The Compleat LBB2 Ship Design

[AnotherDilbert]

To again quote your own worlds "It's rather obviously implied".
The "at least 288" is the giveaway. It is assumed that you maneuver to jump distance and jump, or for insystem travel you would have to calculate if your fuel would last long enough. Look at the final couple of sentences in the Travelling between Worlds on page 1 to which the 288 accelerations is a follow up.

This implies reaction drives?

LBB2'77, p1:
Constant acceleration, turn-around, and constant deceleration are assumed. It is suggested that the units used be 1000 miles, 10 minute periods, and 1 G (2000 miles per [10 minutes]2). These units are those used in the space combat section later in this booklet.

Constant acceleration for 9.6 days (w/o using fuel or propellant) implies a reaction drive?
I see that it implies a magical reaction-less drive rather heavily.

There is a complete lack of hint of any accelerate, coast, decelerate procedure that a reaction drive with limited amount of propellant or acceleration would result in.

 

[whartung]

Nowhere does agility 2 equate to 2g of maneuver as you state.

LBB 2 has no concept of Agility, it's a B5 concept that's constrained by available power and the G rating of the M-Drive.

 

[robject]

1977 Book 2 doesn't imply reaction drives. It's explicit but has no game effects or consequences. Page 22.

3. Thrust: Ships maneuver using reaction drives, referred to as M-Drive or ma- neuver drive.

Did you guys already get this? Sorry for coming in late here.

I think we all can agree though that this had absolutely no effect on Traveller rules. It was a reaction drive, but there was -zero- text on whether or not that could be used for anything other than acceleration, and no assumption that is might e.g. cause problems at starports.

But this is where High Guard 1977 got its fusion drives as weapons thing. HG1 p40.

Fusion Drives As Weapons: Any ship may use its maneuver drive as a weapon when at short range, provided the drive is operational, and fuel is available. When used, the ship attacks as with energy weapon. Automatically, the ship (all ships in the side) move to long range, regardless of initiative.

Then High Guard 1980 came along and Marc adjusted the physics of the universe away from it. Where there was a mention, it's now gone. Unless you carry the concept with you from 1977 Book 2, you won't have any inkling, and even with the 1977 rules we agree that it has -zero- effect on the game.

And then 1981 Book 2 doesn't have that little word in it at all, thus closing the gap silently.

 

[robject]

No idea. I think what they were trying to do with weapon factors was the right way to do it, it just needed a bit more thinking though. [...]

Mike can you explain a little more here? Wait wait, I'll start a new topic.

It is certainly much easier to fire each weapon type once rather than have to go to a bucket of dice or use statistical resolution as is done in HG80. Particle accelerators with a factor less than A also needed re-evaluation. And the black globe was much more similar to the Langston Field.

Now I have to go back and read HG1.

 

[AnotherDilbert]

1977 Book 2 doesn't imply reaction drives. It's explicit but has no game effects or consequences. Page 22.

3. Thrust: Ships maneuver using reaction drives, referred to as M-Drive or ma- neuver drive.

No, I at least missed that, thanks.

Reaction drives without reaction mass, curiouser and curiouser...

Perhaps some type of ion drive?

 

[kilemall]

No, I at least missed that, thanks.

Reaction drives without reaction mass, curiouser and curiouser...

Perhaps some type of ion drive?

It’s all pick your aesthetics of Clarke magic science.

 

[robject]

No, I at least missed that, thanks.

Reaction drives without reaction mass, curiouser and curiouser...

Perhaps some type of ion drive?

I think they just didn't want to run down the consequences there. They just wrote it, moved on, got to the end of the book, and said "no more delays, let's just publish this baby."

 

[AnotherDilbert]

I think they just didn't want to run down the consequences there. They just wrote it, moved on, got to the end of the book, and said "no more delays, let's just publish this baby."

Or they looked at the rocket equation and said "Hell, no!", then proceeded to set the fuel requirement to something very simple.

But they choose to have a large PP to power a small M-drive, not just a small APU to power the lights...

I have always looked at this and thought: Fusion + Grav drives + Jump = starship.

LBB2'77, p11.


Technically, a propellant-less grav drive would still be a reaction drive if it produced an equal and opposite reaction on the gravity field, i.e. pushed against the local star system.

