CT Only: Five Sisters Clipper (block 3 revision update)

[Grav_Moped]

Was sort of there before that. Found what's probably a draft for a post I was pretty sure I made, but searching for text strings isn't returning it.
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For what it's worth, the math for the drive tables (for the TL-14 drives and below) is a bit more complex than straight percentages, but works the way they meant for it to work.

These formulae allow decimal-fraction maneuver drives and power plants. (A.5, K.5, etc.) but probably shouldn't. Jump drives will always resolve to a letter.

Jump Drive:
M=Hull tons, Jn=Jump Number

M must be between 100 and 5000 inclusive. Jn must be an integer.

If M=100, Jn must be divisible by two; if an odd Jn is desired, calculate drive size and cost using the next higher Jn divisible by 2. Drive capability and fuel consumption are based on the intended Jn.

If M < 1000 but not evenly divisible by 200, round M up to the next multiple of 200 before calculating drive tonnage.
If M > 1000 but not evenly divisible by 1000, round M up to the next multiple of 1000 before calculating drive tonnage.
This rounding up does not affect fuel consumption calculations.

Jump Drive (tons) = (0.025*M*Jn)+5
Jump Drive (percent of M) = ( (0.025*M*Jn+5)/M ) *100
Cost = MCr0.05*M*Jn
Cost per ton = MCr2*(JD tons-5)

If M=2000 and Jn=1, subtract 5Td and MCr10.
If M*Jn>4000, consult table as exceptions may be present.

Maneuver Drive:
M = Hull Tons, G = Acceleration in Gs

M must be between 100 and 5000 inclusive.
Note: values of M*G less than 100 yield negative drive tonnage! (Values below 200 get weird when you try to figure out Gs per ton of maneuver drive. Just don't go there, ok?)

If M=100, G must be divisible by two; if an odd G is desired, calculate drive size and cost using the next higher G divisible by 2. Drive capability and power requirements are based on the intended drive rating.

If M < 1000 but not evenly divisible by 200, round M up to the next multiple of 200 before calculating drive tonnage.
If M > 1000 but not evenly divisible by 1000, round M up to the next multiple of 1000 before calculating drive tonnage.
This rounding up does not affect fuel consumption calculations.

Maneuver Drive (tons) = (0.01*M*G)-1
Maneuver Drive (percent of M) = ((0.01*M*G)-1/M)*100
Cost = MCr0.02*M*G
Cost per ton = MCr2*(MD tons+1)

If M=2000 and G=1, subtract 2Td and MCr4.
If M*G>4000, consult table as exceptions may be present.
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Power Plant:
M = Hull tons, Pn = Power Plant Number
M must be between 100 and 5000 inclusive.
If M=100, Pn must be divisible by two; if an odd Pn is desired, calculate drive size and cost using the next higher Pn divisible by 2. Powerplant fuel consumption and output is based on the intended Pn.

If M < 1000 but not evenly divisible by 200, round M up to the next multiple of 200 before calculating drive tonnage.
If M > 1000 but not evenly divisible by 1000, round M up to the next multiple of 1000 before calculating drive tonnage.
This rounding up does not affect fuel consumption calculations.

Power Plant (tons) = (0.015*M*Pn)+1
Power Plant (percent of M) = ( (0.015*M*Pn+1)/M )*100
Cost = MCr0.04*M*Pn
Cost per ton = MCr2.67*(PP tons-1)

If M=2000 and Pn=1, subtract 3Td and MCr8.
If M*G>4000, consult table as exceptions may be present.

 

[infojunky]

LBB2.77 and LBB2.81 have ... dramatically INADEQUATE tables for drive performance. There is nowhere NEAR enough granularity in the LBB2 tables for use cases except at exceedingly contrived breakpoints (100, 200, 400, 600, 800, 1000, 2000, 3000, 4000, 5000).

Optimal Drives Usage (LINK) (click it!)

Ever wanted to know how to get away from being stuck with 100 ton hull increments?
There's your answer.

