Shuttle FDO MFD

[Wolf]

Sure. It's caused by nodal regression: https://en.wikipedia.org/wiki/Nodal_precession

This effect acts on the orbit of both the Shuttle and the ISS and pulls both orbits "westwards". But this effect is also depending on the altitude of a satellite and it's going to be stronger for a vessel in a lower orbit. Now, the Shuttle spent about 2 days in an orbit that is much lower than the ISS, up to 100NM lower. That's why you get a differential nodal regression between those two orbits. Effectively you need to insert the Shuttle in an orbit that has a Longitude of the Ascending Node (LAN) that is further east. Then it's going to be pushed westwards, more than the ISS. In the case of STS-114 the orbits in this post OMS-2 scenario are:

Shuttle:
Inclination: 51.66°
LAN: 59.28°

ISS:
Inclination 51.66°
LAN: 58.85°

Both LAN values will become lower over time (so more towards west) and when the Shuttle is finally doing the maneuvers that takes it "up" to the ISS orbit the LAN values will be almost identical.

Thanks for the clear explaination Indy :thumbup:

 

[Tim13]

@Indy91 So right now, the Shuttle FDO MFD is scenario specific, as in real numbers from a real mission are the starting point?

Do you envision a time where a user could pick their own launch date/time, and the MFD would then look at the post MECO shuttle state, and the ISS state, and then do a real time calculation of all the burns based on the post shuttle launch data?

I find this MFD to be a very appealing idea to really enhance the immersion of the SSU.

Tim

 

[indy91]

@Indy91 So right now, the Shuttle FDO MFD is scenario specific, as in real numbers from a real mission are the starting point?

Do you envision a time where a user could pick their own launch date/time, and the MFD would then look at the post MECO shuttle state, and the ISS state, and then do a real time calculation of all the burns based on the post shuttle launch data?

I find this MFD to be a very appealing idea to really enhance the immersion of the SSU.

Tim

Right now it loads the launch time and rendezvous plan of STS-126 by default, because that's the mission I used for testing. But you can already change the time and every single thing about the rendezvous plan by hand. It's just a bit inconvenient to do that every time when loading Orbiter. So that will be improved. But in theory (minus bugs) you can already use the MFD with any mission you want and start planning your rendezvous some time between insertion and OMS-2. And it supports any burn after that, just need to delete the first maneuver in the plan whenever a burn was executed and adjust the constraints a bit.

 

[Donamy]

Would this work for another ship ? The Crew Dragon perhaps.

 

[indy91]

Would this work for another ship ? The Crew Dragon perhaps.

The first two displays of the MFD, yes. Maneuver Constraints Table and Maneuver Evaluation Table are both using no Shuttle specific numbers for the calculation. The other displays that are already implemented are Shuttle specific, calculating burn times based on thruster selection etc. But you don't have to use those other displays. All you get in that case is the TIG and DV vector in LVLH coordinates based on an impulsive burn. Not sure how you would burn e.g. exactly 84.7 ft/s in a specific direction in the Crew Dragon though. Is there an MFD for that? In any case I will not add anything to the FDO MFD that would break the rendezvous planning part of it for other vehicles.

 

[Donamy]

There are some MFDs available. Don't know which ones would work with FDO MFD though. :shrug:

 

[indy91]

There are some MFDs available. Don't know which ones would work with FDO MFD though. :shrug:

It's a pretty standard format, TIG in mission elapsed time, DV not in inertial coordinates but in LVLH and in feet per second. That is what PEG-7 of the Shuttle computer used as the input and also the input that the AGC used. Maybe it can be done with the Burn Time MFD or so.

 

[Tim13]

Right now it loads the launch time and rendezvous plan of STS-126 by default, because that's the mission I used for testing. But you can already change the time and every single thing about the rendezvous plan by hand. It's just a bit inconvenient to do that every time when loading Orbiter. So that will be improved. But in theory (minus bugs) you can already use the MFD with any mission you want and start planning your rendezvous some time between insertion and OMS-2. And it supports any burn after that, just need to delete the first maneuver in the plan whenever a burn was executed and adjust the constraints a bit.

