Ship Drive Sizes

[OIT]

OK, so, in general, I like MGT. However, I'm digging a little more into ship design and the following bits about drives stick out:

Traveller Core Rulebook, pg 107, states, “Any specific drive will be less efficient as the tonnage it must drive increases.”

and

MGT High Guard, pg 63, states, “Hulls vary in their requirements for drives and power plants based on tonnage. Any specific drive will be less efficient as the tonnage it must drive increases.”

Yet the following examples illustrate the opposite:

Shuttle(90tons): Jump NA, Thrust 3 = 6.67%, PP 3 = 5%
Far Trader(200tons): Jump 2 = 7.5%, Thrust 1 = 1%, PP 2 = 3.5%
Light Carrier(30ktons): Jump 4 = 5%, Thrust 2 = 3.25%, PP 4 = 3.75%

In all cases, the smaller ships require more space, percentage-wise, than the capital ship, but for a much lower level of performance.

Also consider:

Free Trader(200tons): Jump 1 = 5%, Thrust 1 = 1%, PP 1 = 2%
Superfreighter (100ktons): Jump 4 = 5%, Thrust 1 = 1%, PP 4 = 3%

So the free trader gives up nearly as much space, as a percentage, as the superfreighter for a much, much lower level of performance.

Even within the core ruleset:

Far Trader(200tons): Jump 2 = 7.5%, Thrust 1 = 1%, PP 2 = 3.5%
Heavy Freighter(1kton): Jump 2 = 4.5%, Thrust 1 = 0.9%, PP 2 = 2.5%

Rather than having small ships perform better, the rules actually seem to penalize smaller craft.

Is there a piece of errata I missed? Is there a game design reason why the stated methodology in the verbal parts of the ship design rules do not match the actual nuts-and-bolts rules? Has anyone else noticed this?

 

[cajon5]

Traveller Core Rulebook, pg 107, states, “Any specific drive will be less efficient as the tonnage it must drive increases.”

I think this is just a queston of wording. Any given drive, say Jump Drive A, will be less effective when put in a larger hull. Jump Drive A produces Jump 2 in a 100 ton hull, but only Jump 1 in a 200 ton hull. It has no effect in a 300 ton hull.

Likewise, under High Guard rules, 50 tons of jump drive produces lower jump numbers as the hull it is in gets larger.

 

[robject]

Cajon's explanation sounds right to me. Even back in Book 2 days, a larger ship had less percentage devoted to drive volumes.

 

[Peter Schutze]

I also think you are looking at it the wrong way around .... take it literally as written and it makes perfect sense in newtonian physics:

any drive (size) will be less efficient if it is pushing a larger mass

same as a car .... my 1.4 litre engine is fine in a subcompact, barely functional in a typical SUV and totally useless on its own for trying to move a semi

or in traveller terms: this type B j-drive gives my 100t scout J-2 but only gives a 200t far trader jump-1 and doesnt get the 600t liner anywhere at all

 

[atpollard]

Personally, I have no problem with the design system, but agree that “efficiency” may be a bad choice of words. The Performance of a Maneuver Drive decreases as the Hull Size increases, but the EFFICIENCY seems to hold constant.

For example, MD-C appears to supply 600 Gee-Tons of force:
MD-C installed in a 100 ton hull will provide 6 Gees of acceleration (6 Gees x 100 tons = 600 Gee-Tons). MD-C installed in a 200 ton hull will provide 3 Gees of acceleration (3 Gees x 200 tons = 600 Gee-Tons). MD-C installed in a 300 ton hull will provide 2 Gees of acceleration (2 Gees x 300 tons = 600 Gee-Tons). MD-C installed in a 600 ton hull will provide 1 Gees of acceleration (1 Gees x 600 tons = 600 Gee-Tons).

Thus the Performance decreases with hull size, but Efficiency does not.

[I am, obviously, just picking a nit.]

This can, however, provide a useful tool for would-be custom designs.
For example if we install MD-C in a 150 ton hull, then 600 Gee-Tons / 150 tons = 4 Gee acceleration.
Or if we install MD-C in a 500 ton hull, then 600 Gee-Tons / 500 tons = 1.2 Gee acceleration (Note that your ship is actually just a little faster than an exactly 1 G ship – this could matter at some critical event.)

 

[OIT]

Engineering Terminology

Atpollard hit the nail on the head.

When reading the statment in question at first, I assumed it was referencing the common engineering phenomenon of declining efficiency beyond a certain size in pretty much any type of propulsion of power generation known to man. However, upon re-reading it, after having been handed a clue-bird by cajon5, it appears to be a fatuous statement on basic physics. What threw me off was the misuse of the word "efficiency".

thanks guys.

I'll hush up now. Nothing to see here, move along, move along.

 

[cajon5]

This can, however, provide a useful tool for would-be custom designs.
For example if we install MD-C in a 150 ton hull, then 600 Gee-Tons / 150 tons = 4 Gee acceleration.
Or if we install MD-C in a 500 ton hull, then 600 Gee-Tons / 500 tons = 1.2 Gee acceleration (Note that your ship is actually just a little faster than an exactly 1 G ship – this could matter at some critical event.)

When I was running CT, way back in the day, I just decided that manoeuver drives were sort of like Larry Niven's reactionless thrusters, and further (to accomodate the rule about hulls sizes between the ones listed on the Book 2 tables producing a manoeuver/jump/power plant output per the next even sized hull) that the effect produced by these thrusters was "quantumized." That is, it was kind of like Niven's hyperdrive--hyperdrive quantom level I produced a given, set FTL speed, there was no faster, slower, etc. The quantum level II drive was an order of magnitude faster, but there was no speed possible between level I and level II. Thus, I reasoned (rationalized?), your ship could accelerate at 1-G or 2-G, but nothing in between. The quantum levels also stopped at 6-G.

 

[Sylvre Phire]

When I was running CT, way back in the day, I just decided that manoeuver drives were sort of like Larry Niven's reactionless thrusters, and further (to accomodate the rule about hulls sizes between the ones listed on the Book 2 tables producing a manoeuver/jump/power plant output per the next even sized hull) that the effect produced by these thrusters was "quantumized." That is, it was kind of like Niven's hyperdrive--hyperdrive quantom level I produced a given set acceleration, there was no faster, slower, etc. The quantum level II drive was an order of magnitude faster, but there was no speed possible between level I and level II. Thus, I reasoned (rationalized?), your ship could accelerate at 1-G or 2-G, but nothing in between. The quantum levels also stopped at 6-G.

As an added historical note, that's pretty much the way they described the difference between jump-1, jump-2, etc. In DGP's Starship Operator's Manual for MT.

Pax et bonum,

Dale