Fuel for Vehicles

Discuss the Traveller RPG and its many settings
keravon
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Fuel for Vehicles

Postby keravon » Fri Apr 13, 2018 12:49 pm

Hi Guys,

I'm struggling to find any info in the core rule book on Vehicle fuel. Cost and type.

Plenty of info for star ships but nothing for vehicles. Any help much appreciated.

Thanks
Condottiere
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Re: Fuel for Vehicles

Postby Condottiere » Sat Apr 14, 2018 10:12 pm

Off hand, I think it's concerned with increasing range of operations, and by implication, fuel capacity.
Reynard
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Re: Fuel for Vehicles

Postby Reynard » Sun Apr 15, 2018 2:20 am

Under Customization on page 46 they have Fuel efficiency and Fuel capacity to increase or decrease the range. They greatly simplified vehicle design by having the chassis type come with a standard motive type whose range is based on Tech Level. Whether gasoline, wood or Fusion Plus, this is how far the vehicle will go on a fill up. If you want complex, try Striker, Fire, Fusion & Steel or MegaTraveller.
AnotherDilbert
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Re: Fuel for Vehicles

Postby AnotherDilbert » Mon Apr 16, 2018 1:20 pm

keravon wrote: I'm struggling to find any info in the core rule book on Vehicle fuel. Cost and type.
I would say it depends on the world and the application.

The design system for vehicles is note very detailed, the fuel type is very much left up the Referee.

We know that with current technology we can build motor vehicles that run on various hydrocarbons (oil-derived, coal-derived, agriculture-derived), hydrogen, and batteries.

A vehicle carried on a spacecraft would likely use hydrogen or batteries, rather than difficult to source hydrocarbons.
steve98052
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Re: Fuel for Vehicles

Postby steve98052 » Tue Apr 24, 2018 10:19 pm

AnotherDilbert wrote:
Mon Apr 16, 2018 1:20 pm
. . .
A vehicle carried on a spacecraft would likely use hydrogen or batteries, rather than difficult to source hydrocarbons.
Hydrogen is more difficult to store than liquid hydrocarbons. It requires cryogenic storage, hydrides, or high pressure tanks. Hydrogen molecules are tiny, and tend to diffuse through a lot of materials that are otherwise gas-tight, and reacts with some metals; for example, it dissolves into iron and most steels. It also has a wider range of explosive mix percentages in air. In short, it requires a lot more special handling.

On the other hand, it's a lot easier to generate without biological sources, and it's much better as a fuel cell fuel.
AnotherDilbert
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Re: Fuel for Vehicles

Postby AnotherDilbert » Tue Apr 24, 2018 11:36 pm

Quite, but spacecraft already carry large amounts of hydrogen and are often equipped to routinely find and extract more. Storing LHyd seems to be a solved problem.

Refined hydrocarbons such as petrol or alcohol on the other hand would have to be sourced from an industrialised source possibly many lightyears away.
Condottiere
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Re: Fuel for Vehicles

Postby Condottiere » Wed Apr 25, 2018 5:58 am

I think originally it was battery packs.

Recharging would be easier, if possibly longer depending on the source.

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Re: Fuel for Vehicles

Postby Annatar Giftbringer » Wed Apr 25, 2018 6:44 am

Vehicle handbook has an info block on typical power plants throughout the TLs.
OrganicMechanic
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Re: Fuel for Vehicles

Postby OrganicMechanic » Sat Apr 28, 2018 1:20 pm

Good point, the vehicle handbook does not publish cost for refueling.

My homebrew rules, which seems to work for me, are

TL 3 or 4 - steam power so using wood, biomass or coal - cost to refuel vehicle is 30cr/shipping tonne
TL 5 to 7 - internal combustion so using petrochemicals, alcohol, veg oil etc. - cost to refuel vehicle is 20cr/shipping tonne
TL 8 to 10 - electric powered using batteries - cost to refuel vehicle is 15cr/shipping tonne
TL 11 upwards - probably powered by micro fusion reactor using hydrogen- cost to refuel vehicle is 10cr/shipping tonne

and by shipping tonne I mean the shipping mass of the vehicle....

for example:
- to refuel a ATV (rule book page 139), which is TL12 it wants hydrogen and is 10 tonnes shipping so will cost 100Cr to refuel fully.
- to refuel a gound car (rule book page 141), which is TL 8 I assume batteries and its 3 tonnes so that is 45Cr to refuel fully

if you have only gone half the range then you have only used half the fuel. Also you may find it difficult to obtain certain fuels on certain planets or local crisis may affect the cost and availablilty of course but thats an easy guide. It seems about right, refueling your car is about the cost of a leather jacket and cheaper than a computer so I reckon thats about right.
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Re: Fuel for Vehicles

Postby steve98052 » Tue May 01, 2018 10:04 pm

An intermediate fuel between batteries and fusion is the radioisotope thermal generator. They've been used on space probes for decades, and are idea for cases where long endurance is useful but the vehicle is too small for even the smallest fusion plant.

