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Virtual AGC
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dseagrav



Joined: 03 Dec 2005
Posts: 216

PostPosted: Thu Apr 27, 2006 6:37 am    Post subject: Reply with quote

Because I'm an optimist.
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chode



Joined: 31 Jan 2005
Posts: 123

PostPosted: Thu Apr 27, 2006 6:44 am    Post subject: Reply with quote

Good enough!
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dseagrav



Joined: 03 Dec 2005
Posts: 216

PostPosted: Thu Apr 27, 2006 6:56 am    Post subject: Reply with quote

Anywho, all joking aside, if you really want to help with the vAGC, I highly suggest at least basic familiarity with assembly language. Most of the big problems are not with getting it to run but figuring out what exactly to do to make it perform useful work; This involves a lot of digging around in the Colossus / Luminary source code and a lot of research. Basically, it's computer archaeology, with the bonus that when it works, it neatly debunks the conspiracy theories alluded to in problem #5 (About which I was kidding, BTW). The first two problems are the big showstoppers. The second and third are minor annoyances as far as I'm concerned. The fifth was a joke. It's coming up on 0200 here and I was in traffic court today so I'm a little bit wierder than normal right now. (BTW You keep odd hours - Where are you located?)
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Tschachim



Joined: 26 Nov 2004
Posts: 1272

PostPosted: Thu Apr 27, 2006 9:38 am    Post subject: Reply with quote

chode wrote:
Should I continue developments on the AGC in C++, or might my time be put to better use in contributing where I can to the vAGC development?

Good question!
As dseagrav said the VAGC has several problems (especially the hoax problem Wink), so we'll still need the AGC++ and a CSM reentry autopilot would be very cool. A working EMS would be fantastic...

But of course working on the VAGC would be great, too, it looks like that the reentry controlled by the VAGC is still improvable.

Looks like it depends on what is more challenging and makes more fun for you! Smile

Thanks irnenginer for the document, I'll have a look at it. Full link is:
"Deorbit and entry crew training simulations for near-earth orbital missions"
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740072934_1974072934.pdf

Cheers
Tschachim
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Christophe



Joined: 09 Feb 2005
Posts: 280
Location: France

PostPosted: Thu Apr 27, 2006 2:39 pm    Post subject: Reply with quote

Tschachim wrote:
Hi Christophe,

that's interesting, but I don't get that alarm. I launch to orbit, go to P00, do V41N20E and enter +01000E +00000E +00000E. NO ATT goes on and the IMU/FDAI drives to (10, 0, 0). If I enter V40E I get an operation error, if I do it correctly (GSOP) and enter V40N20E, the IMU is set to (0,0,0) as intended, no error.

Cheers
Tschachim


I've found what I was doing wrong as soon as I've posted the message(as usual Wink )
In fact it's normal to get the NO ATT lt on during V40N20. To turn the NO ATT off you have to do the gyro torquing with V42. The purpose is to fine tune the IMU align by nulling the residual error.

That's what happens when I go too fast Embarassed

AS far as the 375 code alarm is concerned I get it sometimes while playing with the DSKY but I still have no clue why?
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Christophe



Joined: 09 Feb 2005
Posts: 280
Location: France

PostPosted: Thu Apr 27, 2006 3:02 pm    Post subject: Reply with quote

I've just read the dseagrav's post about people who are waiting for a "video game" kind of apollo sim. It's very interesting and I do agree with what you said.
I just want to reply: we don't care about those people. Of course if people don't want to bother with doc and checks and want just to push a magical MFD button to get around the moon, something exits for us: it's called AMSO.
I don't want to offense the author of this simulator since I still remember that the first time I saw the Apollo craft in orbiter, it was with AMSO. It's a great orbiter add-on, perfectly right for the orbiter community who just want to play one day with delta glider and an other day with the lunar module.
I think that today ProjectApollo has reached a point it could not be viewed like an orbiter add-on anymore. Orbiter is just the necessary environment to install the simulation. Day after day, we use orbiter features less and less.

My vote is for the vAGC. 100%
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movieman



Joined: 25 Nov 2004
Posts: 1018

PostPosted: Thu Apr 27, 2006 3:05 pm    Post subject: Reply with quote

375 is undocumented and there's no reference to it as an error that I can find in the code.

