Value chain · CLM-1160
In plain terms
A 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 geostationary base needs a storm shelter with the shielding of about 15 cm of aluminium, plus goggles and lead underwear so the shelter can be lighter; and a geomagnetic storm can make the electron belt a hundred times more intense in hours.
The claim as recorded
For an SPS crew in GEO, where "The geomagnetic field in GEO is too weak to afford shielding against energetic particles from solar flares", the 1978 LBL evaluation took the August 1972 event as the design case: "about 40 g/cm2 aluminum is needed to reduce the proton skin dose equivalent to 25 rem" (or "about 30 g/cm2 tissue"), a suited worker at 0.2 g/cm2 would reach the 30-day skin limit in about three hours ("Skin (hr) 3.0 3.5 4.7 8.0" at 0.2, 0.4, 1 and 5 g/cm2, "Lens (hr) 1.9 2.4 3.6 6.5 11.7"), so that "A heavily-shielded shelter is necessary to protect personnel from large solar particle events such as those of August 1972", its weight held down by self-shielding and by "goggles to protect the eye lens and lead undergarments to protect the testes and ovaries"; separately, storm-time trapped electrons in GEO "increase by more than two orders of magnitude in a few hours" and at peak "exposures in excess of allowable limits can be accumulated in about 30 minutes or less".
Evidence behind this: T3-the synthesis paper's restatement of two cited flare-dose calculations (Rossi and Stauber 1977; Wilson and Denn 1976) for the August 1972 event, with its own operational conclusions.
Scope and limits
A DESIGN-CASE CALCULATION FOR ONE HISTORICAL FLARE, cited from two model papers, with no shelter mass, no warning-system design and no probability of occurrence per 90-day tour stated. The 30-minute electron-storm figure has no dose attached in the text.
What it assumes
The August 1972 event as the design flare and the King 1973 spectrum; the 1970 NAS 30-day limits of CLM-1161 as the limits reached.
Where it comes from
PDF 237 / printed 235: "The geomagnetic field in GEO is too weak to afford shielding against energetic particles from solar flares" (normalised); "This calculation indicates that about 40 g/cm2 aluminum is needed to reduce the proton skin dose equivalent to 25 rem" (normalised). PDF 242 / printed 240: "about 30 g/cm2 tissue attenuates the dose-equivalent to 25 rem at the center of the tissue sphere" (normalised). PDF 243 / printed 241, Table 4 (layer): "Skin (hr) 3.0 3.5 4.7 8.0" and "Lens (hr) 1.9 2.4 3.6 6.5 11.7" for 0.2, 0.4, 1, 5 and 10 g/cm2 of tissue; behind 13.7 g/cm2 aluminium "the additional self-shielding is enough to keep the dose" (raw) equivalent "below the 25-rem limit for the marrow and the 75-rem limit for the skin; however, the 37-rem limit for the eye lens and the 13- rem limit for the testes are reached in about 12 and 13 hours, respectively" (normalised). PDF 252 / printed 250: "the results of Table 4 indicate that dose-equivalent limit to the skin would be reached in about three hours" (normalised). PDF 253 / printed 251: "trapped electron intensities in GEO during intense magnetic storms increase by more than two orders of magnitude in a few hours followed by decay with mean lifetime of several days. When the peak intensity is reached, exposures in excess of allowable limits can be accumulated in about 30 minutes or less" (normalised). PDF 257 / printed 255: "A heavily-shielded shelter is necessary to protect personnel from large solar particle events such as those of August 1972" (normalised); "to use personal shielding such as goggles to protect the eye lens and lead undergarments to protect the testes and ovaries" (normalised). PDF 4 / printed 2: "Geostationary personnel must be warned in time to reach adequately shielded shelters in order to avoid lethal exposures from the large solar particle fluxes which often accompany such solar storms" (normalised). Recomputed: 40 g/cm2 / 2.70 g/cm3 = 14.8 cm of aluminium; 30 g/cm2 of tissue is 30 cm of water-equivalent.
Basis: g/cm2 of aluminium or tissue; rem dose-equivalent; hours from flare onset
Cite this
energyaperture.com/c/clm-1160
CLM-1160, 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-1159A 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...CLM-1161The 1978 plan assumed space workers would be allowed about ten times the radiation dose an ordinary radiation worker may take, under 1970...