[1.3.0] Kerbal Engineer Redux 1.1.3.0 (2017-05-28)

[MonaBabii]

Finally installed it Some of the things in this mod are driving me insane lol but it's for the most part fun to learn

Question Cybutek, as I'm used to modding games but KSP is unlike any other lol: In order to update KER I just replace files, right?

Thanks in advance for the reply and the mod itself It's great! But I'm gonna have to continue watching Das for a very long time xD Not that I mind that but.. yeah, I'm so bad.

[cybutek]

Finally installed it Some of the things in this mod are driving me insane lol but it's for the most part fun to learn

Question Cybutek, as I'm used to modding games but KSP is unlike any other lol: In order to update KER I just replace files, right?

Thanks in advance for the reply and the mod itself It's great! But I'm gonna have to continue watching Das for a very long time xD Not that I mind that but.. yeah, I'm so bad.

Yup, just copy/replace. I'm also watching Das by the way

[Gfurst]

Yup, just copy/replace. I'm also watching Das by the way

Das????

Another update? I never thought I would say this ever to a modder, but, would you slow down with those updates???

Just kiddin, keep on having fun and keep them coming. I know I'm liking them changes..

[cybutek]

Das????

Another update? I never thought I would say this ever to a modder, but, would you slow down with those updates???

Just kiddin, keep on having fun and keep them coming. I know I'm liking them changes..

Sorry for the update spam. The next one will hopefully be 1.0.12 with features instead of bug fixes

DasValdez is a Twitch streamer and he's currently streaming on KSP-TV (http://www.twitch.tv/ksptv) right now.

[Phil deCube]

G'day Guys, I haven't been able to find an answer to this (or even a question about it), so maybe it's just something I'm doing wrong, but...

Why is it that when I create a ship with a couple of probes on top, which will be separated and sent to different targets in the long run, that the Delta v for these stages is not shown in the list? The main stages are all listed, but these ones, just seem to be dropped.

Stages 0 and 1 are the ones that I am missing in this picture. The left and right probes on the top.

Mechjeb does the same thing, so I don't know that it is a problem with Kerbal Engineer, as such.

Thanks.

Edited November 11, 2014 by Phil deCube

[Kerbas_ad_astra]

Kerbal Engineer's calculations are dependent on staging order. For example, I've got an Apollo-like rocket with a lander which is separate from the main crew module. However, because it starts out below the crew module, the staging system assumes (and Kerbal Engineer calculates delta-V based on this assumption) that the booster stage lifts the rocket into orbit, and then the lander's descent stage pushes the whole thing, and then the ascent stage fires, and then the crew module's engine fires, when this isn't how it will actually go at all (I can attach pictures tomorrow if it would help). Based on your description, it sounds like the probes fall somewhere between stages, and because the motors are on the "far side" of the decouplers (I assume), Kerbal Engineer sees that they don't contribute to the delta-V of the main vehicle, and so ignores them.

[Phil deCube]

Thanks, I think I see what you mean.

I have put a picture up now, which might explain it better than my description. I guess, from your explanation, that it is because my probes (stages 0 and 1) are attached above the main (original) ship's probe body. Would that be right?

[TedwinV]

Kerbal Engineer's calculations are dependent on staging order. For example, I've got an Apollo-like rocket with a lander which is separate from the main crew module. However, because it starts out below the crew module, the staging system assumes (and Kerbal Engineer calculates delta-V based on this assumption) that the booster stage lifts the rocket into orbit, and then the lander's descent stage pushes the whole thing, and then the ascent stage fires, and then the crew module's engine fires, when this isn't how it will actually go at all (I can attach pictures tomorrow if it would help). Based on your description, it sounds like the probes fall somewhere between stages, and because the motors are on the "far side" of the decouplers (I assume), Kerbal Engineer sees that they don't contribute to the delta-V of the main vehicle, and so ignores them.

So what's the workaround for this? Build all the sections separately with probe cores, get the delta-v's, put them in as subassemblies, and then add the delta-Vs manually when building the main launcher? That seems like a lot of extra work, and I'm not sure if that will still yield accurate delta-v budgets. Is there a way to account for this in the mod?

