[1.8.1 - 1.10.1] BoostGuidance v1.0.1

[Kerbal Productions]

9 hours ago, oyster_catcher said:

I'm not sure. Could you make a short video? That would help see the problem.

Here's a G-Drive link: https://drive.google.com/file/d/1FuviXsdbTQkzY0EjWcx_-J2KyXTcGRFD/view?usp=sharing

I commonly decouple them at 72000 km

[oyster_catcher]

7 hours ago, Helvica_Ring_Scientist said:

Here's a G-Drive link: https://drive.google.com/file/d/1FuviXsdbTQkzY0EjWcx_-J2KyXTcGRFD/view?usp=sharing

I commonly decouple them at 72000 km

Thanks, thats very useful. Its great to see people using the mod. I have a few suggestions.

(1) You kept all engines enabled for boostback. This makes for the mod to reduce thrust enough to delicately reduce the minimum target error when it gets small since checks are only done 10 times/sec. Use fewer engines for boostback, re-entry and landing burn as the booster is much lighter and is super-sensitive to thrust (I set up an action group to toggle nines). Your video didn't show what the final target error was at the end of boostback. Take a took at this, it'd be good to see how low it gets.

(2) You were quite ambitious with a boostback burn so far away from the launchpad. The re-entry burn is nearly horizontal. I would expect the re-entry burn to be 20 degrees off vertical max for good accuracy. Because the trajectory is very horizontal prediction of aerodynamic drag makes the landing spot very prone to error (you can see that if the aero-drag calculation is wrong with a vertical trajectory then the prediction error on the ground won't change much). The landing was 126km off target was is embarrassingly bad though I couldn't tell if this was an overshoot or undershoot. It is possible to get the landing error to a few metres. Staying a bit closer when doing boostback will make it easier for the mod to be accurate.

(3) Again because of the large number of engines with high thrust and landing burn thrust is applied very late (even though landing burn is enabled many seconds earlier thrust is not applied). With fewer engines the landing burn will span over more time and will work more accurately.

(4) Raising the "touchdown margin" in the advanced tab by perhaps by 30-40m will help, even if you do nothing else. It looked like the booster hit the ground at 80-90 m/s and decelerating at perhaps 40m/s/s so it needed just 2 extra seconds of deceleration.

On (4) I'm working on making the landing burn more accurate for high thrust rockets. I've learnt some more things

- Upping the rate of thrust calculation estimate from 10 per sec, to the maximum physics rate

- The vessel altitude given from the probe corer rather the origin of the booster of the CoG. This meant some of my calculations were off.

- Upping the gain of the throttle. So the throttle will re-active more rapidly of the booster is travelling too fast. The gain can't be too high otherwise the throttle will oscillate around the required amount.

The first change was in v1.1.0. The next changes are coming soon along with a full tutorial.

I hope you get it working a bit better.

[Kerbal Productions]

Ok sure. Testing this out ASAP.

[Kerbal Productions]

I noticed that the landing burn is done at 500m, which brings my booster tumbling when it's on land, or having a hard impact when it's at sea. What's wrong?

Edited January 17, 2021 by Helvica_Ring_Scientist

[NiL]

Do anyone know how much dV you need (in general) to land with this mod? 

[Kerbal Productions]

8 hours ago, NiL said:

Do anyone know how much dV you need (in general) to land with this mod? 

It's not really dV that you need. It's just m/s. dV is used for interplanetary travel. But it's just landing a booster back on Kerbin.

The mod itself will do the boostback and stuff so your booster lands in one piece.

[oyster_catcher]

7 hours ago, Helvica_Ring_Scientist said:

It's not really dV that you need. It's just m/s. dV is used for interplanetary travel. But it's just landing a booster back on Kerbin.

The mod itself will do the boostback and stuff so your booster lands in one piece.

Thanks for answering. Correct.

It depends on the reduction in velocity you need for re-entry burn plus landing burn. If you don't need the re-entry burn then you just need enough dV is bring your booster from terminal velocity need the ground to a stop (if on Kerbin), these depend on the settings and fast your booster is going at the reentry burn so its complicated.

However the mod would be able to do a rough calculation of dV, but calculating the how much fuel is used looks complex and I have up on that.