With all that, ever consider rewriting it all in 1/2 g increments?

 

[Grav_Moped]

For what it's worth, the math for the drive tables (for the TL-14 drives and below) is a bit more complex than straight percentages, but works the way they meant for it to work.

These formulae allow decimal-fraction maneuver drives and power plants. (A.5, K.5, etc.) but probably shouldn't. Jump drives will always resolve to a letter.

The "intermediate" drives come from dropping the requirement that M (ship tons) be rounded up to the next 200 or 1000 ton increment for calculating the rating. Maneuver drives, as noted, get silly or imaginary below 200Gs*tons, and require adjustments to that formula.

I ought to make a stab at what the interpolations around the W-Z drives look like, but I don't think the math would be consistent enough to turn into a formula.

 

[mike wightman]

You can get away with quite a lot by building a custom 199t ship. You have to allocate drives as if it is 200t but you save in crew positions.

 

[Spinward Flow]

You can get away with quite a lot by building a custom 199t ship. You have to allocate drives as if it is 200t but you save in crew positions.

Yeah ... I know ...

However, at sub-200 tons, you're way better off using custom LBB5.80 drives than you are attempting to reach the same performance with LBB2.81 standard drives. In the under 200 tons form factors, the difference between 0.01MPn and 10Pn for power plant fuel is just devastating ... particularly with high performance drives in high-G courier ships!

 

[Grav_Moped]

Yeah ... I know ...

However, at sub-200 tons, you're way better off using custom LBB5.80 drives than you are attempting to reach the same performance with LBB2.81 standard drives. In the under 200 tons form factors, the difference between 0.01MPn and 10Pn for power plant fuel is just devastating ... particularly with high performance drives in high-G courier ships!

If you're already committed to high Gs, yes.

I've mentioned this before, but just for giggles, do up a LBB2'81 ship with 6G acceleration. It's quick work, and easy.

 

[Spinward Flow]

I've mentioned this before, but just for giggles, do up a LBB2'81 ship with 6G acceleration. It's quick work, and easy.

@ 200 tons ... that's a difference between 12 tons of power plant fuel (LBB5.80) and 60 tons of power plant fuel (LBB2.81).
Custom LBB5.80 maneuver-6 and power plant-6 drives @ TL=10 weigh in at 34 tons (MCr17) and 36 tons (MCr108), respectively.
Standard LBB2.81 F-class maneuver-6 and power plant-6 drives @ TL=10 weigh in at 11 (MCr24) and 19 tons (MCr48), respectively.

LBB5.80 = 34+36+12 = 82 tons (MCr125)
LBB2.81 = 11+19+60 = 90 tons (MCr72)

So there's a pretty big cost savings (MCr53!) going with standard drives ... but that comes at the expense of losing 8 net tons of hull capacity that could have been dedicated elsewhere, which in a 200 tons (or less) form factor represents at least 4% of hull capacity (which you might not have available to you, depending on the design). Still, for a 200 tons or less form factor, a savings of MCr53 on the cost of drives is going to be QUITE significant, representing a major fraction of the cost of the entire ship!

Now, one factor that crops up from this "napkin math" analysis is that ... the standard drives are themselves smaller than the custom drives option, meaning less tonnage needs to be spent on drives. For ships that are 200+ tons, that can be an important consideration, since more drive tonnage means more engineering positions needed to crew the engineering department ... but in a sub-200 ton form factor, that need for engineers gets waived (along with the need for a medic or a navigator once you're over 200 tons). That in turn brings about a significant savings in crew accommodations (staterooms), life support overhead and salaries.

So let's say you're going with 90 tons of standard F-class maneuver and power plant drives along with the necessary power plant fuel tankage. Now add in B-class jump-2 drives (15 tons) and 40 tons of jump fuel for 2 parsecs. You're up to 145 tons allocated.
Add in a bridge (20 tons) and a model/1bis (1 ton) as the bare minimum computer. You're up to 166 tons.
Add in a single stateroom for 1 crew member (presumably a pilot/gunner) and allocate 1 ton to fire control. You're now up to 171 tons.
Add in a TL=10 fuel purification plant (minimum 8 tons) ... and you're up to 179 tons.

