Small ship universe

[Dragoner]

I did the calc's for power generation and consumption a long time ago (helped being in engineering school) and was amazed. The 28 day endurance I can wave away as life support and food; other stuff, not so much. It's ok, I like CT the best because it is fluff basically, and doesn't try to hide it behind nonsense like later editions did.

 

[rancke]

No, actually, I like the Classic game. I would not be using it as an example of a good role-playing game for my game design class if I did not. It is easier for students to get a handle on the D&D, as it deals with material that they see or can extrapolate from in real life. There are problems, but such is the nature of gaming. Given my background, I think that I might notice more problems than other people.

I don't want to drive you away; a fresh perspective is always welcome. But you may want to consider that when people have been discussing these things for 30 years, even those who are slower and less well educated than you have probably had time to spot a lot of those problems.

Dragoner was referring to the fact that the Traveller community has been aware of the various problems with the fuel consumption rules for a quarter of a century.


Hans

 

[mike wightman]

The following material is taken from The Effects of Nuclear Weapons, Dept. of Army Pamphlet 50-3, March 1977. Said document is an official US government publication and is therefore in the public domain and copyright free.

Which no doubt has pictures for the hard of thinking

More seriously - most of us learned to do such calculations in physics class.

I understand that fuel for power plants in Traveller is Liquid Hydrogen, not Liquid Deuterium, but all that is going to do is increase your energy yield per unit mass from the fusion of hydrogen into deuterium. However, for the purpose of the following discussion, I will use the deuterium energy value.

I think you may need to look up the US Army guide to fusion reactions for dummies...

or just go do some basic research into fusion reactions on the interweb and you will spot your own errors.

A standard 200 ton Free Trader uses 10 metric tons or 10,000 kilograms of liquid hydrogen for its power plant every 28 days. That means an average fuel consumption of 14.88 kilograms per hour, or 14,880 grams per hour. Now if you assume that 57 grams of liquid H will yield 3 X 10 to the 6th kilowatt-hours (that assumes your fusion reaction is equal to 0.86 that of fission, the actual figure is 0.9475, so this is quite conservative), or 3 X 10 to the 3rd Megawatt-hours, or 3 Gigawatt-hour of power, the the fusion yield of the power plant is going to be 783 Gigawatts of power per hour on the average. If you are not using that energy, which is quite a lot, for maneuvering your Free Trader, what is the ship using it for?

And what is the efficiency of your reactor? 100% fusion?

As for what it uses it for - no idea. Once you enter the realm of late HG/MT then reactionless maneuver drives are the canonical explanation - some sort of warp bubble would be a better model for a reactionless drive and energy will be needed to maintain the bubble even if you are not moving. But as written - no idea.

In Thrust into Space, by Maxwell Hunter, he calculates that it takes 4 kilowatt-hours of power to place 1 pound of mass into Earth orbit. That equates to 1.764 Gigawatt-hours to put a 200 metric ton mass into Earth Orbit. Your power plant is producing, on the average, 443.9 times the power needed to place a 200 metric ton Free Trader into Earth Orbit.

You really don't need to quote authors and books, most of us did these calculations in physics class...

Now, if you are getting ready to jump, then your power plant is going to use 20 metric tons, or 20,000 kilograms of fuel in a very short time. Twenty metric tons of liquid hydrogen will supply 1,052,631 Gigawatt-hours of power. To put this in context, the US in 2008 used 4,401,698 Gigawatt-hours of power. You also have 20 metric tons, essentially, of extremely hot Helium plasma to get rid of in some manner.

It'll be mostly hydrogen plasma with a few fusion products in it - efficiency remember

The MegaTraveller Imperial Encyclopedia, on 81, lists the power plant output for a 200 ton Free Trader at 990 Megawatt-hours. Based on the data from Thrust into Space, mentioned earlier, that would be sufficient to place a 200 ton Free Trader into Earth orbit in 2 hours. However, based on the fuel consumption of 14.88 kilograms per hour, the power plant is using only about 0.126% of the potential energy of the fuel if complete fusion takes place. That does leaves you with 14.88 kilograms of extremely hot Helium plasma to dispose of in some manner. If you actually need Terawatts of power to make a jump, that less than a Gigawatt power plant is going to take a long time to generate that much power.

Bingo - there is no complete fusion - it's physically impossible. Read the description of the jump drive in Starship operators Manual, or even Marc Miller's jumpspace article. Part of the jump drive is a fast fusion high yield reactor.

