Apollo 15: Lunar Ascent Preparation and RTCC Procedures?

[Wedge313]

OK I'll try that. At some point the light will come on for me, but right now I'm groping in the dark. Thanks again.

 

[rcflyinghokie]

OK I'll try that. At some point the light will come on for me, but right now I'm groping in the dark. Thanks again.

Yeah I had my hand held with RTCC flying 12-17 one after the other, so that's how I picked up a lot of this

 

[Wedge313]

Yeah, I'm messing something up. Ran through the whole process again. Made the MPT inactive, went back to the Ascent and recalculated, and still no joy on the DEDA inputs.

There's probably some basic step that might be really obvious to you but that I'm leaving out here.

 

[rcflyinghokie]

Yeah, I'm messing something up. Ran through the whole process again. Made the MPT inactive, went back to the Ascent and recalculated, and still no joy on the DEDA inputs.

There's probably some basic step that might be really obvious to you but that I'm leaving out here.

Did you recompute the RLS? Also I see you have the target set as the LM, you need to target the CM.

 

[Wedge313]

Did you recompute the RLS? Also I see you have the target set as the LM, you need to target the CM.

I did re-compute the RLS a while back, before I generated the L/O orient REFSMMAT, but not after I made the MPT inactive. Would that matter?

Also, I tried generating the Ascent PAD with the CM as the target, then the LM as a target, back and forth a few times, trying different things to see if I could stumble on my mistake.

Question: As I go over all of this, repeating the process, when I pull up the lunar launch targeting table I noticed my TGT button has no effect, I know the first time through I had to select CSM as the target but subsequently the TGT is not showing up. Does this indicate something I'm doing wrong?

I think what I might try is deleting this whole scenario from the MPT, I know I saw a button on one of these pages that deletes the maneuver, and start the whole thing over from scratch, see if I get better luck.

 

[rcflyinghokie]

I did re-compute the RLS a while back, before I generated the L/O orient REFSMMAT, but not after I made the MPT inactive. Would that matter?

It shouldn't matter, it should still be stored there but it doesn't hurt to check

Question: As I go over all of this, repeating the process, when I pull up the lunar launch targeting table I noticed my TGT button has no effect, I know the first time through I had to select CSM as the target but subsequently the TGT is not showing up. Does this indicate something I'm doing wrong?

I believe it doesn't matter if the MPT is active, but I need to jump in and double check.

I think what I might try is deleting this whole scenario from the MPT, I know I saw a button on one of these pages that deletes the maneuver, and start the whole thing over from scratch, see if I get better luck.

Yeah without seeing it I don't know if something got messed up. Would you mind posting a scn file I can check for issues or bugs.

Also just setting the MPT to inactive should let you compute the ascent with no issues.

 

[Wedge313]

Here's a .scn.

I tried unsuccessfully to delete the ascent from the MPT, the DEL function had a format I was unable to decipher.

 

[rcflyinghokie]

I was able to compute your liftoff with and without MPT. The target button in the LLT wont function if you are using MPT.

For the Ascent PAD, you should be using the CSM as target. Also it looks like you didn't burn enough plane change, so you still have a crossrange component. I just computed a plane change you still have about 19fps to go to center your orbit. Now the LM can make this crossrange, but I think something went off with your PC burn.

And to delete on MPT, Its M62, Table (CSM/LEM), Maneuver number (which number on the list it is from the top), and then D (or DH if the maneuver is in the past)

So to delete your ascent, you would use (M62,LEM,1,D).

 

[Wedge313]

Obviously I'm going to go back and re-do the plane change.

I was able to compute your liftoff with and without MPT. The target button in the LLT wont function if you are using MPT.

When you say "compute your lift off" do you mean you got the ascent PAD to generate correctly?

And I'm obviously not getting the relation between the MPT and the LLT or ACT functions, I thought they all were inter-related. But I have to turn off the MPT to get the LLT to work correctly?

Well, let me figure out where I went wrong on the plane change. Then I'll get back to banging my head against the wall with the RTCC.

