Radiation shielding: passive and active

Key results

Passive shielding is the pressure vessel

• Paul451's design principle: "radiation shielding is not an add-on". At 1–5 m of hydrogen-rich or light material it is the pressure-vessel structure, so start the design with it Paul451, 2022-12-09.
• Shield first (e.g. 200 kg/m²), then size the hull lamontagne, 2026-09-15.
• 3–5 m of shield at 1 g is 6000–10,000 kg/m², which dominates the design and drives the choice between sun-facing (BIS) and perpendicular (Globus) orientation lamontagne, 2023-09-29.
• Geometry.
• Shielding scales with area and useful volume with volume, so minimize surface-to-volume: spheres and barbells, not tori Twark_Main, 2023-02-21; Paul451, 2023-06-05.
• Clump modules (7-module hex packing) Twark_Main, 2023-02-23.
• John's torus uses ~2.7× more thick shielding than a compact bola Twark_Main, 2024-07-05.
• A 2-sphere dumbbell needs ~3.5 Mt of shielding, half that of lamontagne's banded torus at equal volume mikelepage, 2023-03-06.
• Minimum torus (2 m minor radius, 4 rpm, 1 g) ≈ 3100 m³ vs minimum barbell 67 m³ Twark_Main, 2022-10-30.
• The shield mass factor ((r + t)²/r² − 1) favours a larger minor radius Twark_Main, 2023-09-30.
• Radiation pulls designs into compact "blobs" Twark_Main, 2022-11-16.
• Deep shielding for free. At the centre of a ~40 m radius habitat with 100–200 kg/m³ interior density, there is 4–8 t/m² of "free" shielding. Rooms deeper than 40 m inside a 0.2 t/m³ sphere get Ramsar-level dose anyway Twark_Main, 2022-11-26; Twark_Main, 2022-12-04.
• Stores as shielding.
• Surround the hab with supplies rearranged by a radiation-aware robot Twark_Main, 2024-08-16.
• Paul451: consumables become waste and total mass stays constant, so stores add shielding beyond the baseline Paul451, 2024-08-17.
• Shielding can come from life-support water LMT, 2022-12-23. JohnFornaro: shielding water must be pure and kept as a separate system JohnFornaro, 2023-10-12.
• Floor-only shielding is insufficient, because GCR arrives from all directions LarryCanuck, 2023-07-01.

Materials

• Hydrogen-rich materials are best.
• Polyethylene (RFX1) is 50% better than Al against SPE and 15% better against GCR Roy_H, 2014-03-01. Low average atomic mass is best Robotbeat, 2022-12-17.
• Thick PE is far better than thick Al or regolith Coastal Ron, 2022-12-18. See lamontagne's attached shielding.pdf lamontagne, 2018-08-06.
• Shevek23's correction (Bethe-Bloch with measured excitation potentials): per unit mass nearly all low-Z substances are similar for ionization Shevek23, 2019-10-26.
• LH₂ is best for large stations Robotbeat, 2023-05-18. Liquid methane for large structures (~8 m for 5 t/m²) Shevek23, 2019-10-25.
• Diminishing returns.
• 4 t/m² of PE gives only 18–20% lower dose than 1 t/m² (200 → 160 mSv/yr), so it is better to build 4× the stations Twark_Main, 2022-12-20.
• Practical SPE/GCR shielding is ~0.2–0.3 t/m² (20–30 g/cm²); returns vanish beyond that Twark_Main, 2022-10-30.
• OLTARIS by atomic mass: Fe-56 is a big contributor unshielded; 5 g/cm² LiBH₄ shifts dose to secondary protons; for 50 cm PE in LEO, dose rises beyond 30 cm under new pion/muon models Lampyridae, 2023-06-09.
• A "surrounded" architecture cuts GCR dose only ~10% (Bailey 2012) LMT, 2023-05-04.
• Water vs PE. Water is re-arrangeable but leaks; PE is lighter and can be structural or act as a Whipple shield Twark_Main, 2022-12-24.
• Operators prefer life-compatible materials (consider the consequences of a hole in LH₂ vs H₂O vs PE) Barley, 2023-05-26.
• HDPE water tanks in a double-wall annulus LarryCanuck, 2023-01-14.
• Aquaculture as permanent shield and refuge Coastal Ron, 2023-06-05.
• Numbers.
• OLTARIS: a 20 g/cm² C-C hull plus 40 g/cm² water cuts proton flux >90%. One 150 t ITS water payload shields ~380 m² at 40 cm LMT, 2018-07-08.
• A 1 km station at 5 m and 1600 kg/m³ needs ~6 Mt lamontagne, 2022-11-27.
• Kalpana One: 4.5–10 t/m² for an Earth-like dose Shevek23, 2019-10-25.
• 97% of Janhunen's L5 facility mass is shielding at population 200, but that is near worst case LMT, 2023-04-27; Twark_Main, 2023-04-29.
• Janhunen: adding 2% water and B-10 cuts shielding ~10%; Z-graded shielding puts metal outside LMT, 2024-03-18; LMT, 2023-09-20.
• Graded-Z: bolts outside Twark_Main, 2024-08-16.

