COACC Rocket Engine

[atpollard]

There is an engine called TRITON that proposed LOX augmented exhaust to increase thrust on a high ISP rocket engine (to increase mission flexibility). I was trying to get a handle on the limits of this concept to apply it to other engine concepts (mostly pre-fusion).

There might be some funky conservation of momentum reactions involved. High velocity and high temperature H plasma meets low velocity and low temperature atomized LOX - reaction increases propellant mass, reduces temperature and increases the total energy (H+O = exothermic). Will the increase in mass be greater than the reduction in velocity and increase total thrust? A space "afterburner"?

 

[atpollard]

There is an engine called TRITON that proposed LOX augmented exhaust to increase thrust on a high ISP rocket engine (to increase mission flexibility). I was trying to get a handle on the limits of this concept to apply it to other engine concepts (mostly pre-fusion).

There might be some funky conservation of momentum reactions involved. High velocity and high temperature H plasma meets low velocity and low temperature atomized LOX - reaction increases propellant mass, reduces temperature and increases the total energy (H+O = exothermic). Will the increase in mass be greater than the reduction in velocity and increase total thrust? A space "afterburner"?

 

[Commander Drax]

Hi Guys thanks for the maths, I cant do stuff like that due to a brain deficiency, I just don't understand all that formula. So what I've got then is a single fusion rocket engine, producing 150 tons of thrust, consuming 77 Kl of liquid hydrogen per hour of thrust.

It's still remarkably efficient by comparison to other drives, at this level of performance is the drive still radioactive?

I always thought that radioactivity was a by product of the fusion reaction initiated within the reaction mass, so if we had a 'light bulb' type engine as posted previously would radioactivity still be a problem.

 

[Commander Drax]

Hi Guys thanks for the maths, I cant do stuff like that due to a brain deficiency, I just don't understand all that formula. So what I've got then is a single fusion rocket engine, producing 150 tons of thrust, consuming 77 Kl of liquid hydrogen per hour of thrust.

It's still remarkably efficient by comparison to other drives, at this level of performance is the drive still radioactive?

I always thought that radioactivity was a by product of the fusion reaction initiated within the reaction mass, so if we had a 'light bulb' type engine as posted previously would radioactivity still be a problem.

 

[Commander Drax]

Hi Guys thanks for the maths, I cant do stuff like that due to a brain deficiency, I just don't understand all that formula. So what I've got then is a single fusion rocket engine, producing 150 tons of thrust, consuming 77 Kl of liquid hydrogen per hour of thrust.

It's still remarkably efficient by comparison to other drives, at this level of performance is the drive still radioactive?

I always thought that radioactivity was a by product of the fusion reaction initiated within the reaction mass, so if we had a 'light bulb' type engine as posted previously would radioactivity still be a problem.

 

[TheEngineer]

Hi !

The LOX idea is pretty.
With regards to the fusion rocket nearly anything, which could be fed into a reaction chamber could be useful - in order to increase mass flow.
The fusion process itself is enough to provide the energy.
Somehow it would be like 2 component fuel, one providing the energy, the other providing the mass

The key factor is, that the nuclear reaction is another league as the LOX chemical reaction. Energetically the LOX reaction would be insignificant.

Commander, if the drive still is radioactive is a good question.
So far I found no rulewise note, that it is.
Now there are indeed pretty clean fusion reaction types and perhaps at higher TL the exhaust is no longer radioactive because the reactions are "under total control".

regards,

TE

 

[TheEngineer]

Hi !

The LOX idea is pretty.
With regards to the fusion rocket nearly anything, which could be fed into a reaction chamber could be useful - in order to increase mass flow.
The fusion process itself is enough to provide the energy.
Somehow it would be like 2 component fuel, one providing the energy, the other providing the mass

The key factor is, that the nuclear reaction is another league as the LOX chemical reaction. Energetically the LOX reaction would be insignificant.

