Rune

Orbital maneuvers: navigational achievements.

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Rune    4362
Posted (edited)

Ever felt like Kepler and Newton where sitting on your shoulders, whispering as you plotted a maneuver? Maybe you managed to plot a course that seemed impossible, and got your kerbals back home with the last drop of fuel. Perhaps plotted three gravity assists with a single node? Circularized around Jool with RCS and Tylo to await rescue, because you had horribly misjudged your dV, but are a heck of a navigator? Well this is the place to show off those navigational skillz! It's amazing what this game teaches us to do, so let's show off our intuitive understanding of orbital mechanics, and those feats of orbital maneuvering that made us feel like we were the guys at JPL.

orbital_mechanics.png

I'll start with the one that prompted me to write this post, so you see what kind of thing I'm talking about. See, I was wrangling this asteroid, with not a lot of time (or engines), and I just managed to stop it at close approach, in a very weird 50º inclination (in my defense, I didn't see it until it came into kerbin's SOI, else I would have corrected the trajectory in solar orbit with plenty of time). Trouble is, the rock is about 1,700mT, and I only have four puny nukes on the ship tugging it. Even with a lot of fuel tank space for them, I can only get ~150m/s out of the tanks before I dry them and have to process more fuel, so I am limited in what I can do in a single burn. Changing that inclination and altitude by brute force, in any case, would take ages. So, what to do? Easy, just catch a ride on the Mun!

6462psc.png

I highlighted the important bits so you can admire the thing, plotted in all its glory. Just two maneuvers totaling 67m/s! And you can't see it from there, but take my word for it, the resulting orbit is not only a lot lower (16,400x78kms vs 39,300x9,800kms), it also has pretty much zero inclination (the game won't tell me, but I did the trick of moving the camera to make it coincide with the Mun's orbital plane). Yay me! I totally felt like like a pro when I plotted that. The key is that Munar encounter, where I fiddled with the node more or less by gut feeling until I got closer and closer to what I wanted (use a gravity assist to kill my vertical motion and thus make my inclination 0º). It came out to around 51kms altitude, so I could actually gone a bit lower if I needed more change in velocity. Turns out I also go out on a very useful orbit, where I can move into an aerobrake to go lower down, or use another Mun encounter afterwards to circularize at around the Mun's altitude, with further small corrections. Isn't it awesome what you learn to do in KSP? And it's all done by Mk1 eyeball, not even precise node! :)

For completeness' sake, here's the "vehicle" I plotted this for, just before the very long capture burn that got me the initial "wherever it falls" Mun encounter.

jEWSPgS.png

Tip: to make good maneuver screenshots, you can make highlights persistent in map mode by right-clicking on stuff (manuver nodes, Ap/Pe nodes and all that stuff), and move the PoV around without clicking with Tab.

 

Rune. Now show me how you did it!

Edited by Rune

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regex    8867

Orbital slingshots? Every. Damn. Day.

7qsbJLb.png

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Rune    4362
34 minutes ago, regex said:

Orbital slingshots? Every. Damn. Day.

 

Cool one! That's, what, RSS? Care to explain the particulars of the situation, so we can be properly awed? :)

 

Rune. And perhaps learn something while we are at it!

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38 minutes ago, regex said:

Orbital slingshots? Every. Damn. Day.

7qsbJLb.png

Wait, which moon of Jupiter are you getting that assist from? It's not one of the Galilean moons, and I didn't think even those were large enough for a meaningful assist, much less any of the smaller moons.

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regex    8867
Posted (edited)
32 minutes ago, Rune said:

Cool one! That's, what, RSS? Care to explain the particulars of the situation, so we can be properly awed? :)

It's nothing particularly special, just using Callisto's gravity to lower my apoapsis. It's just easier to do in stock because SOIs are so big. In RSS you need to ... wait longer. :P

And no, that doesn't make your Munar inclination change any less impressive.

27 minutes ago, IncongruousGoat said:

Wait, which moon of Jupiter are you getting that assist from? It's not one of the Galilean moons, and I didn't think even those were large enough for a meaningful assist, much less any of the smaller moons.

