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Propellant Recycling


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1 minute ago, ThatGuyWithALongUsername said:

Thrust is way, way too small. Much easier to use larger sources of energy, even in the form of photons- now we're getting into solar sail territory.

 

Or, it you want more concentrated power, lasers from the ground (so you don't have to carry their tremendous weight). See project Starshot. Still hard, though.

Power the laser with a nuclear reactor

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32 minutes ago, Cheif Operations Director said:

Now suppose that you never let go but transferred some of your heat energy into The kinetic energy of the table.

So we want to convert the vibrations of trillions if molecules, moving rapidly in every conceivable direction (heat is just the vibration of particles), into movement in one direction.

Nobody has found a way to do this yet.

9 minutes ago, Cheif Operations Director said:

Why has this not been done yet?

Extremely low thrust, I would imagine. You are expelling photons backwards. The thrust from a lightbulb is almost nothing. Scale that up to the largest photon emitter we can build, it's still almost nothing.

Note, I am not well versed in photon rockets, so that might be wrong.

9 minutes ago, Cheif Operations Director said:

I mean yes but I get new momentum by putting the liquid propellant into a chamber and turning it into a gas where it is these expelled like a normal chemical rocket, at least that was the idea.

So not really free energy

Yes. This will give you thrust and a net force on the vehicle. All is fine until you recapture the propellant. As we have been trying to explain, stopping the propellant after it exits the engine using a collector connected to the engine would negate the force of the engine.

Edited by Ultimate Steve
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5 minutes ago, Cheif Operations Director said:

I mean yes but I get new momentum by putting the liquid propellant into a chamber and turning it into a gas

You don't get momentum by heating something. You get it by pushing off something. In case of rockets they are pushing off expelled propellant (~~~). Do you understand why you cannot lift youself in the air by grabing your own hair and pulling? 

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3 minutes ago, Ultimate Steve said:

So we want to convert the vibrations of trillions if molecules, moving rapidly in every conceivable direction (heat is just the vibration of particles), into movement in one direction.

Nobody has found a way to do this yet.

Gases expand, there you go

Just now, NiL said:

You don't get momentum by heating something. You get it by pushing off something. In case of rockets they are pushing off expelled propellant (~~~). Do you understand why you cannot lift youself in the air by grabing your own hair and pulling? 

Yes

1 minute ago, NiL said:

You don't get momentum by heating something. You get it by pushing off something. In case of rockets they are pushing off expelled propellant (~~~). Do you understand why you cannot lift youself in the air by grabing your own hair and pulling? 

Ok it also pushes off of the chemical reaction, but yes your right I already know that.

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1 minute ago, Cheif Operations Director said:

Gases expand, there you go

Apologies, I phrased that last part badly, but you are correct that gas would expand when heated, and this can be exhausted to create thrust.

That was stupid of me to say, and completely incorrect. I apologise.

However, so we have a high pressure gas. How do we use that to add momentum to the table without expelling it?

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Just now, Ultimate Steve said:

Apologies, I phrased that last part badly, but you are correct that gas would expand when heated, and this can be exhausted to create thrust.

That was stupid of me to say, and completely incorrect. I apologise.

However, so we have a high pressure gas. How do we use that to add momentum to the table without expelling it?

Put it into a rocket nozzle. That creates momentum. Then use a device (let’s just call it magic for now so we can move past those technicalities) that then slows down the propellant after it has been used by the rocket and has left the nozzle. Re-capture the gas and condense it, then re-heat it. Basically a nuclear steam reactor but instead of turning a turbine you turn it into a rocket with the nozzle. 

 

That at was my idea but many people point it conservation of momentum and I need to go through the design again. I’ve been on the road all day so I need a chance to sit down with my laptop and good WiFi to do that.

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And yes, once we start talking about photon rockets, your design does produce thrust if you alter it to expel the photons more efficiently.

However, at this point you are better off replacing the propellant with something that glows very brightly when heated, and having a tank of that and photon director (mirrors) on one side of the craft.

You end up with a design that works on a completely different principle than the design you started with, but the design could never hope for even the TWR of ion engines.

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20 minutes ago, NiL said:

0_o

I agree about photons being a propellant, of cource, but they are generated from pure energy. If i will use a non-expendable light source (like heating a metal plate to produce IR radiation) and a ~non expendable energy source (solar panels), how would ship's mass decrease? I mean a metal plate can lose some matter due to outgassing and stuff, but it is not part of the ship's propulsion process.

It won't, but if you try to use solar panels to power a photon rocket, you will find that your ship is more accurately described as a solar sail with a laser steering jet. Solar panels are pushed by every photon that impacts them. After all the efficiency loses in the system, you will find that if you try to thrust straight at your star, you will accelerate away from it, because light pressure would exceed the thrust of your laser. That system would be usable for propulsion, but only if you factored in the solar sail effect and thrusted perpendicularly to the panels. Probably better to use a normal solar sail, but I can see this idea having some very niche uses (keeping a solar statite in place, for one).

Mass comes from energy you have stored in the system. A full battery is heavier than an empty one, and knowing the capacity you can very easily calculate how much. If your energy is used up, mass will decrease. If energy passes through the system instead, you need to account both for how it gets out and how it gets in. Any form of "pure energy" has mass, and this mass is E/c^2.

