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Great video! It was really helpful!
I hope that I can lend some constructive criticism in return for the information you've shared
Pretty much everything is good in the first (voiced over) part of the video. However, there are a few things that you can do to significantly increase your production quality for little effort. Try to occasionally pitch in and explain what you are doing. For less important parts, you can speed up the footage and add some music. This (maybe 15 minute) change can really increase your audience retention and eliminate any chance of confusion.
Of course, the video is already great as is, and I really enjoyed watching it. These could just be some things to think about in the future
I hope that I can lend some constructive criticism in return for the information you've shared
Pretty much everything is good in the first (voiced over) part of the video. However, there are a few things that you can do to significantly increase your production quality for little effort. Try to occasionally pitch in and explain what you are doing. For less important parts, you can speed up the footage and add some music. This (maybe 15 minute) change can really increase your audience retention and eliminate any chance of confusion.
Of course, the video is already great as is, and I really enjoyed watching it. These could just be some things to think about in the future
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Hooray VEEGA for 1.5! Thanks a lot TOtWOT!
T
The reason I do not include music is because Islam forbids it, so I accordingly dislike it and do not utilize it or listen to it. I had a tough time getting the audio done, so this is as good as I could get ut without taking another month to finish it. I really did want to go a bit deeper, and in a few places I froze the video to give me a chance to say what I needed to say. Also, in the beginning I'm only using 2× rather than 4× for the same reason. It also helped keep the initial manoeuvres visually clearer. Thanks Earl, I'd really do it better if I could.
I'm about as charming as a piece of wood.
I'm about as charming as a piece of wood.
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So I have been doing some research in the Interplanetary Transition Network, and seeing if I can apply it to SFS. Not only can I replicate some real life manouvres in SFS, like Lunar Assist, I have found that it isn't always the best idea. I do believe however, that the way SFS uses SOI, means that just inside the SOI is the equivalent of a Lagrange point.
Basically L2 is furtherest away from the heavier body, and most of the rest of the edge of the SOI is like L1. There is this problem, that even using the Lagrange points, most of the experimental trajectories use up more fuel than a straight Hoffman trajectory. I am still grappling with the physics behind this, but have mostly decided it is similar to a diffraction pattern. Only the white lines of the diffraction pattern are in n-space, and are very thin.
So these artist's impressions of the Interplanetary Transfer Network are just completely wrong. Also there is a huge difference in fuel usage, from one path to the next. The worst part, very few of these low burn paths can be done in one orbit, like in the VEEGA tutorial above. I attempted to do Lunar assist into a VEEGA, to see if I can improve on the ΔV useage. After two flybys of the moon, I had already expended more fuel than flying straight from LEO to a Venus Flyby. If I spent more time, doing a third pass, it may take an entire two years to get enough gravity assist to reach a Venus Flyby using less fuel.
I am going to keep experimenting in SFS, to try and make a useable map of the solar systems ITN, similar to the ΔV maps that are all over the internet. The problem with an ITN map, is it is in n-space, ie, more than four dimensions. I don't have access to JPL's software than can generate these trajectories. The NASA public tool only provides Hoffman trajectories.
Anyone have any links that might help me put L1 and L2 to better use in SFS? I am aware μ for most solar bodies gives significant solar assist. It is just the way SFS works with its SOI, it is difficult to translate the astrophysics.
Basically L2 is furtherest away from the heavier body, and most of the rest of the edge of the SOI is like L1. There is this problem, that even using the Lagrange points, most of the experimental trajectories use up more fuel than a straight Hoffman trajectory. I am still grappling with the physics behind this, but have mostly decided it is similar to a diffraction pattern. Only the white lines of the diffraction pattern are in n-space, and are very thin.
So these artist's impressions of the Interplanetary Transfer Network are just completely wrong. Also there is a huge difference in fuel usage, from one path to the next. The worst part, very few of these low burn paths can be done in one orbit, like in the VEEGA tutorial above. I attempted to do Lunar assist into a VEEGA, to see if I can improve on the ΔV useage. After two flybys of the moon, I had already expended more fuel than flying straight from LEO to a Venus Flyby. If I spent more time, doing a third pass, it may take an entire two years to get enough gravity assist to reach a Venus Flyby using less fuel.
I am going to keep experimenting in SFS, to try and make a useable map of the solar systems ITN, similar to the ΔV maps that are all over the internet. The problem with an ITN map, is it is in n-space, ie, more than four dimensions. I don't have access to JPL's software than can generate these trajectories. The NASA public tool only provides Hoffman trajectories.
