VEEGA 1.5 Edition

[Junipurr]

Low memory does severely exaggerate this effect also.

Hmmm, my next step is to try any increase internal memory without uninstalling.

 

[Blazer Ayanami]

Hmmm, my next step is to try any increase internal memory without uninstalling.

You can try to zip some files you don’t commonly use, or create backups on Google Drive/Mega or wherever you want, or simply moving them to another device, like a PC or something.

 

[Junipurr]

You can try to zip some files you don’t commonly use, or create backups on Google Drive/Mega or wherever you want, or simply moving them to another device, like a PC or something.

Files I can move manually, I routinely move to my SD Card. Like screendumps.

 

[TtTOtW]

You have an S5. I have a J2. Runs Eternia fine as long as I do not timewarp within 5km of anything. I have 2gig free space.

 

[Junipurr]

You have an S5. I have a J2. Runs Eternia fine as long as I do not timewarp within 5km of anything. I have 2gig free space.

Right so it is a memory thing then.

 

[Altaïr]

Wow, there has been a lot there.

Junipurr Determining a gravity assist trajectory is known as a NP problem, which means there's no easy way to solve it. It's generally done with a computer. However it's possible to calculate relatively easily (though it's approximative) the deviation obtained from a gravity assist. The trajectory around the body is an hyperbola, which equation is:

r = p/(1+e×cos(θ-φ))

where p is the orbital parameter, e the eccentricity, and φ the argument of periapsis.
e<1 means the trajectory is elliptic
e=1 means it's parabolic
e>1 means it's hyperbolic

For an hyperbola, the deviation angle is equal to:
2×acos(-1/e) - π

To use those formulas you have to calculate p and e from ingame data. I have some formulas for that, but I'm on holidays right now, I don't have my notebook with me. But you can probably find them easily with the following formulas:
periapsis = p/(1+e)
1/2 × v^2 - μ/r = -p/(2×(1-e^2))

You have to know the periapsis, and the speed at a given radius. I usually use the speed at the SOI level for this, but it works with any point. Then you have 2 equations, and 2 values to determine, p and e. The second one is very general while being quite simple by the way. It can be applied in a lot of situations, that's often a life saver. If you need φ you'll need a protractor. There are some protractor apps that can help you to get an angle from a screenshot.

That's relatively simple and predictable until now, but in practice this is still approximative. Firstly, because the deviation formula is exact when you consider it for an infinite radius. But the approximation is rather good in practice. But there's also another problem, during the gravity assist, the planet still rotates around its parent body, and the planetary configuration changes during the time you perform your swingby. This slightly changes the deviation angle. In practice, you have to evaluate the angle by which the planet has moved, and to substract it if you made a prograde slingshot, to add it if you made a retrograde slingshot. That's the reason why retrograde slingshots are slightly more efficient in practice.

But to evaluate that angle is more difficult, because it depends on the planet speed (which can easily be found because the orbits are circular), but also on the time you spend being in the SOI. And for this one you need the Kepler equation. I can't remember the exact formula, but you can find it on the internet (be careful, there's an equation for elliptical orbits, and another one for hyperbolic orbits).

With all of this you can calculate the result of a gravity assist quite precisely, but it's still an approximation, you would have to check the actual result ingame, and overall that's already a tedious process.

I'll try to help you, but as you see, it's rather a long process.

 

[James Brown]

Wow, there has been a lot there.

Junipurr Determining a gravity assist trajectory is known as a NP problem, which means there's no easy way to solve it. It's generally done with a computer. However it's possible to calculate relatively easily (though it's approximative) the deviation obtained from a gravity assist. The trajectory around the body is an hyperbola, which equation is:

r = p/(1+e×cos(θ-φ))

where p is the orbital parameter, e the eccentricity, and φ the argument of periapsis.
e<1 means the trajectory is elliptic
e=1 means it's parabolic
e>1 means it's hyperbolic

For an hyperbola, the deviation angle is equal to:
2×acos(-1/e) - π

To use those formulas you have to calculate p and e from ingame data. I have some formulas for that, but I'm on holidays right now, I don't have my notebook with me. But you can probably find them easily with the following formulas:
periapsis = p/(1+e)
1/2 × v^2 - μ/r = -p/(2×(1-e^2))

You have to know the periapsis, and the speed at a given radius. I usually use the speed at the SOI level for this, but it works with any point. Then you have 2 equations, and 2 values to determine, p and e. The second one is very general while being quite simple by the way. It can be applied in a lot of situations, that's often a life saver. If you need φ you'll need a protractor. There are some protractor apps that can help you to get an angle from a screenshot.

That's relatively simple and predictable until now, but in practice this is still approximative. Firstly, because the deviation formula is exact when you consider it for an infinite radius. But the approximation is rather good in practice. But there's also another problem, during the gravity assist, the planet still rotates around its parent body, and the planetary configuration changes during the time you perform your swingby. This slightly changes the deviation angle. In practice, you have to evaluate the angle by which the planet has moved, and to substract it if you made a prograde slingshot, to add it if you made a retrograde slingshot. That's the reason why retrograde slingshots are slightly more efficient in practice.

