They Started to Fix LBB2 Fuel Burn...

[Grav_Moped]

I can see why they threw up their hands and let it go -- the easy fix requires breaking most designs with more than 1G maneuver.

The easy fix is to use the average fuel requirement for all ship sizes in LBB2, which comes out to a little over 5% per Pn (10% at 100Td, 1% at 1000Td, 0.2% at 5000Td). This makes the Type S more plausible and doesn't affect the Type A or A2. It makes the upgrade to the Type R (J2/2G) that the standard hull discount implies, nonviable (you can do it, but it chops 20Td out of the 150Td remaining cargo that RAW leave you after the upgrade). It ruins the Type M Liner by wiping out almost its entire cargo capacity, and breaks the Patrol Cruiser and Mercenary Cruiser hard.

The slightly more complex fix is to keep the 5% per Pn but only require Pn=Gs (as per '77 rules) but add a requirement for a minimum Pn of 1. This saves the Subsidized Liner and upgraded Subsidized Merchant (it's J2/1G though), but both Cruisers are still whacked.

Dropping the fuel requirement lower (someone called this the "High Guard Fix" -- 1% per Pn) can save all of these designs but starts skewing High Guard designs badly, since it makes LBB2 drives much more competitive in the LBB2 size range -- limited Pn (capped at 6) means more armor to compensate for lost agility, and the low available power means missiles and sandcasters dominate. Not quite what HG was trying to accomplish there...

In the end, T5's solution was "Half the High Guard Fix" (2% per Pn, modified by TL-stage effects). Close enough, maybe?

 

[whartung]

Funny thing, Chadwick thinks the HePLAR isn't efficient enough. He feels that with the latest information, we can make something that's (I think) up to 50 times better, which makes HePLAR almost equivalent to the M-Drive for all practical purposes.

It's been a while, he uses the drives in his Sci Fi books (which I have not read).

 

[Grav_Moped]

Funny thing, Chadwick thinks the HePLAR isn't efficient enough. He feels that with the latest information, we can make something that's (I think) up to 50 times better, which makes HePLAR almost equivalent to the M-Drive for all practical purposes.

It's been a while, he uses the drives in his Sci Fi books (which I have not read).

Which is pretty cool from an aesthetic perspective, but it results in Scout/Couriers having a maneuver drive that's two factor 2 plasma gun batteries...

... and capital ships propelled by spinal-mount-class fusion guns.

Messy.

 

[whartung]

but it results in Scout/Couriers having a maneuver drive that's two factor 2 plasma gun batteries...

Not necessarily.

On a planet, perhaps, sure. Nothing says "Adventure" than lighting a huge grass fire that consumes the entirety of the Great Plains when you touchdown on a pristine world.

That said, when it comes to combat, it's easy to pull out your handy HP Pocket Hand Waver and assert that fusion drives don't have the magnetic containment systems that turns fusion and plasma in to "bolts" that can actually be accurately aimed and retain integrity and effectiveness over long range.

Consider, a flame throwers range is only a 100 or so feet.

This is was distinguishes a thruster from a "gun".

At "space" engagement ranges, thrusters are ineffective.

 

[willtron3030]

Nothing says "Adventure" than lighting a huge grass fire that consumes the entirety of the Great Plains when you touchdown on a pristine world.

Or a coal seam fire that burns for millennia. [link goes to Science Alert article about one such fire in Oz]

 

[TJP]

Funny thing, Chadwick thinks the HePLAR isn't efficient enough. He feels that with the latest information, we can make something that's (I think) up to 50 times better, which makes HePLAR almost equivalent to the M-Drive for all practical purposes.

Whoa, this is the first time I hear that the HEPlaR drive isn't efficient enough! Back in the day there was a lot of pulling of hair and gnashing of teeth about the HEPlaR being way, way too efficient. Being as magical as a reactionless drive, almost. I've done a few back of an envelope calculations and don't really see them as too over the top efficient, but I sure don't see them as not efficient enough either. Curious about what this 'latest information' is that says we can surpass the (theoretical) HEPlaR's efficiency by 50 times.

By Chadwick, you mean Frank Chadwick (of GDW), right?

 

[whartung]

By Chadwick, you mean Frank Chadwick (of GDW), right?

Yes.

He did a presentation at a convention in San Francisco that they posted, so I listened to it. I can't find it anymore.

