Founded in 1961 and abandoned in 1967, HARP research program (High Altitude Research Project) was a joint initiative of the US and Canadian military officials. The goal of the project was to explore the ballistics of delivering objects into the upper layers of atmosphere and beyond.
In short, the aim of the project was the creation of a giant cannon with the ability to shoot into space. The fruit of this collaboration is a huge gun rusting at the site of Barbados.
One of the authors of this project was a ballistic engineer Gerald Bull. Initially he designed a 50-caliber naval weapon, which was supposed to be installed on warships, and then he increased its caliber to 100. The gun turned out to be too big for effective military use, but seemed ideal to deliver satellites into orbit. It would fire a projectile in a special heat-resistant shell that protected the satellite from heating.
At the peak of experiments, in 1963, the gun fired up to a staggering 180 kilometers into the sky, setting a world record for gunfire height-wise. Incidentally, this record has not yet been broken.
When the US- and Canadian government shifted their priorities towards the Vietnam War, they withdrew HARP funding in 1967. The skeleton of a giant space gun was left to rust on its original launch site. You can see it with your own eyes, if you hike along the south coast of Barbados. By now, the gun is almost impossible to recognize, since it has been covered in growing bush and it has been almost completely consumed by corrosion.