Of course fusion plants can be pretty small at the highest technology levels, or else there wouldn't FGMP weapons. But those are really expensive, and if you just want a ground car you might as well give it an RTG and change it out every few years.

Widespread use of RTG power supplies would explain seeing "radioactives" as a sought-after cargo on the cargo tables.

Radioactivity scares people in the real world, but presumably in the Traveller universe it seems less exotic because nuclear waste disposal is a solved problem: reprocess it if you have the technology, or export it if you don't.
heron61
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Re: Fuel for Vehicles

Postby heron61 » Thu May 03, 2018 7:15 am

One thing that's always puzzled me and that I always change is that I've always assumed that higher tech vehicles (typically TL 12+) are fusion powered, or at least everything as large or larger than a standard air raft is, and as such, even with unreasonable power requirements, it should still not have any sort of range, but should instead have a duration between required refueling and fusion reactor maintenance of somewhere between a few months and a few years. Sure, I can see a grav cycle using batteries or fuel cells, or whatever, as would all vehicles up to TL 10 or 11, and these vehicles would require fuel or charging far more frequently, but I really don't see this with mid to large sized high tech vehicles.
Condottiere
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Re: Fuel for Vehicles

Postby Condottiere » Thu May 03, 2018 8:38 am

There's some inconsistency with fusion reactors, and it's easiest to bypass it by installing batteries.

Economy of scale and fuel tank size.
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Re: Fuel for Vehicles

Postby steve98052 » Mon May 07, 2018 5:25 pm

Ultra-tech batteries have such high energy density that fusion is only needed for heavy vehicles like grav tanks. RTGs are great for long endurance but modest power requirements.
heron61
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Re: Fuel for Vehicles

Postby heron61 » Tue May 08, 2018 8:08 pm

steve98052 wrote:
Mon May 07, 2018 5:25 pm
Ultra-tech batteries have such high energy density that fusion is only needed for heavy vehicles like grav tanks. RTGs are great for long endurance but modest power requirements.
I can't find the article, but years ago I read an excellent argument about how superconducting batteries (which likely possess highest energy density possible with a battery) are limited to having an energy density of no more than an equal volume of gasoline due to magnetic stress on the material. Given that a good internal combustion engine has an efficiency of 33% and electrically powered devices have an efficiency of more like 80%, that effectively gives you, at most 2.4 times the range of gasoline, which is awesome for low power applications like personal devices, but still fairly limiting for vehicles. In contrast, small fusion reactors offer would not require additional fuel for months or years.
Condottiere
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Re: Fuel for Vehicles

Postby Condottiere » Wed May 09, 2018 9:06 pm

Solar panelling does allow recharging on the hoof.
steve98052
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Re: Fuel for Vehicles

Postby steve98052 » Fri May 11, 2018 4:54 pm

heron61 wrote:
Tue May 08, 2018 8:08 pm
. . . I read an excellent argument about how superconducting batteries (which likely possess highest energy density possible with a battery) are limited to having an energy density of no more than an equal volume of gasoline due to magnetic stress on the material. Given that a good internal combustion engine has an efficiency of 33% and electrically powered devices have an efficiency of more like 80%, that effectively gives you, at most 2.4 times the range of gasoline, which is awesome for low power applications like personal devices, but still fairly limiting for vehicles. In contrast, small fusion reactors offer would not require additional fuel for months or years.
That's a reasonable guess for the limits of batteries constrained by real physics. And some things in Traveller do try to follow real science. But there's a lot of super-science* in Traveller too, and devices like the backpack powered laser rifle are well into super-science battery territory. If we can allow for laser weapons that can get 40 or 50 shots out of a backpack battery, we can allow battery-powered vehicles with fairly long endurance too.

And as I've mentioned, RTGs are ideal for really long endurance at moderate power levels. With nuclear damper box technology (TL12), RTGs are really useful power sources. Fusion is great, but not always necessary.
heron61
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Re: Fuel for Vehicles

Postby heron61 » Fri May 11, 2018 8:04 pm

steve98052 wrote:
Fri May 11, 2018 4:54 pm
But there's a lot of super-science* in Traveller too, and devices like the backpack powered laser rifle are well into super-science battery territory. If we can allow for laser weapons that can get 40 or 50 shots out of a backpack battery, we can allow battery-powered vehicles with fairly long endurance too.
Is that actually true? I can easily see the problem if laser weapons used continuous beams, but I've always assumed they fired very short pulses. From what I've seen able to find, 10 kilojoules would be a pretty lethal laser pulse, and there are 3.6 megajoules in one kilowatt hour, and gasoline is well higher than that. Roughing out the numbers, and allowing for inefficiency and overkill. If each shot uses 72 kilojoules, then a 1 kWh/kg battery (which is definitely possible) can hold 500 shots. Honestly, this is saying to me that a laser rifle won't need a backpack to hold 100 shots, but could instead use an integral battery.
And as I've mentioned, RTGs are ideal for really long endurance at moderate power levels. With nuclear damper box technology (TL12), RTGs are really useful power sources. Fusion is great, but not always necessary.
Definitely.

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