Assessment of the maximum velocity and efficiency of a multistage reluctance accelerator added to the theoretical section of my site, finishing series of publications dedicated to determination of the basic parameters of coilguns from analytical equations for the field and forces in electromagnets.

The formulas established for the first time which describe an achievable velocity of a projectile and acceleration efficiecy for a launcher with known length and energy capacity.

1) The key characteristic of a multi-coil electromagnetic accelerator is its caliber d. The efficiency η is directly proportional to d, and the velocity of the projectile is inversely proportional (interestingly, this corresponds well to the empirical assumption η ≈ d, which I used when writing previous articles about the properties of accelerators of various configurations). This feature distinguishes the multi-stage system from a single-stage one - where the dependence of the output speed on the caliber was much weaker.

2)The saturation induction of the accelerated body material, and the value of the winding density a (read - the quality of manufacture of accelerating coils) are also quite significant parameters.

3)The length of the accelerator and its energy capacity (that is, the characteristics that are most amenable to change by a designer) are, unfortunately, the least significant for increasing the velocity of the projectile - it depends on them only as a cubic root. That is, in order to increase the speed by 2 times while maintaining all other parameters, it is necessary to increase either the length of the accelerator or the energy consumed by 8 times. The resistivity of the wire is equally insignificant - it follows that winding of coils with an aluminum or silver conductor instead of the usual copper one which is sometimes proposed will affect the acceleration of the projectile very weakly.