NASSP AGC incorrect TLI Any Help?

[polaris149Tiberius]

Hello all,

I have found that the AGC in NASSP doesnt do the TLI the way the instruction set says to do it. I have tried it several times and it seems to not be able to take the time amount the way it mentions in these instructions in "Flying Saturn V.pdf":

"Performing an automated TLI burn
To perform the TLI burn, you need to run program 15. So, start with VERB 37 NOUN 15 ENTER to begin running that program.​

Now use your favorite MFD to calculate the burn ejection time and delta-V. I've used the Transfer MFD, but this should work with TransX too.​

The computer will respond with a flashing VERB 06 NOUN 33. This displays
the time to ejection in hours (top line), minutes (middle line) and hundredths of seconds (bottom line).​

Skip time until the time to ejection in the MFD display is around 1300
seconds. Now enter VERB 22 ENTER to change the value of the minutes
field. Press '+00020' to indicate twenty minutes, and wait. Watch the time to ejection count down and when it hits 1200 seconds, press PROG to update the time for the computer. ​

You've now told the program when to make the TLI burn. The display will
switch to VERB 06 NOUN 14. This is one line, the delta-V for the burn.​

Press VERB 21 ENTER to update the delta V. Now press '+' and enter the
value with appropriate leading zeros. For example, if your burn delta-V is
going to be 3183 m/s, enter '+03183'. When you're done, press PROG.​

The computer will perform some calculations and respond with a flashing
VERB 06 NOUN 95. This shows the burn details. The top line is the time to
engine ignition, the middle line the delta-V, and the bottom line the velocity for engine cutoff. The time to ignition will not be the value you just entered, as it allows for the burn duration and engine startup.​

Now you can sit and wait, or skip time towards ignition. If you want a
countdown, then press VERB 16 ENTER to monitor the burn values.​

Along the way a few things will happen to keep you awake. About nine and a half minutes before ignition the UPLINK ACTY light will come on for a few seconds. About 1 minute and 45 seconds to ignition the display will blank briefly, then switch into countdown mode with VERB 16 NOUN 95.​

About 1 minute and 30 seconds to ignition the computer will enable prograde mode, if it's not already enabled: it will then keep it active throughout the burn and turn it off at the end. At this point, if you forgot to set the RCS pitch and yaw switches for the SIVB you'll suddenly realise... luckily you have a few seconds to hit them and still be ready for the burn. ​

If you change your mind before ignition, then press VERB 34 ENTER to
terminate the current program. If entered after ignition this will shut down the SIVB, but you will have used up your single restart.​

After the engines ignite, the display will change. Although it's still NOUN 95, it will now show an approximate countdown to engine shutoff in the top line, the remaining delta-V in the middle, and the cutoff velocity in the bottom line. If you want to monitor the state of your orbit, you can use VERB 16 NOUN 44 to display apogee, perigee and current altitude.​

One thing you will notice is that the cutoff velocity in the NOUN 95 display
will change during the burn. As the engine runs, you begin to climb away from Earth, and as a result you lose velocity. On a real Saturn V NASA would have calculated the cutoff velocity taking that loss into account, but the MFDs don't do so, therefore the computer performs the calculations in realtime as the engine runs.​

When the engine cuts off, you should be within about 1 m/s of the correct
velocity. If you're further out you can probably fine-tune with the SM RCS
once you've seperated the LM from the SIVB.​

The countdown on the DSKY will stop at zero, so press PROG. That will give you a flashing VERB 37 to remind you to change programs, at this point you might as well enter NOUN 00 ENTER to switch the AGC to idle, or NOUN 06 ENTER and then PROG to put it in standby mode."​

When getting to the part that I enter the 20 minutes and then get to 1200s I press PROG as the instructions say to do. However the display shows 16 50 and when I set it to show the count down its earlier than IMFD shows the TEj to be. I even convert IMFD's TEj to minutes and the AGC's burn is around 4 minutes early. Even though it says:
"The time to ignition will not be the value you just entered, as it allows for the burn duration and engine startup."
...it still burns way too early and ends up putting me near the moon but not a free-return. My dV shows correct, but I noticed the AGC only points in the retrograde direction. IMFD Burn Vectoring shows a different "Off-Axis" burn vector. At the end of the burn map MFD shows a vector toward the moon, but not a free-return. Im lost on what to do. I really wanted to use the AGC to do this burn.
​

Does anyone know what is wrong with the AGC here?
Are there any NASSP developers that read these forums that can help?
Am I doing something wrong?​

Thanks in advance.​

 

[Moonwalker]

Please report NASSP related bugs and errors in the development forum:

http://www.ibiblio.org/mscorbit/mscforum/

Also in this case, the Flying Saturn V.pdf doesn't correspond to the current version of Project Apollo - NASSP. It's rather, rather old. If you use the current version of Project Apollo - NASSP just use the documents contained in the 'Check List' Folder.

