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Book 2 Small Craft Design

robject

robject

SOC-14 10K
Admin Award
Marquis
Reverse engineering the Book 2 small craft, I find a couple of interesting things going on.

First, crew accomodations are all in the form of two couches, for a total of 1 ton. There is no bridge.

Second, fuel is 1% of thrust, with a minimum of 1 ton.

Third, I found some things that are most likely either errors or fudges (a rose by another name). More importantly, one particular variance (and perhaps two) is probably explained as being a TL effect.

In all cases, drive volume can be determined by the formula:

Volume = 2.7 + DV * tons-thrust

Where DV varies according to the table below:

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">All volumes are in tons.

TL10? TL12? TL13? TL14?
DV DV DV DV
tthrust fuel DV MCr 0.0612 0.06 0.055 0.046
------- ---- ----- --- ------ ----- ----- -----
launch 20 1 5 14
slow boat 90 1 8.1 15 8.1
boat 180 1.8 13.5 16 13.5
fighter 60 1.2 6 18 6
slow pinnace 80 1 6.4 18 6.38
pinnace 200 2 14.7 20 14.7
cutter 200 2 14.5 28 14.7
shuttle 285 2.85 20.15 33 20.142</pre>[/QUOTE]For reference, here's all of the numbers for all DV ratios.

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;"> DV DV DV DV
tthrust fuel DV MCr 0.0612 0.06 0.055 0.046
------- ---- ----- --- ------ ----- ----- -----
launch 20 1 5 14 3.924 3.9 3.8 3.62
slow boat 90 1 8.1 15 8.208 8.1 7.65 6.84
boat 180 1.8 13.5 16 13.716 13.5 12.6 10.98
fighter 60 1.2 6 18 6.372 6.3 6 5.46
slow pinnace 80 1 6.4 18 7.596 7.5 7.1 6.38
pinnace 200 2 14.7 20 14.94 14.7 13.7 11.9
cutter 200 2 14.5 28 14.94 14.7 13.7 11.9
shuttle 285 2.85 20.15 33 20.142 19.8 18.375 15.81
gig 120 1.2 ??? ?? 10.044 9.9 9.3 8.22 </pre>[/QUOTE]Here are the tentative conclusions I'm reaching.

</font>
  • The cutter's drive volume is actually 14.7.</font>
  • The fighter's drives are due to high tech.</font>
  • The slow pinnace's drive volume is actually 7.5.</font>
  • The shuttle TL is indeed lower.</font>
  • The launch's drive volume is probably 4.</font>

My "corrected" table would therefore be:

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">All volumes are in tons.

TL tthrust fuel DV MCr Notes
-- ------- ---- ----- --- -----------------------
launch 12 20 1 4 14 +1 ton to cargo
slow boat 12 90 1 8.1 15
boat 12 180 1.8 13.5 16
fighter 13 60 1.2 6 18
slow pinnace 12 80 1 7.5 18 -1.1 tons from cargo
pinnace 12 200 2 14.7 20
cutter 12 200 2 14.7 28 -0.2 tons from cargo
shuttle 12 285 2.85 19.8 33 +0.3 tons to cargo</pre>[/QUOTE]Although, I'd prefer the Shuttle to be a lower TL design.
 
Reverse engineering the Book 2 small craft, I find a couple of interesting things going on.

First, crew accomodations are all in the form of two couches, for a total of 1 ton. There is no bridge.

Second, fuel is 1% of thrust, with a minimum of 1 ton.

Third, I found some things that are most likely either errors or fudges (a rose by another name). More importantly, one particular variance (and perhaps two) is probably explained as being a TL effect.

In all cases, drive volume can be determined by the formula:

Volume = 2.7 + DV * tons-thrust

Where DV varies according to the table below:

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">All volumes are in tons.

TL10? TL12? TL13? TL14?
DV DV DV DV
tthrust fuel DV MCr 0.0612 0.06 0.055 0.046
------- ---- ----- --- ------ ----- ----- -----
launch 20 1 5 14
slow boat 90 1 8.1 15 8.1
boat 180 1.8 13.5 16 13.5
fighter 60 1.2 6 18 6
slow pinnace 80 1 6.4 18 6.38
pinnace 200 2 14.7 20 14.7
cutter 200 2 14.5 28 14.7
shuttle 285 2.85 20.15 33 20.142</pre>[/QUOTE]For reference, here's all of the numbers for all DV ratios.

