Can't Dock

[Wes]

Hey Guys,

Please help in docking? I just cant seem to do it! How do you just position your ship at the last square and "hold"?? I
keep flying around the ISS - then my CVEL goes Negative very quickly - Its as if im doing loops around the ISS and
cant seem to stop and hold!

Is there nothing out there that does all this for you?
Please can someone help with detailed instructions - It would be greatly appreciated!

Thanks so much,
Wes.

[AphelionHellion]

I'm not quite sure how far you're getting in the docking process, so I apologize if my suggestions appear pedantic or
cover ground you've already tried. It sounds like you're over/undercompensating at the wrong times - this is very very  
very easy to do if you're new to the docking game

The main thing you need to to, to make sure you don't overshoot, is use the docking HUD to get your relative velocity
down. 180 degrees from the "+" symbol (which is your forward vector in docking mode, for some reason it looks like
the retrograde symbol) is the "(+)" prograde symbol, which represents the direction you're coming from relative to the
object you are docking with. It should have a number representing your total velocity. I like this better than CVEL
because if you're moving laterally it won't drop off and reverse itself when you pass the axis of the station. Whichever
direction you're moving, if you aim your nose straight at the prograde symbol and burn your engines, the number will
drop. When it gets to within 4 m/s of zero, you're nearly stationary relative to the station.
The trick is to get within 15 kilometers of the ISS and use this method to reduce your speed and make final
adjustments so that your forward velocity symbol takes you right to the station - then get closer and do it again at
about 2 or 3 kilometers. From there you should be able to ignore orbital motion more or less altogether and slowly
approach for final docking.
One thing to remember is that everything you do in terms of acceleration you have to match in deceleration. So
instead of cranking up your relative velocity to get near the station quickly and then having turn around and
decelerate again, do your final approach at as low a speed as you can handle and use 10x or 100 x time acceleration
to coast in. Ever watch NASA TV? I love the subject matter, but it's boring as all get out:

Ok, they're about 20 meters from that satelite....
...
...
...
....................
19.9 meters...
...
...
....................
19.8!...
...
...
...
.....................
are they even moving??
...
...
...


If you want to do it by the books, NASA style, painfully slow is the way to go

That being said, if you want to cheat and do things the easy way, download the Attitude MFD. Among other things it
has a function that works much like killrot, but instead of killing rotation, it uses the engines and thrusters to null
your velocity out to zero, relative to any object you choose. It's extremely handy
Here's one place - I think it's mirrored somewhere but I couldn't find it elsewhere right now
http://filebox.vt.edu/users/cknestri/Orbiter/AttitudeMFD-090602.zip

Just curious, how close to the ISS have you been able to get? In what ship? And whats your lowest total relative
velocity as shown by the HUD velocity vector?



Post Edited ( 07-12-04 02:00 )

[Wes]

Hey,

Thanks so much for responding!!  

OK:
"The main thing you need to to, to make sure you don't overshoot, is use the docking HUD to get your relative
velocity
down. 180 degrees from the "+" symbol (which is your forward vector in docking mode, for some reason it looks like
the retrograde symbol) is the "(+)" prograde symbol, which represents the direction you're coming from relative to
the
object you are docking with. It should have a number representing your total velocity. I like this better than RVEL
because if you're moving laterally it won't drop off and reverse itself when you pass the axis of the station.
Whichever
direction you're moving, if you aim your nose straight at the prograde symbol and burn your engines, the number will
drop. When it gets to within 4 m/s of zero, you're nearly stationary relative to the station."

That I can do - when It reaches zero, I point my nose to the ISS and Im usually about 150km from the ISS! Once I'm
facing the ISS I pop some thrust to get my CVEL to about 300 - I think thats too much though! I use Killrot to stop my
ship (DGI), but that darn ISS keeps moving! Its hard to explain! Im always flying circles around the darn thing! I
cant seem to come to a "dead stop" and move at the same speed as the ISS and in the same direction! I have
no idea if Im explaing this right!

I have absolutely no idea how to get to that last green square and "hold" <-- They make it sound so easy!!

I think i'll cheat just for awhile while I get used to it - I've got the AttitudeMFD", but how do I activate it? And use
it?

The closest I've been to the ISS is 8km, but Im not stable! Im still doing loops around the ISS at that stage
with my CVEL being positive and then negative and then positive and then negative and then I run out of
fuel!  It will be a miracle if I can get to 2-3km and be stable!! WoW! I envy you guys that can do this! JeeZ!

Thanks again so much for helping!

Wes.

P.S: I live in South Africa, Cape Town, so we dont get NASA TV! I wish we did - It sounds really interesting!  

