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 Post subject: Fission reactors
PostPosted: Sun Oct 18, 2015 12:02 am 
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Joined: Sat Sep 01, 2012 2:44 pm
Posts: 187
Location: Colorado
I’m researching power plants for a home brew ship and vehicle design sequence. I’m looking at TL10 thru 12 (it’s for a variant 2300 setting) and am happy taking some liberties with the numbers but I’d like to have some semblance of believability.

Fission reactors are first up:

I started looking at naval reactors as it seemed they would present the closest facsimile for a starship based reactor, they’re built to be self contained and as I understand it, to a higher degree of engineering than commercial reactors as they’re operating in hostile environments underwater and in combat!

From FAS I found sizes of the reactor vessel for a number of older US naval ships. From the image I can see what’s probably inside the reactor vessel but I don’t know what else is needed to generate power (turbines, generators and stuff like that) and most importantly, it’s volume and mass.

Question 1, what’s an approximate volume and mass for the stuff not in the reactor vessel?

Wikipedia lists several others but the information isn’t up to date or complete as I assume that the current reactors are classified.

Question 2, What are the volumes and masses for the more recent US naval reactor vessels?

The reactors were rated by what I believe to be thermal output and then a SHP rating/number of shafts. I converted SHP to MW to make it a comparison easier (if indeed it’s even valid). I don’t know what their electrical output is, I assume that would be proportionate to their thermal out put but I’m not sure if it is or at what ratio.

Question 3, what’s the electrical output of the US naval reactors?

Question 4, is the electrical output likely a percentage of it’s thermal output and will it increase as more efficient (higher tech level) models are designed?

I then started looking for small reactors, the intention to get an idea of minimum volumes at different tech levels and found this and this. Wiki gave me the stats for the mPower reactor, hopefully they’re about right, a lot smaller than the naval reactors and with the Babcock and Wilcox it would appear to have a similar thermal output and lists it’s electrical output to a 1960s naval model, it's not an apple and apple comparison tho as I don't know the peripheral machines for both and what's actually in the naval vessel that the numbers refer to. Now in part that’s the advancement of technology, partly not being built “mil spec” and partly cos I don’t know what peripheral machinery I’m missing.

Question 5, how do these reactors compare to the kind the USN uses? Are they as reliable and efficient?

Question 6, are there other things I should be looking at?


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 Post subject: Re: Fission reactors
PostPosted: Mon Oct 19, 2015 1:04 pm 
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Joined: Sun Sep 07, 2008 12:06 am
Posts: 360
Have you checked the Atomic Rocket pages?

I remember a (TRITON: A TRImodal capable, Thrust Optimized, Nuclear Propulsion and Power System for Advanced Space Missions) that had some data on size and mass and power output.

A SMALL MODULAR REACTOR may have parametric data on size and weight for a complete system that could help (check the references at the bottom).

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Last edited by atpollard on Mon Oct 19, 2015 2:47 pm, edited 1 time in total.

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 Post subject: Re: Fission reactors
PostPosted: Mon Oct 19, 2015 2:06 pm 
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Joined: Tue Jul 08, 2008 8:42 pm
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Location: Texas, USA
Unfortunately, the vast majority of what you are asking is very classified. I was in the Nuclear Navy in the 80's and I don't feel comfortable giving out that info from subs back then, let alone anything more modern.

The GENERAL principle is a two-system steam cycle.

The PRIMARY system is the water going through the reactor to cool it and keep the reaction going. Water is wonderful in that it can do both. The water goes out of the reactor vessel, through a pump and into a Steam Generator, where it is cooled, then goes back into the reactor to be reheated.

The SECONDARY system is a more traditional steam-turbine cycle. The water goes into the Steam Generator where the heat of the reactor water boils it. The high pressure steam then goes into a Steam turbine where it produces work (turning the main propeller) or electricity (by turning an electric generator). The steam that comes out is low pressure and goes into a Condenser, where it is turned back into low-pressure water (sea water cools this condenser on subs). The low pressure water then goes to a Pump, where it becomes high-pressure water, which goes back into the Steam Generator.

