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The effect of radiation on a space craft/probe is not binary and like with all things, you have to take into account many different factors and make many trade offs often forced on you by economics and risk aversion/tolerance. In order to maintain public support and politic capital, NASA has to do some really stupid things that they wouldn't otherwise need to. SpaceX doesn't have to deal with public perception like NASA does because insurance companies and customers dealing with space are much smarter about the cost benefit. For example (citation needed but these are ballpark numbers I remember from a JPL study), if you have $500 million for a mission like NuSTAR, one that must succeed because of its scientific significance, you have to spend that money to get a 95% success probability (for the primary mission duration). You can build and launch the satellite for $250 million with an 80% probability of success (and launch two) or launch one with a 95% chance for $500 million because that last 15% has rapidly diminishing returns on capital invested. The former has a 4% chance of both failing, 64% chance of both succeeding, and 32% chance of at least one succeeding. However, after half a century NASA has found that what matters is the absolute number of failures, not number of successful missions or success rate. It's absurd, but NASA gets more funding when it successfully launches 4 out of 5 missions than if it launches 8 out of 10 for the exact same cost. This means that the two satellites for $250 million option has a one in three chance of at least one failure andh could easily cost NASA $500 million or so for another scientifically critical mission, even if one satellite makes it and the mission is successful. It gets even worse when you factor in all of the pork barrel politics going into the NASA budget. Because NASA has operations and vendors in so many districts, in order for the timing and logistics to work out in the above example, they'd have to spend closer to $300-$400 million per satellite, wait many years between launch attempts, or build both satellites at the same time and waste everything but the launch cost (only $50-100 million) in the 80% scenario where the first satellite makes. NASA has technical and political debt just like any fast moving 50+ year old organization but it is still a lean mean fighting machine that accomplishes milestones for our civilization on an annual basis. It's our political system that's bloated. |