LBB2 M-Drives in LBB5: When does it help?

[AnotherDilbert]

So the key is to figure out what game/story effect you want then work backwards to a theory of antigrav that is consistent enough to maintain suspension of disbelief for you and your players.

I would do it the opposite way: Let's assume X, what effects would that have?

 

[Grav_Moped]

There is no redesign involved, you are taking one part of rating vehicle speed rule, but discarding another part.

There isn't enough information presented in the LBB3 description to apply other parts of the Striker rules. Top/cruise speed doesn't align with Striker formulae, there's no mention of avionics-limited NOE speed, and unladen mass is not stated so thrust/weight cannot be defined except when fully loaded.

Which is sort of the point of referencing the parallel construction of descriptions of the other vehicles in LBB3. Unladen automobiles and aircraft generally don't go much faster than fully loaded ones -- though they should accelerate to that top speed more quickly -- because top speed is a matter of power-to-drag ratio, not power-to-weight (all else equal). Grav vehicles (in later rules) modify that as (power not used for lift)-to-drag, but this isn't mentioned in LBB3. Granted, it may be because the writers simply didn't think of it at the time, but nonetheless, it's not included.

 

[Grav_Moped]

So the key is to figure out what game/story effect you want then work backwards to a theory of antigrav that is consistent enough to maintain suspension of disbelief for you and your players.

I would do it the opposite way: Let's assume X, what effects would that have?

These are both perfectly valid ways to approach creation of SciFi technology (and writing SF for that matter).

 

[Spinward Flow]

The fun part is when you realize that under CT Striker you can build AIRCRAFT with Grav Thrusters.

Just make sure that you have a (G-1) speed rating > stall speed and suddenly there's no need for VTOL airframe performance anymore.
Your CTOL simply uses Grav Lift+Thrust up to stall speed ... but then above stall speed you can use ALL of your G rating for thrust (because the airframe is doing the lifting).

Offer not valid on worlds with insufficient atmosphere for the airframe to make use of ...

 

[infojunky]

The fun part is when you realize that under CT Striker you can build AIRCRAFT with Grav Thrusters.

Not to forget you can build Tracked and wheeled vehicles with Grav as well, think about it, nearly a infinite Power to Weight ratio....

 

[kilemall]

The fun part is when you realize that under CT Striker you can build AIRCRAFT with Grav Thrusters.

Just make sure that you have a (G-1) speed rating > stall speed and suddenly there's no need for VTOL airframe performance anymore.
Your CTOL simply uses Grav Lift+Thrust up to stall speed ... but then above stall speed you can use ALL of your G rating for thrust (because the airframe is doing the lifting).

Offer not valid on worlds with insufficient atmosphere for the airframe to make use of ...

I’ve done those.

Problem is the rules IMO don’t cover what power to weight improvement has already been done in RL, and aren’t finicky enough to cover the very different performances in different areas atmosphere densities and composition.
For the former, I think I do something like military power tracks on a high curve of improvement tapping out at TL10, and civ engines that get more fuel/cost efficient.

For the latter, I just use what the optimum is and then degrade them badly in any other environment. You end up with highly specialized units that have an edge in their home sky, but pure grav is the cost effective overall expeditionary/merc choice.

 

[kilemall]

Not to forget you can build Tracked and wheeled vehicles with Grav as well, think about it, nearly a infinite Power to Weight ratio....

Or just a few minutes surge on batteries, enough to fly over a river, pop up for surprise attacks, or drop off a transport/small craft to float down.

 

[Spinward Flow]

Not to forget you can build Tracked and wheeled vehicles with Grav as well, think about it, nearly a infinite Power to Weight ratio....

Ah, I see you have fallen foul of a fallacy in thinking.

While "weight" can be a variable, *mass* will remain a constant ... hence why extremely massive objects moving slowly in "zero-g" can still be extremely dangerous (because inertia remains the same).

So long as you don't fall prey to the urge of thinking that Grav Thrusters let you "reduce Weight to zero" ... at which point, with a small enough divisor the Power to Weight ratio approaches infinity ... you'll be okay.

Besides, as any gearhead who loves ground vehicle racing will tell you, the limiting factor on upper end speed for a wheeled (or even tracked) vehicle isn't POWER sent to the drive train ... it's DOWNFORCE. Without sufficient downforce, excessive power to wheels (or tracks) will just make them break friction and spin uselessly, rather than powering you in a desired direction. The faster you want to go, the more downforce you need to maintain friction contact with the ground surface.

So yes, I know it's called Power to Weight and that Grav Thrusters "muck up" the WEIGHT part of that simplistic relationship ... so it's better to think of it as Power to Mass (which Grav Thrusters DO NOT modify).

Weight is just a measurement of Mass in a Gravity Well.
Mass is the constant ... while gravity can vary (especially with offworld travel and gravitic technology) ...

 

[Grav_Moped]

Besides, as any gearhead who loves ground vehicle racing will tell you, the limiting factor on upper end speed for a wheeled (or even tracked) vehicle isn't POWER sent to the drive train ... it's DOWNFORCE. Without sufficient downforce, excessive power to wheels (or tracks) will just make them break friction and spin uselessly, rather than powering you in a desired direction. The faster you want to go, the more downforce you need to maintain friction contact with the ground surface.

