Jump to content

[1.12.x] Anatid Robotics / MuMech - MechJeb - Autopilot - [2.14.3] [4th March 2023]


sarbian

Recommended Posts

7 minutes ago, captspiff said:

Two Stage assent: TWR is 0.53 (second stage lights after atmosphere escape)

 

it's low, so unless you have ascent angle 40 or less (depends on how much deltav in first stage), you don't make it, and here comes MJ bug which i am talking about - it does not pitchup in end of burn.

 

23 minutes ago, ansaman said:

I only use Mechjeb. If you are happy with the performance of another mod, use that.

I use around 55 if I have a good TWR, you are right, 75 might be too high and 40 is almost always WAY too low given current atmospheric characteristics.

problems start if ascent angle lower than 40, in last test it was 34, and it still goes ok without steering correction,

and it will be ok if abort MJ, right at apoapsis and manually pitchup so vertical speed would be still positive,

again it's optimum orbit profile, if you use 50 ascent profile you lose a LOT of delta-v (with starting TWR > 2).

as for other mod, i too prefer mechjeb just because it could do many things(in compare to only gravity turn), but that's not excuse for clear bugs.

 

 

Edited by okder
Link to comment
Share on other sites

13 minutes ago, captspiff said:

Q limit is turned off. I was using it set at 30000 pa but turned it off to try, and fail, to make assent work. 

AoA is set at 5 degrees

Two Stage assent: TWR is 0.53 (second stage lights after atmosphere escape)

THERE is your problem. TWR of .53 is WAY TOO LOW. I have found .80 to be not enough and 1.0 can be marginal depending upon ascent path. 30000 pa is TOO HIGH, but turning it off can be just as bad. Try 20000. AOA of five degrees is not enough. It restricts the gravity turn too much and will ruin your ascent. Try 10 degrees. The TWR of .53 cannot generate enough acceleration in time to avoid gravity overtaking your craft. Remember, an orbit is FALLING back to the surface and MISSING because of the speed (about 2250 or so in KSP). If you do not reach orbital speed quickly enough you will hit the atmosphere and then you are done.

Link to comment
Share on other sites

0.53 on border, if you have at least 1700 dv in first stage, with low ascent profile (<40) you going to make it but you need to pitch up manually, and burn continuously (low ascent profile actually guaranties that), but if first stage have less than 1700 dv you having a big problem, in border cases that means you would spend too much delta-v from second stage, or not going in orbit at all.

 

Link to comment
Share on other sites

17 minutes ago, okder said:

but that's not excuse for clear bugs

I don't see these bugs so I will politely opt out of further discussion with you and defer to your superior knowledge of what should be happening despite 3-4000 hours playing KSP and over a thousand with Mechjeb. I am sure that with your superior knowledge you will be able to fix the mod and rewrite the code. I apologize for trying to help with my inferior knowledge and experience.

Link to comment
Share on other sites

10 minutes ago, ansaman said:

I don't see these bugs so I will politely opt out of further discussion with you and defer to your superior knowledge of what should be happening despite 3-4000 hours playing KSP and over a thousand with Mechjeb. I am sure that with your superior knowledge you will be able to fix the mod and rewrite the code. I apologize for trying to help with my inferior knowledge and experience.

again it's simple 2 clear bugs with corrective steering:

1. incorrect inclination in the end (mostly by cicrularization burn)

2. incorrect pitch in the end of gravity turn (at border of atmosphere), so it initially kills vertical velocity, and not restore (some positive) vertical velocity in the end of burn, when it's critically needed.

i.e. when you slowly begins to fall down (almost reached orbit velocity) it's pretty clear that you need to pitch up to prevent fall down, no high maths or programming skills required to see that, and yes i do have knowledge how to fix it, but compile whole mechjeb (not only ascent guidance), and testing it after fixes, and posting fixes itself requires a lot if time (all of that requires several times more time actually than simple to fix a bug).

 

Edited by okder
Link to comment
Share on other sites

6 minutes ago, okder said:

0.53 on border, if you have at least 1700 dv in first stage, with low ascent profile (<40) you going to make it but you need to pitch up manually, and burn continuously (low ascent profile actually guaranties that), but if first stage have less than 1700 dv you having a big problem, in border cases that means you would spend too much delta-v from second stage, or not going in orbit at all.

 

Your target orbit also matters.  If you're going higher you can get away with a low TWR in the circularization stage.  So long as there is enough time between the edge of the atmosphere and the apoapsis you'll make it.  I've circularized with a TWR below .1.  I went for a higher orbit and made sure it staged at the very end of the initial burn so MechJeb would not be confused about what to expect. 

Link to comment
Share on other sites

1 minute ago, Loren Pechtel said:

Your target orbit also matters.  If you're going higher you can get away with a low TWR in the circularization stage.  So long as there is enough time between the edge of the atmosphere and the apoapsis you'll make it.  I've circularized with a TWR below .1.  I went for a higher orbit and made sure it staged at the very end of the initial burn so MechJeb would not be confused about what to expect. 

if you have low twr, then in reality you need to go lowest possible orbit, only reason why it's not the case with mechjeb - forced coast time between gravity turn burn and circularization burns.

