How much dV do you lose with a higher LKO really?

[Red Iron Crown]

3 hours ago, dire said:

It is also this effect that acceleration decreases as speed increases, which is responsible for the speed of light being the universal speed limit. Even rockets aren't magic.

Speed of light being a universal limit is outside Newtonian mechanics, it's a relativistic effect. All my posts here in this thread are in that context, as KSP doesn't model relativity. There is no upper bound on speed under the Newtonian model.

[dire]

I wonder how close to c we can get a stock ship, relative to its SoI.

 

 

Edited August 30, 2016 by dire

[foamyesque]

13 hours ago, dire said:

It is also this effect that acceleration decreases as speed increases, which is responsible for the speed of light being the universal speed limit. Even rockets aren't magic.

 

Even in a relativistic context, Oberth applies, through a derivation involving relatavistic momentum and energy. The functional difference with rocketry, more precisely expressed, is that a rocket is a constant force acceleration mechanism, in that the force it provides is not affected by the velocity of the rocket. This is not the case with pretty much any other system I can think of.

[Plusck]

On 30/08/2016 at 8:43 AM, dire said:

It is also this effect that acceleration decreases as speed increases, which is responsible for the speed of light being the universal speed limit. Even rockets aren't magic.

Acceleration wouldn't change either if you were in a rocket approaching the speed of light. If you started off accelerating at 10 m/s² with infinite fuel, you'd still be accelerating at 10 m/s² as you approached the speed of light, as far as you were aware. But everyone else would see your "second" as passing verryy ssllloooowwwwwwlllllllyyyyyyy............

The hard limit for speed is less a question of speed, but rather the hard limit for any time passing (and therefore being able to do anything) at all.

Edited September 14, 2016 by Plusck
missing ^2

[qoonpooka]

At the risk of Necro'ing the thread: It's decisively argued herein that departing from a lower orbit is just better because the cost of attaining the higher orbit overwhelms the lower dV required to make the departure...

But what if you don't have to pay full price for the higher orbit?  What if, instead, you were to make a pass or two at Mun and/or Minmus on your way out of Kerbin - essentially obtaining a higher departure orbit at a discount?  Is a gravity assist sufficiently powerful that it can save you a few gallons of gas?

[Superfluous J]

3 hours ago, qoonpooka said:

At the risk of Necro'ing the thread: It's decisively argued herein that departing from a lower orbit is just better because the cost of attaining the higher orbit overwhelms the lower dV required to make the departure...

But what if you don't have to pay full price for the higher orbit?  What if, instead, you were to make a pass or two at Mun and/or Minmus on your way out of Kerbin - essentially obtaining a higher departure orbit at a discount?  Is a gravity assist sufficiently powerful that it can save you a few gallons of gas?

No, because there aren't any gate orbits higher than Mun. Duna and Eve are about Mun IIRC, and the rest are lower.

I don't know what you could or could not do with a Mun gravity assist, though. I've only played with it enough to decide it's not really something I want to play with