Anyone have any links that might help me put L1 and L2 to better use in SFS? I am aware μ for most solar bodies gives significant solar assist. It is just the way SFS works with its SOI, it is difficult to translate the astrophysics.
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Altaïr, you've got a customer!
Yeah, it's generally accepted that lunar assists are worse than just going direct. The moon is too weak in 1.5 for that kinda thing.
Also, the SOIs in game don't work in the same way as they do in the real world, even taking into account the 2D aspect. Gravity is an either/or, not an everything, so Langrange isn't a thing because you can't be in that sweet spot where everything cancels each other out and leaves you hanging in the middle. You're always subjected to one gravitational pull and none of the others affect you.
Altair is our resident astro-navigation specialist. He created the ΔV maps for SFS you see dotted about the web and has...intimidate...knowledge with how SFS works.
Yeah, it's generally accepted that lunar assists are worse than just going direct. The moon is too weak in 1.5 for that kinda thing.
Also, the SOIs in game don't work in the same way as they do in the real world, even taking into account the 2D aspect. Gravity is an either/or, not an everything, so Langrange isn't a thing because you can't be in that sweet spot where everything cancels each other out and leaves you hanging in the middle. You're always subjected to one gravitational pull and none of the others affect you.
Altair is our resident astro-navigation specialist. He created the ΔV maps for SFS you see dotted about the web and has...intimidate...knowledge with how SFS works.
The Earth Moon gravity assist is quite powerful, it is just very difficult to match up with a Venus Transfer line, especially since the thrid pass is basically leaving Earth's SOI, and coming back again on an unknown trajectory. I could probably get it to work eventually, but for not much improvement, and very difficult to map.
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Ah, thanks Horus. He seems to be a customer that knows what he is talking about indeed
Hi Junipurr,
I've heard a little about the ITN, and to be honest, the theory behind that seems beyond my knowledge, but it's quite unlikely that you can recreate it in SFS anyway: Actually, SFS uses what is called the patched conics approximation: an object is considered to be only submitted to the gravity of the dominant body (which is materialized by the SOI). This is good to calculate easily and with good approximation an interplanetary probe trajectory (implying Hohmann transfers, gravity assists...), but this approximation fails to recreate the dynamics around the lagrangian points. You're right saying that L1 and L2 are at the edge of the SOIs, but still, they won't behave like L points. A n-body approach is necessary for this (at least 3 bodies...). Anyway, those points are unstable, and a ship placed there usually needs to perform some station-keeping to maintain its position. Moreover in practice that could be extremely frustrating to handle: you're aware about how a little correction can lead to a very different trajectory... At some points we are not computers.
About using the Moon for gravity assist, Horus is right, this is not viable. And trust me, I really like this technique, if it worked in that case I would be the first to promote it. One thing to consider is that using that technique to go to Venus would save at most 76 m/s, which is really little. This is the difference between a transfer to the Moon and a transfer to Venus. The reason why this value is low is because when you burn from LEO, you benefit from the Oberth effect (a burn is more efficient when it's performed close to a massive body). When you use some gravity assists from the Moon, you loose that Oberth effect, and the kick you get from the Moon isn't enough to compensate. I've tried myself, but two gravity assists don't give you enough speed, and boosting the second gravity assist is already too expensive. A third gravity assist could help, but the second one pulls you largely out of the Earth SOI, so I don't see how you could get that opportunity...
Sometimes going the simple way is still the most efficient, the gravitational slingshot is best used with massive bodies.
Hi Junipurr,
I've heard a little about the ITN, and to be honest, the theory behind that seems beyond my knowledge, but it's quite unlikely that you can recreate it in SFS anyway: Actually, SFS uses what is called the patched conics approximation: an object is considered to be only submitted to the gravity of the dominant body (which is materialized by the SOI). This is good to calculate easily and with good approximation an interplanetary probe trajectory (implying Hohmann transfers, gravity assists...), but this approximation fails to recreate the dynamics around the lagrangian points. You're right saying that L1 and L2 are at the edge of the SOIs, but still, they won't behave like L points. A n-body approach is necessary for this (at least 3 bodies...). Anyway, those points are unstable, and a ship placed there usually needs to perform some station-keeping to maintain its position. Moreover in practice that could be extremely frustrating to handle: you're aware about how a little correction can lead to a very different trajectory... At some points we are not computers.
