Nuclear photonic rocket: Difference between revisions

at a velocity of 9,100 m/s, and 400 m/s additional velocity is obtained from the east to west rotation of the earth. The Photon thrust will be sufficient to more thenthan counterbalance

the pull of the sunssun's gravity, allowing the photon rocket to maintain a heliocentric velocity

of 240 km/s in this hypothetical case . At a 30 km/s heliocentric velocity , the photon ship would recede a distance of 600,000,000 miles from the sun per year .

It is possible to obtain even higher specific impulse; that of some other photonic propulsion devices (e.g., [[solar sail]]s) is effectively infinite because no carried fuel is required. Alternatively, such devices as [[ion thruster]]s, while having a notably lower specific impulse, give a much better thrust-to-power ratio:; for photons, that ratio is <math>1/c</math>, whereas for slow particles (that is, nonrelativistic; even the output from typical ion thrusters counts) the ratio is <math>2/v</math>, which is much larger (since <math>v\ll c</math>). (This is in a sense an unfair comparison, since the photons must be ''created'' and other particles are merely ''accelerated'', but nonetheless the impulses per carried mass and per applied energy &mdash; the practical quantities &mdash; are as given.) The photonic rocket is thus wasteful when power and not mass is at a premium, or when enough mass can be saved through the use of a weaker power source that reaction mass can be included without penalty.