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;"> DV DV DV DV
tthrust fuel DV MCr 0.0612 0.06 0.055 0.046
------- ---- ----- --- ------ ----- ----- -----
launch 20 1 5 14 3.924 3.9 3.8 3.62
slow boat 90 1 8.1 15 8.208 8.1 7.65 6.84
boat 180 1.8 13.5 16 13.716 13.5 12.6 10.98
fighter 60 1.2 6 18 6.372 6.3 6 5.46
slow pinnace 80 1 6.4 18 7.596 7.5 7.1 6.38
pinnace 200 2 14.7 20 14.94 14.7 13.7 11.9
cutter 200 2 14.5 28 14.94 14.7 13.7 11.9
shuttle 285 2.85 20.15 33 20.142 19.8 18.375 15.81
gig 120 1.2 ??? ?? 10.044 9.9 9.3 8.22 </pre>[/QUOTE]Here are the tentative conclusions I'm reaching.

</font>
  • The cutter's drive volume is actually 14.7.</font>
  • The fighter's drives are due to high tech.</font>
  • The slow pinnace's drive volume is actually 7.5.</font>
  • The shuttle TL is indeed lower.</font>
  • The launch's drive volume is probably 4.</font>

My "corrected" table would therefore be:

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">All volumes are in tons.

TL tthrust fuel DV MCr Notes
-- ------- ---- ----- --- -----------------------
launch 12 20 1 4 14 +1 ton to cargo
slow boat 12 90 1 8.1 15
boat 12 180 1.8 13.5 16
fighter 13 60 1.2 6 18
slow pinnace 12 80 1 7.5 18 -1.1 tons from cargo
pinnace 12 200 2 14.7 20
cutter 12 200 2 14.7 28 -0.2 tons from cargo
shuttle 12 285 2.85 19.8 33 +0.3 tons to cargo</pre>[/QUOTE]Although, I'd prefer the Shuttle to be a lower TL design.
 
Small Craft Design Core v2

Here's the core rules for small craft design in Book 2 -- at least, as near as I can tell.

Hull price varies by volume.
* Up to 74 tons: KCr250 per ton.
75 tons and up: KCr160 per ton.

All small craft have a 1t cockpit, with room for 2 people.

Additionally, bays cost Cr150,000 per ton. Yes, that's quite expensive.

Select your acceleration, in G's.

Drive volume (t) = 2.7 + 0.06 * hull volume * accel. Max volume = 19.8 tons (285tt).
Drive cost = MCr3.5, plus MCr 0.5 per ton of drive.
Fuel (t) = hull volume * accel / 100
(fuel is always at least one ton).

That's it, folks. All other accessories are standard cost and volume.

What, you want EPs, too?

EP (probably) = hull volume * accel / 100

All power up to the first EP is unavailable for add-on systems.

(*) Milspec designs (like fighters) might require additional rules to increase the price...

Note: The combo drives are now too expensive to consider installing into starships.
 
Small Craft Design Core v2

Here's the core rules for small craft design in Book 2 -- at least, as near as I can tell.

Hull price varies by volume.
* Up to 74 tons: KCr250 per ton.
75 tons and up: KCr160 per ton.

All small craft have a 1t cockpit, with room for 2 people.

Additionally, bays cost Cr150,000 per ton. Yes, that's quite expensive.

Select your acceleration, in G's.

Drive volume (t) = 2.7 + 0.06 * hull volume * accel. Max volume = 19.8 tons (285tt).
Drive cost = MCr3.5, plus MCr 0.5 per ton of drive.
Fuel (t) = hull volume * accel / 100
(fuel is always at least one ton).

That's it, folks. All other accessories are standard cost and volume.

What, you want EPs, too?

EP (probably) = hull volume * accel / 100

All power up to the first EP is unavailable for add-on systems.

(*) Milspec designs (like fighters) might require additional rules to increase the price...

Note: The combo drives are now too expensive to consider installing into starships.
 
Very promising

So what's a few square pegs in round holes... ;)
 
There may be a problem with my conclusions.

The 200tt combo drive displaces 14.7 tons, but only costs MCr4.2. Wouldn't a Free Trader prefer that tradeoff, instead of installing an A power and A maneuver drive, for 6 tons at MCr12? That's a savings of nearly MCr8. Sure, the combo drive is larger, but only by 9 tons. A Far Trader might prefer to absorb that and have a lower price tag.

So I'm thinking the drives might have to cost more. Any opinions?

At any rate, the combo drives are obviously less efficient.
 
There may be a problem with my conclusions.

The 200tt combo drive displaces 14.7 tons, but only costs MCr4.2. Wouldn't a Free Trader prefer that tradeoff, instead of installing an A power and A maneuver drive, for 6 tons at MCr12? That's a savings of nearly MCr8. Sure, the combo drive is larger, but only by 9 tons. A Far Trader might prefer to absorb that and have a lower price tag.

So I'm thinking the drives might have to cost more. Any opinions?

At any rate, the combo drives are obviously less efficient.
 
I'll take a look at it, robject. It looks pretty close to what I got when I reverse-engineered the CT small craft.
 
I'll take a look at it, robject. It looks pretty close to what I got when I reverse-engineered the CT small craft.
 
I've jiggered the numbers slightly; though the Fighter gets a little cheaper as-is, the drive combos take up more of the cost, and therefore are not palatable at all for starships.

I'll edit my "system" above to reflect that.

The short of it is this: the combo drives are too big to fit into starships, and regular drives are WAY too expensive to (normally) fit into small spacecraft.

That also means that milspec (or special private or corporate-owned) small craft can use the more expensive starship Type A M-drive and power plant, with a corresponding increase in free space.

However,

ASSUMPTION: the minimum starship M-drive volume is 1 ton.
ASSUMPTION: the minimum fusion power plant is 0.00126 tons.

THEREFORE, these drives should be possible:

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Tons-Thrust (M-vol P-vol) Total MCr
ca 20 1 0.4 1.4 4.8
cb 60 1 1.2 2.2 6.4
cc 80 1 1.6 2.6 7.2
cd 90 1 1.8 2.8 7.6
ce 100 1 2 3 8.0
cf 120 1 2.4 3.4 8.8
cg 180 1 3.6 4.6 11.2
ch 200 1 4 5 12.0
cj 285 1.5 6 7.5 18.0


Hull Vol ca cb cc cd ce cf cg ch cj
10 2 6
20 1 3 4 4 5 6
30 2 2 3 3 4 6
40 1 2 2 2 3 4 5
50 1 1 1 2 2 3 4 5
60 1 1 1 1 2 3 3 4
80 1 1 1 1 2 2 3
90 1 1 1 2 2 3
95 1 1 1 2 3</pre>[/QUOTE]
 
I've jiggered the numbers slightly; though the Fighter gets a little cheaper as-is, the drive combos take up more of the cost, and therefore are not palatable at all for starships.

I'll edit my "system" above to reflect that.

The short of it is this: the combo drives are too big to fit into starships, and regular drives are WAY too expensive to (normally) fit into small spacecraft.

That also means that milspec (or special private or corporate-owned) small craft can use the more expensive starship Type A M-drive and power plant, with a corresponding increase in free space.

However,

ASSUMPTION: the minimum starship M-drive volume is 1 ton.
ASSUMPTION: the minimum fusion power plant is 0.00126 tons.

THEREFORE, these drives should be possible:

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Tons-Thrust (M-vol P-vol) Total MCr
ca 20 1 0.4 1.4 4.8
cb 60 1 1.2 2.2 6.4
cc 80 1 1.6 2.6 7.2
cd 90 1 1.8 2.8 7.6
ce 100 1 2 3 8.0
cf 120 1 2.4 3.4 8.8
cg 180 1 3.6 4.6 11.2
ch 200 1 4 5 12.0
cj 285 1.5 6 7.5 18.0


Hull Vol ca cb cc cd ce cf cg ch cj
10 2 6
20 1 3 4 4 5 6
30 2 2 3 3 4 6
40 1 2 2 2 3 4 5
50 1 1 1 2 2 3 4 5
60 1 1 1 1 2 3 3 4
80 1 1 1 1 2 2 3
90 1 1 1 2 2 3
95 1 1 1 2 3</pre>[/QUOTE]
 
“At any rate, the combo drives are obviously less efficient.”

If I understand you correctly the small ship drives may become increasingly less efficient as they and or the craft get larger. If they are of the reactionless type there could be a good physical reason why there is a big drive/little drive split around 100 tons. I mean why build a 95 ton shuttle instead of a 120 ton shuttle unless the drive system requires it.
 
“At any rate, the combo drives are obviously less efficient.”

If I understand you correctly the small ship drives may become increasingly less efficient as they and or the craft get larger. If they are of the reactionless type there could be a good physical reason why there is a big drive/little drive split around 100 tons. I mean why build a 95 ton shuttle instead of a 120 ton shuttle unless the drive system requires it.
 
I don't know what to do about it, now. I think the CT designs are really cool, but it's hard to reconcile them to CT starships, let alone anything else.

