TransX Tutorial...yes ok,but when and how should I take off,burn???

[Lele81]

HI!
I read two TransX manuals, I think I understood how to plan a trip (to mars for now)....ok I have to set up two stages...set the prograde velocity, the window date...the hiperbolic orbit etc etc etc

But in pratice AFTER THAT what should I do???I have 2 questions:

1) When should I take off?
Tell me if I'm right: may I take off by myself and parking in a coplanar(with the target one) low earth orbit without watching at TransX? (quite earlier than the window date launch of course!!!)
(If not I think I understand I should watch in the first stage, equatorial view...and take off when the gray line intercept my position at ground...?)


2) Ok, suppose I'm in the coplanar LOW Earth orbit now, and I'm waiting to do my prograde burning: When and for how long?
Is the "when" the date that I read in the second TransX stage?
And what about the "how long"...the only thing I have is a number that I set up in stage 2, "prograde Vel." (suppose it is 2.000K....how I use this information for the "how long" must be my burning?

Thank you!!!

 

[TSPenguin]

Regarding Number 2:

You do your burn at the date you enter in the eject plan. TransX assumes the whole energy of the burn is set free at an instant. That point is the dashed yellow line.
To execute the burn so that the outcome matches TransXs assumption you need to start burning earlier. To calculate that, you can use BurnTimeCalc MFD. It also has an autoburn feature and is quite usefull in many other isntances.
Newer versions of TransX have BTC ability built in. The information is displayed in the lower left corner of the escape plan. It shows you positional information, how much Delta V you have to output and the correct time until you need to start burning. This is quite useful, although I prefer to use BTC MFD, no practical reason, I just like the thing

 

[agentgonzo]

For number 1, you need to launch when your current position lies at one of the intersection nodes of the target orbit - in other words, when the grey line marking the intersection of your current and target orbits lies straight through the major axis (ie, centre) of the green ellipse, like in the following image.

You can achieve this by either waiting, or by changing the ejection orientation.
This page explains it better

 

[ar81]

HI!
I read two TransX manuals, I think I understood how to plan a trip (to mars for now)....ok I have to set up two stages...set the prograde velocity, the window date...the hiperbolic orbit etc etc etc

But in pratice AFTER THAT what should I do???I have 2 questions:

1) When should I take off?
Tell me if I'm right: may I take off by myself and parking in a coplanar(with the target one) low earth orbit without watching at TransX? (quite earlier than the window date launch of course!!!)
(If not I think I understand I should watch in the first stage, equatorial view...and take off when the gray line intercept my position at ground...?)


2) Ok, suppose I'm in the coplanar LOW Earth orbit now, and I'm waiting to do my prograde burning: When and for how long?
Is the "when" the date that I read in the second TransX stage?
And what about the "how long"...the only thing I have is a number that I set up in stage 2, "prograde Vel." (suppose it is 2.000K....how I use this information for the "how long" must be my burning?

Thank you!!!

It seems you understand TransX, but not the concepts behind interplanetary flight. You may like this: [ame="http://www.orbithangar.com/searchid.php?ID=3403"]Tutorial: Concepts for Interplanetary MFD 4.2.1[/ame]

 

[Lele81]

Hi, I'm reading for now the tutorial that suggested Agentgonzo, it seems useful because it's a bit more "pratical" then the other tutorials I read....those are cool, but with this one, maybe I'll reach to understand it better....I'll let you know if I have other problems))) (and of course I'll have ahahaha:speakcool

 

[Tex]

Why don't you try flytandem's transx video tutorials? They were a great help for me and helped me finally master transx:

http://www.orbiter-forum.com/tutorials.php

Transx is now my new favorite MFD.

 

[Lele81]

Thank you! I'll try surely those too!!!!!!!!!!!

P.S. before I try those tutorials, can anyone solve a doubt that I have?

I'm doing an Earth Moon trip, following a tutorial, I have a question about the MID COURSE CORRECTION:

The tutorial tells to start thinking for a correction when TransX deletes the first STAGE of the planning trip (because of the distance from Earth)

Ok, then it tells to use Manoeuvre in the same way I used the TransX before to plan my ejection orbit. Ok, that's right, my doubt is: in the exact moment in which TransX deletes the first Stage, in the remaining stage, it comes a changing: the dashed yellow line of MINE predicted future position slides immediately from the position in which it was (aliged to the other yellow line and the grey one) and it alignes with the blue line of my actual position.

I don't know if it's a bug or wath, but when I do the correction....do I have to re-correct also the yellow line and bring that back in the right position of alignment? But doing that the distance from the planet increases so much...

Thankz, now I'll download the other tutorials!!!!!

 

[Tex]

I am no transx expert by any means as I finally learned it myself just recently thanks to flytandem's video tutorials. I would suggest you just watch those, specifically his earth to moon and earth to mars tutorials. Learn it right the first time and things will be a lot easier on you.

Anyway, yes you should be using manouver mode when you do a midcourse correction burn. The object is to adjust all of the manouver values until you get Inc as low as possible and get your closest approach set where you want it. Change the view to your burn view and point the ship so the green X is in the center. Burn until Dv is 0.


Note: For midcourse correction burns the time remaining till the burn will be shown as negative. Nevermind this. Proceed with the burn after you've made the necessary adjustments to the manouver values.

 

[Lele81]

Thank you tex!
Thanks to that tutorials I managed to do a trip Earth-Moon-Earth finally!!! It's my first one....now, I was trying to do the Earth-mars tutorial....but I have a doubt (maybe the last one) about the Burning Dates:

Ok TransX does it all by himself and it tells you WHEN to burn but, in the tutorial, flytandem, almost always, sets an EJECT DATE (in the second stage "eject plan") that is a bit in the past....and also, when he returns to the first stage to set the ESCAPE PLANE, he goes forward in the time, to find a good heading (90 degrees) for the departure....with ANY CARE ABOUT THE EJECT DATE IN THE EJECT PLANE THAT IS VERY BEHIND IN TIME RESPECT TO THE ACTUAL DATE (rising)!!!!

But TransX gives a positive "time to burn"...how is it possible? how can things work out IF the EJECT DATE is in the past???? (and it works, because he manage to go to Mars but...if I don't understand WHY, I can't understand how things work....

Thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Lele81]

I solved all my doubts with the tutorial
The date problem was that...well, it's not very important if you depart some orbits before or after, thank you!!!