What would it take to make a fuctioning photon rocket?

For reference closet counterpart to this would be the "wings of light" and Minovsky Drive System of the Gundam metaseries, engines that release what looks like pure light as a propellant.

• Just to clarify, are you looking for a mechanism/maths which would allow for light to be used as a propellant? or a proper design for a rocket? As a note, you would not be able to see the light from a photon rocket unless it was interacting with particles in the eject path, or if you are somehow in the blast zone of the light. – Shadowzee Aug 22 '19 at 1:44
• I would post a picture of a astronaut holding a flashlight, but apparently I can't put pictures into comments. – TheDyingOfLight Aug 22 '19 at 1:57
• Literally anything that can emit photons can act as a rocket in space for items of small enough mass, so "what it would take" to be useful is just a lot of photons. – stix Aug 22 '19 at 3:00

You can point any light source out the back of your ship and get some acceleration, but for all modern-day light-producing technologies the acceleration of the ship would be incredibly low. If you want to get decent acceleration your best bet would probably be matter-antimatter reactions powering a gamma ray laser, see the pdf of F. Winterberg's paper on the idea here and a shorter summary of his scheme here. The reason you want photons in the gamma ray frequency range is that the momentum $$p$$ of a photon is given by the equation $$p = \frac{hf}{c}$$ where $$h$$ is Planck's constant, $$f$$ is the frequency, and $$c$$ is the speed of light, so you want the frequency to be as high as possible so that the momentum added to the ship when it emits the photon (which is equal and opposite to the momentum of the photon, due to conservation of total momentum) will be as large as possible.