Radiation environment and dose limits

How much radiation a station's crew receives in each location, and how much is acceptable. The thread's biggest single driver of mass.

Key results

Environment by location

• Equatorial LEO (ELEO) is the thread's consensus location for near-term stations.
• Al Globus (2014, 2015): a 1 g station in equatorial 500–600 km LEO needs little or no shielding daveklingler, 2015-02-23; LMT, 2018-07-08.
• At <5° inclination and ~600 km: GCR <40 mSv/yr unshielded, orbital lifetime ~20 years mikelepage, 2018-11-01. Inclination under 5° avoids the South Atlantic Anomaly LMT, 2018-07-08.
• mikelepage and Al Globus tabled yearly dose against altitude and inclination: the good window is 400–600 km and 0–20° mikelepage, 2022-11-29.
• Lowering from 400 to 250 km cuts MMOD impacts ~90% and dose ~50% LMT, 2018-07-05.
• In LEO, Earth blocks about half the sky, so GCR dose is roughly half the deep-space value Twark_Main, 2022-11-08; Robotbeat, 2022-12-17.
• A LEO station is far more mass-efficient than a deep-space one Coastal Ron, 2019-05-10. Habitant: in ELEO, shielding is hundreds of kg/m² vs 10+ t/m² in deep space (50×); a 24 × 32.6 m cylinder needs 6 vs 333 Starship launches of shielding Habitant, 2026-09-15.
• LMT: no shielding is needed in extreme VLEO (EVLEO) LMT, 2023-05-24; LMT, 2023-01-07.
• A 500 km sun-synchronous orbit has high radiation mikelepage, 2019-09-04.
• EML-1 and L4/L5: harsher radiation and more ΔV Twark_Main, 2022-12-18. Globus (NSS "An Easier Way"): ELEO is realistic and L5 unrealistic because of radiation LMT, 2024-03-16.
• Deep space:
• 20 g/cm² of PE (22 cm) gives ~300 mSv/yr, about 15× the NASA recommendation lamontagne, 2022-11-01.
• 10 g/cm² of Al gives ~750 mSv/yr in deep space and about half that in LEO Twark_Main, 2022-12-22.
• OLTARIS: 20 g/cm² LH₂ + 1 cm Al gives ~190 mSv/yr at 1 AU. For comparison, Mars surface >125 and a lava tube >22 LMT, 2023-06-07.
• 1 mSv/yr in deep space needs >10 m of water LMT, 2024-03-19.
• Van Allen "safe zone" at 2–4 Earth radii, with low-Z shielding against beta bremsstrahlung gbaikie, 2014-02-18.

Units

• Sv weighting factors: photons, electrons and muons 1; protons 2; alpha and heavy ions 20; neutrons energy-dependent Roy_H, 2022-12-17. Gray vs Sievert Robotbeat, 2022-12-17.

Dose limits and risk tolerance (unresolved)

• Standards cited:
• Radiation-worker limit 20 mSv/yr; aircrew typically <10 mSv. TommiR proposed designing for ≤10 mSv/yr TommiR, 2018-10-03.
• NASA career limit 600 mSv; ICRP 20 mSv/yr (≤50 in any year) LMT, 2023-05-24.
• Earth background 2.4 mSv/yr; pregnancy limit 1 mSv/yr Twark_Main, 2024-03-19; LMT, 2024-03-18.
• There is no global radiation standard Coastal Ron, 2024-03-12.
• The Ramsar argument.
• Ramsar, Iran has up to 260 mSv/yr background with no cytogenetic differences KelvinZero, 2022-11-02.
• Twark_Main: 8 t/m² (Earth-atmosphere equivalent) is excessive, so target a Ramsar-like dose. <20 mSv/yr is unnecessary, and 30 cm PE blocks cut shielding ~30× Twark_Main, 2022-12-04; Twark_Main, 2023-04-29.
• Counterarguments:
  • Ramsar's population is <2000; 260 mSv/yr arises only by combining spring water and radon; the mean is 6–10 mSv/yr; smoking confounds mikelepage, 2023-05-24.
  • Ramsar's maximum is 132 mSv/yr, below 400 LMT, 2024-03-18.
  • Acute solar-storm doses are a different matter lamontagne, 2022-11-02.
• Risk arithmetic.
• NASA uses ~5% risk per 1000 mSv; 100 mSv acute may add ~0.8% cancer risk mikelepage, 2023-05-24.
• mikelepage: 600 mSv ≈ +3% lifetime cancer on a 40% baseline. For an "epochal migration" one might accept 2000–4000 mSv lifetime, ≤200 mSv/yr, a 10–20 year deep-space career, then retirement in EVLEO mikelepage, 2023-05-25.
• Residents also receive dose outside the habitat (passageways, ships, EVA, medical), which argues for more habitat shielding Paul451, 2023-05-03.
• Design responses.
• Twark_Main: prove 20 vs 50/100/200 mSv; repair robots are cheaper than over-shielding; rotate crews every 3–5 years Twark_Main, 2023-05-06.
• Superpowers will drop the 600 mSv limit if it blocks them Twark_Main, 2024-03-12.
• Coastal Ron: first-generation stations are workplaces, and radiation tolerance belongs in the dedicated radiation thread Coastal Ron, 2024-03-18.
• "100% protection is never optimum"; wear garments for solar events Vultur, 2026-08-14. The AstroRad vest worked on Artemis I Coastal Ron, 2026-08-14.

