Video Tutorial: DG4 to ISS

[Enjo]

I didn't have time to watch the whole tutorial, but if you zoomed the map just a bit more, you'd notice that you had actually passed the launch window The key is to launch a bit before the orbital plane passes our launch site.
Also, what helps users are animations. A good effect would be achieved if you accelerated time and shown that the orbit does move.

When I have something more, I'll post.

 

[Tex]

Cheers Enjo!

you'd notice that you had actually passed the launch window

Yea, that was actually how it looked by the time I loaded that scenario and got to filming. Its the stock scenario which came with the DG4. I wanted to use something everyone had, however the time in that scenario should really be backed up for the best launch time.

Also, nice idea about accelerating time to show the movement of the orbital plane.

 

[blixel]

I agree with kevinvr who said, "I agree with Oceanic, wish I had seen it a few moths ago, but then again I did learn a lot by making my own mistakes." Like kevinvr, I feel like I learned a lot by making my own mistakes. So maybe it's a good thing that I didn't watch this video until now.

But I just wanted to say what many others in this forum have said before me. But it's worth repeating. Great job on this tutorial. I say that with absolute sincerity! I've done a bit of work with video, so I can appreciate how much effort goes into this kind of thing.

The audio quality of this video is outstanding. It sounds like you were definitely using a mic and were mindful enough to eliminate any background noise. (No TV's blaring, no dogs barking, no kids screaming, etc...) The audio is nice and clear.

The video quality is very good. I understand how much disk space and "bandwidth" video takes at high resolutions, so I understand why this was kept at 640x480. (Plus it was recorded a couple of years ago ... which I believe was before youtube even offered HD.)

The production quality was top notch! The way you broke the video up into logical segments and added additional images to help clarify your points ... that kind of thing is incredibly useful. You definitely have some production skills. (I've seen some other videos on your youtube channel ... great stuff.)

Something that I think is worth mentioning ... I don't think there is anything about your instructions that requires the DG IV is there? (Other than the autopilot take off.) The reason I mention that is because I had actually avoided your video up to this point because I assumed you were using some technique that could only be done in the DG IV. And since I don't use the DG IV (and don't want to use it [yet]), I figured I couldn't learn anything from your video.

But I decided to watch it anyway today ... and the main thing I noticed was that everything you did (other than the autopilot take off) can be done in the regular Delta-glider. Right?

As a relative newbie to Orbiter, I don't want to clutter my system with additional spacecrafts and MFD add-ons. I want to learn the standard MFD's first and stick to the standard spacecrafts.

I read in another forum post how there are a lot of add-ons that can make Orbiter completely unstable. Whatever the guy was talking about, the people who responded suggested that he disable all his MFD add-ons and try again.

So ... I don't know what's safe and what isn't, so I'm just sticking to the defaults. It seems to me the defaults will always get the most attention from the developers, so I'd rather learn that stuff than learn about some add-on that may become obsolete with the next release because the developer of such and such add-on isn't actively involved with Orbiter any more. Know what I mean?

9:20 (Synchronize orbit)

This section was really useful to me. I had already read (somewhere) about docking with the ISS on the sunlit side of the planet. But the information I read didn't explain *how* to make sure you will dock with the ISS on the sunlit side of the planet.

So up to this point, I have been using my existing apoapsis and periapsis points as the reference points for determinging which side to dock on. By existing points, I mean - whatever my apoapsis and periapsis happened to be at the point after I achieved orbit and stabilized my perigee.

For example, if my periapsis happened to be on the dark side of the planet, then I would choose the apoapsis as my rendezvous point. And if the apoapsis happened to be on the dark side, then I would use the periapsis as my rendezvous point.

I never put any thought into making my apoapsis be the rendezvous point right after sunrise. That was an excellent tip that I picked up from watching your video! (Learn something new every day.)

The problem with my method (of relying on wherever my apogee/perigee just happened to be) was if I needed to make a large burn to bring DTmin down to zero, I could potentially lower my periapsis down so far that it would be in the earth's atmosphere. (Like you mention in the video at around 17:55)

To work around that problem, I would fast forward time for as many revolutions as was necessary to bring my Delta-glider closer to the ISS so that my DTmin adjustment would be minimal.

