Help docking DG to ISS

[startrekmaniac]

Okay Im trying to Dock to DG to the ISS. I just aligned my orbit now im trying to 0.01. Im now trying to sync my orbit with the sync orbit mfd. Anyway when I bring it up I get no Intersection. What dose that mean? Im I doing something wrong?

 

[dutchpirate]

are several options for intersecting using the syncorbit mfd. Click on the MOD button until you get sh-perapsis, then follow the manual/tutorial to sync your orbit. If you need a tutorial, try http://www.orbiter-forum.com/faq.php?faq=tutorials#faq_orbitertutorials

 

[Tex]

Okay Im trying to Dock to DG to the ISS. I just aligned my orbit now im trying to 0.01. Im now trying to sync my orbit with the sync orbit mfd. Anyway when I bring it up I get no Intersection. What dose that mean? Im I doing something wrong?

Hi startrekmaniac,

Please refrain from creating a thread with a one liner title like, "Help". Be more specific when titling your threads. This will vastly improve others in the future when doing a forum search. If you haven't already done so, please read the forum rules HERE.

Rule #1:

1. Creating Topics - If you have a question or problem regarding Orbiter or any addon, you may of course create a new topic, however there are some guidelines that should be considered before posting:

• Try to fix the problem by yourself first. If you have a problem, you should try some research to find the answer before creating a new topic. Reading the documentation supplied with Orbiter or the addon, will give a solution in most cases. You may also try a forum search for similar threads that may have already been created.
• Be clear, tell what you've already tried. If you have tried to fix the problem, but couldn't find the answer, don't hesitate to create a new topic. Specify what exactly you've found and where the problem rises.
• Pay attention to the content of the topic. If you don't have a problem at all, but would just like to start a discussion, then make a clear topic in which you substantiate your opinion or statement. Topics starting with a few words or one liners are not tolerated.
• Give your topic an appropriate title.
• Place the topic in the right forum. Topics placed in an inappropriate forum will be moved by the moderators.

I have renamed this thread from "Help" to "Help Docking DG to ISS"




PS: Dutchpirate gives sound advice there, start with the tutorials here:
http://www.orbiter-forum.com/faq.php?faq=tutorials#faq_orbitertutorials

 

[Urwumpe]

You can only have an intersection, when your orbit crosses the orbit of your target. As long as this does not apply, you should try the other references available for Sync Orbit - for example Sh-Pe.

 

[Biscuit]

It's probably a really fuel ineficient way of doing it, but what I like to do is get into a stable low orbit (around 140-180 km), align my plane with ISS.

Once I get that to 0.03 or less, I'll do a prograde burn to bring my ApD to within a few klicks as ISS ... bring up the 'sync orbit' MFD, set it to sh-periapsis then wait.

About 90 seconds before ApT, swing prograde, at approx ApT -20 sec start a full thrust burn.

Once my ApD gets beyond the ISS orbit, I'll let it run up until my second orbit equals usually ISS's third (sometimes fourth if the kids distract me). Engine cut-off, tweak the intercept timing with the translation thrusters ... then settle down for another wait. (The advantage for me is I don't need any special MFD's, and it's fairly easy to eyeball.)

When intercept is getting close: about PeT - 120 turn retrograde, then approx PeT - (however long the previous burn took), ignite the mains and burn like crazy.

I've started playing with also bringing up the docking MFD in the other window and using it to help get aligned during the sync-burn.

My best record so far is finishing the final burn 2.7 Km from ISS with a closing velocity of -25 m/s. (That was in the DGXR1, all settings at default, no SCRAM on ascent ... 8% fuel left at docking. Whew!)

I'm sure a lot of you guys that have been doing this for a while are probably reading the above and just shaking your heads. Hehehe Nothing really special, but's it's fun for me.

Now, if only I could figure out how to do a reentry without frying my ship to a crisp. (and start setting up for some station building eventually)

 

[startrekmaniac]

How do I take a picture of my mfd's? I dont know what any of you are talking about and if you have a look at my mfds you can help me. Sound good?