Open questions

• Is the acceptable long-term dose 20, 50, 100 or 200 mSv/yr? The thread never agreed, and the answer changes station mass by an order of magnitude.
• Does partial gravity modify radiation susceptibility (combined-stressor effects)?

Related pages

• Radiation shielding · Location and orbits · Zero-g health effects

Sources

Forum posts

• gbaikie, 2014-02-18 (reply #73): Van Allen safe zone. Post.
• daveklingler, 2015-02-23 (reply #388, 1 like): Globus: equatorial LEO needs no shielding (1 like). Post.
• LMT, 2018-07-05 (reply #882): 400→250 km: −90% MMOD, −50% dose. Post.
• LMT, 2018-07-08 (reply #898, 1 like): Globus & Strout 2015 Table 6. Post.
• TommiR, 2018-10-03 (reply #1227, 1 like): 20 mSv/a worker limit; design ≤10. Post.
• mikelepage, 2018-11-01 (reply #1251, 2 likes): ELEO ~600 km: <40 mSv/yr. Post. Attachments: NASA Debris Orbit decay figure 1995.png.
• Coastal Ron, 2019-05-10 (reply #1623): LEO stations more mass efficient. Post.
• mikelepage, 2019-09-04 (reply #1664, 3 likes): SSO high radiation. Post.
• lamontagne, 2022-11-01 (reply #2300): 22 cm PE ~300 mSv/yr. Post. Attachments: solid_black_line_is_the_one_to_look_at.jpeg.
• KelvinZero, 2022-11-02 (reply #2303, 1 like): Ramsar 260 mSv/yr. Post.
• lamontagne, 2022-11-02 (reply #2305): Acute storm dose differs. Post.
• Twark_Main, 2022-11-08 (reply #2324, 1 like): Earth blocks half the sky. Post.
• mikelepage, 2022-11-29 (reply #2495): Dose vs altitude/inclination tables (4 likes). Post.
• Twark_Main, 2022-12-04 (reply #2531): 8 t/m² excessive. Post.
• Roy_H, 2022-12-17 (reply #2662): Sv weighting factors. Post.
• Robotbeat, 2022-12-17 (reply #2663, 1 like): Deep space GCR ~2× LEO. Post.
• Twark_Main, 2022-12-18 (reply #2665, 1 like): EML-1 critique. Post.
• Twark_Main, 2022-12-22 (reply #2686): 10 g/cm² Al ~750 mSv/yr. Post. Attachments: aluminum__radiation_shield_thickness.jpg.
• LMT, 2023-01-07 (reply #2803): Little shielding in EVLEO. Post. Attachments: Kalpana-24_Ba2-1920.jpg.
• Twark_Main, 2023-04-29 (reply #3654): 30 cm PE ~30× less shielding. Post.
• Paul451, 2023-05-03 (reply #3663): Dose outside habitat. Post.
• Twark_Main, 2023-05-06 (reply #3667): Rotate crews; prove limits. Post.
• mikelepage, 2023-05-24 (reply #3745): Ramsar caveats. Post.
• LMT, 2023-05-24 (reply #3746): No shielding in EVLEO. Post. Attachments: Simonsen et al. 2020 Fig3a.png.
• mikelepage, 2023-05-25 (reply #3747): Risk tolerance for migration. Post. Attachments: delay-adjusted-rates-per-persons.jpeg.
• LMT, 2023-06-07 (reply #3795): OLTARIS ~190 mSv/yr. Post.
• Coastal Ron, 2024-03-12 (reply #4545): No global standard. Post.
• Twark_Main, 2024-03-12 (reply #4549): Limits will change. Post.
• LMT, 2024-03-16 (reply #4566): Globus: L5 unrealistic. Post. Attachments: The High Frontier - An Easier Way.png.
• LMT, 2024-03-18 (reply #4570): 30 cm → ~400 mSv/yr = 20× ICRP. Post.
• LMT, 2024-03-18 (reply #4572): Ramsar max 132 mSv/yr. Post.
• Coastal Ron, 2024-03-18 (reply #4573): Belongs in radiation thread. Post.
• Twark_Main, 2024-03-19 (reply #4585): Background 2.4 mSv/yr. Post.
• LMT, 2024-03-19 (reply #4587): 1 mSv/yr needs >10 m water. Post.
• Coastal Ron, 2026-08-14 (reply #5074): AstroRad vest. Post.
• Vultur, 2026-08-14 (reply #5075): 100% protection not optimum. Post.
• Habitant, 2026-09-15 (reply #5111): ELEO 50× less shielding. Post.

External references

• Globus, A. & Strout, J. (2015). Orbital space settlement radiation shielding. NSS.
• Globus, A. et al. "Space Settlement: An Easier Way" (space.alglobus.net/papers/Easy.pdf); Marotta & Globus (2018) The High Frontier: An Easier Way.
• Benton & Benton (2001); Englert (2014); Kessler (1989): altitude effects on MMOD and dose.
• NASA OLTARIS radiation transport tool.
• Aliyu & Ramli (2015) Radiation Measurements 73; Eslami & Mortazavi (2019) JBPE 9(4): Ramsar studies.
• Seedhouse (2018), radiation effects chart.