1st edition HG Capital Ship Design Example p. 70 Step 3 Fuel/Power Plant

[snrdg121408]

Hello all,

I may have found errata in Step 3 for the power plant fuel requirement. From 1e HG p. 70

Step 3 – Fuel
Julia decides that her heavy cruiser will be capable of 1 4 parsec jump and 4 weeks power plant endurance. Jump fuel required is (0.4 x 75,000) 30,000 tons. Power plant fuel is (2812.5 x 2/3 x2) 3,750 tons. She chooses at this time to fit fuel scoops (MCr 1) and a fuel processor capable of purifying all her fuel in 2 days that is (37,500 /20 /2) 843.75 tons and costs MCr 42.1875.

The power plant requires fuel for 4 weeks.

1e HG Power Plant fuel p. 64

Power plant fuel depends on the tonnage of the plant. For fusion plants an amount of fuel equal to two thirds of the tonnage of the power plant will power the starship for two weeks. For example, a 3,000–ton power plant would consume 2,000 tons of fuel in two weeks of operation. For chemical plants, this figure is 15 times larger.

According to the power plant fuel rule operating a 2,812.5 ton Power Plant-6 for 2 weeks requires (2812.5 x 2/3 x 2) = 3,750 tons of fuel. The Capital Ship Design example requires the power plant to operate for 4 weeks which would require 7,500 tons of fuel.

Note: Traveller High Guard Errata found on the High Guard 1st edition product page

Page 70-72
In Step 3, the Fuel Processor should come in at 937.5 tons and MCr 46.875. The summary costs from this step onwards should therefore be MCr 4.6875 higher each time, and cargo should be 93.75 tons less.

The errata entry did not change the power plant fuel requirement calculation.

The simplest recommendation is to change Step 3 to read:

Step 3 – Fuel
Julia decides that her heavy cruiser will be capable of 1 4 parsec jump and 2 weeks power plant endurance. Jump fuel required is (0.4 x 75,000) 30,000 tons. Power plant fuel is (2812.5 x 2/3 x4) 7,500 tons. She chooses at this time to fit fuel scoops (MCr 1) and a fuel processor capable of purifying all her fuel in 2 days that is (37,500 /20 /2) 937.5 tons and costs MCr 46.875.

Unfortunately, the change in power plant fuel and fuel processor tons leaves (20,412.5) tons not (24,162.5).

 

[AnotherDilbert]

According to the power plant fuel rule operating a 2,812.5 ton Power Plant-6 for 2 weeks requires (2812.5 x 2/3 x 2) = 3,750 tons of fuel. The Capital Ship Design example requires the power plant to operate for 4 weeks which would require 7,500 tons of fuel.

No, the basic requirement is power plant * 2/3 for 2 weeks.
So in the example the power plant is 2812.5 dT. It requires 2812.5 * 2/3 = 1875 dT fuel for 2 weeks. For 4 weeks operation it requires 4/2 * 1875 = 3750 dT fuel.

 

[snrdg121408]

Morning PST AnotherDilbert,

According to the power plant fuel rule operating a 2,812.5 ton Power Plant-6 for 2 weeks requires (2812.5 x 2/3 x 2) = 3,750 tons of fuel. The Capital Ship Design example requires the power plant to operate for 4 weeks which would require 7,500 tons of fuel.

No, the basic requirement is power plant * 2/3 for 2 weeks.
So in the example the power plant is 2812.5 dT. It requires 2812.5 * 2/3 = 1875 dT fuel for 2 weeks. For 4 weeks operation it requires 4/2 * 1875 = 3750 dT fuel.

Thank you for the correction and explanation of the rules. Unfortunately, the Traveller High Errata that changed the fuel processor tons from 843.75 to 937.5 does not appear to be correct unless the fuel processor rule from 1e CRB/MRB p. 110 has been change.

Using the formula I'm going to figure out the total fuel load that the is calculated for:
937.5 tons = ? tons of fuel / 20 / 2 =
937.5 x 20 x 2 = ? tons of fuel
18,750 x 2 = ? tons of fuel
37,500 tons of fuel.

The capital ship design example calculated the jump fuel requirement to be 30,000 tons and 3,750 ton to run the power plant for 4 weeks. The total fuel requirement is 33,750 tons.

Subtracting the jump fuel from the total 37,500 - 30,000 = 7,500 tons of fuel not the 3,750 tons calculated for a 2,812.5 ton power plant for four weeks of operation. To help reverse calculate to the power plant tons from the power plant fuel tons I am converting 2/3 to 0.666667.

7,500 tons of power plant fuel = ? Power Plant tons x 0.666667 x 2
round(7,500 / 0.666667 / 2,1) = ? Power Plant tons
round(11,250 / 2,1) = ? Power Plant tons
round(5,625,1) = ? Power Plant tons
5,625 ton fusion power plant.

With your input I believe I have found the point that HG 1e. Capital Ship Design Example Step 3 - Fuel went off the tracks. Tallying the jump and power plant fuel on p. 70 I get 33,750 tons of fuel. The equation in the text shows the total fuel as 37,500 tons of fuel. In this case I believe the Traveller High Guard Errata should read

Page 70-72
In Step 3, change fuel processor equation from (37,500 /20 /2) to (33,750 /20 /2).

versus

Page 70-72
In Step 3, the Fuel Processor should come in at 937.5 tons and MCr 46.875. The summary costs from this step onwards should therefore be MCr 4.6875 higher each time, and cargo should be 93.75 tons less.

Thank you again for catching my error on how to calculate the tonnage for a fuel processor.

 

[AnotherDilbert]

Glad to help.

The design example in my PDF contains a typo level error. The basic calculation would be 33750 / 20 / 2 = 843.75 dT fuel processor. They have written "(37500 / 20 / 2) 843.75" which is the right result but the wrong calculation.

The errata is wrong. It corrected the result, not the calculation.

The designer is of course free to use any size fuel processor he wants. If he uses a slightly larger size than necessary it's only inefficient, not wrong.

 

[snrdg121408]

Hello again AnotherDilbert,

Glad to help.

The design example in my PDF contains a typo level error. The basic calculation would be 33750 / 20 / 2 = 843.75 dT fuel processor. They have written "(37500 / 20 / 2) 843.75" which is the right result but the wrong calculation.

The errata is wrong. It corrected the result, not the calculation.

The designer is of course free to use any size fuel processor he wants. If he uses a slightly larger size than necessary it's only inefficient, not wrong.

Technically speaking the use of 37,500 tons in the equation is a math error which resulted in the errata calculating for the wrong total fuel tonnage. Using the total fuel tonnage of 33,750 leaves the Summary So Far table correct as shown on 1e HG PDF p. 70.

Changing the text

and a fuel processor capable of purifying all her fuel in 2 days that is (37,500 /20 /2) 843.75 tons and costs MCr 42.1875.

to

and a fuel processor capable of purifying all her fuel in 2 days that is (33,750 /20 /2) 843.75 tons and costs MCr 42.1875.

is in my opinion the easiest correction.

Unfortunately, 1e. HG Softcover and PDF copies Step 4 - Command appears to need corrections too.

Again thank you for catching my mistake and getting me on the right track.