Author Topic: Gaseous Core Nuclear Thermal Rocket  (Read 5166 times)

Offline cjackson

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Gaseous Core Nuclear Thermal Rocket
« on: 09/17/2011 06:20 AM »
http://www.projectrho.com/rocket/enginelist.php#id--Gaseous_Core_Nuclear_Thermal_Rocket

http://en.wikipedia.org/wiki/Gas_core_reactor_rocket

How practical would this be? How much of a technological leap would be needed to achieve this?

Would it make outer solar system missions possible?

Could the technology be used for non space applications?

Offline strangequark

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #1 on: 09/17/2011 07:28 AM »
http://www.projectrho.com/rocket/enginelist.php#id--Gaseous_Core_Nuclear_Thermal_Rocket

http://en.wikipedia.org/wiki/Gas_core_reactor_rocket

How practical would this be? How much of a technological leap would be needed to achieve this?

Fuel confinement is a massive issue. If you're open cycle, you need to know the fluid mechanics in the system very precisely, and ensure that the flowfield provides containment of the fissile material. Then, your propellant temperature is still in excess of what we know how to handle (at least if you want to gain anything...). It's an open question as to whether this would be a substantially better system than a solid core NTR. Call me crazy, but I'm not fond of gaseous fissioning material floating around my rocket engine. Closed cycle has more merit, I'm a little bit of a fan of the "Nuclear Lightbulb", but admittedly that concept only allows a relatively modest increase over a solid core.

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Would it make outer solar system missions possible?

Dual mode nuclear with a high-efficiency electric thruster is going to be a better, more reliable, easier to develop option.

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Could the technology be used for non space applications?

God I hope not.

Also, if you want to talk advanced nuclear rockets where we don't care spewing out radioactive plumes, then this is a better crazy idea:

Fission Fragment Rocket
« Last Edit: 09/17/2011 07:31 AM by strangequark »

Offline DLR

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #2 on: 09/17/2011 11:39 AM »
Why would you care about fission products exiting your engine in space, unless you aim your exhaust plume at something inhabited?

The fission products would travel at a velocity far exceeding solar escape velocity, and interplanetary space is filled with deadly ionising radiation anyway ...

Offline jbrooks

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #3 on: 09/17/2011 02:42 PM »
Closed cycle has more merit, I'm a little bit of a fan of the "Nuclear Lightbulb", but admittedly that concept only allows a relatively modest increase over a solid core.

Solid core NTR's achieve an Isp of about 800-900 sec (This is data from  experimental engines that the US and Soviets ground tested in the 60's and 70's. The Americans was on the low end of the range - the Russians got above 900 sec!).

US - http://www.astronautix.com/engines/nerva.htm
Soviet - http://www.astronautix.com/engines/rd0410.htm

For the "nuclear lightbulb," it's about 1800-3000 sec, depending on your source. Figure in the fact that increasing Isp has an exponential effect on your mass ratio, and the benefits are even greater.

However, I'm practical and don't think that gas-core is a viable technology any time soon - provided that no "quantum leap" in materials engineering occurs.
« Last Edit: 09/19/2011 08:15 PM by jbrooks »

Offline strangequark

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #4 on: 09/17/2011 09:02 PM »
Why would you care about fission products exiting your engine in space, unless you aim your exhaust plume at something inhabited?

The fission products would travel at a velocity far exceeding solar escape velocity, and interplanetary space is filled with deadly ionising radiation anyway ...

Didn't say we did. Just that if it's an application where you don't, and you're working at those temperatures, etc, then fission fragment is higher Isp and probably easier.

For the "nuclear lightbulb," it's about 1800-3000 sec, depending on your source. Figure in the fact that increasing Isp has an exponential effect on your DV, and the benefits are even greater.

However, I'm practical and don't think that gas-core is a viable technology any time soon - provided that no "quantum leap" in materials engineering occurs.

That's only if you can drive the container temperature as high as we think. That is an open question. Practically speaking, it may not get that high.
« Last Edit: 09/17/2011 09:25 PM by strangequark »

Offline john smith 19

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #5 on: 09/18/2011 12:54 PM »
http://www.projectrho.com/rocket/enginelist.php#id--Gaseous_Core_Nuclear_Thermal_Rocket

http://en.wikipedia.org/wiki/Gas_core_reactor_rocket
You do get that this is a site for SF authors to improve the S in their F?
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How practical would this be?
Compared to what? It's much less developed than NERVA and probably less polluting than an Orion drive.

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How much of a technological leap would be needed to achieve this?
Substantial. Look at the dimensions on those chambers and consider how you're going to make them
This gives a bit more science to what you're asking.
http://en.wikipedia.org/wiki/Gas_core_reactor_rocket
Which suggests why some of those Isp figures might be *quite* optimistic.
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Would it make outer solar system missions possible?

Do you mean crewed outer solar system missions? They *are* possible with other methods whose TRL is *much* higher than this. It depends how much someone wanted to trash their home planet and pollute the rest of the solar system.

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Could the technology be used for non space applications?
Well at those temperatures nearly everything could be incinerated.
Of course the "ash" would be radioactive but anything which was poisonous by its structure (industrial chemicals) rather than their atoms (Lead, Cadmium, Mercury) could be rendered harmless.

« Last Edit: 09/18/2011 01:10 PM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C Apply So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline jbrooks

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #6 on: 09/18/2011 04:28 PM »
Compared to what? It's much less developed than NERVA and probably less polluting than an Orion drive.

