I wanted to expand on one thought from last night. If you have a launch vehicle that you want a reasonably good chance of reusing 1000x, it actually needs a lot better than a 1:1000 Loss of Vehicle probability for any given mission. With a 1 in 1000 chance of losing the vehicle on any given flight, you actually have a very high chance of losing it long before the 1000th flight. The odds of not losing a vehicle in x consecutive flights with a given reliability rating (probability of a non-LOV flight) is:
Psurvive_all = PnoLOV ^ x
Or solving for the required probability of not losing a vehicle on any given flight (assuming an equal probability on any flight):
PnoLOV = Psurvive_all^(1/x)
So, if you want a 75% chance of surviving 1000 flights in a row, you get:
PnoLOV = 0.75^.001 = .9997 or about 1 in 3500 probability of losing the vehicle on any given mission.
If you’re ok with a 50% chance of surviving 1000 flights in a row, you need more like a 1 in 1500 probability of losing the vehicle on any given flight, and if you want a 90% chance, you’re up to almost one in 10,000.
Long story short, if you want a high probability of amortizing the vehicle over 1000 flights, you’ll need to do much, much, much better than the historical best reliability levels of liquid fueled rockets (98% or so at a 95% confidence interval). This suggests that design for survivability is likely going to be just as important as design for performance or design for cost if you want a lot of flights on an airframe.
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