Callisto, and yes, they are massive enough to perform such maneuvers. What you didn't see was the 2.2km/s braking burn that got me into the Jovian system in the first place. Maneuvers like this just mean you can be much sloppier about your braking burns.

Edited by regex

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Shadowmage    3687

One of the best transfers and maneuvers I ever managed to wrangle, was this Jool insertion and multi-moon encounter setup.  Capturing at Jool and getting flybys of 4 out of 5 moons for <100dV, no dedicated insertion/braking burn (and the fifth moon likely doable for very little extra dV, once I get closer and can get more accurate trajectory predictions).  This was all plotted from Kerbin orbit, and the maneuver shown on the dV widget is the ejection burn.  Haven't gotten back to the game in a few weeks, but when I finally do, it is going to be one busy little probe returning scads of science from all the flybys and still having a few k of dV left in the tanks.

sdbLiuf.png

1KEaLm8.png

Apparently I misplaced the rest of the screenshots showing the rest of the flyby encounters.  Sad.  I'll have to load the game up and see if it is all still in place :)

 

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This is my favorite orbital achievement thus far, and one of my biggest "aha" moments in KSP. Everybody probably does this, but the first time was a complete surprise (it was a lucky accident), and now it's something that I take for granted.

You can see that I'm about 2 years away from a Jool encounter. This is right after I made a slight correction at the node to set up a Tylo encounter.

screenshot16.png

I have the standard number of conics set (3 I believe), so in this next pic, I added an empty maneuver node (because it will add the extra conic to show your orbital path). Now you can see, even though my Tylo encounter is 2 years away, I already have an orbit around Jool. 

 

screenshot17.png

If I want to, I can adjust the orbit anywhere along the way, depending on what I wanna do when I get there. But no matter what, I'll capture at Jool without needed a single drop of fuel. No dangerous aerobraking or lugging shields along. Just a nice, easy gravity brake that was set up 2 years earlier. And it works every single time. It's probably an ordinary accomplishment, but I'm extremely proud that I discovered it on my own.

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Rune    4362
Posted (edited)
21 hours ago, Shadowmage said:

One of the best transfers and maneuvers I ever managed to wrangle, was this Jool insertion and multi-moon encounter setup.  Capturing at Jool and getting flybys of 4 out of 5 moons for <100dV, no dedicated insertion/braking burn (and the fifth moon likely doable for very little extra dV, once I get closer and can get more accurate trajectory predictions).  This was all plotted from Kerbin orbit, and the maneuver shown on the dV widget is the ejection burn.  Haven't gotten back to the game in a few weeks, but when I finally do, it is going to be one busy little probe returning scads of science from all the flybys and still having a few k of dV left in the tanks.

Apparently I misplaced the rest of the screenshots showing the rest of the flyby encounters.  Sad.  I'll have to load the game up and see if it is all still in place :)

Pretty cool! The Jool system really is the paradise of a good navigator, and the reason many of us end up learning how to grav-assist. And four moons without mid-corrections sounds sick!:)

13 hours ago, Cpt Kerbalkrunch said:

This is my favorite orbital achievement thus far, and one of my biggest "aha" moments in KSP. Everybody probably does this, but the first time was a complete surprise (it was a lucky accident), and now it's something that I take for granted.

You can see that I'm about 2 years away from a Jool encounter. This is right after I made a slight correction at the node to set up a Tylo encounter.

I have the standard number of conics set (3 I believe), so in this next pic, I added an empty maneuver node (because it will add the extra conic to show your orbital path). Now you can see, even though my Tylo encounter is 2 years away, I already have an orbit around Jool. 

If I want to, I can adjust the orbit anywhere along the way, depending on what I wanna do when I get there. But no matter what, I'll capture at Jool without needed a single drop of fuel. No dangerous aerobraking or lugging shields along. Just a nice, easy gravity brake that was set up 2 years earlier. And it works every single time. It's probably an ordinary accomplishment, but I'm extremely proud that I discovered it on my own.

