Alternative to the 1000D M-Drive limit

[MasterGwydion]

Hey all! Just an idea I had for greater variations in M-Drives.

D limit for M-Drives as a function of their M-number. (200Dx"Thrust Potential Lost for increased M-Drive sensitivity") This is how far away from a Gravity Well, that the ship can operate. This is built into the design when the M-Drive is built and cannot be changed later. Installing a whole new M-Drive would be required.

The "Remaining M-Thrust Potential" is used as the actual M-Drive number for performance, power consumption, etc.

Total Drive Potential is the M-3 of the drive on the chart in Highguard.

Use the total Drive Potential number for finding required TL, size of the drive, and the drive's Cost, as per the chart in Highguard.

So at TL-16 with an M-drive/10 you could be either;

Zipping around at Thrust/9, but limited to the 200D limit or,
You could be slow-boating it at Thrust/1 all the way out to 1,800D before your performance degraded to 1% of normal Thrust.

At a more modest TL-12 and a M-Drive/7 you could either;
Zip around at Thrust/6 and be limited to 200D or,
slow-boat it at Thrust/1 all the way out to 1,200D.

TL-10 and a M-Drive/3?
Thrust/2 within 200D or,
Thrust/1 within 400D.

What do you guys think of this idea? How do you think it would change the game?

 

[Arkathan]

I've never used the 1000D limit. I don't recall it existing in the core CBT books.
Use of that limit makes the continuous thrust travel calculations irrelevant, since your engine performance degraded as a function of distance from the primary. It also seems a bit silly when you consider the direction of the thrust being used. Not much better than a sail.

I always used anti-grav vehicles as bound to planetary orbits and M-Drives as a Niven Known Space Reactionless Drive, generating gravitic thrust against the ship's thrust plate, perhaps in a fashion similar but opposite to the manner in which gravitic deck plating works.
The 1000D limit would tend to make scavenging fuel from hulks when you get caught in a jump eddy of the Abyssal Rift rather problematic unless you have a fusion rocket tacked on.

 

[Condottiere]

Consider them as plot devices, which either the players chose to limit their wandering about, or expands their possible paths.

The more you squeeze them, the more microjumps start looking attractive.

 

[MasterGwydion]

Consider them as plot devices, which either the players chose to limit their wandering about, or expands their possible paths.

The more you squeeze them, the more microjumps start looking attractive.

I was thinking that this would make micro-jumps more of a thing for perishable or time-sensitive in-system cargo as well as passengers. Even moreso, cut the fuel cost by 90% for "in-system jumps", say... within the Oort Cloud or so. Making micro-jumping a viable economic choice, as opposed to drone ships for repeating cargo runs in system, or calculate the ship's trajectory, accelerate all of the way to the limit of you M-Drive, coast across the "dead-space" in the middle and decelerate at the next gravity well.

 

[Geir]

Mongoose Traveller doesn't directly address the 1000D M-drive barrier, but hints around at it. Some of the disadvantages for M-Drive definitely shows an intent, and the Deep Space Maneuvering system introduced in Deepnight Revelation implies that a limit does exist without specifying exactly where it is. 1000D is inconveniently just short of Saturn's orbit, so it would put everything beyond in the much-harder-to-get-to realm where a microjump might make sense. The revised 'history' of early Terran Jump Drive usage seems to imply such a conundrum.

T5 definitely uses the 1000D M-Drive barrier. All of the grav-type drives have some sort of limits; for G-Drive it's 10D and for lifters it's 1D - we assume above the surface, but perhaps from the center, making it 0.5D from the surface - and NAFAL, oddly 51 weeks or 1/8 light-year, though there is a 'Thruster' type of reactionless drive as well which is also called the Dean Drive. So choices for everyone.

My handwavium assumption with M-drive and its siblings is that it actually 'steals' energy from a gravitational field in some manner. Think of a gravity slingshot which uses no fuel or an Oberth Maneuver which uses less fuel than normal to achieve a bigger change in velocity. These effects are essentially stealing gravitational energy from the massive object they're using to for that extra push. Don't ask me how the M-Drive does that (mumble, mumble, spinning condensate quantum effects, mumble) - if I knew how that would work, I'd be talking to a patent attorney, not typing in a Traveller forum.

