Rendezvous test scenario.scn

[mstram]

What do I need to plug into spec 34 to rendezvous with the ISS ?

I've read the DPS, and looked at the source code.

The DPS is not much help, as it's more a reference than a "user guide" :/

 

[Urwumpe]

The DPS is not much help, as it's more a reference than a "user guide" :/

The DPS Dictionary is really the reference there, but about the procedures and actions, you should take a look at a RNDZ CL. A lot of it works, a lot more of it still requires cheating.

 

[mstram]

The DPS Dictionary is really the reference there, but about the procedures and actions, you should take a look at a RNDZ CL. A lot of it works, a lot more of it still requires cheating.

What exactly is the "cheating" ?

I was playing with the ORBTGT MFD / Shuttle fleet, and he has a "TargetingDataTable.ini” file that was presumably tailored for the "STS-131 before NCC .scn"

Do you have that MFD ?

If not any idea how he arrived at the numbers in the file ? ..:

*** What is the '-3462.0' number ?

The rest I figured out (the dt , dx, dy, dz for the SPEC 34 display)


----- TargetingDataTable.ini ---

NCC -3462.0 0.0 57.7 -48.6 0.0 1.2
Ti 0.0 0.0 76.9 -0.9 0.0 1.8
MC1 1200.0 0.0 56.9 -0.9 0.0 1.8
MC2 2994.0 29.07 27.0 -0.9 0.0 1.8
MC3 1020.0 0.0 10.0 -0.9 0.0 1.8
MC4 1620.0 0.0 13.0 0.0 0.0 0.6

======== STS-131 before NCC ===========
BEGIN_DESC

END_DESC

BEGIN_ENVIRONMENT
System Sol
Date MJD 55293.1431760693
END_ENVIRONMENT

BEGIN_FOCUS
Ship STS-131
END_FOCUS

BEGIN_CAMERA
TARGET STS-131
MODE Extern
POS 4.48 7.20 -28.32
TRACKMODE TargetRelative
FOV 40.00
END_CAMERA

BEGIN_HUD
TYPE Orbit
REF AUTO
END_HUD

BEGIN_MFD Left
TYPE Docking
TARGET ISS
END_MFD

BEGIN_MFD Right
TYPE Orbit
PROJ Ship
FRAME Equator
ALT
REF Earth
TARGET ISS
END_MFD

