R-drives vs. M-drives

[BP]

Well, most OTU ships have gravity compensators and can hover/neutralise their weight in up to 6g gravity (System dependend, some game systems have a TL scale i.e TL9 compensates 2g, TL10 3g...). So the 1g Thrust is effective thrust since the gravity pull is already neutralized. ...

I was under the impression that was to compensate for internal forces - not provide extra 'virtual' accelleration against external gravity for the entire spacecraft.

But this whole area seems rife with unneccessary logical holes... gravitics for simplistic science fiction 'propulsion' and magical lift is fine, as long as a whole framework of illogic is not hung from it... as often presented, many OTU concepts remind me of this:

 

[Rikki Tikki Traveller]

HOW exactly the M-Drive works and whether it provides negation of natural gravity (hovering) is entirely up to the Referee.

Past editions of Traveller may have provided some of the details, but MGT is back to an open interpretation.

Since there are no air breathing engines required for a starship, you can assume that the M-Drive works in an atmosphere and allows landing and take off from the planets surface.

Streamlined ships can land on a planet with an atmosphere, no extra equipment required. Since streamlined ships are not very maneuverable (flying bricks), you can reasonably assume that the M-Drive must be able to counteract the local gravity to allow control of the ship.

Whether it can "hover" is entirely up to you as the GM.

MY INTERPRETATION is that the acceleration listed for the M-Drive is independent of the local gravity field. An M-Drive with 1G of acceleration could land on the largest world out there just fine; it could also take off and immediately begin accelerating at 1G. In other words, the M-Drive negates local gravity AND provides acceleration, not one or the other.

Others have interpreted the operation of the M-Drive differently which is fine. Your Game, Your Interpretation.

 

[AndrewW]

Streamlined ships can land on a planet with an atmosphere, no extra equipment required. Since streamlined ships are not very maneuverable (flying bricks), you can reasonably assume that the M-Drive must be able to counteract the local gravity to allow control of the ship.

One could add airofins to help with manuevering.

 

[Robbo]

If a maneuver drive does cancel out local gravity then is all that stuff on vectors applied near worlds in HG optional?

 

[Rikki Tikki Traveller]

Absolutely true! BUT, per the rules they are not needed to land, so the basic streamlined hull with an M-Drive has to be good enough to land on just about any world AND skim gas giants.

To me that means that the M-Drive has to be able to land just about anywhere which means it should be able to "hover".

 

[Robbo]

If I may venture a little off thread ... the Empire Culture IMTU has Maneuver Drive technology. this was given to them by benevolent aliens when they were around TL 6-7. As a result they leaped into space without ever developing chemical rockets for their space program (missiles are another story.)

The Newcomers are Terrans at TL 12 who did not develop gravitics. They of course used rockets of all stripes, the early ones were quite pitiful. As a result they had to make every gram they lifted to orbit count.

What areas of technology would the Newcomers be ahead in because they had to make gear smaller and lighter to even get it into space?

 

[Jeff Hopper]

For R-Drives, do not for get the Kzinti Lesson:

The Kzinti lesson is, "a reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive."

Cobble up some quick-and-dirty rules for using the reaction drive thrust as a weapon. Say, like having the number of tons of r-drive is equal to a number of sandcasters in effect (this presumes that the r-drive exhaust is short ranged and disperses, but that is still a point of damage for each ton).

Why is this effective? Because every ship using a r-drive is now armed and can "attack" an opponent by turning tail and running. Even civilian craft.

 

[Robbo]

Kind of makes you want to rethink grabbing a cutlass and vacc suit and preparing to board the enemy ship! :evil:

 

[Rikki Tikki Traveller]

I think that was even mentioned in one of the old versions of Traveller.

Consider the R-Drive to be a Fusion Gun. Short Range but deadly. You would scale the drive tonnage into Bay tonnage (say at 10:1 or something since it isn't designed to be a weapon) and see what you get. Better than nothing!

 

[Rikki Tikki Traveller]

If a maneuver drive does cancel out local gravity then is all that stuff on vectors applied near worlds in HG optional?

Good point. I don't use the Vector rules, so I completely forgot about this issue!

IF you adopt my interpretation of how an M-Drive works in a gravity well, then YES you would have to ignore those rules.

If you keep those rules, then it would seem to imply that the acceleration of the M-Drive must overcome the gravity of the planet. That means that 1G of acceleration will not allow you to land/takeoff on a planet of Size 8+. In that situation, I would have Aerofins give you a bonus to your lift (uses wings to provide additional lift) so that a 1G ship could land on a larger world (up to Size 10).

To me this is a perfect example of a game rule that was not properly thought through when presented.

 

[Jeff Hopper]

I think that was even mentioned in one of the old versions of Traveller.

It was, in 1st edition High Guard.

 

[BP]

If a maneuver drive does cancel out local gravity then is all that stuff on vectors applied near worlds in HG optional?

Good point. I don't use the Vector rules, so I completely forgot about this issue!

IF you adopt my interpretation of how an M-Drive works in a gravity well, then YES you would have to ignore those rules.