About using the Moon for gravity assist, Horus is right, this is not viable. And trust me, I really like this technique, if it worked in that case I would be the first to promote it. One thing to consider is that using that technique to go to Venus would save at most 76 m/s, which is really little. This is the difference between a transfer to the Moon and a transfer to Venus. The reason why this value is low is because when you burn from LEO, you benefit from the Oberth effect (a burn is more efficient when it's performed close to a massive body). When you use some gravity assists from the Moon, you loose that Oberth effect, and the kick you get from the Moon isn't enough to compensate. I've tried myself, but two gravity assists don't give you enough speed, and boosting the second gravity assist is already too expensive. A third gravity assist could help, but the second one pulls you largely out of the Earth SOI, so I don't see how you could get that opportunity...
Sometimes going the simple way is still the most efficient, the gravitational slingshot is best used with massive bodies.
4KidsOneCamera
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Ah, thanks Horus. He seems to be a customer that knows what he is talking about indeed
Hi Junipurr,
I've heard a little about the ITN, and to be honest, the theory behind that seems beyond my knowledge, but it's quite unlikely that you can recreate it in SFS anyway: Actually, SFS uses what is called the patched conics approximation: an object is considered to be only submitted to the gravity of the dominant body (which is materialized by the SOI). This is good to calculate easily and with good approximation an interplanetary probe trajectory (implying Hohmann transfers, gravity assists...), but this approximation fails to recreate the dynamics around the lagrangian points. You're right saying that L1 and L2 are at the edge of the SOIs, but still, they won't behave like L points. A n-body approach is necessary for this (at least 3 bodies...). Anyway, those points are unstable, and a ship placed there usually needs to perform some station-keeping to maintain its position. Moreover in practice that could be extremely frustrating to handle: you're aware about how a little correction can lead to a very different trajectory... At some points we are not computers.
About using the Moon for gravity assist, Horus is right, this is not viable. And trust me, I really like this technique, if it worked in that case I would be the first to promote it. One thing to consider is that using that technique to go to Venus would save at most 76 m/s, which is really little. This is the difference between a transfer to the Moon and a transfer to Venus. The reason why this value is low is because when you burn from LEO, you benefit from the Oberth effect (a burn is more efficient when it's performed close to a massive body). When you use some gravity assists from the Moon, you loose that Oberth effect, and the kick you get from the Moon isn't enough to compensate. I've tried myself, but two gravity assists don't give you enough speed, and boosting the second gravity assist is already too expensive. A third gravity assist could help, but the second one pulls you largely out of the Earth SOI, so I don't see how you could get that opportunity...
Sometimes going the simple way is still the most efficient, the gravitational slingshot is best used with massive bodies.
Hi Junipurr,
I've heard a little about the ITN, and to be honest, the theory behind that seems beyond my knowledge, but it's quite unlikely that you can recreate it in SFS anyway: Actually, SFS uses what is called the patched conics approximation: an object is considered to be only submitted to the gravity of the dominant body (which is materialized by the SOI). This is good to calculate easily and with good approximation an interplanetary probe trajectory (implying Hohmann transfers, gravity assists...), but this approximation fails to recreate the dynamics around the lagrangian points. You're right saying that L1 and L2 are at the edge of the SOIs, but still, they won't behave like L points. A n-body approach is necessary for this (at least 3 bodies...). Anyway, those points are unstable, and a ship placed there usually needs to perform some station-keeping to maintain its position. Moreover in practice that could be extremely frustrating to handle: you're aware about how a little correction can lead to a very different trajectory... At some points we are not computers.
About using the Moon for gravity assist, Horus is right, this is not viable. And trust me, I really like this technique, if it worked in that case I would be the first to promote it. One thing to consider is that using that technique to go to Venus would save at most 76 m/s, which is really little. This is the difference between a transfer to the Moon and a transfer to Venus. The reason why this value is low is because when you burn from LEO, you benefit from the Oberth effect (a burn is more efficient when it's performed close to a massive body). When you use some gravity assists from the Moon, you loose that Oberth effect, and the kick you get from the Moon isn't enough to compensate. I've tried myself, but two gravity assists don't give you enough speed, and boosting the second gravity assist is already too expensive. A third gravity assist could help, but the second one pulls you largely out of the Earth SOI, so I don't see how you could get that opportunity...
Sometimes going the simple way is still the most efficient, the gravitational slingshot is best used with massive bodies.