That, of course, is very sloppy and time consuming.

I also found that when I would make my burn to bring DTmin down to zero, my apoapsis and periapsis would often "flip" on me. For example, if I was burning at perigee to bring apogee down a little so that DTmin would be closer to zero, it would often be the case that my burn would last so long that my apogee would end up lower than my current perigee ... so they would "flip."

That wasn't too much of a problem really ... (other than being confusing) ... but I would then have to change the Sync Orbit MFD from Sh-apoapsis to Sh-periapsis.

The whole thing just felt very sloppy and imprecise. I have (only recently) been able to catch up and dock with the ISS/Mir/another vessel ... but the procedure has felt dirty. Your video has given me a great bit of insight. I can't wait to get into Orbiter and try this out.

One thing I found interesting about your video was at about 17:05, you mention that you don't know if you're going to need the main engines or the retro engines. I have had that problem too but just assumed it was my own lack of knowledge. Surely there is a scientific way to know which way to burn to bring DTmin down to 0? Surely it isn't just trial and error?

Finally, what is all that extra stuff at the end of your tutorial?? It looks like you have a person remove an object from the ship and transfer it to the ISS? Can you really do that with Orbiter?? I've never seen any options for taking a space walk. If Orbiter can do that ... OMG ... how freaking awesome is this program???

I'm discovering new things I can do all the time. Like the Shuttle-A ... I just learned that it has some kind of payload thing. I don't know how to use it yet, but it sounds like a really fun simulation to take a payload to the moon and drop it off.

---------- Post added at 11:57 PM ---------- Previous post was at 07:42 PM ----------

I didn't have time to watch the whole tutorial, but if you zoomed the map just a bit more, you'd notice that you had actually passed the launch window The key is to launch a bit before the orbital plane passes our launch site.

Hmm... I didn't know this. I thought the launch window was when the target object (the ISS, Mir, whatever), was along the same longitudinal line as the launch site? So ... launching from Cape Canaveral, I thought you were supposed to launch when the ISS was along the 80 degree West longitudinal line. Basically as close to "over head" as possible.

But if I'm understanding what you said here, you are saying you want to launch when the orbital plane line is crossing over the launch site.

Is there a way to calculate this more scientifically. Using terms like "a bit before" doesn't seem very accurate. What is "a bit" exactly? A dozen pixels on the Map MFD? A centimeter on the Map MFD?

With the precision that all the other MFD's offer, I'm thinking there must be a more precise way of figuring out when to launch to rendezvous with an orbiting target like the ISS. (Please don't say TransX. Fingers crossed.)

 

[Tex]

Hi blixel, thanks very much for your comments. I'm always happy to hear my tutorial helped someone. Allow me to answer your questions below. :tiphat:

The audio quality of this video is outstanding. It sounds like you were definitely using a mic and were mindful enough to eliminate any background noise. (No TV's blaring, no dogs barking, no kids screaming, etc...) The audio is nice and clear.

I use a very professional mic which is run through a mixer and then the sound card. Learned after many failures the computer mics just don't cut it. :thumbup:

... and the main thing I noticed was that everything you did (other than the autopilot take off) can be done in the regular Delta-glider. Right?

Indeed you can use the same techniques in any vessel. I just listed the DGIV as required for the launch autopilot, as you mentioned, and the fact that it came with the exact scenario I wanted the viewer to use so that they were starting with the exact same parameters as I did in the video.

I've been considering remaking the tutorial, so perhaps I will use the default Delta Glider for the remake. I will at least be more clear about the fact you can use the same techniques on other vessels. You make a good point looking at it from a beginners perspective which I just overlooked.

As a relative newbie to Orbiter, I don't want to clutter my system with additional spacecrafts and MFD add-ons. I want to learn the standard MFD's first and stick to the standard spacecrafts.

Nothing wrong with that. For the large and complex addons (ie: Shuttle Fleet, AMSO, NASSP) it is best to have a totally separate install for them, which their documents will detail. I have a general play install that has the essential addons such as sound, DGIV, UCGO, XR2, XR5 all installed. You can easily run all of those with no problems, as well as MFDs like TransX, Aerobrake, IMFD, BaseSync, LaunchMFD. I usually have all of those activated during my sessions.