There are limits. You need enough downforce to maintain traction, but not much more than that -- the excess turns into rolling resistance.

 

[Grav_Moped]

Or just a few minutes surge on batteries, enough to fly over a river, pop up for surprise attacks, or drop off a transport/small craft to float down.

Pairs nicely with energy weapons.

 

[Grav_Moped]

The fun part is when you realize that under CT Striker you can build AIRCRAFT with Grav Thrusters.

Not to forget you can build Tracked and wheeled vehicles with Grav as well

Then start looking to High Guard -- you only get one hardpoint for starship-grade weapons, but how many tank turrets can you hang off of it? And mass no longer matters!

 

[Condottiere]

As long as there's local gravity, grav motors have traction.

Not all editions explicitly state that manoeuvre drives can be vectored, if at diminished values.

 

[Grav_Moped]

CT & MT agrav is just thrust, like a helicopter.
TNE contragrav is weight counteraction, like a blimp.
T4 contragrav is somewhere in between.

No. CT (LBB3) describes grav modules providing weight neutralization like a blimp, rather than using a thrust-based paradigm. Again, I'm fairly confident that they didn't have a consistent vehicle design system then.

 

[AnotherDilbert]

There isn't enough information presented in the LBB3 description to apply other parts of the Striker rules. Top/cruise speed doesn't align with Striker formulae, there's no mention of avionics-limited NOE speed, and unladen mass is not stated so thrust/weight cannot be defined except when fully loaded.

Then you can't even deduce this:

An Air/raft neutralizes its own weight and has 0.1G acceleration (regardless of local gravity*).

Striker says that 0.1 G thrust over local gravity gives a top speed of 100 km/h. If you discards the rest as incompatible, then that is incompatible too.

 

[AnotherDilbert]

No. CT (LBB3) describes grav modules providing weight neutralization like a blimp, rather than using a thrust-based paradigm.

LBB3'77, p17:
Air/Raft (8) CR 6,000,000. Also known as a flier, the air/raft relies on solid state null gravity modules for lift and propulsion. Four independent, individually replaceable modules (CR 1,000,000 each) insure a maximum of safety. Loss of one module reduces lift by one-quarter. The standard air/raft weighs 4 tons and can carry a payload of up to 4 tons including pilot and passengers. Cruise speed is 100 km per hour with unlimited range and endurance. Normally, air/rafts are open topped; the referee may allow a pressurized version or such options as gun mounts, searchlights, crash cushions or larger capacities at higher prices.

Lift and propulsion are forces, aka thrust.
Each module gives a specific (but unspecified) amount of thrust.
No magic decoupling from gravity in this description.

Again, I'm fairly confident that they didn't have a consistent vehicle design system then.

Of course not.

 

[Grav_Moped]

Then you can't even deduce this:

Striker says that 0.1 G thrust over local gravity gives a top speed of 100 km/h. If you discards the rest as incompatible, then that is incompatible too.

No, it says 0.1G discretionary thrust gives a top speed of 120kph. Design Sequence Tables booklet, p.5, GRAV VEHICLE SPEED table (left column).

 

[Grav_Moped]

LBB3'77, p17:

The '81 description differs in several respects:
- Cost is reduced from MCr6 to Cr600,000
- Doesn't say "four" null-gravity modules, just "multiple"
- Cruise speed is "100kph ... extremely subject to wind effects ... with some capability of higher speed to about 120kph"
- Mass is not stated, only the volume (4Td)

 

[AnotherDilbert]

No, it says 0.1G discretionary thrust gives a top speed of 120kph.

Okay, does that materially change the rest of my statement?

So: Striker says that 0.1 G thrust over local gravity gives a maximum speed of 120 km/h. If you discards the rest as incompatible, then that is incompatible too.

 

[Grav_Moped]

Okay, does that materially change the rest of my statement?

So: Striker says that 0.1 G thrust over local gravity gives a maximum speed of 120 km/h. If you discards the rest as incompatible, then that is incompatible too.

Yes. '81 rules give the Air/raft a 120kph top speed. (LBB3'81, p.23). This aligns with the Striker table result for 0.1G discretionary thrust.

 

[AnotherDilbert]

The '81 description differs in several respects:
- Cost is reduced from MCr6 to Cr600,000
- Doesn't say "four" null-gravity modules, just "multiple"
- Cruise speed is "100kph ... extremely subject to wind effects ... with some capability of higher speed to about 120kph"
- Mass is not stated, only the volume (4Td)

Does it say "buoyancy" or "unaffected by gravity"?

LBB3'81, p23:
Air/Raft (8) Cr600,000, 4 tons. A light anti-gravity vehicle which uses null-grav modules to counteract gravity for lift and propulsion. An airlraft can cruise at 100 kph (but is extremely subject to wind effects), with some capability of higher speed to about 120 kph. An airlraft can reach orbit in several hours (number of hours equal to planetary size digit in the UPP); passengers must wear vacc suits and interplanetary travel in an airlraft is nos possible. Range in time or distance on a world is effectively unlimited, requiring refueling from a ship's power plant every ten weeks or so. An airhaft can carry four persons plus four tons of cargo. The air/raft is unpressurized and usually open-topped.

It counteracts gravity to produce lift and propulsion = thrust.
We might perhaps conclude that the air/raft would not work outside a grav field from this, but there is no repealing gravity or special relativity implied that I can see.