A Survey of the Lightning Launch Commit Criteria

The Lightning Launch Commit Criteria (LLCC) are a set of weather rules to avoid natural and rocket triggered lightning to in-flight rockets. Rocket triggered lightning occurs when naturally occurring stronger than normal electric fields are compressed until they reach the electrical breakdown voltage gradient of air, triggering a lightning strike to the rocket. The compression of the pre-existing electric field is primarily from the high temperature of the exhaust plume, which makes it electrically conductive. The size and shape of the rocket, and the composition of the fuel, also contributes to the electric field compression. Many atmospheric phenomena lead to electric fields that are sufficiently strong for rocket triggered lightning, but not natural lightning. Even stratus clouds can have sufficiently strong electric fields for rocket-triggered lightning, if they are thick enough and reach the correct temperature level. The same set of LLCC are used for space launches by the US Air Force, NASA, and others. The LLCC are the second leading weather cause of launch delays and scrubs from Cape Canaveral Air Force Station and NASA Kennedy Space Center. The LLCC are very different from most other operational weather support. This paper will review the basic mechanisms of the LLCC, the history of their development, the current set of LLCC, how they are evaluated operationally, and requirements for future improvements.