Meet Blackbird: The homemade drone that hit nearly 700km/h https://newatlas.com/drones/biggs-blackbird-411mph/
Melbourne engineer Benjamin Biggs designed, built and flew the world’s fastest drone. It flies at more than half the speed of sound.
Mu original link, but paywalled link..... https://www.theaustralian.com.au/weekend-australian-magazine...
If he was willing to make it single use and didn't care about thermal runaway he could do better.
Missiles only have to fly once.