RTCC Nominal Apollo 13

[Max-Q]

Thanks to my previous attempts at Apollo 12, I have successfully arrived in lunar orbit.
Now I am ready to calculate DOI and I cant seem to figure it out. I think I found the DOI processer, but can't seem to get anything useful out of it.
Also, looking ahead in the flightplan I'm not sure about some other RTCC stuff:

• Obviously DOI
• At 94:00 it mentions a possible "Tweak Burn" at 94:40. How do I know if it's required and how to calculate?
• At 97:30: "Update to CSM - Undock & Sep Time & IMU Pitch" Huh?
• At 98:00: AGS Abort Constants, DAP Data - How to get these?
• At 98:10: LGC Abort Constants, EMEM Update - Same ^
• At 98:20: AGS K Factor - What?
• Where/how do I get my RCS SEP pad?

OK, I guess that's enough questions for one post! Sorry for the long list, I have bad internet and like to fly long stretches of mission at once.
Thanks in advance!

 

[rcflyinghokie]

Ok lets see if I can tackle these!

If you haven't already checked it out, the RTCC input guide can help with many of these. Its found in your orbiter install under \Doc\Project Apollo - NASSP

Obviously DOI

You compute DOI for the CSM the same way as you did with the LM.

At 94:00 it mentions a possible "Tweak Burn" at 94:40. How do I know if it's required and how to calculate?

I believe this was a ground calculated orbit adjustment in case the orbit perturbed too much. You wont need this in NASSP. I think its calculated the same way as DOI-2 was for 17 but you shouldnt need it for 13.

At 97:30: "Update to CSM - Undock & Sep Time & IMU Pitch" Huh?

This would be updates to the flight plan sep time and expected IMU pitch at sep. Sep was planned to be performed with undocking for 13, so you would undock at sep attiude and the sep burn was 1fps with -X. To accomplish this you can use RTCC and compute a burn with dvz being -1.0 and the sep time from the flight plan and it should give you a pitch pretty close to the flight plan. Just remember when you have P41 up, you burn -X, so you will have 2.0fps on your R1/EMS not zero.

At 98:00: AGS Abort Constants, DAP Data - How to get these?

DAP data will be your CSM/LM weights you can get those with the RTCC MFD under DAP PAD. Abort constants you can use the ones in the LM activation checklist and fine tune some of them using your PDI PAD.

At 98:10: LGC Abort Constants, EMEM Update - Same ^

This would be uplinked if necessary, not necessary do update these in NASSP.

At 98:20: AGS K Factor - What?

This is the time difference between the LGC and AGS. The initial k factor is just the initial time bias. After you have the AEA clock set, you can use RTCC, AGS SV pad to calculate k factor.

Where/how do I get my RCS SEP pad?

As I stated above, the pad will be the sep time from the flight plan and dVs will be 0, 0 ,-1.0. This in P30 will allow P41 to have the correct attitude, then you burn -X (ie away from the LM) for the actual sep.


Hope this helps!

 

[Max-Q]

If you haven't already checked it out, the RTCC input guide can help with many of these. Its found in your orbiter install under \Doc\Project Apollo - NASSP

I was able to figure out LOI with that, but I seem to have a hard time understanding the RTCC documentation for some reason.
Still very helpful, though.

You compute DOI for the CSM the same way as you did with the LM.

I’ve actually never calculated DOI with RTCC, by the time I got there in 12, MCC support was implemented.

Everything else makes sense!

 

[rcflyinghokie]

I was able to figure out LOI with that, but I seem to have a hard time understanding the RTCC documentation for some reason.

Yeah a lot of it is shorthand and it needs to be updated/revised for sure.

I’ve actually never calculated DOI with RTCC, by the time I got there in 12, MCC support was implemented.

Oh haha, I didnt think about that. It should be TAR->LDP with MOD being LM Maneuver Sequence and SEQ DOI. TH1 should be the threshold before your desired DOI time.

 

[Max-Q]

Oh haha, I didnt think about that. It should be TAR->LDP with MOD being LM Maneuver Sequence and SEQ DOI. TH1 should be the threshold before your desired DOI time.

So like the nearest hour before flightplan DOI time?
Just leave TH2, 3, and 4 alone?

 

[rcflyinghokie]

So like the nearest hour before flightplan DOI time?
Just leave TH2, 3, and 4 alone?

Yeah hour before DOI time. It should find the correct time in the orbit.

I am 99% sure you dont need a TH2 for DOI here, if one did go there it would likely be landing time but I dont think it plays into the calculation. Let me double check that.

EDIT: TH1 alone should suffice

 

[Max-Q]

One other thing i missed in the first post, at 82:20:20, there is a “Bailout Burn” scheduled if required. I assume this is for if for some reason the CSM couldn’t stay in the 60 by 7 orbit and I can just skip it?

 

[rcflyinghokie]

One other thing i missed in the first post, at 82:20:20, there is a “Bailout Burn” scheduled if required. I assume this is for if for some reason the CSM couldn’t stay in the 60 by 7 orbit and I can just skip it?

