Author Topic: Apollo DSKY electroluminescent glass panel display replica  (Read 481 times)

Offline Trebor

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Really nice replica of the Apollo DSKY by Applied Science.
A good source for anyone wanting to know how they worked or build their own.


Offline bknight

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #1 on: May 16, 2019, 08:58:33 AM »
Now that is cool. :)
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Offline JayUtah

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #2 on: May 17, 2019, 11:38:09 AM »
That is awesome.  My first boss, one of the old Apollo engineers who mentored me, has an actual DSKY.  Thing weighs a friggin' ton.
"Facts are stubborn things." --John Adams

Offline bknight

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #3 on: May 17, 2019, 11:55:29 AM »
That is awesome.  My first boss, one of the old Apollo engineers who mentored me, has an actual DSKY.  Thing weighs a friggin' ton.

Without doing any research, are the two DSKY's in the CSM and LM identical?
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
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Offline Obviousman

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #4 on: May 17, 2019, 05:42:58 PM »
That is awesome.  My first boss, one of the old Apollo engineers who mentored me, has an actual DSKY.  Thing weighs a friggin' ton.

Without doing any research, are the two DSKY's in the CSM and LM identical?

I believe so.

Offline JayUtah

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #5 on: May 18, 2019, 01:31:54 PM »
Without doing any research, are the two DSKY's in the CSM and LM identical?

Ya know, for a hot minute I thought the LM DSKY had a slightly different form factor.  Now that I'm comparing all the pictures I can find, I don't think that's the case.  I think all the DSKYs were the same design.  The one my old boss had was a CM DSKY to be sure, because it was one that eventually got pulled from the Apollo 14 CM and replaced with a better one.  He got it because he was one of the engineers who worked on the docking probe, and was called into troubleshoot Apollo 14's docking issues.
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Offline bknight

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #6 on: May 18, 2019, 03:21:54 PM »
Without doing any research, are the two DSKY's in the CSM and LM identical?

Ya know, for a hot minute I thought the LM DSKY had a slightly different form factor.  Now that I'm comparing all the pictures I can find, I don't think that's the case.  I think all the DSKYs were the same design.  The one my old boss had was a CM DSKY to be sure, because it was one that eventually got pulled from the Apollo 14 CM and replaced with a better one.  He got it because he was one of the engineers who worked on the docking probe, and was called into troubleshoot Apollo 14's docking issues.

The cats out of the bag so to speak, now I know why you knew so much about the docking issue.  ;D
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Offline ajv

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #7 on: May 18, 2019, 06:44:23 PM »
Without doing any research, are the two DSKY's in the CSM and LM identical?

Surely one difference is that the LM had yellow ALT and VEL lights.
https://www.hq.nasa.gov/alsj/a12/LM6-co28.jpg

They indicated that the altitude and velocity data-good signal from the landing radar was absent during the Landing Radar Data Read Routine. [LM6 (Intrepid) and LM10 (Falcon) handbook - page 3-77]. In addition, the ALT light flashes if the data-good signal is received but the data does not pass the LGC Reasonableness Test.

BTW the TRACKER indicator is energized (their word) if LR altitude data-not-good discrete or LR velocity data-not-good discrete occurs during the LGC data read sequence. [same page]. That seems to be the same - but a less specific indicator. The TRACKER indicator is also used for the rendezvous radar.

Re: LGC Reasonableness Test. The crew had to manually decide to incorporate the radar values (Verb 57 - Permit Landing Radar Updates). Presumably the Reasonableness Test was an automatic data check to avoid bad radar data infecting the tracking even if you're permitting updates. I guess there'll be something about that in the LGC sources.

Also, the Apollo Operations Handbook LM 10 (and subsequent) Volume 1 indicates two more decals (PRIO DISP and NO DAP) in the other two empty DKSY indicator slots but I can't see where they were documented in the handbook.
https://www.hq.nasa.gov/alsj/dsky_lm.jpg

Offline Allan F

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #8 on: May 19, 2019, 08:22:09 PM »
That is awesome.  My first boss, one of the old Apollo engineers who mentored me, has an actual DSKY.  Thing weighs a friggin' ton.

32 kg?
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Offline ajv

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #9 on: May 20, 2019, 04:58:47 PM »
Re: Landing RADAR Data Reasonableness Test

I dived into the documentation and the Luminary source and here's what I think is happening.

From R-567: Guidance System Operations Plan for Manned LM Earth Orbital and Lunar Missions Using Program Luminary 1C (Rev. 131) Pages 5.3-81-85

First, here's the note about why they're doing it:
Quote
The objective of the LR data reasonableness test is to detect and reject degraded LR data caused by cross-coupled side lobe or vibrating structure frequency-tracker lock-up.
Well, naturally. (However, if you now want to make a comment about a cross-coupled side lobe or a vibrating structure frequency-tracker lock-up you're either an electrical engineer or you've got a dirty mind.)