But to evaluate that angle is more difficult, because it depends on the planet speed (which can easily be found because the orbits are circular), but also on the time you spend being in the SOI. And for this one you need the Kepler equation. I can't remember the exact formula, but you can find it on the internet (be careful, there's an equation for elliptical orbits, and another one for hyperbolic orbits).

With all of this you can calculate the result of a gravity assist quite precisely, but it's still an approximation, you would have to check the actual result ingame, and overall that's already a tedious process.

I'll try to help you, but as you see, it's rather a long process.

Well, do you have a physics knowledge of University then?

 

[Junipurr]

Wow, there has been a lot there.

Junipurr Determining a gravity assist trajectory is known as a NP problem, which means there's no easy way to solve it. It's generally done with a computer. However it's possible to calculate relatively easily (though it's approximative) the deviation obtained from a gravity assist. The trajectory around the body is an hyperbola, which equation is:

r = p/(1+e×cos(θ-φ))

where p is the orbital parameter, e the eccentricity, and φ the argument of periapsis.
e<1 means the trajectory is elliptic
e=1 means it's parabolic
e>1 means it's hyperbolic

For an hyperbola, the deviation angle is equal to:
2×acos(-1/e) - π

To use those formulas you have to calculate p and e from ingame data. I have some formulas for that, but I'm on holidays right now, I don't have my notebook with me. But you can probably find them easily with the following formulas:
periapsis = p/(1+e)
1/2 × v^2 - μ/r = -p/(2×(1-e^2))

You have to know the periapsis, and the speed at a given radius. I usually use the speed at the SOI level for this, but it works with any point. Then you have 2 equations, and 2 values to determine, p and e. The second one is very general while being quite simple by the way. It can be applied in a lot of situations, that's often a life saver. If you need φ you'll need a protractor. There are some protractor apps that can help you to get an angle from a screenshot.

That's relatively simple and predictable until now, but in practice this is still approximative. Firstly, because the deviation formula is exact when you consider it for an infinite radius. But the approximation is rather good in practice. But there's also another problem, during the gravity assist, the planet still rotates around its parent body, and the planetary configuration changes during the time you perform your swingby. This slightly changes the deviation angle. In practice, you have to evaluate the angle by which the planet has moved, and to substract it if you made a prograde slingshot, to add it if you made a retrograde slingshot. That's the reason why retrograde slingshots are slightly more efficient in practice.

But to evaluate that angle is more difficult, because it depends on the planet speed (which can easily be found because the orbits are circular), but also on the time you spend being in the SOI. And for this one you need the Kepler equation. I can't remember the exact formula, but you can find it on the internet (be careful, there's an equation for elliptical orbits, and another one for hyperbolic orbits).

With all of this you can calculate the result of a gravity assist quite precisely, but it's still an approximation, you would have to check the actual result ingame, and overall that's already a tedious process.

I'll try to help you, but as you see, it's rather a long process.

Yes. Very complicated formula, needs protractor in real time, still inaccurate, and then you need to iterate to find best solution. (There is an infinite number of solutions with different burns.)

Actually if I was frank, using Hebrew Math, our concept of infinity is usually א. However the solutions to the four body problem is א to the power of three.

r = p/(1+e×cos(θ-φ)) is very non-linear, so a spreadsheet with tangential nummerical solver might need 100 iterations, per path considered. If I considered anything upto 3 orbits before encounter, that could be 1000 different paths.

That Math, Physics and Computing are a little off the scale for a computer game, but if you already have something running, yu can see better than me what kind of solutions this would spit out. So in a sense, I am still flying blind, because you are months ahead of me in Astronavigation.

I wanted to make a user friendly map, but that seems impossible now. Too many input variables.

 

[Altaïr]

Well, do you have a physics knowledge of University then?

Well yes I have, even if it's been long now. I haven't been to the university for 15 years
But even some high education only gives you some general knowledge. I've toyed a lot myself with those astrodynamics formulas, that's how I know about all those equations.

And we are still only talking about newtonian physics, what if we talked about relativistic formulas

Yes. Very complicated formula, needs protractor in real time, still inaccurate, and then you need to iterate to find best solution. (There is an infinite number of solutions with different burns.)

Actually if I was frank, using Hebrew Math, our concept of infinity is usually א. However the solutions to the four body problem is א to the power of three.

r = p/(1+e×cos(θ-φ)) is very non-linear, so a spreadsheet with tangential nummerical solver might need 100 iterations, per path considered. If I considered anything upto 3 orbits before encounter, that could be 1000 different paths.

That Math, Physics and Computing are a little off the scale for a computer game, but if you already have something running, yu can see better than me what kind of solutions this would spit out. So in a sense, I am still flying blind, because you are months ahead of me in Astronavigation.

I wanted to make a user friendly map, but that seems impossible now. Too many input variables.