 

[polaris149Tiberius]

Im curious

I have found in RendezvousMFD documentation only 1 doc that is a simple readme. However it launched my research with me Wiking Rbar. I found this article Rendezvous pitch maneuver. It has some info at the bottom of the page describing that the shuttle approaches from Rbar and docks from Vbar. All this says to me is that the shuttle (and our various orbiter spacecraft) would do this too. But I found a link to a good wiki for Space rendezvous on that page. This is a good research page for rendezvousing in general.
It says (and I quote)

"The standard technique for rendezvous and docking is to dock an active vehicle with a passive target. This technique has been used successfully for the Gemini, Apollo, Apollo/Soyuz, Salyut, Skylab, Mir, and ISS programs. The active vehicle is first put on an intercept course with the target. The closure rate is then reduced by use of the active vehicle's reaction control system. Docking typically occurs at a rate of 0.1 ft/s (0.030 m/s) to 0.2 ft/s (0.061 m/s).[4]
Z-bar approach V-bar approach STS-104 was the third Space Shuttle mission to conduct a V-bar arrival at the International Space Station.[5]
R-bar approach Astrotech has proposed meeting ISS cargo needs with a vehicle which would approach the station, "using a traditional nadir R-bar approach."


This is not very much information and I think it needs to be added to but its a good start for some research.
I am curious if you are taking into account launch windows, which are very important if your conserving fuel,
and
if you are launching before the ISS passes over or after it passes. This will make a big difference in how much fuel you will use. Im not sure if a prograde approach is better or a retrograde approach is better but during sync and final approach Im sure this will determine how much fuel you have ..which will effect how much fuel you will have for re-entry and attitude control during re-entry.

I normally launch to an altitude that is lower than the ISS and at the correct window time which I figured was after the ISS passes and the ISS's plane passes over the cape and then wait until Im near the ISS like 400Km or so. Then I use rendezvousMFD to calculate a rendezvous with a low approach velocity like say 90m/s. When the period of the rendezvous process is over then I circularize using IMFD. Then I recalculate another orbit and find the lowest velocity possible with the lowest burn time. This works well. I still havent found the best window that saves the most fuel but Im real close and I think I have found a good roll proceedure for comming to the correct Inclination. If anyone has some good thoughts on this I would love to hear it. I have no idea what is the cheapest time or position the ISS needs to be to be cheap but I have found some good cheap burns when the ISS is past Canaveral, and the plane is approaching from the East. Just before that is the window I have been working with for the Space Shuttle Atlantis STS-101 with the carina in the bay.

I can get you on the surface safely if you have enough fuel to do the re-entry burn which will determine what AoA you will have overall during re-entry. It is importanto to note that I think you should be able to take some of the ISS's fuel as long as you take back some later -it needs that fuel for any manuvers it needs to make during re-entry.

Im currently working on a Space Shuttle to ISS process that I am documenting and can make it available after I finish it. The goal of my document will be to tutor a pilot to launch the shuttle Atlantis (w/cargo) to rendezvous with ISS, detach, deploy cargo, and land at the Cape. Im 98% done with the testing process and proceedure but as of yet I havent put it into document form. Ill like this thread to the document thread when I post it here.

 

[Tex]

How do I take a picture of my mfd's? I dont know what any of you are talking about and if you have a look at my mfds you can help me. Sound good?

You could use a program like FRAPS or simply press "Print Screen" on your keyboard. As soon as you do, you'll need to exit Orbiter, open something like paint, then hit Ctrl+V to paste the screen shot in paint and save as a JPG. Doing it this way you will only be able to take 1 screen shot at a time. FRAPS will allow you to take as many as you need as save as a JPG at the sametime. :speakcool:

 

[startrekmaniac]

Okay I uploaded the picture tell me what I need to do from here. Oh im still learning orbiter so I used unlimted fuel and I am useing the checklist missions. Quickstart, and im taking off when the mission opens.

 

[Tex]

Okay I uploaded the picture tell me what I need to do from here.

Going by the screen shot you posted...assuming your plane is already aligned with ISS you need to do the following:




1. Match one side of your Orbit altitude to ISS - Either PeA or ApA, which ever is on the daylight side I would suggest which from the screen shot looks like PeA.

• Select ISS as a target on your Orbit MFD.
• Look at ISS's altitude just as it crosses your PeA and write it down.
• Coast around till you reach your ApA.
• Burn either prograde or retograde at ApA to match your orbit altitude on the opposite side of the planet to ISS. Percision here will make docking easier. (If ISS is at 360.2K at your PeA, then your altitude should be exactly the same at that location.)

