Overengineer1

@DerekL1963 Yes, it will learn from that, provided you go all the way to atmosphere exit before you revert.

@Jim DiGriz: The whole point of this mod is that we don't have to have these kinds of hypothetical discussions about a set of principles that interact with each other in overwhelmingly complicated ways. We can just test them and see what works the best. I did 4 runs with the same ship, different Sensitivity values: 0.01, 0.1, 0.2, and 0.5. There was no remarkable difference in any of them, all had around 1000 loss, with a difference between them of less than 1 percent, well under what we'd consider a statistically significant difference. Anyway, the Oberth effect doesn't work that way. It's not about being closer to the planet, it's about traveling faster: a rocket can be more effective when traveling at high speed. If you're in orbit, then the point where you're traveling fastest will be where you're closest to the planet. But when you're launching, the opposite is true.

@mcirish3 Setting the sensitivity lower mostly just makes the launch take longer, without increasing efficiency. A zero setting often (always?) causes the engine to kind of flutter on and off during the tail end of the launch, which just feels like a horrible idea even if I've never seen it cause an issue. The recommended setting is 0.2 which seems like a nice middle ground without sacrificing fuel.

One of the 1.2.2 changes to pitch corrections had an unintended side effect during the initial launch. I'm still working on version 1.3 which has some great new features, but in the meantime I'm releasing 1.2.4 to fix that pitch correction issue. You should all find that your lower TWR rockets launch much more smoothly and a bit more efficiently with this. CKAN should pick up the new version within a few hours of this comment.

@legoclone09 That's way out of line with what the mod works. "Find the most efficient launch" is a lot easier to type than to actually do without actually launching, since there are so many variables involved. I'm able to do what I can do with throttlable engines because that throttle takes a huge variable out of the equation, we can have exactly as much acceleration at any given second as we want. If you take that away... well, then you don't need GravityTurn. There's nothing for me to do if there's no throttle to control, except all the guess work to set the initial turn angle, which is just WILD speculation already. TL;DR: No, I don't feel like I can be a lot of help with RO launches.

@Jim DiGriz There's no code specifically for that. That's a side-efffect of the minimum throttle.

@Suppressor It has to do with how the mod is handling low-TWR designs. Specifically, when it thinks it will be behind the target position for more than 20 seconds, it will pitch upwards a bit as allowed by dynamic pressure. So in your case and in the other guy's case where you won't hit the initial desired AP time for well over a minute, the mod is scrambling to catch up to where it thinks you want to be. There are a number of different ways to address this in the settings that will all have different effects on the overall outcome. This behavior has great benefits later on in the launch when your hyper-efficient 0.5TWR upper stage ends up not crashing into the planet, but takes some adjustment for a slightly lethargic lower stage. The upcoming version (currently available in the dev branch on Github) will "learn" from previous launches and make more/less aggressive settings based on the previous best result. This is done per ship name, and it excludes the default "Untitled Space Craft" name since that would cause a lot of unwanted guesses. This has a lot of serious implications in a lot of cases, like occasionally burning your ship up on ascent. In general it iterates towards horrifyingly fireball-like ascents, because those are the most efficient, and this is the desired behavior that I will keep. I am working on making it quit while it's ahead and learn when to stop instead of going just one launch too far. With my 1.25m test rocket, the second guess launch had improved over the first by 60m/s, the next another 40. If your rocket is not currently engulfed in flame during ascent, then your improvements will probably be more dramatic. Let me repeat that this is still in development, and while it does seem to work pretty well, you still have to hold its hand a bit or you'll end up catching a bit too much fire. The below image is not too much fire, this is in fact a very efficient launch for that particular design, and 100m/s better than any guess settings in previous versions:

@Shalfar The rocket in question is lower than that at 1.4 TWR, and stages halfway through the lift to even lower TWR. Falcon 9 starts at 1.5, and only goes up from there during the first (out of 2) stage.

@KerBlam So, like I said already, your ship is underpowered for the settings you have entered. I already told you the settings to change. The sudden shift in angle of attack is actually a shift to zero angle of attack to orbital prograde. Check it yourself. The mod is trying to reach 40 seconds Time To AP, because you told it to, and it's trying to get there as soon as possible, because you told it to. Your ship is not capable of doing that before 1 minute and 30 seconds into launch, which is an extremely slow launch. Your lifter stage is only 1.4 TWR, and that goes down almost immediately in the next stage, so it's no wonder that the mod is having trouble keeping up with the default settings. Your ship has a lot of non-stock parts, so I'm not able to load it. But I think a Hold AP Time Start of 30 seconds, and a Hold AP Time Finish of 60 seconds is a good place to start.