If you are sitting on a planet, with a D or E class starport, which I would assume that a Free Trader would do on a regular basis, for what exactly are you using those 990 Megawatts, going with the MegaTraveller reference? A 729 Gross Register Ton former US Coast Guard buoy tender, which would equate to 153 displacement tons in Traveller uses two 170 Kilowatt ship service generators for all of its power needs, to include A/C, full ship lighting (using incandescent lights for the most part), electronics and computers, galley, etc. It actually only needs one, but has to have two for a backup. A 1945 aircraft carrier was requiring somewhere between 5 and 10 Megawatts of power for full operation. That would be roughly a 7500 ton ship under Traveller's displacement ton rules.

Again, if the maneuver drive is not consuming power from the power plant, where is all of that power going?

I agree with your question completely =)

 

[BlackBat242]

Your power plant is either extremely inefficient, or your endurance should be not 28 days, but more like 28,000 days assuming 100% fuel burn efficiency, or say 2800 days, assuming a 10% efficiency, and an average energy consumption of 783 Megawatts per hour.

So, one fuel load lasts one TL7 lifetime (from birth to average death due to aging: 76 years, 7 months, 28 days)?

http://www.youtube.com/watch?v=OBEB7EfkDII

60 years, 2 months, 24 days

 

[Carlobrand]

...A standard 200 ton Free Trader uses 10 metric tons or 10,000 kilograms of liquid hydrogen for its power plant every 28 days. That means an average fuel consumption of 14.88 kilograms per hour, or 14,880 grams per hour. Now if you assume that 57 grams of liquid H will yield 3 X 10 to the 6th kilowatt-hours (that assumes your fusion reaction is equal to 0.86 that of fission, the actual figure is 0.9475, so this is quite conservative), or 3 X 10 to the 3rd Megawatt-hours, or 3 Gigawatt-hour of power, the the fusion yield of the power plant is going to be 783 Gigawatts of power per hour on the average. ...

This Cornell site puts the energy from fusion at 3.4x10^8 joules per gram...

http://www.geo.cornell.edu/eas/energy/research_front_page/nuclear_fusion.html

... which translates as 94.445 MwH. That's a little under twice your proposed energy release, but of course that assumes you get 100% usable energy at no energy cost. Same site says generating the reaction requires bringing the fuel to 100 million degrees centigrade while keeping it confined. I don't know how much energy that takes - presumably that requires a fair chunk of that 94.445 MwH.

Question on the floor: optimistically, how much energy does it take to bring that gram of hydrogen to fusion, assuming we have the materials and technology to make it fuse at 100%? How much of that 94.445 MwH will be left for our own use? And, realistically, how much of that left-over energy can we grab, and how much would be lost to various unavoidable inefficiencies? (I understand there are some physical laws that apply.)

 

[aramis]

last data I saw, the navy's current program started with 102% of recovered energy being spent on confinement and initiation. 2% loss. Once the Navy reupped the funding, it went under blackout.

 

[BytePro]

Yeah, did the theoretical calculations for Traveller fusion when I was .. 12.

Here are a few generalized simple 'equations' to ponder:

Fusion in the universe = gravity.

Motion in the universe = gravity.

Handwave in Traveller = gravitics!​

As to heat (entropy/2nd law): starships are only 'mostly closed' systems while travelling and it would be silly to consider future energy conversion efficiency as not much advanced over atmospheric steam engine tech.

CT didn't use real world energy units - thankfully. And heat was ignored - thankfully. So, IMTUs, power plants include energy capacitors (as supported in HG) as well as 'heat trap cans' - the majority of the PP is infact not the reactor and plumbing. High efficiency thermal to electric conversion dumps converted energy into caps, and the rest into the 'heat cans' - however, after a few weeks of maneuvering (PP working), the capacity to do so is exceeded. Thus helping to address the 'just accelerate to past some %c or FTL' velocity using the gravitic M-Drives issue.

['Cans' store heat in such a way that their radiated heat is minimal, but enough that they are still utilized for life support, and, over the course of a trip they tend to exceed their thermal insulation and life support regulation and begin heating the ship to uncomfortable levels - especially with lots of PP usage (- all RP, no rule mechanics for this).

