Jelaskan Operator dari Avangard (kendaraan layang hipersonik)

Andrew Cockburn, "Like a Ball of Fire: Andrew Cockburn on hypersonic weaponry", London Review of Books, vol. 42, no. 5 (5 March 2020), pp. 31–32. "'Welcome to the world of strategic analysis, where we program weapons that don't work to meet threats that don't exist.' This was what Ivan Selin, a senior Pentagon official, used to tell subordinates in the Defence Department in the 1960s." (p. 31.) Cockburn recounts impracticable-weapons projects, including Russia's Avangard "hypersonic glide missile", Ronald Reagan's "Star Wars" project, the US's 1951 nuclear-powered-bomber project, and the US's 1950s Dyna-Soar "boost-glide"-weapon project suggested by Walter Dornberger, a favorite of Hitler's who had overseen the V2 rocket program. "[T]he US and Russia have both taken Selin's axiom a step further: they mean to deploy a weapon that doesn't work against a threat that doesn't exist that was in turn developed to counter an equally non-existent threat." (p. 32.)