Agriculture and food

Should a station grow food or ship it? The 2023 debate reached a fairly clear quantitative answer.

Key results

Grow or import (the main result)

  • Twark_Main's criterion. NASA long-term ECLSS dry food is 0.62 kg per person per day (+10% comfort, +5% packaging), about 4 t per person over 15 years. If a greenhouse's equivalent system mass (ESM: power, thermal, volume, consumables) exceeds 4 t per person, pack dry food plus a small salad garden Twark_Main, 2023-10-04.
  • Distance cancels out. Both resupply and the greenhouse must be shipped, so only the total duration of occupancy matters (short → stored food, long → greenhouse), unless ISRU exists at the destination Twark_Main, 2023-10-08; Twark_Main, 2023-10-10.
  • mikelepage's numbers. NASA food is ~668 kg per person per year including packaging. A grow system is ~20 t (~160 m²) per person, so break-even is ~30 years on pure mass.
  • With resupply every ~3 years (synodic), the advantage of shipping drops from 30× to 5× at the first resupply and 2.5× at 9 years.
  • Food shelf life is ~2 years, and palatability technology is at low TRL mikelepage, 2023-10-12.
  • Consensus: bulk food plus 5–10% fresh produce (<1 week old) ≈ a Western supply chain Twark_Main, 2023-10-12; Twark_Main, 2023-10-17. "There's no such thing as a free greenhouse" Twark_Main, 2023-10-12.
  • Coastal Ron's counterpoints. Perishables justify growing far from Earth. Residents demand it, and it helps food security, air freshening and mental health. Community co-op farms; import commodity staples Coastal Ron, 2023-10-12; Coastal Ron, 2023-10-16. Food preferences vary (~50% self-identified foodies) Coastal Ron, 2023-10-13.
  • Twark_Main's separation principle. Agricultural stations want maximum area and big flat light; habitation wants compact, round and heavy. Combining them gives absurdities (a GCR-shielded hot-air chimney, a 3 m shield around a farm). Vertical farming is fundamentally uneconomic, with "no free lunch/energy" Twark_Main, 2023-09-28. Grow lights are too bright for living spaces Twark_Main, 2025-03-06.
  • Small robotic high-rpm food stations separate from habitats lamontagne, 2023-01-16. LMT: one large greenhouse is more mass-efficient LMT, 2023-01-17.

Yields and areas

  • Biosphere 2 (~12,500 m²): 6.4 people/ha overall; with ~20% agriculture, ~32 people/ha on a low-calorie diet; high-intensity agriculture limit ~64 people/ha mikelepage, 2023-03-11.
  • lamontagne's greenhouse economics. A 100 m cylinder is ~2 ha; at 60 t/ha and ~400 W/m² it feeds ~240 people. The food is worth only ~$1.2M/yr retail (~$0.3M at the farm), so the greenhouse cannot be financed unless it costs ~$6–30M. That requires self-replicating factories; the same applies to O'Neill colonies lamontagne, 2023-01-28.
  • Energy: ≥50–60 kW per person for food and a mild ecosystem lamontagne, 2023-02-20. Crops need ~1000 W/m² of light lamontagne, 2026-09-15. Food energy depends on sunlight vs LED crops vs algae Vultur, 2024-08-06.
  • Hydroponics. 500 ft² of tower hydroponics (200 tubes) makes salad for ~30 people; lamontagne says 3–4× more is needed LarryCanuck, 2023-03-06; lamontagne, 2023-03-06.
  • mikelepage's asteroid barbell: ~0.25 ha of grow shelving (~240 t) along 2 × 52 m arms could support up to 16 people mikelepage, 2023-09-29.
  • Soil vs hydroponics. Soil beats hydroponics for biomass recycling: "Eastern Forest Dirt" starter packs; mulch, not till; engineered soils JohnFornaro, 2023-03-11; Twark_Main, 2023-03-13; Coastal Ron, 2023-03-13. Tree roots stay in the top 2–3 ft Coastal Ron, 2022-11-05.
  • High-density crops. Ship storable crops such as corn meal. Vertical farm example: Richmond VA strawberries, 4 M lb/yr Coastal Ron, 2025-03-07.
  • USU–Perigee wheat under high CO₂ LMT, 2023-01-17.

