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Old 11-23-2013, 09:26 PM   #1
Alexrey
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Default TransX Ejection Manoeuvre Errors

I've been trying to create a transfer from Earth to Mars using TransX but I keep running into the same problem. I've set up the required ejection date and burns etc. and aligned myself with Mars' orbital plane, but when actually trying to set the manoeuvre up with manoeuvre mode on, and adding the required delta-v for prograde and plane change burns the spacecraft isn't even able to get into hyperbolic ejection! I've looked at flytandem's tutorials, but I don't what I'm doing wrong.

Any help would be appreciated.

Here are some screenshots of what I mean:
Attached Thumbnails
transxprogradevelocity.jpg   transxplanechange.jpg   transxdate.jpg  
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Old 11-23-2013, 09:45 PM   #2
statickid
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Looks like your dumping a huge amount of DV into a plane change there. You're left display looks good to me at a glance.

Maybe don't worry so much about the plane if you're just starting out. Just get the ejection and timing right, adjust your orbital plane mid-course
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Old 11-23-2013, 09:48 PM   #3
blixel
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What I'm seeing in the 3 screenshots you provided is that you are inputting the velocity incorrectly. In Stage 1:1, View: Escape Plan, you take the total Delta V and input that as your prograde. That's it. What you're doing is you're going into Stage 2 and trying to copy each velocity element into your Maneuver. That may seem logical, but it's not what you want to do.

Look at this image:

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Old 11-23-2013, 09:52 PM   #4
statickid
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Remember if you are orbiting earth you CAN'T align your plane to Mars except at the nodes

---------- Post added at 01:52 PM ---------- Previous post was at 01:50 PM ----------

Yes it looks like two different plans, I'm actually confused by the right side display because I've never seen it have two separate target trajectories
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Old 11-23-2013, 10:40 PM   #5
blixel
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Perhaps a video reply will be easiest:

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Old 11-23-2013, 11:47 PM   #6
Alexrey
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Wow, thanks for taking the time to make that video blixel, very impressive. I'll download it when I'm at work on Monday (I'm currently using a heavily capped dongle at home while I wait for our internet to be installed), and I think I'll download the rest of your videos as well, brilliant!
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Old 11-24-2013, 10:58 AM   #7
Ripley
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Hi Blixel.

While watching your video I noticed some new wording of the various sensitivity levels, like Micro, Rough, etc., i.e. at 2:15, when you move the date around on the right MFD.

I presume I have the same "graphicsfix_enterbutton" TransX version as yours, but my sensitivity levels are not the same.
How's that?
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Old 11-24-2013, 03:40 PM   #8
Alexrey
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My next most pressing question is, say I start a scenario that is already in orbit about Earth and set up my ejection plan from there. How do I then align my spacecraft's orbit with the ejection orbit's plane? I tried setting my inclination to that of the ejection orbit but that did not work. I'm guessing I have to perform the plane change burns at the ascending and descending nodes of the ejection plane, and not my current orbit's nodes?
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Old 11-24-2013, 06:20 PM   #9
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Quote:
Originally Posted by Ripley View Post
 Hi Blixel.

While watching your video I noticed some new wording of the various sensitivity levels, like Micro, Rough, etc., i.e. at 2:15, when you move the date around on the right MFD.

I presume I have the same "graphicsfix_enterbutton" TransX version as yours, but my sensitivity levels are not the same.
How's that?
I'm using a custom version of TransX that dgatsoulis made. It adds the Rough adjustment (which is MORE than Course - very useful when you need to adjust the MJD forward by months/years), and it adds the Micro adjustment (which is LESS than Hyper - which is useful for fine tuning all maneuvers.)

There are other changes in his version as well. I believe he plans to make it available to everyone after we've had a chance to test it a bit more.

---------- Post added at 06:20 PM ---------- Previous post was at 04:04 PM ----------

Quote:
Originally Posted by Alexrey View Post
 My next most pressing question is, say I start a scenario that is already in orbit about Earth and set up my ejection plan from there. How do I then align my spacecraft's orbit with the ejection orbit's plane? I tried setting my inclination to that of the ejection orbit but that did not work. I'm guessing I have to perform the plane change burns at the ascending and descending nodes of the ejection plane, and not my current orbit's nodes?
I'm not completely sure I understand what you're asking. I think you might be asking how to set the Eject Orientation if you're already in orbit?