For now its not possible, you just need to experiment and get a feel for it.

On 1/17/2021 at 2:40 AM, Helvica_Ring_Scientist said:

I noticed that the landing burn is done at 500m, which brings my booster tumbling when it's on land, or having a hard impact when it's at sea. What's wrong?

Do you think 500m is high enough? If not raise the touchdown margin to give me time.

If its just the tumbling thats the problem I would pull the steering gain for the landing burn all the way to the left so it just steers retrograde, this should stop the tumbling. I've be pleased to see if this work. If you are able to make a video (make sure you include the BoosterGuidance main window) that'd help me diagnose it. Also, I've found a few bugs in v1.1.0, v1.1.1 is coming soon which will be more accurate.

[Kerbal Productions]

I suggest you add a feature that adds a time when to do the boostback or stuff so we accurately land.
I would love that, and it would be highly helpful for me.

[oyster_catcher]

v1.1.1 released

Basically quite a few accuracy improvements and bug fixes. v1.1.0 had quite a major bug, the simulation wasn't computed correctly which could lead to very large errors in the landing prediction. The simulation ran fast though so didn't slow down the game much. Now it works again but is slower, but I've tuned it a lot to run as fast as possible which minimizing 'jitter' on the landing predictions. This is still higher than I'd like to some cases and it runs slower than I'd like. In my machine I've seen to take up to 50ms (x10 times a second, so taking 50% of the CPU!) when furthest from landing but mostly its not worse than 20ms. The jitter is generally low but I've seen it get high when coming to land at a low angle in Realism Overhaul.

- Upped throttle gains which avoids very heavy vessels hitting ground (depends on dt in simulate)
- Target crosses now move when selecting vessel or navigation target
- Landing burn works correctly when clicking button even if aero-descent not enabled first
- Fixed bug in simulate that led to landing burn not being simulated below 500m (leading to jitter in predictions)
- Tuning of simulation to make it as fast and accurate as I currently can
- Now runs faster for planets with no atmosphere
- Reduced maximum gains to try and reduce the near to tweak gains to reduce max angle-of-attack in RO (gains still needed to be low for RO)
- Reduced jitter to landing prediction by reducing timestep of simulation when near ground (can still get bad jitter is some scenarios)

Get it here https://spacedock.info/mod/2587/BoosterGuidance and here https://github.com/oyster-catcher/BoosterGuidance/releases/tag/v1.1.1

Released under GPL v3. I'd definitely recommend users upgrade. A full tutorial video is *still* in the works.

[oyster_catcher]

13 hours ago, Helvica_Ring_Scientist said:

I suggest you add a feature that adds a time when to do the boostback or stuff so we accurately land.
I would love that, and it would be highly helpful for me.

I suggest you check out this video which gives a rough idea of an easily manageable boostback, but you can actually be much more extreme than this but it gets a bit touch and go! It took a while before I got a real for it. This video is great!

Generally you want to still be climbing after you have finished boostback which means you have good height and will fall not too far off vertical. So, I tried to reproduce your trajectory with a near horizontal re-entry burn. I tried it out in realism overhaul in v1.1.1 (just released). I have now fixed a number of bugs and amazingly I managed to 'land' (almost!) within a few hundred metres of the landing target. I accidentally took off again as the throttle switched to maximum when BoosterGuidance got disabled on landing! But I did get some extreme jitter of the landing prediction due to the highly non-vertical trajectory before landing. See my attempt here:

 

 

 

[Kerbal Productions]

But one time I had just 15m err at boostback, all of it was ruined when the re-entry happened. Any tips?

[Kerbal Productions]

And I really, REALLY wanted to have the feature when to do the boostback, just like maneuver nodes. If you could add that, please add it as it means so much to my booster-return missions!

[oyster_catcher]

14 hours ago, Helvica_Ring_Scientist said:

But one time I had just 15m err at boostback, all of it was ruined when the re-entry happened. Any tips?

A video would really help please, but, when did it go wrong? In the re-entry burn, aero-dynamic descent or landing burn?

The most likely cause is that the booster is being steering the wrong way, this can happen when the engine is ignited and travelling fast. This could be re-entry or landing burn. The aero-dynamic descent is usually well behaved. If this happens then move the gain slider for that phase far left and the error should at least not grow any more.