Yeah the bailout burn is if there was an overburn or something causing the DOI orbit to be dangerous, basically its a quick about face to raise perilune in an emergency. Since this was the first CSM/LM stack DOI planned, they added this for safety.

 

[Max-Q]

I'm on the surface successfully, less than 10 meters from Apollo 14's historical landing site.
So, looking ahead at the flightplan again, here is RTCC Questions Mega-Post #2:
I did look at the manual, but I couldn't figure these out:

• RLS - Mentioned a lot; do I need it?
• PC-1 - How to calculate
• At 134:30: CSM S.V. (L/O) - How is this different from a regular SV?
• Also at 134:30: Uplink To LM ZERO POS/NEG CELLS - I assume I can just skip this, but what is it?
• Liftoff PAD - How to calculate
• CSI PAD - How to calculate
• LM Deorbit burn - How to calculate, uplink P99, etc.

Thanks and sorry for the many questions!

 

[rcflyinghokie]

Thanks and sorry for the many questions!

First and foremost don't be sorry!

RLS - Mentioned a lot; do I need it?

Yes you do! This basically tells your LGC/AGS where you are so it can successfully integrate a state vector at liftoff. You will want to uplink this with your known landing site coordinates as well as enter it into the AGS (231)

PC-1 - How to calculate

TAR->LDP with MOD being CSM Prelaunch Plane Change

At 134:30: CSM S.V. (L/O) - How is this different from a regular SV?

This means the SV is time tagged, in other words its the state vector at liftoff time.

Also at 134:30: Uplink To LM ZERO POS/NEG CELLS - I assume I can just skip this, but what is it?

We actually havent quite figured out what this is either, so needless to say you can skip it haha.

Liftoff PAD - How to calculate

RTCC input guide has the steps for a concentric liftoff. You will need to use those processors before computing a pad.

CSI PAD - How to calculate

Same as above.

LM Deorbit burn - How to calculate, uplink P99, etc.

The easiest way I have found short of multiple iterating and checking ground coordinates is to enter the values expected from the mission into the maneuver pad page and iterate the TIG until values like attitude line up.

P99 is just an uplink from RTCC. UTI->EMP, and there are 4 uplinks (0-3) you simply uplink 0, then 1, then 2, then 3. Also follow the procedures I linked you for running it.

 

[Max-Q]

RTCC input guide has the steps for a concentric liftoff. You will need to use those processors before computing a pad.

I found the instructions for getting the PAD and calculating the ascent, I guess my question is more how to target the ascent.
It asks for stuff like exact Ascent TIG, TIG of TPI, and so on. Where do I get these?

 

[rcflyinghokie]

I found the instructions for getting the PAD and calculating the ascent, I guess my question is more how to target the ascent.
It asks for stuff like exact Ascent TIG, TIG of TPI, and so on. Where do I get these?

All of this is using the lunar launch window processer (LLWP)

From the RTCC guide:

T3, ASCENT (Concentric) TPI Times: Apollo 14 & earlier: Sunrise-23min, Apollo 15+: Sunrise-16min

• TAR, LLW, INI, TAR, VLH: +5535.6, VLV: +32.0 - TAR, LLW, THT: Desired TPI Time, CSI: 50
• CLC solution - TAR, ASC, LTO: Desired LLW sol. GET, CLC - Go back to LLW and CLC again

 

[Max-Q]

I think I got the ascent figured out; I now know my ascent time and TPI time, but the CSI stuff is still giving me trouble.
After exactly following the button and input sequence in the manual I can't seem to get CSI to calculate. I am really lost here, can you offer more detail than is in the manual?

 

[indy91]

You are doing the calculation in the LM and have selected the CSM as the target vessel, right?

 

[Max-Q]

Yep, in the LM targeting the CSM.
I did manage to calculate a valid ascent solution, so if needed I can just use the CSI & TPI times from the LLWP display for P32, but I really wanted to get the CSI PAD.

 

[rcflyinghokie]

Yep, in the LM targeting the CSM.
I did manage to calculate a valid ascent solution, so if needed I can just use the CSI & TPI times from the LLWP display for P32, but I really wanted to get the CSI PAD.

You have everything you need in there for the CSI pad. Is there something you are missing?

 

[Max-Q]

I was trying to get this screen to calculate:

I have the times from here:

The dVs look super high, is this because I'm practicing this calculation at 124:00 MET and it's too far in the future for a good solution?
Also, I'm a bit suspicious of my PC-1 burn. The dV came out to about 114 fps, much lower than in the flightplan; however the groundtrack looks corrent to pass over the landing site at liftoff time.

 

[rcflyinghokie]

Mind sharing shots of your ascent calculations in the LLWP and such?

Also the processors you are using (SPQ) need the MPT active.

 

[Max-Q]

TPI time:

LLWP:

Ascent Processer:

CSI Processor

 

[rcflyinghokie]

The CSI processor needs the MPT, so thats why you are getting no data on it.

I could take a look at a scn and see what I get computation wise.