Self-propelled artillery - Wikipedia
https://en.wikipedia.org/wiki/Self-propelled_artillery
The Army Wants Longer Barreled Howitzers To Fire Ramjet-Powered And Other Special Shells
https://www.thedrive.com/the-war-zone/21598/the-army-wants-longer-barreled-howitzers-to-fire-ramjet-powered-and-other-special-shells