Hypervelocity Projectiles
 

Not really aviation related, but I find it interesting nonetheless:

https://scout.com/military/warrior/A...Guns-103103278

Navy to Fire Rail Gun Round from 5-inch Guns

How do you propel them to such speed?

Some practical and integration aspects of electric rail guns

https://www.wired.com/2014/08/the-ph...f-the-railgun/

US Navy's Railgun Dream Could Be Denied By Two Big Problems | The National Interest Blog

ISTR reading a plan about using kinetic weapons from the SR71. This was mooted back in the 1980's, as a way of taking out certain hardened faciilties over in Redland, with using nukes. I think it might have been mentioned in Paul Crickmore's book on the Blackbird.:8