[MonaBabii]

Yup, just copy/replace. I'm also watching Das by the way

Thanks Yeah I've seen you several times in chat, also asked a couple questions too. Das is the one who indirectly pushed me to get KER I was so intimidated by the mod before, and still am but at least now I know just a little bit more than I think I can probably maybe manage eventually xD

[BudgetHedgehog]

@Phil - because when you decouple the probes, they're no longer part of your main ship. KER calculates the dV that your main ship has and your main ship is the one that the root part is on. It's not calculating the probes dV because they're not contributing anything to the core ship as they're decoupled from it. It won't matter if you decouple them last, KER just sees them as dead weight until they're jettisoned and the dV will show that.

If you want the probes dV, make a part on it the root part. Then KER will calculate the correct dV for it so you can either add that to the original dV or swap staging around so it's the last thing to decoupled.

[Kerbas_ad_astra]

So what's the workaround for this? Build all the sections separately with probe cores, get the delta-v's, put them in as subassemblies, and then add the delta-Vs manually when building the main launcher? That seems like a lot of extra work, and I'm not sure if that will still yield accurate delta-v budgets. Is there a way to account for this in the mod?

It is some extra work, but it does work. It may help to split up your delta-v budget into the delta-V that your booster and transfer vehicle needs to get into orbit around wherever you're going and the delta-V that your probes need to land (that's how I did it for my lander -- so much delta-V for the landing, so much for the return, and so much to get the whole stack to the destination). Then, you can design your probe to meet its delta-V requirement, turn it into a subassembly, and tack it onto your main vessel, and make sure that the booster/transfer vehicle has enough delta-V to get everything to the planet you're exploring. Alternatively, you can choose your various probe cores as the root and see what the new "top stage" has for delta-V, if you want to design everything at once (although you will still have to watch the staging order, and be especially careful if the probe is in the middle of the stack or if the rocket is intended to re-arrange itself).

For changing the root, as ObsessedWithKSP suggests, there's an addon for that: SelectRoot. The short version is that, with this mod installed, you can LeftCtrl+LeftShift+Click a part, as long as it has nodes for stack connection, and make it the new root part, allowing you to prune off anything else and make it into a subassembly. For example, build a probe, then tack a rootable part onto the part where the probe will touch the mothership, make it the new root, and then make a subassembly out of the probe. It seems Squad will make this a stock feature in 0.90, so get ready to make the HypeProbeCarrier!

I'm trying to think of ways for Kerbal Engineer to do this accounting, and my idea basically involves making trees starting from any potential control source and tracing out which rockets can accelerate which core, but that still depends a lot on when various parts get released. How is KER supposed to know if a probe gets released when the fuel tank of its carrier stage is only half-empty? That will affect the true delta-V of the whole stack below it. All of this depends on staging order, and more importantly, mission architecture, which is probably not possible to automatically store, compute, or evaluate in a reasonable way -- if it were, there wouldn't be much need for us aerospace engineers.

[Mystique]

Is it a spot in my knowledge of how rockets fly or KER is calculating stage delta-v in a strange way: I have SRB and LFE as booster stage. If I stage LFE to start right after SRB decouple, KER shows more total delta-v for booster stages than if I stage SRB to start alone, decouple and start LFE in mid-air. Is it normal or am I missing something? Perhaps surface Isp of LFE or something else is also taken into account by KER?

[Padishar]

Is it a spot in my knowledge of how rockets fly or KER is calculating stage delta-v in a strange way: I have SRB and LFE as booster stage. If I stage LFE to start right after SRB decouple, KER shows more total delta-v for booster stages than if I stage SRB to start alone, decouple and start LFE in mid-air. Is it normal or am I missing something? Perhaps surface Isp of LFE or something else is also taken into account by KER?

I'm not actually sure what you are describing. It is most probably correct as KER very carefully simulates the burning of the fuel by the engines (though there are some issues with it not being able to tell when to activate stages but that shouldn't be an issue during launch of a reasonably standard rocket). Can you show screenshots of the KER window (with show all stages selected) in the two situations you are describing?

[Mystique]

I'm not actually sure what you are describing. It is most probably correct as KER very carefully simulates the burning of the fuel by the engines (though there are some issues with it not being able to tell when to activate stages but that shouldn't be an issue during launch of a reasonably standard rocket). Can you show screenshots of the KER window (with show all stages selected) in the two situations you are describing?