BEGIN_SHIPS
ISS:ISS20A
STATUS Orbiting Earth
RPOS 2801429.93 6048842.22 -873542.88
RVEL 4888.780 -1434.645 5774.270
AROT 165.79 31.89 -123.86
VROT 0.00 0.07 0.00
AFCMODE 7
PRPLEVEL 0:0.792000
IDS 0:588 100 1:578 100 2:568 100 3:476 100 4:478 100
NAVFREQ 0 0
XPDR 466
P6 0.0000
P4 0.2505
RAD 0.0000
MBS 21.6939
DIALOG
END
STS-131:Shuttle
STATUS Orbiting Earth
RPOS 2766505.84 6057914.50 -914144.60
RVEL 4914.551 -1374.657 5763.578
AROT -13.43 -39.62 32.33
VROT -0.06 -0.00 -0.00
RCSMODE 2
AFCMODE 7
PRPLEVEL 0:0.777983
NAVFREQ 0 0
CONFIGURATION 3
OV- 103
RENDER
RMSARM
ODS
OBSS
CARGODOOR 1 1.0000
KUBAND 1 1.0000
POSTLAND 0 0.0000
SSMES 1 1.0000
ADTA 0 0.0000
PETD 0 0.0000
SETD 1 1.0000
ARMTILT 1 1.0000 1 1.0000
PRADIATOR 0 0.0000
SRADIATOR 0 0.0000
GEAR 0 0.0000
PAYLOAD_MASS1 3.0000
PAYLOAD_MASS2 0.0000
PAYLOAD_MASS3 0.0000
ARM_STATUS 0.5000 0.1852 0.1705 0.5208 0.5000 0.5000
PL1_OFS 0.050000 0.700000 -1.500000
PL1_DIR 0.000000 -1.000000 0.000000
PL1_ROT 0.000000 0.000000 1.000000
PL2_OFS 2.850000 2.150000 3.850000
PL2_DIR 0.000000 1.000000 0.000000
PL2_ROT 1.000000 0.000000 0.000000
PL3_OFS -1.850000 1.800000 11.750000
PL3_DIR 0.000000 1.000000 0.000000
PL3_ROT 0.000000 0.000000 1.000000
PL4_OFS 0.000000 1.000000 -5.500000
PL4_DIR 0.000000 -1.000000 0.000000
PL4_ROT 0.000000 0.000000 1.000000
PL5_OFS 0.000000 -1.800000 4.100000
PL5_DIR 0.000000 1.000000 0.000000
PL5_ROT 0.000000 0.000000 1.000000
PL6_OFS 1.850000 1.800000 11.750000
PL6_DIR 0.000000 1.000000 0.000000
PL6_ROT 0.000000 0.000000 1.000000
KEEL_CAM 0.145000 -0.500000 -1.356000
OMS
CALLOUT
ASSIST 133.000000 77.000000
END
BayLightsBLights
STATUS Orbiting Earth
RPOS 3425808.99 3807021.09 4356276.03
RVEL -5251.979 -1485.278 5426.098
AROT 109.77 31.58 143.26
VROT 0.00 0.00 0.07
ATTACHED 0:15,STS-131
AFCMODE 7
NAVFREQ 0 0
LIGHTS 0.10
ODS
DIALOG
END
END_SHIPS

 

[Urwumpe]

Cheating means using non-SSU tools and non-STS-procedures. :lol:

 

[indy91]

The ORBTGT MFD is based on some old lua scripts of mine. The Targeting Data Table contains the same parameters that can be used in SPEC 34 in SSU.

The first column is the Time of Ignition relative to a base time. In the real Shuttle this target data table was stored in the memory and with an Item 1 input the target set for one maneuver could be loaded. The first base time you would load is the TIG of the TI Maneuver. "-3462.0" is the relative time for the first onboard targeted rendezvous maneuver, the NCC maneuver. So NCC happens 3462 seconds before TI.

This target set depends on the altitude of the target orbit. In the rendezvous checklist, (e.g. STS-135: https://www.nasa.gov/centers/johnson/pdf/567076main_RNDZ_135_F.pdf) there is a section called Reference Data. Here the data tables for different altitudes are listed on pages 6-4 and 6-5.

In SSU there are currently three limitations, I think. First, SSU doesn't automatically load a target set with Item 1. Related to that, SSU doesn't use the base time feature yet so a time relative to this base time that was loaded from the memory wouldn't show the proper TIG.

And lastly, in the real Shuttle the MC2 maneuver is not performed at the specified time but at a specific elevation angle relative to the target. So the Time of Ignition was shifted for this maneuver. The elevation angle in the targeting data table you posted is 29.07°. This TIG calculation based on elevation angle is also not working yet in SSU, so you have perform the "MC2 On Time" from the rendezvous checklist.

 

[mstram]

Cheating means using non-SSU tools and non-STS-procedures. :lol:

Like .... for example .... ?

---------- Post added at 06:23 PM ---------- Previous post was at 05:58 PM ----------

The DPS Dictionary is really the reference there, but about the procedures and actions, you should take a look at a RNDZ CL. A lot of it works, a lot more of it still requires cheating.

I have JSC-48072-135 / Rendezvous STS-135.

Is that the doc you meant ?

That doc shows what they are inputting but not why.

For example, after I ran the OrbtGT tutorial, it seems ?? that Item 28 (Compute T1 ) can be used "alone" (without Item 29 and whatever data it requires), to calculate the burn params for a desired interecept.

