Project Orion had much more thrust than this proposal but also came attached to a very heavy lifter plate and set of shock absorbers. That meant that the only

Project Orion had much more thrust than this proposal but also came attached to a very heavy lifter plate and set of shock absorbers. That meant that the only feasible way to get Orion up to orbit was for it to fly there under its own power. That means that all the radioactive byproducts were going to end up in the atmosphere. Each bomb is tiny but you'll need a lot of them and it adds up. By contrast this drive is designed to be used in space and once you're outside the Van Allen belt you're pretty much fine to use nuclear drives. The fact that there aren't any critical masses involved also means that you're not violating the Outer Space Treaty.