@KerBlam Yes, reentry effects while ascending are definitely desirable, I see them on all my most efficient launches. If you want to get to orbit having burned <3000m/s, you will absolutely see heating effects, and that's a very routine number for GT. Bump your lower stage TWR up to 1.8 (atmo, not vacuum) or so, sacrificing some of your upper stage TWR down to 1.0 (vacuum) if you have to. Then compare the actual numbers, either remaining fuel or remaining m/s from KER.

@KerBlam Some of your issues sound like you just have a very low TWR rocket: flying vertical for a long time, suddenly changing to orbital prograde at 22km, this is because you are going so slow and not able to go faster. The mod is trying to do what you told it to do, and your ship just isn't capable of it. You probably want to decrease your start angle (so you don't end up burning up), decrease your Start AP Time, and increase your Finish AP Time so that the mod isn't trying and failing to keep up with settings that your ship is not capable of. The rest of your issues are just your own misconceptions about what the most efficient launch path will be. No, leveling out at 50km is not more efficient. The atmospheric drag above about 38km is miniscule, and the increased vector loss and gravity drag from burning up higher to 50km will way more than take up what you save in air drag. I mean probably by 10 times, you will lose 10 times as much fuel by shifting your curve higher than you save by reducing air resistance. With just about any rocket-shaped rocket, you will burn up before you find a curve that is too low to be efficient. If you want to burn all the way to AP, then you need an upper stage that has an unreasonably low TWR. This is just not reasonable to accomplish in an efficient way with a planet of Kerbin's dimensions. If your curve tops out at 70km, then sure, your PE will be about 70km when the burn stops. But this will burn a lot more fuel than necessary. I have done a LOT of testing on this, and I have all the numbers to back it up: Having your curve top out at 40km and slowly climbing to an 80km AP halfway around the planet from where you launched is in every reasonable case by far the most efficient launch path with a stock atmosphere. If you want the mod to overshoot the AP to get a higher PE... Well, no, I'm not going to do that. The mod is going to do what you tell it to do. If you want it to overshoot 80km, then you need to tell it to go to 85km.

@KerBlam I don't mean to say that higher TWR launches are better. But GT is able to make better use of higher TWR to avoid some of the losses. It's a more efficient launch for a less efficient ship, at the end of the day you'll have burned more fuel. Like I said above, in my extreme example that ship burns enough fuel to send a dozen smaller ships to orbit.

@KerBlam The x-axis is horizontal distance, but it's not surface distance, it's orbital. You start at launch with 175m/s of horizontal velocity because the planet is spinning. What you describe as holding a 5 degree AoA is not a gravity turn. That's just a turn. That 5 degrees causes you to present more of your vessel to the wind, so it increases your air resistance. It also spends some of your thrust changing direction instead of going faster, which is wasteful. The shape of the curve depends entirely on the capabilities of the ship. Ships with very high TWR can indeed follow a nice smooth curve. This one has a launch TWR of 4.0, and gets to orbit in only 2840m/s, just barely avoiding overheating, and uses a very aggressive turn of close to 30 degrees at 10m/s: This is an extreme example. I would hardly call this rocket efficient; even though it only uses 2800m/s, it only carries a single Kerbal and burns enough fuel to send a dozen 1.25 meter ships to orbit. The example you picture however is a very low TWR rocket, so the mod decided it was not able to pitch down without risking falling. With a TWR even as low as 2.0 GT is able to make a launch curve that looks similar to the one here. What you describe as an aggressive angle of attack is not actually an angle of attack. You are at an altitude where the atmosphere starts to really thin out. Because you're going so slow, the dynamic pressure on your vehicle fell below the default cutoff of 2500, so the potential for atmospheric drag is very low. At this point the craft changes from surface velocity to orbital velocity. The angle of attack is zero throughout the entire launch with the exception of the initial turn. A faster ship will maintain a higher dynamic pressure for higher through the atmosphere. We switch to orbital prograde as soon as possible because, like I said earlier, every bit of thrust we spend in a direction other than prograde is wasted. To be more specific, every bit of thrust we spend in a direction other than orbital prograde is wasted. Your slow ship does it a bit earlier than average. If you want to do it later, set a lower pressure cutoff. However I doubt that would make your launch more efficient.

Of course they do. /home/<username> is a direct parallel to C:\Users\<username> (or C:\Documents and Settings\<username> for you XP users) In either case I won't be writing any logs there, as KSP takes care of the file path building for me.