Ah, thanks Horus. He seems to be a customer that knows what he is talking about indeed
Hi Junipurr,
I've heard a little about the ITN, and to be honest, the theory behind that seems beyond my knowledge, but it's quite unlikely that you can recreate it in SFS anyway: Actually, SFS uses what is called the patched conics approximation: an object is considered to be only submitted to the gravity of the dominant body (which is materialized by the SOI). This is good to calculate easily and with good approximation an interplanetary probe trajectory (implying Hohmann transfers, gravity assists...), but this approximation fails to recreate the dynamics around the lagrangian points. You're right saying that L1 and L2 are at the edge of the SOIs, but still, they won't behave like L points. A n-body approach is necessary for this (at least 3 bodies...). Anyway, those points are unstable, and a ship placed there usually needs to perform some station-keeping to maintain its position. Moreover in practice that could be extremely frustrating to handle: you're aware about how a little correction can lead to a very different trajectory... At some points we are not computers.
About using the Moon for gravity assist, Horus is right, this is not viable. And trust me, I really like this technique, if it worked in that case I would be the first to promote it. One thing to consider is that using that technique to go to Venus would save at most 76 m/s, which is really little. This is the difference between a transfer to the Moon and a transfer to Venus. The reason why this value is low is because when you burn from LEO, you benefit from the Oberth effect (a burn is more efficient when it's performed close to a massive body). When you use some gravity assists from the Moon, you loose that Oberth effect, and the kick you get from the Moon isn't enough to compensate. I've tried myself, but two gravity assists don't give you enough speed, and boosting the second gravity assist is already too expensive. A third gravity assist could help, but the second one pulls you largely out of the Earth SOI, so I don't see how you could get that opportunity...
Sometimes going the simple way is still the most efficient, the gravitational slingshot is best used with massive bodies.
Hi Junipurr,
I've heard a little about the ITN, and to be honest, the theory behind that seems beyond my knowledge, but it's quite unlikely that you can recreate it in SFS anyway: Actually, SFS uses what is called the patched conics approximation: an object is considered to be only submitted to the gravity of the dominant body (which is materialized by the SOI). This is good to calculate easily and with good approximation an interplanetary probe trajectory (implying Hohmann transfers, gravity assists...), but this approximation fails to recreate the dynamics around the lagrangian points. You're right saying that L1 and L2 are at the edge of the SOIs, but still, they won't behave like L points. A n-body approach is necessary for this (at least 3 bodies...). Anyway, those points are unstable, and a ship placed there usually needs to perform some station-keeping to maintain its position. Moreover in practice that could be extremely frustrating to handle: you're aware about how a little correction can lead to a very different trajectory... At some points we are not computers.
About using the Moon for gravity assist, Horus is right, this is not viable. And trust me, I really like this technique, if it worked in that case I would be the first to promote it. One thing to consider is that using that technique to go to Venus would save at most 76 m/s, which is really little. This is the difference between a transfer to the Moon and a transfer to Venus. The reason why this value is low is because when you burn from LEO, you benefit from the Oberth effect (a burn is more efficient when it's performed close to a massive body). When you use some gravity assists from the Moon, you loose that Oberth effect, and the kick you get from the Moon isn't enough to compensate. I've tried myself, but two gravity assists don't give you enough speed, and boosting the second gravity assist is already too expensive. A third gravity assist could help, but the second one pulls you largely out of the Earth SOI, so I don't see how you could get that opportunity...
Sometimes going the simple way is still the most efficient, the gravitational slingshot is best used with massive bodies.
I would like to, but it seems very difficult, to deconstruct the VEEGA manouvre in game, and apply it to other legs of my journey. At the start, there is an imperative to get an Earth - Venus - Encounter point alignment. My question is, is that alignment mathematically determined, or has it been discovered by trial and error?
It seems delaying transfer past this initial point suggested by the in game nav computer, angles you trajectory when arriving at Venus. I understand that is a pre-requisite for gravitational assist to work effectively. My next question, is that angle important, so a Venus to Earth trajectory can be found easier? There seems to be a lot of scanning the vector after entering SOI, but are we already close to that magic line, because of the previous alignment timing?
