Deorbiting Space Junk

[Alaskan Glitch]

What is the best method for getting spent fuel tanks, rockets, and other debris out of orbit? I may not be able to do anything about the small stuff, but I should be able to get other junk out of orbit by design. Meaning, I should be able to use an unmanned command module on one or more stages that allows me to fly it back into the atmosphere, or deorbit after I'm done using it, especially if it still has fuel.

I've added boosters that slow the spent stage down after I separate, but that only works if I'm under 100 km on Kerbil. An orbit higher than 100 km and it slows the spent stage, but not enough to completely deorbit (at least not for a few decades).

I'm not really interested in recovering the resource. I'm more interested in keeping the low-Kerbil orbit as free from junk and debris as possible. The debris current orbiting Kerbil out masses the satellites I have in orbit by a factor of ten. That can't continue.

[fauxpas]

Can't you use a cheap probe with a claw to grab them and then burn up in orbit / land safety?

[Alaskan Glitch]

Originally posted by fauxpas:

Can't you use a cheap probe with a claw to grab them and then burn up in orbit / land safety?

I could develop a craft specifically for the removal of space junk, but it seems to me that having a design built-in would be more efficient. The boosters and first stage are no problem, because they always expend their fuel before reaching space. It is the second stage (particularly in orbits above 100 km) where I'm having an issue.

I've tried adding an unmanned command module to the second stage, but it doesn't seem to work. Adding boosters that fire upon separation do work, but are limited to about 100 km.

If I can't design them to "fall from the sky" on their own, then I see no other alternative than to develop a craft specifically for collecting and deorbiting space junk. What a waste.

[A Terrible Modder]

the tracking station can send warheads to destroy space junk

[Alaskan Glitch]

Originally posted by BOOMH34D$HOT:

the tracking station can send warheads to destroy space junk

You suck at being a troll.

[Slacker CA]

He's referring to the Terminate button in the Tracking Station.

https://wiki.kerbalspaceprogram.com/wiki/Tracking_Station

https://wiki.kerbalspaceprogram.com/wiki/File:TrackingStationButtons.png

[A Terrible Modder]

Originally posted by Slacker CA:

He's referring to the Terminate button in the Tracking Station.

https://wiki.kerbalspaceprogram.com/wiki/Tracking_Station

https://wiki.kerbalspaceprogram.com/wiki/File:TrackingStationButtons.png

yea

[andylaugel]

Build a ship with an efficient engine (high Isp in vacuum) and an Advanced Grabbing Unit (a.k.a. the Klaw). Rendevous and dock with the debris using it. At your Ap, accelerate retrograde until your Pe drops to 45 km. Release space debris, and accelerate your vessel until your Ap is 70 km or better. Then go watch your space debris burn up. Seriously, watch it. Atmospheric physics don't happen if no one looks. Repeat while you've got enough fuel for your vessel. Consider docking with a tanker with fuel for extended use.

[andylaugel]

Okay, if you want to design a ship that doesn't leave behind space debris with its second stage, then there is a simple way of doing it. Watch your trajectory from the map screen, and drop your second stage before your Pe gets too high. The atmosphere is 70 km high, but I tend to aim for 45 km for aerobraking. If you've done a gradual gravity turn, it shouldn't take too much more dV for your final stage to circularize your orbit.

[andylaugel]

Please excuse the 3 posts in a row, but I do find this topic interesting. Here is an example, using my usual low Kerbin orbit recovery rocket. Details vary slightly (antenna(s), probe cores, swivel/reliant/skiff, optional separatons on the boosters), but it's proven useful enough for 100+ launches in my careers.
https://steamcommunity.com/sharedfiles/filedetails/?id=732892664
I launched one of these in my most recent career to remove 2 pieces of space debris left over from before I got the Klaw for crew rescues. I don't claim to be the most efficient pilot, but here is how it went. I burned from launchpad, nosing down gently to the east until my Ap was 120 km at 2 minutes 20 seconds away. I then planned the circularization burn, which the navball told me would take 37 seconds. I waited, and then used up my last droppable stage with 350 m/s left on that burn, discarding it while the Pe was still below ground level. No space debris generated during the launch. I then completed the burn, getting a 72 km Pe.

