STS-130: Full Rendez Vous with FDO MFD

[Gingin]

Hello,

I tested quite a lot the FDO MFD made by Indy
https://www.orbiter-forum.com/showthread.php?t=40471

Very nice MFD, reflecting some of the tools that Flight Dynamic Officers had to elaborate Shuttle Flight Plan.

A quick sum up of how strong it might be to reproduce with a great accuracy real mission.

Here, we gonna talk about STS-130, Launched Monday 8 Feb 2010 at 14h06 UTC.
Rendez vous on Flight Day 3, around MET 1/19:30 for Docking
ISS was at this epoch on a 188 x 183 orbit

It was the last Night Launch of STS programm

https://en.wikipedia.org/wiki/STS-130

For that first try, I used Spherical Gravity, with a launch window 300 seconds before the descending node to be almost in plane as there will be no nodal precession.




Endeavour on the Launch Pad

ISS waiting for her,

Lift off, Endeavour in roll programm

MECO time, Dump of propellant that will add around 10 fps of velocity.
Direct insertion Orbit of 124 Nm by 31 Nm
Apogee in 25 mn

MET 0/0:36

OMS 2 burn was done at MET 0:0:37 mn ( 38:35 in real), for an Orbit of 124 Nm by 110 Nm
Over Saudi Arabia with Sinai and Aden golf, pretty impressive details on the ground
90 ° behind ISS ( 91 ° ish in real) after OMS-2

Alright, time to fire the FDO MFD and planify the rest of our Journey
Two important documents
First one, the forecasted Nasa flight plan for a Monday Launch

Second one, the real flight plan flown ( both of them are really close)

And here what we have after a bit of FDO preparation, trying to match the NASA Flight plan

One phasing burn ( NC-1), on plane change burn ( NPC). Value is real small, Rinc was 0.01 ° after insertion and with no nodal precession, it helps :lol:

Then an height Adjust manouveuer ( NH), quite early on in that Flight plan. A bit weird, as it acts also as a phasing burn .

Then a place holder phasing burn ( EXDV). It adds 3 fps in prograde direction. Those burns were forecasted to avoid over phasing at the end of the rendez vous. One or two by Flight days were done.

Then the NC-4 burn, initiation of the last part of rendez vous, with the constraint to be 40 Nm behind ISS at a given time
Met of 1:15:40 here for1:15:42 in the real FP, not bad

And finally, Stable Orbit Initiation ( Ti) and Rendez Vous ( Mc 4) to finish the rendez vous plan.
Also, we can note that the lighting constraints at Ti ( Sunset minus 36 mn ) are respected.
It was important for a good visual on ISS before the MC 3 burn and to allow some Star tracker pass during last orbit before Rendez Vous.


So, we are within 2 mn of the real one after almost two days in space, let's see how it goes practically now





MET 0/02:36

First phasing burn, NC-1
It will raise the Apogee at 184 Nm to reduce the catch up rate and adjust the phasing procedure

MET 0/3:23

NPC burn.
We will reduce to zero at a node our Relative Inclination and it will stay like that with Spherical Gravity parameter.

Note that if we activate Nodal Precession and Non spherical gravity, we have to Launch with an Eastward difference in LAN ( by some 0.15 °) to be in plane with a small NPC burn the day of rendez vous, as the LAN will drift westward faster for the Shuttle ( lower orbit) than ISS.
That is fascinating to plan those thing.

Overhead Marocco and Gibraltar

Hypnotic desert

MET 0/16:52

NC-2 burn ( NH) to adjust the height of the Perigee. I will goes from 113 to 164 Nm.
Catching rate further reduced with that burn.
Rendez vous in one day ( like we said, really early NH burn for that mission)

Canada in Background during the burn, leaving it for Atlantic Ocean

Post NH and EXDV burns ( 3 fps) parameters, looking good.
Phase of 25 °, 2900 km behing the lady. Close to FP

Alright, time now for the last part of rendez vous starting at NC-4 burn
Rendez vous in two orbits from now on
A quick recap on what we want to fly and where we want to be as per NASA procedure