One thing I found interesting about your video was at about 17:05, you mention that you don't know if you're going to need the main engines or the retro engines. I have had that problem too but just assumed it was my own lack of knowledge. Surely there is a scientific way to know which way to burn to bring DTmin down to 0? Surely it isn't just trial and error?

Sure there is a way, I just forgot which direction during all the other things I was rambling on about in the video. If ISS is closer in front of us, then we are going to burn retrograde at the rendezvous point because we need to catch ISS. If it was closer behind us, then we would burn prograde at the rendezvous point because we would need to slow down, or take a longer time to orbit the earth each orbit, which in turn allows ISS to catch up to us. Clearly in the tutorial ISS is just in front, so I knew the burn was going to be retrograde, I just forgot while filming it. I suppose in the end it gives the viewer an idea of what sort of trial and error will work though.

Taking many orbits to catch ISS or letting it catch you is not sloppy. That is realistic and being conservative with your fuel. The further ISS is away from you, the more you will have to burn to rendezvous in only a few orbits. If your goal is to get there in a very short time, then burn prograde until DTmin is on 0, with only a single orbit to rendezvous. Otherwise, if you burn retrograde, you are limited by a collision with the atmosphere as you discovered.

Finally, what is all that extra stuff at the end of your tutorial?? It looks like you have a person remove an object from the ship and transfer it to the ISS? Can you really do that with Orbiter?? I've never seen any options for taking a space walk. If Orbiter can do that ... OMG ... how freaking awesome is this program???

That is all part of the DGIV addon. You can add payloads and do space walks from the DGIV. You can see a list of recommended addons here, the DGIV is linked on that page. Its a good starting point, but as you get better I recommend the XR vessels. They're a lot more complex to fly, a pilots vehicle if you will.

Hmm... I didn't know this. I thought the launch window was when the target object (the ISS, Mir, whatever), was along the same longitudinal line as the launch site?

You actually have to allow yourself enough time to reach orbital velocity, which takes up to 8 minutes or so, depending on the vessel you're flying. That is why you take-off just before the orbital plane crosses your position. I explain this better in my newer tutorial, PART I here.

 

[blixel]

Hi blixel, thanks very much for your comments. I'm always happy to hear my tutorial helped someone.

It was extremely helpful. And again, the production was A+. I wish I had the resources to do videos. I really like explaining things that interest me, such as Orbiter.

I've been considering remaking the tutorial, so perhaps I will use the default Delta Glider for the remake. I will at least be more clear about the fact you can use the same techniques on other vessels. You make a good point looking at it from a beginners perspective which I just overlooked.

No need to "throw out" the current video. For me personally, I like hearing/seeing the same thing explained multiple times in a variety of ways. When someone explains something, there is often some disconnect between their thinking and mine. But when I see/hear the same thing explained 2 or 3 different ways (even if its by the same person), I can usually bridge the disconnect by grasping different bits of information from each explanation.

For example, the default Orbiter install has a great tutorial called "DG to the moon" ... it was definitely extremely useful. But I really wish there had been at least 2 "DG to the moon" tutorials. No two trips to the moon (in my experience) go exactly the same way. So when I was learning to do it on my own, I ran into a couple of roadblocks (so to speak) whenever my situation was different than what happened in the tutorial. A second tutorial probably would have been different enough to help clear up some of those things.

Sure there is a way, I just forgot which direction during all the other things I was rambling on about in the video. If ISS is closer in front of us, then we are going to burn retrograde at the rendezvous point because we need to catch ISS. If it was closer behind us, then we would burn prograde at the rendezvous point because we would need to slow down, or take a longer time to orbit the earth each orbit, which in turn allows ISS to catch up to us.

Ah, of course. Yes, that makes perfect sense ... and I actually already understood that. But I guess I thought the "rules" might be different when using the Sync Orbit MFD.

Actually, it just occurred to me that you don't absolutely need the Sync Orbit MFD. You could just use the Map MFD to establish your rendezvous point ... say Apogee at sunrise ... and then simply orbit the earth as many times as was required to close the gap. It would happen *eventually* as long as your perigee was, say, 200km.