Yep, it's not simple. Sorry if I discouraged you, that was not the intention...

To make the conic equation a bit more friendly, you can also write it that way:
1/r = 1/p × (1+e×cos(θ-φ))
Now it's a constant plus a sinusoid. It's a bit easier to toy with it.

In the end finding that kind of path requires practically a simulator... which is basically SFS.

For the story, most of the gravity assist trajectories I proposed are inspired from real trajectories: the VEEGA path was used by the Galileo probe. The descent to Mercury was used by the Messenger probe. Climbing back from Mercury through gravity assist is basically the same technique reversed... I copied that technique more than I invented it.

The craziest trajectory I designed was used to go from Mercury to Io. It used 10 gravity assists and needed only 750 m/s of delta-V. A small ship with a half full fuel tank was enough to make the trip. I made it especifically for the Grand Tour (landing on all planets/moons in a single launch), but it needed several weeks to work it out, and it's very situational in the end.

I tried to find other trajectories, but in the end the VEEGA trajectory is very flexible, it allows to reach Jupiter and above if needed. Using Mars for example is not viable: it's too light, and Jupiter is too far away to be reached that way. In the end I tend to reuse what is already known to work

 

[Junipurr]

Earth LEO
||
V
Venus VEEGA Trajectory
||
V
Clockwise
||
V
Earth x2
||
V
Jupiter, Saturn, or Interstellar

Earth LEO >> Direct Hoffman >> Moon, Mars, or Venus Surface.

Earth LEO
||
V
Venus VEEGA Trajectory
||
V
Anti-Clockwise
||
V
Mercury x5

 

[TtTOtW]

Some say, he sleeps in the Graveyard and works on Uranus, and that he's never heard his own voice since he permanently moves faster... than the speed of sound...
... all we know is...

 

[Mars Pathfinder]

Some say, he sleeps in the Graveyard and works on Uranus, and that he's never heard his own voice since he permanently moves faster... than the speed of sound...
... all we know is...

Is it light or Altaïr?

 

[Blazer Ayanami]

he sleeps in the Graveyard

He’s probably sick, or a serial killer.

he works on Uranus

Is it light or Altaïr?

Nah, it’s gotta be Altaïr. Light doesn’t works in Uranus.

 

[Mars Pathfinder]

Nah, it’s gotta be Altaïr. Light doesn’t works in Uranus.

Oh yeah Space Stig

 

[Junipurr]

Is it light or Altaïr?

Ayrton Senna

 

[Altaïr]

Ayrton Senna

I hope I won't end like him...

That reminds me when I was working on the Ariane 5... My job was so far from my home that it took more time for me to go to work than the Ariane 5 needed to send its payload on GTO
I was far below the speed of light then.

 

[Junipurr]

I hope I won't end like him...

That reminds me when I was working on the Ariane 5... My job was so far from my home that it took more time for me to go to work than the Ariane 5 needed to send its payload on GTO
I was far below the speed of light then.

I was and still am a big fan of Ayrton Senna. The Stig, Michael Schumacher, is not the God of the racetrack, but his understudy.

 

[Altaïr]

I was and still am a big fan of Ayrton Senna. The Stig, Michael Schumacher, is not the God of the racetrack, but his understudy.

Him too didn't end very well anyway
Well, at least he's not dead, but he's had some serious problem.

But it also happens that the Stig does wrong when performing a slightly too agressive gravity assit

Ouch, that hurts...

 

[Horus Lupercal]

I was and still am a big fan of Ayrton Senna.

A cultured soul I see

Him too didn't end very well anyway
Well, at least he's not dead, but he's had some serious problem.

But it also happens that the Stig does wrong when performing a slightly too agressive gravity assit
View attachment 52026 View attachment 52027
Ouch, that hurts...

Space Stig set to maximum attack

I'd call that a good landing. Looks like you phased through that hill as well.

Are you still using 1.4 dude?

 

[Altaïr]

A cultured soul I see



Space Stig set to maximum attack

I'd call that a good landing. Looks like you phased through that hill as well.

Are you still using 1.4 dude?

That's an old screenshot. It's just that I remind it because if how hilarious it is. I wanted to screenshot a very close fly-by, and instead, it showed my ship a fraction of second before a big boom.

 

[James Brown]

Him too didn't end very well anyway
Well, at least he's not dead, but he's had some serious problem.

But it also happens that the Stig does wrong when performing a slightly too agressive gravity assit
View attachment 52026 View attachment 52027
Ouch, that hurts...

Boom

 

[TtTOtW]

Well, SFS is having its ASS handed to it by Altaïr once again.

 

[AstronautAdam]

Ehm, guys what is VEEGA?

 

[James Brown]

Ehm, guys what is VEEGA?

Venus Earth Earth gravity assist

 

[Mars Pathfinder]

Ehm, guys what is VEEGA?

A good maneuver that can throw things beyond.

If acronym. Venus-Earth-Earth Gravity Assist