[TransX] Calculating the Eject date

[blixel]

I'm able to get around the solar system quite well these days, but I'm always interested in improving my efficiency and understanding of things.

Video version of my question:

TransX Eject date question - YouTube

TransX Eject date question - YouTube

Text version of my question:

When you begin configuring your Eject plan in TransX, the Eject date it uses is right now. The problem is that right now expires in 1 second.

So, I need my Eject date to be in the future. The problem I have is that I don't know how far in the future it needs to be. There are 2 things that typically have to happen before I will reach the ejection point.

1. I need to wait until the earth rotates into proper position so that I can have an easterly take off heading.
2. I need to take off, get up to orbital velocity, and make sure my relative inclination is low.

I don't know how much time is going to be needed for those things to happen, so how can I set the Eject date to the proper MJD while sitting on Earth setting up my plan?

I do know that I can ignore the Eject date and use the TransX plan I came up with to take off and get into a parking orbit ... and then cancel the TransX plan I set up on Earth, and create a new one once I'm in orbit. Doing it that way ensures that my Eject date will be correct.

But I am wondering if there is a better answer than resetting TransX after take off? Resetting the TransX plan is especially inconvenient when you have 9 stages.

[Furet]

I'm not sure I understood your question well, but according to me you do not need to reset your TransX plan after take-off.

I think your questions are answered by Flytandem in the tutorial Earth to Mars part 1

TransX Tutorial - Earth to Mars (Part 1) - YouTube

TransX Tutorial - Earth to Mars (Part 1) - YouTube

and part 3

TransX Tutorial - Earth to Mars (Part 3) - YouTube

TransX Tutorial - Earth to Mars (Part 3) - YouTube

I'm doing this procedure to the letter and it works very well for me.

Happy orbiting.

[blixel]

Thanks for the reply. I actually know how to do that method already. That's what I was talking about in my original post with regards to establishing a parking orbit and then (as flytandem points out in video 3 at 1:40), you go through all the variables and "kill" them.

I'm just curious if there's a way to calculate the right Eject date MJD while you're still on the ground.

[Furet]

I'm using

Trajectory Planner

Trajectory Planner

and

Trajectory Optimization Tool v2.1

Trajectory Optimization Tool v2.1

to determine a departure date. Once I know the MJD, I set the scenario date about 1 day before ejection, and I'm planning all the trip with TransX. Then I'm looking for the take-off hour with Flytandem's method.

Once I'm in transfert orbit, I'm just adjusting the ejection parameters according to Flytandem's tutorial: I'm looking for the deltaV for the ejection burn, and I'm setting the prograde velocity accordingly on the manoeuvre view.

Then the variables of the 2nd stage can be resetted, but if the transfer orbit has the correct inclination and LAN, the whole TransX plan remains unchanged (no need to plan again all the stages).

Hope this helps.

PS: Just feel free to correct me if I'm doing wrong. I'm just feeling far from an expert.