IRL, and to a smaller extent in game, finding the perfect trajectory in only one or two orbits seems obvious, but mathematically these trajectories usually only happen by mistake. A great deal of computational trial and error is involved. With the game being 2D and having no eccentricity currently, we can predict with high certainty where planets will be after a certain time delay. Recording that time delay, or calculating the apparant angle for a map, seems difficult without points of reference. Such points of reference are not common in this game. I can predict Lunar gravity assist by the angle the moon is making with the Sun Earth Orbit line. Then I have to subtract more time, or more angle, based on the rockets current position, and specific acceleration.
Doing this for Venus or any other planet in game is currently a bit beyond me. So I am experimenting, and building up a picture in my mind. There are other limits imposed by the games nav system, which means even if you know where that magic line is approximately, it is very hard to find in practice.
I think my next lot of experiments will be a reverse VEEGA to get to Mercury cheaply. The graveyard is not impossible for me to reach, even using Hoffman trajectories. The Δ V is huge, but so are my payloads. If I can get a couple more low burn trajectories mapped out in my mind, I might be able to come up with a general approach for any planet exisitng or added later.
My current planet mod I am working on, has 12 new stars and 12 new planets which don't make my phone crash. Most have a huge ΔV, making them more difficult to leave than Venus, because they are Super Earths Light Years away. I would like to have a generic low burn trajectory, so I can reasonably visit them using the current tech in game.
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It was mostly determined with practice. The ideal transfer to Venus can be determined mathematically, as this simply corresponds to the transfer window, but that's all. And still, this is only true because the planets' orbits are perfectly circular. If they are not, it's necessary to use some numerical analysis methods to determine a transfer window.
The angle is important, but in practice you have an acceptable margin of error. Between 2 attempts your trajectory may be slightly different, but in the end you will simply adjust your trajectory when you enter Venus' SOI so that you can encounter Earth. Once you get approximately the correct timing it's generally ok. But sadly, doing the adjustment is harder in 1.5. Under 1.4 we had the closest approach line that told us how close we were, now we are blind, so it requires more practice/trial and error
Or you can save, time-warp to see where you ship falls, then reload and make the correction accordingly.
I'm not sure I see exactly how you want to proceed, but if you plan to make a backward gravity assist with Earth, yes you will probably be able to reach Mercury that way, but because your apoapsis will be very high (at least at Earth level), the insertion burn around Mercury will be incredibly expensive. Don't forget that it's the most expensive part in the end. I had a technique for this under 1.4, that consisted in performing a backward swingby with Venus, to pull your ship on a Venus-to-Mercury transfer trajectory. Then by chaining several gravity assists with Mercury I could reduce the insertion cost. But in 1.5, Venus is closer to the Earth than before, and thus further from Mercury. Reaching Mercury that way is still possible, but you need to burn well past after the ideal transfer point (the same as with VEEGA) to make it possible. Then chaining gravity assists with Mercury is very tedious now. At least, the Venus swingby is already what saves the most delta-V.
The angle is important, but in practice you have an acceptable margin of error. Between 2 attempts your trajectory may be slightly different, but in the end you will simply adjust your trajectory when you enter Venus' SOI so that you can encounter Earth. Once you get approximately the correct timing it's generally ok. But sadly, doing the adjustment is harder in 1.5. Under 1.4 we had the closest approach line that told us how close we were, now we are blind, so it requires more practice/trial and error
Or you can save, time-warp to see where you ship falls, then reload and make the correction accordingly.
I'm not sure I see exactly how you want to proceed, but if you plan to make a backward gravity assist with Earth, yes you will probably be able to reach Mercury that way, but because your apoapsis will be very high (at least at Earth level), the insertion burn around Mercury will be incredibly expensive. Don't forget that it's the most expensive part in the end. I had a technique for this under 1.4, that consisted in performing a backward swingby with Venus, to pull your ship on a Venus-to-Mercury transfer trajectory. Then by chaining several gravity assists with Mercury I could reduce the insertion cost. But in 1.5, Venus is closer to the Earth than before, and thus further from Mercury. Reaching Mercury that way is still possible, but you need to burn well past after the ideal transfer point (the same as with VEEGA) to make it possible. Then chaining gravity assists with Mercury is very tedious now. At least, the Venus swingby is already what saves the most delta-V.
T
Altaïr and Junipurr. I discovered the initial alignment throug trial and error, combined with a comparison of practical results in VEEGA in 1.4, and engineered the flight path to cater for reasonable error and available information on screen during the various phases of the process. I can thus for certain say that, following the exact same initial alignment, and assisting anticlockwise with Venus at 40.1km perigee, will get you an easy and useful intercept with Mercury's orbit. What remains to be determined is Mercury's ideal angular offset to get an immediate Mercury assist upon first intercept of its orbit.
