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Old 01-18-2011, 03:12 PM   #1
vicky_molokh
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Default [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

Greetings, all!

I noticed there's a shortage of power plants below TL7. Boilers are TL7 for some reason. Fuel Cell has no RAW analogues below TL7 . . . how much endurance would a power plant based on some sort of combustible fuel have at TLs 6 and below?

Likewise, what stats should I use for the equivalent of WWI planes' propulsion, those barely exceeding a hundred mph? Would Ether Screws be a close enough fit? (They seem to provide more speed than the planes of the age had).

Thanks in advance!
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Old 01-18-2011, 03:49 PM   #2
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Default Re: [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

A TL5 Steam Engine (p. HT14) requires 250 lbs./hr. of wood and 400 lbs./hr. of water (and some amount of oxidizer without access to an atmosphere) for an 8,000-lb. engine. That implies that a Fuel Tank system would run a Steam Engine system for no more than 12 hours (depending on how much mass of oxidizer is required).

A TL6 Internal Combustion Engine (p. HT14) requires 8/3 lbs./hr. (and again, some amount of oxidizer) for a 125-lb. engine, so a Fuel Tank system would run an ICE system for no more than 48 hours.

How much oxidizer do we need? I'm going to guess a 3:1 ratio of oxidizer to combustible by mass*. That gives us 3 hours per Fuel Tank of wood† for a TL5 Steam Engine system, and 12 hours per Fuel Tank of gasoline for a TL6 ICE system. As a reality check, the TL9 MHD Turbine (p. SS20) provides two power points for 24 hours on a Fuel Tank (comparable to one power point for 48 hours), so we're not busting any TL barriers here. If I've mis-estimated the amount of oxidizer required, use a different divisor.

I don't know if the idea (or at least the production) of an oxidizer is appropriate pre-TL7 though. That might be why these aren't listed.


* That's about what the space shuttle uses. For wood and gasoline, well ... it's been a long time since high-school Chemistry, but I can guess the end products of combustion are going to be CO2 +H2O, which is about 3:1 Oxygen to Carbon+Hydrogen by atomic mass. Is two Hydrogens per Carbon about right for wood and gas? I dunno.
† Charcoal might double that endurance (p. LT27), and coal might multiply it by four (p. HT14).

Last edited by munin; 01-18-2011 at 04:15 PM.
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Old 01-18-2011, 04:16 PM   #3
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Default Re: [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

The spaceships system is really too low granularity to deal with aircraft. Realistically, you don't get the required power density for viable aircraft before mid TL 6, at which point you're basically using the same power plants as you'd use at TL 7, just with lower performance.
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Old 01-19-2011, 04:47 AM   #4
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Default Re: [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

Quote:
Originally Posted by munin View Post
A TL5 Steam Engine (p. HT14) requires 250 lbs./hr. of wood and 400 lbs./hr. of water (and some amount of oxidizer without access to an atmosphere) for an 8,000-lb. engine. That implies that a Fuel Tank system would run a Steam Engine system for no more than 12 hours (depending on how much mass of oxidizer is required).

A TL6 Internal Combustion Engine (p. HT14) requires 8/3 lbs./hr. (and again, some amount of oxidizer) for a 125-lb. engine, so a Fuel Tank system would run an ICE system for no more than 48 hours.

How much oxidizer do we need? I'm going to guess a 3:1 ratio of oxidizer to combustible by mass*. That gives us 3 hours per Fuel Tank of wood for a TL5 Steam Engine system, and 12 hours per Fuel Tank of gasoline for a TL6 ICE system. As a reality check, the TL9 MHD Turbine (p. SS20) provides two power points for 24 hours on a Fuel Tank (comparable to one power point for 48 hours), so we're not busting any TL barriers here. If I've mis-estimated the amount of oxidizer required, use a different divisor.

I don't know if the idea (or at least the production) of an oxidizer is appropriate pre-TL7 though. That might be why these aren't listed.
Oxydizer doesn't enter the equation yet.