Edited by Guest
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2 minutes ago, Ultimate Steve said:

And yes, once we start talking about photon rockets, your design does produce thrust if you alter it to expel the photons more efficiently.

However, at this point you are better off replacing the propellant with something that glows very brightly when heated, and having a tank of that and photon director (mirrors) on one side of the craft.

You end up with a design that works on a completely different principle than the design you started with, but the design could never hope for even the TWR of ion engines.

Whom are you talking too?

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1 minute ago, Cheif Operations Director said:

Yes

You are suggesting to do the same thing with rockets. I lack the english words to say it properly, but by saying «I'll use heating to add energy into the system» you are saying «I'll invite my friend and we would grab each other's hair and would try to pull each other up. Because i'm adding momentum to my friend and he is adding monentum to me, it's not a cheat drive and we'll fly upwards, pulling each other by hair». The inner momentum of a closed system is always 0. When you are expelling propellant, you are making it into another system, so "engine system" and "propellant system" can have differet momentum relative to each other. Without permanently dividing engine and propellant into two systems you cannot give momentum, because inner momentum of a system is always 0. 

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Just now, Cheif Operations Director said:

Put it into a rocket nozzle. That creates momentum. Then use a device (let’s just call it magic for now so we can move past those technicalities) that then slows down the propellant after it has been used by the rocket and has left the nozzle. Re-capture the gas and condense it, then re-heat it. Basically a nuclear steam reactor but instead of turning a turbine you turn it into a rocket with the nozzle. 

Yes, this works!

The problem is the magic part, which, unless we discover something completely new to physics, can't be done in reality. There is no known way to produce a net positive thrust while recapturing the propellant, as to produce thrust you have to either expel something permanently (be it hydrogen, iron, or photons) or invent a device which can slow something down using less energy than it should take to slow it down, or zero energy.

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2 minutes ago, Ultimate Steve said:

The problem is the magic part, which, unless we discover something completely new to physics, can't be done in reality

This and 

Quote

There is no known way to produce a net positive thrust while recapturing the propellant, as to produce thrust you have to either expel something permanently (be it hydrogen, iron, or photons) or invent a device which can slow something down using less energy than it should take to slow it down, or zero energy.

This conflict with each other, are you saying the recapturing part is not possible or the slowing it down without causing “drag” is not possible

The slowing down device can take up as much energy as the reactor can provide

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1 minute ago, Cheif Operations Director said:

This conflict with each other, are you saying the recapturing part is not possible or the slowing it down without causing “drag” is not possible

Slowing down something completely without a "drag" equal to the momentum of the propellant is impossible without the said magic device or a new revolutionary discovery.

I do not see how my responses conflict. In the first part, I said it's impossible without that magic device, in the second part I say that it is impossible without a new discovery, akin to the magic in the first response.

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3 minutes ago, Ultimate Steve said:

I do not see how my responses conflict. In the first part, I said it's impossible without that magic device, in the second part I say that it is impossible without a new discovery, akin to the magic in the first response

I think I misread what you were saying sorry

 

3 minutes ago, Ultimate Steve said:

Slowing down something completely without a "drag" equal to the momentum of the propellant is impossible without the said magic device or a new revolutionary discovery.

I agree. My proposal is to angle the “device”in such a way that it does not affect (in terms of “drag” ) the forward or backward momentum, only the up/down and side to side momentum. It creates drag but it does not affect the forward thrust. 

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Again, move your talks of recycling propellant out of this thread. 

A. Because this has a high chance of being a nuclear jet engine, which would just accelerate air, no onboard propellant or propellant recycling required.

B. This is about an accident with a nuclear propulsion system, not about recycling propellant

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4 minutes ago, Cheif Operations Director said:

I agree. My proposal is to angle the “device”in such a way that it does not affect (in terms of “drag” ) the forward or backward momentum, only the up/down and side to side momentum. It creates drag but it does not affect the forward thrust. 

If you eventually slow the exhaust down to zero forward and backward momentum, and deflect it so it only has sideways momentum, something has to cancel out that forward and backward momentum, and that something is most likely on the craft.

We have taken the thread waaaay too off topic. If you would like to continue the conversation I suggest creating your own thread with a proper diagram and explanation of the device in the OP.

The last thing I wish to say on this matter in this thread is that if it was that easy to accelerate without using propellant, someone would have done it already.

Although I do admire your sincerity and desire to understand. I am glad this has not devolved into a shouting match.

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3 minutes ago, Ultimate Steve said:

If you eventually slow the exhaust down to zero forward and backward momentum, and deflect it so it only has sideways momentum, something has to cancel out that forward and backward momentum, and that something is most likely on the craft.

We have taken the thread waaaay too off topic. If you would like to continue the conversation I suggest creating your own thread with a proper diagram and explanation of the device in the OP.

The last thing I wish to say on this matter in this thread is that if it was that easy to accelerate without using propellant, someone would have done it already.

