egg changed the topic of #principia to: Logs: https://esper.irclog.whitequark.org/principia | <scott_manley> anyone that doubts the wisdom of retrograde bop needs to get the hell out | https://xkcd.com/323/ | <egg> calculating the influence of lamont on Pluto is a bit silly…
Guest38395 is now known as raptop
_whitelogger has joined #principia
raptop has quit [Ping timeout: 190 seconds]
<queqiao-> ⟨mad_hazelnut⟩ Greetings! Is this a bug I should be reporting or just more things I should learn? Why don't the burn times match?
<queqiao-> ⟨ezsnack⟩ Did you click active engines before decoupling the previous stage?
<queqiao-> ⟨mad_hazelnut⟩ *before decoupling? I'm not sure I follow. The planning was started as the vehicle was exactly as pictured.
<queqiao-> ⟨mad_hazelnut⟩ so looks like a bug?
<queqiao-> ⟨kuzinat0r⟩ If you click "Active angines", does it change anything?
<queqiao-> ⟨mad_hazelnut⟩ nope
<queqiao-> ⟨mad_hazelnut⟩ well, unless I switch to RCS, in which case it then changes back to 61 s.
<queqiao-> ⟨mad_hazelnut⟩ * it, first changes to some huge number, of course,
<queqiao-> ⟨mad_hazelnut⟩ * first,
<queqiao-> ⟨ezsnack⟩ Aaaah i see maybe. The 2 solids that you have still on your craft even tho they have already fired are confusing principia
<queqiao-> ⟨mad_hazelnut⟩ I can redo the plan, without the solids
<queqiao-> ⟨mad_hazelnut⟩ let me try.
<queqiao-> ⟨mad_hazelnut⟩ * try (but it would still be pretty bad if this were the case).
<queqiao-> ⟨mad_hazelnut⟩ * case, so I'd still report it).
<queqiao-> ⟨mad_hazelnut⟩ The same thing happens with a "clean" stage.
<queqiao-> ⟨makoivis⟩ So what’s the best way to go about using solid engines for flight plans? Plan using instant impulse and fire a bit before the node?
raptop has joined #principia
raptop has quit [Ping timeout: 207 seconds]
raptop has joined #principia
<queqiao-> ⟨mad_hazelnut⟩ don't know about "best" but that's certainly how I did it. Moreover, seeing that the liquids are buggy too, I'm thinking I should use instant impulse for those too..
<queqiao-> ⟨makoivis⟩ Buggy how?
<queqiao-> ⟨mad_hazelnut⟩ See my two messages above
<queqiao-> ⟨makoivis⟩ Ah you have separation motors?
<queqiao-> ⟨mad_hazelnut⟩ I do. In a different stage.
<queqiao-> ⟨makoivis⟩ Principia does not like when you have those still hanging around, it’s vastly preferable to decouple them after use
<queqiao-> ⟨makoivis⟩ Or that’s how I work around it at any rate
<queqiao-> ⟨makoivis⟩ It’s the only workaround I’ve found
<queqiao-> ⟨mad_hazelnut⟩ even if they are in a different stage you mean?
<queqiao-> ⟨makoivis⟩ Yes, if the used up separation motors are still attached, Principia will consider them as active engines and will account for their thrust
<queqiao-> ⟨makoivis⟩ Alas you can’t deactivate solids. Patches welcome, one presumes
<queqiao-> ⟨captainswag101⟩ I wonder if it might also be because solids tend to burn out with a tiny bit of residual fuel left over, as well?
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ Yeah, and they’re still on
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ So they effectively never shut down
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ Does Principia actually care about fuel levels/staging in its maneuver calculations, or is it just what engines you have active when making the plan? I’ve never checked
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ I guess one could code a module that automatically shuts down the engine when it runs out of fuel?
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ of course it would not be restartable, a module made specifically for one-shot engines
<queqiao-> ⟨makoivis⟩ What engines you have active when making a plan. When I make a plan that covers maneuverw after staging, I use instant impulse as the placeholder and adjust the plan after staging with a rebase
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ I meant more if you stage in the middle of a burn
<queqiao-> ⟨makoivis⟩ This and finally figuring out alternative flight plans has been a pretty big deal
<queqiao-> ⟨makoivis⟩ Oh yeah no it doesn’t like that at all
<queqiao-> ⟨makoivis⟩ When I have to do that, I just use an instant impulse burn right after the first burn. This is usually not something that I encounter unless I’m doing something like launching a probe with centaur + star-48
<queqiao-> ⟨makoivis⟩ So the way I do it it goes as follows. TJI burn includes thrrr stages: a centaur, a Star-48 or similar solid stage, and the thruster on the probe.
<queqiao-> I plan the TLI maneuver as one burn only first using the optimize function to get the flyby.
<queqiao-> Then I duplicate the plan and start splitting it up. I subtract from the first burn until it’s within the dV limit of the centaur, then add an instant impulse burn internally locked like two minutes after the end of the impulse burn, and finally an active RCS burn after the impulse burn to get a ballpark figure.
<queqiao-> ⟨makoivis⟩ I do the centaur burn, spin up, fire the solid motor, and then do the correction turn with the probe’s engines.
<queqiao-> ⟨makoivis⟩ It works reasonably well.
<queqiao-> ⟨makoivis⟩ Maybe I should do a write-up: this does work really well and lets you use the optimize feature still.
<queqiao-> ⟨makoivis⟩ Anyway the idea of using instant impulse as placeholders for splitting up burns is powerful and worth messing about with.
<queqiao-> ⟨makoivis⟩ Oh huh the stable inclinations for lunar orbit are _really_ stable
<queqiao-> ⟨makoivis⟩ I have some relay satellites I forgot about at 50 deg and 5000kn altitude and they’re merrily staying in orbit years later with no station keeping
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ Yeah
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ I think a satellite that coincidentally was almost in a frozen orbit lasted about two years irl?
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ something that was intentionally in one would probably last a long long time
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ I forget does altitude matter for those or just inclination?
raptop has quit [Ping timeout: 190 seconds]
<queqiao-> ⟨makoivis⟩ Both, there’s a few papers on it and ~5000km apsis was near enough to one of the frozen semi major axes
<queqiao-> ⟨makoivis⟩ Also easy enough to target and remember 🙂
<queqiao-> ⟨makoivis⟩ Would you look at that, they’ve already done the work on viable comms constellations
raptop has joined #principia
<queqiao-> ⟨makoivis⟩ But yeah one of the frozen inclinations and arg of Pe at 90 or 270 will permit quite a bit of leeway apparently