Airdocking?

[bhauth]

edit: The main idea here was docking to a craft slowly descending with parachutes, and that doesn't work because craft in atmo, even if they have pods, disappear at too short a distance from what you're flying. Nevermind, I guess.

Something that's a challenge on its own and might make lighter Eve landers possible: "airdocking". Basically, use one craft for initial takeoff, and then rendezvous with another one before reaching orbit.

Apparently "zephren-kerman" had this idea before I did ( http://www.reddit.com/r/KerbalSpaceProgram/comments/2196wt/seat_of_the_pants_presents_the_dung_beetle_it/ ) and was trying to land Kerbals on platforms on parachutes. I think it would be much easier to instead use the new AGU, and just fly the lander into the other craft.

There are 2 options for docking:

- suborbital rendezvous

- lots of parachutes, detaching a lander that does a "suicide burn", quickly planting a flag, then coming back up

There are several options after docking:

- use enough control wheels to counter off-center mass

- manual engine throttling to counter off-center mass

- transfer a kerbal over

- a fuel tank with parachutes, transferring fuel to the lander then detaching

What do you think?

Edited May 11, 2014 by bhauth

[r4pt0r]

i think flying the non lander craft while also landing the lander will be hard. also what of the fuel usage for the non lander?

[bhauth]

Those problems only apply to suborbital rendezvous, not to docking with a non-lander with parachutes.

[Pecan]

You might like to read the threads on inflight refuelling in regards to this eg; http://forum.kerbalspaceprogram.com/threads/74169-Has-anybody-ever-managed-Aerial-refueling). LOTS of parachutes may make it easier but I'd think Hooligan Labs' (mod) balloons would be better as they could give your non-lander neutral bouyancy.

PS: What is "the new AGU"?

[bhauth]

Pecan:

That thread is for docking aircraft in flight.

AGU = Advanced Grabbing Unit = Klaw

Yeah, balloons might be easier, but I was thinking about the possibility of lighter stock Eve landers.

I made a craft with a lander that splits off from a fuel tank with parachutes, and tried testing it on Eve. I put a probe core on the fuel tank, and set it as a target while flying the lander, but I lost the target when it got ~1.5km away and I didn't see the fuel tank on the orbit map either. Anyone know what the problem is there?

[brianorca]

Anything more than 2.5km away from your vessel is destroyed if it is still in atmosphere. Too far away, and KSP stops calculating physics for it, but it also can't put it "on rails" while in atmosphere, so it gets deleted. I think there's an .INI file you can change that distance, but I haven't tried it, and it may affect performance if you make it too big. You generally don't want KSP to do physics calculation for every stray ship that flies overhead the launchpad, for instance, as it would really slow things down.

[Pecan]

AGU = Advanced Grabbing Unit = Klaw

Doh! I only ever think of it as 'claw' and never recognise the real name. Thanks for that.

Anyway - it's an interesting idea and I look forward to seeing how you get on with it. The reason I pointed to the inflight threads is just for information about the problem of controlling (or even having) two vehicles in an atmosphere at the same time. Good luck.

[Claw]

You still have to have enough dV to "catch up" to the craft dipping into the atmosphere. I would also guess that chances are that craft will be traveling faster than the typical circular orbit speed because it would need to be in an elliptical orbit in order to ensure escape from the atmosphere. So while you would need less dV to get up to orbit, you would need more dV to catch up to the mothership's orbital speed.

You could conceivably have a ship in a close orbit, but outside of the atmosphere. The lander could take off and rendezvous at the top of it's parabolic launch. The ship in orbit could slow down to catch the lander, grab on, then accelerate away back into orbit. I'm not sure how much this would "save" you in total, but I suppose you could set it up so that your lander needs less mass to escape from the surface.

[Northstar1989]

There is a *third* option of sorts- if you can get a plane (a rocket-plane on Eve perhaps, or one powered by Thermal Turbojets with KSP-Interstellar) into a circular trajectory in the upper atmosphere where its peripasis is always above the altitude at which unloaded craft are deleted, then you can unload it and it won't disappear even though it never leaves the atmosphere...

I say a plane because planes expend a lot less fuel maintaining a given altitude, and are much more "floaty"- meaning when you send up your craft to rendezvous with it, it will be much easier to dock with.

I suggest, on Eve, using a large plane with enormous wings (for high endurance) in level flight and a circular "orbit" for the mothership (power it with a single NERVA or Thermal Turbojets). Provide it with an ascent vehicle capable of reaching orbit, or make it capable of reaching orbit itself.

From the mothership, deploy a much smaller/faster plane to descend to the surface. Start out with it attached to the belly of the mothership via docking port or decoupler, for easy deployment, and have it dive down to the surface in a steep dive immediately after being detached... (you can actually use lift to INCREASE your rate of descent if you dive with a winged craft from orbital velocity) Land as quickly as possible, grab samples, and fly back up to the mothership.

Transferring your Kerbal over is the hardest part- it's probably easiest if you either (a) Make the mothership capable of reaching orbit, so you don't have to bother in-atmosphere (simply dock to the mothership and then scramble up to orbit) or ( Use a mod that allows crew transfers between docked craft without EVA.

If you opt for an all-stock approach, probably the easiest solution is to give the smaller plane a "Klaw" radially mounted to face upwards, and simply have it fly into the belly of the larger mothership (preferably close to its Center of Mass).

If you use mods, another possibly is to simply create a really enormous mothership using B9 Aerospace with a cargo bay large enough for the lander-plane to simply fly into- at which point you can ditch the Kerbal on EVA and have him grab onto conveniently-placed stock Pegasus ladders or command pod doors to have him stabilize with the mothership- while the lander can simply be allowed to roll/slide out of the rear of the cargo bay with a little well-planned pitching on the part of the mothership...

If you wait too long on rendezvousing with the mothership, though, you'll have issues with its heading relative to the horizon (and thus the Angle of Attack of its wings) changing while it was unloaded- since heading in KSP is maintained relative to the galactic plane (a vessel pointed prograde on one side of a planet will be pointed retrograde if loaded back up when it has orbited to the other side- and don't even get me started on the complexities if you leave a craft unloaded for a significant portion of that planet's revolution around the sun...) So you still need to get back up to the mothership as quickly as possible, unless you want to risk loading up the mothership where it is in an Angle of Attack where it will instantly enter into an unrecoverable spin...

An afterthought: KMP or a similar multiplayer mod would simplify the mothership tactic IMMENSELY (simply having a pilot to keep the mothership's angle of attack constant while another player pilots a smaller plane to the surface would prove invaluable...) In single player, ANY airdocking strategy is enormously complex, and hardly worth it except maybe for awesomeness-factor or a challenge...

Regards,

Northstar

[chicknblender]

Hey bhauth, did you ever have any success with this? The initial comment on Reddit that you linked to was from my post, and I have been seriously thinking about making this happen. I would love to hear what if anything you learned about this technique.