From that 120 km Ap/72 km Pe orbit, it was a simple matter to rendevous with each bit of space debris, dropping the first one to aerobrake, restoring a stable orbit, then docking and landing the last bit of space debris. For LKO rendevous like this, it helps to know right-clicking a maneuver node toggles its mode, and the '+' button in the new configuration advances the maneuver an orbit.

[Alaskan Glitch]

Originally posted by andylaugel:

Okay, if you want to design a ship that doesn't leave behind space debris with its second stage, then there is a simple way of doing it. Watch your trajectory from the map screen, and drop your second stage before your Pe gets too high. The atmosphere is 70 km high, but I tend to aim for 45 km for aerobraking. If you've done a gradual gravity turn, it shouldn't take too much more dV for your final stage to circularize your orbit.

This is exact what I have been doing. When putting satellites into orbit between 80 km and 100 km I have no problem with the second stage re-entering the atmosphere. I placed small boosters on them so when I separate the second stage the boosters fire in retrograde. That is usually enough to slow the second stage so that it will eventually deorbit in one or two orbits.

For higher orbits (above 100 km) something else is required. I tried using bigger boosters, but after a second or two of firing in the desired direction they don't really have any control. The second stage could end up going anywhere.

It should not be too difficult to put together a small unmanned probe with a grappling hook and enough fuel to reenter the atmosphere with whatever it has attached. I was hoping I could avoid going that route.

Unforunately, KSP doesn't seem to like two unmanned control modules on the same craft. Otherwise it would be easy. When I separate the second stage I just take control and fly it back into the atmosphere, while my satellite goes on its merry way. But alas, it is not to be...

[Alaskan Glitch]

Originally posted by andylaugel:

Please excuse the 3 posts in a row, but I do find this topic interesting. Here is an example, using my usual low Kerbin orbit recovery rocket. Details vary slightly (antenna(s), probe cores, swivel/reliant/skiff, optional separatons on the boosters), but it's proven useful enough for 100+ launches in my careers.
https://steamcommunity.com/sharedfiles/filedetails/?id=732892664
I launched one of these in my most recent career to remove 2 pieces of space debris left over from before I got the Klaw for crew rescues. I don't claim to be the most efficient pilot, but here is how it went. I burned from launchpad, nosing down gently to the east until my Ap was 120 km at 2 minutes 20 seconds away. I then planned the circularization burn, which the navball told me would take 37 seconds. I waited, and then used up my last droppable stage with 350 m/s left on that burn, discarding it while the Pe was still below ground level. No space debris generated during the launch. I then completed the burn, getting a 72 km Pe.

From that 120 km Ap/72 km Pe orbit, it was a simple matter to rendevous with each bit of space debris, dropping the first one to aerobrake, restoring a stable orbit, then docking and landing the last bit of space debris. For LKO rendevous like this, it helps to know right-clicking a maneuver node toggles its mode, and the '+' button in the new configuration advances the maneuver an orbit.

I don't mind the posts at all. I also find it an interesting problem. It is not just an interesting problem, it also happens to be a real-world problem.

This web site displays all the satellites, rocket bodies, and other debris currently being tracked: http://stuffin.space/

At the very least we should be building into each mission a means to recover, or at least dispose of, rocket bodies. Otherwise it is going to get very crowded, and very dangerous eventually.