Non-rotating shields

• A non-rotating shell around a rotating habitat needs only light support in 0 g TrevorMonty, 2018-11-01. See non-rotating hubs for bearing issues.
• Roy_H: a non-rotating 20 g/cm² PE shield around a 460 m torus is ~6000 m², ~1200 t Roy_H, 2022-11-01. Twark_Main: often a bad trade; equivalent spheres need only 192 t Twark_Main, 2022-11-08.
• Ashworth (JBIS 2020): a double torus inside an unpressurized spherical shield is the cheapest protected volume lamontagne, 2023-03-01.
• mikelepage's asteroid-pit bola: a bola rotating inside a pit dug into an asteroid blocks ~70–85% of GCR mikelepage, 2023-09-15.

Active shielding

• Concepts.
• Dartmouth toroidal superconducting shield (~10⁸ A to deflect 1 GeV GCR); NTRS 19890006394 double-torus shield mikelepage, 2015-10-09; mikelepage, 2023-05-17.
• ISU Starport 1: a 100 MW superconducting shield LMT, 2023-01-09.
• CREW HaT, a 10 T Halbach torus LMT, 2023-05-16. Slough 2022 LMT, 2023-05-18.
• Charged dielectric capacitors (Mechmann 2022) LMT, 2023-01-11. NASA electrostatic experiments Twark_Main, 2024-03-11.
• Mass comparison. For a 12 m sphere-equivalent torus, 20 g/cm² of LH₂ ≈ 362 t against YBCO cabling ≈ 65 t, so the torus suits active shielding mikelepage, 2023-06-05; mikelepage, 2023-06-01.
• Problems.
• A superconducting loop feels kN·m torque in the geomagnetic field; counter it with electrodynamic booms LMT, 2023-01-09; Hanelyp, 2015-11-16.
• CREW HaT makes things worse above ~1 GeV/n (secondaries) Robotbeat, 2023-05-18; Twark_Main, 2023-05-18.
• An electrostatic shield blocks ~50% of SPE but only ~15% of GCR Twark_Main, 2024-03-13. A passive bumper plus an active shield has no synergy Twark_Main, 2024-03-13.
• Verdict: a BIS contact with a magnetic-shielding author said the power is too high for a large habitat. mikelepage concluded the torus's advantage fades and passive shielding must come from asteroids lamontagne, 2023-09-14; mikelepage, 2023-09-15.
• Coastal Ron: reserve space for future electrostatic shields; use a superconducting refuge for storms Coastal Ron, 2024-03-12; Coastal Ron, 2024-03-13.

Storm shelters

• Water walls around a central corridor mikelepage, 2019-04-08. The tourist station needs a storm shelter KelvinZero, 2022-11-01.

Open questions

• Is 30 cm of PE "economical" or reckless? See dose limits.
• Will active shielding ever beat passive shielding at station scale?