So you have two closed systems that move the heat from the reactor to make work/electricity. The reactor water is radioactive, so that is why you don't have it touch your steam generators (which is where people are). The entire Primary system and the Steam Generator, are within the Reactor Compartment, behind heavy shielding. The rest of the Secondary system is out in the engine room where people work.

For a Spaceship, there needs to be a way to replace the sea water cooling in the Condenser with something else. You need a heat dump. Most designs that I have seen that are not "magically technological" use Radiator Fins which radiate the heat away into space. This is not very efficient, so the fins have to be HUGE, but it works. Most SciFi games tend to gloss over this part.

Modern US submarine reactors are rated in MW of power, but again, that info is classified and I don't feel comfortable using a number, but something between 10 MW and 200 MW wouldn't be unreasonable. The vast majority of that power is needed for propulsion, the electric generators produce hundreds of KW of power, but not a lot more.

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 Post subject: Re: Fission reactors
PostPosted: Mon Oct 19, 2015 5:42 pm 
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Joined: Sat Sep 01, 2012 2:44 pm
Posts: 187
Location: Colorado
Richard,

I was very much hoping that you would respond and I understand your position!

I've been assembling numbers from TNE's FF&S and 2300ad and comparing them as best I can with the available numbers for actual reactors. I'm trying to boil it down to an output expressed as MW/metre^3. It's a gross simplification but the object is to add mass and energy requirement back to ships and vehicles.

If and it's a very big if, the volume of the reactor vessel listed in the links above is comparable to the volumes in FF&S and 2300ad then they're both off by order of magnitudes!

I realise it's a big if and I am unlikely to find the numbers to be able to compare. I need to add a dash of hand wavium which is to be expected. Given that this is for a setting based in 2350, I can pluck numbers from the ether but I wanted to try and base them on figures rooted in reality and where we might be at in the future.

The waste heat dump is an interesting conundrum which might be the death knell for the arguments for stealth in space. Phavoc reported a current day potential resolution over on the Mongoose boards for converting heat into electricity but he didn't link it as far as I can tell. Who knows? :)

Arthur, thanks for the links to Atomic Rocket, I've been reading there but not on this topic. The Rocketpunk Manifesto has been helpful too!


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 Post subject: Re: Fission reactors
PostPosted: Mon Oct 19, 2015 5:45 pm 
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Joined: Mon Dec 02, 2013 1:43 pm
Posts: 321
Location: Queens, NY
Hiro, this might be a tiny bit of sidetracking, but have you ever checked out EABA, and particularly the supplement "Stuff!"?

If you really want to get your gearhead hat on, that's a great place to go. The setting/supplement for EABA, "Fires of Heaven", has a lot of 2300-ish ideas in it that you could mine for your ship designs.

If you don't mind a GURPS level of crunch, it can be really fun. If not, steer clear. :)


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 Post subject: Re: Fission reactors
PostPosted: Mon Oct 19, 2015 5:50 pm 
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Joined: Sat Sep 01, 2012 2:44 pm
Posts: 187
Location: Colorado
Matt

I have EABA, Stuff, Fires of Heaven and my bible, Guns Guns Guns!

I'm not sure what it is about EABA but I've never really got into it. That makes no sense because as you say, it is right up my street. I think my biggest problem is no one I play with even knows about it so I'm rooting the setting I'm working on in 2300 and MgT (tho its getting further and further from both)

Maybe I just have to polish my selling skills and get my players interested?

(Tho to be honest, I'm really enjoying putting my own thing together)

Tim


Last edited by hiro on Mon Oct 19, 2015 10:45 pm, edited 1 time in total.

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 Post subject: Re: Fission reactors
PostPosted: Mon Oct 19, 2015 5:58 pm 
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Joined: Mon Dec 02, 2013 1:43 pm
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Location: Queens, NY
I hear you. Nobody I know plays EABA either.


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 Post subject: Re: Fission reactors
PostPosted: Sat Oct 24, 2015 7:55 pm 
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Sorry, I think the latest posts are missing from here now - I tried to update the forum software and it didn't work, so I've got back to the last database backup which was from last week!

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