Haven't played in a couple years : is hard-docking possible yet?

[egoego]

1 hour ago, sieve said:

Are those conic white things that support the motors stock? I keep seeing them everywhere 60 hours of gameplay later I still can´t figure wich part it is lol

Those seem to be Tail Connectors: http://wiki.kerbalspaceprogram.com/wiki/Nose_cone

[KerikBalm]

11 hours ago, SomeGuy123 said:

Reasons include : game has unrealistic wobble on spacecraft coming in for a dock, wobbling your docking port side around from feedback.  Game doesn't handle time warp physics the same as regular physics, so time warping to skip a slow and boring approach will often end up with you farther from your target than when you started.  Game lacks adequate automation tools and mechjeb has problem as it is tied to the faulty game. 

The wobble is fine (although I too wish that docking port connections were stiffer after they've been made)... that SAS itself could use some work to stop oscillations that are basically like "PIO" in aircraft... manual control can halp here to prevent the wobble,

Also, you can help stop the wobble by selecting "control from here" on various parts.. because if you use the wrong part as a control point when the rocket is flexing (particularly underacceleration), the SAS will not make the correct maneuvers, and the navball display will be misleading... again... manual control is a solution here (as is balanced RCS and such)

The time warp is just fine... I suspect you are trying to simply move in a straight line to your target.. which works for short timescales and distances... but not over large distances or time... orbital mechanics doesn't work that way... you blame the game when it is behaving correctly.

Don't feel too bad though, NASA had the same problems:

https://en.wikipedia.org/wiki/Space_rendezvous#First_attempt_failed

" the Gemini 4 attempts at rendezvous were unsuccessful largely because NASA engineers had yet to learn the orbital mechanics involved in the process. Simply pointing the active vehicle's nose at the target and thrusting was unsuccessful. If the target is ahead in the orbit and the tracking vehicle increases speed, its altitude also increases, actually moving it away from the target. The higher altitude then increases orbital period due to Kepler's third law, putting the tracker not only above, but also behind the target. The proper technique requires changing the tracking vehicle's orbit to allow the rendezvous target to either catch up or be caught up with, and then at the correct moment changing to the same orbit as the target with no relative motion between the vehicles (for example, putting the tracker into a lower orbit, which has a shorter orbital period allowing it to catch up, then executing a Hohmann transfer back to the original orbital height)."

TL:DR ... slow approaches straight to your target will end up with you missing your target if your craft is moving along a significant portion of its orbital trajectory during that time.

Lastly... use "puller" designs, or change the fuel drainage so that most of the mass stays inbetween the source of thrust and the docking port.

For example... this:

I couldn't launch it all at once... I had to launch it in two parts and dock them in orbit:

That in line 2.5 docking port has adequate strength, as long as i have the fuel flow the right way.

That KR-2L puts out a lot of vacuum thrust... but the inertia of the 3.75m kerbodyne tanks provides enough resistance ... ie the acceleration is low enough, that even with the heavy payload in front, it could withstand the stress... but as the fuel burned off and acceleration went up, the docking port starts to flex, and the SAS can screw it up.

The solutions: control from the rearmost docking port... so that the control point is always actually facing the way the engine thrust is.

Run the 2x LV-Ns at the top of the payload to help reduce the strain on the docking port (they pull... but not much compared to the push from the KR-2L... but it stil helps).

Have the engine drain fuel from the section in front of the payload/craft (which in this case contains a lot of LF, but very little oxidizer). As the secton in front of the payload gets lighter, its less strain on the docking port... if I disable crossfeed on the docking port, and have the rearmost kerbodyne tanks run empty, the docking port will not be strong enough. Instead I let the oxidizer in the 3.75m tanks run nearly empty, but keep their LF full and use LF from the front of the craft. Then when the burn is complete, I transfer the LF back to the front section, and undock the rear section. The rear section retains enough LF (plus any left over oxidizer) to retroburn with the LV-Ns to stay in kerbin's SOI and aerobrake for refueling and re-use (its there as a reusable first stage for my moho mission.. the mid section is a moho station... yea... I'm putting a station in moho orbit, and all thats left is a capture burn for less than 2.7km/s... I've got it made... with enough fuel for 3-4 landings on moho).