Cans may be ejected from a ship - they are located such that they are also used for thermal protection of the hull ('heat pipes' were applicable). They are designed to extend from ship exteriors to 'dump heat' into landing pads, heat hull when atmo didn't and also serve to melt ice for wilderness refueling. Starports have 'thermal charges' incorporated into dock fees (though they generally use the heat for profit related activities such as heating domes, melting ice, or converting to electricity via more efficient means, of course). There is also the issue of electrical discharge from the potential difference between ships and pads ... but that is another issue.]

 

[Ishmael]

IMTU...

Fusion plants are aneutronic, with direct conversion to electricity. Today's experiments can do the conversion part with 86% efficiency, so figuring much better efficiencies at higher tech levels is easy.
Fusion plants that release most of their energies via neutrons have to rely on thermal conversion methods which peak at Carnot efficiencies.

Nothing says that the fuel in Traveller is used entirely, and some editions ( FFS1 and SOM, for example ) specifically state that the hydrogen is an abstraction to cover many things, especially coolant. FFS1 even says that energy conversion is via steam turbines ( thermal conversion ).

Thus, IMTU, most of the 'fuel' is actually coolant for either regenerative and/or dump cooling. The reaction uses only a very tiny fraction of the entire 'fuel tankage'. But without the coolant, the reactor slags.
This lets me not worry too much about the problems with fusion fuel use and heat management.

IMTU, I also have explosive pumped flux compression generators charging jump caps or charging through solar ( takes a fairly long time....) or other electrical generation methods.

 

[Jame]

So, one fuel load lasts one TL7 lifetime (from birth to average death due to aging: 76 years, 7 months, 28 days)?

http://www.youtube.com/watch?v=OBEB7EfkDII

60 years, 2 months, 24 days

Yes, and that doesn't assume increase at higher TLs. Such as 9, 11, 15...

 

[Carlobrand]

Uhh, what does that have to do with the price of tea in China?

 

[Khan Trav]

Can you say spam?

 

[Carlobrand]

Spam, spam, eggs, spam, bacon, spam, and spam.

 

[77topaz]

Uhh, what does that have to do with the price of tea in China?

All the tea in China has been estimated to be worth 1.5 billion American dollars.

 

[aramis]

Yes, and that doesn't assume increase at higher TLs. Such as 9, 11, 15...

Uhh, what does that have to do with the price of tea in China?

breakpoints for PP fuel efficiency in striker, MT, TNE, & T4

 

[Carlobrand]

breakpoints for PP fuel efficiency in striker, MT, TNE, & T4

Might I point out for the record that my response was to a post that, presumably for violating site rules, no longer exists?

Thank you for that, by the way. Better a bit of confusion than having people think they can come in here and pull such ridiculous shenanigans.

 

[Timerover51]

I am working on a modification of the ship design process for Classic Traveler, trying to get some distinction between the design of military ships and civilian vessels.

Presently, I am experimenting with a flat 10 tons of fuel per jump number, with the variable fuel being used for maneuvering. Power plant usage while in jump space and planet-side is inconsequential, and minimal costs while in orbit. Military ships, scouts, and Free Trader will carry sufficient fuel for two consecutive jumps without refueling, while civilian ships on regular runs will only have sufficient jump fuel for one jump.

Military hulls cost the 100K credits per ton, civilian hulls cost 10K credits per ton. Military drives and power plants have half the mass but cost the twice as much, with some scaling. Maintenance costs for military are 10% of the cost of the ship per year based on the entire ship cost. Maintenance costs for civilian ships are 10% per year of the cost of the drives and power plant, being the most critical components. If a civilian ship is built to military standards, the maintenance costs are the same as the military.

There are standard ship hulls, but engineering spaces can be customized without extra cost. Cargo is carried on the basis of 5 tons mass per 1 Traveller displacement ton, which works out to about 10 pounds per cubic foot of volume, or about what is assumed for air freight shipments. Civilian ships require manned turrets, military ships may be unmanned. Military bridge and sensor suites cost 10 time civilian costs, reflecting a much higher level of coverage.

Hull size will be limited to 5000 tons, with civilian ships limited to a maximum of 4 to 6 gun mounts, at the rate of one gun mount per 100 tons of hull.

The idea is to make military ships considerably more distinct that civilian ships and also much better armed.

Still working on ideas for computer systems.

 

[atpollard]

Looking at the small weapon mounts on helicopters and a picture of those dogs with all of the folds of skin gave me an idea for increasing the hardpoints on a (military) ship by bending without rewriting the existing rules.