Here they are, notice sequence of engines starting and total resulting delta-v:

According to my understanding of how things work, delta-v should be higher when all engines start at once, because otherwise SRB carry dead weight consisting of payload and not working LFE stage.

[Padishar]

Unfortunately it isn't that simple. In both cases the first stage burns for 30.6s (which is the burn time of the solid boosters). In the first example, the second stage then only has 3.2s of fuel remaining. In the second example, the liquid engine has the full 33.8s of fuel.

Yes, when only the solids start at first, the solid boosters are lifting the whole of the liquid stage as "dry" mass but, when they both start together, the liquid engine is having to also push the mass of the solid boosters for all but the last 3.2s of its burn.

The numbers are correct and can actually be verified fairly easily. Load the vessel to the pad and hit X to zero throttle. Turn on infinite fuel and hack gravity. Then, manually enable the liquid engine and fly the rocket straight up out of the atmosphere (70km+) and then turn around and stop it again. Then disable the liquid engine again, disable infinite fuel (but don't turn hack gravity off), point directly away from Kerbin, set throttle to max and hit space to stage the staging. Stage again once the solids burn out and once the rocket stops burning check the speed of the rocket. This should equal your deltaV. Then repeat the process with the other staging setup (or better, quicksave once you get into space and simply reload the save and tweak the staging in flight before "launch").

[Mystique]

Unfortunately it isn't that simple. In both cases the first stage burns for 30.6s (which is the burn time of the solid boosters). In the first example, the second stage then only has 3.2s of fuel remaining. In the second example, the liquid engine has the full 33.8s of fuel.

Yes, when only the solids start at first, the solid boosters are lifting the whole of the liquid stage as "dry" mass but, when they both start together, the liquid engine is having to also push the mass of the solid boosters for all but the last 3.2s of its burn

Stage burn time can be adjusted by tweaking SRB throttle. If LFE and SRB burn at the same time, shouldn't it add the same delta-v as if the burn in sequence? I just want to understand how it works. Don't even remember real world crafts that would first burn SRB and then start the engines (well, maybe it's also because that if engines don't start for some reason, there is no use of starting SRBs - it won't fly far anyway).

[Padishar]

If that was the case then there would be no point in using staging at all. Basically, when you fire all the engines at once, the liquid engine is pushing much more mass and is therefore adding less deltaV. The exact specifics of the calculations are quite involved. The Tsiolkovsky rocket equation itself is fairly simple even when staging is involved but it requires you to have an "effective ISP" value for each stage. Calculating the effective ISP when multiple engines with different ISP values are burning is more complex and involves summing the flow rate multiplied by the engine ISP for each engine and then dividing this by the sum of the mass flow rates for each engine (the mathematical derivation of this is left as an exercise).

I can't easily go into the details in a forum post and I don't know your level of maths ability but I suggest you do some more advanced reading about the rocket equation and try to run through a calculation manually and hopefully it will make more sense...

[Phil deCube]

@Phil - because when you decouple the probes, they're no longer part of your main ship. KER calculates the dV that your main ship has and your main ship is the one that the root part is on. It's not calculating the probes dV because they're not contributing anything to the core ship as they're decoupled from it. It won't matter if you decouple them last, KER just sees them as dead weight until they're jettisoned and the dV will show that.

If you want the probes dV, make a part on it the root part. Then KER will calculate the correct dV for it so you can either add that to the original dV or swap staging around so it's the last thing to decoupled.

Thanks ObsessedWithKSP (my wife thinks that's my name),

I see what you mean. Thanks. I have been fooling around with making subassemblies, but could never get them to match up with launcher stages until yesterday. I discovered I should be building them from the bottom up, not top down, and now I can create a probe as a stand alone, get it's delta v, save it as a subassembly, and then plonk it on my rocket.

So, with the explanations in this thread, and my discovery in another on subassemblies, I'm good to go now.

Cheers

[Drew Kerman]

Thanks ObsessedWithKSP (my wife thinks that's my name),

I see what you mean. Thanks. I have been fooling around with making subassemblies, but could never get them to match up with launcher stages until yesterday. I discovered I should be building them from the bottom up, not top down, and now I can create a probe as a stand alone, get it's delta v, save it as a subassembly, and then plonk it on my rocket.

