Commercial Rocket Launch: Weather Worries?

Andy Cox, Jon Erdman Updated: May 21, 2012, 2:18 PM EDT

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Private rocket maker SpaceX is aiming for a Tuesday liftoff after fixing the engine problem that caused a launch abort over the weekend, stalling the world's first commercial space station supply flight.

(DETAILS:  SpaceX Launch Grounded)

Space Exploration Technologies - better known as SpaceX - still hopes to begin a new era in spaceflight as the first company to send a spacecraft to the International Space Station.  But Saturday's glitch forced a delay until the next launch window of 3:44 am Tuesday morning.

SpaceX is one of two companies working under a NASA program to develop private sector cargo transport capability, which will allow NASA to focus on exploration beyond low Earth orbit after ending the 30-year space shuttle program in 2011.

In this June 4, 2010 photo, the SpaceX Falcon 9 test rocket lifts off from complex 40 at the Cape Canaveral Air Force Station in Cape Canaveral, Fla.

AP Photo/John Raoux, File

If weather conditions cooperate and there are no other glitches, the nine main engines on SpaceX's Falcon 9 rocket will roar to life early Tuesday, and ten minutes later the Dragon spacecraft will be on a path to meet up with the International Space Station.

This would be the third flight of the Falcon 9 - named after the Millennium Falcon from the Star Wars movies - and the second demonstration flight of the Dragon spacecraft under the Commercial Orbital Transportation Services (COTS) program. If SpaceX meets all of the demonstration mission objectives, the company may begin operational cargo flights to the station later this year.

Falcon 9, like the space shuttle, must fight its way through Earth's dynamic atmosphere on the way into orbit. The unique shuttle's launch weather rules were somewhat more restrictive than most launch vehicles, especially because of its emergency landing requirements.

How launch weather rules compare to the Space Shuttle

  • Lightning:  All launches from Cape Canaveral are subject to the lightning launch commit criteria, a set of rules designed to protect against natural and artificially triggered lightning as the rocket flies near electrically charged clouds.  For example, launch is prohibited if lightning is observed within 10 nautical miles of the flight path in the previous 30 minutes.  
  • Wind:  Windy conditions can cause control problems, as anyone who's driven a car in windy conditions knows. Wind shear can also place excessive structural stress on launch vehicles. The details differ, but all launch vehicles have rules for wind at the launch pad and at higher altitudes. The space shuttle's rules covered not only winds along the normal launch flight path, but also at potential emergency landing sites. The Dragon has no such restriction - at least, not on this flight. Future Dragon launches may carry crew and will likely have additional weather rules for emergencies.
  • Precipitation:  The shuttle was not allowed to launch if there was rain anywhere along its flight path, and was also not allowed to fly through rain during landings. This meant the any time rain was anywhere near the launch pad or landing site, there was a good chance of violating at least one of the weather rules. The Falcon's rule is less restrictive; rather than prohibiting any flight through precipitation, there are different thresholds depending on the altitude and speed.

Tuesday's Forecast

Tuesday's Forecast

The Forecast

An early morning launch this time of year typically offers the best opportunity to avoid Florida's scattered afternoon thunderstorms in the "wet season".

(MORE:  Florida's Wet and Dry Seasons)

At this point, the forecast for the pre-dawn hours Tuesday looks quiet for Florida's Space Coast.  

In the absence of any showers and thunderstorms, forecasters with the U.S. Air Force 45th Weather Squadron, responsible for supporting all launches from Cape Canaveral, are most concerned about cumulus clouds.  Yes, rules also exist regarding clouds near the launch site or within the launch path.

The current forecast from the USAF 45th Weather Squadron is a 20 percent chance of weather violations, primarily for the cumulus cloud rule of the lightning launch commit criteria.

(MAP:  Interactive satellite loop

In the event of a no-go on Tuesday, there will be another window of opportunity on Wednesday.  

(MORE:  Cape Canaveral 5-day forecast)

The Weather Channel and will feature comprehensive coverage of the SpaceX demonstration mission, including weather coverage leading up to launch. You can also follow @twcspacewx on Twitter for the latest space news.

(MORE:  Eclipse Ahead Sunday)

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