This about sums it up. For near-term nuclear propulsion, a NERVA-style system is by far the most practical. For long-term interplantery propulsion, there are other systems - Hall thrusters/Ion drives, VASIMR/MPD, etc. - that are easier to develop.

Since, as others have pointed out, pollution doesn't matter in space - Orion would get higher thrust and Isp than a gas-core. The odds of getting either in our nuclear-phobic world are about the same, but that's for another thread.  :)

Offline DarkenedOne

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #7 on: 09/18/2011 06:03 PM »
Do you mean crewed outer solar system missions? They *are* possible with other methods whose TRL is *much* higher than this. It depends how much someone wanted to trash their home planet and pollute the rest of the solar system.


Explain how you can pollute the solar system.  Honestly at this point I do not think that humans could do that no matter how much we wanted to do so.

Offline lkm

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #8 on: 09/18/2011 07:41 PM »
If you're not focused on solely on getting some extreme ISP out of it gas core reactor rockets  can actually be a simpler solution. There is a NTRS paper on a Nuclear Vapor Thermal Reactor that could be easier to build than a new NERVA.

http://hdl.handle.net/2060/19960020451

It uses the same basic NERVA design but dispenses with complex fuel construction for fuel channels of UF4 surrounded by Hydrogen channels. This has the benefit of potentially easier refuelling and reusability, improved safety and a good ISP.

Offline jbrooks

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #9 on: 09/19/2011 01:06 AM »
If you're not focused on solely on getting some extreme ISP out of it gas core reactor rockets  can actually be a simpler solution. There is a NTRS paper on a Nuclear Vapor Thermal Reactor that could be easier to build than a new NERVA.

http://hdl.handle.net/2060/19960020451

It uses the same basic NERVA design but dispenses with complex fuel construction for fuel channels of UF4 surrounded by Hydrogen channels. This has the benefit of potentially easier refuelling and reusability, improved safety and a good ISP.

Fascinating concept - I've never seen it before. The T/W ratio of 5.0 for the C-C moderated design is higher than most realistic NERVA designs.

Here's an idea - how about an NVTR with LOX augmentation? Such a design would have a great T/W ratio and the Isp of a solid-core NTR.
« Last Edit: 09/19/2011 01:07 AM by jbrooks »

Offline 93143

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #10 on: 09/19/2011 02:39 AM »
The T/W ratio of 5.0 for the C-C moderated design is higher than most realistic NERVA designs.

The tungsten-based ones, I guess...  Graphite-based could get 7:1 or better back in the day...

Dumbo, of course, trashes any of these, and if Figure 9-9 in the original report is anything to go by, a tungsten/cermet Dumbo could potentially get a similar Isp to this NVTR...

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Here's an idea - how about an NVTR with LOX augmentation? Such a design would have a great T/W ratio and the Isp of a solid-core NTR.

Not at the same time.  You lose Isp really fast with LOX augmentation.

It is an interesting idea, though.
« Last Edit: 09/19/2011 02:54 AM by 93143 »

Offline Tass

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #11 on: 09/19/2011 08:29 AM »
Figure in the fact that increasing Isp has an exponential effect on your DV, and the benefits are even greater.

It has an exponential effect on mass ratio, not deltaV. 

Offline lkm

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #12 on: 09/19/2011 09:52 AM »
If you're not focused on solely on getting some extreme ISP out of it gas core reactor rockets  can actually be a simpler solution. There is a NTRS paper on a Nuclear Vapor Thermal Reactor that could be easier to build than a new NERVA.

http://hdl.handle.net/2060/19960020451

It uses the same basic NERVA design but dispenses with complex fuel construction for fuel channels of UF4 surrounded by Hydrogen channels. This has the benefit of potentially easier refuelling and reusability, improved safety and a good ISP.

Fascinating concept - I've never seen it before. The T/W ratio of 5.0 for the C-C moderated design is higher than most realistic NERVA designs.

Here's an idea - how about an NVTR with LOX augmentation? Such a design would have a great T/W ratio and the Isp of a solid-core NTR.

I think the geometry was kept simple and NERVA like for the sake of development cost and easier analysis but I don't see why the fuel gas channels couldn't be arrange in a helical structure with a radial gas flow for a more DUMBO like performance.

Offline jbrooks

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #13 on: 09/19/2011 10:24 AM »
The T/W ratio of 5.0 for the C-C moderated design is higher than most realistic NERVA designs.

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Here's an idea - how about an NVTR with LOX augmentation? Such a design would have a great T/W ratio and the Isp of a solid-core NTR.

Not at the same time.  You lose Isp really fast with LOX augmentation.

It is an interesting idea, though.

I realize that - the paper linked to earlier stated a range of 1000-1200 seconds for the theoretical Isp of an NVTR. Being that this is an advanced concepts thread, I'm working off of the high end.

Offline 93143

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #14 on: 09/19/2011 04:28 PM »
Fair enough - I guess it's a question of what you consider a "great" T/W ratio...

Offline jbrooks

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Re: Gaseous Core Nuclear Thermal Rocket
« Reply #15 on: 09/19/2011 08:14 PM »
Fair enough - I guess it's a question of what you consider a "great" T/W ratio...

Poor word choice on my part. (sheepish grin: ;D )

Figure in the fact that increasing Isp has an exponential effect on your DV, and the benefits are even greater.

It has an exponential effect on mass ratio, not deltaV. 

Thank you - a little brainfart there. (kicks self) Duly noted and corrected.

"It was late and I was tired..." (another sheepish grin: ;D )
« Last Edit: 09/19/2011 08:15 PM by jbrooks »

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