A photon rocket
has been a leading rocket scheme that inspired generations of rocket enthusiasts. By definition, the photon rocket is a rocket
that uses thrust
from the momentum of emitted photons
(radiation pressure by emission
) for its propulsion. Photon rocket has has been widely discussed for decades as a next generation propulsion that can make interstellar flight possible, which requires the ability to propel spacecraft to speeds at least 10% of the light speed, v~0.1c = 30,000 km/sec (Tsander, 1967). Photon propulsion has been considered to be one of the best available interstellar propulsion concepts, because it is founded on established physics and technologies (Forward, 1984). Traditional photon rockets are proposed to be powered by onboard generators, as in the traditional nuclear photonic rocket
. The standard textbook case of such a rocket is the ideal case where all of the fuel is converted to photons which are radiated in the same direction. In more realistic treatments, one takes into account that the beam of photons is not perfectly collimated
, that not all of the fuel is converted to photons, and so on. A large amount of fuel would be required and the rocket would be a huge vessel. Bae recently proved that the maximum spacecraft speed achieved by onboard photon rockets even with fusion is limited by the nuclear fuel mass as described below.
The limitations posed by the rocket equation
can be overcome, as long as the reaction mass is not carried by the spacecraft. In the Beamed Laser Propulsion
(BLP), the photon generators and the spacecraft are physically separated and the photons are beamed from the photon source to the spacecraft using lasers. However, BLP is limited because of the extremely low thrust generation efficiency of photon reflection. One of the best ways to overcome the inherent inefficiency in producing thrust of the photon thruster by amplifying the momentum transfer of photons by recycling photons between two high reflectance mirrors. Read more...