Though the DPS, does say for Item 29 (Calc T2) that it is used to :
"The maneuver solution computed is that required to null relative velocity at T2 TIG". ... Which I suppose might be useful (if you don't want to continue to "zoom" by the target ? :lol:

Also, while the OrbtGT MFD seems to require a "re-input" of Item 1 / 9 (the MFD is already initialized with Item 1 = 9), to "kick" it into action, it seems the SSU SPEC 34 can run Item 28, "immediately", (without executing Item 1/??? (1 ?) and is outputting the "top line" (which IS getting loaded into OPS 202 (19,20,21)

Are there any other docs, beside the SCOM, DPS, above-mentioned-RNDZ doc, that you are using to code SPEC 34 / ORBIT TGT ?

---------- Post added at 06:35 PM ---------- Previous post was at 06:23 PM ----------

@indy91 (for some reason the forum quote button won't quote your post)

"The ORBTGT MFD is based on some old lua scripts of mine. The Targeting Data Table contains the same parameters that can be used in SPEC 34 in SSU"

Are those scripts online somewhere ? / Do you still have them ? / Can you post them / send them to me ?

>In SSU there are currently three limitations, I think. First, SSU doesn't automatically load a target set with Item 1.

As per my earlier post, it seems ITEM 28 works with / without ITEM 1. Do you have any idea what SSU-SPEC 34 IS doing ?

>Related to that, SSU doesn't use the base time feature yet so a time relative to this base time that was loaded from the memory wouldn't show the proper TIG.

What is the "base time feature" ? (The DPS is pretty terse about it).

 

[GLS]

I think there's a post somewhere from SiameseCat explaining how to use the SPEC 34. I seem to recall that only T1 was used and the target was not loaded via item input but by editing the scenario file somehow.

 

[indy91]

The scripts are still available on Orbithangar, but they don't do anything new for you. The Orbit Targeting MFD is basically a nice GUI with the same functionality, so I would always use the MFD.

Base Time works as follows. The real Shuttle computer and the targeting data table for the Orbit Targeting MFD don't have an absolute time of ignition (measured in mission elapsed time) stored, but instead a relative time. The relative time for NCC is -3462 seconds, the relative time for the TI maneuver is 0 seconds. Obviously the TI maneuver doesn't happen at 0 seconds Mission Elapsed Time. So the relative times are relative to a so called Base Time. This Base Time was calculated by Mission Control and could then be used as an input for the computer on the Shuttle. The first Base Time is identical with the Time of Ignition for the TI Maneuver, hence the 0 seconds in the table. For the NCC maneuver, which happens before the TI maneuver, the same Base Time is already used and so there is a negative number, the -3462, stored.

The advantage here is you don't have to load a complicated Time of Ignition for each of the NCC, TI, MC1-4 maneuvers. Without a Base Time you would always have to load the full TIG e.g. "001\02:03:04". Instead you load a Base Time once or twice and every event is happening relative to this Base Time.

As I said in the post above, during a normal rendezvous sequence you calculate a new TIG for the MC2 maneuver based on the elevation angle. This new TIG is used as the new Base Time for the MC3 and MC4 maneuvers. That's why the first column in the table has a smaller number for MC3 than for MC2. The MC1 and MC2 times are still relative to the TI maneuver.

All this applies to the real Shuttle computer. SPEC 34 in SSU can already calculate the rendezvous maneuvers and does eveything the real SPEC 34 does, except for the three missing features: it doesn't use the Base Time yet, it can't calculate a new TIG for the MC2 maneuver based on elevation angle and the targeting data table is not stored and can be loaded with Item 1, but instead each of the items for the maneuver (DX, DY, DZ, DT etc.) has to be loaded manually.

 

[mstram]

The scripts are still available on Orbithangar, but they don't do anything new for you.

Ya, I'm not expecting anything new, just maybe something more understandable than the SSU code (probably not).

I bought the book "Fundamentals of Astrodynamics", and it's not the easiest read for a non-math / space geek (but I'm slowly picking up some of it)