What counts as a low orbit over Kerbol?

[ShadowDragon8685]

I've managed to get a probe into interplanetary space. That's not new for me, since I dipped Jebediah and Bill up in a rocket to take some measurements once before.

I want to send this probe on a sun-diving trajectory to get some Science! from Low Kerbol Orbit and then bring it back up to rendezvous with Kerbin.

But I can't for the life of me find out what altitude actually is a low Kerbol orbit! >_< I guess I can just quicksave and experiment, but it's quite frustrating. Does anybody know?

Edited February 8, 2014 by ShadowDragon8685

[Fett2oo5]

Check this out:

Low Kerbin Orbit

[MilkToast]

I don't think that was actually the question.

I've got a probe down around 100km above the surface of Kerbol - stupid me, however, didn't equip science parts so I can't answer that.

[Max Grant]

OK I was reading this so wrong. Low Kerbol orbit was anything under 100,000 km. I believe. I was getting science from the Sun by doing dives that took me down to like the 60's and I was getting down there and burning like a whole tank of fuel trying to get some Oberth effect off it.

Edited February 7, 2014 by Max Grant

[ShadowDragon8685]

Check this out:

Low Kerbin Orbit

OK I was reading this so wrong. Low Kerbol orbit was anything under 100,000 km. I believe. I was getting science from the Sun by doing dives that took me down to like the 60's and I was getting down there and burning like a whole tank of fuel trying to get some Oberth effect off it.

Kerbol. Kerbol! Not the planet, the star!

I'm trying to dip a sundiver probe down low into Kerbol's SOI so I can get some sweet science out of it.

It looks like it'll take a massive amount of dV, though. I'm not sure how in the world I'm going to do that, without some ridiculous craft with eight ion engines that takes forever and twenty days to burn anywhere...

[Fett2oo5]

well, my mistake then. Sorry.

[Jouni]

You don't need that much delta-v to get near Kerbol. 1,000,000 km is already a low orbit, so a 4200 m/s escape burn from LKO should get you near enough. If you can do a manned mission to Mun and back, you already have the hardware to launch a probe for a close Kerbol flyby.

[Geschosskopf]

OK I was reading this so wrong. Low Kerbol orbit was anything under 100,000 km. I believe. I was getting science from the Sun by doing dives that took me down to like the 60's and I was getting down there and burning like a whole tank of fuel trying to get some Oberth effect off it.

Actually, anything below 1,000,000 km is low orbit at Kerbol.

I did such a mission the other day, described in full in this thread. As you can see in the pics there, the actual mission vehicle (upper stage) had over 7800m/s. This was JUST BARELY enough to get home with. By the time I got my Kerbin Pe below 30km so I could aerobrake straight to the ground, I had less than 400m/s left.

You can go TO Kerbol any time you want, no launch window needed, just like coming home from Mun. It's the getting back that's takes the time. You'll be in an elliptical orbit with a Pe down near Kerbol and the Ap out at Kerbin's orbit, but you'll have to wait multiple orbits before Kerbin synchs back up with you. And you probably won't have enough delta-V to change this; you'll just have to wait. It pays nearly 1000 Science points, though.

[Jouni]

You can go TO Kerbol any time you want, no launch window needed, just like coming home from Mun. It's the getting back that's takes the time. You'll be in an elliptical orbit with a Pe down near Kerbol and the Ap out at Kerbin's orbit, but you'll have to wait multiple orbits before Kerbin synchs back up with you. And you probably won't have enough delta-V to change this; you'll just have to wait. It pays nearly 1000 Science points, though.

The orbital period is quite close to 40% of Kerbin's, so completing five orbits should give a reasonable return window. You probably need very little fuel for the return, if you fine tune the orbital period in advance, and are willing to do some spectacular aerobraking.

[Geschosskopf]

The orbital period is quite close to 40% of Kerbin's, so completing five orbits should give a reasonable return window. You probably need very little fuel for the return, if you fine tune the orbital period in advance, and are willing to do some spectacular aerobraking.

When I did it, it was in fact 5 orbits later that Kerbin came around. HOWEVER, I just had a the closest approach markers, not an actual encounter, even though the markers were right on top of each other, just a hair outside of being an encounter. And it required nearly 4000m/s at a Kerbol Pe just inside 900km to turn that into an encounter and get the Kerbin Pe down low enough to stop there. Seriously, I burned for like 10 minutes without seeing the trajectory change AT ALL, and when it did, it just sort of blinked at the far end from being a close approach to an encounter, without the blue line moving noticeably.

And yes, the aerobraking was harsh. 6200m/s when I hit the air, 28.8 Gs experienced.

Bottom line: if you don't have nearly 8000m/s when you leave, don't expect to come back.

[Jouni]

I'm kind of tempted to try it with 5000 m/s when I have time.

