IMFD tutorial results in uncompleteble flight, need tips why

[Hmuda]

So the situation is this:

I use the DGIV and the IMFD for Dummies tutorial (at least that explains WHY I'm doing stuff and not just what I'm supposed to be doing, so thanks a lot José, you sure made my life easier ).

But there seems to be a problem in the Slingshot tutorial. I follow every single instruction to the letter, but when I get to the actual slingshot, the proposed PeA in the slingshot MFD is waaaaay below the Moon's surface. Something like 1.4xxM meters.

I can adjust this by altering the arrival date to the target object (in this case, the ISS), but I was wondering if I did something wrong, forgot something, or the arrival date was wrong in the tutorial in first place?

And since I'm here, just a couple more questions:

- is there any good reason why I should use the latest IMFD? 4.2.1 works flawlessly, but I noticed control lockups when using 5.3. I can eject just fine, but somewhere along the way, auto-burn won't do squat any more and all my ship-controlls become unresponsive (AB just sits there, trying to turn but since the controls are gone, it can't). 4.2.1 doesn't have this and it's NOT because I run out of fuel or anything like that. It's just simply stops working. Exiting the simulation and loading the Current State fixes the thing, but still annoying.

- What are radiators for? If I understand correctly, they should radiate heat off but I really can't see any difference on any instrument whether I have them out or not.

 

[jedidia]

the proposed PeA in the slingshot MFD is waaaaay below the Moon's surface.

I'm not sure I understand correctly. Might it be that you confuse PeA with PeR? PeA is periapsis ALTITUDE, so for it to be below surface, it would have to be negative. a PeA of 0 is right on the surface, and a PeA of 1.4M would be 1400 km above surface. For the moon, that's not really too close.

AB just sits there, trying to turn but since the controls are gone, it can't

I never had a similiar problem. Then again, I never fly a DGIV, so there might be a slight incompatibility somewhere... couldn't imagine how, though.

IMFD 5.3 provides more information than 4.2, if you don't need that, stick with the older one. There is some stuff that is different with 5.3, and using the tutorial for 4.2 might not allways get you what you want in 5.3 (for example, I seem unable to get the Orbit insertion program to work with excentricity, I have to use apoapsis instead...)

 

[Hmuda]

I'm 100% sure it was PeA since it showed a negative number (especially obvious since it was bright red to be sure to catch the orbinaut's eyes, sorry for not making this "little" detail clear ). As I said, it was easily corrected by changing the arrival date and managed to finish the tutorial without crashing anywhere, just want to make sure where things went wrong.

Thanks for clearing up the IMFD differences. I'll stick with the older one. Orbit insert isn't really a problem, I just use the technique explained by José in his tutorial (take the half of BT and start burning before PeT-'that time').

 

[ar81]

It took me some time to understand concepts for interplanetary flight from the different versions of the manual and all the posts I have seen at the forums and many tutorials.

I tested what I knew with a Delta Glider IV to see how it worked, and it worked fine. I used 4.2.1 because this is the user interface I know better. Since user interface has been changing since then, a new learning curve was needed for each new version, and since I understand newer versions had issues, I preferred to attach to the old 4.2.1.

If I understand your problem correctly, PeA might not work for you. PeA is measured in meters. So if you enter 300, you have 300m, not 300 km.

Also, as time passes, plotted trajectory changes. I think it may have to do with either integration inaccuracies or with trajectry perturbations caused by other bodies in the solar system, but I am not sure, since I did not code IMFD.

So setting trajectory too early and too low PeA, may lead to a crash.

 

[Hmuda]

I attached an image of the thing in question.

As soon as I enter the Moon's SOI, I make an approach burn to direct me to a 300km high PeA at 7°EqI.

Then, as the tutorial suggests, I set up an off-plane intercept for the ISS, setting up the arrival date as instructed. After that, I open te slingshot menu, select Course/Retrograde and the necessary course is way inside the Moon, as seen in the picture. I would need to lower the arrival date to at least 60252.5 to avoid crashing.

Also, what I don't understand, is why did I just make an approach burn, when the slingshot burn would take me to the other side of the moon (approach places me to a pro-grade slingshot, while I need a Retrograde one)?

The most helpful tutorial I've ever read, but this part is the only thing that seems flawed a bit. I can correct the course so the sling does slow me down, but something seems off in the original instructions.

 

[ar81]

Please post the scenario, before you started to setup IMFD for the slingshot, so I can reproduce the problem.

 

[Hmuda]

I appreciate you looking into this. Here are the file(s) you asked for.

1: I just entered the Moon's SOI and made the approach burn so that I would place the periapsis at 7°EqI and at 300km altitude. Nice, clean pass.

2: Configured the Off-Plane Intercept screen so that I would arrive at the ISS at 60251.0.

3: I open the Slingshot screen on the right and change it to course/Retro-grade and I get this.

I'm sure I'm missing something that I forgot from earlier lessons.:embarrassed:

Thanks again for looking into this.

 

[jedidia]

I would need to lower the arrival date to at least 60252.5 to avoid crashing.

You mean you need to raise it (as seems obvious, since in your screenshot you posted it shows 60251). I got confused there for a minute. I can't take a look at your scenario currently. From intuition, my best guess would be that you're setting up the burn a little late (but that's judging solely on you MJD. if you planed to get there at 6049, 6048.82 seems a bit late). But this really is just a guess. I'll wait and see what ar81 comes up with.

That said, first time ever I see a negative ApA. I didn't know the MFD could produce that until now (then again, I'm not using it SO frequently).

 

[Tommy]

As I recall, you can set planet approach to a retrograde orbit by giving it an Inc between 90 and 180 degrees (with 180 being equatorial retrograde).

 

[Hmuda]

As I recall, you can set planet approach to a retrograde orbit by giving it an Inc between 90 and 180 degrees (with 180 being equatorial retrograde).

I'll try that.

By the way, just how close/far should I be from the planet to start burning for the slingshot?

 

[Tommy]

You should be inside, or very close to, the Moons SOI, after that watch the dV required. If it's dropping wait, if it's rising use the AB.