Thanks again.

 

[rcflyinghokie]

When you say "compute your lift off" do you mean you got the ascent PAD to generate correctly?

Yes, I computed the liftoff using the LLT and ascent processors then went to the ascent pad with the CM as target and it computed for me.

And I'm obviously not getting the relation between the MPT and the LLT or ACT functions, I thought they all were inter-related. But I have to turn off the MPT to get the LLT to work correctly?

So they are apples and oranges. The MPT is basically a way to "save" maneuvers and use them to calculate later maneuvers based on a new trajectory. With the MPT inactive, all of the processors rely on your current trajectory. The processors work regardless, but MPT active or inactive just determines where the results end up. It should work fine with MPT active or inactive, as you saw because you have a good ascent on your MPT.

Obviously I'm going to go back and re-do the plane change.

What parameters did you use when computing it? It's close but not quite there.

I hope that clarifies things? Also, I might have mentioned this, but feel free to pop on discord as well, streaming this stuff and getting real time help can go a long way in generating "eureka" moments!

 

[Wedge313]

Looking over my notes and reviewing your inputs on this topic I'd guess I botched something up when I calculated that PC burn. 19 fps error is a lot. I thought the burn itself went well, even without the auto-ullage....which doesn't exist . I nulled out all the residuals. So it's either I calculated the burn wrong, updated the landing site wrong, or got the P40 orientation wrong. I'll get on it again tomorrow morning, make the coffee a little stronger.

It will all be better once I'm sufficiently caffeinated.

 

[rcflyinghokie]

Looking over my notes and reviewing your inputs on this topic I'd guess I botched something up when I calculated that PC burn. 19 fps error is a lot. I thought the burn itself went well, even without the auto-ullage....which doesn't exist . I nulled out all the residuals. So it's either I calculated the burn wrong, updated the landing site wrong, or got the P40 orientation wrong. I'll get on it again tomorrow morning, make the coffee a little stronger.

It will all be better once I'm sufficiently caffeinated.

My guess is you just had an incorrect liftoff time or landing site. Easy fix!

 

[Wedge313]

Before I went back to correct the PC burn, I spent about an hour trying to get the ascent PAD. I'm totally lost on this. I think I've got the calculations with LLT and ACT complete, but I can't get a PAD from that. I've made sure the CSM (Endeavour) is the target. I've made sure the MPT is inactive. I deleted the maneuver on the MPT. I re-did the maneuver on the MPT. No matter what I've tried I can't get a complete PAD with the DEDA inputs.

Let's make sure I'm on the right page. I've got the LLT and ACT parts done. I made sure the MPT is inactive. From the RTCC main page I select PAD (Pre-Advisory Data), then ASC (LM Ascent PAD). Endeavour is the target. I hit CLC. And then nothing. There are no entries for Crossrange or any DEDA.

What magic buttons are you pushing, and why can't I find them?

 

[Wedge313]

PC remedial burn complete. This looks OK on the MAP MFD, but besides the cross range info on the Lunar Ascent PAD (which I haven't figured out how to generate yet) can I check this some other way?

I'll proceed to calculate the ascent again. Maybe I'll accidently do it correctly.

 

[rcflyinghokie]

Before I went back to correct the PC burn, I spent about an hour trying to get the ascent PAD. I'm totally lost on this. I think I've got the calculations with LLT and ACT complete, but I can't get a PAD from that. I've made sure the CSM (Endeavour) is the target. I've made sure the MPT is inactive. I deleted the maneuver on the MPT. I re-did the maneuver on the MPT. No matter what I've tried I can't get a complete PAD with the DEDA inputs.

Let's make sure I'm on the right page. I've got the LLT and ACT parts done. I made sure the MPT is inactive. From the RTCC main page I select PAD (Pre-Advisory Data), then ASC (LM Ascent PAD). Endeavour is the target. I hit CLC. And then nothing. There are no entries for Crossrange or any DEDA.

What magic buttons are you pushing, and why can't I find them?