The key thing is to do the orbit corrections far enough in advance. 40% of Kerbin's orbital period is approximately 42 d 14 h 36 min 58 s, so you should aim for it as soon as you leave Kerbin's SoI, assuming that it still gets you below 1,000,000 km. That should make the eventual encounter happen just at the trailing edge of Kerbin's SoI. Make the orbit 30 minutes faster, and you should be pretty close to a collision course with Kerbin.

[Geschosskopf]

@ Jouni: I look forward to your results. Let me know how it comes out.

[Taki117]

The most efficient method of getting into low Kerbol orbit is. A bi-eliptic transfer. Basically you raise your AP as high as possible, then when you get there lower your Pe (it shouldn't take much) then at peace lower your Ap down until it touches Kerbin orbit (or you get an encounter)

[JenBurdoo]

The most efficient, maybe, but that would take years -- you have to go (way) farther away before you can get closer.

The answer to the OP is here: http://wiki.kerbalspaceprogram.com/wiki/Science

Look at the Celestial Body Multipliers chart, it indicates where "low above planet" starts. Anything above that but still in SOI is "high above." Low above Kerbol is 1 million km.

[ShadowDragon8685]

Hoooo boy...

I'm starting to wonder if I should do something stupid like, say, park a full Rockomax BIG with an LV-N under it at like, 80,000Km, just under Kerbin's SOI, then attach a probecraft to that.

My initial plan was to to get my Ap above Kerbin's orbit, drop my PE down below low Kerbol orbit, do a swingby, flip back up to apoapsis, circularize, and do a hohman transfer at the window; insert back into Kerbin's SOI, drop my PE to about 30Km and fall back to Kerbin's soil like a gasoline-soaked, trebuchet-launched cat.

Ih, and for the guy who chewed me out about being wrong calling it Kerbol?

Boom. Right there in white and black, on the official wiki.

The answer to the OP is here: http://wiki.kerbalspaceprogram.com/wiki/Science

Look at the Celestial Body Multipliers chart, it indicates where "low above planet" starts. Anything above that but still in SOI is "high above." Low above Kerbol is 1 million km.

Oh my goodness, I can't believe I couldn't find that! >_<

Thank you. THANK you!

Edited February 8, 2014 by ShadowDragon8685

[JenBurdoo]

Good to hear I could help!

Incidentally, read the Kerbol article before you say that. It states that the official name is "The Sun" and (near the bottom) that the name Kerbol was devised on the forum and doesn't (yet) appear in the game. They may still add it. In all honesty though, it's like the complaints about calling the characters "kerbalnauts," another "unofficial" term. I use both. Feel free to call it what you like - it's your game. Until there are multiple stars and types of astronaut in the game, there's no danger anyone will be confused.

[Jouni]

Ok, this started to bother me too much, so I had to try it. Most of the pictures are behind links, as downsizing them from 1920x1080 to 1024x576 makes the text hard to read.

Here is the Icarus on launchpad:

:

It got a bit excessive. First I thought it was unfair to send one kerbal alone on such a long mission, so I used the bigger command pod and sent three. Then I wanted a simple design that would work on the first try, so nuclear engines were out. Next I realized that I didn't want to wait for a puny Poodle to complete the 4200 m/s burn, so I added some boosters. Finally I had to import my heavy lifter from another save to get the thing into orbit. Here is the Icarus at LKO. Start mass is 57.3 tonnes and total delta-v is 5085 m/s.

I messed up a bit and burned more fuel than was necessary. After leaving Kerbin's SoI, I burned prograde until I got the orbital period to 42 d 14 h 06 m 50 s. RCS was needed for the final adjustments, as even a quick tap on 'H' added a few seconds to the orbit. Ultimately I was left with 647 m/s for the return home.

I wasn't really interested in doing anything close to the Sun, so I just warped the next 170 days, until I could see what kind of encounter I would have with Kerbin after the last orbit. Not too bad. Unfortunately I was going to have a Mun encounter on the way back, so fine tuning the approach before reaching Kerbin's SoI would probably not be very accurate. Still, I asked MechJeb for a maneuver node to get my closest approach to 20 km, and it proposed this 1.6 m/s burn a few days after the final periapsis.

After reaching Kerbin's SoI, I did some manual course adjustments to get the periapsis below 20 km. That didn't require much, so I was ultimately left with 640 m/s of delta-v. The Icarus entered Kerbin's atmosphere at almost 6500 m/s, started burning already at 50 km, and experienced 22.8g peak acceleration, but everyone got back home safely.

[Geschosskopf]

@ Jouni:

What a difference that little bit of orbit tweaking on the way out makes. I'll have to remember that for the future. Thanks can congrats!

[RandomGuy1824]

Thanks Necro bones for replying to a 3 year old thread

Edited February 24, 2017 by RandomGuy1824

[Val]

@Egdod. It seems a bit pointless to ask to get back on topic, 3 years after the last post.

@RandomGuy1824, please use the Report post button instead of Necromoaning.

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