Two relative motion plot, first one from NASA, second one made by hand for STS 88 with the distance in Kfeet and Km for a better situational awareness

MET 01/15:41


Final Phasing burn NC-4
We wanted to be 40 Nm behind ISS ( 250 Kfeet/ 76.2 km)
We are 75.87 km behind, sweet

It will raise the perigee to 178 Nm to be one orbit Later in good conditions for Ti burn

Let's fire the ergols

MET 01/16:14

Time now for the first Lambert targeted Burn using Spec 34
It is called NCC ( Corrective Combination Burn)
It is named like that because it is a burn on all three axis ( X Y Z) that will affinate our Ti position 57.7 mn later on


Some explanations on that tool
It used Lambert equations, which allows to add time in the equation.
We are at a relative position at time T1 and we want to be in a finite amount of time ( DT) at a specific relative position at T2 regarding the target ( Delta X for downrange, Delta Y for crossrange, Delta Z for Height in kfeet)


T1 TIG: Time of when we want to make a burn ( red)
DX ( downrange), Dz ( height), DY ( cross range) will be the relative position of the Shuttle compared to ISS at Time of Ignition ( in kilo feet)
Dx dot etc will be the relative speed at TIG
Not yet implemented in SSU




T2 TIG is the time where we want to be at a specific position relative to ISS
That position is define below with DX,y z. ( blue)
For example, we can say to the computer : I want to do a burn at T1 07:00, I want to be in one hour T2 08:00 at ISS position, 10 kfeet below ( Dx=0, Dy=0, Dz= +10)

Then Item 28 compute T1 will try to give us a solution in LVLH frame that we can read at the top of the Spec 34 display ( DVX,y,z), automatically transfered to OPS 202 for the burn (Pink)


Ti timing is one orbit after the NC burn we made, so around MET 1/17:12
We want to burn 57.7 mn earlier for NCC, hence the T1 at 1/16:14:18

Dt of 57.7 mn
Dx -48.60 ( 48600 feet/ 8nm behind ISS at Ti)
Dy 0 ( no cross range)
Dz 1.20 ( 1200 feet below her at Ti)


Result is a small burn of 3.4 total velocity, thanks to the good phasing done by FDO Mfd

One engine burn for small DV

MET 01/17:12


Ti burn now, Stable Orbit Initiation Burn
We target the MC-4 burn here, 76.9 mn later where we want to be 900 feet behind ISS and 1800 feet below

You can notice that value are really close to FDO and real FP one

Thanks to the good sunlight condition ( 36 mn before sunset), we already have a good visuel on ISS

Last orbit before rendez vous, with a couple of Mid course correction






Mid course correction

First one 20 mn after ti burn
We change the T1 and the DT to let the T2 ( 01:18:28 MC 4 target) the same

MC-1 very small ( 0.5 fps)
Multi axis correction, just some RCS firing in Translation mode to null the VGO on X Y and Z shuttle body axes

MC-2 correction, 50 mn after Ti

MC-3 correction, 67 mn after Ti
1 fps of correction, really low

MET 01/18:28:54


MC 4 correction, Stable Orbit Rendez Vous burn.
We are at less than 2000 feet from ISS.
That burn will target a stable R bar position in 13 mn , 600 feet behind ISS

In real, it happened at MET 01/18:29:23
Look how close we are from real timeline ( half a minute)

I forgot to take a pic, I took the one from STS 88 just to see the D x y z paramaters

Arriving at R bar position with natural breaking.
We are a tad lower than ISS, so Shuttle will have a tendency to fall down.
Hence the need to fire +Z translation thrusters ( it avoid plume from -Z thrusters)





600feet below, less than 1 fps of relatice speed.

Then V bar transition

And Docking on time for Endeavour, with good sunlight conditions

I ran out of Forward RCS prop, always to impatient for the final phase of docking which is quite long in real and slow.



Really impressed by the FDO tools.
Great help, great accuracy.

