I can’t make it pencil out. Kudos to the team for raising so much money, though.
Here’s where I see problems. When the chamber admits air after a launch, the rotating arm will be exposed to shock wave plasma at temperatures exceeding 3000°C. That arm is made of composite carbon fiber, and its resin won’t hold up as it melts at under 1000°C.
Then there’s the balance issue. The arm is finely tuned with the payload, but the second the projectile is released, the imbalance becomes massive. At full speed, the energy in that imbalance is staggering. It’ll persist as the arm slows down, assuming it doesn’t overheat or outright explode in the process.
The energy required to create the vacuum they need isn’t being talked about enough, either. Making a vacuum of that size and tightness, for a spin chamber that large, guarantees a significant energy cost one that’s missing from their calculations. The time it takes to evacuate the chamber is also a barrier to rapid cadence.
And finally, the utility feels extremely limited. You’re restricted to small payloads that have to be over-engineered to survive thousands of Gs. If it worked, it might be useful as a planetary-scale artillery style weapon, but as a system for orbital launch, it just doesn’t add up.
