Value chain · CLM-1233
In plain terms
The design's beam would be very intense at the receiver, about two thousand times stronger than sunlight, so the site would need a fenced zone a few hundred metres across. At the fence, the study says, the infrared light would be far below the eye-safety limit of the day. A passing jet would warm slightly, but a slow light aircraft might be harmed.
The claim as recorded
The Lockheed design puts a Gaussian beam with a peak of 284 W/cm2 (2.84 MW/m2) on its 31.5 m receiver and sets a 200 m radius protected zone (62 acres, doubled in one direction for a 60 degree zenith angle), where the flux falls to 1.2 x 10^-4 W/cm2 (1.2 W/m2). Against a corneal limit of 0.1 W/cm2 (1,000 W/m2) for a 10 s exposure at 10.6 um, cited to AF Manual 161-32, that boundary flux is about 1,000 times below the limit. The study calls 1.6 x 10^-4 W/cm2 at 10.6 um "more than safe for continuous corneal exposure". It estimates that an airliner crossing the central 60 m (average about 25 W/cm2) would absorb 1.7 J/cm2 and warm by 12.2 C, while slower light aircraft "may possibly be damaged". On cloud, it states that more than 90 per cent of the population of the 48 contiguous states live where it is cloudy less than 50 per cent of the time.
Evidence behind this: A contractor design study's own safety analysis, citing a US Air Force laser hazard manual; design estimates, not measurements.
Scope and limits
AN EXPOSURE LIMIT FOR 10.6 UM, A WAVELENGTH NO MODERN PROPOSAL USES, TAKEN FROM A 1970S MILITARY MANUAL; NOT THE CURRENT IEC 60825-1 OR ICNIRP LIMIT. The Figure 39 limit formula is garbled in the text layer and needs a render. The boundary flux is 1.2 x 10^-4 at p.29 but 1 x 10^-4 at p.94. The cloud sentence is a population statement read off a national map (Figure 36), not hours lost at a site, and no power-availability analysis was done.
What it assumes
That the 0.1 W/cm2 in the p.29 garble is W/cm2. P.94 states it as "0.1 W/cm" without the squared unit, and the figure axis reads "CORNEAL IRRADIANCE" with PEL in W/cm2.
Where it comes from
PDF p.29 [19], raw (mu written um): "The beam intensity on the receiver is Gaussian with a peak intensity at the center of 284 W/cm2 with an intensity of 1.2 x 10-4 W/cm2 at 200-m radius"; "This ellipse contains 251, 327 m2 (62 acres) which will provide a safety factor 1000 times less than the cur- rent sa!ety standard (0. 1 WI cm ) for corneal exposure to 10. 6-um. laser radiation." PDF p.94 [84], raw: "At 10. 6-u.m. wavelength, the eye is far less sensitive as illustrated in Figure 39 where 0.1 W/cm is permissible for a 10-s exposure. This indicates that at 10.6-um wavelengths an intensity of 1. 6 x 10-4 WIcm2 is more than safe for continuous corneal exposure." PDF p.96, figure caption and source line, raw: "Figure 39;. Permissible exposure level (10. 6 u.m)"; "*AF MANUAL 161-32, LASEif HEALTH HAZARDS CONTROL". PDF p.99 [89], raw: "There is a total of about 700 MW of power being deposited over this area for an average flux density of about 25 W/cm2"; "AT = (l) ( 2 .~a; (0.0 5 ) = 12.2[deg]c (22[deg]F)"; "smaller light aircraft flying slower may possibly be damaged". PDF p.78 [68], raw: "probably more than 90% of the population of the 48 continental United States live in areas that are cloudy less than 50% of the time". Conversions: 284 W/cm2 = 2,840,000 W/m2; 0.1 W/cm2 = 1,000 W/m2; 1.2 x 10^-4 W/cm2 = 1.2 W/m2; 0.1 / 1.2 x 10^-4 = 833, which the page rounds to "1000".
Basis: W/cm2 (converted to W/m2) at the receiver and the protection boundary; exposure time in s; land area in acres; temperature rise in C
Related records
- Answers question
- QST-023 not published in this releaseQST-036 not published in this release
Cite this
energyaperture.com/c/clm-1233
CLM-1233, Energy Aperture, as of 1978-09.
Connected records
Other published records linked to this one. A list, not a judgement.