Ships Drives

[theodis]

No RCS system, or maneuvering system separate from the drive providing main thrust, is ever specified, although clearly, that function must be performed somehow, because ships can turn. Sometimes, this is even represented with an Agility number in some editions, but sometimes not. Ships also can slow down without turning... and at the same rate, no less. The only thing to conclude from these scant few facts provided by the game rules is that ships can thrust omnidirectionally. This conclusion violates the least game mechanics, and is most consistent with physics, given the game rules as a constraint.

Um, I just quoted text from FF&S that specifies all that (and there's more design detail in the rest of that section). Ships push against thruster plates, mount those appropriately on the ship to turn (most of them will be at the back).

Not quite. From "Starship Operator's Manual, p.3: "The orientation subsystem enables the ship to control its direction of flight and orientation attitude. With the advent of superdense composite materials at higher tech levels, inertial gyroscopic systems for reorientation the ship become practical. Housed at the starship's center of mass, these units are fitted in an assembly kept in near-vacuum and revolve at speeds approaching one million RPM. The tremendous inertial force generated from the device actually allows the starship to 'push itself off' the flywheel by means of a surrounding sphere of focused grav modules. Thus, the ship actualy rotates about that gyro when changing orientation."
This is but a tiny part of the description of the thruster plate drive system, addressed in length in that book. I strongly recommend getting it for any Traveller player interested in the workings of starships in the 3I.

 

[Sigtrygg]

Going through my extensive collection I see several references to the nature of maneuver drives.

Classic Traveller in both Starships and High Guard lack descriptive detail for maneuver drive until you find the one reference in Starships page 22 (Starship Combat) which states, "Ships maneuver using reaction drives, referred to as M-drive or maneuver drive." There you have it an why ships since the beginning of Traveller have nozzles. I then cross referenced Mayday for possible information. The vector system game mechanic does suggest lots of old fashion crude reaction thrusting and maneuvering.

An excellent summation but you missed the one piece of evidence that nails reaction drives to the Traveller mast - LBB5 79 edition.
Page 40 - Fusion drives as weapons: Any ship may use its maneuver drive as a weapon when at short range.

Another factioid - when Dave Nilsen was interviewed at length on CotI about TNE the topic of HEPLaR came up. Frank Chadwick wanted to return to the original intent of CT in that maneuver drives should be reaction drives.

 

[Condottiere]

Make reaction drives really cheap but thirsty.

Make thrust plates increasingly expensive the higher rating it has.

 

[Reynard]

It's good we have so many here able to sort through all reference works. I have LBB5 '80 and that page doesn't feature the fusion drive weapon. They must have thought different within a year to remove the reference. They do mention in one edition of Traveller that you do not want to have your craft pass through the exhaust wash of a fusion engine because it is highly radioactive. That means these are only used off planet and away from traffic areas such as space stations.

Creating a campaign for early Earth space exploration and exploitation during the Fire, Fusion and Steel Era, it was obvious fusion rockets would be the proto spaceflight for some time. I realized if there is regular interplanetary movement, it is going to need to be highly regulated in well spaced out flight corridors assuring all those radioactive flares won't be cooking the ships behind them and ships don't wander in the paths. No fusion ship EVER lands on Earth or near colony habitats. Even HEPlars with all that intense plasma flares should be a hazard on an inhabited world without lots of safety protocols.

 

[Condottiere]

Lots of our current warships have dual engine set ups, one for cruising, one for speed.

Add in lifters for landing.

 

[Reynard]

Mongoose Traveller tends to be very abstract about craft and ship flight and landing. That alone makes it difficult to determine if lifters made the port from earlier editions. One in the favor of lifter, however, is The Third Imperium: Starports describing the various starport types having downports with landing pads and no mention of landing strips. This is important because landing pads suggest they do not support horizontal take offs and landing on the whole, ships make vertical take offs and landings and, if only by images, these are not normally tail landings. Aft thrust systems would fail miserably.

 

[Sigtrygg]

Did you ever take a look at the low TL spacecraft design system in MT Hard Times?

A fusion rocket in that design system could easily outperform a higher TL reactionless thruster based 'standard' ship design, but it had the disadvantage of low endurance, a few hours if you were lucky.

Mind you if you had a ship with lots of space allocated for jump fuel then that became your reaction mass - which leads to the HEPlaR paradigm of TNE. I built quite a lot of ships using fusion rockets as maneuver drives, HT being among my favourite Traveller settings.

(I am not a fan of the mess DGP made trying to mash Striker with HG, and a lot of their tech explanations make Star Trek handwavium technobabble sound plausible).

