Apollo 12 Checklists

indy91

No, for Apollo 12 that sounds exactly right. It's a hybrid mission profile, so the trajectory after TLI, as planned, is free-return with a closest approach to the Moon of 1850 NM. That needs to be lowered to 60 NM with the MCC and in the flight plan that takes 68.8 ft/s at the time of MCC-2. The earlier you do this burn the lower the DV for it, so 56.3 ft/s for MCC-1 sounds exactly right.

But MCC-1 would only be done if MCC-2 has an unacceptably large DV, so my suggestion is to skip MCC-1 and do the maneuver like planned at MCC-2, that let's you stay closer to the flight plan.

rcflyinghokie

LM Junky
No, for Apollo 12 that sounds exactly right. It's a hybrid mission profile, so the trajectory after TLI, as planned, is free-return with a closest approach to the Moon of 1850 NM. That needs to be lowered to 60 NM with the MCC and in the flight plan that takes 68.8 ft/s at the time of MCC-2. The earlier you do this burn the lower the DV for it, so 56.3 ft/s for MCC-1 sounds exactly right.

But MCC-1 would only be done if MCC-2 has an unacceptably large DV, so my suggestion is to skip MCC-1 and do the maneuver like planned at MCC-2, that let's you stay closer to the flight plan.
I was speaking of the EMS cutoff dV being high.

indy91

Yeah it's a bit high, but as you know the TLI PAD method of calculating that value is a bit inaccurate. Maybe that effect is just worse for Apollo 12 for some reason. It tends to be off by maybe 40-50 ft/s, so 80 is an outlier but not too terrible.

Max-Q

99 40
So I have calculated my MCC2 and it is very close to the flight plan value.
Now how do I get my PAD and uplink it to the CMC?
Couldn't make heads or tails of the RTCC manual for this part.

rcflyinghokie

LM Junky
So I have calculated my MCC2 and it is very close to the flight plan value.
Now how do I get my PAD and uplink it to the CMC?
Couldn't make heads or tails of the RTCC manual for this part.
So on the main menu of the RTCC menu there is an uplinks button, here you have all the CMC and LGC uplinks.

Here you will uplink a CMC CSM navigation update (state vector) and the CMC external dV (target load)

All you do for the SV is choose the target and hit calculate and for the target load just use calculate once you have computed the maneuver and it should come up.

Max-Q

99 40
After calculating the maneuver in the Maneuver targeting/Midcourse page, I went to Uplinks/CMC external dV and hit calculate.
It shows data from TLI! dV +10448.2 and TIG 2:47:19.64!
What step did I miss here? Do I need to do something else in Maneuver targeting/Midcourse? My MCC2 shows up in column 1 with all the data.

rcflyinghokie

LM Junky
After calculating the maneuver in the Maneuver targeting/Midcourse page, I went to Uplinks/CMC external dV and hit calculate.
It shows data from TLI! dV +10448.2 and TIG 2:47:19.64!
What step did I miss here? Do I need to do something else in Maneuver targeting/Midcourse? My MCC2 shows up in column 1 with all the data.
Did you use the MPT for TLI?

indy91

I think you still need to select which column and engine you want to use for the burn before it is available for the Maneuver PAD page.

When you have the maneuver in one of the Midcourse Tradoff columns press the ENG button and that gets you to the page where you can do that. Select column 1 (probably) there and enter S for the SPS for the maneuver. Then press CLC and that then has converted the impulsive burn that the midcourse calculation came up with (instant velocity change) to a finite burn using a specific engine. The actual TIG will also have slightly changed in that process. Only now is the maneuver available elsewhere in the MFD for Maneuver PAD and uplink.

Oh and also don't forget to use the F30 button to store the data table associated with your MCC-2, or else MCC-3 and 4 can't be targeted properly. But I think that is all described in detail in the manual. I also recently added a section for the Apollo 12 MCC-2 specifically to the manual, it goes into some details on how to fine tune your LOI-1 time of ignition, if that is something you want to do.

Max-Q

99 40
MCC2 complete.
However, I think I may have made a mistake uhh... somewhere.
My residuals are -0.2 +1.9 +4.3, much larger that usual for my SPS burns. At ignition, pitch and yaw kinda went wild then after some rapid SPS gimballing the attitude stabilized.
I am sure I entered the SPS trim angles correctly from the MCC2 pad.
Should I just null the residuals and continue on my way, or did I do something wrong?

indy91

I wonder if it's just a missing V46E after a V48. If you haven't done a V46 since Earth orbit the TVC might still be set up for CSM alone or so. Wrong trim angles set in V48 would mainly give you a transient at ignition, after which it should be able to recover. So if you think it's possible that you haven't done a V46 in a while, maybe try the burn again to see if that changes anything? If not I can take a look at the scenario.

