Discussion LaunchMFD pitch programmes repository

[Enjo]

LaunchMFD now supports pitch programmes as a contrast to full automatic spacecraft guidance. Please post your pitch programmes in this thread, providing info about:

- vessel name as well as its exact configuration path and file name, provided by LaunchMFD
- how much fuel is left after orbital insertion
- the pitch programme itself
- PID settings
- whether complex flight model was on

I will select the best performing programmes and include them in next LaunchMFD releases, however under different directory name, not to overwrite individual users' files. Of course the work will be credited.

 

[agentgonzo]

As I recall, the DG-IV has a launch-to-LEO pitch programme in it's builtin autopilots. It may be useful to post that pitch programme here in a LaunchMFD-friendly format.

 

[Wishbone]

Some more discussion about DGIV programs here: http://www.orbiter-forum.com/showthread.php?t=18144

 

[Enjo]

OK let me start then.

Ship: Deltaglider IV

Complex flight model was off

Fuel left: 4.64k

The config file is:
Config\MFD\LaunchMFD\DeltagliderIV.cfg

contents:

ATMO_XY = 7 3 0

;Credits: Wishbone, Tommy, PeterRoss
PITCH_PROGRAM
0.020 20    ;Take-off pitch
0.700 43   ;climb steady while making turn
1.500 80   ; Thanks go to Tommy! He saved me abt. 100 kilos of fuel!
10.000 75
11.000 70
12.000 65
13.000 60
14.000 55
15.000 50
16.000 45
17.000 40
18.000 32
19.000 26
20.000 20
22.000 18
24.000 16
26.000 14
28.000 12
29.000 10
30.000 8
70.000 8    ; Press DEF to disable pitch guidance and use trim to hold ship in apoapsis
400.0000 0  ; circularization is required. Leaves 4.64k of fuel.
END_PITCH_PROGRAM

 

[astrosammy]

With Atlantis, I'm having problems to get a good transition from pitch program to PEG.
It violently pitches up, overshoots the altitude target,
violently pitches down because of this,
undershoots the altitude, and then pitches up again,
pitching to 90° and starting to spin after it crosses the 90° line.
Increasing the altitude target (I'm using 108km) doesn't help.

Here is the file, needs to go into Config\MFD\LaunchMFD\Atlantis.cfg

After switching off the autopilot as soon as I reached 100 km
and manually completing orbit insertion, I had 40k of fuel left, with complex flight model on.

SPACE_XY = 2 6 0
UPSIDE_DOWN = TRUE
ROLL_ALT = 0.17 

PITCH_PROGRAM
0 90
0.17 88
5 65
10 56
15 48
20 41
25 34
30 28
35 22
40 16
45 16
50 17	;SRB sep
55 18
60 19
85 19
90 18
95 16
100 14	;press DEF here, manually adjust pitch
END_PITCH_PROGRAM

 

[Enjo]

With Atlantis, I'm having problems to get a good transition from pitch program to PEG.

I'm almost sure that the PEG doesn't take the tank's mass into account. If taking into account all stages / parts were done right in my PEG, it would do everything automatically, but this is work for holiday. In case of regular rockets / launchers, the transition is possible because the PEG starts to operate on the last stage.

 

[jgrillo2002]

I'm almost sure that the PEG doesn't take the tank's mass into account. If taking into account all stages / parts were done right in my PEG, it would do everything automatically, but this is work for holiday. In case of regular rockets / launchers, the transition is possible because the PEG starts to operate on the last stage.

So for right now, you are implying that the PEG system works only with SSTO type vehicles?

 

[Enjo]

Actually I should eat my own words now.
I've checked the variables of PEG during Atlantis ascent and they matched with Orbiter reality. This only implies that PEG doesn't work too well for Atlantis, or I just can't configure the pitch program correctly.

About SSTO:
No, using pitch program, you should be able to put into orbit any 2-stage craft, where the pitch program is used for the first stage (booster assisted). After the boosters are separated, the pitch program should end. Then the PEG kicks into action and uses the current situation to automate the remaining part of ascent. It assumes that the current stage is the final stage. This is important information and I will include this in the manual in the next release soon.

Note however, that if our task is to use PEG after booster separation, and we know with good approximation when the boosters will separate, then it would be more reasonable to use time based pitch program than altitude based, where the last point in time would be a few seconds after separation. This is why in the next release I will add PITCH_PROGRAM_TIME option, and change the current PITCH_PROGRAM to PITCH_PROGRAM_ALTITUDE.

 

[Cras]

:facepalm: and here I thought it already was time based. You mean this whole time it was figuring the pitch based on altitude?

And I think you might be one to something with the tank weight. That launcher I was using when I talked to you before, that has an external tank. I wonder if the tank weight as it runs out of fuel is messing with the stability of the PEG close to MECO. I have it set up now that the tank pretty much runs out right at MECO, give or take a second at most.

 

[yagni01]

Actually, why not create a section and post the programs on orbiterwiki, instead. Should be easier to find.

 

[Enjo]

I'd like to announce that the MFD now uses two different pitch program tags:

PITCH_PROGRAM_TIME
and
END_PITCH_PROGRAM_TIME

for time based pitch programs. Support for the altitude based is retained, using the following tags:

PITCH_PROGRAM_ALTITUDE
and
END_PITCH_PROGRAM_ALTITUDE

 

[Gendo]

I assume LaunchMFD probably isn't going to work with the SpaceX model collection. Replicated the pitch program from the F9's internal autopilot, but it seems to have no effect on the rocket. Pretty much just ends up corkscrewing around zenith. Tried various numbers for the first two spots in both sets of XY and Bank (between 0.5 to 15), but didn't improve the odd behavior much. Even trying to at least manually get it going in the right direction, it still fails to lock on. lol

PITCH_PROGRAM_ALTITUDE
Earth
0 90
1 80
5 68
20 48
80 0
END_PITCH_PROGRAM_ALTITUDE

Didn't have any problem intercepting ISS with the DG space plane, so maybe I'll try some other rocket.

 

[Cras]

Launch MFD uses RCS, so if the rocket uses thrust vectoring to guide its sexy self up to orbit, like the Shuttle Fleet for example, then Launch MFD can do nothing but watch while the ship just kind of....goes off and crashes.

If the stack uses RCS for attitude control during its ascent, like say Multistage vessels, or the DG, then Launch MFD will perform beautifully every time.

 

[Gendo]

Launch MFD uses RCS, so if the rocket uses thrust vectoring to guide its sexy self up to orbit, like the Shuttle Fleet for example, then Launch MFD can do nothing but watch while the ship just kind of....goes off and crashes.

If the stack uses RCS for attitude control during its ascent, like say Multistage vessels, or the DG, then Launch MFD will perform beautifully every time.

Could be that it's using gimbaled main engines on that F9 model, but there's just no discernible animation of it. I do hear RCS thrusters intermittently during first stage ascent, but perhaps they're just for roll control. idk

Tried to redo the cfg file to this, but it still ignores the pitch program.

SPACE_XY = 2.5 16 0
SPACE_BANK = 1 12 0
ATMO_XY = 2 2.5 0
ATMO_BANK = 3 6 0
NEXT_LAUNCH_TIME = 230
SYNCHRO_OFF_BY_RATIO = 0
ATMO_CONTINUOUS_CONTROL_SWITCH_ANGLE = 90.0
ATMO_BANK_TARGET_WINGS_LEVEL_SWITCH_ANGLE = 5.0
ROLL_NEEDED
UPSIDE_DOWN = TRUE
PITCH_PROGRAM_TIME
Earth
0 90
15 85
90 50
151 0
END_PITCH_PROGRAM_TIME

Oh well. It was mostly just a test anyways. I'm obviously an Orbiter noob. Would be neat if Enjo were able to figure out how to utilize gimbal engines in a future version of LaunchMFD, but no biggie.

Thanks for the assistance Cras.

 

[Enjo]

Would be neat if Enjo were able to figure out how to utilize gimbal engines in a future version of LaunchMFD, but no biggie.

I'm slightly burned out as a developer for Orbiter. I have now wife and a kid, plus I'm starting to write a PhD thesis, on which I need to focus.
What I'd really like on the other hand, is more cooperation between addon developers, for example: since we already have a working pitch program in Launch MFD, then why don't the vessel developers cooperate with each other and with me to utilize what is already in Launch MFD, so that their vessels can be guided by it? It seems that everybody wants to have their fully own toy. With the current trend I'd never be able to keep up with such ideas on my own. That's why I've decided to quit chasing it.