Multiple ships aerobraking at the same time?

[lantay77]

Can multiple ships aerobrake at the same time? I'm sending 3 ships at the same time to Jool and I'm wondering if they will all aerobrake at the same time. Or will only the ship I am controlling aerobrake and the other ships continue on rails?

Edited December 25, 2013 by lantay77

[Dave Kerbin]

The other ships will continue on rails (and so they won't brake and could be deleted if they pass within a defined distance from the 'surface') unless they are within 2.5km of the ship you are controlling. If they are within 2.5km when you start but they drift away while you are still in Jool's atmosphere then they will be deleted the same way 2nd or 3rd stage boosters are when you are taking off from Kerbin's atmosphere.

[Kanddak]

Just as you might have noticed with debris left around Kerbin, only the vessel you're controlling will aerobrake.

[federicoaa]

Only the active ship and everything around 2.5km simulate physics. Besides, everything not in focus that goes below certain altitude will be removed (the game supposes it will crass or burn in atmosphere reentry).

So, if you send more than one ship to aerobreak, what will probably happen is: your ships don't aerobreak, your ships disappear, or a combination of both.

What you should do is: when your ships enter Jool SOI, use corrective manouvers to delay the aerobreaks, then control each of them individually to ensure all of them survive.

[Cashen]

As other people have said, you need to stagger your arrivals so you can control each ship as it aerobrakes. Fortunately, even if you send multiple ships on the same transfer window, with their ejection burns staggered by a few minutes, by the time they arrive at Jool they will probably be staggered by hours/days already. It's very rare that two ships that leave within a few minutes of each other will also arrive within a few minutes of each other. So you should be fine. In the case of one vessel that will split into multiple vessels (such as multiple probes traveling together, or a multi-part ship), have it aerobrake as one thing before splitting up.

[Superfluous J]

Depending on your mission profile, you could also do your main aerobrake with your probes connected, and then detach them later.

I *just* uploaded a video (well, it was like 2 days ago) of me doing something similar (No aerobraking, but I got a lucky pair of encounters that got me in orbit anyway) in my YouTube Series, and it worked great.

.

[thereaverofdarkness]

If you have all three ships right next to each other on almost exactly the same trajectory so that there is no significant drift, then they might be able to aerobrake together. If they are all pointing the same way and have SAS on, and are all the same design, then they will drift the same way and should stay together. Very tiny differences can pull them apart however. But even if they drift outside the physics range during aerobrake, they can still have aerobraked successfully. If your active ship gets through the whole aerobrake but the others drift beyond 2.5km, they will stop aerobraking and fly on their last trajectory on rails out of the atmosphere. If they got enough slowing, they'll stay within the Jool system and you can take them back down a second time. If they all left 2.5km at a slightly different time, they will come down at different times.

It shouldn't be that difficult to aerobrake multiple ships together if you're careful and thoughtful.

Edited December 25, 2013 by thereaverofdarkness

[Cashen]

Just another quick addition. Because Jool's sphere of influence is so large, you can make tiny tiny correction maneuvers far away from the planet to force your ships to stagger their aerobraking quite easily. I always prefer to aerobrake ships individually, because if you fail to be captured on the first pass it means expending fuel to get captured, and that can be bad if your mission is limited by fuel (this was part of why my Gilly probe failed, because I had to burn fuel to be captured when the aerobraking failed because the two probes were passing Eve periapsis within a minute of each other).

[Dogface]

edit -

Edited December 26, 2013 by Dogface

[lantay77]

Thanks everyone, I think I can stagger my ships enough so that they arrive with enough time apart.

[celem]

I have a used stage (with a command pod) that I left in a Kerbin orbit of 53x310. Several months later it is in an orbit of 53x110. So, it is doing a very slow aerobraking, completely unattended. The Pe is high enough that the stage does not get classified as debris, and deleted.

Yeah i've seen this too around Kerbin. I suspect that what is happening is that you are passing close to it during various launches/orbits of crafts you are actually flying and it is getting caught up in the physics.

I left a similar spent stage in a similar elliptical jool orbit and it never shifted over 5 game years (since i didnt send any more ships to jool).

[Soda Popinski]

Of you're not opposed to mods, Scott Manley mentioned one that extended the 2.5 km bubble out to 100km. Was it the Lazor system?

[lantay77]

Of you're not opposed to mods, Scott Manley mentioned one that extended the 2.5 km bubble out to 100km. Was it the Lazor system?

I don't think it is lazor system, I have it and it does not seem to have an option to do this.

[FenrirWolf]

Nah the option is there for Lazor system. Its in the space center scene and referred to as unload distance or something like that. I don't recall since its been a long time since I had that mod installed, myself.