A big space travel resource: Encyclopedia Astronautica, from a link in a Pyramid article about Sergei Korolev, the ‘Chief Designer’ behind the USSR’s space program.
For example, they have a
A Brief History of the HARP Project, which gave us Gerald Bull and the Babylon Gun, the so-called “Iraqi Super Cannon”.
On the evening March 22, 1990, at the age of 62, as Bull approached his apartment
door in Brussels, he was shot six times in the back of the head. The assassin
was reported to be Israeli military, although the case was never solved.
Gerry Bulls last Supergun was cut up and scrapped by the UN at the conclusion
of the Iraq/Kuwait war. It was never assembled or fired.