2. Sync Orbit with ISS

• Now that you've matched your orbit altitude to ISS at the point in your orbit where you wish to intercept ISS (your PeA), you can now use the Sync Orbit MFD.
• Target ISS and press MOD until you see Sh periapsis or Sh apopsis (choose the side which is at the same altitude as ISS which in your screen shot is going to be PeA, so choose Sh periapsis.)
• Finally coast around to the spot you selected and do your sync burn.
  • If ISS is behind you, burn prograde allowing ISS to catch you.
  • If ISS is in front, burn retrograde allowing you to catch ISS.
• Do your burn until *DTmin reaches '0'. You may have to use translation thrusters to hit 0 exactly. You want this number right at 0.

*If burning retrograde, watch your orbit altitude on the other side making sure it gets no lower than 150k!

[EDIT]Sorry, I missed a few details I added, if you already read the post you might re-read it.[/EDIT]

 

[Biscuit]

Okay I uploaded the picture tell me what I need to do from here. Oh im still learning orbiter so I used unlimted fuel and I am useing the checklist missions. Quickstart, and im taking off when the mission opens.

If I'm reading the numbers right, you're about 70 seconds behind ISS.

At orbital velocities, that's just a wee bit of distance.

I had that problem for a while ... that's why I like to do the bigger loop orbits.

Just get one of the numbers on the left side of the sync mfd to match one of the numbers on the right column (number of ship orbits and how much time vs number of target orbits and how much time).

You taking 1 large orbit while the ISS takes 4 would be fine, as long as the arrival times match up. (That's what the yellow numbers in sync MFD mean .... when you and your target will reach your intercept point.) That way, you both reach the same spot at the same time.

If your target line is at a point in your orbit that is the same height as the ISS (try adding the ISS as a target in your orbit MFD ... it helps) ... then all you have to do is make the yellow numbers in sync MFD match.

(feel free to tell me to shut up if I'm way off base)

.... seat o' the pants LEO flying ... gotta love it.

*update* following Tex's advice would probably be much better than trying to wade through my ramblings.

 

[startrekmaniac]

This would make much more sense if there was some kind of video tutriol on youtube.

 

[Tex]

This would make much more sense if there was some kind of video tutriol on youtube.

Take your time, re-read my post above as I re-worded some of it. Meeting ISS is not overly complicated and once you understand it, it makes perfect sense, but it takes a little time and patience to fully grasp every step needed to properly meet ISS.

 

[startrekmaniac]

Okay which one is my PeA? I mean on the orbit mfd.

 

[Tex]

I just threw together a quick video tutorial showing how to launch the DG4 to ISS. It includes everything from launch, plane align, matching altitude, and sync orbit.

If it proves to be popular I might re-make it spending more time on it as I made this in only 2 hrs and I might also make a few others. It's rendering now then I have to upload it so I'll post a new thread in the Tutorial forum with the video once it's finished in the next hour or so. I'll update this post when it's up.

 

[Master of Blades]

I reccomend "Go Play in Space" It's an easy to understand tutorial, with sample scenarions and playback to make things easier, it does not only bring up Rendevouzing but also all the basics, how to fly to the moon, interplanetary trips etc.

It also contains a great section on addons. I consider it a must-read for all rookiees (myself included D: )


Cheers

 

[startrekmaniac]

Thanks!! Just a few things, I was useing DG1. The first, useing the quickstart mission. Im going to try it again if someone would mined could someone look at see when I need to take off? Thanks again!!!

 

[Tex]

could someone look at see when I need to take off? Thanks again!!!

Watch the first part, I discuss that...

http://orbiter-forum.com/showthread.php?t=2055

 

[startrekmaniac]

I did, do I need to wait for it to fly over the cape? Or can I like you should in the video take off?

 

[pattersoncr]

You need to wait for the path of the target's orbit to pass over your launch site:
Bring up Map MFD.
Select ISS as target,
the yellow line is the ground track of the ISS's orbit.
the yellow line will slowly move as the Earth rotates.
You should wait until the yellow line passes overhead (or very nearly so).

Based on your earlier posts, you already figured out how to align planes. All waiting until the correct launch time does is make aligning planes easier/less fuel intensive.