needed
- A vehicle that meets a freight pod at the top of its arc, catches it, and delivers it where it needs to go.
- Why
- A mass driver can only throw. Something has to catch, or every pod needs its own rocket.
- What’s hard about it
- Rendezvous with something arriving at hypersonic speed on a ballistic arc. Grabbing it without breaking it. Doing it a hundred times a day.
- Turned up in
- That’s Not a Rocket, It’s a Freight Train
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PL-12
Asteroid regolith to printable metal
- What’s needed
- A process, aboard the refinery ship, that turns crushed asteroid into powder or wire a printer can use.
- Why
- There will never be a steel mill in space. Whatever replaces it starts here.
- What’s hard about it
- Separating the metal from everything else without gravity, water, or air. Getting the powder to a grade a printer will accept. Doing it for years without a parts run.
- Turned up in
- Send the Refinery, Not the Ore
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PL-13
Robots that build the barrel
- What’s needed
- A team of machines that takes printed or cast panels and assembles a spinning habitat in orbit, joint by joint, without people outside.
- Why
- You cannot launch a habitat big enough to spin. You launch a shipyard, and the shipyard has to be robots.
- What’s hard about it
- A hundred thousand joints, each of them a leak path. Cold, vacuum, thermal cycling. Inspection and rework by a machine.
- Turned up in
- Launch the Parts, Not the Ship
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PL-14
A sealed habitat we run on Earth first
- What’s needed
- A full-size closed habitat, on the ground, commissioned and lived in for years before anything like it leaves the planet.
- Why
- Biosphere 2 was phase one and it nearly killed the people inside. The oxygen went to 14.5 percent because concrete ate the carbon dioxide and nobody had that on a drawing.
- What’s hard about it
- Money and patience. It is not glamorous to run a test for five years. But that is what commissioning is.
- Turned up in
- Commission It First
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PL-15
A list of which animals earn a berth — and clean stock to fill it
- What’s needed
- A worked-out roster of food animals for a closed habitat, with the mass, feed, oxygen and waste cost of each one written down next to what it gives back. Then breeding stock raised pathogen-free on Earth and certified before it ever goes up.
- Why
- Every animal you carry is a permanent draw on air, water and volume. Some pay for themselves twice over — a chicken eats bugs and scraps nothing else will touch and gives back eggs and manure. Some do not. Nobody has published the honest ledger.
- What’s hard about it
- The animals fight each other. Chickens eat worms, and the worms are the soil engine. Rabbits alone will starve you on lean meat with no fat. Waste from birds and mammals is hard to collect in a way fish waste is not. And a pathogen-free supply chain for livestock is a whole industry that does not exist for this purpose.
- Turned up in
- Top of the Loop, Bottom of the Loop
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PL-16
A crop list where every plant pays rent twice
- What’s needed
- A selected set of food crops scored on oxygen produced, calories, protein, fat, vitamins, and what the inedible half is worth as feed for the rabbits, the chickens and the worms.
- Why
- Mass is the whole budget. A plant that only makes calories is a plant you are carrying at full price. The fat question alone rules out a lot of lists — you need an oil crop or the diet fails no matter how much you grow.
- What’s hard about it
- Pollination. Some of the best candidates need an insect you may not want to carry. And the scoring has never been done as one table — the agronomy, the nutrition and the life-support numbers all live in different papers.
- Turned up in
- Fish, Salt, or Dirt
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PL-17
The medicinal plants, and who still knows how to use them
- What’s needed
- A set of medicinal and culinary herbs chosen for a sealed habitat, and the knowledge of how to prepare and dose them carried up alongside the seed.
- Why
- A resupply run is months away at best and may not come at all. A pharmacy that grows back is worth volume. People also want these plants for reasons that have nothing to do with medicine, and morale is a life-support system too.
- What’s hard about it
- Dose and potency vary with the plant and the growing conditions, and a habitat’s light and soil are not a field in Provence. Much of this knowledge is old, oral, and unevenly true — separating what works from what is folklore is real work nobody has done for this purpose.
- Turned up in
- Fish, Salt, or Dirt
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PL-18
A way to get live animals there — is shipping embryos the only answer?
- What’s needed
- Some means of stocking a sealed habitat with large animals. Shipping them alive is the obvious way and may be the worst one. The alternative on the table is carrying frozen embryos and raising them at the other end — which requires something to raise them in, and a mother to start the chain.
