Do KSP simulates Oberth Effect?

[Aghanim]

http://en.wikipedia.org/wiki/Oberth_effect

Oberth effect is when rocket at high speed generate more useful energy then at low speed. My question is, is this simulated in KSP? Because if its simulated than powered flyby is possible, which is to burn rocket at periapsis to get more boost

[Diche Bach]

It is my understanding that a burn in KSP, right at the periapsis of a flyby produces more acceleration than an identical burn that is not at a flyby periapsis. It seems that is one of the main applications of this effect, so in that sense yes; it seems it does simulate it.

Whether the Oberth Effect has any other real-life applications and whether the game simulates the effect in those other situations I do not know.

[maltesh]

Yes, KSP simulates the Oberth Effect.

If the Oberth Effect does not work in your orbital simulation, then you are either simulating momentum incorrectly, and the Tsilokovsky Rocket Equation doesn't work, or you are simulating Kinetic Energy and Gravitational Potential Energy incorrectly, and the Keplerian orbital equations don't work, or both.

[Diche Bach]

So here is a question for you physics folks. I was under the impression that one of the implications of the general theory of relativity was that, as a body approaches the speed of light the amount of energy needed to accelerate it closer to the speed of light begins to increases exponentially. At some point, accelerating one more meter per second is projected to require nearly infinite energy or something like that?

That seems to be directly opposite to this Oberth effect.

So does the Oberth Effect explain things at one end of the space-time continuum (the relatively slow end) and relativity explains things at the other end?

[Anton P. Nym]

So does the Oberth Effect explain things at one end of the space-time continuum (the relatively slow end) and relativity explains things at the other end?

The Oberth Effect relies on Newtonian mechanics, so yes it starts breaking down when relativistic effects become significant.

-- Steve

[Dangerous_Beans]

The Oberth Effect relies on Newtonian mechanics, so yes it starts breaking down when relativistic effects become significant.

-- Steve

Is it that it stops working as you get close to C?

From my reading of the wiki article, it seems that it should keep working the faster you go, so i thought it would be that the extra energy you get from the Orbeth effect becomes inconsequential compared to the extra energy required to accelerate the vessel.

[Sephta]

Problem is: with going close to light speed © your mass increases: the Oberth effect only is defined for a small object passing by a(n infinite) mass, that is not affected by gravitational effects of the small mass (i.e. your ship). If you're going to reach significant amounts of c so relativistic effects kick in: your mass increases - significantly! If you go fast enough, you will be able to pull a planet out of course, if you come close enough. So you're applying an Oberth effect on the planet - if it had thrusters So to say so...

[allmhuran]

The Orbeth effect requires no special coding to be simulated, it will result from pretty much anything that simulates objects in motion.

All it really says is this: You have some fixed amount of delta-V to "spend" (fuel in an engine). Spending that while travelling at higher speed results in a greater change in energy than spending it while travelling at a lower speed.

The math to show this is simply the kinetic energy equation: E = 1/2mv^2. Consider two cases where we apply the same delta V of 10. (constant mass in both examples, lets set it to 2 to make things easy). Units don't matter:

Example 1:

Initial Velocity = 0. Initial energy = 0

Final velocity = 10. Final energy = 1 * 10^2 = 100

Net energy change: 100

Example 2:

Initial velocity = 10. Initial energy = 100

Final velocity = 20. Final energy 1 * 20^2 = 400

Net energy change = 300.

In example 2 we got 200 more units of energy than we got in example 1, from the same change in velocity in both cases.

You can do a similar analysis based on the scientific definition of "work". Work is force over distance. The rocket is going to burn (apply a force) for the same amount of time no matter how fast you are going. But the faster you are going the more distance you will cover in that time. Therefore the rocket does more work at high speed than at low speed.

This does not conflict with the relativistic property of requiring more and more energy to increase your velocity as you approach the speed of light. What that would be telling us is that the amount of fuel you need to get your delta-V change in the first place (10 m/s in our examples above) needs to get bigger and bigger. But if you did have enough fuel to do it, the orbeth effect would still entail that those extra 10 m/s are "worth more energy" at high speed than at low speed.