First an observation on geometry … a short, squat 1000 dTon ship (like a cube) will have the same volume but less surface area than a long, slender 1000 dTon ship (like a fence post). TNE exploited this relationship by limiting many components based on surface area rather than volume, and I wanted to find a CT way to incorporate this.

Now back to the wrinkly dog. Imagine building a 1000 dTon cube hull and fitting it with hard points. Now imaging peeling off the skin of the ship and wrapping it around 500 dTons of internal ship components. The new ship could look like a cube with folds of extra ‘hull’ like the weapon mount ‘wings’ on a helicopter or the skin could be cut and stitched to cover a long slender hull. In Classic Traveller ship design terms, this would be represented best by ‘purchasing’ a 1000 dTon hull and ‘getting’ only 500 dTons of volume … a 500 dTon ship with 10 hardpoints.
[Drives and such would be purchased and designed for a 500 dTon ship.]

So – good or bad - that was my idea.

 

[DangerousThing]

IMTU...

Fusion plants are aneutronic, with direct conversion to electricity. Today's experiments can do the conversion part with 86% efficiency, so figuring much better efficiencies at higher tech levels is easy.
Fusion plants that release most of their energies via neutrons have to rely on thermal conversion methods which peak at Carnot efficiencies..

IMTU I power my ships with extremely high efficiency batteries. Ones that store their energy in the particle spin rather than chemical reactions. Ship batteries are more expensive per unit volume than normal batteries like the one that powers you air/raft for a year.

 

[77topaz]

Looking at the small weapon mounts on helicopters and a picture of those dogs with all of the folds of skin gave me an idea for increasing the hardpoints on a (military) ship by bending without rewriting the existing rules.

First an observation on geometry … a short, squat 1000 dTon ship (like a cube) will have the same volume but less surface area than a long, slender 1000 dTon ship (like a fence post). TNE exploited this relationship by limiting many components based on surface area rather than volume, and I wanted to find a CT way to incorporate this.

Now back to the wrinkly dog. Imagine building a 1000 dTon cube hull and fitting it with hard points. Now imaging peeling off the skin of the ship and wrapping it around 500 dTons of internal ship components. The new ship could look like a cube with folds of extra ‘hull’ like the weapon mount ‘wings’ on a helicopter or the skin could be cut and stitched to cover a long slender hull. In Classic Traveller ship design terms, this would be represented best by ‘purchasing’ a 1000 dTon hull and ‘getting’ only 500 dTons of volume … a 500 dTon ship with 10 hardpoints.
[Drives and such would be purchased and designed for a 500 dTon ship.]

So – good or bad - that was my idea.

That would be a way to get more hardpoints with the same amount of volume (higher hardpoint-to-volume ratio), but some hardpoints inside a "fold" might be largely blocked and relatively useless, and a ship with a wrinkly shape would not be very streamlined.

 

[Darkwing]

Personally, I just figure military vessels can mount as many hardpoints as desired. They still need enough power, fire control, and volume. But if I can draw the deck plans for it, I assume it can be done. But then I also make sure to add galleys, mess decks, fan rooms, etc.

On the Big Ship vs. Small Ship universe question, I think, like today's military, we need big ships, but depend too much on them. There should be big ships. There should also be small ships. In real life, for example, Frigates are too big for what they provide, and cost too much. We need at least another carrier or three, for everything the gov't wants us to do, but DDGs can do everything CGs do, and the LCS is too small for everything the navy wants it to do. So I figure we need a core of big carriers, some small carriers (convert LHAs/LHDs to CVEs), scrap all old amphibs, replace with LPDs. Scrap CGs. Build some more DDGs to replace the bigger, more expensive CGs. Scrap the white elephant FFGs, replace them with a whole bunch of cheap corvettes, and put the LCS on the back burner until it either phases into obsolescence or becomes actually useful, whichever comes first. We need hulls able to be places more than we need omni-capable ships.
So, in Traveller, have some huge carriers and BBs in the active fleet, some capital escorts in similar masses, then a whole slew of ships in the junior weight class of 1k-10k semi-capital types (Figs, cans, cruisers), then the small escorts, like the Gazelle, Fiery, etc. by the bushel. For the big-stick between star-nations, There's the force-projection of the really big ships, but only a handful of them, and there's the support for them, in their weight class. Then there's the more available big-stick for pirates and pocket kingdoms of your top-end small ships (Kinunir, Sydkai, etc up to 10k dtons), then there's your widespread presence with the little ships - your big stick for PCs getting out of hand.