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coolant can also significantly affect neutron scattering. The magnitude of these two effects is compared by calculating the thermal and kinetic energy components of hydrogen, as a function of temperature and specific impulse, respectively. The thermal energy is


                    Eth = kTH                      (9.1).


where k is Boltzmann's constant and T  is the hydrogen
                                     H
temperature. The kinetic energy of exhausting hydrogen nuclei is
                E    1mv 2                         (9.2)

                k    2    e

where mH is the hydrogen mass and ve is the propellent exhaust velocity. The exhaust velocity is related to the specific impulse, I , according to (13): ve = gIsp                                         (9.3)

where g is the gravitational acceleration. The thermal and kinetic energy components are shown in Figure 24. The upper kinetic energy curve represents the maximum hydrogen energy, corresponding to those propellent nuclei which have obtained exhaust velocity. The lower kinetic energy curve represents the energy of hydrogen nuclei having an average velocity equal to one half the exhaust velocity. For a coolant temperature of 50,000*K and a specific impulse