TransferMFD I thought I had figured out the Transfer MFD thing!

[galwacco]

Hi there people.

First of all, did this forum change or something? I am pretty sure I already had an account at orbiter´s official forum, but even the inteface of this one is different from the one I remember!fftopic:sorry! hehe.

Well, going to my point. After 2 years of trying to get acquainted to orbiter and things I thought that today I had finally gotten the point of hollman transfers. So, I started out my delta glider at Cape Canaveral (that scenario that comes together with Delta Glider IV to launch to ISS).

I changed the map view as to intercept a launch window to the moon, so I had to use time warp to fast forward almost a day in advance in order to get to my desired launch window.

So, launch window approached, relative inclination pretty close to zero, take-off.

as soon as I reached LEO, I performed a correction for my RInc wasn't all that pretty. After RInc correction, turned prograde and started to tune my transfer MDF.

I followed everything according to the rule. My delta V got somewhere around 3.100, fixed my Ejection point, everything correct.

Time to burn was fine, burned as correct as possible, quit my burn when DV was down to zero.

But when I finished the entire process, I figured out that the moon was opposited to me. I was going somewhere else other than the moon!

I got sooo frustrated! because it was the first time in two years I was sure the transfer MDF was correctly tuned and that I followed everything as I should.

What went wrong!??? Wasn't I supposed to get that scenario and fast-forward for the launching window? do I have to only use that scenario that comes in the tutorial? what if I do not want to use the older delta glider? what if I want to go to the moon somewhere closer to today's date?

If it was fine, what was wrong? the transfer MDF told me the burn ejection time, the map told me the launch window, I only took off when both lines at the map where together and my RInc was close to zero.

Another question. How come every single time I try to perform a transfer, when the delta glider is on its way to the moon and I timewarp, it spins??

It does not fligh pointing straight ahead as in the tutorial? what is wrong? I always use prograde until the burn ejection time, but when it's ejection time, I turn off prograde, so I figure it should be pointing straight ahead and not spin around.

Sorry for all those questions. I confess that I am a little frustrated, it's been two years that I have been trying to to that but no success! I can use flight simulator to fly from airport to airport using the VORs, ILSs, waypoints and sheets, but I cannot figure this thing out.

With two kids and a job to cope with, it probably gets hard to focus on the white papers to learn it correctly, but I am trying as hard as I can. If you guys give me a hand on this one, I will appreciante it a lot!

Thanks a lot!

 

[unknown_orbiter]

Ok well here are a few things to note:
Your launch from KSC should be a degree from ideal RINC, because by the time you are up in the air and doing your orbital injection time will move forward (this is not necessary but it makes your calculations a weeee bit more precise, at least it does for me).
Next, don't use the tutorial for this that comes with the program. I dislike it and it screwed me over many a time. Download the "Go Play in Space" orbiter manual and it will give you PRECISE instructions for KSC-Brighton Beach. A common mistake people make with the Transfer MFD is mixing up those pretty colored lines. Green, gray, dotted, filled.... it gets confusing.
Finally, during your flight into a LEO (while still under the blue sky) you must be constantly yawing in order to keep your RINC as close to zero as possible. This way you will have MUCH more fuel after you cancel it out in LEO.
To answer a few more of your questions:
You can fly to the moon in most any craft. In fact I took that scenario (the tutorial KSC-moon scenario) and edited it with notepad to change the Delta Glider to a Delta Glider IV. Much easier craft to use and much more fun!
And you can take off for the moon any time. It is just a matter of fuel. Canceling out a high RINC takes a lot of it. So if you take off from KSC at night while the moon's RINC is as close as possible to zero, then cancel RINC out a bit more during your ascension, then you will have to use very little fuel to completely cancel it out in LEO.
Now for your spastic ship problem during time warp. I am almost completely sure that you are time warping with prograde still activated . Once you are on your way to the moon take off of the autopilot and warp away. I suggest doing the really fast warps only after a sufficient distance from earth (gravity's influence is less than 60). This is pointed out in the Go Play in Space manual, so read there for a reason ( I forget ).
Sorry you had to go through all of that, and good luck! Any more issues and post or PM me.