Commander, if the drive still is radioactive is a good question.
So far I found no rulewise note, that it is.
Now there are indeed pretty clean fusion reaction types and perhaps at higher TL the exhaust is no longer radioactive because the reactions are "under total control".

regards,

TE

 

[TheEngineer]

Hi !

The LOX idea is pretty.
With regards to the fusion rocket nearly anything, which could be fed into a reaction chamber could be useful - in order to increase mass flow.
The fusion process itself is enough to provide the energy.
Somehow it would be like 2 component fuel, one providing the energy, the other providing the mass

The key factor is, that the nuclear reaction is another league as the LOX chemical reaction. Energetically the LOX reaction would be insignificant.

Commander, if the drive still is radioactive is a good question.
So far I found no rulewise note, that it is.
Now there are indeed pretty clean fusion reaction types and perhaps at higher TL the exhaust is no longer radioactive because the reactions are "under total control".

regards,

TE

 

[atpollard]

The Nuclear Light Bulb type of nuclear engines work with both fission and fusion. The propellant never touches the radioactive fuel, so there is no danger of radiation unless the engine explodes.

 

[atpollard]

The Nuclear Light Bulb type of nuclear engines work with both fission and fusion. The propellant never touches the radioactive fuel, so there is no danger of radiation unless the engine explodes.

 

[atpollard]

The Nuclear Light Bulb type of nuclear engines work with both fission and fusion. The propellant never touches the radioactive fuel, so there is no danger of radiation unless the engine explodes.

 

[Wm_Humphrey]

If there would be a chemical reaction, but the energy provided by that is scales lower compared to the amount provided by fusion process, especially if the reaction mass flow is low...
Besdies the temperature level of the main exhaust would be much to high to let a usable H-O reaction happen.
This reaction might occur at more remote regions where temperatur drops below plasma limit...

You're basically right - the temperatures in the exhaust would still be high enough for it to be a plasma. No chemical reactions would be possible until the temperature dropped, likely far beyond the end of your nozzle.

Hydrogen and oxygen can react quickly enough to burn at supersonic speed - that's called a "scramjet" (Supersonic Combustion Ramjet). You use supersonic shock waves to compress and heat the incoming air, inject gaseous hydrogen into the combustor where the flow is still supersonic. (A ramjet has to slow the flow in the combustor to subsonic speeds.) The heat from the combustion causes the exhaust to accelerate and create thrust. NASA successfully flew a scramjet testbed to almost Mach 10 back at the end of 2004.
http://www.nasa.gov/centers/dryden/history/pastprojects/X43/index.html

But scramjets are still air-breathing engines limited to planetary atmospheres.

Bill H

 

[Wm_Humphrey]

If there would be a chemical reaction, but the energy provided by that is scales lower compared to the amount provided by fusion process, especially if the reaction mass flow is low...
Besdies the temperature level of the main exhaust would be much to high to let a usable H-O reaction happen.
This reaction might occur at more remote regions where temperatur drops below plasma limit...

You're basically right - the temperatures in the exhaust would still be high enough for it to be a plasma. No chemical reactions would be possible until the temperature dropped, likely far beyond the end of your nozzle.

Hydrogen and oxygen can react quickly enough to burn at supersonic speed - that's called a "scramjet" (Supersonic Combustion Ramjet). You use supersonic shock waves to compress and heat the incoming air, inject gaseous hydrogen into the combustor where the flow is still supersonic. (A ramjet has to slow the flow in the combustor to subsonic speeds.) The heat from the combustion causes the exhaust to accelerate and create thrust. NASA successfully flew a scramjet testbed to almost Mach 10 back at the end of 2004.
http://www.nasa.gov/centers/dryden/history/pastprojects/X43/index.html

But scramjets are still air-breathing engines limited to planetary atmospheres.

Bill H

 

[Wm_Humphrey]

If there would be a chemical reaction, but the energy provided by that is scales lower compared to the amount provided by fusion process, especially if the reaction mass flow is low...
Besdies the temperature level of the main exhaust would be much to high to let a usable H-O reaction happen.
This reaction might occur at more remote regions where temperatur drops below plasma limit...

