Is it time for Jump-7 drives in Traveller?

[robject]

You neglected to mention MgT HG2e - the jump drive has lots of options for fuel efficiency, size reduction etc as TL increases.
Some of these have made their way into official MgT 3I supplements and are broadly compatible with the T5 rules.

So what we really need rather than jump 7 are conversion rules for the new rules in T5/MgT HG2e to retcon CT and HG 3I designs...

We expended effort to try to keep MgT2 drives roughly compatible with T5.

T5's stage effects generally seem (to me) to be rather MegaTraveller-like. Its ship components most resemble CT Book 2. And, its formulas are HG-like.

The real savings is in fuel economy.

A back-port might then resemble something like this:

Drive Stage	TL	Cost	Fuel	Tons	Notes
Experimental (Exp)	-3	x10	200%	x3	Generally nonworking
Prototype (Pro)	-2	x5	120%	x2	Generally nonworking
Early (Ear)	-1	x2	110%	x1	Dangerous, Bulky, Inefficient, Unreliable, Temperamental
Standard (Std)	0	x1	100%	x1
Improved (Imp)	+1	x2	90%	x1
Modified (Mod)	+2	x1	90%	/2	* see below
Advanced (Adv)	+3	x2	80%	/3	* see below
Ultimate (Ult)	+4	x3	70%	/4	* see below

* Minimum volumes for CT Book 2: 10 tons (jump), 2 tons (maneuver), 4 tons (power plant).
* Minimum volumes for CT HG: x1 tons for maneuver and jump. Use HG power plant table for power plant.


Assume a straight application to CT Book 2 works.
For example, a Jump Drive B. (Is it TL-10?)

Standard Jump Drive B (TL-10). 15 tons, MCr 20.

Assuming I had the cash, if a TL 12 starport had a B drive, it would be the Modified version. It would cost the same, but use 90% of the fuel of a standard B. The specs for "Modified" say it's half the tonnage, but that the minimum tonnage is 10 tons.

Modified Jump Drive B (TL-12). 10 tons, MCr 20, 90% fuel.

 

[Spinward Flow]

THAT assumes that long-haul freight is being handled by Farports, because Hop drops out of jumpspace at 1000 diameters.

Yet another case for having maneuver drives more powerful than a mere 1G ...

 

[robject]

Yet another case for having maneuver drives more powerful than a mere 1G ...

Yeah it is!

It also opens up markets for things like slow insystem barges, fast pinnaces, insystem jumpers, and "truck stop" farports with a cargo and passenger terminal. Essentially a remote extension of the mainworld starport.

I can see a farport established 60,000,000 km away from a gas giant, operating a giant percolator in the GG's atmosphere to throw fuel into orbit for loading into tankers, because it's going to take one day for a tanker to cross 60 million km to the gas giant, and another day to come back.

There's the operations model for the farport. One tanker (plus one spare) shuttling fuel from the GG to storage tanks on site. Passenger and cargo service to take care of hop ship payload. Fast pinnaces to get passengers to the mainworld. 6G could get them from 10 AU to the mainworld, unload passengers, load passengers, and back in, say, 14 days. Slow barges to get the cargo there: 1G takes 8 days one way, or 0.1 G takes a month.

Customs cutters (carrying colonial marines) to keep things civil.

***

Okay, here's some of the elements of my Farport.


Fuel Storage Tank (1)

If you get ten 600t Hop freighters a week, you'll need 600t of fuel per week. Storage is cheap, so let's have a month of fuel stored. Call it a 2400 ton hull filled with fuel. Lifters for attitude control. Basic controls (11 tons of control space). Four transfer pumps. A fuel purifier (theoretical minimum full refining time is 6 hours).

Carve it out of a planetoid.

MCr 31.
No crew -- Farport operations manage these.


Tankers (2)

Next we need a tanker. Maneuver 1. Two days per round trip... say two trips per week. Call it 300 tons of fuel per trip. Double that amount to 600 tons per trip. Don't need a refinery. Minimal bridge. No gunners -- escort it if necessary so you have high guard protection. Don't need fuel specially allocated for the M-drive -- just use the tank. Scoops. Model/1.

700 tons. Nine crew. Clinic. Counsellor.

Not planetoids -- we might have to skim.

MCr 77. Buy two of them => MCr 154.
18 crew total.


