Update IMFD - LTMFD for Orbiter 2016

[JonnyBGoode]

Last night, I was running the Europa to Callisto tutorial scenario. Everything went by the numbers until I got to the orbit insert burn. The engine never shut off after zero eccentricity was reached and I ended up in a collision course with the moon. I thought I had done something wrong until I came here and discovered it was an apparent IMFD glitch.

Which is fine, there's no big skill involved in manual orbital insertion burns.

 

[Eduard]

Hi, I see that IMFD has been updated yesterday, I don't know exactly what changed. But it reminds me of something important that I wanted to report already a few months ago (it still applies to the newest version as well):

The Delta Velocity program does not work properly.
The remaining DV in the BV view does not count down well and never reaches zero. And therefore the Autoburn also never cuts off.
But even when doing the burn manually, when not using Autoburn, the remaining DV never counts down. So this is not an AB problem, but this is a problem specific to the Delta Velocity program.
I compared the same testscenario between IMFD in Orbiter 2010 and IMFD in Orbiter 2016 to be certain about this before posting it here.

 

[boogabooga]

That's exactly what just got fixed, as well as Orbit Insert, etc.

http://www.orbiter-forum.com/showthread.php?t=37864

 

[Eduard]

That's exactly what just got fixed, as well as Orbit Insert, etc.

http://www.orbiter-forum.com/showthread.php?t=37864

Ok, thank you, I didn't see that there is a new thread.

But I just tested it with version 5.7 installed and I am still experiencing this bug. I also removed the 5.6 dll to be shure that I am using the newest version.
I don't understand what I'm doing wrong.
B.t.w. I tested it using the DG-EX vessel, because I had a good saved scenario with this vessel.

 

[boogabooga]

It's working for me. (delta glider).

 

[Eduard]

It's working for me. (delta glider).

Ok, see the attachment. I made this scenario file. I edited it so that I am using a default Deltaglider now and not the DG-EX anymore.
It's a mid-course correction to align the trajectory with Brighton Beach.

It still doesn't work for me in Orbiter 2016 with IMFD 5.7.
I only see it working correctly in Orbiter 2010.

Does this scenario do the burn correctly in your 2016 installation?

Update: When I just do a simple test with a Deltaglider in low earth orbit and then do a simple test with the DV program doing a random short burn, then this indeed works and the remaining DV drops correctly ending with a correct AB cut-off.
But that is very different with the added scenario here.

 

[boogabooga]

Weird. :blink:

I can confirm the error when I use Eduard's scenario. But it has been working for me otherwise.

I haven't found anything different about Eduard's scenario, except altitude.

 

[jarmonik]

The DeltaVelocity appears to be working if the reference frame is changed from "Vel.Frame" to "P30 LVLH". But I have no idea what's going on there and from where the problems are originating. I really haven't touched that code during the past 10 years.

 

[Eduard]

The DeltaVelocity appears to be working if the reference frame is changed from "Vel.Frame" to "P30 LVLH". But I have no idea what's going on there and from where the problems are originating. I really haven't touched that code during the past 10 years.

Ah, now we can start understanding things ...

I tried the "P30 LVLH" setting in my testscenario now and it works indeed well (of course to get the right trajectory correction I had to ajust all settings again, but it works).

Very important detail: The screnario is just outside of Earth's major SOI, so the dominant body is the Sun there.

Realising this leads us to the following question:
When we forward until whe are in the Moon's major SOI, does "Vel.Frame" work correctly then?
Yes, it does. I tested it, the remaining DV goes down in the right way and the AB automatically cuts off.

This SOI issue explains why the burns in LEO go well.
Only when the Sun is the dominant body, "Vel.Frame" goes wrong.

 

[boogabooga]

Out of curiosity, what happens if you disable the wind or terrain? If the problem is specific to Orbiter 2016, perhaps the cause is as well. If IMFD somehow assumes smooth spheres with no wind, even if unintentionally, there will be problems.

Something to test. :hmm:

---------- Post added at 09:16 PM ---------- Previous post was at 07:24 PM ----------

Edit:
Disabling wind and terrain had no effect.

Very important detail: The screnario is just outside of Earth's major SOI, so the dominant body is the Sun there....Only when the Sun is the dominant body, "Vel.Frame" goes wrong.

The "Vel. Frame" reference does work again if you switch the reference body in "Delta Velocity" to "sun". So probably from now on we just have to be careful in IMFD to make sure our reference is actually the same as our actual current major body. This was probably always a good idea, but seems there was more tolerance in Orbiter 2010.