Related pages

• Radiation environment and limits · Materials · Cylinders and spheres · ISRU

Sources

Forum posts

• Roy_H, 2014-03-01 (reply #144): RFX1 vs Al. Post.
• mikelepage, 2015-10-09 (reply #692): Dartmouth ToMaSS. Post.
• Hanelyp, 2015-11-16 (reply #779): Magnetic torque. Post.
• LMT, 2018-07-08 (reply #898, 1 like): OLTARIS water numbers. Post.
• lamontagne, 2018-08-06 (reply #1163): Shielding.pdf; H content key. Post. Attachments: shielding.pdf.
• TrevorMonty, 2018-11-01 (reply #1252, 2 likes): Non-rotating outer shell. Post.
• mikelepage, 2019-04-08 (reply #1505, 1 like): Water walls storm shelter. Post. Attachments: Pods_closed.png, Pods_ajar.png, Pods_open.png, Pods_turning.png.
• Shevek23, 2019-10-25 (reply #1679): Methane ~8 m for 5 t/m². Post.
• Shevek23, 2019-10-26 (reply #1694): Bethe-Bloch correction. Post.
• Twark_Main, 2022-10-30 (reply #2257): 20–30 g/cm² practical. Post. Attachments: solid_black_line_is_the_one_to_look_at.jpeg.
• Twark_Main, 2022-10-30 (reply #2258): Torus can't be shrunk. Post.
• KelvinZero, 2022-11-01 (reply #2295, 2 likes): Tourist station storm shelter. Post.
• Roy_H, 2022-11-01 (reply #2299, 1 like): 460 m torus shield ~1200 t. Post.
• Twark_Main, 2022-11-08 (reply #2323): Non-rotating shield bad trade. Post.
• Twark_Main, 2022-11-16 (reply #2395): Radiation → blobs. Post.
• Twark_Main, 2022-11-26 (reply #2454): Free deep shielding. Post.
• lamontagne, 2022-11-27 (reply #2464, 1 like): 1 km station ~6 Mt shielding. Post. Attachments: DeltaV map.png, Station (2).xlsx.
• Twark_Main, 2022-12-04 (reply #2537): Deep rooms. Post.
• Paul451, 2022-12-09 (reply #2621, 3 likes): Shielding is the structure (3 likes). Post.
• Robotbeat, 2022-12-17 (reply #2663, 1 like): Low atomic mass best. Post.
• Coastal Ron, 2022-12-18 (reply #2671): PE ≫ Al, regolith. Post.
• Twark_Main, 2022-12-20 (reply #2678): Diminishing returns. Post.
• LMT, 2022-12-23 (reply #2702): Life-support water shield. Post.
• Twark_Main, 2022-12-24 (reply #2707): Water vs PE. Post.
• LMT, 2023-01-09 (reply #2829): Starport 1 shield. Post. Attachments: Starport1.png, Starport_1_Final_Report_Fig4-15.png.
• LMT, 2023-01-11 (reply #2870): Mechmann 2022. Post. Attachments: Mechmann_2022_Fig12.png.
• LarryCanuck, 2023-01-14 (reply #2895): HDPE water annulus. Post.
• Twark_Main, 2023-02-21 (reply #3381): Minimize area/volume → sphere. Post.
• Twark_Main, 2023-02-23 (reply #3398): Hex clumping. Post.
• lamontagne, 2023-03-01 (reply #3446): Ashworth double torus in sphere. Post. Attachments: sphere.PNG.
• mikelepage, 2023-03-06 (reply #3494): Dumbbell half the shielding. Post.
• LMT, 2023-04-27 (reply #3650): 97% shielding. Post.
• Twark_Main, 2023-04-29 (reply #3651): Correction: 8× improvement at pop 10⁵. Post.
• LMT, 2023-05-04 (reply #3664): Bailey 2012. Post. Attachments: Bailey_2012_pg31.png.
• LMT, 2023-05-16 (reply #3720): CREW HaT. Post. Attachments: Desiata et al. 2022 Fig7.png, Desiata et al. 2022 Fig9.png, Kozhukhov and Osikova 2022 Fig5.png.