May seem like a silly question but are you doing all of this from the LM?


In the scn you sent me, here are my steps (with MPT inactive):

TAR->LLT->TGT->Select CSM (Endeavour)

TTH->Input the approximate liftoff time rounded down to the nearest hour (171:00:00)

Verify RDO=32 and DT=45 (For Apollo 15)

CLC->Should now compute the preliminary data

TAR->ASC->CLC->Should compute liftoff time

TAR->LLT->CLC

TAR->ASC->CLC

PAD->ASC->TGT->Verify Endeavour->CLC->Should display the ascent pad


In the scn you sent me, here are my steps (with MPT active, maneuvers deleted first, table reinitialized and new vectors updated, and PC burn complete):

Starting fresh I deleted the old maneuver off the MPT with: PLN->DEL->(M62,LEM,1,D)

Reinitialize the tables and vectors as I explained previously

TAR->LLT->TTH->Input the approximate liftoff time rounded down to the nearest hour (171:00:00)

TAR->LLT->VTI->Input the vector time you intend to use (I have rounded down to the nearest hour (171:00:00))

Verify RDO=32 and DT=45 (For Apollo 15)

CLC->Should now compute the preliminary data

TAR->ASC->CLC->Should compute liftoff time

TAR->LLT->Check your TPI time here (bottom right says TPI) and then adjust DT to make it the TPI time you computed. DT is in minutes so you can use decimal minutes to get it close

TAR->LLT->CLC

TAR->ASC->CLC

TAR->ASC->MPT->Puts it on the MPT

Remember doing the MPT computation will not give you an updated PAD, so what I recommend is doing it all in MPT first so you can get your tweak burn data ready, and then making MPT inactive, computing it again and then getting your pad or visa versa.

 

[Wedge313]

May seem like a silly question but are you doing all of this from the LM?

In my situation there are no silly questions. I have been doing this from the CSM. My reasoning was that during this period Dave and Jim are EVA and the LM is powered down. I had to be in the CSM for the plane change, so I just pressed on with the ascent planning while I was there. Should I be in the LM doing this?

And it further exposes my RTCC ignorance because I don't know why it would matter.

Thanks for the very explicit walk through! At first glance nothing jumps out at me as the missing step, but I'll go through it and see if I find my error.

Sorry to occupy so much of your time, but thanks again.

 

[rcflyinghokie]

In my situation there are no silly questions. I have been doing this from the CSM. My reasoning was that during this period Dave and Jim are EVA and the LM is powered down. I had to be in the CSM for the plane change, so I just pressed on with the ascent planning while I was there. Should I be in the LM doing this?

And it further exposes my RTCC ignorance because I don't know why it would matter.

Haha yeah RTCC is vessel dependent in many cases, think about not doing this in a vehicle but rather doing this on earth for a specific vehicle if that helps internalize it.

Good rule of thumb with our implementation, if you intend to compute a maneuver, use the RTCC while in that vessel. So in your case, you should be in the LM to compute that ascent on RTCC.

Sorry to occupy so much of your time, but thanks again.

Not a problem at all! Again, I was in your shoes not too long ago so its nice to be able to pass on what I have scrapped together in RTCC knowledge!

 

[Wedge313]

So I should have been in the LM doing this the whole time?

Funny, I've pictured the RTCC as being synonymous with Mission Control, and someone who looks like Ed Harris in "Apollo 13" is busy cranking out all this information and sending it up to both the CSM and the LM.

I'll try it right now from the LM.

 

[Wedge313]

Success! You know, I'm glad it was something as stupid as being in the LM vs the CSM. You gave very clear, easy to follow instructions and it was driving me nuts trying to figure out what I was doing wrong.

Thanks for hanging in there.

 

[rcflyinghokie]

Success! You know, I'm glad it was something as stupid as being in the LM vs the CSM. You gave very clear, easy to follow instructions and it was driving me nuts trying to figure out what I was doing wrong.

Thanks for hanging in there.

Not a problem! Also it looks like you reburned your plane change? I see a very tiny crossrange