How to bring down debris in orbit?

[guitarxe]

So for my first few foreys into space I was still learning, and didn't really think about where my second-last stage ends up being after I decouple it.

Obviously, it ended up in orbit. Now I want to bring it down. Is there any feasible way of doing this? Would it be just as simple as bumping it along retrograde with some kind of space-tug kind of craft that has a bunch of girders on it for the bumping?

Also, what's a good way to ensure all my non-payload stages end up falling back to Kerbin? I like to design my rockets in such a way that the final payload stage ends up in orbit with a full fuel tank. So that of course means the second-final stage needs to do the orbital insertion, and once it's in orbit it's not coming back down. I COULD time it so that it pumps me up to just below orbit, and then do the final bit of dV burn for orbit with my final stage, but the timing on that is tricky and I like to keep things simple.

Would some Sepratrons pointing in the retrograde direction be able to slow it down enough to come back down?

Edited July 17, 2014 by guitarxe

[RenevB]

I don't think I personally can help you much with the second part of your questions.

The first part: well, that isn't more difficult than docking. If you have access to the claw, you can use that to deorbit debris. Just bumping it sufficently along the retrograde vector would work equally well, but is slightly more difficult, as you can easily send it spinning. You could also choose the easy mode, and delete the debris in the tracking station.

[EdFred]

Add Probe core + RCS fuel + RCS thrusters to the last dropped stage. Then switch over to the last stage and retro burn until your periapsis is low enough that the orbit decays - either enough that it goes below 22km and it will disappear on its own, or just get it down to 40-50km, and watch it until it crashes. (it may take an orbit or two to do so)

Edited July 17, 2014 by EdFred

[TrooperCooper]

Use something like this to manually pull the debries into a low orbit:

Or you could just delete them in the tracking station of the space center (make sure debries are marked visible in the top menu, then delete them on the left).

[severedsolo]

I like to put sepratrons facing backwards on my final launcher stage, when circularisation is complete I point prograde and stage, this activates the sepratrons (which are burning retrograde, because they are upside down) and the booster (usually) falls back to Kerbin

[metaphor]

Sepratrons also work pretty well to deorbit spent stages if you're in a low orbit. Just put the sepratrons in the same stage as the decoupler.

[zxczxczbfg]

Personally, I just try to design my craft so that I never have to eject stages while in orbit; I always eject while I'm either on the way up, or on the way back down, so that they fall back to the surface.

[Pecan]

Yes, anything attached or not that slows the debris' orbital velocity - rockets, bumping, dock/claw tug - will bring it back eventually.

The simplest way to deal with final stages is to simple add a probe core, so it can operate on its own, and leave enough fuel after orbital insertion so that it can turn around, burn retrograde and de-orbit itself. Anything that pushes the periapsis back below 69km will work but ideally you want enough to get below 22km so it's deleted automatically. 100m/s deltaV should be sufficient, and remember that's without the payload and with the launch-stage almost out of fuel so there isn't much mass left to push, so you won't need very much fuel to do it.

[1of6Billion]

Just fhugettaboutit. Chances of getting hit by anything in orbit are pretty slim

[guitarxe]

Why do people mention specifically 22km? What happens at 22km?

[severedsolo]

At 22km Kerbins atmosphere becomes thick enough that the game will automatically delete any craft (and debris) that pass that altitude. Otherwise it will just orbit indefinitely (unless it's your active vessel)

[guitarxe]

Orbit indefinitely? I thought being under 70k was enough to have atmosphere slow down the debris that it eventually falls?

[RenevB]

To elaborate: the game deletes anything moving through an atmosphere thicker than 0.01 atm (on Kerbin around 22, 23 km) and not in your physics bubble (~2.3, 2.5 km away from your controlled ship, I'm not 100% certain of the precise numbers). This (partially) because no physics means no drag, and at some point the game must assume that uncontrolled debris (sometimes sadly spacecraft) reenters and crashes anyway.

[Dave Kerbin]

Why do people mention specifically 22km? What happens at 22km?

Objects that are 'on rails' in KSP don't interact with anything because they are being simulated as just a solid mass orbiting whatever body they are near (so no rotation, no structural flexing, no atmospheric drag). However to avoid some issues there is an altitude above every body where an on rails object will be deemed to have 'crashed'. For Kerbin that altitude is 22km so any on rails object getting that close will 'crash' and be instantly deleted.

[guitarxe]

Oh, I see. Thanks everyone!

[asb3pe]

Why do people mention specifically 22km? What happens at 22km?

oops already answered, didn't see page 2 Oh well.

http://wiki.kerbalspaceprogram.com/wiki/Kerbin

Atmosphere

Kerbin's atmosphere contains oxygen and extends to roughly 69,078 meters. Its atmosphere exponentially rarefies with altitude with a scale height of 5 km.^[3] The atmospheric pressure on Kerbin at an altitude expressed in meters, generally is:

The thickness of Kerbin's atmosphere makes it suitable for aerobraking and using parachutes to save fuel during reentry and landing. Debris above approximately 23 km will not be removed.