Meadville Space Center
Welcome, Guest. Please login or register.
November 24, 2020, 02:02:10 AM

Login with username, password and session length
Search:     Advanced search
25068 Posts in 2094 Topics by 2267 Members
Latest Member: Apollo Next
* Home Help Search Login Register
+  Meadville Space Center
|-+  Project Apollo - NASSP
| |-+  Project Apollo - NASSP News & Discussion
| | |-+  Support & Bugs (Moderators: movieman, Tschachim, Swatch, lassombra)
| | | |-+  Re-entry help please.
« previous next »
Pages: [1] Print
Author Topic: Re-entry help please.  (Read 1703 times)
bart
Full Member
***
Posts: 60


View Profile
« on: July 06, 2006, 04:38:25 PM »

Sorry guy's I know aspects of this has been covered in a few different threads but I'm having problems with it.

I'm trying to carry out a re-entry with VAGC using the A15Delco checklist, page 73 and 74. I can get the VAGC to go through all the steps in P37 ok, most of it I presume is just pressing Pro? I 've tried guessing the entry time and accepting what's given (around 2hrs).

Following this procedure nothing happens, no burn, no orientation, nothing?? I try to go into P40 and get a PROG caption. I'm pulling my hair out over this. Maybe I'm overlooking something else but I've followed the checklist to the letter for P37. I also read somewhere to monitor the burn in PXX, how is this achieved? there's a page and a half for P40 in the checklist, which step allows you to monitor a burn?

I did read Mikael has done this somewhere but can't find the thread.

Posting this is the last resort as I know you guy's have a lot on and have probably got better things to do....sorry.
Logged
mikaelanderlund
Full Member
***
Posts: 205


View Profile
« Reply #1 on: July 07, 2006, 05:05:55 AM »

Hi Bart,

Have you activated DAP? Try these steps. You find these in Virtual AGC thread.

Step 1

The Following assumes you are in orbit and at POOH (Prog:00) and seperated from the SIVB.

V48E

You'll see V06N46 with R1:10002 and R2:01111. These setup the DAP.
PRO
you'll now see V06N47 with R1 and R2 both zeros. these are for the spacecraft weight in pounds. R1 for CSM and R2 for LEM. V21E+74075E
PRO
V06N48
PRO
make sure SC CONT is set to CMC and CMC MODE is set to FREE
V46E  This Starts the DAP.
V49E This runs the crew defined manuver.
PRO This launches you into routine 60 with V50N18 flashing. This is the AGC asking if you really want to do this.
CMC MODE AUTO
PRO you'll see V06N18
What should happen is the spacecraft will oreint itself to the angles you entered. Once it is within the deadband it will flash V50N18 again at which point you press ENT to exit.

Step 2

P37 Don't enter dV (VPRED) and gamma (GAMMA EI) during V06N60 but leave it at 0 the first iteration, the AGC will choose proper values for that by itself. Don't expect any orientation or burn in P37

Step 3

Activate
SC CONT - CMC
CMC MODE - AUTO
SPS THRUST - DIRECT ON


40E
       
        F 06 18

PRO
        spacecraft moves to nos-up or nos-down attitude.
        F 50 18
ENTR
       F 50 25 
ENTR
        F 06 40 (time from ignition/cutoff,
                 velocity to be gained,
                 velocity already gained

        DSKY blanks at T-35s to T-30s

        F 99 40 at T-5s ("Are you sure?")
PRO
        F 06 40

Burn is executed.


Mikael
« Last Edit: July 07, 2006, 05:16:04 AM by mikaelanderlund » Logged
bart
Full Member
***
Posts: 60


View Profile
« Reply #2 on: July 07, 2006, 07:10:22 AM »

Thanks Mikael,

I hadn't activated the DAP...!

Just been messing about with attitude and velocity changes using the VAGC all seems to work ok so far, except when doing a velocity change to increase orbit alt. I entered a time to burn of 40 mins (2.400k ApT in orbit MFD), then used P40 to do the burn and the DISKY replied with a F99 40 too soon, I wanted to burn at Apoapsis to turn an elliptical orbit into a near circular one. Any idea why it wanted to do this?  The entry for the burn time was R1 +00000E R2 +00040E R3 +00000

Is there a method of accurately achieving a particular orbit alt. using VAGC?


