Costs of variant grav vehicles?

[McPerth]

Well, in an atmosphere, at some point your thrust will be balanced by the drag from the air.

True, this is not your vaccum maximum speed, but your atmospheric maximum speed (even if on the rules is listed as Top Vaccum Speed, as top vaccum speed is, by definition, 0.9999999... C theoretically, quite less practically).

Remember none of our designs would work on vaccum (nor on exotic atmospheres, BTW), as all of them need an atmosphere with oxigen for the PPs to work (or carry their own oxigen supply, but that would weight quite more than the fuel carried).

 

[Zutroi]

I'm affraid you miscalculated the acceleration, as formula is (tons of thrust/loaded weight)-1.

I'm affraid you forgot to substract this '1' (in truth I guess it should be 'gravitiy of the world in Gs' instead of plain '1'), so accelerations sould be (respectively) 0.04 G and 0.11 G, and cruise/top speeds 40/50 for the Sherlock and 144/180 for the Carnegie.

Sorry if you sells plummeted after this corrections...

I've always had a problem with the 'official' calculation, as the whole thing is VECTOR math, not SCALAR...

The equation forms a right triangle, with 'thrust' being the hypotenuese and 'gravity' being one of the other sides... for simplicity we'll take a world with .3G local grav (so we can use the nice, simple 3-4-5 right triangle and not futz around with a lot of square roots...), and have our NPC Bil buy a locally made g-car with .5G thrust...

OTU math gives him 0.5-0.3 = 0.2G thrust.
Vector math gives him ((.5^2)-(.3^2))^0.5= 0.4G thrust in level flight, double the OTU result!

 

[McPerth]

I've always had a problem with the 'official' calculation, as the whole thing is VECTOR math, not SCALAR...

The equation forms a right triangle, with 'thrust' being the hypotenuese and 'gravity' being one of the other sides... for simplicity we'll take a world with .3G local grav (so we can use the nice, simple 3-4-5 right triangle and not futz around with a lot of square roots...), and have our NPC Bil buy a locally made g-car with .5G thrust...

OTU math gives him 0.5-0.3 = 0.2G thrust.
Vector math gives him ((.5^2)-(.3^2))^0.5= 0.4G thrust in level flight, double the OTU result!

You're right, but if you want to calculate as you say, aside form complicating the calculations a lot, you must take into account if your grav vehicle is lifting, diving or flying level, as vector would be different, so I guess the designers tried to keep it easy.

 

[Icosahedron]

Thanks. I do know about these calculations, and I ask myself "If you can output 0.04 G ad infanitum (or for the duration of the fuel anyway) why can you only reach 50 kph? Why can't I reach max unstreamlined velocity (300 kph), but just take a long time to get there?"

And I've never found a good answer to the first question. Do you have one?

Best regards,

Ewan

It could be about safety and reaction times - just think of all the problems you get with spacecraft having over-large vectors. You need to cruise at a speed you can reduce to zero in a reasonable amount of time. Civilian vehicles would probably have speed governors built in for this purpose.

 

[McPerth]

It could be about safety and reaction times - just think of all the problems you get with spacecraft having over-large vectors. You need to cruise at a speed you can reduce to zero in a reasonable amount of time. Civilian vehicles would probably have speed governors built in for this purpose.

I think if that was the limit (legal matters), it would be more related to the Law Level of the world you're in than to the gravity/thrust.

Aside from that, remember that limits are not only for acceleration, but for streamlining also. That seems to point (again) that the limit is marked by atmosphere drag braking, so being atmospheric top speed, not vaccum (as the book says). On the official errata as collected by Don Mckinney (DonM in this forum, you'll find a link to the errata with his signature on any of his posts) this is corrected (page 36 of the errata v2.19(15/9/10))

 

[E.D.Quibell]

Well, in an atmosphere, at some point your thrust will be balanced by the drag from the air.

Happy with that. That's the max unstreamlined velocity (300 kph). But why limit getting there with Grav drives?

Best regards,

Ewan

 

[E.D.Quibell]

I think if that was the limit (legal matters), it would be more related to the Law Level of the world you're in than to the gravity/thrust.

Aside from that, remember that limits are not only for acceleration, but for streamlining also. That seems to point (again) that the limit is marked by atmosphere drag braking, so being atmospheric top speed, not vaccum (as the book says). On the official errata as collected by Don Mckinney (DonM in this forum, you'll find a link to the errata with his signature on any of his posts) this is corrected (page 36 of the errata v2.19(15/9/10))

I agree with this. It has to be with atmosphere drag, and there are limits to USL, ST but not really for AF.

However this still doesn't answer my querstion. If I can continue to put out any proportion of Gs acceleration why can't I get to max unstrealmimed velocity (i.e. 300kph)?

Best regards,

Ewan

 

[McPerth]

I agree with this. It has to be with atmosphere drag, and there are limits to USL, ST but not really for AF.

However this still doesn't answer my querstion. If I can continue to put out any proportion of Gs acceleration why can't I get to max unstrealmimed velocity (i.e. 300kph)?

Best regards,

Ewan

When you move into any fluid (in this case athosphere), there's a resistence this fluid makes onto you (dragg) that acts as a brake (negative acceleration).

This dragg/braking depends mostly on the viscosity of the fluid (accepted in play as more or less constant in atmosphere), the streamlining of your vehicle (in game reduced to USL, SL and AF) and the speed.

The speed at which this braking equals your acceleration capability is your maximum speed.

As you see there are some simplifications to the formulas (not all atmospheres would have the same viscosity in real, as there would be various degrees of streamlining, not only 3 categories), as well as the fact that this maximum speed would in real be relative to air, not to ground (so depending also on the wind direction/speed), but I think it's OK to keep the game playable.

The maximum speed for streamlining class (regardless you acceleration) would be the maximum speed at which your craft is still controlable, due to streamlining of your vehicle/craft.