- Why
- Goats, and anything else that eats rough forage and gives milk, have to get there somehow. A live animal in transit needs feed, water, air, heat, and handling, and every part of its world changes at once — enclosure, motion, noise, light, and unusual gravitational forces. A frozen embryo needs none of that and does not care how long the trip takes. It is also far easier to certify clean than a live goat is.
- What’s hard about it
- The two ends are demonstrated and the middle is not. Frozen mouse embryos have been thawed and cultured aboard the International Space Station for four days, reaching blastocyst with no detected DNA damage, and freeze-dried mouse sperm has come back from nine months in orbit and produced healthy offspring. At the other end, an extrauterine device has carried premature lambs for up to four weeks with normal lung and brain development — but that device finishes a fetus that is already most of the way there. Nobody has taken an embryo from blastocyst to a live birth in a machine, in any species. That middle stretch, implantation through viability, is the gap.
- The question
- Is this the only way to make it happen? Are there other options — and is anybody working on the middle? If you know, write to us.
- Turned up in
- Fish, Salt, or Dirt
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PL-19
A seed-saving program for one air volume
- What’s needed
- A written, tested procedure for keeping open-pollinated varieties true inside a habitat where every crop shares one air volume and the insects go where they like: isolation by timing, bagged blossoms, hand pollination, seed drying and storage on board, germination testing, and a person whose job it is.
- Why
- The editorial position of this magazine is heirloom seed only, and that position is worthless without the discipline that keeps the seed pure. A variety that crosses in year three is a variety you no longer have.
- What’s hard about it
- On a farm you keep varieties apart with distance. In a barrel there is no distance. Squash crosses with squash and cabbage with kale, and the standard isolation tables were written for fields, not for a few thousand square meters under one roof. Nobody has written the version for a habitat.
- The question
- Who has run a seed-saving program in a single greenhouse for decades without losing varieties? What did it take? Write to us.
- Turned up in
- Heirloom, or Nothing
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PL-20
The crop table — every candidate scored against every loop
- What’s needed
- One table. Every candidate crop down the side; calories, protein, fat, vitamins and minerals, oxygen and carbon dioxide, water transpired, feed value of the inedible fraction, biomass returned to soil, processing equipment required, seed-saving burden, and morale across the top. Scored, totaled, and fought over.
- Why
- Nothing else on the crop side can be settled until this exists. Growing area, hull diameter, lighting load, and the entire animal question all fall out of it.
- What’s hard about it
- Every column is a different discipline, and they are usually measured in different units by people who do not attend the same conferences. The agronomy exists in pieces; the piece nobody has done is the scoring of all of it as one table, for a closed habitat, on open-pollinated seed.
- The question
- Has anyone built this and simply not published it? If you can fill in even one column properly — one crop, one loop, real numbers — write to us. We will publish it and credit you.
- Turned up in
- Watney Was Lucky
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PL-21
A mountain flank that can take a mass driver exit
- What’s needed
- The exit bore itself: engineering the place where a twenty-mile evacuated tube breaks the surface on the upper flank of a working volcano — Mauna Kea or Mauna Loa, below the summit — without collapsing the mountain around the tube or the tube under the mountain.
- Why
- The whole mass driver depends on this one hole existing. Everything else in the design assumes the tube can come out of the rock at speed and stay open.
- What’s hard about it
- Nobody has bored a launch tube exit through the flank of a live volcano. Tunneling crews know rock, and volcanologists know this mountain, and those two groups have never had to solve this together.
- Turned up in
- Out the Side of the Mountain
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PL-22
Closed-loop cooling for a mountain’s worth of electromagnets
- What’s needed
- A liquid cooling loop through every electromagnet plate along the twenty-mile tube, dumping its heat into an underground chiller and into the surrounding rock as a heat sink.
- Why
- Firing magnets in sequence at this scale throws off more waste heat than any coilgun built to date. Heat that isn’t carried away ends the launch schedule.
- What’s hard about it
- The loop has to survive repeated high-current pulses, continuously, for decades — sealed underground where nobody can get to it once it’s buried.
- Turned up in
- Out the Side of the Mountain
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PL-23
An orbital tug that can actually catch a freight pod
- What’s needed
- The catch itself, not just a tug that exists. A mechanism that matches velocity with an unpowered pod at the top of its arc and takes hold of it without damaging either vehicle.