The altitude (un)reasonableness test is a linear function of the estimated current altitude:
Quote
|<delta>q| >= DELQFIX + 0.125 q'
This tests if the (absolute value of the difference between the landing radar altitude and the currently estimated altitude based on the state vector) is greater than or equal to (DELQFIX + 1/8 of the state vector estimated altitude). If this happens then the LR data looks bad and we should flash the ALT light so the astronaut is aware that there is a problem.

The reasonableness test says that as you're descending the altitude presented by the landing radar should fall within a gradually decreasing envelope around the current state-vector's estimate.

Apparently DELQFIX is normally set to 50 feet but I'm not sure where. DELQFIX is in erasable memory. Of course all the calculations are done in meters - in this case scaled 2^-24 with the least significant bit of the double precision value representing 1/16 of a meter.

The Luminary (LGC computer program) code for this calculation is as follows. The #s are comments. DELTAH (=<delta>q) and HCALC (=q') have already been computed and DELTAH is already in the MPAC accumulator register.

Code: [Select]
        TC      INTPRET
        ABS     DSU
                DELQFIX         # ABS(DELTAH) - DQFIX   50 FT NOM
        SL3     DSU             # SCALE TO 2(21)
                HCALC           # ABS(DELTAH) - (50 + HCALC/8) AT 2(21)
        EXIT

        INCR    LRLCTR

        TC      BRANCH
        TCF     HFAIL           # DELTA H TOO LARGE
        TCF     HFAIL           # DELTA H TOO LARGE
        TC      DOWNFLAG        # TURN OFF ALT FAIL LAMP
        ADRES   HFLSHFLG
        ...
HFAIL
        ...
        TC      UPFLAG          # AND SET BIT TO TURN ON TRACKER FAIL LITE
        ADRES   HFLSHFLG

The stuff between the "TC INTPRET" and the "EXIT" tells the instruction interpreter to execute some magic multi-precision interpreted instructions. To save space (instructions codes are small and you can fit two in a word) a pair of instructions are written on a single line and then the arguments for those instructions follow that line. So you should mentally be reading this as:

Code: [Select]
        start of magic interpreter instruction section
          ABS                   #  ABS(DELTAH)
          DSU   DELQFIX         #  ABS(DELTAH) - DELQFIX
          SL3                   # (ABS(DELTAH) - DELQFIX) * 8
          DSU   HCALC           # (ABS(DELTAH) - DELQFIX) * 8 - HCALC
        end of magic interpreter instruction section
which computes the value of
Quote
(|<delta>q| - DELQFIX) * 8 - q'
which has the correct sign for the reasonableness test.

The "TC BRANCH" is a subroutine call which tests the double-precision value left by the magic multi-precision instructions and then runs whichever of the following instructions corresponds to a value > 0, = 0 or < 0. In this case it will jump to HFAIL if the value is >= 0.

Finally the flag argument to the "TC UPFLAG" subroutine call is (naturally) in the instruction slot following the subroutine call. We're going to be setting the H-FLaSHing-FLaG which will cause the ALT light to flash.

The velocity (un)reasonableness calculation is similar but uses vectors!
« Last Edit: May 20, 2019, 06:41:38 PM by ajv »

Offline ka9q

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #10 on: May 21, 2019, 02:54:23 PM »
The Apollo 9 CM ("Gumdrop") is in the San Diego Aerospace Museum. It's missing its DSKY, along with a lot of other stuff (looks really sad in there). Maybe Jay knows where it went? :-)

Offline JayUtah

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #11 on: May 21, 2019, 03:22:39 PM »
The Apollo 9 CM ("Gumdrop") is in the San Diego Aerospace Museum. It's missing its DSKY, along with a lot of other stuff (looks really sad in there). Maybe Jay knows where it went? :-)

It was even sadder in Jackson, Mich. where it came from.  It's also the only flight CM I've been inside, and it was sad (and smelly) and missing its DSKY then too.
"Facts are stubborn things." --John Adams

Offline ajv

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Re: Apollo DSKY electroluminescent glass panel display replica
« Reply #12 on: June 08, 2019, 12:51:18 AM »
Apparently DELQFIX is normally set to 50 feet but I'm not sure where.
The values for the various missions are in the pad loads.
Quote
Apollo 1160.96 m(200 feet)
Apollo 1260.96 m(200 feet)
Apollo 1360.96 m(200 feet)
Apollo 14152.4 m(500 feet)
Apollo 1530.48 m(100 feet)
Apollo 1630.48 m(100 feet)
Apollo 1730.48 m(100 feet)