 

[fusor]

Not quite. From "Starship Operator's Manual, p.3: "The orientation subsystem enables the ship to control its direction of flight and orientation attitude. With the advent of superdense composite materials at higher tech levels, inertial gyroscopic systems for reorientation the ship become practical. Housed at the starship's center of mass, these units are fitted in an assembly kept in near-vacuum and revolve at speeds approaching one million RPM. The tremendous inertial force generated from the device actually allows the starship to 'push itself off' the flywheel by means of a surrounding sphere of focused grav modules. Thus, the ship actualy rotates about that gyro when changing orientation."
This is but a tiny part of the description of the thruster plate drive system, addressed in length in that book. I strongly recommend getting it for any Traveller player interested in the workings of starships in the 3I.

It's a bit of a contradictory mess in that book. It does describe Thruster Plates as being how the ship moves, but it also says that the thrust can be vectored through the plate - 100% of the thrust is achievable if the vector is through the "back" of the plate, then it drops off rapidly so that 25% of the thrust is vectored through the sides of the plate, and then it drops off further so that 10% of the thrust can be vectored from the "back" of the plate. It also says that the plates are usually ("by convention") mounted on the aft of the ship - so even though the plates are at the back, the thrust can still be vectored sideways or even forwards.

And then it continues to talk about Orientation as you quoted.

I think that's all pretty silly though. Why put all the plates at the back of the hull when you can put them around the ship and get 100% of the thrust in those directions instead rather than a smaller percentage? It also talks about ships having to land and take off vertically because the apparently clueless designers put all the plates at the back (which again is stupid). And then the "turn on a dime" approach suggested by your quote is also redundant since you can just do that with thruster plates anyway. So I don't think their explanation really makes much sense.

Plus the DGP stuff isn't considered to be canon anyway. It does say that there's a "St Elmo's Fire"-like glow effect around the thruster plates when they're in operation though.

 

[rust2]

[From "Starship Operator's Manual, p.3: "The orientation subsystem enables the ship to control its direction of flight and orientation attitude. With the advent of superdense composite materials at higher tech levels, inertial gyroscopic systems for reorientation the ship become practical. Housed at the starship's center of mass, these units are fitted in an assembly kept in near-vacuum and revolve at speeds approaching one million RPM."

I am not aware of any official starship deck plan which shows such a system at the starship's center of mass.

 

[fusor]

I am not aware of any official starship deck plan which shows such a system at the starship's center of mass.

Yeah, none of the DGP designs even had that, so they're not even following their own material there. I think that aspect can be safely ignored since it's never appeared in any designs before or since then.

 

[theodis]

I am not aware of any official starship deck plan which shows such a system at the starship's center of mass.

Yeah, none of the DGP designs even had that, so they're not even following their own material there. I think that aspect can be safely ignored since it's never appeared in any designs before or since then.

I agree. Pity, though. I like the principle.

 

[Condottiere]

Almost the entire technological foundation in Traveller rests upon our understanding and manipulation of gravity.

So grav drives, that are optimized to function at various distances to objects with significant gravities, is alright with me.

 

[Tenacious-Techhunter]

And you can "reason" about anything, so long as it's consistent. Thruster Plates may be unrealistic, but they're consistent. You put a bunch on the back and on the bottom of the ship, you put a much smaller number elsewhere for attitude control, stick power into them and you're done.

O.K., let’s put this to the test, fusor. Your ship just crashed on a partially inhabited desert world... in the desert part. The Air Raft bay, and the raft itself, were completely destroyed. You have some injuries that can wait a few hours (but only a few) while you cobble together an improvised escape craft from the ship’s Thruster Plates, some modular stateroom walls, whatever remains of the Air Raft, and a few spare computers and consoles; fortunately, the machine shop is still running.

How much Thruster Plate is needed for lift? How much is needed for thrust? How much is needed as control surfaces? How much power plant do those total surfaces need? How much fuel is needed to make a full trip of a known length?

If this were a lawnmower or motorcycle style go-kart engine, or an electric motor, or even some very loosely specified piece of tech (Torque of X from 0 to max RPM of Y), you would be able to reason about and answer these questions, and your game wouldn’t stall out over incomprehensible nonsense. Instead, you have to half-ass everything, instead of giving your players that sweet-spot of a slim, but fighting chance.

 

[Tenacious-Techhunter]

Not quite. From "Starship Operator's Manual, p.3: "The orientation subsystem enables the ship to control its direction of flight and orientation attitude. With the advent of superdense composite materials at higher tech levels, inertial gyroscopic systems for reorientation the ship become practical. Housed at the starship's center of mass, these units are fitted in an assembly kept in near-vacuum and revolve at speeds approaching one million RPM. The tremendous inertial force generated from the device actually allows the starship to 'push itself off' the flywheel by means of a surrounding sphere of focused grav modules. Thus, the ship actualy rotates about that gyro when changing orientation."
This is but a tiny part of the description of the thruster plate drive system, addressed in length in that book. I strongly recommend getting it for any Traveller player interested in the workings of starships in the 3I.