If you keep those rules, then it would seem to imply that the acceleration of the M-Drive must overcome the gravity of the planet. That means that 1G of acceleration will not allow you to land/takeoff on a planet of Size 8+. In that situation, I would have Aerofins give you a bonus to your lift (uses wings to provide additional lift) so that a 1G ship could land on a larger world (up to Size 10).

To me this is a perfect example of a game rule that was not properly thought through when presented.

Well, actually it works fine - just has the limitations that were not spelled out explicitly (or perhaps even thought of).

Your rules don't work with them - but they work fine for you since you are ignoring the vector stuffs. That is also fine - it's your 'verse!

I prefer not having G-Drives cancel out gravity and simultaneously providing acceleration. Fortunately, MGT is not explicit in this area - and I would hope they continue to be! Your rules work for you - no reason to have 'official' discrepencies to contend with (aside from breaking an optional set of rules).

For simplicity I've always taken Gravitics M-Drives in Traveller to be gravitic propulsion - not anti-gravity drives. This makes it easier to contend with the fact that gravity varies dramatically wherever a ship happens to be. But compensators (for internal use) and other forms of gravitics (personal transport) 'exist' as well, so either works for me - I just prefer the added challenge and greater 'fictional' simplicity (disbelief) of not ignoring local gravity for ships.

It also matches the rules as written that I have seen.

The other advantage is that this provides certain limitations that in turn make for more interesting RP - like considering manuevering around high-G worlds - and that orbits are still desirable, regardless of constant acceleration provided by gravitics (to avoid extra delta-V and frequency of collisions as stated earlier in this thread). That, in turn allows for more exciting de-orbiting.

The part that wasn't 'properly thought through when presented' is that gravitics means no need for heat shields and orbits. As I've pointed out - this was a needless (and less desireably IMHO) oversimplification that seems to have perpetuated itself.

 

[Robbo]

I think that heat shield/no heat shield is a much more understandable distinction than streamlined or distributed hull for what ships can land. A distributed hull ship with an m-drive that can pull 6 g's an't withstand 1-2 g's laterally? How does it evade at full acceleration?
Maybe the solution is to say streamlining includes heat shielding and airfoils. Standard hulls have minimal shielding and foils and distributed hulls have no heat shielding or control foils and are unbalanced for flying.

 

[Rikki Tikki Traveller]

Another consideration about Heat Shields... They didn't exist in CT or the original HG, so comparing this option back to the original designs doesn't work either.

 

[Robbo]

I was considering using hyperdrive instead of jump drive in this setting, but the rules as written are a little unclear. They say you move 1 parsec a day per g of drive rating. Does this mean you're thrusting continuously (which would eat rocket propellant) or is it just an initial burst of speed when you enter hyperspace (which would hurt the M-drive folks as I am halving their acceleration beyond 10 diameters)?

I'm thinking of using hyperspace because the cultures in this setting have to use more fuel/propellant than in the OTU. OTOH I could use another homebrewed FTL drive.

 

[BP]

The hyperspace ('portal') mechanics in the book seems to presume a gravitic drive - so normal operations (like 2 weeks) of manuever is assumed. You would probably want to make your own rules for non-gravitic drives (and have to for vessels larger than 5,000 tons).

Sounds more like a dynamic wormhole setup to me (using 'portals' instead) - where finite amount of time is spent 'within the (higher dimensional) wormhole'.

If you are gonna use other rules as is (like trade, starship design and combat) then a system that keeps close to the current jump drive + jump fuel tonnage would keep things balanced.

 

[Robbo]

The hyperspace ('portal') mechanics in the book seems to presume a gravitic drive - so normal operations (like 2 weeks) of manuever is assumed. You would probably want to make your own rules for non-gravitic drives (and have to for vessels larger than 5,000 tons).

I could live with ships of 5000 tons or smaller. That's about the limit of practicality for deck plans for me. The rules assume speed in hyper is based on your stl drive but what if I base it on something else like the computer software or power plant rating? Either would give the R-drive folks an edge (as they have superior computing systems and power plants.) This would give them a strategic advantage if they could get their ships to move say 3 pc a day as opposed to 2 pc.

 

[BP]

It's your 'verse (TU)!

Given the changes you have made, it would seem reasonable to go outside the official box further with the FTL.

Balance with your settings, then balance with the other rules you want to keep and things will be easier, but, again its your game. I like to extend the rules myself, but I am very frugal there - since the core stuffs is often well balanced - upseting such, causes more work for me...

My settings have never been based on the OTU - only the first 8 LLBs and some supplements. My version Jump space, etc is very different from 'canon', but I have kept all the mechanics - such as parsecs and jump time limits.

 

[Fovean]

The rules assume speed in hyper is based on your stl drive but what if I base it on something else like the computer software or power plant rating?

Power plant rating seems like a good bridge... X tons of fuel for R-drive for X days of STL thrust + Y tons of fuel for P-Plant for hyperdrive & life support, computers, sensors, etc for Y days of operations...

Gives both sides advantages and disadvantages, but seems to keep the flavor you're looking for.