It is feasible to do it by hand for rendez vous, but not with that timeline precision for Sun conditions particularly


Great job Indy

 

[Tim13]

Hi Jean,

I'll just throw out some questions if you don't mind, this way, others down the road might run across them when searching for information.

First question is easy. In one of the pictures, you have the commanders top CRT in "2021/ /" and the bottom CRT in "2012/034/".

So the bottom CRT is running SPEC 34. How did you physically get that to happen. In other words, what series of key strokes did you use? I've yet to be able to pull up SPEC 34 like that.

See, I told you the first question would be easy....LOL.

Thanks,

Tim

 

[GLS]

Hi Jean,

I'll just throw out some questions if you don't mind, this way, others down the road might run across them when searching for information.

First question is easy. In one of the pictures, you have the commanders top CRT in "2021/ /" and the bottom CRT in "2012/034/".

So the bottom CRT is running SPEC 34. How did you physically get that to happen. In other words, what series of key strokes did you use? I've yet to be able to pull up SPEC 34 like that.

See, I told you the first question would be easy....LOL.

Thanks,

Tim

Simple, on the selected keyboard type:
SPEC
3
4
PRO

AFAIK, they only used the CRTx MDUs to display the "CRT (green) displays".

 

[Urwumpe]

AFAIK, they only used the CRTx MDUs to display the "CRT (green) displays".

Correct - since these displays are converted from DEU format to MDU format by the IDPs, you can't even replace any failed CRT MDU with any other MDU. It must be controlled by the IDP, which function you want to replace.



In the real shuttle, you can also change which GPC is driving which IDP, something that SSU does not model yet.

 

[GLS]

Correct - since these displays are converted from DEU format to MDU format by the IDPs, you can't even replace any failed CRT MDU with any other MDU. It must be controlled by the IDP, which function you want to replace.



In the real shuttle, you can also change which GPC is driving which IDP, something that SSU does not model yet.

Admittedly, I've not looked in-depth at this area, but I still haven't seen anything, other than crew procedure, that limits what each MDU can do (other than being connected to IDPx and not IDPy). :shrug:

Anyway, a discussion for another thread.

 

[Gingin]

@Tim: To put a DPS page on the lower MDU, you press the arrow and click on DPS
It will be a repeater of CRT 2 for the lower left mdu and crt 1 for lower right mdu

So in the screen, it is on lower left mdu, repeating crt 2 ( linked to GPC2) which you can dial with the right keyboard with the switch on IDP/CRT 2

 

[Tim13]

Thanks to all for the tips. For some reason, I thought SPEC34 needed to be executed and not programmed.

I noticed that SPEC34 can run in OPS201 and OPS202. Does it matter when using SPEC34?

Can someone expand on the use and function of the RESUME key?

Tim

 

[Urwumpe]

Thanks to all for the tips. For some reason, I thought SPEC34 needed to be executed and not programmed.

Thats what you do. Programming SPEC 34 would require you to either use SPEC 0 (GPC MEMORY) and some hex editing or HAL/S.... or in SSU, C++ (maybe with HAL/S like DSL)

Remember that the Space Shuttle was designed in the 1970s. While early prototype graphical user interfaces existed, keyboard operations had still been the norm back then. And interactive computer applications that interact with a user had even been rare - most computers at that time did batch processing of tapes or punch cards.

I noticed that SPEC34 can run in OPS201 and OPS202. Does it matter when using SPEC34?

No, a SPEC is overlaid to a OPS. By entering a SPEC or DISP, the OPS keeps on running in the background. If you enter a DISP from a SPEC, OPS and SPEC run in the background.

Can someone expand on the use and function of the RESUME key?

It makes you go up one level in the display hierarchy. For example, you go from OPS to SPEC, the pressing RESUME makes you go back to the OPS. If you are in a DISP, RESUME goes back to the SPEC or the OPS.