Hmm... I'll have to try that. That might be worth pointing out to newbies. Forget about the Sync Orbit MFD for your first couple of times rendezvousing with the ISS. Just learn how to establish the apoapsis at sunrise, and then learn how to eliminate the relative velocity once you catch up to the ISS. (And subsequently dock.)

Then, to improve your efficiency, add in the relative complexity of learning the Sync Orbit MFD.

Now that I put that into words, I wish I had known that myself a few weeks ago. I couldn't figure out how to catch up to the ISS to save my life. The Sync Orbit MFD was a source of major confusion and aggravation. It would have been nice to know it wasn't even needed.

Taking many orbits to catch ISS or letting it catch you is not sloppy. That is realistic and being conservative with your fuel.

That makes sense. What I really meant by "sloppy" was that the way I was going about it (due to lack of understanding) made everything awkward. A burn at apogee to adjust DTmin would end up causing my apogee to move its position.

I now realize that was because I was trying to do too much at once. I now realize that catching up to the ISS may require lots of little burns combined with lots of orbits.

I was thinking in terms of the way I got to the moon. At each step, you basically just do 1 thing. Burn to align the plane, then do a big ejection burn.

I didn't comprehend that the "mechanics" were very different when trying to catch up to the ISS. If the ISS is on the other side of the planet, for example (which it has been for me several times due to my not knowing when to launch), then it's probably impossible (or at least very impractical) to get everything done in a single cycle.

In the event of the ISS being really far away, it seems to me like the right course of action is to close that gap down to a relatively small distance before even bothering with the Sync Orbit MFD. Otherwise, the burns you need to make are so huge that it totally messes up your rendezvous point.

For example, if your rendezvous point is apogee, and you make a huge burn to bring up your perigee (in an effort to reduce DTmin to 0) ... you end up "flipping" your perigee and apogee ... which is confusing as hell. And when you don't know what's going on, you just think it's not working. The fact is, it is working, it's just that your course of action leaves a lot to be desired. (Speaking from personal experience here.)

You actually have to allow yourself enough time to reach orbital velocity, which takes up to 8 minutes or so, depending on the vessel you're flying. That is why you take-off just before the orbital plane crosses your position. I explain this better in my newer tutorial, PART I here.

I'll check out the new information you just linked to. But briefly, based on what you just said, I'm still a little confused. When you say take of before the orbital plane crosses your position ... do you mean the ISS itself? As in ... when the ISS itself (as indicated on the Map MFD) is passing by? Or do you mean the actual orbital line on the Map MFD. That long line that represents the ISS's orbital plane.

The reason I ask is because when I tried taking off when the line on the Map MFD for the ISS's orbital plane crossed Cape Canaveral, the ISS itself was almost on the other side of the planet. So when I got into orbit, I was well aligned with the plane (thanks to careful corrections while riding to orbit), but once I got there, the ISS was so far away that I had to go around ... for what seemed like several dozen orbits.

Perhaps that is the "right" way as in more fuel efficient? Off the top of my head, it just seems to me like it would be more efficient to be closer to the ISS after launch.

Maybe my expectations are all wrong. When you are going to the moon, you can take off, do everything you need to do, and then eject to the moon pretty much without even completing a single full orbit. I guess it seems unintuitive to me that you can go to the moon in a single orbit, and yet you can't rendezvous with the ISS without going around the earth dozens of times.

 

[tblaxland]

Perhaps that is the "right" way as in more fuel efficient? Off the top of my head, it just seems to me like it would be more efficient to be closer to the ISS after launch.

Changing the orientation of your orbital plane is much more expensive (in terms of fuel) than waiting for the ISS to catch up (which in comparative terms uses basically no fuel). The important thing for a fuel efficient intercept is to be "close" to the ISS in terms of velocity - this means both your speed and direction need to be similar - getting close in terms of distance is just a matter of waiting. It is counter-intuitive, but that is the way the physics work.

Maybe my expectations are all wrong. When you are going to the moon, you can take off, do everything you need to do, and then eject to the moon pretty much without even completing a single full orbit. I guess it seems unintuitive to me that you can go to the moon in a single orbit, and yet you can't rendezvous with the ISS without going around the earth dozens of times.