As I understand it, it's the tech in his book "Chain of Command", which I have not read.

 

[TJP]

Ah, okay. Thanks for the info. I'll do some digging about the book's setting.

 

[Grav_Moped]

Crosslinking myself from a severely drifted thread.
(This post in particular.)

Going back to the first post in this thread:

That's the key. Even starships/non-starships had a fixed kg-per-burn (not kg per-G*tons) consumption rate in the first edition. And it's an explicit link since the Jump Drive didn't need the power plant for operation.

That's where the 10 tons per Pn (rather than percent of hull tonnage per Pn) power plant fuel requirement came from: Starships and small craft both worked that way in the first edition, though power plants from the LBB2 Drive Table had a higher flat kg/burn fuel consumption rate (about 35kg/G-turn).

I was both right and wrong here.

Small craft and starships, and non-starships (100Td+) all had the same flat 10kg/g-turn) rate.
The reason starships had a mandatory 10Td per Pn requirement is that at 10kg/g-turn, 10Td per Pn provides almost exactly (94%) one week of full acceleration. Starships don't need more than 1 week of continuous acceleration, because any trip that would take longer than a week in normal space could be shortened to one week by jumping. Trips requiring longer continuous acceleration (wilderness refueling with jumps from one gas giant to the next) were handwaved by averaging them with the ones that required far less than a week (size 8 to size 8 -- one day at 1G to the 100D limit at each end) through declaring that all of the power plant fuel was expended every trip.

Non-starships required 10kg*Pn*g-turn (which works out to about 1.44Td per 24 hours) instead of 10Pn because they can't shorten a trip by jumping and need fuel for the whole normal-space burn-flip-decelerate trip. Since the 10Pn allotment only supported seven days of maneuver operation, it was clearly insufficient for interplanetary trips that could last far longer than that.

Small craft often didn't even need the whole 10Pn (or in their terms, 10,000kg/g) because as presented in LBB2'77, they were conceptualized as interface craft for starships, rather than as interplanetary craft. In that role, flights would have been measured in hours, not days or weeks.

 

[Grav_Moped]

Small craft and starships, and non-starships (100Td+) all had the same flat 10kg/g-turn) rate.
The reason starships had a mandatory 10Td per Pn requirement...

And of course this says nothing directly about the 1-month mandatory fuel allocation rule in LBB2'81.

Though it might be possible to infer a few things from it.

The first is that the fuel allocation was originally intended to serve for up to two weeks (one of which was in Jumpspace) and also meant to be handwaved out to four-plus weeks (mainworld to gas giant, then jump to gas giant, then gas giant to destination mainworld).

The 1-month specification in High Guard (both versions) turned the handwave into a hard limit and drastically slashed nonstarship fuel requirements. It was subsequently backported into LBB2'81.

Anyhow.

LBB2'77 power plant fuel is all about maneuver. No other energy draw even comes close.

Fast forward to '81 with the High Guard fuel use paradigm in place, and it's really about maintenance power. Maneuver fuel use is (by declaration) a trivial fraction of total consumption -- but then, so is fuel use to power weapons! A double laser turret draws as much power as 2G acceleration for a 100Td ship, but there really isn't a plausible case for running a laser 24/7 for a month straight -- so it's not the weapons causing the fuel consumption either.

Then you bring in the TCS power-down rule that can drop fuel use by more than 80% (Pn-6 running at Pn-1) and it all stops making any sense whatsoever.

Now what?

 

[infojunky]

While I haven't closely looked at the numbers the fuel use from Beltstrike is starting to look good.

 

[Grav_Moped]

While I haven't closely looked at the numbers the fuel use from Beltstrike is starting to look good.

Haven't really looked at Beltstrike's numbers, but I'm not going to argue.

I like the notion from '77 that maneuver costs fuel, but not much else does.
I also think it approaches my house-rules that exploit the TCS powerdown rules as well as my take on the 1-month allocation as being a best-practice based on the outlier cases of flights with wilderness refueling rather than an absolute, arbitrary rule.

I'm also wondering about a possible interpretation of the '81 (and HG) Pn=Jn rule to roll it back toward the '77 rules: the required power plant is needed, but not the power plant fuel for the week in jump, because that's included in the jump fuel allocation. It doesn't work out at the low end (Size A drives with LBB2 fuel use rates would use all the jump fuel for the power plant, leaving none for jump), and drop tank rules (whole load gets burned up-front) strongly suggest it can't be that way. But it's an interesting thought.

