Odd volumetric/surface area ideas about drives.

[infojunky]

Consider this, thrust is limited by the amount of surface area devoted to thrusters.

Thus the amount of available thrust goes down as the total volume increases. this kinda matches the tables in Book2, note I said kinda.

This is a smaller ships go faster sorta idea.

This also works for Jump drives as well.

Thoughts?

 

[whartung]

"Not really"?

Thrust is mass out the back (and however may handwavitons get sput out by the M-drive).

It's mass, not surface area. Does more surface area mean more mass? Maybe? Sorta? If you have something with 1/2 the area and twice the energy per sq meter, then it equivalent.

Trivial, contrived example.

A 5.56mm rifle round (i.e. 22cal) has more "thrust" than a 22 Long Rifle round because of mass and velocity, but the surface area out the back is the same. Internally, the "drive" is "bigger", but the little hole out the back? Not so much.

Now, are their limits? Eh, probably, somewhere, I just don't know where or what they are.

 

[Marcatlas]

"Not really"?

Thrust is mass out the back (and however may handwavitons get sput out by the M-drive).

It's mass, not surface area. Does more surface area mean more mass? Maybe? Sorta? If you have something with 1/2 the area and twice the energy per sq meter, then it equivalent.

Depends on the edition. CT for most of its rules didn't reaction M-drives. Same with MT, Mongoose, etc.

 

[Rupert]

Consider this, thrust is limited by the amount of surface area devoted to thrusters.

Thus the amount of available thrust goes down as the total volume increases. this kinda matches the tables in Book2, note I said kinda.

This is a smaller ships go faster sorta idea.

This also works for Jump drives as well.

Thoughts?

There's no reason this can't work, and if you use modifiers to surface area for hull form, as FF&S did, you could get some interesting trade-offs, with high-area shapes allowing higher drive performance, but costing in armour mass.

 

[mike wightman]

If you are going to use the square cubed law for thrust why not for available hardpoints too?

 

[kilemall]

Only measurement that matters in LBB2 is dtons accelerated at xG.

Type A drive can push 200 dtons at 1G. We also get the result with 100 dtons 2G.

We could extrapolate that an A drive could push a 50 dton craft 4G, and 33 dtons 6G. To logical extremes, a 10 dton fighter with an A drive could accel 20G.

Perhaps we should give it a rating nomenclature- try 200 dtons standard thrust or some such.

Whats a bit fun is rating out some of those oddball dton/drives where it’s a bit more under the hood then standard tonnage would seem.

For instance the M drive is a 2000 dton rated that can take extra damage, but by multiplying it’s 400 dton/6G, 600 dton/4G and 800 dton/3G capability it pops out as more of a 2400 dton drive.

The X drive comes out as more 6000 dton, and Z drive as 12000 dtons.

I’m sure this has been discussed before with these values, just interesting to get a little more value out of your build within reason.

 

[Carlobrand]

You could change it up a bit. Maybe those are heat exchangers and acceleration is limited by how much waste heat the drive is able to discharge, lest it burn out.

 

[Nathan Brazil]

Im not getting it.
Please educate me further on how this works
I learned from Megatraveller and TNE that Gs or thrust determines base speeds, modified by atmospheric drag from configuration determines atmosphric speed. This is volume independent. The only time surface area factors into volume is waste space for real wings. But that remains an unchanging ratio. Do you mean surface area of the exhaust tube in the back of the drive?

 

[infojunky]

If you are going to use the square cubed law for thrust why not for available hardpoints too?

Heh, where do you think this whole chain of thought started.

Im not getting it.
Please educate me further on how this works
I learned from Megatraveller and TNE that Gs or thrust determines base speeds, modified by atmospheric drag from configuration determines atmosphric speed. This is volume independent. The only time surface area factors into volume is waste space for real wings. But that remains an unchanging ratio. Do you mean surface area of the exhaust tube in the back of the drive?

Ok, I started with surface area. Or generally the function f(x)= x^(2/3) which gives the ratio of volume to surface area. From that I supposed that there was a maximum amount of thrust one could derive from a unit of surface area (note the volume of said drive is a secondary consideration here).

Thus the amount of surface area controls the maximum amount of thrust that can be generated (or Jump potential for that matter)

The function stipulates that the amount of surface available for use for thrust gets smaller as the total volume increases.

 

[infojunky]

There's no reason this can't work, and if you use modifiers to surface area for hull form, as FF&S did, you could get some interesting trade-offs, with high-area shapes allowing higher drive performance, but costing in armour mass.

Actually these limits are kinda baked into FF&S.

 

[Rupert]

Actually these limits are kinda baked into FF&S.

But at quite high displacement. You'd need to have drive take up more area or have more restrictive placement if you wanted the limit to be more like CT's LBB2.

 

[infojunky]

But at quite high displacement. You'd need to have drive take up more area or have more restrictive placement if you wanted the limit to be more like CT's LBB2.

So true, and yes some adjustment would be required.

Mostly this thread is what happens when I am sitting out in the Courtyard with a big cup of tea and a cigarette (don't judge my bad habits ) pondering the Maths that govern Traveller.