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The challenge is to have small nuclear reactor powering those three vehicles by the end of 20th century. I think there's two important parts that should be overcomed in order to make it happen:
1. Technical issues of the reactor itself. How to make small enough but still have the power AND safety for its users.
2. Making society accept the reactor as usual as OTL hybrid cars/ biofuel system. Maybe convincing them using the pollution issue?