[harmsway]

Like you I had a difficult time with this. So once I had it licked I wrote down what help me and posted it on this web page.

http://www.eharm.net/shop/freeware/orbiter/tutorials/orbiter_instrument/docking.html

But make sure you are sync first

http://www.eharm.net/shop/freeware/orbiter/tutorials/orbiter_instrument/synchronize.html

Gene

[McBrain]

good tutorials, harmsway!!

I myself NEVER first go the to last green square!
I just set 10° FOV at about 10km distance and change my trajectory with the linear RCS thrusters to fly directly in front
of the docking port I want to dock. Then I close with about 20m/s and short before I arrive I burn retro to null out my
relative velocity. Then I align with the port and dock. It's the fasted method for docking.

No offense to you, Wes!
Just try to manage to dock as described in Harmsway's tutorial.
When you can dock without any tutorial, try my method.

If you want to do it "properly", you should first go to the last green square!
But if you're too lazy...

[Wes]

Thanks so much Gene! Ive printed it all! But, how do you stop all Relative Velocity?

Thanks again,
Wes.

[Wes]

LoL - JeeZ - You make it sound so easy!!

Im willing to try anything at the moment!
Thanks McBrain!
Wes.

[McBrain]

You can stop rel. vel. by pointing the ship towards the green cross (the + velocity indicator) and burn the retro thrusters, or you can point the ship towards the green circle with the cross in it (the - vel. ind.) and burn the main thrusters.
I assume you have docking HUD and you've set up the correct frequency from the ISS.

[Wes]

Hhmm - Interesting!! Yes, I have the Docking MFD and HUD up and tuned in all the frequencies! Thats something I
can do!! Although, Im still getting used to the Docking MFD and all its terms and what to do with it!

So, when do I use Lin and Rot thrusts?  

Thanks again,
Wes.

[McBrain]

When you are near the station,(I hope you managed to get near to it and "hold") you should rotate your ship towards the station with the Rot RCS (rot = "rot" ate you ship") then you should aproach the station by using RCS in Lin mode
(lin = "move" your ship). The forward lin rcs thrusters are applied by pressing "6" on the keypad.
With "8" you can move down, with "2" up, with "1" and "3" move left and right".
In the docking MFD you can align the ships attitude to the docking port by rotating until the white cross (with horizontal and vertical line) is in the middle and the white arrow at the edge of the circle pointing exactly 90° upwards.

Then you have to try to position the ship in the approach path. The green cross (with 45° angles) should also be in the middle of the circle. You have to try which lin thruster acts how on the ships movement. The best method is, change to external view and align your ship roughly by visual judgement. then go inside and fine-tune your position.
when perfectly aligned, you can thrust forward with the lin rcs.
while closing, watch the align crosses and try to hold them in the middle. Final docking speed should be around 0.1m/s
that means, 10cm/s.

Hope this helps,

[Wes]

Hey McBrian,

I just tried it and WoW - I did MUCH MUCH MUCH better!!!!  

I got within 2.5km of the ISS and was pretty stable!! Just the green squares were below me, but I just read your
post again and I should have pressed "8" in Linear!

Also, when do you request clearance to dock? I pressed CTRL-D, but nothing happened?!
Also, the only thing that didnt show up was the big red cross? Why's that? Does it only show up if you're really close
to the last green square?

Also, when I was near the ISS, it always slipped away, but very very slowly - Is that normal, or is there a way to
make the movement come to a complete stop? If so, how?

Thanks so much for your help,
Wes.

[McBrain]

1. I'm McBrain, not McBrian!

2. I'm glad that I can help you!

3. You don't have to request dock clearance with stations implemented as vessel.
Earlier there was special "station classes" for stations, where you had to request permission before the docking ports
were activated.

4. I don't know if the crosses only show up when close to the approach path. Just try to head to the station when you're
stable close to it. Then maneuver to the last square with the lin rcs.

5. If you're not docked to the station you will always float away, because your orbit differs slightly from that one of the station. There is no way to stop completely, apart from docking.

6.

Thanks so much for your help

No problem, that's what we are here for!

[Wes]

Guys,

Thank you Thank you THANK YOU!! I actually managed to dock - right now!! I cant believe it!  Now theres more of
this:   and less of this:  

I didn't realise that Linear thrust was so important! I'm just hoping it wasnt beginners luck!!
This has made my week!
Thanks again!  

Cheers,
Wes.

[McBrain]

No problem!
As said before: We're here to help!

BTW: What about register and join us?

[reekchaa]

Yes... JOIN US, Wes!!!!  



...If you only knew the Power of the Dark Side!  

[McBrain]

You can't beat us, Wes, you know that!
It'd be better for you to join US!

Henceforth you are MY disciple!!
MUHAHAHAHAHahahaha....


Bah, forget it! Feel free to join us!

[McBrain]

Hmm, btw, Wes, I helped you, now can you ...... h.....hel....help me with a little problem I have?
The crystal of my lightsaber is broken and..... AARRRRGHHH!! I MUST KILL!!!! CAN YOU HELP ME?




