Tutorial Elaboration on trojan sling tutorials?

[atuhalpa]

Flytandem, I was wondering if it would be possible for you to do one more trojan sling tutorial verbally elaborating what is actually taking place as you click buttons and rotate trajectories. I am going over the one you did but in certain places such as "and now adjust inclination to rotate the white line til it is 90 degrees from where it was" I don't understand why you do that. I will admit that I am a bit slow on the uptake of certain concepts and and that it takes valuable time out of your day but in my humble opinion you are the foremost guru of the cult of transX, and a more explanatory tutorial would go a long way towards clarifying the concepts of inclination changing slings.

 

[flytandem]

Just noticed this post. Sorry for the delay.

I remember the slings off Jupiter that were intended to change the inclination to chase a trojan asteroid. Definitely a bit of a game coming up with the best velocity and the inclination and outward angles of the sling.

To answer the question about why we want to rotate the white line 90 degrees. First remember that that line is the axis of intercept between your plane and the plane of your target asteroid.

So let's get back to a simple situation of doing a plane change to match the orbit of a target. It could be you chasing the ISS for example. You could "seat of the pants" plane change by waiting until you are close but still a bit short of the node (where your orbit crosses the white line). You burn DN or AN whichever is pushing the white line (node) away from your position. The best you can do, in minimizing the resulting difference between your orbit and the plane of your target from that location, is to push the axis to 90 degrees from your current position. If you burn it past 90 you have passed the minimum. Then if you like you can repeat by waiting again until you are almost at the node and again burning AN or DN to push it to 90 from your current position. And even repeat several times for extra precision.

This concept of pushing the axis to a 90 degree position is all I'm doing in adjusting the slings to chase a trojan. You don't get to do repeated pushes to 90, just the one because you only have one sling at Jupiter. After that you will be doing any remaining plane changes using your fuel. This is why the whole thing is based on first doing the sling when Jupiter is crossing the node with the asteroid and then making the sling try to push the white line to 90 degrees.

I hope this helps. Doing those tutorials were very time consuming. Not so much for the flying but for the work in trying to figure out how to capture and minimize file sizes yet still have video quality. Everything I do now is on a small screened laptop and 3G connection from a remote area.

 

[atuhalpa]

I have followed the tutorial for the trojan sling and I can't get past the point where I am supposed to bring the node line back to the tangent point by adjusting the date (after the inclination adjust to swing it perpendicular) when I attempt to adjust the date the line only moves a very short disance and when it finally gets back to where it is supposed to be both orbits, jupiter and the trojan are completely eliptical and the date is really screwed up. I have followed the tutorial word for word and I don't understand where I am screwing up.

Any little tidbits of knowledge you pass along will be greatly appreciated, but I have realized that the only way I am going to learn the more esoteric aspects of transX is to just play with it and to accurately note what the results of my adjusting different parameters do to the flight trajectories of the vessels. I WILL become proficient in inclination changing slings or I'll go nuts trying!

 

[flytandem]

If the white line isn't moving very far then either not very much inclination angle is being applied, or you are applying the wrong direction of inclination angle. You could be making positive when the angle should be negative for example.

A way to think of it is, if you are before a node of Jupiter and trojan then the node (of you and the trojan after the sling) should be being pushed away. Make sure it's not being drawn closer. If you advance the date to past the node of Jupiter and trojan then it should push the node of you and trojan away meaning it will push it the opposite direction. So when passing the actual node of Jupiter and the trojan, that white line should be swinging back across your position. Almost like a couple of magnets that push away from one another. As you approach it from behind, it repels the node forward. as you pass it is then repels it rearward. As it swings back across your position, going from pushing forward to pushing rearward, then you are at the actual node of, in this case, Jupiter and the trojan.

 

[atuhalpa]

Okie dokie! I am wending my way through the learning process and can now set up a surrogate flight plan from Jupiter. Once I get my inclination, encounter velocity, and eject date for the Trojan node sling off of Jupiter, how do I go about setting up the flight plan from Earth? There is no rush to answer this post Flytandem as I am going through the trial and error process and trying to figure it out myself, but any pearls of wisdom would be greatly appreciated.

 

[flytandem]

Getting the ideal sling date and velocity at Jupiter is straightforward. Not necessarily easy but there is a specific answer.

The trip from Earth to Jupiter is however is more of an artform. You are starting with an ideal arrival date and arrival velocity that you want and so you start by just trying to arrive at Jupiter. Then you modify to get the date closer to your desired date. And mix in the arrival velocity. It's constant tweaking. Sometimes there is no perfect trajectory but it's a tradeoff of coming in on time and not the best speed, or coming in at a closer speed but not the exact date. Sometimes you can get both fairly close but you are missing Jupiter so a healthy mid course correction is the tradeoff. I often opted for the trade of correct date and do a burn at the Pe of the sling to get the velocity closer to what's wanted.

 

[atuhalpa]

Right, it is logical that arriving when Jupiter is at the node is more important than arriving with the right velocity delta vee wise. I will play around with the parameters til I get it right.