Partial-g plant research

Colony threshold

Open questions

  • What is the real ESM of a partial-g greenhouse? Nobody has built one.
  • Do crops and livestock reproduce normally at 0.38 g and 0.16 g?

Sources

Forum posts

  • high road, 2014-02-24 (reply #134): Test crops at Mars g. Post.
  • savuporo, 2015-09-07 (reply #628, 1 like): Eu:CROPIS plan. Post. Attachments: Eucropis_Satellit.jpg, Eucropis_Tomaten.jpg.
  • Paul451, 2019-01-07 (reply #1261): Food species. Post.
  • mikelepage, 2019-01-08 (reply #1275, 1 like): Eu:CROPIS launch. Post.
  • Coastal Ron, 2022-11-05 (reply #2318): Tree roots. Post.
  • lamontagne, 2022-11-15 (reply #2390): Colony threshold. Post.
  • lamontagne, 2023-01-06 (reply #2785): Outpost vs settlement. Post.
  • lamontagne, 2023-01-16 (reply #2934): Robotic food stations. Post. Attachments: Spacecolony2.jpeg.
  • LMT, 2023-01-17 (reply #2936): One large greenhouse. Post.
  • lamontagne, 2023-01-28 (reply #3144, 2 likes): Greenhouse economics (2 likes). Post. Attachments: Kalpana greenhouse.jpg.
  • lamontagne, 2023-02-10 (reply #3281): Hempsell sky farm. Post. Attachments: HempsellFeedingaSpacePopulationJBISVol70pp3-11.pdf, Skyfarm.PNG, Skyfarm2.PNG.
  • lamontagne, 2023-02-20 (reply #3357, 2 likes): 50–60 kW/person. Post.
  • LarryCanuck, 2023-03-06 (reply #3504): Tower hydroponics. Post.
  • lamontagne, 2023-03-06 (reply #3509, 1 like): 3–4× more. Post.
  • mikelepage, 2023-03-11 (reply #3549, 2 likes): Biosphere 2 densities (2 likes). Post.
  • JohnFornaro, 2023-03-11 (reply #3550): Soil starter pack. Post.
  • Twark_Main, 2023-03-13 (reply #3558): Mulch not till. Post.
  • Coastal Ron, 2023-03-13 (reply #3560, 1 like): Engineered soils. Post.
  • Twark_Main, 2023-09-28 (reply #4039): Separate farm vs habitat stations. Post.
  • mikelepage, 2023-09-29 (reply #4058): Grow chambers along arms. Post.
  • Twark_Main, 2023-10-04 (reply #4126): Dry food ≈ 4 t/person/15 yr vs greenhouse ESM. Post.
  • Twark_Main, 2023-10-08 (reply #4142, 1 like): Distance cancels; duration matters. Post.
  • Twark_Main, 2023-10-10 (reply #4147): Option D vs B. Post.
  • Coastal Ron, 2023-10-12 (reply #4154): Food growing in original design. Post.
  • Twark_Main, 2023-10-12 (reply #4155): No free greenhouse. Post.
  • Twark_Main, 2023-10-12 (reply #4159): Bulk + 5–10% fresh. Post.
  • mikelepage, 2023-10-12 (reply #4161, 1 like): Food mass numbers (1 like). Post.
  • Coastal Ron, 2023-10-13 (reply #4176): Foodies; attribute matrix. Post.
  • Coastal Ron, 2023-10-16 (reply #4184, 1 like): Import staples, grow perishables. Post.
  • Twark_Main, 2023-10-17 (reply #4199): Some ESM for onboard growing. Post.
  • LMT, 2023-11-05 (reply #4276): Eu:CROPIS damper. Post. Attachments: EUCROPIS attitude control hardware.png.
  • Vultur, 2024-08-06 (reply #4724): Sunlight vs LED vs algae. Post.
  • Twark_Main, 2025-03-06 (reply #4823): Grow lights too bright. Post.
  • Coastal Ron, 2025-03-07 (reply #4827): Vertical farm example. Post.
  • mikelepage, 2025-03-18 (reply #4837): Bottle garden cubesat. Post.
  • lamontagne, 2026-09-15 (reply #5107, 3 likes): Crops ~1000 W/m². Post. Attachments: Image51_002.jpg.

External references

  • DLR Eu:CROPIS mission.
  • Hempsell, M. "Feeding a Space Population". JBIS 70, pp. 3–11.
  • ESA MELiSSA.