- Why
- A mass driver can throw; it cannot steer. Everything downstream of the launch depends on a catch that works every time.
- What’s hard about it
- Closing speed and alignment tolerances, with no active guidance on the pod’s end to help. The tug does all the work, and the pod gives it nothing.
- Turned up in
- That’s Not a Rocket, It’s a Freight Train
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PL-24
Lunar launch and support facilities for avatar robots
- What’s needed
- The ground infrastructure that has to be on the Moon before avatar robots can be landed and put to work — somewhere to land, recharge, dock, and be serviced — and a way to push operations outward from that first site.
- Why
- A robot with nowhere to recharge or get fixed is a robot that fails alone, and a failed robot on the Moon stays failed.
- What’s hard about it
- All of it has to be built and kept running before there are any people living there to maintain it.
- Turned up in
- The planned lunar avatar-robots piece — article forthcoming
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PL-25
A single-occupant emergency oxygen pod grown from one plant
- What’s needed
- A sealed pod in which one plant, likely wheatgrass, is a person’s entire oxygen supply — with output that rises when the occupant works harder and breathes out more carbon dioxide.
- Why
- A last-resort life support fallback that needs no power plant and no spare parts. The editor saw one demonstrated on a tour of the Houston space center in the 1990s.
- What’s hard about it
- Nobody has published how to engineer that one-plant balance into something reliable and repeatable, or how to scale it.
- Turned up in
- The editor’s own visit to the Houston space center — article forthcoming
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PL-26
A robot that clips onto its own rail without wheels or magnets
- What’s needed
- A placing robot that grips a panel’s tongue-and-groove rail with two fingers — tight enough to hold its position while it pushes the next panel home, then loose enough to let go and travel.
- Why
- The same groove that locks the panels together has to double as the robot’s track. No separate rail, no extra mass.
- What’s hard about it
- A grip that holds firm under load and still releases cleanly, with nothing rolling and nothing magnetic.
- Turned up in
- A Thousand Garages
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PL-27
Inspecting and insulating a hundred thousand joints across a multi-wall hull
- What’s needed
- A way to check every seam of a three- or four-wall habitat shell for leaks and damage, and to keep the insulating gaps between the walls working, for the life of the structure.
- Why
- A multi-wall hull only beats a single shell if every one of those joints stays sound and sealed.
- What’s hard about it
- Scale. No habitat has ever had this many joints to inspect, and once the walls are assembled, none of them can be reached.
- Turned up in
- The magazine’s habitat and panel design work — article forthcoming
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PL-28
Printed stainless parts that survive vacuum cold-welding and metal fatigue
- What’s needed
- A treatment or a redesign for binder-jetted 316L stainless panels, so they don’t gall together in vacuum — where clean metal surfaces can fuse on contact — and don’t fail early from the shorter fatigue life of sintered metal.
- Why
- The whole panel plan depends on printed parts holding up structurally in orbit for decades.
- What’s hard about it
- Binder-jetted stainless is measurably weaker, and worse in fatigue, than ordinary wrought stainless — a point this magazine’s own printing article first got wrong.
- Turned up in
- A Thousand Garages
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PL-29
A positioning satellite constellation for a new planet
- What’s needed
- A GPS-equivalent network in orbit around Mars, or any body being settled, put there before serious surface work begins.
- Why
- Nothing on the ground can be reliably located, mapped, or navigated without it.
- What’s hard about it
- Deploying and maintaining a full constellation around a planet with no infrastructure and no crew on the ground to help.
- Turned up in
- Plant the Satellites First — article forthcoming
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PL-30
Remote-controlled robots that work through real signal lag
- What’s needed
- A control system that lets an operator on Earth or in orbit drive avatar robots on the Moon or Mars despite the communication delay. These robots are driven, not autonomous.
- Why
- A robot that freezes or drifts off task during a lag window fails at exactly the moment nobody can react.
- What’s hard about it
- The delay grows from about a second and a half at the Moon to as much as twenty minutes each way at Mars. Joystick-style control stops working well before that.
- Turned up in
- The planned lunar avatar-robots piece — article forthcoming
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PL-31
A shaft drilled up through a mountain for a lunar base
- What’s needed
- A vertical bore connecting an underground lunar habitat to a radiation-shielding glass dome on the summit, carrying structure, utilities, and people between the two.
