A few weeks ago SpinLaunch managed to spin up their demonstrator and lob a projectile into the sky. I did not give it a whole lot of thought; it just doesn’t impress me a whole lot. There are easier ways to accelerate a projectile to the speed of sound.
However, Thunderf00t *did* give the concept a lot of thought, and he’s anti-impressed. One detail that I’d noticed was that the projectile emerges from the “muzzle” of the launch tube crooked. One thing I *didn’t* do was closely examine the faint and blurry in-flight footage of the projectile. And I should have, because the projectile is *tumbling.* In retrospect this makes sense: while attached to the rotating arm, the projectile is rotating at about three revolutions per second. Once released, it will retain that angular momentum; since it’s not touching anything – it’s not riding rails, or sliding down a barrel, nor at its fins reacting against air since it’s in a vacuum – there is nothing to arrest that rotation. So it leaves the “barrel” tumbling. This would be *disastrous.* Even if the fins could stabilize the projectile in flight, a massive amount of launch energy would be wasted in the process, the trajectory would be virtually randomized, accelerations would be massive and all over the place.
In short, this thing seems to be a whole lot of nothing as far as being practical.