Longshot

Allow me to preface the title: Longshot Space wants to build a 6-mile-long (10-km) space cannon to shoot several-ton objects into low Earth orbit (LEO). The company has already built a working proof of concept.

Rockets are expensive, so a number of kinetic launch startups are working on ways to simply yeet payloads into orbit and bring costs down. This one's very fun – a six-mile-long concrete cannon that'll squeeze launch vehicles to Mach 30 in one second.