- Why
- The growing space and living quarters go underground for shielding. The dome gives the people living there a view out over the Moon, and back to Earth.
- What’s hard about it
- Boring and lining a stable shaft in lunar rock with no atmosphere, no water for conventional drilling, and no way to call in more equipment if something goes wrong halfway up.
- Turned up in
- The planned lunar base piece — article forthcoming
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PL-32
A load path for a spinning sphere versus a spinning tube
- What’s needed
- A worked structural analysis of a spherical rotating habitat, where everything placed inside pushes outward on every wall at once — so the inner structural layer has to be very strong while the outer layer can be comparatively thin.
- Why
- The sphere has been raised as an alternative to the cylindrical barrel, and nobody has worked out whether its load path actually holds up.
- What’s hard about it
- No rotating habitat of either shape has ever been built. This load distribution has only ever been reasoned through on paper.
- Turned up in
- The magazine’s habitat and panel design work — article forthcoming
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PL-33
A redundant, whole-habitat oxygen supply, not a single system
- What’s needed
- Oxygen generation at barrel scale on two independent paths, the way Earth runs on both ocean plankton and land plants — not one plant-only system and not one machine-only system.
- Why
- Biosphere 2 ran its oxygen too close to a single point of failure and paid for it: down from 20.9 to 14.5 percent over sixteen months.
- What’s hard about it
- Fitting two genuinely independent paths, biological and mechanical, into one sealed structure without either one starving the other of space, power, or carbon dioxide.
- Turned up in
- Commission It First
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PL-34
Waste disposal and CO2 scrubbing for a closed habitat, on its own
- What’s needed
- A full accounting of where human, animal, and crop waste goes, and how carbon dioxide is pulled back down to safe levels — built and proven as its own system, not assumed to ride along inside the nitrogen loop.
- Why
- A sealed habitat has nowhere to send anything away. Every waste stream has to be processed, stored, or converted on site, indefinitely.
- What’s hard about it
- Both get mentioned as a line item inside other systems. Nobody has worked either one as a standalone, sized, engineered system.
- Turned up in
- Commission It First
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PL-35
An affordable large-format printer or CNC machine for garage panel-making
- What’s needed
- A machine with a bed well beyond today’s roughly ten-inch consumer printers, still cheap enough for an ordinary garage, that can turn out larger structural panels.
- Why
- The whole distributed-manufacturing idea depends on ordinary people worldwide being able to afford the equipment, and today’s affordable machines top out too small.
- What’s hard about it
- Print volume, precision, and material strength all get harder to hold at once as the bed grows, and the price climbs fast with size.
- Turned up in
- The magazine’s habitat and panel design work — article forthcoming
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PL-36
A durable way to personalize a panel for generations
- What’s needed
- An engraving or stenciling method built into the panel-making process, so a maker can put a name, a date, or a family name on a panel and have it last decades in orbit — through radiation, thermal cycling, and vacuum.
- Why
- Ordinary people worldwide building panels that carry their names, as a legacy their grandchildren can point to.
- What’s hard about it
- Any mark added to a structural panel must not become a stress riser or a weak point in the very joint that holds the habitat together.
- Turned up in
- The magazine’s habitat and panel design work — article forthcoming
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PL-37
A UV-C scrubber loop for nitrous oxide
- What’s needed
- A sealed air-treatment loop that pulls habitat air through a UV-C chamber, in the range of roughly 200 to 240 nanometers where nitrous oxide breaks apart, and returns it clean — with the lamps shielded so none of that light ever reaches the crew, the crops, or the seals.
- Why
- Soil and compost give off nitrous oxide all the time. On Earth it drifts up to the stratosphere, where hard ultraviolet sunlight breaks it down for free. A sealed habitat has no stratosphere, so it simply builds up — Biosphere 2 saw exactly that. At high enough levels it interferes with vitamin B12 and the nervous system.
- What’s hard about it
- The pieces exist; UV-C lamps are standard in hospital and water-treatment sterilizers. Nobody has purpose-built one as an atmospheric scrubber for a sealed habitat, sized it, and run it for years. And the same light that breaks nitrous oxide also shreds DNA and degrades plastics and gaskets, so the loop has to be built to contain it for decades.
- Turned up in
- Research for The Gas Nobody Budgets For