If you want to stop at 199 tons ... that means you've only got 20 tons of cargo capacity for your 6G "hot rod" starship.
You'll be relatively safe from pirates (they'll have to catch you first!), but you'll have an expensive ship that basically amounts to an "incidental cargo delivery van" as a one man operation.

If you use it for mail deliveries (5 tons for mail) that leaves you 15 tons of cargo space to speculate with whenever the markets look favorable to buy ... which isn't much to work with (learn to warehouse excess stock on planets and make multiple jumps to deliver it all?).

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However, if you ... relax ... your need for 6G acceleration ... back to, say ... 5G ... things start looking a fair bit more favorable.

LBB5.80 maneuver-5 and power plant-5 drives @ TL=10 weigh in at 28 tons (MCr14) and 30 tons (MCr90) in a 200 ton form factor and requires 10 tons of power plant fuel. That totals up to 68 combined total tons and MCr104 in construction costs.
LBB2.81 E-class maneuver-5 and power plant-5 @ TL=10 weigh in at 9 tons (MCr20) and 16 tons (MCr40) in a 200 ton form factor and requires 50 tons of power plant fuel. That totals up to 75 combined total tons and MCr60 in construction costs (+7 tons, but -MCr44!).

Take the standard drives and add in B-class jump-2 drives (15 tons) and 40 tons of jump fuel for 2 parsecs. You're up to 130 tons allocated.
Add in a bridge (20 tons) and a model/1bis (1 ton) as the bare minimum computer. You're up to 151 tons.
Add in a single stateroom for 1 crew member (presumably a pilot/gunner) and allocate 1 ton to fire control. You're now up to 156 tons.
Add in a TL=10 fuel purification plant (minimum 8 tons) ... and you're up to 164 tons.

If you want to stop at 199 tons ... that means you've only got 35 tons of cargo capacity for your 5G "hot rod" starship.

The fun thing is though, that fuel is fungible.
Sure, you need to have a fuel tank of 50 tons for the power plant, but if you're double jumping, you really only need 2.5 of the 4 weeks (2 weeks in jump, 1/2 week maneuver reserve) if you don't mind "cutting it close" on fuel reserves.

So if you had 30 tons of cargo space and a 30 ton collapsible fuel tank, doing a 2J2 would require 40+40 tons of fuel for the two jumps (in a 200 ton form factor) and a standard E-class power plant in that form factor would consume 25 tons of fuel during those 2 jumps, for a total of 105 tons of fuel consumed while in jump (maneuver reserves in normal space not included). Well, the 5G "napkin math" model here is already allocating 90 tons towards fuel capacity, so an extra 30 tons of fuel capacity would be sufficient to "self-deploy" across a 4 parsec gap in deep space (half towards jump fuel consumption, with the remaining 15 tons being enough for more than 1 week of maneuvering reserve).

Could even make it a 2-man ship (add extra stateroom) and have 31 tons of cargo capacity, so the crew can be a 2-man crew of a Pilot and a Gunner, rather than a 1-man ship that needs a dual skilled Pilot/Gunner. Same computations as above apply, except you wind up with only a 10-10.75 ton fuel reserve for maneuvering (5.6 days worth), which still ought to be sufficient under most nominal circumstances (absent weapons fire and the need for damage control!) if still carrying mail in order to make payroll regularly.

Conversely, if you want to use the "fuel is fungible" way of looking at things, the standard drive configuration has enough fuel capacity for a J2+1 transit (40+20 tons to jump, 25 tons for 2 weeks during jump) that would consume 85 tons of fuel during 2 weeks. From a 90 ton fuel capacity, that leaves 5 tons of fuel remaining or 2.8 days of maneuvering reserve ... which depending on where the jump points are in the respective systems could potentially be "a little bit tight" on the reserve. That said, ~2.5 days of acceleration/deceleration burn is sufficient to transit ~3.9 AU, which hopefully ought to be enough to reach a wilderness refueling location.