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The most painful is getting the first, but hopefully, there is a way to chain gravity assists with the same body after that. It relies on resonant orbits. Two orbits are resonant when their orbital periods form a rational ratio. It means that body 1 orbits m times while body 2 orbits n times in the same time. So if you exit Mercury's SOI making sure you're on a resonant orbit, you're guaranteed to meet it again after a few turns. That's how I calculated how to get a second encounter with Earth in the VEEGA procedure.
The same can be done with Mercury of course. Under 1.4, I used to aim for the 3:4 ratio, then 6:7, then I could make a cheaper insertion.
The method to get the resonance ratio is surprisingly simple, it relies on the 3rd Kepler law. If you have 2 bodies 1 and 2, let's call A1 and A2 their semi great-axis. If you have:
N2/N1 = (A1/A2)^(3/2)
Then the orbits are resonant, and the body 1 will orbit N1 times while body 2 orbits N2 times.
All you need is the semi great-axis of Mercury: its orbital radius. Then you have to find a semi great-axis you can aim for that gives an integer ratio with the formula above, and you're done.
However, because there is a trajectory correction soon after a GA, this breaks the resonance. For this reason, the orbit that must be made resonant is your orbit AFTER the correction burn. Just anticipate what will be your new periapsis (usually just below Mercury level), and calculate your apoapsis taking it into account.
Don't hesitate to ask if it's a bit confusing, I'll clarify
The same can be done with Mercury of course. Under 1.4, I used to aim for the 3:4 ratio, then 6:7, then I could make a cheaper insertion.
The method to get the resonance ratio is surprisingly simple, it relies on the 3rd Kepler law. If you have 2 bodies 1 and 2, let's call A1 and A2 their semi great-axis. If you have:
N2/N1 = (A1/A2)^(3/2)
Then the orbits are resonant, and the body 1 will orbit N1 times while body 2 orbits N2 times.
All you need is the semi great-axis of Mercury: its orbital radius. Then you have to find a semi great-axis you can aim for that gives an integer ratio with the formula above, and you're done.
However, because there is a trajectory correction soon after a GA, this breaks the resonance. For this reason, the orbit that must be made resonant is your orbit AFTER the correction burn. Just anticipate what will be your new periapsis (usually just below Mercury level), and calculate your apoapsis taking it into account.
Don't hesitate to ask if it's a bit confusing, I'll clarify
The most painful is getting the first, but hopefully, there is a way to chain gravity assists with the same body after that. It relies on resonant orbits. Two orbits are resonant when their orbital periods form a rational ratio. It means that body 1 orbits m times while body 2 orbits n times in the same time. So if you exit Mercury's SOI making sure you're on a resonant orbit, you're guaranteed to meet it again after a few turns. That's how I calculated how to get a second encounter with Earth in the VEEGA procedure.
The same can be done with Mercury of course. Under 1.4, I used to aim for the 3:4 ratio, then 6:7, then I could make a cheaper insertion.
The method to get the resonance ratio is surprisingly simple, it relies on the 3rd Kepler law. If you have 2 bodies 1 and 2, let's call A1 and A2 their semi great-axis. If you have:
N2/N1 = (A1/A2)^(3/2)
Then the orbits are resonant, and the body 1 will orbit N1 times while body 2 orbits N2 times.
All you need is the semi great-axis of Mercury: its orbital radius. Then you have to find a semi great-axis you can aim for that gives an integer ratio with the formula above, and you're done.
However, because there is a trajectory correction soon after a GA, this breaks the resonance. For this reason, the orbit that must be made resonant is your orbit AFTER the correction burn. Just anticipate what will be your new periapsis (usually just below Mercury level), and calculate your apoapsis taking it into account.
Don't hesitate to ask if it's a bit confusing, I'll clarify
The same can be done with Mercury of course. Under 1.4, I used to aim for the 3:4 ratio, then 6:7, then I could make a cheaper insertion.
The method to get the resonance ratio is surprisingly simple, it relies on the 3rd Kepler law. If you have 2 bodies 1 and 2, let's call A1 and A2 their semi great-axis. If you have:
N2/N1 = (A1/A2)^(3/2)
Then the orbits are resonant, and the body 1 will orbit N1 times while body 2 orbits N2 times.