Max-Q

99 40
Yeah, I don't remember having done that.
Will try V46.

indy91

V46 is a weird verb, the LGC doesn't even have an equivalent. I am never quite sure when it's important to do it after the V48, but looking at the code for V46 it seems important when you switch the vehicle configuration in the first display of V48 (the first digit of N46 where 1 = CSM, 2 = CSM/LM and 3 = Saturn stage). The checklists for V48 are usually always doing a V46 aftwards, but I guess it's mainly relevant for when you change the vehicle configuration. If you haven't done that at least once after TLI (you launch with the DAP set to Saturn stage) then the TVC is probably not set up correctly.

Max-Q

99 40
Here are two scenarios, TIG minus 2 minutes, and after shutdown showing my residuals.
Did V48 and then V46.
Still more of the same.

Attachments

• 507_tig-2m.scn.txt
225.9 KB · Views: 47
• 507_residuals.scn.txt
226.8 KB · Views: 47

indy91

Yeah I am getting the same thing. So I think the RTCC MFD wasn't set up quite right, missing one minor step. On the configuration page of the MFD next to the TYP button it says "CSM". That means some parts of the RTCC MFD treat the vehicle configuration as CSM alone. If you press the TYP button once it will switch to "CSM/LM docked". That is what you want for the next while.

And I believe this has an effect on the SPS trim angles the Maneuver PAD calculates. So it calculated the angles for the CSM alone, which are quite different. Maybe for a longer burn the TVC recovers, but for a short burn you will get residuals. If I use 0.1x time acceleration I have enough time in your T-2min scenario to exit out of P40 (V37E 00E), then start V48 and enter the correct trim angles (about +0.96° for pitch and -0.23° for yaw). And then go back to P40. With that I get a good burn.

A few other minor things I noticed in your scenario. Not all pitch and yaw thrusters are enabled (Auto RCS Select). That might be a configuration for PTC or so, but normally you want all pitch and yaw thrusters enabled, or else doing an attitude maneuver causes a translation, alterating your trajectory slightly. For roll you usually have either A/C or B/D quads enabled, but during a burn you often want all thrusters on. And you probably didn't care for the SCS in this case, but I think it was set to Att 1/Rate 2 (which is the attitude hold mode) at a different attitude than the burn attitude. On FDAI 2 you can see the error needles have a large deflection. If you switch to the SCS in that T-2min scenario you would get a lot of RCS firing. Just put the three BMAG switches to Rate 2 and then back to Att 1/Rate 2 to hold the current attitude.

Max-Q

99 40
Thanks! With the stuff you pointed out fixed, I got a good burn with minimal residuals. The attitude was rock solid for the entire burn.

rcflyinghokie

LM Junky
Thanks! With the stuff you pointed out fixed, I got a good burn with minimal residuals. The attitude was rock solid for the entire burn.
RTCC takes a while to learn, just ask @indy91 how many times I had him walk me through things

But once you grasp the concepts it lets you fly any mission.

Max-Q

99 40
In light of some of the major improvements to NASSP since build 1727, I would like to update to the latest build. However I don't usually like to update during a mission but I have a feeling that Apollo 12 may go on for a while... Would there be any issue updating to the latest build (1736) mid-mission?

rcflyinghokie

LM Junky
In light of some of the major improvements to NASSP since build 1727, I would like to update to the latest build. However I don't usually like to update during a mission but I have a feeling that Apollo 12 may go on for a while... Would there be any issue updating to the latest build (1736) mid-mission?
I think you should be fine, its only been 2 weeks so you shouldn't need any scenario edits etc.

Max-Q

99 40
At GET 56 hours, the flightplan says to uplink delta H if required. What is this, how do I know if it is required, and how do I uplink it?

Miriam

Active member
That's P23's horizon altitude. Houston would gather data from the P23s Dick Gordon did on launch day and derive an improved value for delta H from that. The background is that the edge of earth's atmosphere to space is not a sharp line, but rather fuzzy, and every CMP tended to mark on a different spot on that fuzzy glow. As you couldn't simulate that on the ground, the only way to solve the problem was to let the CMP do some P23s and calculate backwards where that spot is.
We can't do that (at least I haven't found any function like that in RTCC MFD), so just leave it.