See the "Crew Software Interface Workbook"/CSI 21002

 

[Gingin]

Good introduction book to the Shuttle Computer

https://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=0ahUKEwiI0PbHgenWAhWBIcAKHbXoCecQFgg8MAc&url=https%3A%2F%2Fforum.nasaspaceflight.com%2Findex.php%3Faction%3Ddlattach%3Btopic%3D17437.0%3Battach%3D143306&usg=AOvVaw10GSCKIigUK4q3hKjETmyA

 

[Urwumpe]

Good introduction book to the Shuttle Computer

https://www.google.fr/url?sa=t&rct=...ttach=143306&usg=AOvVaw10GSCKIigUK4q3hKjETmyA

Its a bit low-level maybe.

 

[Tim13]

If someone has a quick minute, would you look at this scenario, and FDO text file I modified for the STS-126 launch? The reason I edited it, was to launch 300 seconds before the node, to reduce the RInc between Endeavour and ISS. It seems to me I'm too close to the ISS. The phase angle seems too small.

The FDO MFD seems to work for the OMS-2 burn with my edited scenario, but I haven't gone past that.

Lastly, is there a way to save your progress in the FDO MFD to pick up where you left off during a later session of simming?

One other question: After the FDO MFD populates post MECO with the burn TIGs, and velocity changes, would it be reasonable to take a screen capture of it, and use those numbers all the way to rendezvous? Or would too much cumulative error be introduced as orbits and maneuvers start to add up over the course of the mission?



Thanks,

Tim

 

[indy91]

If someone has a quick minute, would you look at this scenario, and FDO text file I modified for the STS-126 launch? The reason I edited it, was to launch 300 seconds before the node, to reduce the RInc between Endeavour and ISS. It seems to me I'm too close to the ISS. The phase angle seems too small.

The FDO MFD seems to work for the OMS-2 burn with my edited scenario, but I haven't gone past that.

Different phase angles can have different rendezvous profiles. I'll launch your scenario and will try which one works best. But in general a small phase angle can become a large phase angle by adding 360° of phasing. And it's still possible to do a Flight Day 3 rendezvous with that.

Lastly, is there a way to save your progress in the FDO MFD to pick up where you left off during a later session of simming?

One other question: After the FDO MFD populates post MECO with the burn TIGs, and velocity changes, would it be reasonable to take a screen capture of it, and use those numbers all the way to rendezvous? Or would too much cumulative error be introduced as orbits and maneuvers start to add up over the course of the mission?

I'll answer those together. The "OMP Executive Menu" has save and load buttons for the constraint tables. So what I have usually done is have the pre mission plan saved in the e.g. "STS-126" file and then when a maneuver has been done like OMS-2 I deleted that maneuver from the table with the DEL button, did any other necessary modifications and saved the new plan in "STS-126A" and many letters after "A" afterwards for later states of the constraints table. That way you don't have to use the initial plan throughout the whole mission. And no, I don't think it would work very well to do that. There will always be small error that accumulate over time. And I didn't have great results so far for very large burns (150+ ft/s). Either because the MFD isn't calculating the TIG or DV for those right or because SSU isn't executing the burns accurately enough.

 

[Wolf]

And no, I don't think it would work very well to do that. There will always be small error that accumulate over time. And I didn't have great results so far for very large burns (150+ ft/s). Either because the MFD isn't calculating the TIG or DV for those right or because SSU isn't executing the burns accurately enough.

This is where I get lost: how do we know what has to be changed as the mission unfolds: type of burn, TIGs, DVs, etc. in order to meet the rendezvous constraints?

 

[indy91]

Ok, I launched with the scenario from Tim, and the phase angle at OMS-2 would be 19°. That is too small for Shuttle missions. So we add 360° of phasing, making it 379°. I'll try to come up with a rendezvous plan for that. The basic plan that you have should still apply, just some modifications are necessary like the number of revolutions between maneuvers. It's definitely a trial-and-error process though.

This is where I get lost: how do we know what has to be changed as the mission unfolds: type of burn, TIGs, DVs, etc. in order to meet the rendezvous constraints?

