In Jules Verne’s 1865 science fiction novel From the Earth to the Moon, three men travel to the moon aboard a projectile launched from a huge cannon. In reality, launching crews this way is impossible because of the acceleration required to reach Earth’s escape velocity of 11.2 km/s. Even using a barrel that is 270 m long like in Verne’s novel, this would result in an acceleration of 224 km/s2 or 22,845 g. For comparison, the maximum recorded g anyone has ever survived is 46.2. Using this method for space launches would therefore only be suitable for extremely tough payloads.
It’s currently unclear if the required speeds can be reached at all. Railguns are guns the fire projectiles driven by an electromagnetic current instead of explosives, and they can achieve higher speeds. Aircraft carriers have railguns that can fire projectiles at 2.4 km/s with a range of 185km. They are ideal platforms for railguns because their nuclear reactors supply enough energy and plenty of water for cooling is available. The highest speeds currently achievable for railguns is around 3 km/s, still very far from the 11.2 km/s that would be required for space launches.
Longshot is a startup that’s taking a different approach by accelerating the projectile more slowly by using a gas gun with multiple boosters. Even if they reach their goals of Mach 5 (1.7 km/s), they’d still be a long way away from what’s already doable with railguns, and even further away from escape velocity.
Nehaveigur 