Flywheels are great for, say, things that have to turn really slow. Honestly, on a great big freighter, they would be perfect. But for combat evasion? Hell no. There’s a reason that Kerbal has RCS thrusters, instead of just flywheels. Please do try again.

 

[fusor]

And you can "reason" about anything, so long as it's consistent. Thruster Plates may be unrealistic, but they're consistent. You put a bunch on the back and on the bottom of the ship, you put a much smaller number elsewhere for attitude control, stick power into them and you're done.

O.K., let’s put this to the test, fusor. Your ship just crashed on a partially inhabited desert world... in the desert part. The Air Raft bay, and the raft itself, were completely destroyed. You have some injuries that can wait a few hours (but only a few) while you cobble together an improvised escape craft from the ship’s Thruster Plates, some modular stateroom walls, whatever remains of the Air Raft, and a few spare computers and consoles; fortunately, the machine shop is still running.

How much Thruster Plate is needed for lift? How much is needed for thrust? How much is needed as control surfaces? How much power plant do those total surfaces need? How much fuel is needed to make a full trip of a known length?

That's what ship and vehicle design systems are for. You recalculate based on the mass of the escape craft, how much power you have available, etc, and away you go. In FF&S (for spaceships) each m³ of drive makes 40 tonnes of thrust, and then the surface area required is the total thrust in tons/200. Or use whatever design system in the Traveller edition you're using in order to calculate that. I really don't get what your problem is.

You don't and shouldn't need an engineering degree to design spaceships in Traveller. The info about how drives work could definitely do with some expansion and consolidation, but once that's done it'd be a lot easier to figure this stuff out.

 

[Condottiere]

I suspect it's one tonne of thrusters per hundred tonnes per gee point.

 

[fusor]

Please do try again.

He doesn't have to "try again" - he's quoting what was said in a book. That's what it says. If you're not satisfied with that, then that's your problem - not his.

Traveller isn't Kerbal Space Program. It's also not realistic in a lot of ways, but you seem incapable of understanding and accepting that. if you want to make a realistic scifi RPG then by all means go ahead and do that - but you seem to want to throw out everything in Traveller that makes it what it is and replace it with something else, and that just makes no sense at all.

 

[Reynard]

"Traveller is scientifically based for much of it's technology, but is not strictly speaking a 'hard science' game. Instead, it is a reasonable compromise between hard science and science fiction literature, and this shows up in the mathematics of maneuver drives among other places."
Fire, Fusion & Steel (Traveller:TNE page 69)

Even the people who created the system and made each change the canon of that edition knew this seemingly hard to understand concept. Each edition of Traveller introduces, modifies, expands and/or drops game mechanic and concepts. Each game mechanic is true and valid. The most recent editions are the latest truism. I don't remember the memo when people who know about Traveller let alone actual refs and players have the position to declare which editions and what rules are null and non-canon. I don't remember any official announcement that the game is invalid because one or two people decide the rules aren't real enough.

 

[Tenacious-Techhunter]

That's what ship and vehicle design systems are for. You recalculate based on the mass of the escape craft, how much power you have available, etc, and away you go. In FF&S (for spaceships) each m³ of drive makes 40 tonnes of thrust, and then the surface area required is the total thrust in tons/200. Or use whatever design system in the Traveller edition you're using in order to calculate that. I really don't get what your problem is.

You don't and shouldn't need an engineering degree to design spaceships in Traveller. The info about how drives work could definitely do with some expansion and consolidation, but once that's done it'd be a lot easier to figure this stuff out.

You are the one who said you could reason about these things. So do it. Put your knowledge of physics to work with what the game materials provide. Except you can’t. Because it’s nonsense that can’t be reasoned about.

The ship and vehicle design system are to make things easy; not to make things possible. If it’s not possible to reason about something like this, it’s not possible for players to adapt them by applying reason.

 

[Tenacious-Techhunter]

Please do try again.

He doesn't have to "try again" - he's quoting what was said in a book. That's what it says. If you're not satisfied with that, then that's your problem - not his.

Traveller isn't Kerbal Space Program. It's also not realistic in a lot of ways, but you seem incapable of understanding and accepting that. if you want to make a realistic scifi RPG then by all means go ahead and do that - but you seem to want to throw out everything in Traveller that makes it what it is and replace it with something else, and that just makes no sense at all.

I want to throw out everything that makes Traveller obsolete. Because, otherwise, there’s no point to trying to sell it. No one wants to try a Sci Fi game that fails to adhere to modern scientific and technological standards. Better to start from scratch with a Hard Science Fiction base, and add speculative technology in a way that breaks the least physics possible.

Regardless, you asked what sort of drive technology I want out of Traveller, so I have said so. It should be:

1. Consistent with as much physics as possible
2. Consistent with all the movement rules

So far, no Traveller Drive Technology meets 2, much less 1.