So, with the explanations in this thread, and my discovery in another on subassemblies, I'm good to go now.

Cheers

You probably can't build top-down because you're not using test weights. You're on the right track with sub assemblies though. See the last link on the right in my sig below for a top-down building guide that removes the need for Engineer to try and figure out what you're doing with your staging. Mystique this could probably apply to you as well.

[Phil deCube]

You probably can't build top-down because you're not using test weights. You're on the right track with sub assemblies though. See the last link on the right in my sig below for a top-down building guide that removes the need for Engineer to try and figure out what you're doing with your staging. Mystique this could probably apply to you as well.

Thanks for that Gaiiden. Reading the link now. Very interesting stuff.

[Hyomoto]

I'd like to make a request. Not sure what this would require, but would you look into exposing certain variables for RasterPropMonitor? The major ones would be stage resources, as KSP does not provide this information correctly. FAR, surprisingly, exposes some of it's variables so it might be possible to see what Ferram did if you are willing to look into it. It is possible to do this with MechJeb as well, but since that isn't a mod I use it isn't one I'd personally support. I've been wanting to get to updating my monitor configurations but this is sort of an impasse for me since it really wrecks some of the choices I made with them.

[starkline]

Hi, I am loving the HUD so far! I have been using VOID for my HUD until now, but there are a few bits of info that it has that KER doesn't have yet that I think would be useful....

...heading/pitch/roll...

It's been a while since I'd looked at Engineer, and I must say the improvements that have been made are fantastic. It has quickly replaced MechJeb custom windows. I'd like to echo Sewer Urchin's opinion that vessel pitch, heading, and roll would be another great addition.

It's always nice to know where you're pointing, and making the nav ball large enough to gauge axial tilt to within a degree or two is just not practical. I also dislike large HUDs when not in IVA (ala Steam Guage). Screen space is just too much of a premium! A few numbers for pitch, heading, and roll in an elegant custom HUD from KER would be sweet.

Anyway, cheers for KER!

[Mystique]

If that was the case then there would be no point in using staging at all. Basically, when you fire all the engines at once, the liquid engine is pushing much more mass and is therefore adding less deltaV. The exact specifics of the calculations are quite involved. The Tsiolkovsky rocket equation itself is fairly simple even when staging is involved but it requires you to have an "effective ISP" value for each stage. Calculating the effective ISP when multiple engines with different ISP values are burning is more complex and involves summing the flow rate multiplied by the engine ISP for each engine and then dividing this by the sum of the mass flow rates for each engine (the mathematical derivation of this is left as an exercise).

I can't easily go into the details in a forum post and I don't know your level of maths ability but I suggest you do some more advanced reading about the rocket equation and try to run through a calculation manually and hopefully it will make more sense...

Err, just noticed that I was wrong while writing my question - I compared one staging method to itself, while describing it with different words

Correct question was:

I have SRB and LFE as booster stage. If I stage LFE to start right after SRB decouple in mid-air (SRB fire, rocket flies, SRB stops, SRB decouple, LFE starts), I get more total delta-v for booster stages than if I stage SRB to start together with LFE on the launchpad and drop SRB in mid-air while LFE is still working (SRB and LFE fire together, rocket flies, SRB stops, SRB decouples, LFE still working for some time).

Though screenshots were correct anyway.

[Red Iron Crown]

I have SRB and LFE as booster stage. If I stage LFE to start right after SRB decouple in mid-air (SRB fire, rocket flies, SRB stops, SRB decouple, LFE starts), I get more total delta-v for booster stages than if I stage SRB to start together with LFE on the launchpad and drop SRB in mid-air while LFE is still working (SRB and LFE fire together, rocket flies, SRB stops, SRB decouples, LFE still working for some time).

That calculation is correct. In the case where you start the LFE after the SRBs are staged away your liquid fuel is spent accelerating a smaller mass, so the same amount of liquid fuel delivers a greater amount of acceleration.

[Mystique]

That calculation is correct. In the case where you start the LFE after the SRBs are staged away your liquid fuel is spent accelerating a smaller mass, so the same amount of liquid fuel delivers a greater amount of acceleration.

Well, I though it over again, it makes sense - the same as if would've added another LFE stage below instead of SRBs on the sides. Question closed