10 hours ago, Helvica_Ring_Scientist said:

And I really, REALLY wanted to have the feature when to do the boostback, just like maneuver nodes. If you could add that, please add it as it means so much to my booster-return missions!

I'm struggling to work out what the specification would be. In reality you would boostback after you separate the 2nd-stage. I guess you want something like the furthest point on the predicted trajectory where you would still have enough fuel for boostback, re-entry and landing? For this I'd need to predict fuel consumption and fully understand the change in mass from staging, and understand which components you want to send back after staging. This is very difficult if possible at all as the KSP API doesn't really tell you what you would get in the future after staging.

I think it might be possible the work something out without trying to predict staging, but I'd have to work out fuel consumption and thats quite complex too. I'll bear it in mind as feature but its some way off, sorry.

[Kerbal Productions]

Any update that's helpful for more accurate landings, it'll be a go for me!

[henrylzy]

Great work! I use it with the Tundra's F9 booster and it works pretty well!

 

A little suggestion, not sure if anyone have mentioned it before, it'll be great if there is a preset option to select from different profiles(eg. Droneship landing, ground landing-pad landing), so instead of the parameters reset every time for a new launch, I can just select from saved  profiles for different landing pads or orbits.

[oyster_catcher]

6 hours ago, henrylzy said:

Great work! I use it with the Tundra's F9 booster and it works pretty well!

 

A little suggestion, not sure if anyone have mentioned it before, it'll be great if there is a preset option to select from different profiles(eg. Droneship landing, ground landing-pad landing), so instead of the parameters reset every time for a new launch, I can just select from saved  profiles for different landing pads or orbits.

Excellent, glad it works for you.

Ok, that's an interesting thought, would do you tend to change for the different types landings? I tend the settings depend a bit more on the vessel rather than the landing type so they are saved with the vessel. I'm a bit wary of adding the complexity for something I'm not very sure had I'd use it so I'd be interested in your reasons

[henrylzy]

19 hours ago, oyster_catcher said:

Excellent, glad it works for you.

Ok, that's an interesting thought, would do you tend to change for the different types landings? I tend the settings depend a bit more on the vessel rather than the landing type so they are saved with the vessel. I'm a bit wary of adding the complexity for something I'm not very sure had I'd use it so I'd be interested in your reasons

The mod resets the coordinates and re-entry burn target altitude and speed to 55000m and 700m/s every time when a new launch started, so I have to manually adjust all the parameters, including the max steering angle for each stage(the default for aero-descent is 30 and that setting would flip my first stage everytime when it hits the dense part of the atmosphere). Also my re-entry burn is significantly lower than the default value(27000m, 280m/s).

For each landing I tends to fine tune those parameters. The first stage would sometimes flip so I set the aerodescent steering limit really low, and the touch down margin was set to a low value so that it would perform more like a spacex’s suicide burn.

 

I also have a drone ship placed on the ocean, as well as another landing pad on the shore north east to the KSC for a 40-55 degrees inclination launch, just to maximize the capacity of the rocket.

 

 

 

[oyster_catcher]

On 1/24/2021 at 9:57 AM, henrylzy said:

The mod resets the coordinates and re-entry burn target altitude and speed to 55000m and 700m/s every time when a new launch started, so I have to manually adjust all the parameters, including the max steering angle for each stage(the default for aero-descent is 30 and that setting would flip my first stage everytime when it hits the dense part of the atmosphere). Also my re-entry burn is significantly lower than the default value(27000m, 280m/s).

For each landing I tends to fine tune those parameters. The first stage would sometimes flip so I set the aerodescent steering limit really low, and the touch down margin was set to a low value so that it would perform more like a spacex’s suicide burn.

I also have a drone ship placed on the ocean, as well as another landing pad on the shore north east to the KSC for a 40-55 degrees inclination launch, just to maximize the capacity of the rocket.

I agree. Thats very painful to have to set those values every time.

The settings get saved when you use "Save Game". I think the problem is that the craft is saved with the default settings from the VAB. So when you reset to launch, which is like loading the saved game at launch the settings are reset.

So I'll at least try and work out either how your craft can get saved with your settings, or someway they don't get reset with a revert to launch. Thats the first step.

