ferram4 changed the topic of #RO to: Welcome to the discussion channel for the Realism Overhaul (meta)mod for KSP! Realism Overhaul Main Thread https://goo.gl/wH7Dzb ! RO Spreadsheet http://goo.gl/Oem3g0 ! Code of Conduct http://goo.gl/wOSv2M ! | Maximal & soundnfury's RP-1 Race Into Space Signup: http://bit.ly/2DEVm2i [15:01] <soundnfury> Straight Eight Stronk (and) RP-0/1 is basically "Space Agency Spreadsheet Simulator"
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<schnobs>
compare to NTRS 19720007150.pdf, page 74
<Raidernick>
i saw that PR
<Raidernick>
thanks for doing that
<Raidernick>
those srbs have been a mess for a long time
<Raidernick>
and yeah i know there were multiple grain shape configurations for the boosters
<Raidernick>
can you make it whichever one was used most often?
<schnobs>
All three in that plot use the same thrust:propellant curve, just running at different thrust levels.
<Raidernick>
ah
<Raidernick>
i'm assuming green is the standard
<schnobs>
yes.
<Raidernick>
ok then use that
<schnobs>
Well, "standard" -- the one that was considered for MOL.
<Raidernick>
the image in the pdf even says it's standard
<Raidernick>
on page 74
<schnobs>
yes.
<Raidernick>
although the end of the curve there look a bit different
<Raidernick>
the image sucks unfortunately
<Raidernick>
starting from 120 seconds i think?
<Raidernick>
and the start also
<schnobs>
Come again?
<Raidernick>
the shape of the curve
<Raidernick>
the "standard" curve
<Raidernick>
is different than the one you just sent me
<schnobs>
I've got the hump a bit too soon, i think.
<Raidernick>
it has a sharp jump in thrust at ignition in the pdf
<Raidernick>
and the last few seconds of thrust seem to flatten out before droping more sharply
<Raidernick>
the rest of the curve looks good
<schnobs>
Yeah, that's a PITA to get right. As are the wobbles at the end of the tailoff.
<Raidernick>
btw the srmu one is good
<schnobs>
The main curve doesn't quite fit yet either. Getting there.
<Raidernick>
so you don't need to make a pr for that too
<Raidernick>
unless you don't like how that guy did it?
<schnobs>
One could almost re-use the 1205 curve at different thrust. Only that the main hump on the 1207 lasts 30sec, on the 1205 it's only 20sec.
<schnobs>
Nah, what i came here to ask:
<Raidernick>
if you think reusing it is better than doing it again from scratch that's fine too
<schnobs>
Given that the cuvres for different thrust levels all work quite well, and can be set by the user using the SRB thrust slider...
<Raidernick>
one srb that you definitely CAN reuse it for is the ua1206
<schnobs>
I wonder if one shouldn't make just one config and leave it to the user?
<schnobs>
Would it be possible tha the main slider is set to 90% by default?
<Raidernick>
maybe
<Raidernick>
but that's going to cause issues with multiple mesh files
<Raidernick>
or mods that use mesh changes
<schnobs>
?
<Raidernick>
i think it's best to just have them separate
<Raidernick>
however they CAN adjust the thrust to match one of the other curves for the same booster
<schnobs>
I can of course make three different configs that have only differ in rated thrust.
<Raidernick>
yes
<Raidernick>
that's what i think is best
<Raidernick>
don't try to combine the configs
<Raidernick>
i wish that RF had an srb config manager similar to what ti uses for liquid engines
<Raidernick>
then you could combine similar ones like this
<Raidernick>
but without that keeping them as separate files and just changing the thrust is best
<schnobs>
I'm totally unsure about the 15xx boosters.
<schnobs>
I guess I could re-use the 12xx curves -- from what I gather, nearly any curve could be built into a SRB. So it wouldn't be wrong, per se. But... I'm not happy with that approach.
<Raidernick>
does that report now have any example curves for those?
<Raidernick>
not*
<schnobs>
That one's only about 1205 and 1207.
<Raidernick>
ah ok
<Raidernick>
i didn't look further into it than that pages about the 1207
<schnobs>
The only thing dealing with 15-foor SRMs I could find, was UA advertising possible solutions for space shuttle boosters.
<Raidernick>
since that's what i was looking for
<schnobs>
Those all have very flat and long curves, 130sec.
<schnobs>
Don't look anything like what eventualy was on the shuttle.
<Raidernick>
i don't know then
<Raidernick>
you might need to just fudge the numbers to come up with something
<Raidernick>
i wouldn't copy the ua12 booster curves
<schnobs>
Well, it will certainly look similar, but probably not quite the same.
<Raidernick>
is there any information on grain shape?
<schnobs>
in the 12xx doc? Yes.
<Raidernick>
can you use that to "guess" but change the length of it to come up with something for the other boosters?
<Raidernick>
I'm assuming they'd use a similar shape
<schnobs>
Me too.
<schnobs>
Nutshell: 5 or 7 circular sections, plus aft and nose section.
<schnobs>
Only the nose section had a star cut.
<schnobs>
That's the hump at the beginning.
<schnobs>
1207 had a larger nose section ("forward closure"), hence the hump lasts longer.
<schnobs>
Remaining adjustments com from burning the main sections either only inside out, or from one or both fore/aft ends as well.
<schnobs>
That's the meanin of "both ends restriced".
<Raidernick>
ok
<schnobs>
further variations would be possible by having slower and faster burning propellant in different sections, but I think they only considerd cases where the forward closure was the odd one out.
<schnobs>
Grrr. 156-in SRMs were MOL/LUNEX. Hence DoD, not NASA.
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<Raidernick>
schnobs, pap plans to release RO tonight
<Raidernick>
any chance you can get that ua1207 curve done
<Raidernick>
i'll be merging your PR very soon
<Raidernick>
i'm testing the other curve ones now
<Mike`>
schnobs nice work, but where are the tangents? :(
<Mike`>
But yeah you discovered an issue with their calculation which apparently happens when the data points are too close and/or the section is flat. Will investigate that some more later i think.
<Raidernick>
@Mike`, the release is tonight
<Raidernick>
if the fix needs to be in that it has to be done within the next 6 hours
<Mike`>
That's fine
<Mike`>
it doesn't
<Raidernick>
the ua1207 one does
<Raidernick>
that booster has the issue with internal temp
<Raidernick>
that some of the others did
<Mike`>
oh, yeah, i meant my tangent fix doesn't have to get in. :) About the ua, yeah, that really should get fixed if it has temp issues.
<Raidernick>
the curve is just bad
<Raidernick>
it's totally wrong
<Raidernick>
i don't know where it was copied from
<Raidernick>
probably a much smaller booster
<Raidernick>
they also remain at 100% thrust the entire time
<Mike`>
in theory i could create a curve in an 30-60 mins i guess but i'd rather want to sleep as it's late here.
<Mike`>
Isn't it an option to just delay the release a day or two and you could press the button then in case the curve's not getting ready?