 

[Quick_Nick]

About the spinning, do you have a joystick? It is possible that you have a small thrust from your RCS. More importantly, remember that you don't start your burn at the ejection date. (if you do, you'll be way off) The ejection date should be right in the middle of your burn. You have to figure out how long your burn will be, then subtract half of that from the ejection date, to find when to begin the burn.
You can use [ame="http://www.orbithangar.com/searchid.php?ID=3035"]this MFD[/ame], although you sometimes have to actually use your engines for a moment for the MFD to read your thrust correctly. (basically, if you start a scenario and don't use the engines, it will be wrong)

 

[galwacco]

Thanks for all the tips and sorry for taking so long to reply. I thought when somebody answered this topic I would automatically get a message at my mail box, which I didn´t, so I just checked directly at this forum today and found your answers there.

I figured out what was wrong, I messed up with the dotted colors, I am color-blind, so green and yellow are the same to me, I changed the colors of this MDF as an atempt to not mess up with that anymore.

My transfers still suck big time, but now I can get to the moon though I need to perfect it a loooooot more. Still gotta learn how to land at the right place at the right time too.

Thanks again for all the help. About the spining, it was because the prograde was on for too long, so I managed that too.

Thanks folks!!!

 

[TSPenguin]

to the forum galwacco.

You probably had an account at the old M6 forum. It was unstable and so Tex made this forum. The old forum only serves as an archive now.
Since this is an entire different forum software, in order to get an email if someone replies you need to subscribe to the thread. There you will have several options on email notfications.

You changed the colors on the TransferMFD? How?
There are a lot more colorblind orbinauts and it would be great if your method could help them as well.

Good that your spinning issue is resolved. But you will encounter some degree of spinning under high time acceleration. There is module on OH called absolute killrot which will fix that if you still have an issue with this.

Happy Orbiting

 

[TMac3000]

You almost always have a little bit of rotation, even at normal time, and even if you use KILLROT. It's because your controls are not perfectly precise (nobody's are). This little bit can translate to a lot at high time compression. I never go over 100x time compression; Orbiter gets buggy if you do. At 100x, Earth to Luna takes about 45 minutes real time. Quite tolerable. But if you hit KILLROT at 100x, you will almost eliminate the rotation. At the very least it will tolerable enough that you will only have to correct every few minutes.

 

[ar81]

See concepts on planetary transfers here
[ame="http://www.orbithangar.com/searchid.php?ID=3403"]Tutorial: Concepts for Interplanetary MFD 4.2.1[/ame]

 

[TachyonDriver]

I never go over 100x time compression; Orbiter gets buggy if you do.

I just ignore the spinning and watch my MFDs - I use max time compression on my trips to Mars....

When you've plotted your HTO in the transfer MFD, take a look at the TLi readings for you and the target. What you need to do is match those during the trip. Once you've completed the ejection burn, then either burn prograde or retrograde to keep the TLi values equal.

For interplanetary transfers you need to use patched-trajectory for the transfer MFD. Create an HTO (ref sun, source planet) to get you in the ballpark.
You first get out of the planet's gravity influence by burning prograde until your orbit goes hyperbolic, wait until the influence is less than say, 0.5 or 0.4 i.e it turns red on the MFD. Then switch ref to Sun, source to Self and then plot out a "proper" HTO.

Tach.

 

[Linguofreak]

You almost always have a little bit of rotation, even at normal time, and even if you use KILLROT. It's because your controls are not perfectly precise (nobody's are). This little bit can translate to a lot at high time compression. I never go over 100x time compression; Orbiter gets buggy if you do. At 100x, Earth to Luna takes about 45 minutes real time. Quite tolerable. But if you hit KILLROT at 100x, you will almost eliminate the rotation. At the very least it will tolerable enough that you will only have to correct every few minutes.

Orbiter doesn't really get "buggy," there's just stuff that you have to be careful about doing at high time warp. I generally use the killrot autopilot so as not to "cheat" on RCS fuel use, and then edit my rotation vectors in the scenario editor to get rid of the last little bit of rotation. Then I set RCS to "off" and set my joystick aside.

 

[Fizyk]

If you just turn off prograde, then you are already spinning, though very slowly, because the autopilot made you spin at such a speed that you follow the path. If, however, you killed rotation after turning prograde off, then the spinning was probably caused by gravity gradient torque.

Also, did you try to warp time and check, if you get to the Moon? Because in the beginning it may seem like you are going somewhere into the empty space, but during your flight the Moon will move, and you should meet it at your apogee.

 

[Tommy]

Absolute Killrot will eliminate all rotation completely:

[ame="http://www.orbithangar.com/searchid.php?ID=2899"]AbsoluteKillrot v.1.2[/ame]