[KerbMav]

So, what did we really gain for our voyage/orbit after using the oberth effect?

If adding 10 m/s just adds 10 m/s to our orbital velocity regardless of planetary mass, height of the orbit or initial velocity - then what is the extra gain in energy doing for us?

[magnemoe]

So, what did we really gain for our voyage/orbit after using the oberth effect?

If adding 10 m/s just adds 10 m/s to our orbital velocity regardless of planetary mass, height of the orbit or initial velocity - then what is the extra gain in energy doing for us?

One easy way to see the oberth effect is to make an Mun flyby, make an node changes your Pe (closest encounter), now make an new node at Pe. Change the Pe adjustment and see how the effect changes.

The effect depend on the gravity of the body so you get more out of Jool than Gilly.

I once put an ion probe in very low solar orbit, I know I saved 2Km/s over mechjeb estimate by only burning around Pe.

[Diche Bach]

Does this Oberth effect apply to animals, cars, bicycles?

[blizzy78]

Does this Oberth effect apply to animals, cars, bicycles?

Technically, the effect applies to everything. Though you might not notice it at the slow speeds a car is going, for example.

[Skorpychan]

So here is a question for you physics folks. I was under the impression that one of the implications of the general theory of relativity was that, as a body approaches the speed of light the amount of energy needed to accelerate it closer to the speed of light begins to increases exponentially. At some point, accelerating one more meter per second is projected to require nearly infinite energy or something like that?

That seems to be directly opposite to this Oberth effect.

So does the Oberth Effect explain things at one end of the space-time continuum (the relatively slow end) and relativity explains things at the other end?

Not quite. Relativity is 'right' at all points, but until you get up to significant fractions of the speed of light, it's practically identical to newtonian physics.

At least, as far as I understand it. I failed A-level physics because I couldn't get my head around things.

[Kimberly]

Not quite. Relativity is 'right' at all points, but until you get up to significant fractions of the speed of light, it's practically identical to newtonian physics.

At least, as far as I understand it. I failed A-level physics because I couldn't get my head around things.

That's basically it. We developed a simple model that covered our observations, but then we discovered things that didn't fit into our neat little model...so we made a complex model that accounted for these new observations, as well. Science marches on! But why apply the complex model to situations where the simple model works quite adequately? Even the Moon landings were done largely using patched conics instead of n-body physics.

[Amoun]

*right eye twitches*

This game is a whole different world to me now

[blizzy78]

This game is a whole different world to me now

How so?

/10chars

[Diche Bach]

*right eye twitches*

This game is a whole different world to me now

If you find the Oberth Effect unsettling then check this out

I particularly like the sound of "Quantum Chaos"; good name for a Super-Villain, eh?

This page seems to have changed (expanded) a great deal since the last time I looked at it; so I cannot actually find the tidbit that I remembered, and do not recall exactly which one of these unsolved problems it reflected on.

However, if memory serves, some of these unsolved problems have realworld significance and/or were recognized as an unsolved riddle because of incongruous realworld observations. The one I'm remembering is that, a couple times space craft that have been sent on flybys of Earth had slightly different final velocities after the maneuver than was expected. I want to say that this was being interpreted as bearing on dark matter, but not sure. Anyway, it ties back into the Oberth Effect.

ADDIT: and of course, how can we go any longer without mentioning that golden exemplar of science: the Journal of Irreproducible Results.

Not sure if the following is irony, paradox or just plain funny as heck

JIR received attention from American military intelligence when a copy of one of their articles was found among other papers in an abandoned terrorist headquarters in Kabul. The article was a highly unrealistic and farcical explanation of how to build a nuclear weapon that some unwitting Al Qaida member had filed away. Nonetheless the discovery prompted a short-lived official investigation.[2][3]

Edited August 12, 2013 by Diche Bach