I have heard that the tiles on the space shuttle were sensitive to being wet, in that they might be damaged. I recently saw this photo, ported to be of the Space Shuttle launching. It struck me as weird, having flown through clouds, which contain significant amounts of liquid water. What were the flight rules for flying through clouds with the Shuttle?

enter image description here

  • 2
    $\begingroup$ That seems to be the last launch of the Endeavor, here's a video too. $\endgroup$
    – kim holder
    Apr 8 '16 at 15:31
  • $\begingroup$ There's a report here that mentions damage in natural rain (not artificial spray) but not from non-precipitating clouds. That might explain the difference. nasa.gov/centers/dryden/pdf/88136main_H-1484.pdf $\endgroup$
    – Andy
    Apr 8 '16 at 16:08
  • 1
    $\begingroup$ AFAIR, we weren't so much worried about the Thermal Protection System getting wet as we were worried about impact damage caused by liquid precipitation. $\endgroup$
    – Digger
    Apr 9 '16 at 19:30
  • $\begingroup$ It seems like hitting water droplets in a cloud at high speed would cause some impact damage... $\endgroup$
    – PearsonArtPhoto
    Apr 9 '16 at 22:22
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    $\begingroup$ Yeah, the rules below seem designed mostly to avoid lightning hazards and liquid precipitation. $\endgroup$ Apr 9 '16 at 22:34

Based on the picture I assume you are asking about launch constraints due to clouds (versus cloud rules relating to shuttle entry and landing). Fortunately there is a nice human readable summary here, and the cloud rules are

Cumulus Clouds: Do not launch through cumulus- type clouds with tops higher than the 41 degree 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 degree 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.

Disturbed Weather: Do not launch if the flight path is through any non-transparent clouds that extend to altitudes at or above the 32 degrees F level, which are associated with disturbed weather producing moderate or greater precipitation, or melting precipitation, within 5 nautical miles of the flight path.

Thick Clouds: Do not launch if any part of the planned flight path is through a layer of clouds within 5 nautical miles, is 4,500 feet thick or greater, and the temperature is between 32 degrees F and -4 degrees F. Launch may occur if the cloud layer is a cirrus-like cloud that never has been associated with convective clouds, is located entirely at temperatures of 5 degrees F or colder, and shows no evidence of containing water droplets.

Anvil Cloud: Do not launch through an attached or detached anvil cloud if it is within 10 nautical miles of the launch pad if it is determined to be electrified and could trigger a lightning strike by flight through the cloud. Launch can be permitted if the conditions in the launch criteria directives for Volume-Averaged Height-Integrated Radar Reflectivity (VAHIRR) are met. This specifies the distance, time, radar and field mill measurements required to ensure safe flight. The condition of an anvil cloud must be evaluated for these criteria when it is within 10 nautical miles of the launch pad.

Debris Cloud: Unless VAHIRR launch criteria directives permit, do not launch if the flight path will carry the vehicle through a debris cloud which is not transparent and less than three hours old. Launch may not occur within five nautical miles of these debris clouds unless: 1) for 15 minutes preceding launch there is at least one working field mill within five nautical miles of the debris cloud; 2) all electric field mill readings are between -1 kilovolt and + 1 kilovolt per meter within 5 nautical miles of the flight path for the past 15 minutes; 3) weather radar has detected less than 10 dbz of reflectivity in the debris cloud within 5 nautical miles of the flight path for 15 minutes.

Smoke Plume: Do not launch if the flight path will carry the vehicle through any cumulus cloud that has developed from a smoke plume while the cloud is attached to the plume, or for the first 60 minutes after the cumulus cloud detaches from the smoke plume.

The Eastern Test Range also had range safety cloud constraints, to wit:

Direct visual observation of the shuttle is required through 8,000 feet. This requirement may be satisfied using optical tracking sites or a forward observer.

– A cloud ceiling of 6,000 feet is permitted for short- duration launch windows if all required range safety instrumentation systems are functioning.

– A cloud ceiling of 4,000 feet is permitted if:

a) The cloud layers between 4,000 and 8,000 feet are not more than 500 feet thick.

b) The vehicle can be seen by the Eastern Range airborne and/or the ground forward observers through 8,000 feet and they can communicate with the flight control officer.

There were other weather related constraints at the link provided earlier.

There were weather constraints for the abort landing sites as well.

And, there were many and different weather rules for landing. Also summarized at the link.


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