Oh, I see.

It looks like it has to be compiled from github. It took me 3 days to get a working copy of SSU up and running by compiling.....LOL.

I think I'll wait until there is a grab and drop version available. My brain can't handle another compiling assault....hahahaha.

I love what you're doing here though.

Tim

 

[indy91]

Oh, I see.

It looks like it has to be compiled from github. It took me 3 days to get a working copy of SSU up and running by compiling.....LOL.

I think I'll wait until there is a grab and drop version available. My brain can't handle another compiling assault....hahahaha.

I love what you're doing here though.

Tim

I put release versions with prebuild modules up on Github as well: https://github.com/indy91/Shuttle-FDO-MFD/releases Here the direct link to the most recent one: https://github.com/indy91/Shuttle-FDO-MFD/releases/download/v0.1.1-alpha/ShuttleFDOMFD.zip

 

[Gingin]

@Donamy : Maybe Imfd would work
I think there is a sub module where we can use LVLH velocities

Great work Indy

 

[Tim13]

@Indy91 thanks for that link!

Tim

 

[Wolf]

@Donamy : Maybe Imfd would work
I think there is a sub module where we can use LVLH velocities

Maybe DVTools MFD could also help?

 

[indy91]

I'm still working on improving the iteration behavior and the nonspherical gravity logic of the MFD. A lot to do for that, but it's getting there. And the MFD still needs to be made more flexible and user friendly for starting a plan for any kind of mission.

Here follows another part of a tutorial of sorts. I'll probably collect these texts and put them in a PDF that comes with the MFD eventually.

Maneuver Types

Maneuvers are added to the rendezvous plan on the Maneuver Constraints Table page. There are a bunch of buttons associated with it:

ADD: add a maneuver. Syntax: "Type Name". Example: "HA OMS-2"
DEL: delete a maneuver. Syntax: "ID". Example: "1"
MOD: modify an existing maneuver, changes type and name. Syntax: "ID Type Name". Example: "2 NC NC-1"
INS: inserts a maneuver at the specified location in the table. Syntax: "ID Type Name". Example: "3 EXDV NC-2"

The real Orbital Maneuver Processor that the Shuttle FDOs used had a whole bunch of different maneuver types, some of them involving a target (e.g. a phasing maneuver) and others are just single vehicle maneuvers (e.g. a circularization maneuver). Not all of them are supported by the MFD yet, but I plan to add them all eventually. Right now the support maneuver types are:

APSO (Apsidal Shift). Simply reverses the vertical velocity at the time of ignition. Most useful is this maneuver when executed at a specific angle from perigee or apogee, but that isn't implemented yet. E.g. if performed 10° before perigee this maneuver would shift the line of apsides by 10°x2 = 20°.

CIRC (Circularization). Circularizes the orbit at the maneuver time.

DVPY/DVYP (Delta Velocity with Yaw and Pitch). If you specify the secondary constraints DV, PIT and YAW a PEG-7 target is build with the specified delta velocity, pitch and yaw angles.

EXDV (External Delta Velocity). PEG 7 maneuver, which needs three secondary constraint inputs DVLV. So e.g. "DVLV=8.0 DVLV=0.0 DVLV=0.0"

HA (Height Adjust). Purely horizontal maneuver, adjusts the height 180° from the maneuver point. The secondary constraint for this is HD (height desired). Often used for OMS-2.

NC (Nth Closing Maneuver). Horizontal maneuver that targets a specific phasing from the target at some future point. Uses the DR (downrange) secondary constraint. The NC-4 maneuver is usually target to occur at 40NM behind the target, so "DR=-40". This is what the first NC maneuver will iterate to achieve.

NCC (Nth Corrective Combination). Lambert targeted, aims for a specific offset to a target in 3-axis. Either as three CXYZ secondary constraints on the following maneuver, or using DH (Delta Height), DR (downrange) and WEDG (wedge angle). This type of maneuver is usually the first onboard targeted rendezvous maneuver
and would target DH=0.2, DR=-8 and WEDG=0.

NH (Nth height maneuver). Similar to NC maneuver, but iterates on a height difference specified with DH.