 

[robject]

And now that I've been diving into High Guard 1, I'll notice EVEN IT has an inconsistency in that Fusion Drive As A Weapon thing, namely on page 24:

Power plant fuel is computed at 1% of the ship tonnage per power plant number; a 10,000 ton ship with power plant-6 requires 600 tons of fuel tankage for its power plant. Note that power plant fuel also provides energy for the maneuver drives. The stated fuel requirement is sufficient for four weeks of cruising (including while in jump space) before refuelling for the power plant is necessary.

Really boring, right? So here I am designing a ship in HG1.5 and I double check to make sure powerplant fuel essentially equals the powerplant number... i.e. Power 6 takes 6% and its fuel takes another 6%, one for one.

But then I focus on the text and it says

Note that the power plant fuel also provides energy for the maneuver drives.... sufficient for four weeks of cruising before refuelling for the power plant is necessary.


It's not a complete denial of the Fusion Torch thing -- after all, the rule is there plain as day -- however it is clear that that Fusion Torch thing was not an original conception of High Guard, but rather it is more likely that it was tacked on to please e.g. Frank Chadwick.

 

[mike wightman]

And yet the m-drive is explicitly a reaction drive as per LBB2.

 

[AnotherDilbert]

And yet the m-drive is explicitly a reaction drive as per LBB2.

A reaction drive that does not use noticeable amounts of fuel or propellant:

LBB5'79, p17:
Starships move through normal space using maneuver drives as described in Book 2, page 1 under Interplanetary Travel. Power for the maneuver drives is provided by the starship's power plant, which must have a drive number equal to or exceeding the drive number of the maneuver drive. ... Fuel consumption for starships is inconsequential, and assumed to be part of the power plant consumption, regardless of the degree of maneuver undertaken.

So, not a rocket, but possibly an ion drive?

 

[robject]

I forgot about 1977.

So it started as a souped up Ion drive, which on Militarized Ships can be used as a fusion weapon, but inexorably the rules gravitated away from this until here we are, post 1981.

 

[Grav_Moped]

And now that I've been diving into High Guard 1, I'll notice EVEN IT has an inconsistency in that Fusion Drive As A Weapon thing, namely on page 24:



Really boring, right? So here I am designing a ship in HG1.5 and I double check to make sure powerplant fuel essentially equals the powerplant number... i.e. Power 6 takes 6% and its fuel takes another 6%, one for one.

But then I focus on the text and it says

Note that the power plant fuel also provides energy for the maneuver drives.... sufficient for four weeks of cruising before refuelling for the power plant is necessary.


It's not a complete denial of the Fusion Torch thing -- after all, the rule is there plain as day -- however it is clear that that Fusion Torch thing was not an original conception of High Guard, but rather it is more likely that it was tacked on to please e.g. Frank Chadwick.

Per LBB3'81, fusion power starts at TL-7.
HG'80 maneuver drives (up to 2G) start at TL-7, and I wouldn't be surprised if this is a direct carry-over from '79.
....
But grav tech starts at TL-8!

So, what exactly is a TL-7 "maneuver drive" supposed to be?

 

[AnotherDilbert]

 

[mike wightman]

A reaction drive that does not use noticeable amounts of fuel or propellant:

So, not a rocket, but possibly an ion drive?

You still appear to be unable to grasp the at least 288 accelerations limit of the fuel carried.

The language used may be the issue:
"A fully fueled power plant will enable starship an effectively unlimited number of accelerations (at least 288) if necessary to use the maneuver drive during the trip."

The first part basically means you can ignore the power plant fuel use during normal operations ie travel to the 100D limit then jumping.

If used during combat however the limit is 48 hours of constant acceleration per 10 tons of fuel at 1g.

Now my reading of the rules doesn't mention fuel use beyond this 48 hours, so it is perfectly reasonable to infer that for the long interplanetary trips either burn coast burn must be used or the ship must carry more than 10tons of fuel per g.

The m-drive could indeed be an ion drive rather than a fusion rocket...

 

[AnotherDilbert]

You still appear to be unable to grasp the at least 288 accelerations limit of the fuel carried.

Yes, I grasp that you really want the M-drive to be a rocket, but that is not what I see in LBB2'77.

LBB2'77, p1:

Constant acceleration for over a week is assumed for a "Typical Travel Time".

LBB2'77, p5:
A power plant, to provide power for one trip (internal power, maneuver drive power, and other necessities) requires fuel in accordance with the formula: 10Pn.
...
The formula indicates amount of fuel in tons, and all such fuel is consumed in the process of a normal trip.