 

Pull, not push whenever possible

Minimize mass ahead of docking ports when pushing, by playing with fuel flow

Use 2.5m docking ports

have you control point on the same section as the engines doing the thrusting to help keep the SAS from causing an oscllation

Manually override the SAS if it starts to cause oscillations

[Overland]

4 hours ago, SomeGuy123 said:

How do you take advantage of the wobble?

They make good stock flexable joint couplings.. If they were as rigid as say hard dock etc then itd seriously impact engineering possibilities  for say rover supension..train couplings and the like .

Dont get me wrong though theres definately a need for a proper docking part..but some of these quirks to kerbalised parts your unhappy about form the foundations to other craft outside of stick shaped space stations

 

[Corw]

12 hours ago, SomeGuy123 said:

I would prefer a "target movement mirror" mode.  You approach a target.  You choose "target mirror".  Once you are close enough, your spacecraft control thrusters make tiny millisecond burns so you stay exactly at the same orientation in position relative to the other spacecraft, auto-correcting for phasing from orbital mechanics. 

This would drain your RCS fuel but in real life the dV corrections would be so tiny you could do this for months.  

You then can go into a docking mode where you can specific position changes.  The integral of acceleration is velocity, and the integral of velocity is positon.  So this would be a control scheme permitting you to control 2 integrations up.  You have a GUI that ways "you are 5 meters back, 2 meters up, 10 meters left" essentially, and you can say "move 10 meters right".  A tiny puff of gas, and you begin moving to the right, automatically at the end of the maneuver you come to a stop exactly 10 meters over.  

Same thing for angular differences.

I suspect, though I don't know this for certain, that the computer-assisted docking the Soyuz modules use does exactly this.  

You wouldn't need cheat magnets because one you align all 3 rotation axes and 2 of the translation axes, the only difference between your 2 docking ports is distance on a single axis.  Your spacecraft is continuing to burn a tiny trick of RCS to keep you here.  You then just do "5 meters forward" or whatever and boom, docked.

Your "mirror movement" already exists. It is called properly orientated docking target. If you turn your target vessel so that target docking port is perpendicular to orbit direction, you and your target will rotate in same way, so all you have to manage is your position left/right up/down. I have been using that for over 2 years. Here is a vid at relevant time

 

https://youtu.be/nlG-N35u1KQ?t=8m36s

[sieve]

4 hours ago, monophonic said:

Tail connector A under aerodynamic parts. Very stock and in the basic plane parts tech node.

Wow how can I be so blind xD thanks a lot!

[Hobbes Novakoff]

On December 11, 2015 at 1:27:36 AM, monophonic said:

Tail connector A under aerodynamic parts. Very stock and in the basic plane parts tech node.

@sieve It was probably remodeled in 1.0.5 though. 

[Scotius]

I once hauled this to a low Solar orbit. These are two solar power plants, with a 4xLV-N nuclear tug in the middle. Payload is connected to the hauler with Clamp-O-Tron Sr's. If that abomination held together during some awfully long burns, then wobble situation in the game is not so bad

Edited December 15, 2015 by Scotius

[Commander Zoom]

"Tractor" configuration definitely helps.  I tried sending a few long-ish vessels on their way with thrust from the rear, or even the middle, and they tended to sway and flop around much like you'd expect of any large, unsecured, semi-rigid structure - such as, infamously, some suspension bridges.   (They didn't come apart, though, and the oscillations tended to balance out over the course of the burn, and ended not long after it did.)

tl;dr - don't try to push a noodle.

[cantab]

In terms of spacecraft and station rigidity I think the big one is that update 0.23.5, released April 2014, significantly stiffened all the part joints. You no longer need to be using loads of struts all the time. While docking connections still aren't quite as rigid as VAB-built joints, they're stiff enough for most sensible uses.