The lack of inlet duct and the use of dense liquid propellant allows the pressurisation system to be small and lightweight, whereas duct engines have to deal with air which has a density about one thousand times lower. Moto X3M.

What it boils down to is that if the delta V requirements for the mission is less than or about equal to the exhaust velocity, the mass ratio is modest and large payloads are possible. Retrieved July 19,

Retrieved August 30, All three modes share the fusion reactor as the power source, but use the power in three different ways.