Ship design - am I doing it right?

Hakkonen

Banded Mongoose
I'm going through the ship-design process in High Guard to make sure I understand it.

Tech Level
The Rainbow Dash is a racing sloop, either a nobleman's toy or sponsored racer in a professional league. She's being built at a TL15 shipyard, but most of the critical components will be TL12 to take advantage of "high technology" modifiers.

Step 1: Create a hull
The Rainbow Dash displaces 250 tons, and her hull is both lightweight and streamlined, costing MCr 11.875. Every cubic centimeter is precious in a racing machine, so she doesn't waste space on armor.

Step 2: Install drives
The Rainbow Dash has both a gravitic maneuver drive and a reaction drive for extra speed. Her M-drive/7 is top-of-the-line for TL12, and benefits from 30% size reduction, displacing only 12.25 tons (7% of 250 is 17.5, times 0.7 is 12.25). The Dash's reaction drive is similarly advanced, displacing 56 tons (32% of 250 is 80 tons, times 0.7 is 56). Her jump drive 3 displaces 13.125 tons (7.5% of 250 is 18.75, times 0.7 is 13.125). All of this space-saving does come at a cost: her drive systems cost MCr 36.75, 16.8, and 29.53125, respectively.

Step 3: Install power plant
Dash draws 301 power (50 for ship's systems, 175 for the M-drive, 75 for the J-drive, and 1 for the sensors installed later). A TL15 fusion plant would displace 15.05 tons, but by applying some TL15 materials and manufacturing science (again, 30% size reduction) to a TL12 design, we shave an entire ton off of that and get a 14.05dT, TL12 fusion reactor. Hey, she's a racing ship; saving space is everything. Accounting for the advanced technology used to build it, her power plant costs MCr 21.075.

Step 4: Install fuel tanks
Ouch. Here's where we start having to make compromises. A rating 16 reaction drive in a 250-ton hull consumes 100 tons of fuel per hour. That's why the Rainbow Dash only carries 50 tons (30 minutes' worth) of fuel for her drive: she has to save it for when it counts, but when that time comes she can haul ass (I'm assuming that the thrust ratings of M-drives and R-drives are strictly additive; that is, for 30 minutes, the Rainbow Dash can make Thrust 23). She also carries 75 tons for her J-drive, and 1.405 tons to run the power plant. The total cost to top off all her tanks is 5,000 + 37,500 + 140.5 = Cr 42,640.5.

Step 5: Install bridge
This is simple: according to the table on p. 17 of High Guard, the Rainbow Dash's bridge displaces 20 tons and costs half a megacred. Easy-peasy, lemon squeezy.

Step 6: Install computer
I go with a standard TL12 Computer/20, no frills. It's enough to run Jump Control/3 software, which is really all she needs. No space used, but MCr 5.3 added to the cost of the ship.

Step 7: Install sensors
Civilian grade sensors displace 1 ton, cost MCr 3, and eat 1 power (see step 3).

Step 8: Install weapons
Not applicable. Nobody's taking the Dash into combat, and she can't spare the room for weapons in any event.

Step 9: Install optional systems
Nope.

Step 10: Determine crew
The Rainbow Dash's drives and power plant add up to 95.55 tons; going by the Crew Requirements table on p.21, she needs three engineers. If the Captain, pilot, and astrogator can each also be an engineer, then she only needs three crew.

Step 11: Install staterooms
One double-occupancy stateroom displaces 4 tons, and costs half a megacred. The crew will have to sleep in shifts, but there simply isn't room for more accommodations.

Step 12: Allocate cargo space
A whopping 3.17dT in cargo space. I dunno, maybe a racing vehicle for multi-stage space/planetary races?

Step 13: Finalize design
The racing sloop Rainbow Dash displaces 250 tons, has a crew of three, and can fly goddamned fast for a severely limited amount of time. Maybe the racing team also includes a tender for "pit stops?"

Did I overlook anything?
 
R-drives only use fuel efficiency modifications, streamlining only applies to atmospheric flight and provides a built-in fuel scoop.

If your only doing in system racing drop down to small craft size with a m-drive 9, r-drive rated to taste and no jump drive.

On the other hand if your trying to do a inter system yacht race, max out the j-drive and m-drive instead. ( Look at Decreased Fuel, Early Jump and Size Reduction for the j-drive.)
 
Hakkonen said:
Did I overlook anything?

You could same some space using Decreased Fuel instead of Size Reduction.

There's also the Smaller Bridge option, comes with a disadvantage, but if you really want to save some more space.

There's also the Virtual Crew option to reduce the amount of crew needed.
 
Looks good!

I have a few small niggles:
Hull cost = 250 × 0.05 × 120% × 75% = MCr 11.25

Jump drives start with an extra 5 Dt plus the percentage of the ship size:
Jump Drive Size = ( 5 + 250 × 7.5% ) × 70% = 16.625 Dt

You could save some space by using a Man-9 (with only two advantages) and Reaction-14 drive. Same max acceleration of 23 G. Or even a M-9 + R-15 drive for some extra thrust.

You don't really need power for the J-Drive and M-Drive at the same time. The J-Drive only needs power for a short time when you initiate jump. You can even underpower the ship's basic systems a little for a short while. You might get away with a 10 Dt power plant, saving a little bit of space.

Power Plant fuel is rounded up, so it should be 2 Dt.

Both the small crew and the tiny accommodations makes me uncomfortable, but it's racing craft so that might be OK.
 
baithammer said:
R-drives only use fuel efficiency modifications, streamlining only applies to atmospheric flight and provides a built-in fuel scoop.
http://forum.mongoosepublishing.com/viewtopic.php?f=89&t=120613
Others disagree about advantage applicability, and frankly I see no reason why a higher tech level shouldn't be able to build smaller motors with the same output. The Dash is streamlined for the purpose of aerobraking maneuvers. Why waste fuel when you can shed velocity into an atmosphere, instead?

AndrewW said:
You could same some space using Decreased Fuel instead of Size Reduction.

There's also the Smaller Bridge option, comes with a disadvantage, but if you really want to save some more space.

There's also the Virtual Crew option to reduce the amount of crew needed.
Oh, I know there are things I could tweak; the purpose of the exercise is just to make sure I grok the spacecraft design rules. ;)

AnotherDilbert said:
Looks good!

I have a few small niggles:
Hull cost = 250 × 0.05 × 120% × 75% = MCr 11.25
http://forum.mongoosepublishing.com/viewtopic.php?f=89&t=120614
There seems to be a certain amount of debate regarding the math. Additive modifiers makes more sense to me, and the text is ambiguous. o_O

Jump drives start with an extra 5 Dt plus the percentage of the ship size:
Jump Drive Size = ( 5 + 250 × 7.5% ) × 70% = 16.625 Dt
Thank you! I really wish that extra 5dT was noted on the J-drive table, in addition to the text.
 
Hakkonen said:
http://forum.mongoosepublishing.com/viewtopic.php?f=89&t=120614
There seems to be a certain amount of debate regarding the math. Additive modifiers makes more sense to me, and the text is ambiguous. o_O
What I believe is, of course, not very important, but I'm simply following higher authority:
AndrewW said:
AnotherDilbert said:
From what I remember AndrewW has confirmed (for the Heavy Fighter) that it should be 3000 × 0,05 × 1,2[Streamlined] × 1,5[Reinforced] = MCr 270.

Yup.
 
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