You're basically right - the temperatures in the exhaust would still be high enough for it to be a plasma. No chemical reactions would be possible until the temperature dropped, likely far beyond the end of your nozzle.

Hydrogen and oxygen can react quickly enough to burn at supersonic speed - that's called a "scramjet" (Supersonic Combustion Ramjet). You use supersonic shock waves to compress and heat the incoming air, inject gaseous hydrogen into the combustor where the flow is still supersonic. (A ramjet has to slow the flow in the combustor to subsonic speeds.) The heat from the combustion causes the exhaust to accelerate and create thrust. NASA successfully flew a scramjet testbed to almost Mach 10 back at the end of 2004.
http://www.nasa.gov/centers/dryden/history/pastprojects/X43/index.html

But scramjets are still air-breathing engines limited to planetary atmospheres.

Bill H

 

[Wm_Humphrey]

Originally posted by TheEngineer:
Hi !

An pretty easy approach is to use the simple formula for thrust based on reaction:

Thrust[N] = Mass-Flow[kg/s-1] * Exhaust velocity [m/s]

or
Needed Exhaust velocity [m/s] = Thrust/Massflow
...
You can use this one to check which values given in the rulesets are ok or just bullshit.
A mass-flow of 5 l/hour is just around 0,0001 kg/s (different result here Humphrey ?). For a rocket this is near to nothing.
The needed exhaust velocities to get 130 tons of thrust are beyond reality, namely

1300000 N / 0.0001 kg/s-1 = 13371428571 m/s

As you might see, the result is a bit unphysical

...
regards,

TE

"Hi!" right back at you! It's good to be indulging my Trav gearhead side again!

You are obviously correct about the formula for thrust. Specific impulse is directly related to the exhaust velocity of a rocket. And the exhaust velocity is related to the combustion chamber temperature and pressure, since you can't expand the exhaust all the way to zero absolute pressure.

Using Newton's second law is a good sanity check since the exhaust also obviously can't exceed the speed of light (300,000,000 m/s)!

You are also correct that a volume flow rate of 5 L/hr corresponds to a mass flow rate of just a hair under 0.0001 kg/s for liquid hydrogen. My figure of 0.01 kg/s was what the fuel consumption rate (per "ton" of thrust) should be if you assume a specific impulse of 100,000 seconds.

For the chemical rockets, though, you have to use the "Cryo" fuel (which is just average density of the proper mixture of liquid hydrogen and liquid oxygen for good combustion). Chemically, you need 1 kg of hydrogen and 8 kg of oxygen for perfect combustion (no leftover hydrogen or oxygen). The density of 0.35 ton/kL gives a ratio of 1 kg hydrogen to about 6 kg oxygen, which is the mixture used by the shuttle main engines. You do actually need a surplus of one component (hydrogen in this case, also used to keep the nozzle cool) for fast, stable combustion. So at least the fuel info. is correct.

Cheers,
Bill H

 

[Wm_Humphrey]

Originally posted by TheEngineer:
Hi !

An pretty easy approach is to use the simple formula for thrust based on reaction:

Thrust[N] = Mass-Flow[kg/s-1] * Exhaust velocity [m/s]

or
Needed Exhaust velocity [m/s] = Thrust/Massflow
...
You can use this one to check which values given in the rulesets are ok or just bullshit.
A mass-flow of 5 l/hour is just around 0,0001 kg/s (different result here Humphrey ?). For a rocket this is near to nothing.
The needed exhaust velocities to get 130 tons of thrust are beyond reality, namely

1300000 N / 0.0001 kg/s-1 = 13371428571 m/s

As you might see, the result is a bit unphysical

...
regards,

TE

"Hi!" right back at you! It's good to be indulging my Trav gearhead side again!

You are obviously correct about the formula for thrust. Specific impulse is directly related to the exhaust velocity of a rocket. And the exhaust velocity is related to the combustion chamber temperature and pressure, since you can't expand the exhaust all the way to zero absolute pressure.

