Exaust Velocity by ship line

[Nyankosensei]

After the rebalance all exaust velocity are modified for mach the ship type, to me that is wrong becouse make some strange values, is enought to see the differences of deltaV from Wave to kanara and they have the same fuel onboard.

By what is wrote in the ship.lua file

-- Exhaust velocity Vc [m/s] is equivalent of engine efficiency and depend on used technology. Higher Vc means lower fuel consumption.

I think is better give some values by manifacture and age of the ship and after play with onboard fuel for get the need deltaV



Other point is possible have less fuel onboard for increase hyperdrive range and make more efficient uploaded fuel on cargo

[lwho]

I'm having a hard time to understand you mean.

Exhaust velocity is determined for example by the shape of the jet nozzle (i.e. the engine). So, I would expect it to be quite different between different kinds of ships. As far as I understand, your suggestion is to make it less different between ship types, which means they have the same efficiency. It doesn't make sense to have so many ship types, if they aren't distinctly different.

Also, I don't understand, why you have two curves "Proposed" and "Proposed Long Range". Exhaust velocity is a constant for the ship (well in reality it will probably vary with thrust and probably have a higher exhaust velocity with 100% thrust, than with 10%, but it's a game and let's not make it more difficult than necessary).

To get a higher deltaV, you have two possibilities:

1. Build a more efficient engine, i.e. one with higher exhaust velocity. This will give you more deltaV per ton of fuel (linearly as you see from the formula below).
2. Put more fuel on the ship (you can also change how fast the fuel is burned, but this changes only how fast you reach the maximum velocity). However, putting more fuel on a ship only has logarithmic effect.

For reference the formula for deltaV is (Tsiolkovsky rocket equation):

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deltaV = exhaustVelocity * ln((emptyMass + fuelMass) / emptyMass)

The formula for the thrust is:

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thrust = exhaustVelocity * burnRate
burnRate = fuelMass / time

So, while a higher burn rate increases your thrust, it will also deplete your fuel earlier, which is why it has no effect on the maximum velocity.

[Nyankosensei]

What i tell is that, if the exaust velocity is the Engine technology why in the same year and same manufacture we have so hight differences ?

Exaust velocity is not DeltaV or max speed but is the Engine efficency to burn fuel, why in the same year we have engines hable to give the same power with 1/4 of fuel ?

Those values are only for example but are for give identity to manufacture of the ship and is possible make more gap from 1 manufacture to another.

[lwho]

why in the same year we have engines hable to give the same power with 1/4 of fuel?

Because more efficient technology is much more expensive? So, not everyone can afford high-end hardware. IMHO that's the right way to balance it: All other things being equal, a more efficient ship (higher exhaust velocity) should be more expensive.

I still don't understand, why you are giving two different exhaust velocities for each ship type. What does "long range" mean in the graphs?

[Nyankosensei]

Long range mean less fuel onboard and less fuel burned in a travel, that can be usefull for improve hyperjump for big ships and make more usefull upload fuel on cargo.

Other point is that we can have low cost manufacturer like opli barnard or high cost and hight end performance with ship manufacturer like Mandarava or auronox and make more easy add new ship with some reference values

[Nyankosensei]

a more efficient ship (higher exhaust velocity) should be more expensive.

If we watch that graph the most efficent manufacture is the OPLI Barnard ?

But if you're the one who wrote the code and you can not understand what I'm saying is probably becouse I am in error

Sorry for waste your and my time

[mld]

Is delta-v the maximum attainable speed before you run out of fuel in space?
But if you are on a planet, you first need to beat gravity, so you will never achieve delta-v, right?

[lwho]

a more efficient ship (higher exhaust velocity) should be more expensive.

If we watch that graph the most efficent manufacture is the OPLI Barnard ?

I didn't check the prices of the ships. If that's your point that the prices do not match efficiency, maybe you should say so (and make a graph showing exhaust velocity vs. price).

But if you're the one who wrote the code

I did not write the code. And what I explained, actually had not much to do with the code, but with Newtonian physics. Admitted, it's only a game and not a simulation, but a game based on Newtonian physics and in my opinion we should stick to that to a certain degree. There are enough games out there that completely ignore physics.

and you can not understand what I'm saying is probably becouse I am in error

Or maybe because English is neither your nor my native language?

Long range mean less fuel onboard and less fuel burned in a travel, that can be usefull for improve hyperjump for big ships and make more usefull upload fuel on cargo

Okay, so you are only seeing it from the point of view "what to achieve for gameplay", but not from a physical point-of-view. Is that right?

Sorry for waste your and my time

I'm sorry, you're seeing it that way. Because balancing is certainly an aspect of the game that needs attention. So, I'm not saying everything is good, as it is now. It just seems we are not agreeing on how to improve it.

Is delta-v the maximum attainable speed before you run out of fuel in space?

Right, deltaV is the speed you would achieve without any external forces if you started at rest.

But if you are on a planet, you first need to beat gravity, so you will never achieve delta-v, right?

But you can convert the energy needed to escape from a body to equivalent delta-v. For Earth, to start at the surface and fly to a point far from Earth, that would be 11.2km/s (called escape velocity). If you started with that velocity (in any direction that doesn't collide with Earth, and ignoring atmospheric drag), you would stop moving "at infinity".

[DraQ]

Actually, I wouldn't go with simplistic "better ship == greater exhaust velocity".

Picture a spaceship. Thrusting is generally meant to change your momentum by launching some reaction mass.
This reaction mass will have resulting momentum vector (relative to origin) opposite to yours.

Now, since momentum is product of mass and velocity, you can generally achieve the same increase in thrust by launching proportionally more mass as by launching it at higher velocity.
Now, mass in space is difficult to come by - you're limited to what is sloshing around in your tanks, so you'd better launch it as fast as you can.
However, kinetic energy increases with square of velocity - energy requirements increase along with it (and since the temperature is function of particle velocity, your waste heat problem gets even worse than that).

So, the thing is that for same increase in power you can increase thrust much more by increasing the propellant flow, than by increasing exhaust velocity - for example if you get 4x the power, you will be able to increase thrust 4x by spending 4x as much propellant, but only 2x by actually increasing exhaust velocity.
Seems like a bad decision - after all it doesn't help your delta-v - ...unless you have to take off from massive planet and need at least as much thrust as you weigh, have to dodge incoming fire or are chasing nearby craft (nearby = you can catch up with it way before you reach your delta-v reserve for coming back).

So, all in all I propose that ships should have their overall thrust and exhaust velocity adjusted to their purpose - a ship meant to do heavy lifting (planetary miner or freighter, for example) will want thrust, even at the expense of delta-v, so will short-range courier/passenger transport (where you won't get to coast even with sub-par delta-v), short range interceptor or general combat ship.
OTOH ship meant for long range pursuits or courier/taxi missions will generally work better with less thrust but better delta-v, especially if it doesn't have to land on massive planets.

Alternatively (or complementarily) thrust throttling could be made a toggle, and allowed to throttle exhaust velocity vs propellant flow (such drives are researched even today, so why not?) with autopilot calculating optimal ratio.