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Old 11-26-2013, 03:33 PM   #10
Ripley
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I don't mean to hijack the thread, but I think I have a similar problem, relative to TransX Eject Orientation anyway...

Say I am in an XR-2, going to Venus, took off at MJD 56014.9658741658 from KSC when RInc was nearly 0.01, I kept the RInc to a minimum while ascending, circularized my orbit and made an Eject Plan:



TransX on the left shows a lowest possible RInc of 7.727.

1st question: I've just passed the point on the line of Nodes. Is it the same if I burn on the other end of the line (inverting the direction of the burn of course? Norm/AntiNorm)?


2nd, more important question: if Align Plane MFD shows a 0 RInc, what is that 7.727?
I remember you once told me in a PM that Venus requires a "hefty chunk of plane change", but I just don't get why that RInc difference.




Thanks and

Last edited by Ripley; 11-26-2013 at 03:43 PM.
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Old 11-26-2013, 05:04 PM   #11
statickid
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from the transX manual:

"R.Inc. This is the difference in relative inclination between your planned escape orbit and your
focus orbit."
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Old 11-26-2013, 05:05 PM   #12
blixel
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Quote:
Originally Posted by Ripley View Post
 I don't mean to hijack the thread, but I think I have a similar problem, relative to TransX Eject Orientation anyway...

Say I am in an XR-2, going to Venus, took off at MJD 56014.9658741658 from KSC when RInc was nearly 0.01,
When taking off and getting into orbit, it's ideal to launch when you can fly as close to a 90 degree heading as possible. I brought up Orbiter and looked at the MJD you provided. At that particular time, you would have had to launch with a heading of either 173 degrees (almost straight south), or about 356 degrees (almost straight north). Either way, it's a lousy time to launch.

A better timing for the launch would have been about 56014.861145. At that time, you could fly at a heading of 67 degrees. (Getting a 90 degree heading from KSC isn't possible on this date.)



Quote:
Originally Posted by Ripley View Post
 1st question: I've just passed the point on the line of Nodes. Is it the same if I burn on the other end of the line (inverting the direction of the burn of course? Norm/AntiNorm)?
If the orbit is circular, then yes - it's the same either way. If the orbit is elliptical, then it will cost less dV to burn at whichever node is closest to Apoapsis.


Quote:
Originally Posted by Ripley View Post
 2nd, more important question: if Align Plane MFD shows a 0 RInc, what is that 7.727?
I don't believe Align plane MFD is of any use to you in the example you are showing. Venus orbits the sun, not Earth. So using Align plane MFD to determine your RInc wouldn't do any good until you escape Earth.

As far as TransX goes, the 7.27 is how far off you are from a 0.00 Eject Orientation. My guess is that when you were on the ground, you didn't fly to the heading that TransX gave you?


I don't have time to proofread. I'm on my way out the door.
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Old 11-26-2013, 05:57 PM   #13
Ripley
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Quote:
Originally Posted by blixel View Post
 When taking off and getting into orbit, it's ideal to launch when you can fly as close to a 90 degree heading as possible...
I forgot to say that I launched exactly in a 90 HDG.
I did that because Align plane MFD was telling me I had 0 RInc, but now i discover (how embarassing...) that align plane MFD...

Quote:
Originally Posted by blixel View Post
 I don't believe Align plane MFD is of any use to you in the example you are showing. Venus orbits the sun, not Earth...
Its REF wasn't on Sun.

Quote:
Originally Posted by blixel View Post
 If the orbit is circular, then yes - it's the same either way. If the orbit is elliptical, then it will cost less dV to burn at whichever node is closest to Apoapsis.
At least I (kind of) got this one.
http://orbiter-forum.com/showthread....3&postcount=41

Quote:
Originally Posted by blixel View Post
 As far as TransX goes, the 7.27 is how far off you are from a 0.00 Eject Orientation. My guess is that when you were on the ground, you didn't fly to the heading that TransX gave you?
Right!

Ok, thanks for your time.
I'll hide in my cave and dive into the books.
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