2300 Heat

[rgrove0172]

It seems Star Cruiser missed the entire Heat issue. Ive seen one set of house rules addressing the problem. (Radiators, sinks and the effects if you dont have enough on your signature and more) Anyone else have a set they would like to offer up or a comment on the subject?

Is it a glaring goof? An option for Tech Nuts? Was it assumed a non issue but some other 2300AD technology Im just not considering?

 

[shaunhilburn]

It seems Star Cruiser missed the entire Heat issue. Ive seen one set of house rules addressing the problem. (Radiators, sinks and the effects if you dont have enough on your signature and more) Anyone else have a set they would like to offer up or a comment on the subject?

Is it a glaring goof? An option for Tech Nuts? Was it assumed a non issue but some other 2300AD technology Im just not considering?

Star Cruiser has Basic, Extensive, and Advanced hull masking radiators. They're optional but should be required. This was a *big* oversight, probably because GDW was still thinking of spacecraft in terms of Traveller.

The temperature per megawatt of Basic hull masking radiators works out to something like 1,400 - 1,500 K, hot enough to glow a bright yellowish orange. Extensive and Advanced hull masking are a few hundred K cooler.

You need enough radiator to handle the rated output/conversion efficiency; a closed-cycle powerplant rated @ 100 MW and 35% conversion efficiency generates 186 MW of waste heat, so you need radiators capable of handling 286 MW. Open-cycle MHD generators and fuel cells exhaust most if not all of the waste heat overboard, so they only need radiators to handle the rated powerplant output.

 

[BMonnery]

Yes, it is a real problem.

Now, the entire hull will of course radiate, assuming it isn't covered with something else.

Take a Kennedy and ignore the masking. It has about 2,500 m2 of hull area not mounting a weapon or similar, and at least 150 MW/60% (250 MWt) of heat to dump (GDW gives MHDs 60% efficiency, and the fuser is essentially a closed loop MHD with a fusion kettle).

Temperature of hull = 1,152 K = 879oC

Now, if the ship wanted to maintain a sustainable hull temperature of 293 K by ambient heating (i.e. maintain the ship at 20oC) then the engine would be operating at 1 MWt.

The easiest fix is to making "masking" mandatory for nuke boats. If we handwave and assume 60% efficiencies, operating temperatures are:

Basic: 1,557 K
Intermediate: 1,309 K
Advanced: 1,250 K

If we stick them on pylons our effective area doubles, and so temperature drops 16%.

In all these cases the working fluid would need to be molten sodium or lithium, and quite a lot of it, but the mass would be included in the reactor.

 

[aramis]

Given GDW's rather low assumptions for fusion, can we not simply assume that the requisite radiators are already included in the drive tonnages? Sure, we should be noting the rather impressive red glow...

 

[BMonnery]

Given GDW's rather low assumptions for fusion, can we not simply assume that the requisite radiators are already included in the drive tonnages? Sure, we should be noting the rather impressive red glow...

We need a surface area.

One option would be the use of Lead-Bismuth alloy. This would approximately fit the area aft, and would produce the blue-white glow seen at the back of the Bassompierre.

In fact that works. In imposes the following limitations in section size for the reactor assuming the rear is one big radiator:

150 MW: 21m diameter
200 MW: 24m diameter
250 MW: 27m diameter
300 MW: 30m diameter
415 MW: 36m diameter (causing some complications for the Richelieu).

 

[Kaye]

So they're all radiators now!?
That would explain all that artwork that has supposedly stutterwarp driven ships toting those impressive plumes at their rear...

 

[BMonnery]

So they're all radiators now!?
That would explain all that artwork that has supposedly stutterwarp driven ships toting those impressive plumes at their rear...

Well, that's more to do with the opening scene of Star Wars, but we can make it fit. Rather have a thousand tons of eutetic Pb-Bi sloshing around than molten lithium any day

 

[shaunhilburn]

We need a surface area.

One option would be the use of Lead-Bismuth alloy. This would approximately fit the area aft, and would produce the blue-white glow seen at the back of the Bassompierre.

In fact that works. In imposes the following limitations in section size for the reactor assuming the rear is one big radiator:

150 MW: 21m diameter
200 MW: 24m diameter
250 MW: 27m diameter
300 MW: 30m diameter
415 MW: 36m diameter (causing some complications for the Richelieu).

That big hole at the back? The problem with tubular radiators is that the inside surface radiates back into itself, unless some fluid stream carries the heat overboard.

 

[BMonnery]

That big hole at the back? The problem with tubular radiators is that the inside surface radiates back into itself, unless some fluid stream carries the heat overboard.

I was basically modelling the rear "end cap" as a single thermal radiator. With Pb-Bi I have enough "wiggle room" to have hot spots (i.e. the Star Wars "engines") since they can be heated to about 1,900 K without huge issue beyond a 1,900 K fluid.

 

[Kaye]

Well, that's more to do with the opening scene of Star Wars, but we can make it fit. Rather have a thousand tons of eutetic Pb-Bi sloshing around than molten lithium any day

Well, I think we all understand here that Star Wars did more harm than good to hard sci fi.
I thing I liked about Star Wars though was that -apart from the technicalities being ridiculous- it showed space flight being a rather regular mode of travel. It worked for and was an integral part of the story line. Space flight was a means and not an end. One gripe I have with 2300AD is that the whole traveling through space -and especially the interface! - takes a lot of effort. It distorts gameplay.

I wholly subscribe to the notion that ships, their workings and details should be well prepared OUTSIDE gameplay! Tinkering with them is fun as long as no PC's are waiting... :nonono:

(Wasn't a lead-bismuth alloy used for lettering? It can be molten in a school classroom ISTR; does it contain enough energy to effectively radiate the energy from a fusion reactor into a vacuum?)

 

[BMonnery]

Well, I think we all understand here that Star Wars did more harm than good to hard sci fi.
I thing I liked about Star Wars though was that -apart from the technicalities being ridiculous- it showed space flight being a rather regular mode of travel. It worked for and was an integral part of the story line. Space flight was a means and not an end. One gripe I have with 2300AD is that the whole traveling through space -and especially the interface! - takes a lot of effort. It distorts gameplay.

2300ad was never a world hopping Travelleresque universe.

However, even using a corrected (increased) fuel:mass ratio for lift it's difficult to justify cost of lift (which is pg 48 1st edition PG for the person that asked). Fuel on the ground is cheaper than Lv100/ton in orbit (typically) and I think dropping a zero is reasonable. The cost to orbit via spaceplane is still Lv300 which is proportional to transatmospheric transit (Lv25 per 100 km!).

(Wasn't a lead-bismuth alloy used for lettering? It can be molten in a school classroom ISTR; does it contain enough energy to effectively radiate the energy from a fusion reactor into a vacuum?)

Probably tin-bismuth. Pb-Bi is liquid upto a bit over 1,700 oC, which is hot enough to get radiators down to "Star Wars" sizes.