Fractional drives

[aramis]

From the initial conception of maneuver drives, they're a scalable block with a constant 1Td hole cut out of the center, that's tied to the power plant. Like an exhaust nozzle...

Once the flavor text changed to "reactionless thruster" from "fusion torch drive," I'm not sure how to explain the LBB2 M-drive tonnage progression.

Inverse scale efficiency, aka, scale inefficiency.

For example, gasoline engines only get so big per cylinder and so much total torque and RPMs before the efficiency curve drops off due to needed masses for the forces involved. But, below a certain point, they also drop off in mass per kgf.

I never experienced Traveller as reaction drives until TNE came out, and two campaigns of that was enough for me... plus, I abandoned HEPlaR after the first one. I started in fall '83... with CT 2E (DT) and 2.1E (TTB)

 

[Spinward Flow]

For example, gasoline engines only get so big per cylinder and so much total torque and RPMs before the efficiency curve drops off due to needed masses for the forces involved. But, below a certain point, they also drop off in mass per kgf.

As any truck driver will tell you ... there is no replacement for displacement ... or at least there won't be until Cyvertrucks and Tesla Semis start taking over the trucking industry.

 

[Condottiere]

Fire Fusion Steel had efficiency scales for motors.

 

[aramis]

As any truck driver will tell you ... there is no replacement for displacement ... or at least there won't be until Cyvertrucks and Tesla Semis start taking over the trucking industry.

My buddy the ship's engineer notes that the drives he works with do better with more cylinders than bigger ones, because once you get to cubic meters per cylinder, the deflagration will only permit a given rate of head movement, well under what the strength of the cranks and rods can be scaled to handle. when a cylinder head is 1.5m across, you need either a uniform pressure-based detonation, or to have multiple ignition sources spaced so as to account for a 30-50 cm/sec flamefront...

Most devices, due to the square law for strength (the strength of a structural member scales to the cross-section area. which is the square of the uniform multiplicand) and the cube law for mass and volume (which are a cube of the uniform multiplicand), do not increase in efficiency indefinitely. There's an optimal range, with both upper and lower bounds.

Oh, and Volvo's delivering new electrics: https://www.volvotrucks.com/en-en/trucks/renewable-fuels/electric-trucks.html
Mack: https://www.macktrucks.com/trucks/lr-electric/
Freightliner, too: https://www.freightliner.com/trucks/ecascadia/

 

[Silverhawk]

Yea, but, still, the "formula" isn't reality in anyway, shape, or form.

There are other factors in powerplant design that makes having an "infinitely scalable" design not workable. There are simply engineering breakpoints that kick in to place.

I can't speak to large freighters, but most powerplants here on Terra Firma are not scalable. The vessel is built around the available plants, and if it's not enough, they gang them up.

This concept is similar to adding cylinders to the motor (2-4-6-8), or rotors in a Rotary motor.

But even still, while there are V-12, even V-16 motors, they're more a novelty.

It's a lot of trouble to engineer these things, and there's only real economy in scaling the operations.

Large diesels such as those used in locomotives are generally V-12 and V-16 depending on horsepower required. There was a model built by the Electro Motive Division of General Motors that had a V-20 diesel engine but it was something of a fuel hog which combined with the fuel shocks of the 1970's impacted its sales.

 

[kilemall]

Large diesels such as those used in locomotives are generally V-12 and V-16 depending on horsepower required. There was a model built by the Electro Motive Division of General Motors that had a V-20 diesel engine but it was something of a fuel hog which combined with the fuel shocks of the 1970's impacted its sales.

Originally there was a power race where the goal was to get 2 locomotives to do the work of 3 of the previous generation.

More powerful diesels and turbochargers were used.

There were two engine monsters such as the Centennials and gas turbine engines. Later, attempts to deploy 6000 HP engines, but aforementioned teething problems plus lack of modularity having so much tied to higher horsepower has meant high end power tends to be 4100-4400 HP.

The direction since has been to get V16 power out of V12 engines thus using less fuel for the same work, and improve performance aspects such as adhesion control and smart axles.

The functional Traveller equivalency would be more power plant fuel efficiency and higher J and M drive ratings out of less power input.

 

[whartung]

The functional Traveller equivalency would be more power plant fuel efficiency and higher J and M drive ratings out of less power input.

The functional gaming equivalency would be smaller drives, or a more efficient J drive (i.e. 8% volume per jump instead of 10%).

The fuel efficiency problem with M-Drives is mostly non-existent, they require so little (i.e. just raw fusion power) as is, there's little motivation for a more fuel efficient drive.

But smaller, 25% smaller would be a nice win for traders everywhere.

 

[Grav_Moped]

The functional gaming equivalency would be smaller drives, or a more efficient J drive (i.e. 8% volume per jump instead of 10%).

The fuel efficiency problem with M-Drives is mostly non-existent, they require so little (i.e. just raw fusion power) as is, there's little motivation for a more fuel efficient drive.

But smaller, 25% smaller would be a nice win for traders everywhere.

The trick is, they did that.
High Guard. Moved the "fast-burn" fusion reactor out of the Jump Drive into the (now capable of being overclocked) Power Plant, leaving the core of the Jump Drive as a smaller, separate unit. Thus, TL increases allow more efficient drives (Jump + Power). Doesn't quite work with what they did to maneuver drives, but that's a separate tradeoff made for game balancing reasons (high acceleration gained a design cost other than power plant fuel, which -- for small ships -- they'd gutted).

 

[spank]

The trick is, they did that.
High Guard. Moved the "fast-burn" fusion reactor out of the Jump Drive into the (now capable of being overclocked) Power Plant, leaving the core of the Jump Drive as a smaller, separate unit. Thus, TL increases allow more efficient drives (Jump + Power). Doesn't quite work with what they did to maneuver drives, but that's a separate tradeoff made for game balancing reasons (high acceleration gained a design cost other than power plant fuel, which -- for small ships -- they'd gutted).

They did alot more than that, Powerplants progress from 4% of ship's mass per point of power to 1% of ship's mass per point of power.
.
Quite a bit better than a 25% improvement.

 

[Grav_Moped]

They did alot more than that, Powerplants progress from 4% of ship's mass per point of power to 1% of ship's mass per point of power.
.
Quite a bit better than a 25% improvement.

Starting at the bottom end, it takes J2 for 100Td from a flat 10Td (JD-A only, per LBB2'77) to a range that runs from 11Td (TL-10) to 5Td (TL-15). Advancing TL enables a possible 45% reduction in (jump drive plus power plant) volume within HG rules alone.

Adding power plant fuel requirements to the comparisons just makes it sillier.

But it all makes a lot more sense when viewed as what 1st Ed. High Guard did to 1st Ed. Book 2, than it does when looking at it as what 2nd Ed. High Guard did. And 2nd Ed. Book 2 just kept pretty much everything for backwards-compatibility reasons, throwing the whole thing off.

 

[TamsinP]

And in MgT2e the relative size of M-drives and J-drives is reversed:

M-drive = 0.01M*Mn
J-drive - 5 dTons plus 0.025M*Jn

You can get reduced sizes at TLs above that of introduction, but it costs more to do so.