I just tried to compile the Latex files and some of the images seem to be missing. The missing files are SSU_Attachments.jpg, SLWT.jpg and SRB.jpg.
Speaking of documentation, could someone write a short tutorial on how to use GNC SPEC 34 ORBIT TGT for rendezvous burns?
Based on appearances, yes. Only thing missing is the ORBITER STATE section.I could do that, is the SSU implementation equivalent to the FDF?
Based on appearances, yes. Only thing missing is the ORBITER STATE section.
Mostly. Specifying the elevation angle at TIG (and calculating the TIG based on this) isn't supported. Also, using ITEM 1 to load all the targeting values doesn't work - each item has to be loaded individually.I could do that, is the SSU implementation equivalent to the FDF?
@BEGINSOFTWARE StateVectorSoftware
TARGET_VESSEL ISS
@ENDSOFTWARE
Mostly. Specifying the elevation angle at TIG (and calculating the TIG based on this) isn't supported. Also, using ITEM 1 to load all the targeting values doesn't work - each item has to be loaded individually.
From a practical standpoint, it's targeting a specific vessel. In real life Mission Control would provide the state vector (which would be propagated by the shuttle GPCs). Since we don't have simulate Mission Control yet, I think it's better if SSU tracks the target vessel.Would be better we could put some general orbit elements into the mission file for the 1-40 target entries. The targeting data is not for specific vessels, but rather for general orbits, that should be reached.
From a practical standpoint, it's targeting a specific vessel. In real life Mission Control would provide the state vector (which would be propagated by the shuttle GPCs). Since we don't have simulate Mission Control yet, I think it's better if SSU tracks the target vessel.
The way SPEC 34 is used, it really targets a position instead of an orbit (the T2 burn is never performed - the point is to target a particular position relative to the rendezvous target).Actually, the data would come from mission planning and be written on magnetic tape before launch. Updates would be possibly delivered if needed.
It is not just targeting one vessel, but also preliminary orbits to that vessel, like the orbit after NCC, the orbit after MC2, etc...
The way SPEC 34 is used, it really targets a position instead of an orbit (the T2 burn is never performed - the point is to target a particular position relative to the rendezvous target).
SPEC 34 always targets the same state, but the offset changes between burns. The TI burn is supposed to occur at a particular position relative to the ISS, so the NCC burn is set up so the shuttle will be in the correct position at TI. For the TI burn, the offsets are changed to set up the MC4 burn.
Matching velocity is only done at then end of the rendezvous and is done manually using the RCS thrusters (this prevents problems due to nav error, and the relative velocity should be small at this point). If you look at the Rendezvous C/L, the T2 burn is never performed.Does not fit to the description of the display: Yes, you can omit the second maneuver, but the target is the position of a virtual satellite in a target orbit, all seven elements described. If you would use it without the second maneuver, you would reach the target without matching velocity.
Also, better read the Rendezvous C/L again, the burn targets are called by different target IDs, but have otherwise very similar data entries, only varying by orbit altitude.
Matching velocity is only done at then end of the rendezvous...
The T1 burn targets a specific position relative to the target object (the DX,DY,DZ values) at a specific time (the DT value). The T2 burn then nulls the relative velocity between the shuttle and the target.
The targeting software needs to know what orbit the target object is in, but this is only so it can calculate the target's position/velocity at T2.
I don't think there's any way to specify a velocity bias for the T2 burn. The elevation angle is used to determine the T1 TIG; it doesn't affect the target position. If the elevation angle is specified, the T1 burn will occur when the target is at a particular elevation above the shuttle.Yes, exactly that. But not just nulling the velocity, it also permits a bias. And the target is not always a spacecraft. You can see that by looking at the table in the rendezvous C/L: different targets and positions, but similar offsets and elevation angles.
I don't think there's any way to specify a velocity bias for the T2 burn. The elevation angle is used to determine the T1 TIG; it doesn't affect the target position. If the elevation angle is specified, the T1 burn will occur when the target is at a particular elevation above the shuttle.
I don't understand why you would use SPEC 34 (and then perform a NCC burn, TI burn, 3 midcourse corrections and the MC4 burn) unless you're targeting a spacecraft. If you just want to change orbits, a Hohmann transfer is a lot simpler.