Untrue. Project Longshot, using nuclear pulse propulsion, did not rely on non-existent or impractical technologies. And it was developed in the 1980s.
Similar to Project Daedalus, Longshot was designed with existing technology in mind, although some development would have been required. For example, the Project Longshot concept assumes "a three-order-of-magnitude leap over current propulsion technology".
Quoting from the Wikipedia article on the subject:QuoteSimilar to Project Daedalus, Longshot was designed with existing technology in mind, although some development would have been required. For example, the Project Longshot concept assumes "a three-order-of-magnitude leap over current propulsion technology"."Some development" is quite the understatement. We don't have inertial confinement fusion of the kind of efficiency necessary for Longshot, and we don't have ANY machine that can be expect to keep working for 100 years without any kind of human intervention, much less a 300 kw fission reactor at full blast. So I would say Project Longshot very much relied on technology that does not exist even now, 30 years later.Regarding the technical difficulties, Breakthrough Starshot seems at least as doable ...
(Sorry haven't read the entire thread. If you know it has already been discussed just say so and I will trawl for it. If you know who by that could help locate it maybe.)Has there been discussion of the vast range of nearer targets this could apply to? Obviously you would not just run it once and there are hundreds of known dwarf planets and a possible new ninth planet in our solar system that are still well out of practical reach. Perhaps such lasers could have duel uses also such as powering thermal or electric propulsion near earth or a probe far from the sun?Another possible application of this array: space junk removal?(I know RobotBeat doesn't like the beamed power idea compared to SEP but I can't remember the issue. Sorry RB.)