[SSU 4.2] RCS Fuel usage and DAP Config

STS

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Hello all


I am testing with SSU 4.2 on Orbiter 2010, and I think I found some issues. Or maybe I am not understanding something.
When looking and the RCS/OMS PRPLT QTY indicators on panel O3, i see that LEFT/RIGHT always shows 99, and the FWD/KIT indicator only decreses when operating the forward jets. When operating the back ones, the indicator does not decrease, but the OMS QTY indicator (when moving the rotary switch) shows a delta. Is this an issue, or the RCS fuel comes from the OMS tanks?


Also, another issue I have is that when using the SPEC20 I can´t for the life of me configure it to use only tail jets. I managed to do it only once on the STS-1 on orbit scenario, but I did it by poking around and can´t remember how I did it...


I made a video about the issues:





One more question: Is the FWD/KIT fuel qty critical for reentry? Because when doing a reentry some days ago, I lost control. The shuttle was unable to keep the attitude, and I think it was because the quantity was zero. But maybe it was for some other reason.


It´s nice to see that SSU has evolved so much! The KU Antenna implementation is beautiful! I can´t wait to test a build of the development of 5.0, maybe very soon! :cheers:
 

Urwumpe

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There are some issues with the implementation and the indicators, that I noticed as well, thank you for testing this more thoroughly as I did. :)

I can't exclude that many scenarios lack FRCS propellant and have to get fixed.
 

DaveS

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To answer the question on whether or not the FRCS was used for entry, the question is no. Prior to entry but after the de-orbit burn the crew executed the FORWARD RCS DUMP procedure on page 3-36 of the generic Entry FDF.

Currently in SSU, this is impossible as were using the same idealized thruster set up from the default Atlantis so only a few of the FRCS thrusters are actually there.

This is also why the orbit DAP is only half-functional, we don't have all the thrusters it expects, so no tail only control or Low-Z DAP modes. Currently SSU is very limited in what it can do. Lots of things are only for show, not function.
 

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To answer the question on whether or not the FRCS was used for entry, the question is no. Prior to entry but after the de-orbit burn the crew executed the FORWARD RCS DUMP procedure on page 3-36 of the generic Entry FDF.

Currently in SSU, this is impossible as were using the same idealized thruster set up from the default Atlantis so only a few of the FRCS thrusters are actually there.

This is also why the orbit DAP is only half-functional, we don't have all the thrusters it expects, so no tail only control or Low-Z DAP modes. Currently SSU is very limited in what it can do. Lots of things are only for show, not function.


I'll work on it. Next well be a fix for the RMS problem.

Not really sure what is next. I want to do some DPS corrections, but I think we also have many more smaller bugs that need to be done. I don't plan doing a multithreaded implementation of the DPS anymore, this opens too many cans of worms regarding saving the state of the DPS in scenario files. There is other work needed that has to be done first, before a new attempt can be made.


Then, I also think an implementation of the flight rules would be great for quality assurance, since this could catch deviations that we are not actively searching for.

And of course, separating animation constants from code would also be a good help for development.
 
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STS

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Thanks for the feedback guys.


I was doing a normal usage of the shuttle when I discovered the issues, wich made me think that I was doing something wrong.



I was flying a full test-mission with rendezvous, and become aware of this as I was starting to manouver for docking and the fuel usage was going "off scale high", on all my attempts to complete the mission. It seems that will be very hard to complete this mission because of this issues... I run out of FRCS fuel...



It´s sad because the DAP is very basic... also the RCS implementation.


If you need help, if I can contribute to the project in some other way different to testing final release versions (I have time for testing things because of the lockdown... but you saw how I test things) make me know. As I said on the dev thread, I could contribute to the code part, but would require a guide to set up the dev environment, and then we could distribute tasks.


This week I can test this same mission but on Orbiter 2016 and on the current SSU version, to see if I find something else. (I will follow the instructions here)
 

Urwumpe

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As I said on the dev thread, I could contribute to the code part, but would require a guide to set up the dev environment, and then we could distribute tasks.


That wasn't that hard with Visual Studio 2019 and checking out from Orbiter-Forum. I can't offer you a more recent guide there, but if you have any questions, I can try helping you. I needed to find it out myself, after just passively reading what happens here.



But even having more people testing SSU and providing feedback is nice, because it makes it easier for me to get back understanding where I actually left. :lol:
 

DaveS

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Another note on the current RCS implementation: The reason why the FRCS propellant seems to be deplete so much quicker than then the ARCS is that currently the ARCS thrusters share the same propellant tank with the much larger and capable OMS. The FRCS only has 2,473 kg of propellant while the ARCS as a consequence of using the OMS propellants have 12,593.5 kg available, that's over 5x as much.
 

STS

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Thanks again for the feedback.


Following the instructions, I was able to test on Orbiter 2016!


photo-2020-05-10-20-01-14.jpg
 

Urwumpe

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Following the instructions, I was able to test on Orbiter 2016!


"That is not the solar sail."

---------- Post added at 20:11 ---------- Previous post was at 20:07 ----------

Another note on the current RCS implementation: The reason why the FRCS propellant seems to be deplete so much quicker than then the ARCS is that currently the ARCS thrusters share the same propellant tank with the much larger and capable OMS. The FRCS only has 2,473 kg of propellant while the ARCS as a consequence of using the OMS propellants have 12,593.5 kg available, that's over 5x as much.


I think we should separate the propellant and pressurant sources as soon as possible, even if the RCS implementation might take some time more. This way, the scenarios could be changed now and not changed in this aspect for a while.
 

STS

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I discovered a workaround to set Tail Only control.


I show it at 49:20 in this video:




The "trick" is that you just need to enter ITM15, ITM16 or ITM19, to cycle the option.


And also, you have to be in PRI. I discovered this by looking at the code. Dont remember exactly the line number and source file. Will post later with this.


This is for the current nightly, but it also works for 4.2
 
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