Using Newton's second law is a good sanity check since the exhaust also obviously can't exceed the speed of light (300,000,000 m/s)!

You are also correct that a volume flow rate of 5 L/hr corresponds to a mass flow rate of just a hair under 0.0001 kg/s for liquid hydrogen. My figure of 0.01 kg/s was what the fuel consumption rate (per "ton" of thrust) should be if you assume a specific impulse of 100,000 seconds.

For the chemical rockets, though, you have to use the "Cryo" fuel (which is just average density of the proper mixture of liquid hydrogen and liquid oxygen for good combustion). Chemically, you need 1 kg of hydrogen and 8 kg of oxygen for perfect combustion (no leftover hydrogen or oxygen). The density of 0.35 ton/kL gives a ratio of 1 kg hydrogen to about 6 kg oxygen, which is the mixture used by the shuttle main engines. You do actually need a surplus of one component (hydrogen in this case, also used to keep the nozzle cool) for fast, stable combustion. So at least the fuel info. is correct.

Cheers,
Bill H

 

[Wm_Humphrey]

Originally posted by TheEngineer:
Hi !

An pretty easy approach is to use the simple formula for thrust based on reaction:

Thrust[N] = Mass-Flow[kg/s-1] * Exhaust velocity [m/s]

or
Needed Exhaust velocity [m/s] = Thrust/Massflow
...
You can use this one to check which values given in the rulesets are ok or just bullshit.
A mass-flow of 5 l/hour is just around 0,0001 kg/s (different result here Humphrey ?). For a rocket this is near to nothing.
The needed exhaust velocities to get 130 tons of thrust are beyond reality, namely

1300000 N / 0.0001 kg/s-1 = 13371428571 m/s

As you might see, the result is a bit unphysical

...
regards,

TE

"Hi!" right back at you! It's good to be indulging my Trav gearhead side again!

You are obviously correct about the formula for thrust. Specific impulse is directly related to the exhaust velocity of a rocket. And the exhaust velocity is related to the combustion chamber temperature and pressure, since you can't expand the exhaust all the way to zero absolute pressure.

Using Newton's second law is a good sanity check since the exhaust also obviously can't exceed the speed of light (300,000,000 m/s)!

You are also correct that a volume flow rate of 5 L/hr corresponds to a mass flow rate of just a hair under 0.0001 kg/s for liquid hydrogen. My figure of 0.01 kg/s was what the fuel consumption rate (per "ton" of thrust) should be if you assume a specific impulse of 100,000 seconds.

For the chemical rockets, though, you have to use the "Cryo" fuel (which is just average density of the proper mixture of liquid hydrogen and liquid oxygen for good combustion). Chemically, you need 1 kg of hydrogen and 8 kg of oxygen for perfect combustion (no leftover hydrogen or oxygen). The density of 0.35 ton/kL gives a ratio of 1 kg hydrogen to about 6 kg oxygen, which is the mixture used by the shuttle main engines. You do actually need a surplus of one component (hydrogen in this case, also used to keep the nozzle cool) for fast, stable combustion. So at least the fuel info. is correct.

Cheers,
Bill H

 

[Wm_Humphrey]

Originally posted by Commander Drax:
Hi Guys thanks for the maths, I cant do stuff like that due to a brain deficiency, I just don't understand all that formula. So what I've got then is a single fusion rocket engine, producing 150 tons of thrust, consuming 77 Kl of liquid hydrogen per hour of thrust.

It's still remarkably efficient by comparison to other drives, at this level of performance is the drive still radioactive?

Drax,

Yes, by my figures, the fusion rocket unit that produces 150 tons of thrust should consume 77 kL of LHyd per hour of operation if it has a specific impulse in line with what I was told years ago. I'd even be willing to go along with a total fuel consumption for the unit of 50 kL/hr to make the numbers nice and round (that would be a specific impulse of a bit over 150,000 seconds for the TL-8 unit and just over 200,000 seconds for the TL-9 unit).