 

[polaris149Tiberius]

Good Answer

Good Answer

Thanks for the reply. A very good and definitive answer with a quick fix. Thanks. Will use the correct docs. It should be noted that those legacy documents should be deleted or put into a legacy folder to make it more clear to users to NOT use them. Or I should say it would be nice if they were.

Thanks again

 

[Moonwalker]

I'm rather sure for the first release which will be Apollo 7 old files won't be included

 

[Tschachim]

Yeah, we really need to clean up the documentation before the Project Apollo - NASSP 7 release.

In order to answer the original question, the "Simple AGC" P15 does a "prograde only" burn, which isn't realistic and - depending on the mission - results in a very unprecise trajectory or isn't working at all.

In reality the AGC can't do the TLI burn (P15 is just a monitor program with a backup cutoff feature, it wasn't even present in the early missions / Colossus versions), but it was done by the S-IVB itself and that's the way it works in Project Apollo - NASSP 7:

Basically you calculate the burn in IMFD, then transfer the burn data with the Project Apollo MFD to the S-IVB, which then executes the burn automatically.

Look here for more informations: http://www.ibiblio.org/mscorbit/mscforum/index.php?topic=1431.0

Cheers
Tschachim

 

[Quick_Nick]

4 minutes earlier sounds like it may be about right actually. IMFD gives you a time for an instant burn(all dV added in an instant). The AGC calculates a time to begin the burn so that the time in IMFD is very close to the middle of your burn. If you began your burn at the Ejection Time IMFD gives you, you would have an inaccurate burn. Ejection burns can be pretty complicated. First of all, you have to have to burn equal amounts on each side of the TEj if you maintain the same amount of acceleration throughout the burn, BUT since you are losing mass your acceleration will increase(assuming you don't throttle down) and you must then take this into account. Luckily the AGC in NASSP calculates all of this for you(so long as you enter the right time and dV) and gives the most accurate ejection possible.
I'll also reinforce the idea that the AGC is for prograde burns.(the only reasonable burn to get to the moon)

Be sure to read this tutorial. It explains a lot:
http://orbithangar.com/searchid.php?ID=462

 

[polaris149Tiberius]

4 minutes earlier sounds like it may be about right actually. IMFD gives you a time for an instant burn(all dV added in an instant). The AGC calculates a time to begin the burn so that the time in IMFD is very close to the middle of your burn. If you began your burn at the Ejection Time IMFD gives you, you would have an inaccurate burn. Ejection burns can be pretty complicated. First of all, you have to have to burn equal amounts on each side of the TEj if you maintain the same amount of acceleration throughout the burn, BUT since you are losing mass your acceleration will increase(assuming you don't throttle down) and you must then take this into account. Luckily the AGC in NASSP calculates all of this for you(so long as you enter the right time and dV) and gives the most accurate ejection possible.
I'll also reinforce the idea that the AGC is for prograde burns.(the only reasonable burn to get to the moon)

Be sure to read this tutorial. It explains a lot:
http://orbithangar.com/searchid.php?ID=462

Ya actually no it doesn't work. You can try it and see if you can get to the moon with the current burn. Its just a wrong burn.

In order to answer the original question, the "Simple AGC" P15 does a "prograde only" burn, which isn't realistic and - depending on the mission - results in a very unprecise trajectory or isn't working at all.

As you can see even Tschachim knows about it. I have tested the Apollo 11 flight scenario .../Project Apollo -NASSP/AS-506 Apollo 11 Launch.scn from Launch to landing at the moon using outside MFDs so that works but I am really interested in seeing the AGC work to get Apollo 11 to the moon and land. That would be GREAT!!

I also wanted to believe that it knew what it was doing by burning a bit earlier but no. In the end, the burn just wasnt correct. First of all, its burning prograde to your current plane and not to the moon's plane.
This doesnt quite take you on the moon's plane -unless you do a costly align plane burn before going. At the suggested azimuth during launch, your still off-plane enough to not get to the moon if you burn prograde.
Also, the burn comes too early and stops too early. It took my dV from an off-plane IMFD calculation and gave me a much too fast velocity. The intercept line showing in IMFD map was a straight line down the center toward the moon, but was too low for me to capture.

I entered the correct time and dV but no. It just gets it wrong. Try it you will see.

 

[Quick_Nick]

Ya but no. Its just a wrong burn. I also wanted to think that it knew what it was doing but no. In the end, the burn just wasnt correct.
I did enter the correct time and dV but no. It just gets it wrong.

Well can you give some more details? Like what IMFD says before the ejection of what the trajectory should be and what it shows the acutal trajectory as after the burn. Basically tell things such as Pe MJD, PeA, Inc, etc. (these are TransX things but should exist somewhere in IMFD)

And, now that I think about it, can you give us a scenario file with IMFD setup and the spacecraft in orbit?

 

[polaris149Tiberius]

Woops!

