SSU Orbit Ops - X,Y and Z DV's

[dabella]

Team,

I have some background skills about Orbit Operations with the standard Orbiter MFD's (Sync, Align) using prograde, retrograde, orbit normal and antinormal burns.

Now I'm trying to project these skills in the CRTMFD of SSU and I will be really thankful if someone can give me tips to accelerate my learning process in regard to this.

Looking at MM105 and 202 that are the main modes I want to use for a OMS-2 and later to target the ISS orbit, I have read a lot of how they work and basically I need to get more info about how to get the DV’s for X,Y and Z. I understand what the axes stand for and that for a prograde burn in OMS-2 I’ll need to put a number in the DVX (item19) but I really don’t know how to calculate it.

I have read about the EquationMFD and the IMFD. The first one seems to give you the tools to calculate this but in a lot of steps. The second one I heard is easier but I don’t find it in Orbit-Hangar.

So, if anyone can give me a tip here, I will be more than thankful J
Am I in the right path? Is there something I am missing?


Marry xmas, happy new year all,

Daniel

 

[Urwumpe]

You just calculate the velocity changes between two orbits... search for Interplanetary MFD, it can give you good numbers without requiring many manual calculations. Alternatively you just use the formulas from your favorite text book,... for example the Fundamentals of Astrodynamics.

 

[C3PO]

EquationMFD is quite easy to use when you get up to speed.

It takes a few steps to get the result, but you don't HAVE to press [t] ASAP.:lol:

 

[dabella]

Thanks guys,
I now have both MFD's so i will make it through
It seems that some calculations are unavoidable if we like this

Daniel

 

[Urwumpe]

Thanks guys,
I now have both MFD's so i will make it through
It seems that some calculations are unavoidable if we like this

Daniel

Remember the different coordinate systems... orbiter is for example left-handed, the Shuttle is right-handed, etc.

 

[C3PO]

I made an Excell sheet that calculated the most common burns, when MultiOrb was "new". Maybe I could make a SSU version when it's released......... eventually.

(If I can find it :lol


-----Post Added-----


Now I KNOW I'm getting old! I've already made a SSU version.:lol:

You can get a copy here.
There are two ways to use it.

Always start by pressing reset!
1:
Set up a maneuver with TranX.
Rotate the orbiter into the crosshair (TransX).
Pause simulation.
Note following values:
MET
α (pitch)
β (yaw)
ΔV (m/s)
ΔT (Time to maneuver)
Set Rotate ΔV Vector to 'yes' (1)
Enter all these into the excell sheet, and the yellow fields tells you the values to enter into the DAP.

2:
Pause simulation.
Note following values:
MET
sma
Ecc
PeT
Set Rotate ΔV Vector to 'no' (0)
You have a choice to:
Alter your PeD
Alter your ApD
Circulize (between current PeD and ApD)
Enter the value of your choice, and press the calculate button. The yellow fields.... You'll know what to do next.:lol:

You may need to trim with RCS, but hey, that's what astronauts are payed to do.

 

[dabella]

SSUltraCalc

This is great C3PO!

I found your Excel sheet the other day making searchs about this topic in the forum, but I fail to use it as i didn´t understand it.

Now, with this brief explanation you gave, I think I'm set to do it on my own :speakcool:

Cheers,
Dan

 

[kwan3217]

Time for me to plug my own solution, BurnTimeMFD. This one will help you calculate both burn magnitude and TIG. Go get it at OrbitHangar.

After ascent, put the CRT into ops 105, and bring up BurnTimeMFD on some other panel. Switch the mode "MOD" to apoapse, then press the "CIR" circularize button. This will calculate the required DeltaV in m/s and time from now to TIG. Then just convert the DeltaV to feet per second (divide by 0.3048) and enter it as item 17 (positive), and pause the simulation at some convenient point, convert the time to go to minutes and seconds, add it to the current MET, and enter it as items 10-13.

Now, push the "ARM" button on the burn time calculator to turn off the auto burn, or else the CRT and burn time calculator will both try to control the burn.

 

[SiameseCat]

Then just convert the DeltaV to feet per second (divide by 0.3048) and enter it as item 17 (positive).

The DV should be entered as ITEM 19, not ITEM 17.

 

[Donamy]

Is the CRT linked to the event timer ?

 

[SiameseCat]

No; the CRT MFD burn timer is not linked to the panel event timers.

 

[Donamy]

I tried an OMS 1 burn, but after the burn was complete, I changed to OPS 105 PRO, the screen came up, but the ITEM 27 is still checked "*". Is this a bug or is there a way to reset it ?

 

[Urwumpe]

I tried an OMS 1 burn, but after the burn was complete, I changed to OPS 105 PRO, the screen came up, but the ITEM 27 is still checked "*". Is this a bug or is there a way to reset it ?

Should be a bug. The transition to OPS 105 is a full reload of new parameters.

 

[DaveS]

Noticed the same thing when doing a transistion between MM105/106.

 

[SiameseCat]

What's the correct bahaviour for the 104/105 and 105/106 transitions? At the moment, all settings are preserved during these transitions. The attitude autopilot is shut off during the 104/105 transition, but retains its settings during the 105/106 transition.

 

[DaveS]

The attitude autopilot is shut off during the 104/105 transition, but retains its settings during the 105/106 transition.

Yes, but the bug is that you can't turn it off with another ITEM 27 after that! So you have to remember to ITEM 27 before the transistion.

I believe settings are reset between transistions.

 

[SiameseCat]

Yes, but the bug is that you can't turn it off with another ITEM 27 after that! So you have to remember to ITEM 27 before the transistion.

I believe settings are reset between transistions.

Does this include the attitude autopilot, or just the burn settings?

 

[Urwumpe]

What's the correct bahaviour for the 104/105 and 105/106 transitions? At the moment, all settings are preserved during these transitions. The attitude autopilot is shut off during the 104/105 transition, but retains its settings during the 105/106 transition.

From what I can decypher, the different Maneuver displays use different I-loaded data initially and the settings of the previous mode are overridden in the moment you have a major mode transition (for example 104 -> 105).

You have to confirm the data by selecting ITEM 22/LOAD except for MM104, where LOAD is selected automatically. After the transition from MM104 to other modes, LOAD will flash as request to confirm the changed data. LOAD will also flash if a maneuver is up-linked from the ground or you do keyboard entries on the data after it was loaded.

The * next to MNVR will only appear if the error difference between current attitude and desired attitude is bigger than 8°, but the automatic maneuver will still be executed if the DAP is set to AUTO.

Also, you can only load the abort targets (ABORT TGT) in MM104 or MM105. Allowed entries there are 0 (No abort target), 1, 3, 4 and 5 in MM104 and 0 - 12 for MM105.

I suspect the abort targets are also I-Loads and stored in the OPS1 tapes.

 

[Donamy]

Also, the weight needs to count down during the burn.

 

[Urwumpe]

And the burn should only be started if EXEC is pressed shortly before TIG, with shortly being an I-Loaded value, usually 15 seconds. The Text EXEC in the top right corner should flash in that time until EXEC is pressed on the keyboard.