I'm going to try another re-entry later so I'll use your advice there, and let you know what happens.... Very Happy

Thanks.
Logged
Tschachim
Project Apollo - NASSP
Administrator
Hero Member
****
Posts: 3700


nassp.sf.net


View Profile WWW
« Reply #3 on: July 07, 2006, 08:01:57 AM »

Quote from: bart
I entered a time to burn of 40 mins (2.400k ApT in orbit MFD)...
This is not the time to burn but the MET (as shown by the mission timer for instance) of the burn.

Cheers
Tschachim
Logged

bart
Full Member
***
Posts: 60


View Profile
« Reply #4 on: July 07, 2006, 09:26:11 AM »

Sorry I didn't word that very clearly, it was 40 mins to the time I wanted to start the burn, an ApT of 2.400k  in orbit MFD when I pressed PRO following this entry :-

For MET +40min for example enter:
Code:
V25E
+00000E
+00040E
+00000E
PRO
       F 06 81 (dV in 0.1 ft/s in local vertical coordinates =
                "surface relative" at ignition, x is prograde, z is outward)


the AGC calculated the duration of the burn to give me my selected increase in speed of 500 ft/s. That part was spot on, just the timing was out.

When it asked if I really wanted to do this (F 99 40) it was no where near the time I entered, perhaps only 5 mins into the 40 min wait. I just delayed pressing PRO until as near the time as I could guess, pressed PRO and the engine lit straight away.
Logged
movieman
Moderator
Hero Member
****
Posts: 1710



View Profile
« Reply #5 on: July 07, 2006, 09:31:59 AM »

Again, you need to enter the MET, not the time to the burn. The Virtual AGC interface isn't the same as the C++ AGC.

The primary reason for that is that calculating METs from the standard Orbiter MFDs is a pain in the butt. However, if our MFD is going to do the calculations in future we could get it to give us METs instead and use those rather than relative times for the C++ AGC as well.
« Last Edit: July 07, 2006, 09:36:56 AM by movieman » Logged
bart
Full Member
***
Posts: 60


View Profile
« Reply #6 on: July 07, 2006, 10:19:11 AM »

Ahhh....ok, so if I wanted to burn in say 30 mins I would enter the Mission Elapsed Time from the clock on the CM instrument panel PLUS 30 mins.......is that correct? effectively I'm entering the MET at which I want the burn to execute?

And the moment I press PRO after entering the MET +30 this would start the count down for the burn?

Sorry guy's i'm not thick Very Happy  just like to be thorough and understand exactly what's happening here.
Logged
movieman
Moderator
Hero Member
****
Posts: 1710



View Profile
« Reply #7 on: July 07, 2006, 10:23:09 AM »

It's a while since I've used the Virtual AGC, but I'm pretty sure that's the case.
Logged
bart
Full Member
***
Posts: 60


View Profile
« Reply #8 on: July 07, 2006, 01:08:57 PM »

Just achieved a successful re-entry. Learned a lot during that flight, mainly about VAGC, very impressive.

I guess Apollo 7 is now go with VAGC, bring on Apollo 8  Very Happy

Thanks for your help.
Logged
mikaelanderlund
Full Member
***
Posts: 205


View Profile
« Reply #9 on: July 07, 2006, 02:29:36 PM »

Again, you need to enter the MET, not the time to the burn. The Virtual AGC interface isn't the same as the C++ AGC.

The primary reason for that is that calculating METs from the standard Orbiter MFDs is a pain in the butt. However, if our MFD is going to do the calculations in future we could get it to give us METs instead and use those rather than relative times for the C++ AGC as well.

I always synchronize the Orbiter's simulation time and VAGC (V25N36E) and the mission time (panel clock) at pre-launch. Then it's easier to calculating GET.

Mikael
Logged
Pages: [1] Print 
« previous next »
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.10 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!