Circularise orbit

[Spyritdragon]

Before i say anything, i'll say i do know about burning prograde and retrograde at apoapsis/periapsis. I can make a reasonably circular orbit. For the time being im also working in vanilla.

What im wondering is, i've seen video's of people who have space stations in an almost exactly circular, 100 kilometer orbit, with less than .3 m/s in altitude change. Im wondering how this is done. As i come close to my circular orbit, my apoapsis and periapsis start to spin around my orbit, and any point in my orbit which i had already fixed at 100 kilometers deviates from it. Whenever i try to correct one part of my orbit back to 100 kilometers, another part of my orbit will deviate from it. I can manage to get my apoapsis and periapsis around the same altitude, but i never manage to put them at any even close to round number. How do i get these round-numbered orbits without having to put my kerbals in space for months/years?

My main problem here is the not being able to control the altitudes of my final orbit, rather than being unable to perfectly circulising it.

[Johnno]

For the time being im also working in vanilla.

Which I take it you mean no mods? There's your problem right there. I only use Engineer Redux that gives me flight info, in which case I can finetune my orbits with RCS, but it doesn't result in perfect orbits. Then again, a few meters off doesn't matter much. If you want perfectly round numbers I suspect MechJeb and its autopilot part are the way to go, that's probably how people do it. As you've already found out, manually doing it in 'vanilla' is hard. I've also heard of something called Manouver Edit or somesuch, where you can put in exact numbers for your nodes/burns, haven't looked into it though.

But in short, mods are the answer to your question.

[RawChicken]

Mechjeb or hyperedit do this.

When I circularize a orbit for a spation, I really dont care if it is <10 km off on a >100km orbit , I mean, It doesnt matter that much when you are docking.

[Winter Man]

To give a non-GET MODS! answer, I achieve it using RCS at the apoapsis and periapsis.

[Spyritdragon]

Okay, thanks for the information everyone :-). I've heard a whole lot about Mechjeb going around KSP, so i'll look into that.

[Sephta]

1: get your apoapsis and Periapsis as close to your orbit height as possible

2: at Apoapsis use RCS (with ASAS active and trimmed on prograde) to get your periapsis close to a couple of meters

3: do the same at your periapsis for your apoapsis.

4. repeat 2 & 3 until you get to the desired orbit

Hint: when firing RCS, you should stop when apoapsis and periapsis are at an equal distance to your ship (given you startet at one of the two points)

[Nibb31]

There really is no point is having a perfectly circular orbit unless you have OCD. It doesn't make rendez-vous or docking any easier and the slightest nudge during docking, or a simple rotation will change your orbit. In real-life, NASA considers that an orbit that has less than 100km difference between Ap and Pe is circular.

[SiliconPyro]

One trick that might make the process a little quicker for you is a mid-point adjustment. When you are equal distances from your AP and PE, a radial burn can adjust both at once. If you're heading toward your AP, point your craft toward the planet at -90 and burn or use RCS. Your AP will decrease and your PE will increase. I used to be pretty OCD about my orbits, but now if they're within .005km, I'm good.

[Spyritdragon]

@Norcalairman Wow, thanks, ill try that . For some reason i never tried burning anywhere but prograde and retrograde when adjusting my orbit.

[SiliconPyro]

@Norcalairman Wow, thanks, ill try that . For some reason i never tried burning anywhere but prograde and retrograde when adjusting my orbit.

I highly recommend putting an orbital maneuver trainer into orbit. Something with a bunch of fuel and RCS. Then pay close attention to where you are and where you're pointing and watch how your orbit changes. Try various types of burns at different points on your orbit, then try combining them. I promise you'll learn best that way and when you really need to know off the cuff how to get your orbit changed, you'll just point and burn instead of hopping over to the forums while your game is paused or using MechJeb. I'm not a MechJeb hater, I've used it a lot, but I play vanilla right now and I really feel more accomplished doing everything stock.

[Spyritdragon]

Okay, thanks :-).

Small side question: I had a rather nasty splashdown earlier and a bit of my ship blew up. I ended my flight, only now i have half a dozen RCS-thrusters bobbing around sillily in my ocean. Can't use 'end flight' because they're not part of my ship anymore - is there a way to delete these without endangering unmanned rovers, landed spacecraft, sattelites and space-stations?

I've looked around on the internet, but i couldn't find any sollution pertaining to stuff that's on the surface/in the sea. The 'maximum debris' makes me afraid it'll destroy stuff i don't want it to.

[Person012345]

Go to the tracking station. Left click the debris icon to show only debris (right click it to add it to the list of things shown) and click the abort button on the bits you want to end. Or fly them and "end flight".

Edit: Also, on the topic of circularisation, I can only suggest being more gentle, using lower power engines/RCS and making sure you align right. I don't tend to have much trouble making very circular orbits. Although there does appear to be a slight bug in the latest build where orbits aren't properly stable.

Edited June 13, 2013 by Person012345

[Spyritdragon]

I can give it a try when i can start up KSP again (can't get to my game right now), but that's kindof my point. I can't focus on the debris anymore, because for some reason it only allows me to focus on parts that have a command module attached. Or does the station itself have an end-flight button?

Anyway, ill try the abort thing. Thanks :-)

And thanks for the info on circularisation :-).