Value chain · CLM-1159
In plain terms
A ninety-day shift in low orbit would give a worker about 20 rad, the trip up and back about 3, and ninety days at geostationary altitude 29 to 56 rad depending on where over the Earth the satellite sat, most of it from X-rays the trapped electrons make in the hull.
The claim as recorded
The 1978 LBL evaluation's preliminary doses for an SPS space worker behind 300 mils (2 g/cm2) of aluminium, in aluminium ("The dose in tissue is about 1.3 times that in aluminum"): in LEO "the 90- day mission dose ... is about 20 rads at solar minimum; the dose at solar maximum is about one-half", Table 3 giving trapped protons 0.2 and 0.1 rad/day and 18 and 9 rad per 90 days as the total, since "the trapped protons constitute the dominant radiation hazard in LEO"; for the LEO-GEO round trip at 5.25 hours each way "3 rad behind 2 g/cm2 aluminum and 0.2 rad behind 5 g/cm2 aluminum", though another transfer ellipse "might be higher or lower by perhaps as much as several orders of magnitude"; and in GEO, where trapped protons "are not energetic enough to penetrate even the thinnest spacesuit", Table 5 gives 0.60 rad/day and 56 rad per 90 days at the worst parking longitude (160 deg west: electrons 14, bremsstrahlung 40, galactic 1.8) and 0.30 and 29 rad at the best (70 deg west), bremsstrahlung dominating so that a tantalum or lead layer in the work-area walls could reduce it "significantly".
Evidence behind this: T3-preliminary model-based dose estimates (NSSDC AP-8 and AEI-7 environments, slab-shield transport) by a named author at a national laboratory workshop; the paper calls every figure preliminary.
Scope and limits
PRELIMINARY BY THE PAPER'S WORD, IN ALUMINIUM BEHIND A SLAB, NOT ORGAN DOSE; the transfer figure can move by orders of magnitude with the ellipse chosen; the GEO figure varies by a factor of two with parking longitude and the AEI-7 model was itself an interim revision upward. Galactic cosmic rays are in the table at 1.8 rad per tour but their HZE component is the "major uncertainty" of CLM-1161.
What it assumes
The AP-8 and AEI-7 environment models of 1976-78 and a 2-pi slab geometry; a 5.25-hour transfer.
Where it comes from
PDF 231 / printed 229: "The dose in tissue is about 1.3 times that in aluminum" (normalised); "the trapped protons constitute the dominant radiation hazard in LEO" (normalised). PDF 234 / printed 232, Table 3 (layer): "Trapped protons 0.2 0.1 18 9"; "TOTAL 0.2 0.1 18 9" (normalised); "the dose from galactic cosmic radiation is less than 0.5 rad at any time" (normalised). PDF 235 / printed 233: an unscheduled EVA gives "a skin dose of 0.3 rad behind a suit of thickness 0.2 g/cm2 aluminum-equivalent for a" (normalised) worst-case "single traversal through the heart of the SAA" (raw). PDF 236 / printed 234: "The absorbed dose for a round trip from LEO to GEO and back to LEO for the specified orbital-transfer ellipse is 3 rad behind 2 g/cm2 aluminum and 0.2 rad behind 5 g/cm2 aluminum" (normalised); "For a different orbital-transfer ellipse, the absorbed dose might be higher or lower by perhaps as much as several orders of magnitude" (normalised); "trapped protons do not present a radiation hazard to personnel because the protons are not energetic enough to penetrate even the thinnest spacesuit" (normalised). PDF 246 / printed 244, Table 5 (render read): "Trapped electrons 0.16 14", "Bremsstrahlung 0.44 40", galactic 0.02 and 1.8, "TOTAL 0.60 56" (worst, 160 deg W; normalised); best, 70 deg W: 0.026 and 2.37, 0.28 and 25, 0.02 and 1.8, 0.30 and 29 (render readings). PDF 255-256 / printed 253-254: "the 90- day mission dose behind 300 mils (~ 2 g/cm2) of aluminum is about 20 rads at solar minimum; the dose at solar maximum is about one-half that at solar minimum" (normalised); "is typically 3 rad behind 2 g/cm2 aluminum and 0.2 rad behind 5 g/cm2 aluminum" (normalised); "the 90-day mission dose behind 300 mils (= 2 g/cm2) of aluminum varies from about 29 rad for the best parking longitude of 70" (normalised) deg west "to about 56 rad for the worst parking longitude of 160" (normalised) deg west; "it is possible to reduce these doses significantly by designing the walls of the work areas with an additional layer of heavy metal, such as tantalum or lead, to attenuate the electron bremsstrahlung more effectively" (normalised). PDF 244 / printed 242: "Curtis (1976) estimated the absorbed dose rates from galactic cosmic rays at roughly 10 rad per year with 35% coming from particles with Z > 2, and 10% from particles with Z > 20" (normalised). Recomputed: Table 5 columns sum to 0.62 / 55.8 and 0.326 / 29.2 against the printed 0.60 / 56 and 0.30 / 29; 0.2 x 90 = 18; in tissue at 1.3 x, 23 (LEO), 38 and 73 (GEO) rad per tour.
Basis: rad absorbed in aluminium behind 2 g/cm2 (300 mil) aluminium, per day and per 90-day tour; tissue about 1.3 x aluminium
Cite this
energyaperture.com/c/clm-1159
CLM-1159, Energy Aperture, as of 1978-09.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-546
- CLM-1158The 1978 plan put seven hundred people in orbit at a time, on ninety-day tours of sixty-hour weeks, adding up to about 270,000 tours over...CLM-1160A big solar flare like August 1972 would push a spacesuited worker past the skin limit in three hours and the eye limit in two, so the...CLM-1161The 1978 plan assumed space workers would be allowed about ten times the radiation dose an ordinary radiation worker may take, under 1970...