Cargo Depots (2)

Say those liners bring in 100 tons of cargo each. That's 1,000 tons of cargo you need to offload, per week. 4,000 tons per month. And we actually want to double that. Of course, you'll send the entire amount to the mainworld via barges, but you also need to be able to handle a month of cargo because JIT doesn't work. So, four hulls that each hold 2,000 tons of cargo.

Install four large cargo doors. 2100 tons. Carve them out of planetoids.

MCr 30 each => MCr 120.
No crew -- Farport operations manage these.



Passenger Layover Hotels (2)

We need to handle up to 300 passengers per week arriving, plus potentially 300 departing, and if we're unlucky they might all be here at the same time, so let's design two 300-passenger hotel hulls.

1600 tons each.

50 tons cargo. Grapples to connect with up to 600 ton ships. 20 officers' quarters and work offices for customer care staff (counsellors, stewards, medics, security). Life support for up to 50 high passengers and 800 others. Adaptations for up to 100 exotic atmosphere breathers. 40 luxury passenger staterooms, 260 standard passenger staterooms. 500 tons of common space.

Also carved out of a planetoid.

MCr 182 each. Let's buy two. => MCr 364.
40 crew.


Customs Cutters (4)

Say we only need to cover the tankers (say the main starport provides security to and from it). Call it two per tanker = 4 cutters.

MCr 28 each => MCr 112.
8 crew, plus 4 squads of marines.



Fast Shuttles (20)

Assume we have to transport 300 passengers per week (1200 per month) between here and the mainworld, and it takes one week round-trip at 6Gs... barely. So we want 200% capacity. Let's pile people aboard custom shuttles.

We might as well make them TL 17 shuttles, then. 5 G's. 200 tons. Takes us 4 days to get there, 4 days in port, and 4 days back. Call it 2 weeks to round trip. Two runs per month per shuttle. 20 tons cargo. 3 crew. 9 tons fuel. 50 passengers per run = 100 passengers per month.

Planetoid hulls again.

MCr 38 each. We need twelve of them just to barely cover traffic, so let's buy twenty => MCr 760.
60 crew total.


Cargo Lighter Barges

These things need to move 4,000 tons of cargo per month between the mainworld and here. Assuming a trip is 9 days, a week layover, and 9 days back, just call it one month per round trip. These will be cargo lighters on a planetoid frame.

I'll keep them smaller because I doubt I want to wait to move an entire 4,000 tons in one barge. But I will make them overtonned.

1200 tons. 1000 tons of cargo. M1, P1, one month of fuel. 13 luxury officer's suites for crew. 20 tons of common space.

Low berths could potentially go here.

These are cozy rides for crew. The luxury suites are nice. The captain gets a study adjacent to his luxury suite -- ten tons of space in total. This keeps them from going crazy; they're not scouts after all, and this is mind-numbing work.

MCr 65. We need four to just barely cover traffic, so let's buy eight => MCr 260.
104 crew total.



Crew Habitat and Ops

I count 230 ship crew, 20 marines, plus whatever operational staff is on the Farport proper. I need to be able to house them all in a planetoid habitat, even if they're not always there. I'd better make it a luxury suite each, too, since this ain't interstellar space travel and they're going to go nuts otherwise.

Call it 250 rooms, and a platoon barracks. 20 tons of cargo. Grapples for various smallcraft... say up to 14 smallcraft, with 490 tons of total displacement supported.

Now let's add 50 tons of operational space for the Farport itself, and a Model/4 computer.

I know we'll need sensors, but I'm out of steam for now.

Another planetoid hull. 1800 tons. MCr 200.

===========

SUBTOTAL INSTALLATION VOLUME: 15,800 tons (installation only, not counting small craft and transports)
SUBTOTAL COST: A cool two billion credits (including small craft and transports)
STAFF/CREW: 230
MARINES: 22

 

[mike wightman]

Not really - hauling the additional tonnage through jump is a waste when there are better options available - see the GT LASH model...

 

[Fovean]

because Hop drops out of jumpspace at 1000 diameters

Hm, yes. I had forgotten that little tidbit. You are correct, sir - nothing is ever easy

 

[spank]

You could borrow the reduced fuel requirements from higher TLs that MT introduced.

This is fundamentally what is missing from jump drive progression.
Under CT rules J-7 approaches impossibility. Not for any rules or tech reason, but the simple math of it,
A J-7 ship is going to require the following minimum hull volume allowances,
70% for fuel,
17.5% for a J-7 drives
10.5% for a matching powerplant.
1.5% for a 1G maneuver driver.
That leaves 0.5% for the bridge, staterooms, and the 5 tons that CT adds to all Jump drives.
.
That's not to say that I don't think J-7 should be permitted, functionally going from J-6 to J-7 is not a big change, it would not change the game in any fundamental way.
.
The big issue is that none of the drives ever get more efficient, it makes sense that a J-drive would require a powerplant of similar rating, and being able to use the same table to select them is quite convenient, what doesn't make sense is a J-1 drive is always the same size, and always uses the same amount of fuel, from TL-9 to TL-15. Adding a TL modifier to fuel usage per J-Number would make a lot of sense, and go a long way towards making higher jump numbers possible.
I'm feeling too lazy to go dig MT out of the pile, so I'll just throw out so numbers.
If, for instance, you assumed TL 12 was the base line of 10% jump fuel use and decided that each TL below TL 12 jumps would use 0.5% more fuel per JN, and above TL 12 jumps would use 0.5% less fuel per JN, then you'd end up with something like this,
TL 9, J-1 --11.5% Fuel
TL 10, J-1 --11% Fuel
TL 11, J-2 --21% Fuel
TL 12, J-3 --30% Fuel
TL 13, J-4 --38% Fuel
TL 14, J-5 --45% Fuel
TL 15, J-6 --51% Fuel
TL 16, J-7 --56% Fuel
And this would continue with your max jump getting more expensive as you went on up in TL, until TL-20/21 when a J11/12 would need 66% of hull volume in fuel. After that max jumps for each TL would need progressively less hull volume. But by that point you should be on to another technology, be it Hop drive, or something else.

 

[Grav_Moped]

This is fundamentally what is missing from jump drive progression.
Under CT rules J-7 approaches impossibility. Not for any rules or tech reason, but the simple math of it,
A J-7 ship is going to require the following minimum hull volume allowances,
70% for fuel,
17.5% for a J-7 drives
10.5% for a matching powerplant.
1.5% for a 1G maneuver driver.
That leaves 0.5% for the bridge, staterooms, and the 5 tons that CT adds to all Jump drives.
.
That's not to say that I don't think J-7 should be permitted, functionally going from J-6 to J-7 is not a big change, it would not change the game in any fundamental way.
.
The big issue is that none of the drives ever get more efficient, it makes sense that a J-drive would require a powerplant of similar rating, and being able to use the same table to select them is quite convenient, what doesn't make sense is a J-1 drive is always the same size, and always uses the same amount of fuel, from TL-9 to TL-15. Adding a TL modifier to fuel usage per J-Number would make a lot of sense, and go a long way towards making higher jump numbers possible.
I'm feeling too lazy to go dig MT out of the pile, so I'll just throw out so numbers.
If, for instance, you assumed TL 12 was the base line of 10% jump fuel use and decided that each TL below TL 12 jumps would use 0.5% more fuel per JN, and above TL 12 jumps would use 0.5% less fuel per JN, then you'd end up with something like this,
TL 9, J-1 --11.5% Fuel
TL 10, J-1 --11% Fuel
TL 11, J-2 --21% Fuel
TL 12, J-3 --30% Fuel
TL 13, J-4 --38% Fuel
TL 14, J-5 --45% Fuel
TL 15, J-6 --51% Fuel
TL 16, J-7 --56% Fuel
And this would continue with your max jump getting more expensive as you went on up in TL, until TL-20/21 when a J11/12 would need 66% of hull volume in fuel. After that max jumps for each TL would need progressively less hull volume. But by that point you should be on to another technology, be it Hop drive, or something else.

Psst: drop tanks.

 

[spank]

.

Psst: drop tanks.

I like drop tanks,
And I hate drop tanks.
They are an expedient solution, but they also mask the fact that efficiency never increases
They also fundamentally change the nature of space ships equipped with them, they will always be a main line, settled world ship. Throwing away your fuel tank is a huge risk. To use drop tanks there would have to be a huge infrastructure to make sure there are drop tanks at each stop, not just drop tanks but tanks of the exact size and configuration needed. If you take your 1,000 ton J-7 ship out to somewhere and there are not 700 ton drop tank, that also fit your ship, then you are deeply and truly hosed.
And not to belabor the point, drop tanks as a work-around hides the fact that J-drives never get anymore efficient. There is no reason a civilization 7 TLs advanced from J-1 should still be burning the same amount of fuel to make that jump.
Surely a 30% increase in efficiency is achievable.

 

[mike wightman]

Drop tanks also inevitably lead to the discussion about tankers with long hoses fueling a ship just before jump...

Note that MgT introduces TL effects, one of them is reduced fuel use per TL higher than introduction. I would combine this with the MT fuel progression.

Tech Level	9-16	17	18	19	20	21
fuel coefficient	1.0	0.8	0.6	0.4	0.2	0.1

The MgT rule is a 10% jump fuel reduction per TL above introduction - so a TL15 jump 3 engine would use only 30% of the jump fuel requirement (also 30%) for a jump fuel total of 21% of hull displacement for jump 3.

 

[Krikkitone]

T5 gives J7 at TL 16…it also lets you use AM for Jump fuel at TL19?18, and has the Hop drive (10 parsecs for 1 parsec of fuel) at TL 17

 

[mike wightman]

I am of the opinion that Traveller should have stuck with base six for drives rather than decimalising, MT went all the way to TL22 in some design elements and yet the jump drive and m-drive were capped at 6.

 

[spank]

I could certainly see an argument for capping jump drives at 6, but I think it should really be an issue of the tech being superceded.

Drop tanks also inevitably lead to the discussion about tankers with long hoses fueling a ship just before jump...

Note that MgT introduces TL effects, one of them is reduced fuel use per TL higher than introduction. I would combine this with the MT fuel progression.

Tech Level	9-16	17	18	19	20	21
fuel coefficient	1.0	0.8	0.6	0.4	0.2	0.1

The MgT rule is a 10% jump fuel reduction per TL above introduction - so a TL15 jump 3 engine would use only 30% of the jump fuel requirement (also 30%) for a jump fuel total of 21% of hull displacement for jump

That's sort of what I was going for, albeit a slower progression spread out over more tech levels.

Tech Level	9	10	11	12	13	14	15	16	17	18	19	20	21
Fuel coefficient	1.11	1.10	1.05	1	0.95	0.9	0.85	0.8	0.75	0.7	0.65	0.6	0.55

 

[spank]

T5 gives J7 at TL 16…it also lets you use AM for Jump fuel at TL19?18, and has the Hop drive (10 parsecs for 1 parsec of fuel) at TL 17

I've had T5 for a while, there's alot of ideas and systems there. There are a ton of useful forms too.
I haven't yet had a chance to dig into the new systems, such as antimatter.

 

[Spinward Flow]

Psst: drop tanks.

My favorite use for drop tank services (because that's the only realistic economic model that would make them available) is for double jumping point to point. That ability to double jump (first time on drop tank fuel, second time on internal fuel) is then what enables mission profiles calling for 6/8/10 parsec jumps to reach distant destinations as directly as possible.

It's why my Five Sisters Clipper (block 3 revision update) design is configured the way it is.
The ship has standard-H drives in it, which can be manufactured at TL=10.
In a 400 ton form factor, a Jump-H drive can perform a J4 in a clean configuration (no external load, internal only).
The fuel tankage onboard is 185 tons, which under regulatory clearances is enough for J3 plus 6.5 weeks of routine operations ... but since fuel is fungible (go figure, eh? ), it can alternatively be used for one J4 plus 2.5 weeks of routine operations.

And that 1J4 with 2.5 weeks is the key to its drop tank mission profile performance ... because with 4x40=160 tons of drop tank fuel the design has just enough fuel capacity for a 2J4 with 2.5 weeks, which is just enough to make a direct double jump (through deep space) from Iderati/Five Sisters to Collace/District 268 (8 parsecs) ... and from Collace/District 268 to Glisten/Glisten (also 8 parsecs) ... with about 2-3 days of fuel reserves remaining after breakout from jump at the destination (enough to reach a wilderness refueling location, assuming navigation works). Furthermore, note that Karin/Five Sisters is only 7 parsecs distant from Collace/District 268.

Sure, the revenue generating capacity of the single 30 ton cargo module "isn't that impressive" when operating the ship in a clean configuration like that, so if you have to transport "other people's cargo" at Cr1000 per ton, your revenue for the trip is going to be in the range of Cr30,000 per jump (or less under charter and/or subsidy) ... but that's if you're only offering freight services to third parties. As a speculative tramp trader, however, being able to speculate on cargo and to link Agricultural+Rich worlds with an Industrial world like that is one of the best ways to "stack the deck" in your own favor with regards to being able to buy low/sell high on speculative cargoes ... and if you get a cargo that sells better at a Non-industrial world, there's plenty of them around both ends of that long 2J4 Clipper Run between Karin or Iderati and Collace to choose from.

So the Clipper design I came up with has this curious "swing role" potential in its operations. It can be profitably operated as a J1 "jump sled" hauling third party cargo in bulk externally (most likely in standardized 20x 30 ton Modular Cutter Modules carrying 600 tons of third party "stuff" in them) ... or as a (1-2)J4 speculative tramp carrying limited quantities of high arbitrage value speculative cargoes to the most favorable destinations as quickly as possible for the most rapid turnaround times for the best profits.

Up to 8 parsecs of range with drop tank services, in a TL=10 starship design that can be supported almost ANYWHERE (including The Great Rift!) starts getting really compelling pretty quickly, despite appearances to the contrary (you just need to think like a Clipper ship captain). With deep space Calibration Points such as fuel caches, that range can be extended even farther ...

At just slightly over MCr253 per copy in volume production, it's a little pricey to buy compared to an A1 Free Trader (6.8x cost) or an A2 Far Trader (3.6x cost) or even a Type-M Subsidized Liner (1.03x cost) ... but the profit potential in a flexible cargo capacity clipper ship (capable of external cargo loading through jump) can easily outpace the rate of returns available to any of those alternatives when in the hands of a savvy operator and a competent crew. If funds start getting low, just "mode switch" from long range clipper ship running speculative cargoes to short range barge transport externally hauling third party cargoes until your cash flow recovers. Same deal if there's no speculative cargo on offer at a price point you want to buy at from your current berthing space ... simply load up on third party cargo to transport a short distance and try your luck again at the next destination. By being able to "switch modes" of operation like that, the ship design is better able to "weather the trade winds as they blow" in order to operate profitably most of the time at margins good enough to keep the crew (and investors) afloat through both good times and bad.



So even though the ship design doesn't NEED drop tanks in order to operate, being ABLE to use drop tanks (when called for) enables an order of magnitude more latitude in choices of destinations ... including being able to make 8 parsec runs across deep space in a TL=10 ship with 30 tons of revenue space. That's a decidedly non-trivial set of capabilities, as far as I'm concerned.

 

[Grav_Moped]

The non-TL-adjusted Jump Drive efficiency seems to be built into the rules, and it fits into the setting.

One good feature of it is that savvy players will dig into the math and conclude that you can't do Jump-7 or higher just because of how the rules work, instead of deciding that it was some arbitrary cap (looking at you, LBB5) that can be waived by referee fiat.

(Then you get drop tanks and it all blows up.)

 

[Grav_Moped]

And not to belabor the point, drop tanks as a work-around hides the fact that J-drives never get anymore efficient. There is no reason a civilization 7 TLs advanced from J-1 should still be burning the same amount of fuel to make that jump.
Surely a 30% increase in efficiency is achievable.

In Traveller canon, jump is "not well understood" despite being in use for thousands of years.
What is understood after thousands of years of research and development, that your jump drive is going to eat 10% of your ship's tonnage in liquid hydrogen per jump number or it's just not going to work.

Being a jump-space physicist in the OTU must be really weird.
I mean, try to figure out a rational explanation for the 10% jump fuel burn, why every jump takes literally one Solmani week (+/-10%), and why it has a range that's invariably an integer multiple of a unit of measure based on Terra's orbital radius. Oh, and why space appears to be 2-dimensional... The meta-answer is of course that it's an artificially-created universe -- but from inside that universe it'd drive scientists to alcoholism or madness.

 

[Grav_Moped]

T5 gives J7 at TL 16…it also lets you use AM for Jump fuel at TL19?18, and has the Hop drive (10 parsecs for 1 parsec of fuel) at TL 17

And that's the workaround. You can't really exploit the higher Jns until you have antimatter power.

 

[mike wightman]

I hate to point this out but in the MT and TNE universes the 10% per jump number was not the constant.

 

[Grav_Moped]

Yeah, and T5 actually enables small tweaks as well.

 

[Condottiere]

Basically, I'd say the reason you don't have long hoses pumping from external water sources is insufficient suction and throughput.