77ºF

Weather for 2nd launch attempt today not looking much better

Rain and clouds a risk for crewed Demo-2 mission

Dragon capsule would land approximately 9–42 miles from shore and approximately 3 miles in the water. However, high winds would increase the currents and increase waves making recovery difficult.
Dragon capsule would land approximately 9–42 miles from shore and approximately 3 miles in the water. However, high winds would increase the currents and increase waves making recovery difficult. (NASA)

JACKSONVILLE, Fla. – The second attempt to launch Americans into space for the first time in nearly a decade on the SpaceX Falcon 9 rocket this afternoon does not look much more promising in terms of the forecast. Wednesday’s attempt was scrubbed about 17 minutes prior to the launch because there was precipitation in the flight path.

The rain that scrubbed Wednesday’s launch cleared the flight path 22 minutes after the launch time, but not soon enough for the narrow launch window SpaceX requires.

Saturday’s weather forecast for the intended launch time of 3:22 p.m. does not look any more promising than what we saw on Wednesday. The 45th Weather Squadron from Patrick Air Force Base forecasts the weather for the launch. At it’s latest weather briefing, the meteorologists placed a 50% chance on the weather scrubbing the second attempt to launch.

The primary weather concerns are flight through precipitation, and the anvil cloud rule and cumulus cloud rule.

Anvil cloud rule

Do not launch through an attached anvil cloud. If lightning occurs in the anvil or the associated main cloud, do not launch within 10 nautical miles for the first 30 minutes after lightning is observed, or within 5 nautical miles from 30 minutes to three hours after lightning is observed.

Do not launch if the flight path will carry the vehicle...

  • Through non-transparent parts of a detached anvil for the first three hours after the anvil detaches from the parent cloud, or the first four hours after the last lightning occurs in the detached anvil.
  • Within 10 nautical miles of non-transparent parts of a detached anvil for the first thirty minutes after the time of the last lightning in the parent or anvil cloud before detachment, or the detached anvil after its detachment.
  • Within 5 nautical miles of non-transparent parts of a detached anvil for the first three hours after the time of the last lightning in the parent or anvil cloud before detachment, or the detached anvil after detachment, unless there is a field mill within 5 nautical miles of the detached anvil reading less than 1,000 volts per meter for the last 15 minutes and a maximum radar returns from any part of the detached anvil within 5 nautical miles of the flight path have been less than 10 dBZ on radar (light rain) for 15 minutes.

Cumulus cloud rule

  • Do not launch through cumulus type clouds with tops higher than the 41 degrees F temperature level. Launch may occur through clouds with tops as cold as 23 degrees F if the cloud is not producing precipitation, there is a field mill within 2 nautical miles of the cloud, and this field mill and all field mills within 5 nautical miles of the flight path read between -100 volts per meter and +500 volts per meter for the past 15 minutes.
  • Do not launch through or within 5 nautical miles of the nearest edge of cumulus-type clouds with tops higher than the 14 degrees F level.
  • Do not launch through or within 10 nautical miles of the nearest edge of cumulus clouds with tops higher than the -4 degrees F level.

Beyond launch weather, scientists also monitor the wave heights in the Atlantic Ocean in case the astronauts need to abort mid-launch or mid-flight and splashdown in the ocean. Weather needs to accommodate a safe abort should something not go according to plan with the first manned American rocket from American soil since 2011.

Saturday’s launch from Complex 39A at NASA’s Kennedy Space Center will return human spaceflight to the United States while flying over a much larger swath of the Atlantic towards Ireland.

Water is the only place it could touch down. Land is not an option in case of a mission abort.

NASA has had a 98-99% launch success rate and NASA will look to minimize risk for astronauts Bob Behnken and Doug Hurley piloting the Dragon spacecraft.

Weather factors will play a large role in their safety, which is why NASA has a detailed checklist to reduce weather-related risks.

The last test abort flight of the Dragon space capsule in January required monitoring a smaller weather footprint.

Unlike January 19th, 2020 test abort flight that terminated a few hundred miles east of Cape Canaveral, this crewed launch will cover the entire Atlantic.
Unlike January 19th, 2020 test abort flight that terminated a few hundred miles east of Cape Canaveral, this crewed launch will cover the entire Atlantic. (NASA)

Meteorologists will be monitoring weather patterns and assessing a no-go call if conditions over the Atlantic and at downrange weather locations show a high probability of violating safety limits at splashdown zones.

These downrange weather areas include more than 50 locations along the ascent track from the eastern seaboard and across the North Atlantic. Waves will be a determining factor.

Saturday's wave heights forecast
Saturday's wave heights forecast

Weather at all these locations can’t violate any of the requirements for wind, waves, lightning and precipitation.

Falcon 9 also uses an onboard predictive simulation to estimate where it will land. Part of the simulation is an estimate of wind speeds in the vicinity of the booster landing zone.

SpaceX measures wind speed in the landing zone using weather balloons. Measurements are taken at various intervals before landing events and used to create the required profiles of expected wind conditions during the landing event.

If the launch can’t happen Saturday afternoon, the next opportunity would be 3 p.m. on Sunday. Thtlate-season forecast looks slightly better, with a 40% chance that weather would scrub the launch.


About the Authors: