RTCC Nominal Apollo 13

Max-Q

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Here you go, scn attached.
How do I use MPT? I may regret asking about more RTCC stuff... I found the MPT screens, but couldn't make sense out of it.
Also, if you don't mind, could you take a look at Odyssey's orbit? I am a bit concerned about how my PC-1 went, the dV was about 75 fps less than the flightplan dV.

Just so you know, this scenario is at 124 hours, nowhere near ascent.
I was just practicing while the crew sleeps so I know what to do in the time critical ascent prep phase.
 

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  • Apollo 13 - 124hrs.scn
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rcflyinghokie

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How do I use MPT? I may regret asking about more RTCC stuff... I found the MPT screens, but couldn't make sense out of it.
MPT takes practice. I don't know if we have any guides for initializing it but I can certainly try to help in here or on discord which might be easier (and more real time) https://discord.gg/tfY4xCsa

It is a little complex at first but it becomes super useful.
Also, if you don't mind, could you take a look at Odyssey's orbit? I am a bit concerned about how my PC-1 went, the dV was about 75 fps less than the flightplan dV.
No problem, I will see if I find anything unusual and get back.
 

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It is a little complex at first but it becomes super useful.
I'm seeing a common theme here... ;)

MPT takes practice. I don't know if we have any guides for initializing it but I can certainly try to help in here or on discord which might be easier (and more real time) https://discord.gg/tfY4xCsa
I prefer to stick with OF, but I'll keep discord in mind if I come up against anything really sticky.

Thanks again for taking so much time to help me with this stuff!
 

indy91

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You don't really need the CSI processor, it doesn't give you any more data than the launch window processor really. I kind of purposefully haven't documented the MPT much because I don't feel it is user friendly and stable enough yet to be advertised as a usable part of the MFD. And I've tried to make the MPT as optional as possible.

For your plane change burn, I don't think it worked exactly as intended. Maybe it found a time to fly over the landing site on the wrong revolution? But it's not so bad, the Ascent PAD shows a crossrange of -1.2 NM, the limit is 8 NM I think. So you don't have to go back and repeat the burn if you don't want to.

For the LLWP the insertion velocity targets that you put in P12 are inputs, on the LLWP page, Initialization, Targeting Parameters. Your CDH burn looks pretty large, so I think the standard values aren't very good for your case. I've tweaked them a bit with your scenario and got 5529 ft/s and 36 ft/s for horizontal and vertical velocity. And the resulting CDH DV was below 2 ft/s, which is definitely good enough.
 

rcflyinghokie

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Yeas as @indy91 said you don't need MPT for a mission, but if you want to learn it I am willing to give you a brief starting point walk through if you wish, but its more the "advanced" side of RTCC
 

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You don't really need the CSI processor, it doesn't give you any more data than the launch window processor really. I kind of purposefully haven't documented the MPT much because I don't feel it is user friendly and stable enough yet to be advertised as a usable part of the MFD. And I've tried to make the MPT as optional as possible.
Yeas as @indy91 said you don't need MPT for a mission, but if you want to learn it I am willing to give you a brief starting point walk through if you wish, but its more the "advanced" side of RTCC
I don't think I'm ready for advanced RTCC stuff... I have a hard enough time with basic RTCC stuff!
Once I get a handle on the basic stuff, I may want to try MPT.

For your plane change burn, I don't think it worked exactly as intended. Maybe it found a time to fly over the landing site on the wrong revolution? But it's not so bad, the Ascent PAD shows a crossrange of -1.2 NM, the limit is 8 NM I think. So you don't have to go back and repeat the burn if you don't want to.
I think I'm going to just launch with the crossrange, I don't really want to go back that far and repeat the burn...
That's baffling though, I calculated the ascent TIG and put that exact GET value in the processer.

For the LLWP the insertion velocity targets that you put in P12 are inputs, on the LLWP page, Initialization, Targeting Parameters. Your CDH burn looks pretty large, so I think the standard values aren't very good for your case. I've tweaked them a bit with your scenario and got 5529 ft/s and 36 ft/s for horizontal and vertical velocity. And the resulting CDH DV was below 2 ft/s, which is definitely good enough.
Interesting! Could this have anything to do with Odyssey being out of plane?
 

indy91

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I think I'm going to just launch with the crossrange, I don't really want to go back that far and repeat the burn...
That's baffling though, I calculated the ascent TIG and put that exact GET value in the processer.

Then that was an error. TH stand for threshold time. The descent planning processor finds a TIG (and also a time to fly over the landing site) at any point after the times you specify. So it should at least be a few minutes before the time you actually want. There is one thing I wanted to change, I want the descent planning display to actually show the time it found to fly over the landing site. That would be a good check to see if it's close to the launch time. Actual launch time happens after the CSM flies over the landing site, so I am pretty sure it found a solution for the next rev. So if you were to launch one orbit later your crossrange might be near zero :D

Interesting! Could this have anything to do with Odyssey being out of plane?

Probably not. The CSM orbit is a bit lower than 60 NM but I was also wondering why 5529 ft/s gives the smallest CDH burn. Seems a little bit low. But not too much. In any case, the optimum values are always a bit of trial and error with the insertion velocities, the standard values only work "ok" for the average mission. Might depend on CSM altitude and landing site elevation and such. Be happy that this is the last time you need to use this processor with many manual inputs, for the short rendezvous profile starting with Apollo 14 you would use the LLTP where a lot more is calculated for you.
 

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Then that was an error. TH stand for threshold time. The descent planning processor finds a TIG (and also a time to fly over the landing site) at any point after the times you specify. So it should at least be a few minutes before the time you actually want. There is one thing I wanted to change, I want the descent planning display to actually show the time it found to fly over the landing site. That would be a good check to see if it's close to the launch time. Actual launch time happens after the CSM flies over the landing site, so I am pretty sure it found a solution for the next rev. So if you were to launch one orbit later your crossrange might be near zero :D
That is it! Sure enough, the CSM should fly exactly over the landing site... on the next rev! My ignorance with RTCC strives again... :LOL:

Probably not. The CSM orbit is a bit lower than 60 NM but I was also wondering why 5529 ft/s gives the smallest CDH burn. Seems a little bit low. But not too much. In any case, the optimum values are always a bit of trial and error with the insertion velocities, the standard values only work "ok" for the average mission. Might depend on CSM altitude and landing site elevation and such. Be happy that this is the last time you need to use this processor with many manual inputs, for the short rendezvous profile starting with Apollo 14 you would use the LLTP where a lot more is calculated for you.
The flightplan actually calls for a 59.9 by 53.8 orbit after PC-1, maybe that explains the difference.
1674333208630.png


The new shorter rendezvous is either good or bad, I'm not excited to have to figure out how to do something totally different, but on the other hand it does seem easer...
Either way, Apollo 14 is next for me.
 

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That is it! Sure enough, the CSM should fly exactly over the landing site... on the next rev! My ignorance with RTCC strives again... :LOL:

Also lack of documentation of RTCC strikes again! I definitely need to add sections about the LLWP and the descent planning to the RTCC manual. At least feature wise they have reached their final form, so there is no excuse to not have it properly documented.

The new shorter rendezvous is either good or bad, I'm not excited to have to figure out how to do something totally different, but on the other hand it does seem easer...
Either way, Apollo 14 is next for me.

Definitely easier and shorter calculation procedure. I'm proud of the LLTP display, looks exactly like the real one!
 

rcflyinghokie

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That is it! Sure enough, the CSM should fly exactly over the landing site... on the next rev! My ignorance with RTCC strives again... :LOL:


The flightplan actually calls for a 59.9 by 53.8 orbit after PC-1, maybe that explains the difference.
View attachment 32148

The new shorter rendezvous is either good or bad, I'm not excited to have to figure out how to do something totally different, but on the other hand it does seem easer...
Either way, Apollo 14 is next for me.
One thing to keep in mind with the FP orbits is they take perturbations due to things like mascons into account, so the Ap and Pe change over time.
 

Max-Q

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OK, time for RTCC mega questions 3!
  • PC-2 - How to calculate. I couldn't find anything on this one in the doc
  • How do I get the Photo REFSMMAT
  • TEI - How to calculate
  • Entry Pad - How to get
  • Entry Update - How to calculate & uplink
 

indy91

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OK, time for RTCC mega questions 3!
  • PC-2 - How to calculate. I couldn't find anything on this one in the doc

We don't know exactly either. What is likely is that they changed the landing site coordinates in the RTCC to one of the photo sites and then calculated the plane change just like they did with LOPC-1. Descartes is probably a good option. Use the coordinates from flight plan page 1-22, plug them in on the Utilities, Landing Site page and leave the radius as it is. Then do the same calculation as for LOPC-1, second threshold(!) time maybe half an hour before the flight plan has a photo pass. I think that is only 2 revs after the burn itself or so. And of course check that the DV looks about right.

  • How do I get the Photo REFSMMAT

Ah this is even worse. Very strange REFSMMAT type, the definition is on flight plan page 1-5. I think the best technique is to calculate a LS REFSMMAT, but with a longitude of 20° east of Fra Mauro (don't bite me if it is 20° west) and a time that has to be not super exact, like the flight plan says, "time of crossing of the longitude of the landing site on revolution 41". I usually study these kind of things in great detail when I implement the MCC for a mission... but as you know, we haven't gotten there yet. A LVLH REFSMMAT also works very well, it places the alignment in-plane, like the flight plan says. But now the time you input is very critical...

  • TEI - How to calculate

This is covered pretty well by the RTCC MFD manual, so I would suggest reading the Return to Earth section in it, skipping the paragraph about the tradeoff display.

  • Entry Pad - How to get

Not much to it once you have saved the splashdown coordinates after calculating TEI. Just go to the Entry PAD page and calculate.

  • Entry Update - How to calculate & uplink

This would be the uplink called Retrofire External DV. That uplinks TIG, DV and splashdown coordinates. This is usually done before TEI or any of the midcourse corrections back home. If you want only the coordinates then it's called Entry Update, might be done after MCC-7. Again, those coordinates are saved when you calculate any RTE solution, may it be TEI or one of the MCCs.
 
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