All you need is the semi great-axis of Mercury: its orbital radius. Then you have to find a semi great-axis you can aim for that gives an integer ratio with the formula above, and you're done.
However, because there is a trajectory correction soon after a GA, this breaks the resonance. For this reason, the orbit that must be made resonant is your orbit AFTER the correction burn. Just anticipate what will be your new periapsis (usually just below Mercury level), and calculate your apoapsis taking it into account.
Don't hesitate to ask if it's a bit confusing, I'll clarify
I have discovered there is such a thing on the Lunar gravity assist, I think I will redo that test to get some calibration data first, sonce experimenting in the Earth-Sun-Moon four body system is fairly easy and familiar to me.
Well, there’s a lot of technical words on that post that I don’t understand...
But I do know one thing: is not recommended to use gravity assistances with the Moon to reach other planets in SFS. Why? Because the way our universe is scaled down. Basically, the benefit of a Lunar gravity assist are... minimal and you can lose them simply by using that small advantage on deltaV to align the second gravity assist. I’m sure Altaïr can explain better.
Is still a cool thing to try, tho.
But I do know one thing: is not recommended to use gravity assistances with the Moon to reach other planets in SFS. Why? Because the way our universe is scaled down. Basically, the benefit of a Lunar gravity assist are... minimal and you can lose them simply by using that small advantage on deltaV to align the second gravity assist. I’m sure Altaïr can explain better.
Is still a cool thing to try, tho.
I understand the drawbacks of Lunar assist better thanks to Altair. I can't remember a lot of these terms from my university days, but I am re-learning them. Just shows how my disability has put so many holes in my memory.
Even though Lunar gravity assist isn't useful most of the time, it will still be useful for establishing an experimental procedure I can use to start creating my own low burn map tool. It should show the ΔV boost for each different low burn line, and show the ΔV boost is usually less than going direct to Venus first.
I suspect if I can plot the unstable third pass lines, that some of them will be slightly more efficient, but making them useable isn't the goal. Understanding how to convert real world formulas into game logic is the key for me. Once I can visualise the 5th 6th and 7th dimension of these lines, I can then translate that information into a chart that is easier for others to understand. I can also make charts for each planet in game, and in my own custom galaxy, which will help me with my main project, explore the galaxy on my old android phone.
Even though Lunar gravity assist isn't useful most of the time, it will still be useful for establishing an experimental procedure I can use to start creating my own low burn map tool. It should show the ΔV boost for each different low burn line, and show the ΔV boost is usually less than going direct to Venus first.
I suspect if I can plot the unstable third pass lines, that some of them will be slightly more efficient, but making them useable isn't the goal. Understanding how to convert real world formulas into game logic is the key for me. Once I can visualise the 5th 6th and 7th dimension of these lines, I can then translate that information into a chart that is easier for others to understand. I can also make charts for each planet in game, and in my own custom galaxy, which will help me with my main project, explore the galaxy on my old android phone.
Yep, that’s what Altaïr does. He’s been the teacher of... well... almost every single player on the forum.
Oh, I understand. You are basically using the moon to learn how to make the smallest possible burn. Interesting. Well, you really seem to be planning very high efficiency missions, that’s nice.
Yes, that’s exactly the case many many times. You will find that using the Oberth effect of Earth is usually much more efficient than nailing precise lunar gravity assistances. Specially if you are going for Venus who is very close to Earth and the burn required to take your perihelion to its orbit is very small, only a few dozens of m/s.
Ooooh, this is very very interesting. We got a couple of charts, a couple of rocket calculators here on the forum. But for what I understand, yours will be something completely new and unique, and because of that I’m sure it will be a very valuable contribution to the forum and the SFS community in general.
Also, are you using planet editing to create the rest of the galaxy?
Oh, I understand. You are basically using the moon to learn how to make the smallest possible burn. Interesting. Well, you really seem to be planning very high efficiency missions, that’s nice.
Yes, that’s exactly the case many many times. You will find that using the Oberth effect of Earth is usually much more efficient than nailing precise lunar gravity assistances. Specially if you are going for Venus who is very close to Earth and the burn required to take your perihelion to its orbit is very small, only a few dozens of m/s.
Ooooh, this is very very interesting. We got a couple of charts, a couple of rocket calculators here on the forum. But for what I understand, yours will be something completely new and unique, and because of that I’m sure it will be a very valuable contribution to the forum and the SFS community in general.
Also, are you using planet editing to create the rest of the galaxy?