Woops!

You replied so fast to my responce. Guess thats why you have the name Quick Nick. If you notice a developer has stated that the program doesnt work. I know what Im doing on IMFD (I write tutorials for it) so I dont think in this case the problem is pilot error. A developer states above that the program is inaccurate.

Have you been able to make it work Nick?

Basically you calculate the burn in IMFD, then transfer the burn data with the Project Apollo MFD to the S-IVB, which then executes the burn automatically.

Look here for more informations: http://www.ibiblio.org/mscorbit/mscf...p?topic=1431.0

Thanks for this I will check it out. It should be noted though that when trying to use the Project Apollo MFD with the NASSP AS-506 Apollo 11 Launch scenario, it comes up saying "This vessel is not supported with this MFD" or something like that. Of course I am using the beta. I will look into the information. Thanks.

 

[Quick_Nick]

Woops!

You replied so fast to my responce. Guess thats why you have the name Quick Nick. If you notice a developer has stated that the program doesnt work. I know what Im doing on IMFD (I write tutorials for it) so I dont think in this case the problem is pilot error. A developer states above that the program is inaccurate.

Ah, good to know. (sort of)

Have you been able to make it work Nick?

I've never used IMFD for various reasons but I will try it if I can get it to work.(Many times it's caused CTDs for no apparent reason) I normally use TransX and have had no issues with it.

 

[Tschachim]

It should be noted though that when trying to use the Project Apollo MFD with the NASSP AS-506 Apollo 11 Launch scenario, it comes up saying "This vessel is not supported with this MFD" or something like that. Of course I am using the beta.

The beta doesn't include a scenario named "AS-506 Apollo 11 Launch", so I assume you have a mixed installation and this scenario loads the 6.4.3 Saturn/CSM, which isn't supported by the MFD.

Cheers
Tschachim

 

[polaris149Tiberius]

Can you tell me what I am supposed to have?

Can you tell me what I am supposed to have installed.

I have been to the SourceForge.net site for your project and installed these files in this order:

1. Orbiter 2006 P1

2. CRAW-SAT-V.zip
3. VirtualApollo_1.1.zip

4. ProjectApollo_6.4.0.zip

5. ProjectApollo_Patch_6.4.3.zip

6. NEP_050223.zip

7. NEP_Apollo11Patch.zip
8. ProjectApollo_Meshland_20060717.zip
9. ProjectApollo_CVS_20080527.zip
10. ProjectApollo_Beta_20080617.zip

According to the main Project Apollo -NASSP sourceForge page for download, There are basically 5 categories to get:

Beta Releases 20080617
NASSP Enhansment Pack (NEP) 050223
Project Apollo-NASSP 6.4.3
Videos & Multimedia Project Apollo -NASSP 7
Virtual Apollo 1.1

I thought since all these files are listed as "latest" at sourceForge that I should install all of them.
Maybe you can clarify which files we need and which ones we dont.

Is there a document giving simple installation information on how to install ONLY the latest versions of Project Apollo-NASSP available somewhere? The Readmefirst.txt offers no installation notes.
I guess I will start from a scratch install of Orbiter and install only the addons that I am supposed to.


Thanks in advance

 

[pattersoncr]

Go here:
http://nassp.sourceforge.net/wiki/Main_Page
and follow the directions under Getting Started.

 

[Tschachim]

http://nassp.sf.net/wiki/Installation

EDIT: Damn, Chuck was too fast for me...

 

[polaris149Tiberius]

http://nassp.sf.net/wiki/Installation

EDIT: Damn, Chuck was too fast for me...

I appreciate the link. Just reading the first few paragraphs I see that this installation page states this:

"This section tries to provide step-by-step instructions to set up the "beta testing enviroment" for Project Apollo."

Im not really interested in beta testing at the moment. Is there a difinitive install document for the stable release?

This looks to be an installation page for beta testing and not for regular stable release installation.

edit: Wait I think I have found it. Is this it? Project Apollo 6.4 FAQ. ??


By the way, thanks for all the help here guys. I and Im sure the forums readers much appreciate the clarification of your addon. I certainly do.

 

[Tschachim]

This looks to be an installation page for beta testing and not for regular stable release installation.
edit: Wait I think I have found it. Is this it? Project Apollo 6.4 FAQ. ??

Correct, but you also wrote:

... Of course I am using the beta ...

which is a little bit contradictory, isn't it?

Cheers
Tschachim

 

[polaris149Tiberius]

Well now that things are a bit clearer to me as to what is Beta and what is stable release, I have reciently decided to go with the stable release now. I just want whatever works the best.
I think you clarified for me that I indeed was using an older version scenario when I thought I was using the beta files only. So this is the reason for the "contradictory" information. Not a contradiction just an education. You pointed that out to me. So I dont think Im contradicting myself, I think your educating me as to which scenario file I was using.

Again thanks for the help.