Yes, the exhaust would be radioactive. But it would mostly be short-lived, unlike fission by-products. In space, especially deep space outside the magnetosphere of a planet, the radiation would be trvial unless you deliberately used your drive like a crude plasma gun.

I would imageine that a fusion rocket would require a fairly substantial amount of energy to kick-start, and would act very much like the MagentoPlasmaDynamic engine until it heats up enough for the actual fusion reaction to start. The batteries required to do this would be built into the engine and automatically recharged once it starts so overall, it's self-starting. The answer to radioactive exhaust in low orbit wuold be to revert to an MPD mode. It would consume power instead of produce power and only generate a few percent of its rated thrust (imagine putting a stick-shift car in first gear and moving it a few yards with the starter motor because you've disconnected the fuel injectors), but it would work.

Bill H.

 

[Wm_Humphrey]

Originally posted by Commander Drax:
Hi Guys thanks for the maths, I cant do stuff like that due to a brain deficiency, I just don't understand all that formula. So what I've got then is a single fusion rocket engine, producing 150 tons of thrust, consuming 77 Kl of liquid hydrogen per hour of thrust.

It's still remarkably efficient by comparison to other drives, at this level of performance is the drive still radioactive?

Drax,

Yes, by my figures, the fusion rocket unit that produces 150 tons of thrust should consume 77 kL of LHyd per hour of operation if it has a specific impulse in line with what I was told years ago. I'd even be willing to go along with a total fuel consumption for the unit of 50 kL/hr to make the numbers nice and round (that would be a specific impulse of a bit over 150,000 seconds for the TL-8 unit and just over 200,000 seconds for the TL-9 unit).

Yes, the exhaust would be radioactive. But it would mostly be short-lived, unlike fission by-products. In space, especially deep space outside the magnetosphere of a planet, the radiation would be trvial unless you deliberately used your drive like a crude plasma gun.

I would imageine that a fusion rocket would require a fairly substantial amount of energy to kick-start, and would act very much like the MagentoPlasmaDynamic engine until it heats up enough for the actual fusion reaction to start. The batteries required to do this would be built into the engine and automatically recharged once it starts so overall, it's self-starting. The answer to radioactive exhaust in low orbit wuold be to revert to an MPD mode. It would consume power instead of produce power and only generate a few percent of its rated thrust (imagine putting a stick-shift car in first gear and moving it a few yards with the starter motor because you've disconnected the fuel injectors), but it would work.

Bill H.

 

[Wm_Humphrey]

Originally posted by Commander Drax:
Hi Guys thanks for the maths, I cant do stuff like that due to a brain deficiency, I just don't understand all that formula. So what I've got then is a single fusion rocket engine, producing 150 tons of thrust, consuming 77 Kl of liquid hydrogen per hour of thrust.

It's still remarkably efficient by comparison to other drives, at this level of performance is the drive still radioactive?

Drax,

Yes, by my figures, the fusion rocket unit that produces 150 tons of thrust should consume 77 kL of LHyd per hour of operation if it has a specific impulse in line with what I was told years ago. I'd even be willing to go along with a total fuel consumption for the unit of 50 kL/hr to make the numbers nice and round (that would be a specific impulse of a bit over 150,000 seconds for the TL-8 unit and just over 200,000 seconds for the TL-9 unit).

Yes, the exhaust would be radioactive. But it would mostly be short-lived, unlike fission by-products. In space, especially deep space outside the magnetosphere of a planet, the radiation would be trvial unless you deliberately used your drive like a crude plasma gun.

I would imageine that a fusion rocket would require a fairly substantial amount of energy to kick-start, and would act very much like the MagentoPlasmaDynamic engine until it heats up enough for the actual fusion reaction to start. The batteries required to do this would be built into the engine and automatically recharged once it starts so overall, it's self-starting. The answer to radioactive exhaust in low orbit wuold be to revert to an MPD mode. It would consume power instead of produce power and only generate a few percent of its rated thrust (imagine putting a stick-shift car in first gear and moving it a few yards with the starter motor because you've disconnected the fuel injectors), but it would work.

Bill H.