 

Link to comment
Share on other sites

2 hours ago, okder said:

if you have low twr, then in reality you need to go lowest possible orbit, only reason why it's not the case with mechjeb - forced coast time between gravity turn burn and circularization burns.

 

IRL most upper stages have a low TWR...  which is what he's talking about there.

Link to comment
Share on other sites

About the pitch up at end of turn bug:
I'm already used to this behaviour since I started with KSP about a year ago.

I found kinda troubleshoot like this:
When the turn is about 2/3 before the turn-end altitude is reached (80 km for 120 km for example) then I go into the ascent path setting, change the final pitch angle value to another value, press Enter, change it back and press Enter again.
This also helps when the craft is already above the assigned altitude and not pitching correctly, just change and change back.

Link to comment
Share on other sites

Hello i have little issue with mechjeb .

 

I use RSS with a bit lighter my own version of realism and it uses "Mandatory RCS" mod . This mod disable tourque in reaction wheels making them useless as a tool to turn the vessel , they only provide some degree of stabilisation.

Now the problem.

When i make maneuver node and press "execute" mechjeb properly use rcs to point vessel towards maneuver node , then it start time warp but it does not stabilise vessel and in warp it keep spining so it is not pointing at the node . Then it leave time warp start turning vessel again , when it point towards node it start warping but again vessel keep spining so it repeat and repeat warp , turning , warp turning warp turning making usage of mechjeb  pointless.

 

With single maneuver node it is not very big issue as i simply manually activate SAS , point at the node use "warp to next maneuver" then execute maneuver in mechjeb just before the node , but when i make several nodes before using mandatory rcs i could just execute them all , go make coffe and come back seeing vessel in proper orbit. Now i need to manually warp to every node and usage of mechjeb is very limited .

 

Any ideas how to teach mechjeb to use SAS during maneuvers so it stop vessel spin when pointing in to the right direction?

Seems like Mencjeb have issues controling vessel without reaction wheels , it is perfectly fine during the burn when it is using only engine gimbal but when i turn on RCS it keep oversteering more and more as it is unable to stabilise the vessel using only rcs and engine gimbal

Edited by Karamon
Link to comment
Share on other sites

Good day, dear Sabrian.

I recently tried to play KSP v1.3.0.1804 with Mechjeb v2.6.1. Absolutely clear version of KSP, i do not install any other mods, only mechjeb. After starting KSP with launcher i briefly see the yellow bar, and then only the black screen with the ksp cursor. No crashes, no errors, so i can not even attach error logs.

What can i do with that problem?

(Sorry, im not native speaker, not even good in eng language.)

UPD. Only need to reinstall. Sorry for it.

Edited by 36OZone
solution
Link to comment
Share on other sites

58 minutes ago, 36OZone said:

Good day, dear Sabrian.

I recently tried to play KSP v1.3.0.1804 with Mechjeb v2.6.1. Absolutely clear version of KSP, i do not install any other mods, only mechjeb. After starting KSP with launcher i briefly see the yellow bar, and then only the black screen with the ksp cursor. No crashes, no errors, so i can not even attach error logs.

What can i do with that problem?

(Sorry, im not native speaker, not even good in eng language.)

UPD. Only need to reinstall. Sorry for it.

@36OZone For the record, errors and crashing have nothing to do with whether you have logs or not.

Unless you explicitly disable logging then you always have logs.

If you don't know how to find your logs then see the following post, linked below.

 

Link to comment
Share on other sites

 Hi,

 I'm having a very interesting issue with MechJeb. Currently, MechJeb will not control my craft unless my mouse is hovering over a MechJeb window which activates the InputLock. My normal in-game SAS also will not work unless my mouse is hovering over one of these windows. Occasionally it'll randomly work, especially if I toggle the manual input lock, but it is unreliable and will randomly stop working at the most annoying times. I've tried reinstalling the game, and I've tried running with no other addons, but I haven't had any luck in fixing this issue. My only other addons I'm running currently are Connected Living Space, Ship Manifest, and Module Manager. When I reinstalled the game I installed MechJeb first and made a new savegame, and still had the same issue. 

 

Here's a link to my log file https://drive.google.com/open?id=0BzuxLXaOCmQgclhoZTFOdV9qa00 

 

Let me know if I can provide any more information to help with this issue. 

Link to comment
Share on other sites

I'm trying to launch to rendezvous to my orbiting satellite, but it doesn't seem to be working. I select the target, engage autopilot and wait for launch. It launches when the target is almost on the other side of Kerbin. Also, it doesn't launch to the target's altitude, it launches to whatever orbit alt I have set. It also doesn't launch into the plane of the target, just whatever I have the inclination set to. It's like Launch to Rendezvous is just not working at all. Not even close. I also randomly lose the set target. Am I doing something wrong?

