Seeding Cold Fog with Pyrotechnics.

In January 1969 a test team seeded supercooled -7.5 to -13C fog and stratus in nine Project Cold Cowl experiments at Elmendorf AFB, Alaska. The team used 2-minute TB-2 pyrotechnic fusees mounted on a WC-130 aircraft flying box and lane patterns at cloud-top level or up to 500 feet above it at about 130 knots. The slow speed was chosen for test convenience the TB-2 would be equally effective at speeds to about 260 knots. The optimum seeding method was to fly parallel straight lanes at 3,000-foot intervals at cloud-top level, using one fusee per lane. The holes thus made merged into one. The major problem was proper positioning of the hole, partly because the hole-making reaction time is 30 to 50 minutes. The fusees were effective and convenient to use effectiveness decreased with increased altitude above the cloud top. Crushed dry ice was dispensed in similar flight patterns for comparison. Author