But all the 'literature', so to speak, implies a sudden drop-off to near zero once a limit is reached. Phase change - 'crystalizing' the process beyond a threshold - maybe. The gradual decline would make sense, but I think it's based on a different pseudo-science than is intended with the OTU.

 

[Condottiere]

I think it's a push and/or anchor.

If it's independent of a local gravity well, it's plain thrust, possibly by recreating a focussed directional gravity field.

Whereas what we would consider lifters and vehicle gravitational motors would be a general field effect, rejecting gravity.

 

[Sigtrygg]

A 1000D m-drive limit invalidates the Traveller Adventure, there is a crucial scenario that takes place in empty hex deep space which is not possible with the 1000D fudge.

 

[MasterGwydion]

A 1000D m-drive limit invalidates the Traveller Adventure, there is a crucial scenario that takes place in empty hex deep space which is not possible with the 1000D fudge.

That is what R-Drives are for. They use fuel, but can be operated outside of a gravity field. M-Drive works like wifi. No wifi, you're out of luck. R-Drives work like a Ham Radio, can be used no matter where you are.

Again, just My 2 cents. So if your players play through the Traveller Adventure and do not take a ship with an R-Drive, then strand them in space. Poor planning in Traveller gets people killed...lol... and so do misjumps...lol...

 

[Reynard]

R-drives have their own serious limitation, extremely short ranged. Even if you sacrifice a lot of internal space for fuel, you still can't go very far. Probably the closest thing to Traveller hard sci-fi.

 

[Sigtrygg]

Have you read the Traveller Adventure at all (the definitive classic traveller adventure which was also reprinted as a MgT 1e adventure)? The players are the crew of a standard subsidised merchant - no "reaction drive" and yet can take part in the battle scenario set in the empty hex deep space.

 

[MasterGwydion]

Have you read the Traveller Adventure at all (the definitive classic traveller adventure which was also reprinted as a MgT 1e adventure)? The players are the crew of a standard subsidised merchant - no "reaction drive" and yet can take part in the battle scenario set in the empty hex deep space.

No. I have not, so take My opinion as an uninformed opinion, but it seems to Me that, in that particular adventure as written, the Travellers should have all died. lol

 

[Arkathan]

A 1000D m-drive limit invalidates the Traveller Adventure, there is a crucial scenario that takes place in empty hex deep space which is not possible with the 1000D fudge.

That is what R-Drives are for. They use fuel, but can be operated outside of a gravity field. M-Drive works like wifi. No wifi, you're out of luck. R-Drives work like a Ham Radio, can be used no matter where you are.

Again, just My 2 cents. So if your players play through the Traveller Adventure and do not take a ship with an R-Drive, then strand them in space. Poor planning in Traveller gets people killed...lol... and so do misjumps...lol...

I think the point was that R-Drives weren't needed in CT. The 1000D limit is a relatively recent development, and is counterintuitive. An anti-grav vehicle is dependent upon pushing against a gravity field, but an M-Drive is more like grav deck plates than an anti gravity unit. The thrust is generated by the drive and directed against the thrust plate. There are no calculations for the degradation of drive efficiency as a function of gravity well depth. So are we to believe that the drive hums along at rated capacity until it runs off a cliff and suddenly doesn't work? With the logic of the 1000D limit, people should be floating through the corridors in spite of having gravitic deck plates.

 

[MasterGwydion]

A 1000D m-drive limit invalidates the Traveller Adventure, there is a crucial scenario that takes place in empty hex deep space which is not possible with the 1000D fudge.

That is what R-Drives are for. They use fuel, but can be operated outside of a gravity field. M-Drive works like wifi. No wifi, you're out of luck. R-Drives work like a Ham Radio, can be used no matter where you are.

Again, just My 2 cents. So if your players play through the Traveller Adventure and do not take a ship with an R-Drive, then strand them in space. Poor planning in Traveller gets people killed...lol... and so do misjumps...lol...