NPC (Nth plane change). Out-of-plane maneuver to put the Shuttle in the orbit of the target. With nonspherical gravity enabled this will try to achieve a wedge angle of 0 at some future, specified time (WEDG constraint). The optimal TIG for this is the common node (CN) with the target orbital plane, so the secondary constraint "CN=1.0" is usually used.

SOI (Stable Orbit Initiation). Lambert targeted maneuver, needs three CXYZ secondary constraints as the offset. This would apply to e.g. the TI maneuver targeting the offset at MC-4. Always goes together with a SOR maneuver as a pair.

SOR (Stable Orbit Rendezvous). Lambert targeted maneuver to essentially do station-keeping with a target. This maneuver is a convenient end point for a rendezvous plan (e.g. MC-4).

 

[GLS]

Finally got the time to test this!
Coming up on the NC-2 burn, and I decided this to be a single OMS engine burn, and I noticed that the MNVR PAD doesn't show the selected "dV source"... :uhh:

 

[indy91]

Finally got the time to test this!
Coming up on the NC-2 burn, and I decided this to be a single OMS engine burn, and I noticed that the MNVR PAD doesn't show the selected "dV source"... :uhh:

Do you mean that it doesn't show which engine was selected for the burn? It actually does in the code in the first line. For example BPE03NC means:

BP (code for both OMS engines. OL and OR would be single OMS burn with left and right engines)
E: External DV burn, it will always say that right now
03: third burn in the maneuver table
NC: type of burn

Oh, and there is a bug currently with the yaw angle of the right OMS engine on the PAD, if single OMS burn was selected. The RY value probably shows 0° only right now, but it should be the opposite of LY (e.g. 4.2° vs. -4.2°). That will get fixed.

 

[GLS]

Uh oh... I knew that error I made in the OMS-2 burn was going to cost me... I'm pretty sure I'm lower that planned, so the constrain M=15.5 on NC-3 means I'll overtake the ISS. :facepalm:
The only positive is that I saw this early enough to change to M=11.5*, but I'll still get ahead. :shrug:

One thing: could the MET table have lines or a larger gap between the 3 maneuver lines?

*) getting an "Error: Too many iterations" with other M values like 11.3 or 11...

 

[indy91]

Uh oh... I knew that error I made in the OMS-2 burn was going to cost me... I'm pretty sure I'm lower that planned, so the constrain M=15.5 on NC-3 means I'll overtake the ISS. :facepalm:
The only positive is that I saw this early enough to change to M=11.5*, but I'll still get ahead. :shrug:

Even lower than the planned 85NM perigee? :lol:

One thing: could the MET table have lines or a larger gap between the 3 maneuver lines?

I'll try. The page needs to display a lot of information, don't want to limit it to fewer maneuvers being displayed.

*) getting an "Error: Too many iterations" with other M values like 11.3 or 11...

Yeah, a value like 11.3 will move the maneuver points away from the line of apsides, which the iteration won't like. You burned NC-1 exactly two orbits after OMS-2, right? Wouldn't that fix any OMS-2 errors considering it happens at the same altitude as OMS-2?

Did you make the NC-2 burn a NC maneuver or kept it as a EXDV one? If you make it a NC maneuver then it will achieve the right phasing again, so the orginal maneuver plan with the numbers of revolutions between maneuvers might still work.

 

[Wolf]

Hi Indy, as my PC came back to life today I am trying to familiarize with your MFD using an STS-114 scenario where the ISS state vectors should be quite ok. Between other things it is not clear to me how we can modify the burn data (TIG, DV, etc) in the Maneuver Constraint Table. Also I am showing no data on the Maneuver Transfer and Detailed Maneuver tables...
I guess I still have to understand a lot on how to use this MFD

A couple of things I also noticed:

I have a discrepancy about the liftoff calendar day number between the Executive Menu and the Maneuver transfer table (for burns planned on launch day). Maneuver transfer says day #208 where as the launch day was actually on day #207 (as the Executive Menu correctly shows). here the screenshot showing this


Another issue is the calculated HP and required DV for the NC-2 burn. The target HP is 126 NM with a DV of 8 fps: this would result in a HP of only 120NM (since the pre burn HP is 116 NM). To get the target 126NM HP I would expect a calculated DV around as twice as much..
Here you can see the FDO MFDs showing target HP and DV for the NC-2 burn and the target HP in OPS202 showing 120 NM only (which make sense according to the DV used)

 

[GLS]

Even lower than the planned 85NM perigee? :lol:

I remeber seeing 77NM at some point.... :facepalm:

I'll try. The page needs to display a lot of information, don't want to limit it to fewer maneuvers being displayed.

