Help with RTCC MFD

[MrFickles]

Hi, I'm currently on the moon with Apollo 15 and I want to know how do I compute the CSM plane change maneuver at 165h GET? I'm not used to the new RTCC MFD interface and I can't find an answer on the MFD manual. Thanks in advance!

 

[indy91]

Ah yes, I got up to a certain point updating the manual but there was still a lot to go. I will continue with that soon.

The plane change is calculated with the Lunar Descent Planning Processor (Descent Planning button). Most of its capabilities are maneuvers for the LM, but it can also calculate the plane change. Go to the page with the LDP button and then press the MOD button until it says "CSM Prelaunch Plane Change". Then you need to give it two times estimates, firstly of the plane change maneuver itself and secondly of the time you want the CSM to fly over the landing site, which is the estimated time of LM liftoff from the surface. The input times are thresholds, so you should choose these times earlier than the estimated time so that it finds the correct GETs. For Apollo 15 good inputs are 164:30:00 for TH1 and 171:30:00 for TH2, but these are just a quick estimate on my part.

Then use the DPT button to go the descent planning display and press CLC. Up to four maneuvers are displayed there, depending on the calculation mode. In this case only the first maneuver will get data. GETTH is the threshold you used and GETIG is the ignition time it found. To the right are DVX, DVY and DVZ. If you are happy with the result press the MPT button to go to the next page where you convert the maneuver to a finite burn using a specific engine. Press the THR button and type in S for SPS and then calculate with CLC. That should give you the final plane change maneuver.

 

[MrFickles]

Thanks for the quick reply! I managed to compute and execute the plane change maneuver successfully, but I ran into another problem.

I could not get RTCC MFD to calculate a REFSMMAT to uplink to the AGC. I can get a REFSMMAT solution by pressing Utility > REFSMMAT > Option : Landing site > Calculate. What I mean is that I cannot get an uplink solution afterward. Uplinks > REFSMMAT update > Calculate Uplink - nothing happens and all values remain at 00000.
For the plane change burn it was not a problem because I could use P40 to update the REFSMMAT, but now I cannot go back to the landing site REFSMMAT in preparation for rendezvous.

Any idea what is going on?

 

[indy91]

Ah, I made the REFSMMAT uplink page use the same kind of input format as the real RTCC needed. In most cases I have only done that when a mission planning mode is activated in the RTCC MFD, mostly because that feature still needs a lot of work and manual writing to be usable by all users. But I guess in this case I already require it of every user, at least for now. So what you need to input there is this:

C12,CMC,CUR,2;

C12 is the code for "Initiate REFSMMAT Update"
CMC is the computer to uplink to, LGC being the other option there.
CUR is the type of REFSMMAT, it's short for current. That is the generally used REFSMMAT type in the MFD, there are others, but only really usable in the mission planning mode.
2 is the code for a desired REFSMMAT uplink. The other option is 1, changing the acutal REFSMMAT in the computer (which you will rarely do).

What I will probably do is simplify this again, so that the only required input is the choice between desired and actual REFSMMAT.

 

[MrFickles]

Thanks indy, its working now. Does every REFSMMAT update require that text string from now on and I swap 'CMC' for 'LGC' as required?

Thanks for all the work you've done with the MFD. It's such a powerful tool, but unfortunately, it's not very user friendly.

 

[indy91]

I'll change it so that the only required input is the REFSMMAT type (desired or actual). I know it's not very user friendly, I hope I can improve in that regard. Constant changes and trying to make things more realistic always gets in a way with that. Hopefully I can reach a point where I'm not doing major changes all the time, and where using the different pages is a bit more consistent and where the manual is fully up to date with more examples.

 

[MrFickles]

I think a difficult to use user interface is fine as long as the documentation covers usage of the MFD.

1 last question. Whenever my LM lifts off the moon on any mission, the entire LM tips backward (or possibly the 2 vehicles spawn in like this). In my Apollo 15 flight, it's so bad that the ascent stage crashes into the ground and I have to cheat. What is happening?