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(Seriously) Really Advanced Technologies: Photon propulsion.


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I would like to see some really advanced technologies. While we are expecting parts like ion engines and interstellar ships, and (I personally) ruled out unrealistic or too futurist techs like warp drive(have we?) and teleporting(definitely), I have some ideas that may worth considering. Technologies that are somehow practical but not yet fulfilled in real life.

(I have even considered how to make this practical in programming)

Photon Propulsion.

The idea is to add a fule called "P" which can be generated with massless electricity alone. And "P" has mass. I know this violates Physics, but let me explain. (OK, you PhDs can skip this. I'm just a high-schooler trying to explain the theory of relativity.) In real life photons have energy as well as momentum. If you can manage to shoot photons to the back of ship at a constant rate, according to the conservation of momentum, the ship accelerates forward. Considering the fact that high-frequency photons are prone to deal damage to anything in its path, we had better shoot low-frequency photons (infared, etc.) with less energy per capita but at a denser rate. To make this possible we must provide energy to "shoot" photons. As energy is transferred to the photons' kinetic energy, the ship must other forms of energy. IF the ship "produces" the energy that makes photons on the way, for example using a fission/fusion reactor, the ship must lose mass and convert it into kinetic energy. (Mass is a form of energy.) In real life this is rarely used in space because the thrust can almost be neglected, but some missions did feature similar designs but the photons comes from the sun and is reflected to provide thrust instead of releasing photons in a constant direction. (see cosmos-1.) But as Kerbals we may make this possible by inventing engines that shoot photons at a really fast rate. 

The following calculations show that this is possible.

ftPccV.jpg

As mentioned above, if the ship reaches 0.05c (very fast even in Kerbal terms, may reach ice giants in several days at this speed), only 4.881% of the ship's mass need to be converted into energy. Considering energy losses due to imperfect converting systems, photon propulsion is still theoretically possible.

Back to the fuel"P", P stands for photons but there can be a different name anyways. The following calculations may make it clearer than words.

ftP610.jpg

So a photon thruster with a constant power of W0 subject to the theory of relativity is an equivalent to a thruster not subject to the theory of relativity whose fuel flow rate k=W0/c^2. I know there might be some programming problems to tackle, but this provides a way to make a photon engine without actually involving the theory of relativity in the game.

I really hope this can be accepted by KSP2 team or at least future KSP2 modders.:)

(Wow I believe this post can be in science&spaceflight but I'll just leave it here in KSP2 suggestions.)

Edited by AllenLi
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This sounds like a great idea for a mod! I'm concerned that the magnets required to contain photons in a space small enough to fly would be almost reality-defying, but considering that there are antimatter engines that do effectively convert mass into energy (a good portion of which comes out as photons), we might see something similar

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A photon drive would be either:

1) Antimatter powered: likely going to be in game

2) A solar sail: would be cool

3) A light sail, and some laser installation: ie beamed power propulsion, I would love this (and beamed power need not be limited to light sails)

4) Massively inefficient if powered by anything other than antimatter or solar: (if using a fusion reactor, throw the reactant mass back at high speed for more thrust per unit fuel)

Regarding the light/solar sails: Using solar panels  instead would be massively inefficient, and would be massively heavy for the miniscule thrust. Photovoltaics would be far less efficient than just reflecting the photon, they would be far heavier, and they would not be able to take nearly the same light intensity... very very very low TWR as a result.

On 8/10/2021 at 2:13 PM, t_v said:

I'm concerned that the magnets required to contain photons 

magnets do not contain photons

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36 minutes ago, KerikBalm said:

magnets do not contain photons

Precisely- meaning they would have to be reality-defying. Out of all solutions, magnets, large masses, and some sort of artificial gravity would be the only "realistic" solutions to photon storage, a term which is likely never going to have a real-life use, and in any case, you can store much larger amounts of energy in antimatter/matter containers, rendering "photon drives" mostly obsolete. But if it were implemented as a mod, I would see magnets being used to contain the light

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55 minutes ago, KerikBalm said:

Antimatter powered: likely going to be in game

Oh yeah KSP2 has antimatter.:lol:Almost forgot that. I may include this in my mod.

55 minutes ago, KerikBalm said:

A solar sail

Mankind(not Kerbalkind) now HAS sent probes(JAXA?ESA?) using solar sail, but to inner solar system (Mercury) where high DV is required and an abundance of solar power is present. And I remember watching a Scott Manley video about reaction wheels. He mentioned that a probe sent to deep space mission by NASA (voyager?) uses small panels that reflect solar light to hold altitude. Those engineers were, just too smart.

1 hour ago, KerikBalm said:

A light sail, and some laser installation

I believe this is agreed with by Stephen Hawking?

1 hour ago, KerikBalm said:

Massively inefficient

The exact problem I found out when writing configs.:o

25 minutes ago, t_v said:

photon storage

I actually mean the ship can somehow generate low-frequency photons on the way, which poses no threat the ship or whatever is in its trail.

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  • 1 month later...
On 8/13/2021 at 11:34 AM, KerikBalm said:

the magnets required to contain photons 

Magnets cannot contain photons (as he said, it would truly be reality-defying). But we can contain medium-vawelength (infrared to ultraviolet) photons using a closed 3d mirror.

Edited by qwery123
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1 hour ago, qwery123 said:

Magnets cannot contain photons (as he said, it would truly be reality-defying). But we can contain medium-vawelength (infrared to ultraviolet) photons using a closed 3d mirror.

Mirrors can't really contain photons either, as in indefinitely preserving them, they actually absorb a fair amount of them with each bounce

Edited by mcwaffles2003
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