Constant Power Throttling is made possible by changing the relative fraction of power going to the first stage (helicon) and second stage (ion cyclotron heating (ICH)) systems and simultaneously changing the rate at which the propellant gas is fed into the engine. For high thrust, power is routed predominantly to the helicon with propellant consumed at a relatively high rate, producing more ions at lower exhaust velocity (low Isp). For high Isp, more power is diverted to the ICH while less power and propellant are being fed to the helicon with concomitant reductions in thrust.
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