 The space shuttle Discovery backlit with lightning near Launch Pad 39A at NASA’s Kennedy Space Center in Cape Canaveral, FL on August 4, 2009. When the big day of the launch finally arrives, the equipment is thoroughly checked, astronauts have spent months in training, and the flight path has been cleared of traffic. But, there’s one thing the flight crew can’t control- the weather. Ultimately, calm winds and clear skies provide the best flight conditions, but that isn’t always the case, as we saw with the SpaceX Dragon Launch in 2020… While equipment can range in the millions of dollars range, it is best to err on the side of caution of making it to space safely. However, delays due to weather can require other accommodations for perishable food or live animals on board. The Air Force 45th Weather Squadron usually provides weather forecasts for launches in the Cape Canaveral area, where most launches occur. NASA has 14 different launch criteria pertaining to weather pertaining to wind, cloud cover, visibility, and the majority because of lightning. Violation of any of these conditions will cause the launch to be rescheduled for another day. Conditions must also be clear down range, in case of an emergency launch abort after liftoff and for a splashdown to occur. See photo below to check out all 14 different weather conditions monitored by flight meteorologists:  Thunderstorms can be the main hazard for rocket launches, particularly at Cape Canaveral, where daily afternoon thunderstorms are common. Rockets on the launch pad are safe from strikes due to lightning rods, but can be susceptible to a hit after they are launched. If a thunderstorm has produced lightning in the past 30 minutes within ten nautical miles of the launch site, it’s a no-go for the flight. A lightning strike almost spelled the end of the Apollo 12 mission in 1969 even before it left the Earth’s atmosphere. Seconds after lift off, the moon-bound rocket was struck by lightning, causing warning lights to go off and the astronauts lose their altitude reference. Luckily, the crew was able to get systems back online and made it to the moon safely. The lightning strike could’ve spelled disaster otherwise. In 1987, the unmanned Atlas/Centaur-67 rocket was launched into rainy, overcast skies, being struck by lightning and sending it “tumbling out of control”. Scientists have learned that exhaust plumes from the rocket can also trigger lightning when passing through a preexisting electric field, such as tall cumulus clouds containing both water and ice. Any form of precipitation could cause a launch to be scrubbed (snow or any type of frozen precipitation is generally rare along the Florida coast). Even a thick layer of clouds may postpone a launch, especially if the cloud layer is greater than 4500 feet thick and extends into the freezing layer, endangering the rocket’s safety. Even on a clear day, wind can still cause a launch to be postponed. If winds are light near the launch site, but exceed 30 mph near the 162-ft level of the launch tower, this criteria will be a violation of the launch procedure. High winds can cause possible control problems for the rocket and cause it to veer off course. If wind observations near the launch pad exceed 34 mph (or 30 knots), the launch will be scrubbed. Determining upper-level winds is a little different, as wind shear (change of wind speed with altitude) is analyzed, not necessarily the speed of the wind. Best to wait for winds to die down. A launch planned for early March 2020 for SpaceX was scrubbed due to high wind shear. SpaceX had planned a launch again on May 27, 2020, but was called off about 17 minutes before liftoff due to the presence of lightning, “lightning energy dissipation”, and an attached thunderstorm anvil (a towering thunderstorm top that can generate an electric field and trigger lightning when in contact with a rocket’s plume) in the vicinity of Kennedy Space Center. The thunderstorms were a result of remnants from Tropical Storm Bertha, which made landfall in South Carolina that morning. Clearing was indicated after the specific launch window. A second launch attempt was made for May 30th, with the forecast calling for lingering cloud cover left in the storm’s wake. The launch was successful. Even after a successful launch, the weather must cooperate for a landing. Landing a rocket with extreme precision in a small target in the ocean is complicated enough without adding factors such as wind, swells, or rain. To learn more about rockets and other space weather topics, please click here: https://www.globalweatherclimatecenter.com/space-weather-topics. ©2021 Meteorologist Sharon Sullivan References:
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