The large power plant requires fuel to power the small M-drive. The M-drive require no fuel or propellant itself. The fuel is consumed whether you spend a long time accelerating or not.

LBB2'77, p26:
There is no restriction on the number of accelerations which may be made by a fuelled ship, but the total acceleration in a turn in inches, may not exceed the size rating of the M-Drive. Should the letter class of the M-Drive (or the power plant) be reduced by combat damage, it may not exceed the revised size rating.

The power plant is just as important for the resulting acceleration as the M-drive.

The power plant burns the fuel to provide power to the M-drive that uses the power to produce thrust, hence the M-drive is not a rocket.


Yet:

LBB2, p22:
3. Thrust: Ships maneuver using reaction drives, referred to as M-Drive or maneuver drive. Their thrust is measured in Gs (Gravities) expressed as a vector of both length and direction.

So, it is a reaction drive that produces thrust apparently using negligible reaction mass, so perhaps an ion drive?


Small craft is a separate case using different rules:

LBB2, p6:
Fuel is also used by the maneuver drives of non-starships. When used in such vessels displacing under 100 tons (ship's boats, shuttles, pinnaces, etc) 10 kilograms (1/100th of a ton) of fuel is sufficient for 1G of acceleration for 10 minutes.

Small craft have no power plant fuel requirement, but a "M-drive" that consumes significant amounts of fuel directly to produce thrust. That might be an extremely efficient rocket?

With a rocket, but no power plant, it would of course be unable to mount significant energy weapons, but that's not the case is it?

1 kg/minute for ~500 kN is orders of magnitude better than what rockets can do currently. A Vega P80FW burns 88 tonnes (88000 kg) fuel to produce about 3000 kN for two minutes, so would be about 7300 kg/min to produce 500 kN.



A 5000 ton starship using the same fuel consumption (scaled up) as a 50 ton small craft would need 100 times as much fuel, or 100 kg fuel per minute = 1 ton per turn. With a power plant fuel allotment of 10 tons it would be able to accelerate at 1 G for 10 turns. It certainly would not have any "at least 288 accelerations" worth of reaction mass.

 

[mike wightman]

So we are back to what you read and infer is right, and when others read and infer they are wrong.

 

[AnotherDilbert]

So we are back to what you read and infer is right, and when others read and infer they are wrong.

I carefully avoided stating that I was absolutely correct, or questioning your intellect.

I simply quoted the book, and showed my conclusions. I find the book incompatible with m-drives as rockets.

You are of course welcome to demonstrate where my conclusions are incorrect.

 

[mike wightman]

No, you stated that I am wedded to the idea that the LBB2 drive is a fusion rocket, which I am not. It is most likely some sort of super advanced ion/plasma engine that also makes use of null grav technology

It is stated it is a reaction drive, and it therefore must use reaction mass, and since there is only liquid hydrogen or fusion products available to be that reaction mass you have to take your pick between those two. Since there is no mention of venting fusion products or having them stored and then dealt with at a starport it is a safe assumption that it is the fusion plasma products that provide the reaction mass.

As you state the fuel used is not enough to give a ship the performance stated - but since this is 77/79 a ship ton is still the equivalent to 1000kg of mass.

Either the plasma reaction mass has to be ejected at near c, or the mass of the ship has to be reduced by null grav tech.

Military ships obviously use much larger m-drives (look at the size difference between LBB2 and HG) so they can use the plasma/fusion exhaust as a weapon.

 

[robject]

I think .... that Traveller has pretty much always had this cognitive dissonance, fought internally within each member of GDW in two fronts:

• Games should have Fewer Magical Things.
• Games should Dial Back The Complexity a bit.

Those come to a head with maneuver, clearly to the point of looming up as a terrible decision within the authors themselves. The fewer magical items you introduce, the better. Traveller has several, and thrust appears to be a low-hanging fruit. Of course, thrust is only one in a cluster of useful, magical simplifications.

These little internal tug-of-wars created a product that hadn't decided. In the 80s they manifested as 2300AD, which attached to GDW's House System. So that came back to Traveller in 1993.

The separation into different kinds of thrust in Traveller wasn't until 1997.

---

And while we have decided on simplifications (and accepted the problems that gravitics gives), HEPlaR is valid (and we've accepted the problems that gives as well).