[A Terrible Modder]

Originally posted by Alaskan Glitch:

Originally posted by andylaugel:

Please excuse the 3 posts in a row, but I do find this topic interesting. Here is an example, using my usual low Kerbin orbit recovery rocket. Details vary slightly (antenna(s), probe cores, swivel/reliant/skiff, optional separatons on the boosters), but it's proven useful enough for 100+ launches in my careers.
https://steamcommunity.com/sharedfiles/filedetails/?id=732892664
I launched one of these in my most recent career to remove 2 pieces of space debris left over from before I got the Klaw for crew rescues. I don't claim to be the most efficient pilot, but here is how it went. I burned from launchpad, nosing down gently to the east until my Ap was 120 km at 2 minutes 20 seconds away. I then planned the circularization burn, which the navball told me would take 37 seconds. I waited, and then used up my last droppable stage with 350 m/s left on that burn, discarding it while the Pe was still below ground level. No space debris generated during the launch. I then completed the burn, getting a 72 km Pe.

From that 120 km Ap/72 km Pe orbit, it was a simple matter to rendevous with each bit of space debris, dropping the first one to aerobrake, restoring a stable orbit, then docking and landing the last bit of space debris. For LKO rendevous like this, it helps to know right-clicking a maneuver node toggles its mode, and the '+' button in the new configuration advances the maneuver an orbit.

I don't mind the posts at all. I also find it an interesting problem. It is not just an interesting problem, it also happens to be a real-world problem.

This web site displays all the satellites, rocket bodies, and other debris currently being tracked: http://stuffin.space/

At the very least we should be building into each mission a means to recover, or at least dispose of, rocket bodies. Otherwise it is going to get very crowded, and very dangerous eventually.

get BD armory and shoot that (poop) out of orbit, also how have you mannaged to kesslerise your save file ?

[Alaskan Glitch]

Originally posted by RoofCat:

adding or reducing droppable tank size you can program your ship to empty them just around the right time. Like 2200m/s for the first stage so second one needs only 90m/s for LKO.

Then going to Mun. You know transfer burn is around 856m/s from LKO and can create direct Mun hit. Burn for impact, decouple used stages/tanks in the prograde direction to decrease their Pe even more (you can radial decouple one by one rightclicking). Then burn for like 0.001 fuel unit Retrograde to get Pe back to 25km for your lander.

You will need ~270m/s for circularization and 550m/s+ for landing. Now in case you intend to drop some more, anything between 280m/s and up to 900m/s will do just fine, as you can drop tanks even with some fuel left if you are really that good at suicide landing. Have at least 20m/s or 1km while doing so and they will crash for sure.

There is no need for accurate math either. As you fly your ships you will notice velocities and spots where those tanks run dry. Adjust a bit and have clean sky.

You can design Mun and Minmus landers that don't eject anything outside Kerbin atmosphere and go all the way from high suborbital to Mun to reentry on one tank. All vacuum stages allow that. Just keep payload (pods, legs, chutes, science, etc.) plus engine mass below 1/4 for Terrier and Poodle.

You could use the solutions SpaceX uses - retroburns. Decouple your stages at ~10% fuel left. They are empty, light at that point and won't have payloads attached anymore. With those ~10% fuel they can do wonders because of that. You main travel route will suffer quite some though. As those 10% may count for some 20% delta v even with all the payload on. Due to how mass works in spaceflight.
Considering Obert effect, you may lose half the Ap altitude or even more. That's why on heavy payloads and high geostationary orbits SpaceX doesn't recover stages - they just push those last 10% to the limit practically doubling the orbital altitude available for the whole package.
You will need some probe added to each Lf booster for that and a radio connection. If you use radial booster stages you can avoid probes positioning your ship properly retrograde and starting engines on them the same time you decouple - you can move stuff on stages even after launch. Just set your thrust level in advance too - you don't need them starting with explosive and wild powers close to your payload. You may also need to adjust softer decoupling forces.

Another way is to blow stuff up making it hit each other. Less predictable, but for example if you decouple radial solid boosters just seconds before they end burn and have attached them in the right spot, they are likely to boost past your ship and hit each other slightly ahead of it (because they pull mass in the middle and are naturally tilted in that direction even if so slightly). I would rather never do that in real world, as an explosion always leaves something... but in KSP it is doable :D
There is just some randomness in every such explosion and you may fail deleting everything eventually.