I think the point was that R-Drives weren't needed in CT. The 1000D limit is a relatively recent development, and is counterintuitive. An anti-grav vehicle is dependent upon pushing against a gravity field, but an M-Drive is more like grav deck plates than an anti gravity unit. The thrust is generated by the drive and directed against the thrust plate. There are no calculations for the degradation of drive efficiency as a function of gravity well depth. So are we to believe that the drive hums along at rated capacity until it runs off a cliff and suddenly doesn't work? With the logic of the 1000D limit, people should be floating through the corridors in spite of having gravitic deck plates.

I would have thought that things like deck plates, "generate" an artificial gravity field, as opposed to M-Drive that use existing gravity fields for thrust, pulling or pushing themselves along.

 

[Andrewmoreton]

I think that something like the 1000D limit is needed to prevent relatavistic bombardment of worlds by any nutter who can buy a starship. But it does make deep space refuelling more challanging to fit into stories , its ok if they have an anchor of some sort but without that its an issue.

 

[MasterGwydion]

I think that something like the 1000D limit is needed to prevent relatavistic bombardment of worlds by any nutter who can buy a starship. But it does make deep space refuelling more challanging to fit into stories , its ok if they have an anchor of some sort but without that its an issue.

Remember that you M-Drives still work in Deep Space, just at 1% efficiency, so hope you arrive exactly on target in Deep Space or it may take a while to get to your fuel depot. lol

 

[Geir]

Have you read the Traveller Adventure at all (the definitive classic traveller adventure which was also reprinted as a MgT 1e adventure)? The players are the crew of a standard subsidised merchant - no "reaction drive" and yet can take part in the battle scenario set in the empty hex deep space.

A great classic book, though it does also include my candidate for Worst Traveller Session Ever - Zilan Wine, a.k.a. Bureaucratic Dungeon Crawl, a.k.a. Permit Treasure Hunt.
But two points:
One: Canon is ever evolving - the first version of High Guard assumed fusion drives for M-Drive, and New Era assumed plasma thrusters, so M-drive has, um, evolved-devolved-changed.
Two: In deep space, all of the participants of any encounters would be at the same disadvantage without a reaction drive, so chugging around at 1% efficiency (galactic background gravity field?) can be fudged. The original text even says "In some cases, the referee may want to ignore detailed representation in the interest of avoiding repetition or saving time."

 

[Arkathan]

That is what R-Drives are for. They use fuel, but can be operated outside of a gravity field. M-Drive works like wifi. No wifi, you're out of luck. R-Drives work like a Ham Radio, can be used no matter where you are.

Again, just My 2 cents. So if your players play through the Traveller Adventure and do not take a ship with an R-Drive, then strand them in space. Poor planning in Traveller gets people killed...lol... and so do misjumps...lol...

I think the point was that R-Drives weren't needed in CT. The 1000D limit is a relatively recent development, and is counterintuitive. An anti-grav vehicle is dependent upon pushing against a gravity field, but an M-Drive is more like grav deck plates than an anti gravity unit. The thrust is generated by the drive and directed against the thrust plate. There are no calculations for the degradation of drive efficiency as a function of gravity well depth. So are we to believe that the drive hums along at rated capacity until it runs off a cliff and suddenly doesn't work? With the logic of the 1000D limit, people should be floating through the corridors in spite of having gravitic deck plates.

I would have thought that things like deck plates, "generate" an artificial gravity field, as opposed to M-Drive that use existing gravity fields for thrust, pulling or pushing themselves along.

Grav vehicles repel gravity. M-Drives and deck plates generate their own fields. In the case of a ship, it generates force against a Thrust Plate.
There is a reason you have a rating in G's. That's what the engine produces. The thrust is constant regardless of where you are in relation to a gravity well. If the 1000D limit was intended to be a well thought out game mechanic thing, the interplanetary travel times would not be calculated in G's, since the acceleration would not be a constant G rating. It would vary with depth in field. To get 2 G at 1 AU in Sol orbit, your drive would be capable of 8G at .5 AU and .5 at 2 AU. Clearly, this is not the case. (Based on rough estimates of radiation calculations, radiation is constant out to around .25-.3D, decreases at slightly less than linear out to .5 D, then acts as a point, and varies with the inverse square of the distance from there. i.e. Doubling distance quarters field strength.
Now, clearly, there is sufficient gravitational forces in play to keep the Oort Cloud in orbit around the star out past more than one light year (as much as three light years - nearly a parsec).
It truly sounds like a past developer wanted a reason to justify the inclusion of reaction drives past TL 9.