The Moon is travelling much slower than the ISS. So much so that it is not really important to be in the same plane as the target anymore - by the time you get to apoapsis your velocity has dropped so much that a plane change doesn't take so much energy. Combine that with the fact that the Moon's gravity will do most of the plane change for you. Gravity is something the ISS has very little of

 

[blixel]

Changing the orientation of your orbital plane is much more expensive (in terms of fuel) than waiting for the ISS to catch up (which in comparative terms uses basically no fuel). The important thing for a fuel efficient intercept is to be "close" to the ISS in terms of velocity - this means both your speed and direction need to be similar - getting close in terms of distance is just a matter of waiting. It is counter-intuitive, but that is the way the physics work.

Thanks a lot for this reply. The more I think about it, the more I understand what you are saying. I remember just yesterday, I took off, docked with the ISS ... and then, for the fun of it, and to test my "skill" ... I decided to try and leave the ISS and go straight to Mir.

I noticed when doing the plane change that I almost ran out of fuel! I remember the difference in planes was over 70 degrees. (I don't recall the exact number, I just remember it was 70-something.)

I thought I was going to have to abort the attempt ... but the Delta-glider did in fact have enough fuel for me to also make it to Mir in one launch. But there certainly wasn't a lot of fuel left when I got to Mir. I coasted in on fumes. haha

It's a good thing I don't know how to land yet, because I wouldn't have had enough fuel left to de-orbit.

I do have a basic understanding of the concept of why it's so important to minimize fuel usage. As I understand it, fuel = mass. (On Earth, mass has "weight", but in orbit, the term weight doesn't mean anything, so it's referred to as mass.)

To get a pile of mass moving, it requires "energy" ... as I understand it, the problem we face with getting mass into orbit is that we basically have the law of diminishing returns because our current engine technology basically sucks. So we get to a point where it is physically impossible to lift an object of certain "weight" into orbit because the additional fuel that would be required to lift that additional "weight" is so heavy that the engines can't generate enough energy to get it off the ground.

So ... for example, if you just wanted to take something as small as a marble to Mars, and you wanted to do it in a reasonable amount of time (e.g. burn lots of fuel to expedite the trip) ... it wouldn't be possible because the fuel requirement would be so high you'd never get the marble off the ground for the fact that fuel you needed to make the expedited trip weighed more than the engines could lift off the ground.

The Moon is travelling much slower than the ISS. So much so that it is not really important to be in the same plane as the target anymore

Really ... I didn't know that. That is interesting. I'll have to try an extremely off-plane trip to the moon just to see if I can pull it off.

- by the time you get to apoapsis your velocity has dropped so much that a plane change doesn't take so much energy.

I have noticed that! I mention that very point in this "slideshow" kind of thing I did, here:

http://www.facebook.com/photo.php?fbid=1676409603540&set=a.1676408803520.86496.1636496947

It's so weird how you get up to over 10,000 meters per second to eject from the earth to the moon, and yet when you are just barely away from the earth (by only a matter of a couple hours), you've already lost a tremendous amount of velocity.

When you watch the velocity drop off so rapidly there at the beginning, it seems like you can't possibly make it.

 

[tblaxland]

Really ... I didn't know that. That is interesting. I'll have to try an extremely off-plane trip to the moon just to see if I can pull it off.

Tip: You can do it without too much fuel cost provided you eject at about the right time. The "right time" is approximately 4 days (your travel time from Earth) before the Moon passes through the intersection of your orbital plane and its own orbital plane. Orbital mechanics is just like doing a tango - you'll land flat on your face if you get timing wrong

 

[Tex]

In the event of the ISS being really far away, it seems to me like the right course of action is to close that gap down to a relatively small distance before even bothering with the Sync Orbit MFD.

As tblaxland mentioned above, it's a lot more costly to change your orbital plane than to sync your orbit with a target. For this reason, sometimes ISS may be right over your launch site when it's time to take-off and other times it may be on the other side of the planet.

Once you finish your launch and your orbital plane is aligned with ISS, you can pull up the SyncMFD and press the 'LEN' button to add more orbits to intercept. This allows you to do a smaller sync burn by using more orbits to meet ISS.

When you say take of before the orbital plane crosses your position ... do you mean the ISS itself? As in ... when the ISS itself (as indicated on the Map MFD) is passing by? Or do you mean the actual orbital line on the Map MFD. That long line that represents the ISS's orbital plane.

