We are fascinated by the hybrid rocket engine which [Ben Krasnow] built and tested in his shop. It is actually using a hollow cylinder of acrylic as the fuel, with gaseous oxygen as an oxidizer.

I’ve dabbled in hollow holds, and they've popped up in plenty of workouts over the years. I’ve never done them consistently, ...

Relativity Networks, an Orlando-based startup focused on hollow-core fibers (HCF) developed at the nearby College of Optics ...