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Weather forecasting for a rocket launch: It’s much more difficult than you might think

Clouds pass over the SpaceX Falcon 9, with the Crew Dragon spacecraft on top of the rocket, as it sits on Launch Pad 39-A Wednesday, May 27, 2020, at Kennedy Space Center in Cape Canaveral, Fla. Two astronauts will fly on the SpaceX Demo-2 mission to the International Space Station scheduled for launch Wednesday. (AP Photo/David J. Phillip)
Clouds pass over the SpaceX Falcon 9, with the Crew Dragon spacecraft on top of the rocket, as it sits on Launch Pad 39-A Wednesday, May 27, 2020, at Kennedy Space Center in Cape Canaveral, Fla. Two astronauts will fly on the SpaceX Demo-2 mission to the International Space Station scheduled for launch Wednesday. (AP Photo/David J. Phillip) (Copyright 2020 The Associated Press. All rights reserved.)

Over the years, I've worked hard to educate you about our weather and how I forecast it.

For you, it’s usually a matter needing to know what time it will rain or snow, how much will fall, and what the temperature and wind will be. And most of the time, as long as I get that right, you have what you need.

But forecasting for rocket launches entails a lot more. A whole lot more. About twenty years ago, I had the privilege of visiting the 45th Weather Squadron (now called the 45th Space Wing) at Cape Canaveral, and talked to the Air Force meteorologists there responsible for forecasting rocket and space shuttle launches. The weather criteria that must be satisfied for a “go” to launch is insane, and is constantly updated.

Here’s is the current list of criteria, with special thanks to NASA Ambassador and Cisco Engineer, Tony Rice, who compiled this for me:

Wind

  • Do not launch if the sustained wind at the 162-foot level of the launch pad exceeds 30 mph. 
  • Do not launch through upper-level conditions containing wind shear that could lead to control problems for the launch vehicle. 

Lightning

  • Do not launch for 30 minutes after lightning is observed within 10 nautical miles of the launch pad or the flight path, unless specified conditions can be met. 
  • Do not launch within 10 nautical miles of an attached thunderstorm anvil cloud, unless temperature and time-associated distance criteria can be met. 
  • Do not launch within 10 nautical miles of a detached thunderstorm anvil cloud. Do not launch within 3 nautical miles of a thunderstorm debris cloud, unless specific time associated distance criteria can be met. 
  • Do not launch within 5 nautical miles of disturbed weather clouds that extend into freezing temperatures and contain moderate or greater precipitation, unless specific time-associated distance criteria can be met. 
  • Do not launch for 15 minutes if field mill instrument readings within five nautical miles of the launch pad exceed +/- 1,500 volts per meter, or +/- 1,000 volts per meter if specified criteria can be met.
  • Do not launch through a cloud layer greater than 4,500 feet thick that extends into freezing temperatures, unless other specific criteria can be met. Do not launch within 10 nautical miles of cumulus clouds with tops that extend into freezing temperatures, unless specific height-associated distance criteria can be met. 
  • Do not launch within 10 nautical miles of the edge of a thunderstorm that is producing lightning within 30 minutes after the last lightning is observed. Do not launch through cumulus clouds formed as the result of or directly attached to a smoke plume, unless time-associated criteria can be met. 

Downrange weather

  • Do not launch if downrange weather indicates a violation of limits at splashdown in case of Dragon launch escape. 
  • Do not launch if downrange weather shows a high probability of violating limits at splashdown in case of Dragon launch escape. 

Notice that the forecast is for much more than at and near the launch pad itself. Should there be an emergency after launch necessitating an abort and bailing out of the crew, then the weather at those designated return locations must also be acceptable. So the 45th Space Wing is also looking far out into the Atlantic and forecasting for splashdown locations.

So how do launch chances look today? Unfortunately, afternoon thunderstorms could once again cause problems. Obviously, where those storms fire up is key but, the way things look right now, coverage should be fairly widespread. If they cannot launch again today, then Sunday is the next opportunity and, fortunately, thunderstorm coverage appears to be lower.

So, whether today’s launch happens or not, think about the enormous pressure on those meteorologists down there at the Cape. And I thought *I* had pressure talking to Tony Michaels about thunderstorm chances on Ford Fireworks Day in Downtown Detroit!


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