• mikelepage, 2023-05-17 (reply #3727, 1 like): Dartmouth JSR09. Post.
• LMT, 2023-05-18 (reply #3735): Slough 2022. Post. Attachments: Slough 2022 Fig4.png, Slough 2022 Fig9.png.
• Robotbeat, 2023-05-18 (reply #3736, 1 like): LH₂ best (1 like). Post.
• Twark_Main, 2023-05-18 (reply #3738): Active helps only low energy. Post.
• Barley, 2023-05-26 (reply #3751): Life-compatible materials. Post.
• mikelepage, 2023-06-01 (reply #3763, 1 like): Torus vs sphere area. Post. Attachments: Torus vs Sphere Major Radii.png, Torus vs Sphere Surface Area Ratio.png.
• Paul451, 2023-06-05 (reply #3784, 3 likes): Cluster modules to share outer walls (3 likes). Post. Attachments: Modules as dumbbell.jpg.
• mikelepage, 2023-06-05 (reply #3786, 1 like): Passive vs YBCO mass (1 like). Post. Attachments: Slough Fig 11.png.
• Coastal Ron, 2023-06-05 (reply #3790, 1 like): Aquaculture shield. Post.
• Lampyridae, 2023-06-09 (reply #3816, 1 like): OLTARIS details (1 like). Post. Attachments: dose percentage by atomic mass.jpeg, dose percentage by atomic mass - 5g per cm2.jpeg.
• LarryCanuck, 2023-07-01 (reply #3901, 2 likes): GCR from all directions (2 likes). Post.
• lamontagne, 2023-09-14 (reply #3935, 1 like): Power too high (1 like). Post.
• mikelepage, 2023-09-15 (reply #3943): Asteroid pit bola. Post.
• LMT, 2023-09-20 (reply #3994): Z-graded. Post. Attachments: Janhunen_2020_table1.png, Janhunen_2020_table3.png.
• lamontagne, 2023-09-29 (reply #4084): 3–5 m shield dominates. Post.
• Twark_Main, 2023-09-30 (reply #4085): Shield mass factor. Post.
• JohnFornaro, 2023-10-12 (reply #4165): Shield water separate. Post.
• Twark_Main, 2024-03-11 (reply #4540): Ars: active shielding. Post.
• Coastal Ron, 2024-03-12 (reply #4545): Reserve space. Post.
• Twark_Main, 2024-03-13 (reply #4555): No synergy. Post. Attachments: The_Muse.png.
• Coastal Ron, 2024-03-13 (reply #4556): Superconducting storm refuge. Post.
• Twark_Main, 2024-03-13 (reply #4557): Electrostatic 50% SPE, 15% GCR. Post.
• LMT, 2024-03-18 (reply #4576): Janhunen additives. Post. Attachments: Janhunen 2020 Table1.png, Janhunen 2020 Table3.png.
• Twark_Main, 2024-07-05 (reply #4646): Torus 2.7× shielding vs bola. Post.
• Twark_Main, 2024-08-16 (reply #4747): Supplies as shield. Post.
• Paul451, 2024-08-17 (reply #4757): Stores add shielding. Post.
• lamontagne, 2026-09-15 (reply #5107, 3 likes): Shield first. Post. Attachments: Image51_002.jpg.

External references

• Dartmouth, "Toroidal superconducting magnetic shielding" (JSR09.pdf); NTRS 19890006394.
• Desiati & D'Onghia (2022). CREW HaT, arXiv 2209.13624.
• Slough (2022). Spacecraft-scale magnetospheric protection from GCR. IEEE Aerospace.
• Janhunen (2020). Shielded dumbbell L5 settlement, arXiv 2004.02241.
• Bailey (2012). NASA 1-year deep-space transit architecture.
• "Optimal Shielding Thickness for Galactic Cosmic Ray Environments" (ResearchGate 311914600).
• Ashworth, S. (2020). JBIS 73(10).