Transient performance of a nuclear thermal propulsion engine utilizing seeded hydrogen

Abstract

Seeding hydrogen is the process of adding a heavy noble gas (the seed) such as argon, krypton, or xenon to the hydrogen propellant. This adds another degree of freedom to the design of a nuclear thermal propulsion (NTP) engine. This is done to reduce pressure losses, improve convective heat transfer, and densify the propellant at the expense of specific impulse and wetted vehicle mass. A numerical study was conducted which predicted and examined the effects of varying the seed concentrations within the hydrogen propellant in the steady state operation of an NTP engine. The current study examines the transient effects of seeded hydrogen on vehicle performance by varying the seed amount during reactor start-up and shut-down events while allowing the engine to use pure hydrogen during steady state operation. This has shown that seeded hydrogen can also benefit the vehicle ΔV performance as a transient had rather than the bulk of the burn profile. It was also suggested that seeded hydrogen could be used to aid in burn events too large for an orbital maneuvering system but too small to justify a full NTP engine burn.