Thanks

[Kerbal Productions]

I have the Tundra Exploration mod, gonna try it out ASAP.

[Kerbal Productions]

So I tried it out, the Super Heavy landed with just a 10m error! Great mod! But I had a problem: the booster nearly dived so hard so I tried to slow it with HyperEdit (sorry!). I think it was my fault cause I changed something. I'll update you when I solved that problem, but what a great mod! It landed my precious Super Heavy! Gotta try it to a droneship! 

[oyster_catcher]

13 hours ago, Helvica_Ring_Scientist said:

So I tried it out, the Super Heavy landed with just a 10m error! Great mod! But I had a problem: the booster nearly dived so hard so I tried to slow it with HyperEdit (sorry!). I think it was my fault cause I changed something. I'll update you when I solved that problem, but what a great mod! It landed my precious Super Heavy! Gotta try it to a droneship!

Fantastic! Glad it worked for you and thanks for the kind words. I've tried to make the mod as easy to use as I can but it still takes quite a bit of experience to get it working really well. Thanks for persevering to get to that point. It'd be interesting to know if your super-heavy had enough thrust to slow down with the hard dive without using HyperEdit, perhaps it did, the mod will aim to use 90% of the maximum thrust to slow down so I can be very late with the sufficient thrust and a light booster.

If you can land a super heavy with 10m error than I think you are ready to build a tower that can catch it out of the air the way Elon is proposing. That would be a fantastic feat to pull off! I'm not quite sure how to build a launch tower that could do that, but perhaps you can or definitely someone in the community can and probably will be doing that.

Part 2 of BoosterGuidance tutorial uploaded. Covers controlling multiple boosters/vessels (for Falcon Heavy style dual landings), setting landing burn engines and logging/plotting. See 

The logging can unfortunately sometimes fail to enable due to some kind of C# file opening error (files not getting closed or some file opened twice or something). If it fails (BoosterGuidance won't get enabled with logging switched on) delete all the ~/${KSP_INSTALL}/*.dat files and try again. Sometimes it might require a KSP restart. I've been working on fixing this for a while but its tricky to debug, so sorry if logging sometimes fails.

[Kerbal Productions]

I have problems with landing on a droneship. 

1. Sometimes, the booster will be upside-down at 3km from water. So the booster speeds up if it flips. Here's a diagram.

2. The boostback can bring the error to 500m, but when the re-entry burn is done, it pushes it to 2km or more. If I lessen the thrust limiter before re-entry burn, the error will increase, leaving me no choice but to use 100% thrust.

Any solutions?

[oyster_catcher]

10 hours ago, Helvica_Ring_Scientist said:

I have problems with landing on a droneship. 

1. Sometimes, the booster will be upside-down at 3km from water. So the booster speeds up if it flips. Here's a diagram.

2. The boostback can bring the error to 500m, but when the re-entry burn is done, it pushes it to 2km or more. If I lessen the thrust limiter before re-entry burn, the error will increase, leaving me no choice but to use 100% thrust.

Any solutions?

Hmm. The mod shouldn't be causing the booster to flip. If you toggle "Debug" in the "Advanced Tab" you will then see a green line which is the desired orientation of the rocket pointing in the direction of the front of the rocket, so it should be pointing upwards. It'll be very useful to know if this is still pointing up, if so then somehow the aerodynamics of the booster has flipped it, not BoosterGuidance, but possibly BoosterGuidance has made its steering unstable.

So I suggest, enable "Debug", try setting up the steering gains to far left so it won't try to steer at all, and seeing if it still flips. Also, at which stage does it flip, in re-entry burn? (I have seen a rocket start to turn with thrust vectoring from the main engine, the main engine cuts and then it doesn't have enough RCS or reaction control wheels to stop the turn, this could be happening - more RCS thrusters or reaction control wheels, and less steering gain in re-entry burn would help this)

[Kerbal Productions]

It happens after the re-entry burn. And I tried to increase the torque of the booster guidance unit. Before that, I noticed that the retrograde is locked in 180 degrees, making it flip, so I realized that the mod goals for retrograde, or maybe it was me who did it. I just forgot what caused it, but I'll try it soon.

[Raqnick]

 This mod is doesnt work.Stage just hit the ground

Edited March 2, 2021 by Raqnick