Photon rocket!

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draqon

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Lets make a rocket with a photons creating the impulse we need.

http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html

Not fast enough? only 1N of force for 300MW of power? than lets increase the number of photons generated. :)

(I will come back to this thread later and add details)

German researcher Eugen Sänger, who published a designed he called a ‘photon rocket’ that would use gamma rays produced by the annihilation of electrons and positrons for thrust.
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The kind of power requirements we're talking about need nuclear powerplants the size of asteroids to make this work, and even then they'd barely move under the force of a single newton. It becomes more feasible to send more massive yet slower bits of matter, like ions, since the energy required to produce the momentum change isn't as high in exchange for the mass tradeoff. Hence why ion engines are used.

Now, if we had something more power-dense, like an antimatter reactor or something fun like that, then we'd be talking!

Neat link though, a constant one-gee acceleration/declaration would get you to Venus in a day or two at the closest point, Mars in a week or two. Only problem with a system like that is that if the engine fails halfway, when you're screaming through space at relativistic speeds, you'd fling right out of the solar system and into oblivion! Or into a hung of space gravel, which at those speeds would smash the hell out of the ship.
 
Or just crash land on your target planet.you really dont turn when en route to the planet you just lead your target to the exact point using computers.
 
I'm sorry but could you explain in lay'mans terms what a photon rocket is for me?

I honestly have no clue how that would work. I know photons are basically light particles but what does this photon rocket do? shine a flashlight out the back or something?
 
fedr808 said:
I'm sorry but could you explain in lay'mans terms what a photon rocket is for me?

I honestly have no clue how that would work. I know photons are basically light particles but what does this photon rocket do? shine a flashlight out the back or something?
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Yeah, it's basically a big flashlight. Photons have momentum, so if you have a really bright light shining from your ship, the light beam will act similar to a rocket exhaust and push your ship forward. The nice thing about it is that you don't need to carry any fuel, so you don't need to worry about running out - as long as you have an energy source, you can accelerate forever. The bad thing about it is that the power requirements are huge - it takes 300 MW to get one N or force.
 
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Nasor said:
Yeah, it's basically a big flashlight. Photons have momentum, so if you have a really bright light shining from your ship, the light beam will act similar to a rocket exhaust and push your ship forward. The nice thing about it is that you don't need to carry any fuel, so you don't need to worry about running out - as long as you have an energy source, you can accelerate forever. The bad thing about it is that the power requirements are huge - it takes 3 MW to get one N or force.
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Does not seem very practical.
 
Nasor said:
Yeah, it's basically a big flashlight. Photons have momentum, so if you have a really bright light shining from your ship, the light beam will act similar to a rocket exhaust and push your ship forward. The nice thing about it is that you don't need to carry any fuel, so you don't need to worry about running out - as long as you have an energy source, you can accelerate forever. The bad thing about it is that the power requirements are huge - it takes 3 MW to get one N or force.
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So you basically could stick your butt out the back of the space ship and fart, and get more thrust..right? :)
 
The added bonus is that u can light a match behind ur butt and light the methane for even more thrust. XD
 
MacGyver1968 said:
So you basically could stick your butt out the back of the space ship and fart, and get more thrust..right? :)
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technically if you are a pilot and you are using up the life supporting system of the spaceship the excreted unwanted gases can be accelerated, however we need neutral charge noble gases here like xenon and argon since they will not stick to the metal and are easier to accelerate that way...so technically no methane from farts will not work. Photons are so efficient, for a reason of their "lack" of mass.
 
phlogistician said:
Bzzzzt! Sorry, wrong answer. Photons have zero rest mass .
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Usually when people talk about mass you can safely assume they mean "rest mass". Usually people will make a point to say "relativistic mass" if that's what they're talking about, and "mass" = "rest mass."
 
Nasor said:
Usually when people talk about mass you can safely assume they mean "rest mass". Usually people will make a point to say "relativistic mass" if that's what they're talking about, and "mass" = "rest mass."
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Except when you talk about photons, unless you have a bag full of stationary photons, ....
 
phlogistician said:
Except when you talk about photons, unless you have a bag full of stationary photons, ....
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Nothing with rest mass can travel at C, so if you say "photons can go so fast because they have no mass," (which is pretty much what he said) then obviously you're talking about rest mass - which is what people normally mean when they say "mass".
 
Anyway, yeah, they aren't really practical at the moment. If you had some amazing energy source that didn't take up much mass, like antimatter or something, then they might be worth it.
 
Nasor said:
Nothing with rest mass can travel at C, so if you say "photons can go so fast because they have no mass," (which is pretty much what he said)
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He used the word 'efficient', not 'fast', and as we are talking about a photon propulsion system, that uses momentum of the photon, to move the ship, whether there is mass or not is an important distinction. Sorry to be picky, but it's a typical Dragon post, where he gets the important detail wrong.
 
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