So the "fuel inefficiency" of the standard drive power plant needing a much larger fuel fraction isn't necessarily as much of a disadvantage as it may at first appear (and if it slashes the construction cost of the ship by over 30%(!) may be well worth the option. It really just depends on what you're trying to do and where you want to do it.

Some TU settings, such as the Distant Fringe for example, completely disallow use of LBB2 construction rules and drives entirely, standardizing upon LBB5.80 exclusively for their ship designs.

Conversely, some alien races (such as the Droyne, for example), are set up to use LBB2 construction rules and drives rather than using LBB5.80 ... so there are tradeoffs depending on how much of a stickler you want to be as a Referee about what is allowed (and why) in your campaigns.



Personally, I think that the sub-200 ton with a crew of 2 starship designs are extremely compelling as an option for nascent Traveller "couples" (friends, partners, married, etc.) who are wanting to "make their fortune" among the stars. After all, everyone has to start somewhere ...

 

[Spinward Flow]

So I have a preliminary finding for the notional "block 4 update" getting bumped up to TL=11 and 450 tons mounting J/J/K drives (permitting laser double fire with appropriate programming, if that's your "thing" in a LBB2.81 universe). Standard J-drives have a rating: 1 for an 1800 ton hull, as per the Optimized Drive Usage table, which is why such drives yield a rating: 4 in a 450 ton form factor (1800/4=450).

• The extra +50 tons (@450) "solves the fuel problem" of the 400 ton version (block 3.1) needing fungible fuel to achieve J4+4 with drop tanks performance (and having only 1/2 a week of maneuvering endurance at the end of it). The 450 ton version (block 4) has 180 tons of jump fuel plus 40 tons of power plant fuel, for a total of 220 tons of internal fuel tankage (and a TL=11 fuel purification plant with a 220 ton capacity).
• Total drive tonnage (starship and modular cutter combined) displaces 98+5=103 tons, so an extra engineering position is not needed (saving on crew salaries).
• Crew remains set at 7, with 2x Pilots, 1x Navigator, 2x Engineers, 1x Medic and 1x Gunner ... with only the Navigator and one of the Engineers requiring Skill-1 minimum while all the other crew positions require Skill-2.
• Was able to retain the Environmental Control Type V-c capacity: up to 7 persons in order to "negate" the costs of paying life support (Cr2000 per 2 weeks per crew member) while also raising the Quality of Life aboard (definitely an intangible benefit as far as CT construction rules are concerned), yielding greater autonomy in tramp operational paradigms for chasing more lucrative speculative cargoes (don't need to worry about topping up the life support reserves every 2 weeks at every port of call).
• Armament remains 2 triple turrets ... a triple sandcaster and a triple pulse laser, organized as single batteries.
• TL=11 enabled the installation of a Model/5fib computer hardened against natural radiation as well as weapon damage radiation effects. The EP budget (LBB5.80) for lasers and computer yields an Agility: 3 and Emergency Agility: 4 performance profile.
• Small craft carried is a single Modular Cutter with a standard Modular Cutter Module loaded for cargo hauling. The 2.5 tons of excess space on the Modular Cutter will typically be allocated to a Small Craft Stateroom (2 tons), giving the Modular Cutter an interplanetary 4G maneuver range for making runabout deliveries as a "side gig" while the main starship is either parked in orbit, berthed at a starport/spaceport or maneuvering elsewhere for a variety of reasons. This gives the combined starship+small craft a 30 ton cargo capacity with the starship acting as the parent "mothership" for interstellar travel.

Single production 100% price cost is MCr341.4974 when including the Modular Cutter and cargo Modular Cutter Module.
Volume production 80% price cost is MCr273.19792 ... which is approximately MCr0.6071 per ton (@450 tons) in volume production.
For reference, a J1 Free Trader costs MCr0.185 per ton (@200 tons) to purchase ... and a J2 Far Trader costs MCr0.2978 per ton (@200 tons) ... so a J4 clipper ship costing basically 2x per ton (and needing 2.25x the tonnage at 450 vs 200) for a far more capable starship seem like a worthwhile investment for the added range capacity.



Preliminary results for a 600 ton TL=12 variant mounting M/M/N drives (still rated at code: 4/4/4) suggests a potential increase in cargo/hangar bay capacity of at least 30+ tons, plus the addition of another pair of turrets and another gunner to the crew. The price to buy would go up, but the cargo capacity for speculative cargoes would increase to 60+ tons, making for a much more capable and flexible design overall (in addition to having an even larger external towing capacity for even higher revenue generation potential when needing to transit less than 4 parsecs in a single jump) that can trade range per jump for external cargo hauling capacity.

For a TL=12 support capacity basing out of the Five Sisters/District 268 or Jewell/Regina subsectors, the 600 ton TL=12 option would probably be better ... while the 450 ton TL=11 option might be the better/more easily supportable choice for the Vilis/Lanth and/or Aramis subsectors in the Spinward Marches.

Sure ... for the price of one J4 clipper ship you could buy ~4.5 Far Traders from a shipyard ... but all of those Far Traders wouldn't be able to operate on the same speculative cargo footing as the J4 clipper ship can (or even as a "bulk freight" external hauler like the J4 clipper can when its full range potential "isn't necessary" for a particular destination). For the same price, the J4 clipper is a far more capable and flexible credit generating proposition ... but it's also operated on a completely different basis and paradigm, so the comparison isn't 1:1 (or even 2:1 or 4.5:1, depending on how you want to look at it). That change in operational capacity makes (literal) worlds of difference in what you can do (and even afford to do) as an owner/operator.



In other words, the research is looking promising so far ...

 

[Spinward Flow]

Preliminary results for a 600 ton TL=12 variant mounting M/M/N drives (still rated at code: 4/4/4)

I now have an actual design finalized for this option ... and it's pretty interesting.

• Total drive tonnage (starship and modular cutter combined) displaces 128+5=133 tons, so four Engineering positions are needed (140 ton drive capacity).
  • J4/M4/A2 @ 600 tons (no external load)
  • J3/M3/A1 @ 800 tons (+200 tons external load)
  • J2/M2/A1 @ 1200 tons (+600 tons external load)
  • J1/M1/A0 @ 2400 tons (+1800 tons external load)
• Crew increases to 9, with 2x Pilots, 1x Navigator, 2x Engineers, 1x Medic and 3x Gunners ... with only the Navigator requiring Skill-1 minimumm while all the other crew positions require Skill-2. All crew have single occupancy stateroom accommodations.
• Was able to retain the Environmental Control Type V-c capacity: up to 9 persons in order to "negate" the costs of paying life support (Cr2000 per 2 weeks per crew member) while also raising the Quality of Life aboard (definitely an intangible benefit as far as CT construction rules are concerned), yielding greater autonomy in tramp operational paradigms for chasing more lucrative speculative cargoes (don't need to worry about topping up the life support reserves every 2 weeks at every port of call).
• Armament increases to 6 triple turrets ... 3x triple sandcasters and 3x triple pulse lasers, with each turret organized as its own battery.
• TL=12 enabled the installation of a Model/6fib computer hardened against natural radiation as well as weapon damage radiation effects. The EP budget (LBB5.80) for lasers and computer yields an Agility: 2 and Emergency Agility: 4 performance profile, but the larger computer makes it much easier to run concurrent weapons programs (including Double Fire for the lasers), enhancing deterrence factors.
• Small craft carried is a single Modular Cutter with a standard Modular Cutter Module loaded for cargo hauling plus a spare Modular Cutter Module in another bay. This combination enables the transport of up to 60 tons of cargo internally within the starship hull. The 2.5 tons of excess space on the Modular Cutter will typically be allocated to a Small Craft Stateroom (2 tons), giving the (unarmed) Modular Cutter an interplanetary 4G maneuver range for making runabout deliveries as a "side gig" while the main starship is either parked in orbit, berthed at a starport/spaceport or maneuvering elsewhere for a variety of reasons. This gives the combined starship+small craft a 30+30=60 ton cargo capacity with the starship acting as the parent "mothership" for interstellar travel.
• An air/raft vehicle berth has been added to provide the means to run errands away from the starship itself and for some assistance with the loading/unloading and possible distribution of cargoes under austere landing conditions.
• A 5 ton cargo bay (Mail Vault conversion ready) has been added to the design, allowing the full 60 tons capacity of the 2x Modular Cutter Modules to be reserved for transport of speculative cargoes and/or ordinary freight.
• 0.6 tons of waste space (8.4m³ capacity) is available for use as a Secret Cargo Hold compartments(!).

Single production 100% price cost is MCr488.4648 when including the Modular Cutter and two cargo Modular Cutter Modules.
Volume production 80% price cost is MCr390.77184 ... which is approximately MCr0.6513 per ton (@600 tons) in volume production.
For reference, a J1 Free Trader costs MCr0.185 per ton (@200 tons) to purchase ... and a J2 Far Trader costs MCr0.2978 per ton (@200 tons) ... so a 600 ton J4 clipper ship costing basically 2.2x per ton (and needing 3x the tonnage at 600 vs 200) for a far more capable starship would seem like a worthwhile investment for the added range capacity (not to mention the external load capacity!).

Also, in comparison to the previous preliminary look at 450 tons ... the 600 ton variant costs 1.43x more than the 450 ton option (a 1.33x hull displacement increase) in exchange for increased weaponry (6 turrets instead of 2 and the extra gunners to crew them), a better computer (6fib vs 5fib due to TL=12 vs TL=11) that makes use of the Double Fire program more reasonable (and more dangerous to adversaries!) while also 2x the internal cargo capacity (60 vs 30 tons) and increasing the external cargo towing capacity by 1.33x as well. So almost Cr50,000 per ton more expensive to buy, but the 2x internal cargo capacity (from 30 to 60 tons) will really make a difference with speculative cargo profits when needing to make a J4 transit.

So in my personal estimation, the 600 ton TL=12 option of the basic design is "compelling enough" to not leave sufficient room for the 450 ton TL=11 to gain much traction as a compelling alternative. Being able to J4 to a type A/B starport on a TL=12+ world for annual maintenance won't be that difficult in most sectors (Spinward Marches or otherwise), even if the ship is being operated purely as a tramp with no "home port" to be specifically tethered to and need to return to every year.

In the Spinward Marches, you can use this search term on TravellerMap to find all the type A starports on TL=12 worlds that would be capable of constructing a hybrid LBB2.81/LBB5.80 design like this 600 ton J4 clipper that I'm outlining here (and will wind up posting in a new thread at some point Soon™).

in:spinward uwp:A??????-C

For other sectors, you can replace the word "spinward" with a part of the unique name for your sector of preference to limit the results to that region of charted space.

Interestingly enough, Mire/Darrian (A665A95–C) would be quite capable of building the 600 ton TL=12 J4 clipper ship design ... and it already has a fiber optic computer built into the design, so a localized variation of the design could be constructed at Mire for use by Darrian traders, if desired. But then, the same can be said of the Sword Worlds too (Gram and Sacnoth) ... and a J4 clipper with a lot of load capacity would be a big help to the Sword Worlds for keeping supply lines running from Narsil, Anduril or Orcrist out to Enos (think about it).

 

[Spinward Flow]

This starship design is being retconned out of existence and "de-canonized" (for whatever that's worth) by the author (me), in favor of a superior design that I will be posting ... Soon™.