Of course it could be a bug Smile.
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Swatch



Joined: 15 Feb 2006
Posts: 262
Location: Cincinnati, Ohio

PostPosted: Thu Apr 27, 2006 6:32 pm    Post subject: Reply with quote

I want to weigh in on the fact that it would be nice to have an AGC++ Apollo on the level of 6.4 with some of the NASSP 7 features implemented.

I agreee, Project Apollo 'feels' like it has expanded beyond a simple orbiter add-on, but this is why I think Realism is such a great idea. AMSO, as nice as it is, is very basic...which is great for the "lets hit the red flashy button!" type of sim pilot. If you focus PA on vAGC, you'll end up with the exact opposite end of the spectrum. Now if you implement a Realism scale and start it (REALISM 0) where NASSP 6.4 left off, then someone can work their way up to max realism slowly. As Tschachim pointed out though, vAGC isn't very condusive to REALISM 0. This is why the AGC++ is so nice, and the key is reconciling the differences between AGC++ and vAGC, so the result is an almost imperceptable blend up the REALISM scale.

We don't need to implement EVERYTHING in AGC++, but basic controls, navigation and overall systems management is nice. We don't necessarly need the extroadinarly accurate re-entry either, just a proper simulation of the steps one would go through to get an accurate reentry from the vAGC.

As far as the problems with saving the vAGC is concearned, it poses quite the problem. Hopefully this can be worked out or at least better understood so that it can be avoided for the time being. And the catch of no time acceleration above 10 just means that the saving issue is made more important Razz .

Anywho, that's my two cents....I wish you luck if you decide to pursue vAGC work, but it would be really nice to have the EMS working as a seperate entity so that it can do it's thing independent of vAGC and AGC++. [/hint hint Wink ]
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dseagrav



Joined: 03 Dec 2005
Posts: 216

PostPosted: Thu Apr 27, 2006 6:45 pm    Post subject: Reply with quote

The EMS really *IS* independent of the computer. The only involvement the computer has with the EMS setup is that the computer generates a list of numbers that must be entered by the crew into the EMS to initialize it prior to re-entry. There are no data connections between the two.
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Tschachim



Joined: 26 Nov 2004
Posts: 1272

PostPosted: Thu Apr 27, 2006 9:04 pm    Post subject: Reply with quote

Well, despite the fact I love the VAGC, I do care about the "video game" people mainly just to reach a bigger audience, or to quote LazyD again: "... to have a no-brainer version to help newbies become addicted." Smile

So I also would like to keep the AGC++, not only but also the AGC++ already can do a lot of stuff, especially the LM descent and ascent is great (... or will be great when the RCS is back... Wink). The only thing we really need the AGC++ cannot do is CSM reentry, so if Chode would do the AGC++ reentry the AGC++ would be quite complete (assuming you do MCCs the "Orbiter way", but if LazyD really is doing his TLI stuff, it looks like the CSM will fly to the moon and back unattended Smile) and a good alternative to the "hardcore" VAGC.

I know AMSO and I understand Alain's "keep it short and simple" concept, but I also think that's no reason to drop the "quickstart mode" nor the AGC++. Additionally to the usage there are a lot of more differences between NASSP and AMSO (Panels, Meshes, Swatch's upcoming VC, the KSC scenary, autopilots...). For example I know from the Orbiter forum that some people complain that AMSO has no panel, even if they don't want to use it like the real thing.

Movieman did a great job to "unify" the interface between the 2 AGC implementations and the rest of the spacecraft, so I just don't see a reason to drop the AGC++ support. To continue with the "quickstart mode" concept isn't very difficult, too, we'll do a better "checklist system" that Movieman already began and after that's we just have to look after the (textfile) checklists, that's all...

By the way, because of the time acceleration problem of the VAGC: I was thinking about to use the standby mode for that. I don't know in detail how it works but I think in standby mode the AGC is clocked much slowly (but still doing state vector integration ???). So my question: Does anyone know more about that or has similar ideas?

Cheers
Tschachim
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movieman



Joined: 25 Nov 2004
Posts: 1018

PostPosted: Fri Apr 28, 2006 2:26 am    Post subject: Reply with quote

I'm not sure it even does state vector integration in standby, I think it just updates the clock every second or so. It's all documented somewhere, probably there's something on the Virtual AGC site.

Presumably the crew would get a state vector from the ground after they brought it back out of standby. Potentially we could simulate going into standby mode, stop the AGC emulation running and stuff the correct values into the clock and state vector when it's brought out of standby before we restart the emulation.
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chode



Joined: 31 Jan 2005
Posts: 123

PostPosted: Fri Apr 28, 2006 6:32 am    Post subject: Reply with quote

Thank you everyone for the comments. I'm getting a clearer picture on what everyone envisions as goals for further development. I generally agree with what people are thinking as far as levels of realism, etc.