Minor update 1.2.3. The autopilot will now continue when the window is closed, and the flight map now includes axis labels.

@linuxgurugamer I'll try to get some numbers in there. Writing text to a dynamically generated texture is not something that is handled very well by Unity, as far as I can find, so maybe I can get something on the outside. The y-axis is altitude, just as you guessed, and it goes from zero to atmosphere depth, or zero to destination height if there is no atmosphere. The x-axis is not time, it's horizontal distance. I'm keeping the current behavior of overlapping itself, because the x and y axis are using the same meter-to-pixel scale, which I think is more useful from a data point of view than dynamically shrinking the x scale as the flight progresses. Originally the map is meant to chart the ship's capabilities to improve the guessing mechanism for a particular ship. Red represents the percent of critical heat for the part closest to critical temp, green is atmospheric drag, and blue is the percent of thrust compared to the ship's overall maximum (usually the first stage full throttle). If I save the map for a particular craft ID (or design name, I haven't decided), I can parse it at launch time and decide if I want to increase or decrease the aggressiveness of the profile based on previous results. It also looks pretty, so I figured I'd go ahead and display it to the user.

To those that call this mod cheaty, that definitely can be true. But it really depends on how you use it. The first build of this was just for my own use. The first release got a lot more attention than I was expecting, so now it's no longer just my personal tool. Being able to repeatably send a rocket on an efficient launch path is the most scientific way to evaluate small or even large changes to your ship, settings. or habits. How important is it to get higher, sooner? GT tells us not only is it not important, it's actually a bad idea in a lot of cases. How important is aerodynamics during a launch? My readouts tell me it's not important enough to justify very much weight gain at all. How bad is it if we see a little fire during ascent? GT proved to me that not only is it not bad, but it's guaranteed to be my best launch profile for any but the most underpowered rockets. If you're a beginner, it can teach you how you should be launching. If you're an intermediate player, it can take the tedium out of resupply missions without sacrificing efficiency. If you're an advanced designer, it can take human error out of design evaluation. I think I'm a little bit of all three of those, so it helped me with all three.

@sarbian Thanks a lot. That's a shocking vulnerability for cross-mod interference. Version 1.2.2 released with a fix that should resolve a lot of compatibility complaints. Should update to CKAN automatically some time tonight.

@rekrats Obviously one of the other mods is messing with the calculations. It's hard to support or troubleshoot with so many other mods all potentially messing around with the atmosphere specs. If you were able to pin it to one mod that causes a conflict, I could take a look. But I know lots of other users use GT with FAR with good results.

@Karyn451 I think it's possible to do a gravity turn with kOs, but making a script that is general purpose and configurable and handle all the different situations that this mod handles... It would be a lot of work for someone.

@linuxgurugamer You can't please everyone every time. Some crafts are just too hard to auto-detect. It would be a little hard for me to make the code know whether or not it should reduce throttle just because the thrust would be out of line with the center of mass. If you have specially designed crafts, you'll need specially designed GT settings. I think setting a higher Hold AP Time Start is what you'd be after here, that would cause GT to maintain full throttle for longer.

This has a lot more to do with the specs of your vessel than with anything else. For a burn that long, your TWR has to be extremely low. Most engines are not capable of throttling that low without cutting out, so you'd need a very low TWR stage. This would be much easier in RSS where the velocity requirements are much higher. If your ship is designed properly with a low enough TWR, then this is exactly what GT would do.

@m4ti140 No, that doesn't sound like it would fit with how GT works. The turn isn't ever finished, it just blends into an orbit, which is still turning. The "finishing" time as you probably think of it would be impacted by the Sensitivity setting, higher settings may be slightly less efficient but will climb faster during the final part of the ascent. I don't recommend prioritizing time-to-space in this way, though. I generally just let the gravity turn run its course and do a 4x physical warp until atmosphere exit. GT is configured to stop all time warps when it hits space.

@mcirish3 If your lower stage is underpowered, there's not much I can do for you. GT won't get you off the ground if you can't get off the ground. If your upper stage is underpowered, then GT will still get you into orbit if at all reasonably possible. It pitches up if it finds that you are at max throttle and still at risk of falling. It's even possible to fall back down for a while before building enough speed to climb again, and GT will carry on flying through that. Some designs that have to be launched this way are actually extremely efficient, and if you spend a lot of (successful) time in RSS you will almost certainly see it.

@rriegner I put in a pull request 6 days ago. It's still pending.