Sorry Doc, , but I couldn't resist!

[Wes]

LOL - You okes (pronounced "oaks" <-- South African slang!) are crazy!!

CooL - I'd love to join!! Ill join now, actually - just gotta find out how...

Thanks guys,
Wes.  

[Wes]

Finally - I am one with the Universe!!  

[DanSteph]

Finally another padawan joined the DaRK SIDE !!!***

mhouahahahahah <- (mad laugh)

(*** anyone can change the light bulb ?... its broken )

Welcome Wes

(btw: I updated the database all your former post as unregistered user
are now taken in acount)

Dan



Post Edited ( 07-12-04 00:06 )

[AphelionHellion]

What are these "green squares" you speak of?
I just slide over to the docking port and make sweet mechanical love to that station
I guess if you want to do it the "safe" and "correct" way, you can use the green squares and docking MFD

Seriously Wes, if my experiences are any indication, with a little practice you'll be nailing those docking approaches
with just the HUD and your Mark 1 eyeballs every time
In other words, if I can do it, anyone can

[AphelionHellion]

Wes: Welcome to our syndicate of evil!

With regard to drifting apart from the station, it's actually sort of a cool way to visually see orbital motion at work.
If you get perfectly stationary relative to your target, but "north" or "south" of the target from where it's heading,
you'll start to drift toward the target until you go through it and wind up the same distance away on the opposite side,
then you'll reverse and go back again, since technically your orbital plane is slightly different than your target's.
Similarly if you're "above" your target (higher altitude above the ground) and perfectly stationary relative to it, you'll
drift "back" retrograde of your target, as it's in a very very slightly lower (and thus faster) orbit than you. Vice versa if
you're between the target and the surface, it'll appear to fall behind you as it's in a higher orbit.

I think the only way to keep perfectly still relative to your target over a period of many orbits would be for your center
of mass to be precisely aligned with the target's center of mass along the imaginary path of the orbit, at precisely the
same speed and altitude and a slightly different direction corresponding to the path of the orbit. In the exact
same orbit but slightly ahead or behind, in other words. This would be a heck of a lot tougher than docking, though,
and I don't think there's an Orbiter MFD to accomplish this feat

[DocHoliday]

Aha, I see you guys solved the problem in this thread. I started answering in another

Another thing Wes, in case noone told you so far:
1. You should always aim to make your initial approach to the station at about 100-50km. If it's more than that, you
aimed poorly and you should try to make another sync attempt. It's too difficult to "catch" the station otherwise.
2. Make sure youre relative inclination, RInc in Align MFD is as low as possible, preferably around 0, but not more than
0.05deg.
3. As you make your final approach to the dock, with luck, use CTRL with your RCS thruster keys (like CTRL-Num2) to
make burns with 1/10th the normal intensity. That is very useful when making small corrections at slow speed as the
speed indicator jumps around wildly.

Welcome aboard and cheers,



Post Edited ( 07-12-04 08:51 )

[Wes]

Hey Guys,

Thank again so much for all your replies and to Dan for updating the database for me! I really appreciate it!
Its great to be able to dock pratically and even better to know what you're actually doing in theory! Thanks for
explaining it!  

Today I fell through Space from the ISS to Mir! And managed to dock first time!!! It's so great when you
hear that noise it makes when you dock!  (I can't say much for Russian coffee though!)

"3. As you make your final approach to the dock, with luck, use CTRL with your RCS thruster keys (like CTRL-Num2) to
make burns with 1/10th the normal intensity. That is very useful when making small corrections at slow speed as the
speed indicator jumps around wildly."  <-- Thanks Doc - Ill keep that in mind, because I noticed how wildy the indictor
jumps!

I quite like using the MFD to dock, but I go "Spot View" (Flight Sim talk, I know!) JUST before docking so I can make
TINY adjustments!

Oh, yes - What I wanted to ask:
I want to go home now, so....how do I re-enter the atmosphere?? I can do the De-orbit burn, but unsure when to
stop burning and thats about as far as I can get! How do you know when to burn and for how long and not land in
the water? Is there a way to work it out?
Also, Im flying the DG3 (DGIII) (DeltaGlider 3) or something (Awesome spacecraft!) and whenever I re-enter the Atmosphere I burn
up! There is an Autopilot for re-entering, but when do you activate it? Or someone can explain to me how to do
it manually - That'll also be CooL!  

Cheers and keep well,
Wes.



Post Edited ( 07-12-04 20:45 )

[Wes]

Oh yes - The other thing:

I sent one of the dudes on a EVA (DGIII) and managed to work out how to control him with the joystick, but how do
you make him move forward? And more importantly, lol, how do you get him back in the ship?? After doing <--
that a couple of times, I leave the poor guy hurtling through Space all by himself!!

Thanks guys,
Wes.