I mean the orbital line, which after you select ISS as a target on the MapMFD you can see. In Orbiter 2010 with the new MapMFD, you have to change it from ground track to orbital plane in order to see your targets current plane while sitting on the ground. In the first part of my newer video tutorial, I explain exactly how to determine when to launch. While it is for going to the Moon, the same principle applies to ISS when you want to optimize your plane alignment during the launch.

 

[wilddoktor]

I know this is a 7 month old thread, but I just starting using Orbiter a couple weeks ago, and was very thankful to find this tutorial. (As others have said, awesome job! Great quality, great information, and...nose cone... )

I hope it's ok to ask a question specific to this tutorial...if not, I'll gladly start a new thread.

Following along with the video, I've gotten (a few times now) thru roughly 15:10, gotten my APA to exactly match ISS's alt @ our rendevous point, RInc to 0.00, and TthA/TthD to 0.05. But each time, when I get the Sync Orbit MFD setup, my DTmin is about twice that in the video.

You probably know where this is going.

If I continue thru the tutorial and make the loooong burn to get DTmin down to 0, my PeA drops to roughly 157k, and my ApA drops a few hundred meters.

After that, things just get worse, and I eventually completely miss getting docked to ISS.

I'm not even sure what to ask at this point; but any help / pointers would be appreciated.

Thanks!

 

[Tex]

If you have 'Non-spherical gravity sources' enabled, then try turning it off because it will cause your orbital parameters to change more. I filmed this tutorial with that option off and recommend beginners learn the concepts first before playing with that option activated.

 

[wilddoktor]

Thanks Tex; It isn't enabled right now, but it might have been when I tried the launches (maybe I messed with it while playing with some of the other demo scenarios). In any case, I'll try again hopefully tonight.

Would the non-spherical gravity cause the DTmin to be larger, or cause the PeA to drop that much? (or both...)

Or maybe a better question is, what exactly is DTmin and why is it so large?

Thanks!

 

[Merv0728]

Tutorial

I have just tried to download this tutorial but get a notice saying the site
megaupload,com has been seized by the U.S. authorities.
Where else can I Download the tutorial ?
Thanks anyone

 

[astrosammy]

Vimeo has a download function. But you need to register.

 

[Ripley]

...Where else can I Download the tutorial ?...

If you don't mind reading some italian subs, you can grab it from my Dropbox.

Link deleted


Edit: Video removed from Dropbox, now only on Vimeo
https://vimeo.com/15865317

[ame="http://vimeo.com/15865317"]Tex's DG4 To ISS - Italian subs on Vimeo[/ame]

 

[Tex]

I'll also upload it to our server and update the download link.

I've been working on a new version for Orbiter 2010 forever now, but just haven't gotten around to finishing it. I haven't really played Orbiter for close to 6 months now.

 

[sitha241]

Success!!

I tried tutorial on orbiter 2010 beta..and done it from first attempt!! tnx tex

 

[C3PO]

If you decide to update this tutorial I suggest you mention the nonspherical gravity at the start.

A RInc of 3-4° is fine for a beginner that's doing a rendezvous for the first time. Reducing RInc during the ascent is for more experienced users. (Since this is using a default scenario, you could post the take-off time that leaves the lowest RInc)

The only thing I'd change in this video are two minor details in the sync bit, but it just how I prefer to do it.. You can always catch up to your target, even if it's right behind you at the end of the ascent. If you go high to let ISS catch up to you, the MFDs are going to look different. The fuel isn't an issue in the DGIV, but it is more efficient to stay below ISS. Just wizz around in the initial orbit until you're 1/4 orbit behind ISS, ant then set up your rendezvous point. That works every time, and simple is good when you're a beginner.

The other thing is the 'LEN' button on the SyncMFD. It can show up to 19 orbits ahead, so it's easier to see when you're going to be closest to the ISS. If you choose the next orbit, you don't risk lowering the PeA into drag, and as a bonus your relative speed will be lower at the rendezvous point. So always thrust prograde to sync the orbits. Simple, and it works every time. (You could mention that DTmin is the difference between the two yellow numbers in the columns)

This is probably the best tutorial I've seen in many years, simple and easy to follow. Excellent work!!!