Thanks!

Yeah, a value like 11.3 will move the maneuver points away from the line of apsides, which the iteration won't like. You burned NC-1 exactly two orbits after OMS-2, right? Wouldn't that fix any OMS-2 errors considering it happens at the same altitude as OMS-2?

Did you make the NC-2 burn a NC maneuver or kept it as a EXDV one? If you make it a NC maneuver then it will achieve the right phasing again, so the orginal maneuver plan with the numbers of revolutions between maneuvers might still work.

I think I' following the original plan, the only things I'm doing are recalculating things about 30mins before the next burn, and now I changed the M of the NC-3.
Another thing, and this is a big one: the NPC really messed up the planes, they were +/- correct, and now I've a 0.1º error both in Inc. and LAN... the next burns show a lateral compoment, so let's hope I get there anyway.

 

[indy91]

Between other things it is not clear to me how we can modify the burn data (TIG, DV, etc) in the Maneuver Constraint Table.

My post above about maneuver types should help a bit with that.

Also I am showing no data on the Maneuver Transfer and Detailed Maneuver tables...
I guess I still have to understand a lot on how to use this MFD

The workflow is one display at a time. When you are happy with all constraints, press CLC to calculate the maneuver plan. If successful the results are transferred to the evaluation page. Only then is there anything on that page. If you are happy with the data on the evaluation page press TRA to transfer the data to the next display. On the transfer page you select thrusters and pressing EXE will make the data available for the Detailed Maneuver Table. There you select the maneuver you want data for with the MNV button and then calculate the numbers on the PAD with CLC.

I have a discrepancy about the liftoff calendar day number between the Executive Menu and the Maneuver transfer table (for burns planned on launch day). Maneuver transfer says day #208 where as the launch day was actually on day #207 (as the Executive Menu correctly shows).

Yep, I had noticed that as well. It's fixed in my local copy, will be in the next update.

Another issue is the calculated HP and required DV for the NC-2 burn. The target HP is 126 NM with a DV of 8 fps: this would result in a HP of only 120NM (since the pre burn HP is 116 NM). To get the target 126NM HP I would expect a calculated DV around as twice as much..
Here you can see the FDO MFDs showing target HP and DV for the NC-2 burn and the target HP in OPS202 showing 120 NM only (which make sense according to the DV used)

The maneuver table doesn't make much sense. Why is there a -55 ft/s OMS-2 burn? The initial orbit had 188NM apogee? So you likely didn't use a scenario from before OMS-2. Which is fine, you would just need to delete the OMS-2 burn from the plan. But then the rest probably will also not make much sense. The maneuver plan definitely needs adjustments for each mission.

I think I' following the original plan, the only things I'm doing are recalculating things about 30mins before the next burn, and now I changed the M of the NC-3.
Another thing, and this is a big one: the NPC really messed up the planes, they were +/- correct, and now I've a 0.1º error both in Inc. and LAN... the next burns show a lateral compoment, so let's hope I get there anyway.

Are you using nonspherical gravity? I can't recommend that yet with the MFD. The procedure is to delete the first maneuver from the constraints table after it was executed. The first maneuver in the table needs a time as the threshold, so what you can do is copy the TIG from the evaluation table for e.g. the NC-1 maneuver and use that as the new threshold for it, instead of M=2.0. The same procedure applies to NC-2, but in that case the maneuver was a placeholder, targeted as 8.0 ft/s fixed. So when NC-1 is done you should change the maneuver type of NC-2 to a phasing burn (NC), so that it can correct any errors in phasing that happened so far. In the process of the mission you will eventually have most maneuvers at a fixed TIG.