Might work with MgT though...

And the T5 2% fuel requirement starts to make a little more sense. The 1% from HG seems a little out of step with LBB2 on the low end (sub-1KTd).

 

[mike wightman]

So what is fuel for? Does it just power the ship via a fusion reaction in the power plant or is it also used as reaction mass?

Up until HG80 a little fuel was used as reaction mass, but still nowhere near the amount that is required if that is all there is going on.

So where do all those GW go?

Maneuver - a reactionless M-drive turns 'energy' into movement, is that energy transferred as electricity or something else?
Environment control - we know what the real world numbers are for power consumption on the ISS, so we can have a stab at this with the exception of...
Gravitics - maintaining the artificial gravity plates and the acceleration compensation.

Along comes HG80 and we learn that 1EP will power a laser continuously, provide a 100t ship with an agility of 1 and so by deductive reasoning the M-drive requires 1 EP per g per 100t.

We later learn from TCS that a power plant may be reduced to power plant 1 to maintain vital ship systems and conserve fuel.

Finally Striker gives the definition of the EP to be 250MW.

 

[Condottiere]

I think, so far, the only practical use of real world energy output is to figure out how many households can be powered by ye local neighbourhood fusion reactor.

 

[mike wightman]

I agree.
It is pretty easy to use energy and power formulae to calculate real values for ship performance - or at least it would be if it were based on mass rather than volume.

So back to my list - movement - environment - gravitics

Of these three the only 'real' unknown is gravitics.

Somehow gravitics allows far less energy from fuel fusion to be turned into the kinetic energy of the vessel. It is also the only unexplainable in the list. We do not know, and no one has ever attempted, to explain how null grav modules, M-drives, artificial gravity and acceleration compenstaion actually work. Describe yes, handwavium explanation, nope.

 

[mike wightman]

Now since we are looking at LBB:2 we can safely ignore all Traveller iterations that came after and concentrate on the stuff we are told in the CYT corpus - LBB2 77, 81, TTB, ST, HG79, HG80, Striker, TCS, Beltstrike.
Anything missing from that list?
And a couple of thoughts - is the EP to 250MW supposed to be accurate foe all uses or just for weapons?
Why can't a BB power plant power down to 1EP rather than to #1?

 

[Condottiere]

Gravity manipulation, will either be creation or neutralization.

Or possibly, ju jitsu.

 

[Grav_Moped]

So what is fuel for? Does it just power the ship via a fusion reaction in the power plant or is it also used as reaction mass?

The way I see it ('77 only) is that the maneuver drive is the rocket exhaust bell attached to the power plant.
Actual electrical generation is a secondary matter since the actual power demands are trivial compared to acceleration.

The Jump Drive does its own thing as far as I can tell in '77. Maybe it uses the power plant output (burning some of the 10%Td jump fuel) to hold jumpspace at bay for a week, maybe it doesn't).

HG'79 introduces the EP economy, and while that works brilliantly for the new abstract combat system, it makes understanding where the fuel actually goes, kind of problematic because the maneuver drive gets described as explicitly a grav drive without a reaction-drive component.

LBB2'81 pretends it doesn't do EPs, except in small craft.

Up until HG80 a little fuel was used as reaction mass, but still nowhere near the amount that is required if that is all there is going on.

So where do all those GW go?

That's what I'm asking! The rules pretty much go out of their way to eliminate each thing that it could be going toward.

 

[mike wightman]

You mean HG80 for EPs?

To paraphrase an old rpg saying

my hat of EPs no no limit

They are useful in a way for design, but the scale is a bit suspect. 1 EP is the energy required for 1 beam laser but is also the amount of energy needed to move a 100t ship at 1g, and let's not look too closely at the black globe rules for energy equivalence. They are also almost always ignored during an actual HG80 game because it is a pain in the behind to rack the EP changes of the ships in a squadron as they take damage.

The EP economy has the M-drive breaking thermodynamics.

 

[Grav_Moped]

You mean HG80 for EPs?

79 didn't have EPs? I knew it either didn't have agility, or at least that agility wasn't important.
I really should get a copy (and one of LBB2'77) for reference...

The EP economy has the M-drive breaking thermodynamics.

Well, it already did to begin with. EPs just made it a lot worse.