Well, braking into a Joolian orbit using Tylo may be much more common than it once was, but it's still a pretty big accomplishment! Think about it, in the real world, it took NASA until the seventies to use the trick, with Mariner 10, to get it to Mercury. And you learned how to do it with a videogame! So yeah, welcome to the club of people that think planning complicated maneuvers is fun. :)

 

Rune. Any other navigators out there? :wink:

Edited by Rune

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regex    8867
Posted (edited)
13 hours ago, Cpt Kerbalkrunch said:

This is my favorite orbital achievement thus far, and one of my biggest "aha" moments in KSP. Everybody probably does this, but the first time was a complete surprise (it was a lucky accident), and now it's something that I take for granted.

22 minutes ago, Rune said:

Well, braking into a Joolian orbit using Tylo may be much more common than it once was, but it's still a pretty big accomplishment!

Back in the days before proper atmospheric heating everyone just used Jool to brake; you could pretty much blindly throw anything into an atmosphere and expect it to survive. Tylo is much safer for interplanetary tugs that don't bother with aeroshields nowadays.

IMO it's a much better state of affairs because people have and get a greater understanding of orbital ballet. Getting a Tylo intercept from outside of Jool orbit, even with the exaggerated SOIs in stock, takes some fiddling and is to be commended.

Edited by regex

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Red Iron Crown    12089

This capture in the Jool system on my way to Laythe made me feel like a steely eyed rocket man:

hKwUrdH.png

Slingshot from Tylo to capture, correct inclination, and set the Laythe encounter. Felt particularly good because a) this was exactly what I was trying to do, whereas usually slingshots are accidental things for me, and b) it was a cheap 25m/s burn to change from a somewhat random Jool entry into this precise one, because I corrected just after leaving Kerbin's SoI

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@Rune, had to show you this one real quick. This was for the Retro Rescue Challenge I just completed. Had to rescue a Kerbal in retro-solar orbit between Kerbin and Eve. You can see here that Jool is flipping my ship directly into a retrograde orbit without needing a burn within it's SOI. I wasn't sure this was possible. The credit goes to @Physics Student for paving the way. I give myself some credit for figuring out how he did it and implementing it. I completed the challenge and I'm absurdly pleased with myself.

 

screenshot205.png

 

 

As a fan of navigation, I thought you might like it. In fact, if you're so inclined, you should check out the challenge. It was a lot of fun, and really tough.

 

You can read my victorious mission report as well :kiss:

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suicidejunkie    267

A fair bit more mundane than the above things, but I was pretty pleased to get two stranded Kerbals from a surface wreck up to Minmus orbit using EVA packs during the same pass of the orbital station.

The first one to launch, arced up higher than required and caught the station during descent. 

The second one flew a more direct route and boarded the station 2 minutes before the first one rendezvoused.

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Veeltch    1997
Posted (edited)

I once plotted a course to encounter Jool with a Tylo slingshot. The best thing about this is that, what I like to call "reverse slingshot" was prograde and would've put me in orbit (around Jool) without any additional manouvering.

I think I have a screenshot on my laptop somewhere.

EDIT: Oh, nvm. Apparently everyone else does it :D

Edited by Veeltch

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19 hours ago, suicidejunkie said:

A fair bit more mundane than the above things, but I was pretty pleased to get two stranded Kerbals from a surface wreck up to Minmus orbit using EVA packs during the same pass of the orbital station.

The first one to launch, arced up higher than required and caught the station during descent. 

The second one flew a more direct route and boarded the station 2 minutes before the first one rendezvoused.

Not sure it counts as an orbital maneuver, but launching 2 Kerbals off the surface Superman-style is definitely pretty cool.

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51 minutes ago, Veeltch said:

I once plotted a course to encounter Jool with a Tylo slingshot. The best thing about this is that, what I like to call "reverse slingshot" was prograde and would've put me in orbit (around Jool) without any additional manouvering.

I think I have a screenshot on my laptop somewhere.

EDIT: Oh, nvm. Apparently everyone else does it :D

Still a good achievement. It was this move that first opened my eyes to the possibilities. It made me realize how other guys were able to do such great things. With good launches and good orbital maneuvers, there's almost nothing you can't do.

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