Wow! That is a lot of useful information. I have tried overbuilding my rockets so that they have more than required delta v to reach orbit. On an equatorial orbit around Kerbin I get 2.265 km/s maxmum velocity before I cut off the engines at ~59 km and coast (heading for an apoapsis of 120 km). I have a TWR of 1.52 pre-launch and a TWR of 1.83 after circulization, with lots of fuel remaining.

I have tried to add an unmanned control module to the second stage, so I could control it after separation. However, I was not able to take control of the second stage after separation and I'm not sure why. So I started working on other solutions (like putting small boosters on the second stage to fire in retrograde when I separate the second stage).

I have had collisions like you described, although not by design.

The other planets, moons, and asteroids are less of a problem only because I haven't had as many launches to those locations as yet. If I can't design the mission to recover the components, then I fully intend to crash unneeded components into those planets, moons, and asteroids to clean things up.

I have also included either a small monopropellant or LFO tanks and a small engine on my satellites so that I can eventually deorbit them when I no longer need them.

Thanks for your very useful suggestions. I did notice that there were a lot of SpaceX parts being tracked. They were all on very elliptical orbits, which is the oribit they usually take when they want to place something in high Earth orbit. Usually I will do my circularization burn with the second stage still attached. So elliptical orbits aren't a good option for me.

[Appy Juice]

Why don't you just add stuff like science, antennas and stuff to the parts that you know will stay in orbit. More satellites and more science

[MeanJim]

The best way is not to put junk into orbit to begin with. If you're just launching satellites, try to design your launchers so the booster stage almost gets you into space (or stop the burn before it's in space) and add a small engine and fuel to the payload to take it the rest of the way. If you need an upper stage for heavier or higher orbits, give it a probe core, power and enough fuel to de-orbit itself once it drops off its payload. As for the junk that's already there, as others mentioned you can delete it from the tracking center, but IMO that's cheating.

I had your problem back when I first started playing KSP (alpha 0.20). Back then, there was no career mode, it was just sandbox, and the Klaw didn't exist. I decided I wanted to see if I could get a small satellite into orbit on my own without reading or watching a video telling me how. I actually made orbit on my first attempt, but it was a messy, highly elliptical retrograde orbit with about a 30° inclination. There was plenty of fuel left, so I wanted to de-orbit the launch stage, but when switching to it, I couldn't control it because it didn't have a probe core or power, but being a noob I didn't know exactly why. After that I consulted some sources on proper launch, and it turned out I almost got it right, except for going retrograde.

My next goal was to launch the satellite into a proper orbit without leaving debris, and to make a long story short, it took me 4 more tries before I got it right. Now I had all of these junk spent stages and useless satellites in orbit and decided I wanted to get rid of them.

As I said, this was in the alpha stages of the game pre-klaw, so I had to design my own. I sent up a few single-use prototypes, the first using landing legs to try and grab the debris, but I didn't know that the landing legs used had a known bug of disappearing when switching to the craft. I ended up just nudging the junk out of orbit. That lead to my second design to use a large flat surface and just nudge stuff. I think I got lucky on that first one because this second design I kept having the debris slip off, but I dd finally manage to deorbit it.

Then I decided to build my own catching mechanism, something that could grab the debris without it getting lose. I came up with a design that worked so well that even though it was intended for single-use, I was able to de-orbit two pieces of space junk with it. I then decided to scale it up and make it modular and create a permanent craft that I could leave in orbit to de-orbit the rest of the debris and future debris. It would be able to be refueled and I put the catcher mechanism on a large docking port so I could switch it out if I needed to come up with a better design (which I did).

I successfully de-orbited the rest of the debris, with only one re-fueling operation. I even decided to use it for my first Mun mission. All I had to do was detach the de-orbiter tool, send up a command module and lander to dock to it, and it was just able to get me to the Mun and back.

If you look at my KSP screen shots and scroll to the oldest, the first screen shot was the first ship I sent to attempt to de-orbit something, and it follows my progress through cleaning up and going to the Mun.