 

[Arkathan]

Have you read the Traveller Adventure at all (the definitive classic traveller adventure which was also reprinted as a MgT 1e adventure)? The players are the crew of a standard subsidised merchant - no "reaction drive" and yet can take part in the battle scenario set in the empty hex deep space.

A great classic book, though it does also include my candidate for Worst Traveller Session Ever - Zilan Wine, a.k.a. Bureaucratic Dungeon Crawl, a.k.a. Permit Treasure Hunt.
But two points:
One: Canon is ever evolving - the first version of High Guard assumed fusion drives for M-Drive, and New Era assumed plasma thrusters, so M-drive has, um, evolved-devolved-changed.
Two: In deep space, all of the participants of any encounters would be at the same disadvantage without a reaction drive, so chugging around at 1% efficiency (galactic background gravity field?) can be fudged. The original text even says "In some cases, the referee may want to ignore detailed representation in the interest of avoiding repetition or saving time."

One of the old books has a reference to reaction drives, but CT Book5 High Guard says:
"Tech level requirements for maneuver drives are imposed to cover the grav plates integral to most ship decks,
and which allow high-G maneuvers while interior G-fields remain normal."

 

[MasterGwydion]

I think the point was that R-Drives weren't needed in CT. The 1000D limit is a relatively recent development, and is counterintuitive. An anti-grav vehicle is dependent upon pushing against a gravity field, but an M-Drive is more like grav deck plates than an anti gravity unit. The thrust is generated by the drive and directed against the thrust plate. There are no calculations for the degradation of drive efficiency as a function of gravity well depth. So are we to believe that the drive hums along at rated capacity until it runs off a cliff and suddenly doesn't work? With the logic of the 1000D limit, people should be floating through the corridors in spite of having gravitic deck plates.

I would have thought that things like deck plates, "generate" an artificial gravity field, as opposed to M-Drive that use existing gravity fields for thrust, pulling or pushing themselves along.

Grav vehicles repel gravity. M-Drives and deck plates generate their own fields. In the case of a ship, it generates force against a Thrust Plate.
There is a reason you have a rating in G's. That's what the engine produces. The thrust is constant regardless of where you are in relation to a gravity well. If the 1000D limit was intended to be a well thought out game mechanic thing, the interplanetary travel times would not be calculated in G's, since the acceleration would not be a constant G rating. It would vary with depth in field. To get 2 G at 1 AU in Sol orbit, your drive would be capable of 8G at .5 AU and .5 at 2 AU. Clearly, this is not the case. (Based on rough estimates of radiation calculations, radiation is constant out to around .25-.3D, decreases at slightly less than linear out to .5 D, then acts as a point, and varies with the inverse square of the distance from there. i.e. Doubling distance quarters field strength.
Now, clearly, there is sufficient gravitational forces in play to keep the Oort Cloud in orbit around the star out past more than one light year (as much as three light years - nearly a parsec).
It truly sounds like a past developer wanted a reason to justify the inclusion of reaction drives past TL 9.

Grav Vehicles repel gravity. M-Drives pull or repel gravity depending on if you are travelling to o away from a gravity well. My only thought on this is that if M-Drives generate their own field, then the 1000D limit wouldn't exist. Deck plates seem to be the only one of them that generates its own gravity field.

The arbitrary point of 1000D is just a game mechanic to simplify the complexity that you so accurately described.

 

[Condottiere]

I think less Tee Five revision, more Marc Miller retcon.

How many planets are in Firefly, twenty seven? You can have a rich campaign just bustling around a large system, as long as it's fairly easy to get to the next town of the week.

You could start graduating out in decimal steps greater ranged gravitational based drives, but there are limits as to how this benefits gameplay.

It's pretty much as to how I wouldn't penalize a budget jump drive with a fifty percent greater minimum distance, if I had a choice, because in some systems, that could really screw up your itinerary.

If the Manoeuvre drive gets revised, perhaps it's time to finesse the jump drive algorithms somewhat as well.