Imagine a 20 ton launch designed with my more recent assumptions about drive systems.

Garden-Variety Budget Launch: 1G, MCr 9.8
Good for transferring passengers and cargo. Shove a fuel bladder in the cargo area and it also serves as a fuel skimmer.
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Volume Component MCr
20 Hull 5.0
1.4 Drives (20tt) 4.8
1 Fuel
1 Fuel scoops
1 Cockpit
4 Accel Couches(8)
11.6 Cargo</pre>[/QUOTE]Fast Launch, aka Gig: 6G, MCr 17
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Volume Component MCr
20 Hull 5
3.4 Drives(120tt) 8.8
1.2 Fuel
1 Cockpit
4 Accel couches(8)
1 Hardpoint
LMS Turret 3.2
9.4 Cargo</pre>[/QUOTE]Strike Shuttle: 6G, MCr 48.2
For carrying infantry and support vehicles.
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Volume Component MCr
95 Hull 15.2
5 M-Drive C 12.0
12 Power plant C 9.0
6 Fuel
1 Cockpit
1 Hardpoint
LMS Turret 3.0
30 ATV module 1 4.5
30 ATV module 2 4.5
10 Infantry(20)</pre>[/QUOTE]
 
I don't know what to do about it, now. I think the CT designs are really cool, but it's hard to reconcile them to CT starships, let alone anything else.

Imagine a 20 ton launch designed with my more recent assumptions about drive systems.

Garden-Variety Budget Launch: 1G, MCr 9.8
Good for transferring passengers and cargo. Shove a fuel bladder in the cargo area and it also serves as a fuel skimmer.
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Volume Component MCr
20 Hull 5.0
1.4 Drives (20tt) 4.8
1 Fuel
1 Fuel scoops
1 Cockpit
4 Accel Couches(8)
11.6 Cargo</pre>[/QUOTE]Fast Launch, aka Gig: 6G, MCr 17
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Volume Component MCr
20 Hull 5
3.4 Drives(120tt) 8.8
1.2 Fuel
1 Cockpit
4 Accel couches(8)
1 Hardpoint
LMS Turret 3.2
9.4 Cargo</pre>[/QUOTE]Strike Shuttle: 6G, MCr 48.2
For carrying infantry and support vehicles.
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Volume Component MCr
95 Hull 15.2
5 M-Drive C 12.0
12 Power plant C 9.0
6 Fuel
1 Cockpit
1 Hardpoint
LMS Turret 3.0
30 ATV module 1 4.5
30 ATV module 2 4.5
10 Infantry(20)</pre>[/QUOTE]
 
Kurega is right. What benefit does the 95 ton 3G shuttle have that a 100 ton 4G spacecraft doesn't?

A good assumption to make is that the 285tt combo drive is the largest possible.


Now comes price comparisons.

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Volume Component Price
95 Hull 15.2
1 Cockpit
19.8 Drives (285tt) 13.4

(74.2) = Totals ========= 28.6

Volume Component Price
100 Hull 20
20 Bridge

1 M-Drive A 4 +
4 Power A 3 = 12

(75) == Totals(A) ====== 32

3 M-Drive B 8 +
8 Power B 6 = 14

(69) == Totals(B) ====== 34</pre>[/QUOTE]Well now we know. I forgot that craft 100 tons and larger require a bona-fide bridge. That's why the Shuttle is worth it... Plus it's still cheaper.

It might also have a smaller sensor signature, being a Class 7 ship (10-99 tons) rather than a Class 8 ship (100-999 tons). But that's a rules issue.
 
Kurega is right. What benefit does the 95 ton 3G shuttle have that a 100 ton 4G spacecraft doesn't?

A good assumption to make is that the 285tt combo drive is the largest possible.


Now comes price comparisons.

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Volume Component Price
95 Hull 15.2
1 Cockpit
19.8 Drives (285tt) 13.4

(74.2) = Totals ========= 28.6

Volume Component Price
100 Hull 20
20 Bridge

1 M-Drive A 4 +
4 Power A 3 = 12

(75) == Totals(A) ====== 32

3 M-Drive B 8 +
8 Power B 6 = 14

(69) == Totals(B) ====== 34</pre>[/QUOTE]Well now we know. I forgot that craft 100 tons and larger require a bona-fide bridge. That's why the Shuttle is worth it... Plus it's still cheaper.

It might also have a smaller sensor signature, being a Class 7 ship (10-99 tons) rather than a Class 8 ship (100-999 tons). But that's a rules issue.
 
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