I'll most likely start working on the EMS system and displays to re-familiarize myself with working on the project before dusting off the reentry code.

Question: One major difference between the vAGC and the C++ version is the units used. I remember there being talk about having a scenario option to specify measurement units. Has this been implemented? Should I build in support for both units? This will be an issue for the EMS delta V monitor and the scrolling chart. The chart would have to be modified to do metric units.

(about my hours, I'm in California)

Regards
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Christophe



Joined: 09 Feb 2005
Posts: 280
Location: France

PostPosted: Fri Apr 28, 2006 8:34 am    Post subject: Reply with quote

movieman wrote:
375 is undocumented and there's no reference to it as an error that I can find in the code.

Of course it could be a bug Smile.


Thanks movieman.
Anyway this bug is not very disturbing. The reset works well, the AGC is not jammed and the routine can go on. So...
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Christophe



Joined: 09 Feb 2005
Posts: 280
Location: France

PostPosted: Fri Apr 28, 2006 9:46 am    Post subject: Reply with quote

I totally agree with the idea of keeping the AGC++ . By the way, I think there is absolutely no reason to drop it.
In fact I believe there is not such a difference between a flight with vAGC and a flight with AGC++.
I explain myself:

- Right now, if you do an apollo flight with AGC++, you can launch with, you can display your orbit parameters with the verb82 associated with the program 11 and you can roughly perform the TLI with the program 15.
As soon as you are on course toward the moon, the AGC becomes almost totally useless and you have to use an MFD to perform the incoming maneuvers. I think that the P17 and P18 are not very practical due to their limitations (only simple orbit change or plane change but not at the same time)

- If you do an apollo flight with the current vAGC, it's almost exactly the same: You can align the IMU and launch into orbit and... that's all!
As long as you cannot change the refsmmat and not compute the necessary parameters to insert into the P30/P40 (I think especially about the deltaV's in reference to the local vertical), the only thing you can do with the DSKY is to realign the IMU with the backup P54.
So if you want to continue the flight, nothing prevent you from doing the next maneuvers with any MFD you want, exactly as well as you were using AGC++.
The only bonus seems to be the reentry capability (P61,62 and so on...)
But for example, TEI canoot be performed with the P37. Remember that P37 is only a backup program not usable outside of the Earth SOI.

However, the advantage goes to the vAGC: I hope that some big brain around here (fortunately we got many ones) will find the way to make it more usable.
As I understand, the issue is more a problem of connecting the vAGC into the orbiter environment than improving the vAGC itself.

The questions I'm asking right know are:

- How to update the refsmmat?
For the moment we have only one: the launch pad refsmmat for launch and for EPO. As soon as we are in TLC, the refsmmat has to be updated and the Xaxis takes place in the ecliptic plane, perpendicular to the projection of the line between earth and moon along the ecliptic plane, the Z axis perpendicular to the X axis and toward north (or south) celestial pole, while the Y axis completes the right hand system.
How the hell can we do that in the current state?
What about the others refsmmat? landing site, preferred and so on...?

- It's seems that there is a problem with the AGC clock, while using a saved scenario. Is it the reason why the P21 is so inacurate?
I tried to update the AGC clock with V55 in a saved scenario but that didn't change the P21 display. May be should I try a state vector update?

- Many of the AGC/LGC routines use VHF ranging that I understand as telemetry update between the 2 computers (LGC in the LM and AGC in the CM). How to do that in orbiter? Is it possible?

- If I would post procedures for using IMFD while maneuvers computations, Is somebody able to convert the parameters into something usable with P30/P40?
I think about an excel spreadsheet with macros like the one irnenginer made for state vector update.

- What about tephem? I never tried this but I wonder what would happen if I change the lauch date in a vAGC scenario?

So many dreams, so many questions, so many things to try and test...
But how fascinating is it! Very Happy
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movieman



Joined: 25 Nov 2004
Posts: 1018

PostPosted: Fri Apr 28, 2006 10:11 am    Post subject: Reply with quote

Quote:
I remember there being talk about having a scenario option to specify measurement units. Has this been implemented?


It was, but a lot of the new code doesn't call the functions it's supposed to call in order to make that work. You'd need to go through it all and fix up the places where it's broken.
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