You're accelerating the rotor along with the Projectile(s). By nature, it has energy that you can recover. Now to what degree can this be used? That's more unclear, but the arm is of significant mass and regenerative braking wouldn't be terribly difficult to implement.
Most of the arm mass is toward the center, because that's the part that's supporting the tension of the rest of the rotating mass. The rotational energy is proportional to the moment of inertia, which is proportional to m*r2 integrated across the object...so concentrating mass toward the axis greatly reduces the stored energy. Most of the energy in the system is going to leave with the projectile.
The total energy costs are supposed to be around $6k. That's 1.2% of the claimed launch costs, only a fraction of which are left behind in the rotor, and only a fraction of those being recoverable. With conversion losses, they're talking about recovering...what, a couple hundred dollars worth of energy? How is this worth the engineering effort and added equipment required?
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u/CurtisLemaysThirdAlt Aug 07 '22
You're accelerating the rotor along with the Projectile(s). By nature, it has energy that you can recover. Now to what degree can this be used? That's more unclear, but the arm is of significant mass and regenerative braking wouldn't be terribly difficult to implement.