Yeah, it's not so easy. But usually the mission plan as it stands before OMS-2 is as complicated as it gets. After that you are mostly deleting maneuvers that you have already done. Delete constraints that have no maneuver anymore that can control them (after the last phasing maneuver you don't have any phasing control anymore). That kind of stuff. There are a few instances where the type of burn changes, like NC maneuvers that were only placeholders of the type EXDV and become NC type burns eventually, when they are the next upcoming maneuver.

I'm just implementing the MFD as the FDO Console Handbook tells me how the Orbital Maneuver Processor is supposed to work. And it does have detailed instructions on how to use it. But that document is not available to everyone unfortunately. It would basically be a replacement for a manual for the FDO MFD.

What I will do is post a complete walkthrough of a mission with screenshots of the constraints and evaluation tables. That should help people understand the workflow with the MFD.

 

[Wolf]

Are you planning also on releasing an FDO MFD manual eventually? Do you think it would be helpful as a general guide or every mission having its own singularities has to be dealt with separately?

 

[indy91]

Are you planning also on releasing an FDO MFD manual eventually? Do you think it would be helpful as a general guide or every mission having its own singularities has to be dealt with separately?

If the FDO Console Handbook doesn't become publically available (for free) then I will definitely release a manual. I've done a bunch of posts explaining things in the thread about the MFD already, so collecting those in one document would be a good starting point.

 

[GLS]

Ok, I launched with the scenario from Tim, and the phase angle at OMS-2 would be 19°. That is too small for Shuttle missions. So we add 360° of phasing, making it 379°. I'll try to come up with a rendezvous plan for that. The basic plan that you have should still apply, just some modifications are necessary like the number of revolutions between maneuvers. It's definitely a trial-and-error process though.

From the official FDO MFD thread:

The phase window was based on a 185 nm average ISS orbital altitude and an 85 nm minimum perigee limit for the orbiter. The phase angle at OMS-2 can vary from 37 degrees to 311 degrees for a Flight Day 3 rendezvous and 211 degrees to 505 degrees for a Flight Day 4 rendezvous.

So, those 19º are outside the "average" phase angle bounds for a FD3 rendezvous.

 

[indy91]

From the official FDO MFD thread:

So, those 19º are outside the "average" phase angle bounds for a FD3 rendezvous.

Yeah, and 379° is as well. That's probably why I am having trouble finding a good profile for Tim's scenario. :lol:
EDIT: The issue is that even with a 0 ft/s NC-1 and thus a phasing orbit of 125x85 after OMS-2 there is not enough phasing to be done to reach the ISS at the normal time for a FD3 rendezvous, so TI maneuver at about 001:18:00:00 MET. And in that case you probably will simply do a FD4 rendezvous, not FD2 or FD3.

I found a fun one for a FD2 rendezvous, but that involves doing quite large OMS-2 and NC-1 burns that almost take the Shuttle up to the ISS altitude already. Probably not very realistic.

FD4 should be quite possible. Main issue with FD4 rendezvous is that you would normally schedule those 3 or 8 ft/s placeholder phasing burns on every day, but then the number of maneuvers exceeds the current ability of the MFD to display them all. I guess I will have to add scrolling through a longer list. The original OMP from 1980 could only handle 9 maneuvers anyway, but by the end of the program it seems to support up to 40.

 

[GLS]

I found a fun one for a FD2 rendezvous, but that involves doing quite large OMS-2 and NC-1 burns that almost take the Shuttle up to the ISS altitude already. Probably not very realistic.

Maybe so, but once they planned to rendezvous with a satellite about 30mins after launch, an insanity complete with MECO downrange position controlled by throttling the SSMEs during ascent, so that FD2 scenario isn't that unrealistic.

I guess I will have to add scrolling through a longer list. The original OMP from 1980 could only handle 9 maneuvers anyway, but by the end of the program it seems to support up to 40.

Or if there are still MFD buttons left, you could add pages to it.

 

[Wolf]

Maybe so, but once they planned to rendezvous with a satellite about 30mins after launch, an insanity complete with MECO downrange position controlled by throttling the SSMEs during ascent, so that FD2 scenario isn't that unrealistic.

That would have been something to watch on NASA TV :lol: