35
votes
When burns are made during inefficient parts of the orbit, where does the lost energy go?
After writing my comments, I started writing a new answer. That got long, so here's a shorter one.
The "energy of an orbit" may be poorly defined and depending on the definition, is not ...
- 11.2k
19
votes
When burns are made during inefficient parts of the orbit, where does the lost energy go?
The sum of all mechanical energy will be the same after your ideal burns. The difference will be that the portion given to your exhaust will be greater for higher burns.
For a burn farther away from ...
- 7,129
6
votes
Can Oberth bike? Is biking up and down a series of hills a good real-world analogy for understanding either the Oberth effect and/or gravity drag?
No, Oberth can't bike.
Why you want to "pedal like mad" in the brief downhill before an uphill, intuitively, is because your physiology is constrained by peak power, so you don't want to ...
- 12.3k
6
votes
Is there an upper velocity limit to obtain benefit of the Oberth effect for a high speed hyperbolic pass around a star?
In most star systems, if you can burn forever at 300 gees, orbital mechanics are things that happen to other people.
Coasting into the Solar System with a hyperbolic excess velocity of about $15\,000 \...
- 5,565
5
votes
Besides hyperbolic flybys, what are all the other cases where the Oberth effect can be used?
The Oberth effect doesn't give you more delta-V. It gives you a larger change in specific orbital energy for the delta-v you decide to expend because of where you decide to expend it. Spending delta-v ...
- 5,565
5
votes
Is it more efficient to burn all needed fuel in an Oberth manoeuvre at once or burn a fraction of the fuel for each orbit?
Retrograde thrust at periapsis doesn't lower the periapsis, it lowers the apoapsis. If you're trying to lower the periapsis, you need to apply thrust at apoapsis.
If you're trying to lower your ...
- 15.9k
3
votes
Accepted
Mangalyaan + Trident; is it possible? escape the solar system using a low cost booster
Is it possible to combine both approaches to perform flybys to the outer planets and escape the solar system?? Launch it first as if it was a Venus mission which heavily relies on oberth trickery, ...
- 19.7k
3
votes
Accepted
Why is a Hohmann transfer from an elliptical orbit to a circular one more efficient if done from Perigee?
Yes, the Oberth effect.
It can be easily understood in terms of kinetic energy:
$$E={m v^2\over 2}$$
Take the derivative:
$$dE=m v\,dv$$
Which for an impulsive burn means:
$$\Delta E=m v\Delta v$...
- 58.4k
2
votes
Oberth Effect in Solar Sails: Where does the extra energy comes from?
When two spacecrafts moving at different speeds are accelerated by solar sails, with everything else being equal, the $\Delta V$ is the same for them (or, rather, almost the same for non-relativistic ...
- 2,120
2
votes
Can Oberth bike? Is biking up and down a series of hills a good real-world analogy for understanding either the Oberth effect and/or gravity drag?
If
$F = ma\ \ $ and $\ \ E = \frac{1}{2}mv^2\ \ $ and $\ \ E = F·d$
and you apply the following constraints
friction losses in wheels and air drag are constant or negligible
force at the wheel hub is ...
- 361
2
votes
Can Oberth bike? Is biking up and down a series of hills a good real-world analogy for understanding either the Oberth effect and/or gravity drag?
While the actual efficiency of this strategy is questionable and involves biomechanics, friction, and many other complicating factors, the most reduced model can indeed be compared to the Oberth ...
2
votes
Can Oberth bike? Is biking up and down a series of hills a good real-world analogy for understanding either the Oberth effect and/or gravity drag?
The reason your biking scheme feels easier is, because the power you put into the pedals is applied for a longer time and therefore lower.
There is no relation to Oberth effect because the total ...
- 15.2k
2
votes
Is it more efficient to burn all needed fuel in an Oberth manoeuvre at once or burn a fraction of the fuel for each orbit?
As Mark already pointed out:
Retrograde thrust at periapsis doesn't lower the periapsis, it lowers the apoapsis. If you're trying to lower the periapsis, you need to apply thrust at apoapsis.
This ...
- 3,337
2
votes
Is it profitable to save fuel for the Oberth effect during a Jupiter gravity assist?
When it comes to the orbital mechanics of this scenario, one thing to note is that when it comes to oberth effect and raising the orbit around the Sun, it's the total velocity relative to the Sun that ...
- 4,231
2
votes
How close to Jupiter does a spacecraft need to get in order to gain maximum gravity assist and Oberth effect bonus for leaving the Solar System?
If you are looking for pure speed your spacecraft would need to get as close to Jupiter as possible without interacting with its atmosphere too much. Remember that there is atmosphere above the cloud ...
- 20.4k
1
vote
Is there an upper velocity limit to obtain benefit of the Oberth effect for a high speed hyperbolic pass around a star?
The Oberth effect is a property of the chemical rockets we use. When a spacecraft is on a highly elliptical orbit, the difference in speed between the highest point (apoapsis) and lowest point (...
- 371
1
vote
What is the relationship between the periapsis altitude and the change in velocity in a gravity assist?
The link in the question is 404 dead but I think this image from a different question could explain your observation:
(Source)
There is a maximum but this representation is not the scenario you ...
- 10.1k
1
vote
Does Lightsail-2 take significant advantage of the Oberth effect?
Their solar sailing algorithm is described in the Planetary Society blog:
Solar sailing: The spacecraft is attempting to raise its orbit using the solar sail. To do this, it must make two 90-...
- 130k
1
vote
Is it profitable to save fuel for the Oberth effect during a Jupiter gravity assist?
I can't give you a full tradeoff on whether it makes sense to save some delta-v for the gravity assist, but if you know how to accurately compute the gravity assist itself, then I think this will ...
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