Ok

7 minutes ago, Ultimate Steve said:

If you eventually slow the exhaust down to zero forward and backward momentum, and deflect it so it only has sideways momentum, something has to cancel out that forward and backward momentum, and that something is most likely on the craft.

We have taken the thread waaaay too off topic. If you would like to continue the conversation I suggest creating your own thread with a proper diagram and explanation of the device in the OP.

The last thing I wish to say on this matter in this thread is that if it was that easy to accelerate without using propellant, someone would have done it already.

Although I do admire your sincerity and desire to understand. I am glad this has not devolved into a shouting match.

Thank you I reposted the topic

9 minutes ago, Ultimate Steve said:

If you eventually slow the exhaust down to zero forward and backward momentum, and deflect it so it only has sideways momentum, something has to cancel out that forward and backward momentum, and that something is most likely on the craft.

We have taken the thread waaaay too off topic. If you would like to continue the conversation I suggest creating your own thread with a proper diagram and explanation of the device in the OP.

The last thing I wish to say on this matter in this thread is that if it was that easy to accelerate without using propellant, someone would have done it already.

Although I do admire your sincerity and desire to understand. I am glad this has not devolved into a shouting match.

Repost this response their so people can follow the conversation

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Off shoot of a thread on Rosatom and their failure, 

 

I will post diagrams when I get back to my laptop

 

Heat your fuel in a nuclear reactor to change states from a liquid to a gas.  Put your fuel into a rocket engine,  That creates momentum. Then use a device (let’s just call it magic for now so we can move past those technicalities) that then slows down the propellant after it has been used by the rocket and has left the nozzle. Re-capture the gas and condense it, then re-heat it. Basically a nuclear steam reactor but instead of turning a turbine you turn it into a rocket with the nozzle. 

 

I would like to clarify that I am not militant in my belief that this will work, or even if it is possible. I am just proposing the idea.

Edited by Cheif Operations Director
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I was told to move the main counterargument to this thread.

Mainly, the act of capturing the exhaust would negate the effect of the engine unless the thing catching the exhaust was not attached to the craft.

If you allow magic to slow the exhaust down without negating the engine's thrust on the craft, the engine works fine.

Howevermost of us think that such a magic device cannot exist under our current understanding of physics.

Chief maintains that using angles and redirecting the exhaust sideways it can be done with current technology.

That sums it up so far, I do not have much intention of sticking around any longer.

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15 minutes ago, Cheif Operations Director said:

Off shoot of a thread on Rosatom and their failure, 

 

I will post diagrams when I get back to my laptop

 

Heat your fuel in a nuclear reactor to change states from a liquid to a gas.  Put your fuel into a rocket engine,  That creates momentum. Then use a device (let’s just call it magic for now so we can move past those technicalities) that then slows down the propellant after it has been used by the rocket and has left the nozzle. Re-capture the gas and condense it, then re-heat it. Basically a nuclear steam reactor but instead of turning a turbine you turn it into a rocket with the nozzle. 

Congratulations. You’ve just described a closed-cycle gas-cooled reactor with MHD coils.

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2 minutes ago, Ultimate Steve said:

I was told to move the main counterargument to this thread.

Mainly, the act of capturing the exhaust would negate the effect of the engine unless the thing catching the exhaust was not attached to the craft.

If you allow magic to slow the exhaust down without negating the engine's thrust on the craft, the engine works fine.

Howevermost of us think that such a magic device cannot exist under our current understanding of physics.

Chief maintains that using angles and redirecting the exhaust sideways it can be done with current technology.

That sums it up so far, I do not have much intention of sticking around any longer.

Ok fair enough, My idea was using magnets or PERHAPS positively or negative charged ions to direct the high speed gas into a certain area and then de-accelerate it with this you may be able to get it to a reasonable speed to re-condense it into a liquid 

3 minutes ago, DDE said:

Congratulations. You’ve just described a closed-cycle gas-cooled reactor with MHD coils.

What are you talking about? What is that?

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If your rocket’s propellant somehow, in any possible way, gets back into the engine, then it’s not propellant. It’s coolant, at best. Doesn’t matter how many turns or slowdowns it makes during its journey. If a closed system (engine + propellant + magnets/diverters/whatever) doesn’t expel something away, then it won’t move. It should be pretty obvious.

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7 minutes ago, sh1pman said:

If your rocket’s propellant somehow, in any possible way, gets back into the engine, then it’s not propellant. It’s coolant, at best. Doesn’t matter how many turns or slowdowns it makes during its journey. If a closed system (engine + propellant + magnets/diverters/whatever) doesn’t expel something away, then it won’t move. It should be pretty obvious.

How is it coolant?

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3 hours ago, Cheif Operations Director said:

OThen use a device (let’s just call it magic for now so we can move past those technicalities) that then slows down the propellant after it has been used by the rocket and has left the nozzle. Re-capture the gas and condense it, then re-heat it. Basically a nuclear steam reactor but instead of turning a turbine you turn it into a rocket with the nozzle. 

BujzYcWCEAA-mAk?format=jpg

Imagine the magnet is your rocket nozzle and the "metal" is what captures the propellant. See the problem? No net force, no net momentum -- no movement.

Edited by mikegarrison
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