The Space Review by Wayne Eleazer 3/8/2021
On January 25, 1957, the first Thor IRBM launch occurred from Launch Complex 17 at Cape Canaveral Air Force Station. The objectives of that first-ever Thor launch operation were modest: to proceed down through the countdown, load the liquid oxygen, and start the engine. Anything useful that occurred after that was pure gravy. As it turned out, contamination in the liquid oxygen led to a valve failure and Thor 101 barely rose off the launch pad before the engine quit and the vehicle fell back down, creating a massive explosion and damaging the launch pad. Nonetheless, since the objectives of the operation were all met, it was a “success.â€
SpaceX has conducted a number of other similarly “successful†operations in the development of its Starship vehicle, launched from the company’s complex in Boca Chica, Texas. Most have resulted in massive explosions, but on each one something new and important was learned, and thus constituted a successful test. Some things cannot be simulated, and often a launch is the first occasion that all of the required elements actually interact.
Some things cannot be simulated, and often a launch is the first occasion that all of the required elements actually interact.With any launch there are certain hazards that have to be mitigated. Falling debris, which may contain firebrands that can have an incendiary effect, is the most obvious. Some vehicles can produce toxic clouds when they explode or burn. And when a booster blows its top, the explosion can produce significant shock waves that may not be strong enough to actually harm anyone standing in the open at some distance away but can damage structures even further away and produce casualties as a result.
The national standard for the acceptable risk posed to areas external to the launch site is a probability of 30 in a million. This originally was roughly based on the threat presented to the general public due to aircraft, the idea being that no additional risk beyond that already accepted from aviation should be allowed. Calculating the probability of casualty requires assessment of the nature of the hazard, the probability of a certain type of failure occurring in each portion of the flight, and the vulnerability of the population that can be affected. Vulnerability of the population depends on not only the number of people potentially at risk but also the type of structures they inhabit and even the time of day, since people are more likely to be inside structures at night. And just what constitutes a casualty is a complex issue that we can’t address here.
The primary means to mitigate the launch hazards is to locate launch sites away from populated areas and to limit the allowed trajectories. At Cape Canaveral, Vandenberg Air Force Base, and Wallops Flight Facility, the launch pads are located well away from populated areas, trajectories largely are limited to over-water flight paths, and evacuations are conducted on the launch base as required to limit risk exposure.
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https://www.thespacereview.com/article/4138/1
