[Spaceships] Homebrew - Alternate Contragrav

[DaltonS]

Gravity Screen System (TL11^) [Hull!]
I decided to go back to first principles (AKA GURPS Vehicles Expansion 2); by analyzing the “Gravity Screen Table” on page 13, a weight reduction of n% requires n/(100-n) kW per square foot of vehicle surface area, with a cost of $100 per kw used. This makes the “Weight Multiplier” equal to 1/(E+1) where “E” is the number of kw/sf used. Using a standard energy point* (and vehicle density) of 100 kW (and cubic feet) per vehicle ton, and the old standard surface area equation Area(sf) = Volume(cf)^(2/3)×6 from GURPS Vehicles, Second Edition, I used a spreadsheet to calculate the table below. Use the “Weight Multiplier” to find the effective weight of the ship. When using a smaller SM system, use three times the “Weight Multiplier” of the larger system to reflect the reduced power of the screen. If multiple systems are used, consider the screens to be layered (ie. use M^n where “M” is the multiplier as a fraction and “n” is the number of systems). Note that this is NOT a force screen variant, and provides no protection against gravitic weapons. The G-Screen Damper described above may still be used against it.

  Size    Cost    Weight  |  Size    Cost    Weight  |  Size    Cost    Weight  
Modifier        Multiplier|Modifier        Multiplier|Modifier        Multiplier   
  SM+4     $1 k   37.50%  | SM+9.5  $600 k    6.64%  |  SM+15  $300 M    0.89%
 SM+4.5    $2 k   32.26%  |  SM+10    $1 M    5.66%  | SM+15.5 $600 M    0.71%
  SM+5     $3 k   29.38%  | SM+10.5   $2 M    4.55%  |  SM+16    $1 B    0.60%
 SM+5.5    $6 k   24.82%  |  SM+11    $3 M    3.99%  | SM+16.5   $2 B    0.47%
  SM+6    $10 k   21.78%  | SM+11.5   $6 M    3.20%  |  SM+17    $3 B    0.41%
 SM+6.5   $20 k   18.10%  |  SM+12   $10 M    2.71%  | SM+17.5   $6 B    0.33%
  SM+7    $30 k   16.18%  | SM+12.5  $20 M    2.16%  |  SM+18   $10 B    0.28%
 SM+7.5   $60 k   13.29%  |  SM+13   $30 M    1.89%  | SM+18.5  $20 B    0.22%
  SM+8   $100 k   11.45%  | SM+13.5  $60 M    1.51%  |  SM+19   $30 B    0.19%
 SM+8.5  $200 k    9.31%  |  SM+14  $100 M    1.28%  | SM+19.5  $60 B    0.15%
  SM+9   $300 k    8.23%  | SM+14.5 $200 M    1.02%  |  SM+20  $100 B    0.13%

* The size of a standard energy point I used came from here.

Originally Posted by Anthony

We can derive it from two sources: power output of weapons, and power output of electric drives.
...
Overall, I'd assume 1 ep is somewhere around 100 kW/ton, which is on a par with a reasonable performance ground car (though said car probably isn't spending only 5% of its mass on its power plant).

Dalton “feeling nostalgic about GURPS 3rd Edition” Spence