Value chain · CLM-1235
In plain terms
Studies from around 1980 used an infrared safety limit of about one-tenth of strong sunlight for long, whole-body exposure, and ten times that for brief exposure of small areas. Meeting it meant fencing off a zone a few hundred metres across around each receiver and keeping aircraft out of the beam.
The claim as recorded
The 1980 Rockwell study cites the ANSI exposure limit for continuous-wave infrared lasers as 100 mW/cm2 (1,000 W/m2), set for small spots and exposures over 10 s. For large-area, long exposure it adopts a lower limit recommended in the literature, 10 mW/cm2 (100 W/m2). With that limit and a margin for the worst plausible pointing accident (a slew of about 70 m), it sets a receptor protection radius of 300 to 800 m and total site land of 0.3 to 2 km2. The 1978 DOE assessment gives the same 10 mW/cm2 per 8-hour day for visible and infrared exposure, based on tissue heating. It says the body tolerates 0.1 W/cm2 (1,000 W/m2) for a short time, the eye is opaque beyond 1.7 um, and 1.5 W/cm2 (15,000 W/m2) is permitted for aircraft. Rockwell restricts all air traffic over the receptor zone, mainly for the eye hazard from stray reflections.
Evidence behind this: Two US agency-funded studies (1978, 1980) stating exposure limits they cite from ANSI and the literature; secondary statements of standards, not the standards themselves.
Scope and limits
1970S STANDARDS QUOTED SECOND-HAND, FOR MID- AND LONG-WAVE INFRARED (ABOUT 5 TO 10.6 UM); NOT THE CURRENT IEC 60825-1 OR ANSI Z136.1 VALUES, AND NOT FOR THE 0.8 TO 1.6 UM BAND MODERN PROPOSALS USE. Neither source gives the ANSI edition. SRC-509 names no standard for its 10 mW/cm2 or 1.5 W/cm2 figures (its footnoted references 49 and 50 are microwave limits). Rockwell's literature limit is a recommendation, not a standard.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF p.53 [3-9], raw: "The American National Standards Institute (ANSI) exposure limit for cw infrared lasers is 100 mW/cm 2 This limit was determined for relatively small spot sizes on the skin or eye based on durations in excess of 10 sec. For large-area, long-duration exposure, [ref. 77] recommend an average ocular or wholebody irradiance limited to about 10 mW/cm 2 ."; "If a maximum permissible exposure limit of 10 mW/cm 2 is adopted and if allow- ance for the maximum plausible accident is included, a protection radius of 300 to 800 m is appropriate."; "The total land areas required by the receptor site is estimated to be 0.3 to 2 km 2"; "all or part of the beam will slew away from the receptor by about 70 m before power-off conditions are achieved". PDF p.52 [3-8], raw: "The transmission air zone associated with all receptor sites must be restricted to all private, commercial, and military aircraft Of all types."; "The principal reason for restricting all air traffic is the occular hazard". SRC-509 PDF p.62 [50], raw (mu written u): "The eye is opaque to wavelengths longer than I. 7 u m, and the human body can tolerate added heat inputs of 0.1 W/cm 2 for a short time. An acceptable visible and infrared radiation exposure level is 10.0 mW /cm 2 per 8-hour day based on tissue heating."; "A radiation level as high as 1.5 W/cm 2 is permitted for aircraft." Conversions: 1 mW/cm2 = 10 W/m2, so 100 mW/cm2 = 1,000 W/m2 and 10 mW/cm2 = 100 W/m2; 1.5 W/cm2 = 15,000 W/m2.
Basis: W/m2 (from mW/cm2 and W/cm2) of infrared exposure; protection radius in m; land in km2
Related records
- Answers question
- QST-023 not published in this releaseQST-036 not published in this release
Cite this
energyaperture.com/c/clm-1235
CLM-1235, Energy Aperture, as of 1980-11.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-509
- CLM-1238In 1978 the US energy department asked whether lasers could replace the microwave beam. Its review said the lasers of the day were not good...
- Also from SRC-573
- CLM-1234A second NASA-funded study in 1980 imagined the standard power satellite with its microwave transmitters swapped for about twenty very...