Hmm. ICE's 12 hours per Fuel Tank (which seems to imply 3 hours for Internal Fuel) seems quite good. In fact, it matches the rate of the Fuel Cell from TL7. Why is it TL7 then?
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Old 01-19-2011, 06:05 AM   #5
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Default Re: [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

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Originally Posted by vicky_molokh View Post
Oxydizer doesn't enter the equation yet.

Hmm. ICE's 12 hours per Fuel Tank (which seems to imply 3 hours for Internal Fuel) seems quite good. In fact, it matches the rate of the Fuel Cell from TL7. Why is it TL7 then?
Would 3/4s of a system worth of TL6 ICE + generator be enough to produce a power point?
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Old 01-19-2011, 06:40 AM   #6
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Default Re: [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

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Originally Posted by Ulzgoroth View Post
Would 3/4s of a system worth of TL6 ICE + generator be enough to produce a power point?
I don't know, it seems comparable to two Passenger Seating of rowers (oars provide half the thrust of screws; screws eat a Power Point, oars eat the work of a system's worth of rowers). Do you think it should provide 1 PP per two systems and have no internal fuel? Provide 1 PP/system with no internal fuel? Or maybe provide 1 PP but consume fuel faster?
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Old 08-04-2011, 04:26 AM   #7
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Default Re: [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

Quote:
Originally Posted by munin View Post
A TL5 Steam Engine (p. HT14) requires 250 lbs./hr. of wood and 400 lbs./hr. of water (and some amount of oxidizer without access to an atmosphere) for an 8,000-lb. engine. That implies that a Fuel Tank system would run a Steam Engine system for no more than 12 hours (depending on how much mass of oxidizer is required).

...
Charcoal might double that endurance (p. LT27), and coal might multiply it by four (p. HT14).
Old thread, but I recently got re-interested in making my just this side of reality dirigible...

You left out one important thing. What SM ship would make an 8000 lb engine roughly one system using Spaceships?
Using 650 lbs per hour for 12 hours gives 7800 lbs which is between SM 5 and SM 6 fuel tanks of 3000 lbs and 10,000 lbs respectively.
Assuming charcoal has double the energy density of wood doesn't affect the need for water, so it wouldn't double the endurance.
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Old 08-04-2011, 05:40 AM   #8
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Default Re: [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

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Originally Posted by munin View Post
A TL5 Steam Engine (p. HT14) requires 250 lbs./hr. of wood and 400 lbs./hr. of water...
At some point it has to be worth installing a condenser and a radiator to cut down the water consumption.

Quote:
How much oxidizer do we need? I'm going to guess a 3:1 ratio of oxidizer to combustible by mass*.
The equation for burning wood is going to be something like
n.{C6.H12.O6 + 6(O2)} —> n.{6.(CO2) + 6.(H2O)}
Which suggests about 192 parts of oxygen to 180 parts of cellulose by mass, or 16 to 15 (that's 1.07)

Burning charcoal is more like:
C + O2 —> C.O2
Which implies 8 of oxygen to 3 parts of fuel by mass. (2.67)

And gasoline is something like:
2.(C8.H18) + 25.(O2) —> 16.(C.O2) + 18.(H2.O)
Which implies 800 oxygen to 228 fuel by mass. (3.51)
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Old 08-04-2011, 05:43 AM   #9
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Default Re: [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

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Originally Posted by Flyndaran View Post
8000 lb engine roughly one system using Spaceships?
8000lb is 4 US tons. One system is 1/20 of a ship. So we're looking at an 80-ton ship. That's about SM+6.
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Old 08-04-2011, 07:07 AM   #10
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Default Re: [Spaceships] Non-TL^ Power Plants and air propulsion below TL7?

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Originally Posted by Brett View Post
At some point it has to be worth installing a condenser and a radiator to cut down the water consumption.

...
How efficient could such a thing(s) be? That water consumption really limits airship endurance.
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