Edited by Voodoo8648
Link to comment
Share on other sites

Another question regarding the Scripting Module:

Is it possible to create a maneuver like a Hohmann Transfer later in the future and have the Scripting module automatically execute that? For example, if I send a ship to Duna orbit then want it to perform a Hohmann Transfer to It's moon.

Link to comment
Share on other sites

1 hour ago, Voodoo8648 said:

I'm trying to launch to rendezvous to my orbiting satellite, but it doesn't seem to be working. I select the target, engage autopilot and wait for launch. It launches when the target is almost on the other side of Kerbin. Also, it doesn't launch to the target's altitude, it launches to whatever orbit alt I have set. It also doesn't launch into the plane of the target, just whatever I have the inclination set to. It's like Launch to Rendezvous is just not working at all. Not even close. I also randomly lose the set target. Am I doing something wrong?

Your problems are linked. It doesn't enter your target orbit for you, you have to do that yourself. If you don't do that and the altitude entered is very different then the phase angle is going to be wrong.

So you have to enter the orbit altitude manually. It doesn't have to be exact but it does have to be close enough to put you in the right area. You can even do it a little lower or a little higher and then do a Hohmann Transfer.

One other thing that you need to be aware of is that even if you DO have the right orbit entered, you still might not end up where you want or need to be. That's normal because MJ2 doesn't know how your rocket is going to perform. 

  1. So what you do is set all your launch parameters the way you want them and let MJ2 launch to rendezvous.
  2. Let it finalize the orbit.
  3. If the orbit is wrong, revert to launch and repeat the launch.
  4. This time, MJ2 knows how your rocket will perform because it just watched it in action!
  5. Now it will put you a lot closer to your rendezvous target.
  6. ?????
  7. Profit!
Link to comment
Share on other sites

9 hours ago, Starwaster said:

... 

  1. So what you do is set all your launch parameters the way you want them and let MJ2 launch to rendezvous.
  2. Let it finalize the orbit.
  3. If the orbit is wrong, revert to launch and repeat the launch.
  4. This time, MJ2 knows how your rocket will perform because it just watched it in action!
  5. Now it will put you a lot closer to your rendezvous target.
  6. ?????
  7. Profit!

Exactly so. Think of it as running a simulation before the launch.

Very rarely, a third launch attempt will get it even closer - though I am not sure why!

It helps to make sure the target is in as near an exactly circular orbit as possible - it's no good aiming for a 100km orbit if the target has periapsis of 98 and apoapsis of 115.

Link to comment
Share on other sites

55 minutes ago, Voodoo8648 said:

@Starwaster thanks for the explanation! Sooo, what exactly does the Launch to Rendezvous button do? 

When you finish a launch MJ saves the angle between your launch point and the point where you where in circular orbit. When you revert to launch and press "Launch to Rendezvous" MJ  can now use that angle to know when it should launch 

Link to comment
Share on other sites

3 hours ago, sarbian said:

When you finish a launch MJ saves the angle between your launch point and the point where you where in circular orbit. When you revert to launch and press "Launch to Rendezvous" MJ  can now use that angle to know when it should launch 

How persistent is that data? If not could it be made persistent? At least for the altitude? Assuming the altitude is a typical one for that rocket (which it probably should be but knowing players, who knows)

Link to comment
Share on other sites

it is saved in a cfg named after your ship (in the mechjeb install subfolders) so it persist as long as you don't launch a vessel using the same but a different design or from an other planet

Link to comment
Share on other sites

17 hours ago, Starwaster said:

So you have to enter the orbit altitude manually. It doesn't have to be exact but it does have to be close enough to put you in the right area. You can even do it a little lower or a little higher and then do a Hohmann Transfer.

Yeah. Set desired altitude a bit higher (+1..2km) and perform "match velocities with target at closest approach" maneuver instead of circularization. After that I have average distance to target about 700m and zero relative velocity. From launch to docking in 2 clicks.

Link to comment
Share on other sites

22 hours ago, Voodoo8648 said:

Another question regarding the Scripting Module:

Is it possible to create a maneuver like a Hohmann Transfer later in the future and have the Scripting module automatically execute that? For example, if I send a ship to Duna orbit then want it to perform a Hohmann Transfer to It's moon.

Is it possible to use Scripting Module to make a self automated probe like Voyager I & II? I'm early on into my career and don't have the technology for long range comm antennas but I want to send a probe to Eve and slingshot to Duna or Jool. I'd need the Hohmann Transfer planner to set up a maneuver after entering Eve's SOI, but it doesn't appear as though this is possible. Am I missing anything?

Link to comment
Share on other sites

8 hours ago, Voodoo8648 said:

Is it possible to use Scripting Module to make a self automated probe like Voyager I & II? I'm early on into my career and don't have the technology for long range comm antennas but I want to send a probe to Eve and slingshot to Duna or Jool. I'd need the Hohmann Transfer planner to set up a maneuver after entering Eve's SOI, but it doesn't appear as though this is possible. Am I missing anything?

I actually have no idea which part of MJ works or does not work when out of comm. range. As for the Scripting module it is a contribution by @SPD13 and I did not take the time to look at all its features, yet.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...