Lighting, windows and views

Key results

How much light

  • Sunlight equivalent (Paul451): a clear day is ~1000 W/m² (1370 in orbit), overcast 200–400, sky glow >100 W/m². Mimicking sunlight needs ~1 kW/m² (≈ 90 W/ft²; 9 kW for a 10 × 10 ft office) regardless of lamp type Paul451, 2023-10-20.
  • Even 100 W/m² daylight LEDs give about half a heavy-cloud winter day and <1/10 of summer sun Paul451, 2023-10-18.
  • LEDs are ~90% efficient, so the energy comparison is W/m² against W/m². Future improvements will be only in form factor and cost Paul451, 2023-10-20.
  • Indoor light is ~1/500–1/1000 of sunlight. A 1 m skylight from a sunlit deck gives "office lighting" for ~500 m² below, which changes the design language Paul451, 2023-10-20.
  • Where light is needed. Only some areas need sun-equivalent light: walkways, social spaces, exercise. Coastal Ron uses 100% electric lighting Coastal Ron, 2023-10-20.
  • lamontagne: follow building-code lighting in work and living areas; provide large high-illumination "outdoor" areas (wide bright circulation, cafés, parks with seasonal variation) and very bright grow rooms lamontagne, 2023-10-20.
  • Strong daylight matters for children's eyesight and mood lamontagne, 2023-10-18.
  • Night on 24-hour stations. Daylight-level areas leak light into sleeping areas, so light sections in turns and block leakage Paul451, 2023-10-20. Tilting mirrors create morning, noon and night JohnFornaro, 2023-10-21.

Natural light vs LEDs

  • Paul451's comparison: PV at 20–30% needs 3–5 m² of panel per m² of lit floor, whereas mirrors or windows need ~2/3 of floor area. Selective mirrors can reflect visible light only, with a diffuser for sky glow Paul451, 2023-10-18. Filter UV and spectrum Barley, 2023-10-18.
  • Twark_Main's optics.
  • Window optimum for a habitat sphere: a ~75° cone. Windows covering 37% of the surface intercept 93% of sunlight; with an annular mirror, 25% of the hull captures 90–100% Twark_Main, 2023-10-14.
  • In a cost-optimized layout only 3–10% of interior volume is exposed to exterior lighting Twark_Main, 2023-10-16.
  • The natural-light question drives top-level design (geometry, shielding, spin axis, stationkeeping, power/thermal), so decide it early Twark_Main, 2023-02-25.
  • A sun-tracking spin axis removes moving shadows. Alternatively, put the axis perpendicular to the ecliptic with a conical 45° mirror Twark_Main, 2023-02-25; Twark_Main, 2023-02-11.
  • Coastal Ron's position: moving light is distracting; use light pipes, fibre and LEDs that mimic spectra. People live without sunlight (submarines, polar stations, a 40-day cave study). "The best part is no part" Coastal Ron, 2023-02-25; Coastal Ron, 2023-10-18.
  • Light pipes of fibre bundles through skylights, with mirrors outside JohnFornaro, 2023-10-18.
  • "Window poor." Huge windows and empty spaces make occupants "window poor" (>30% of fees) Twark_Main, 2023-03-06.

Windows and views in a rotating frame

Open questions

  • Is natural light a requirement for long-term residents, or a luxury? It is unresolved and determines the architecture.
  • How do rotating views affect motion sickness at 2–4 rpm?

Sources

Forum posts

  • high road, 2014-02-22 (reply #117): Screens with stationary view. Post.
  • lamontagne, 2023-01-20 (reply #2995, 1 like): Mona Lisa analogy. Post.
  • Coastal Ron, 2023-01-20 (reply #2996): Stabilized cameras. Post.
  • Asteroza, 2023-01-20 (reply #2997, 1 like): Nadir hub cupola (1 like). Post.
  • LarryCanuck, 2023-01-20 (reply #2998, 1 like): CN Tower 1 rph. Post.
  • lamontagne, 2023-01-25 (reply #3082, 3 likes): View videos 1 vs 3 rpm (3 likes). Post.
  • Coastal Ron, 2023-01-25 (reply #3084): 148 km per rev. Post.
  • mikelepage, 2023-01-25 (reply #3087, 1 like): Centre cupola with cage (1 like). Post.
  • lamontagne, 2023-01-25 (reply #3095): CoR contested. Post.
  • lamontagne, 2023-01-25 (reply #3097, 1 like): 1 rpm calmer. Post.
  • Twark_Main, 2023-02-11 (reply #3284): 45° mirrors > sun-pointing. Post.
  • Twark_Main, 2023-02-25 (reply #3409): Axis ⟂ ecliptic + 45° mirror. Post.
  • Coastal Ron, 2023-02-25 (reply #3410): People live without sunlight. Post.
  • Twark_Main, 2023-02-25 (reply #3417): Natural light drives design. Post.
  • Twark_Main, 2023-02-27 (reply #3437): Dragon cupola acrylic. Post.
  • Twark_Main, 2023-03-06 (reply #3480): Window-poor. Post.
  • Twark_Main, 2023-10-14 (reply #4177): Window cone optimum. Post. Attachments: sphere_window_coverage_optimization.png.
  • Twark_Main, 2023-10-16 (reply #4179): De-rotated observation room. Post.
  • Twark_Main, 2023-10-16 (reply #4181): 3–10% exposed. Post.
  • Coastal Ron, 2023-10-18 (reply #4206): Light pipes/LEDs. Post.
  • lamontagne, 2023-10-18 (reply #4207, 2 likes): Daylight for eyesight/mood (2 likes). Post.
  • JohnFornaro, 2023-10-18 (reply #4210): Fibre light pipes. Post. Attachments: Ring-Station-Labeled.jpg, Ring-Spoke-Section-Labeled.jpg, Ring-Section-with-T-Rex-&-Skylite.jpg.
  • Barley, 2023-10-18 (reply #4213, 2 likes): Filter UV. Post.
  • Paul451, 2023-10-18 (reply #4215, 1 like): 100 W/m² LEDs ≈ cloudy winter. Post.
  • Paul451, 2023-10-20 (reply #4222): ~1 kW/m² for daylight. Post.
  • lamontagne, 2023-10-20 (reply #4225, 1 like): Building-code lighting; outdoor areas (1 like). Post.
  • Coastal Ron, 2023-10-20 (reply #4226): Only some areas; 100% electric. Post.
  • Paul451, 2023-10-20 (reply #4227): Skylights light 500 m². Post.
  • Paul451, 2023-10-20 (reply #4228): Light leakage; sections lit in turns. Post.
  • Paul451, 2023-10-20 (reply #4230): LEDs ~90%. Post.
  • JohnFornaro, 2023-10-21 (reply #4231): Tilting mirrors for day cycle. Post.

External references

  • marspedia.org/Lighting.
  • NTRS 20170001289 (ALON).