[PART, 1.0.2] Anatid Robotics / MuMech - MechJeb - Autopilot - Historical thread

[Castun]

^ It does this sometimes even when using pod torque instead of RCS, RCS is just a lot quicker and more noticeable. It's why when I let MechJeb use RCS for turning, I always manually disable RCS a couple seconds after it gets itself rotating, then turning it back on early enough that it can stop itself. I think the problem is the PID functionality of MJ & ASAS. Having a fixed value for all of these throughout an entire mission, when your mass and maneuverability will constantly change just doesn't work.

On the other hand, I don't have any good ideas on a way to solve the problem either.

[Smorgesborg]

AFAIK ORDA isn't being developed anymore. Has someone else picked up the project?

Yes, please look it up.

Search "Orbital Rendezvous and Docking Assistant." There's one for the current version.

[aquilux]

I've noticed this as well. My first stage always reports 0 dV even though I have LFEs & SRBs in the first stage.

There's a bug report about this. It appears all solid fuel rockets report as 0dV until the next update's fix.

[aquilux]

^ It does this sometimes even when using pod torque instead of RCS, RCS is just a lot quicker and more noticeable. It's why when I let MechJeb use RCS for turning, I always manually disable RCS a couple seconds after it gets itself rotating, then turning it back on early enough that it can stop itself. I think the problem is the PID functionality of MJ & ASAS. Having a fixed value for all of these throughout an entire mission, when your mass and maneuverability will constantly change just doesn't work.

On the other hand, I don't have any good ideas on a way to solve the problem either.

Simple solution, work it in exactly the same way the landing autopilot keeps from smashing into the ground. Use the attitude error as if it's altitude, measure turn rate off of how quickly attitude error changes and use that as velocity, and measure change in turn rate over time (Degrees per second squared) and use that in place of your T/W.

Calculate a table that is updated live based off of your (degrees per second squared) multiplied by an aggressiveness factor (0 to 1, zero does not even try and one will fling the controls full force one way until half way there, then full force in reverse to the target, set by user). This table indicates the desired turn rate per attitude error, much in the same way that the landing autopilot specifies a desired velocity per altitude and feeds that value into the translatron. If the current turn rate is below this, it will thrust to increase turn rate. If it is over this, it will thrust to reduce it's turn rate.

Obviously this gets complicated if you change your target attitude, but that can be attributed to user error. Either don't change your desired attitude so suddenly, or don't set the aggressiveness factor so high that mechjeb can't react fast enough.

Also, fix the method of attitude change. In situations that humans would move in a straight line to the target, which is the most efficient, mechjeb traces out a spiral.

Edited June 3, 2013 by aquilux

[Good_Apollo]

I have a questioning concerning Rendezvous Autopilot: Why are the Hohmann Transfers always high orbits and never low? It doesn't seem to matter what the velocity is, it always goes high. For instance, I have Mir built and I want the Shuttle to realistically come from below instead of meeting it high...

It always seems like I'm wasting fuel, especially when I have payloads that are only meant for LKO and yet are having to burn +150-200KM higher than the target. Maybe I'm misunderstanding the science and math behind it, but I don't think I am.

[HoY]

I have a questioning concerning Rendezvous Autopilot: Why are the Hohmann Transfers always high orbits and never low? It doesn't seem to matter what the velocity is, it always goes high. For instance, I have Mir built and I want the Shuttle to realistically come from below instead of meeting it high...

It always seems like I'm wasting fuel, especially when I have payloads that are only meant for LKO and yet are having to burn +150-200KM higher than the target. Maybe I'm misunderstanding the science and math behind it, but I don't think I am.

It will use lower if you start at a low enough altitude. I frequently launch my ships to a 250km altitude now that I plan on rendezvousing with mechjeb.

I'll launch the other parts to 80km, it seems to want a difference of at least 120km otherwise it will raise its orbit above the targets.

[Good_Apollo]

Yeah that sucks because I often have my LEO stations, like Mir, at altitudes of like 70-85, so there won't be enough clearence. I guess I'll have to try manually doing it...

[HoY]

Or you can do your launches to 200-250km at an extra cost of around 150m/s and let mechjeb take over from there? I do that sometimes too

[MissMolly]

just my thoughts.

well im still not happy with v.20.2 at all and MJ2 is still buggy to the point i just keep the old one from v.19

thought MJ2 would work better with the v.20.2 but that was wishful thinking this could be Ksp more them MJ. im thinking on running my v.19 as it worked better with MJ2.

[Innuce]

I'm not having many issues with MJ2.

I have used the Launch Autopilot, Rendevous Planner, Maneuver Planner, Docking Autopilot, and Smart A.S.S.

The Launch Autopilot doesn't recognize Jet Engine first stages, so I have to use the space bar when I want to decouple my Jets... It just takes getting used to, like for instance, I won't engage the Docking Autopilot until I'm within 30m. The Rendevous Planner gets me in the ballpark within 1000m, then I get in close using the Smart A.S.S. controls. Other than that, it's just like the kind of tools you'd expect a real astronaut's craft would have.

My biggest issue right now is KSP V.20.2 still having the docking bug that freezes up your controls. Fortunately, there's a workaround, but until it's fixed, we run the risk of large stations falling prey to the "wobble of death".

[evilC]

It will use lower if you start at a low enough altitude. I frequently launch my ships to a 250km altitude now that I plan on rendezvousing with mechjeb.

I'll launch the other parts to 80km, it seems to want a difference of at least 120km otherwise it will raise its orbit above the targets.

I am guessing this is to do with time involved. By preferring higher orbits, you are more likely to have a higher warp threshold - by definition you need to wait for an xfer window, so I guess this is coded to avoid it sitting on 2x warp for hours (realtime).

But I agree, there should be a checkbox for "Force lower phasing orbit".

[HoY]

With the proper altitude distance mechjeb will always calculate an intercept burn in less than a full orbit,, so even at 5x warp its no more than a couple mins to get around kerbin. Tho I think you can still go at 10x at 70km can you not?

[MTemplar]

OK. So I've gone and installed Kerbal then Mechjeb2. I put it in the gamedata file then I go into the game and install the module onto the ship. When I go to launch I don't have any special windows to open and don't have anything to click on. It's like I don't even have anything installed except something to give me the module. I currently have 2.2 and 2.0 on my machine and have even tried the 1.9 with the different variations of the mechjeb to see if it will work and nothing is happening. This is the most frustrating thing when you do EVERYTHING that you are supposed to do and yet get no results. Any help would be great.

[HoY]

Top right corner there should be a little translucent tab to press that brings out the window. When it moved with the newer version it threw me off and I couldn't find it right away.

If its not there, open your debug log and see if there are any red entry's.

[Castun]

It seems that a retrograde orbit (East to West) causes NML+ to point south, and vice versa. Is this correct? A quick Google search seems to suggest that normal is always 90' rotation in relation to your trajectory, and anti-normal is -90' orientation, so yes it would seem correct. I think the way the tutorial explained normal and anti-normal for changing your inclination made references to North and South, which is what confused me.

[SpaceDude]

Or you can do your launches to 200-250km at an extra cost of around 150m/s and let mechjeb take over from there? I do that sometimes too

That's not really an option with Mir, unless you want to create a different launch vehicle to get it to 200-250km, but the Proton that comes with the Soviet Pack won't lift Mir components any higher than ~85km before it runs out of fuel.

-

Does anyone know whether it's possible to easily scale down the radial MJ component that comes with MJ2? I am looking for something I can stick on probes, so about 1/4 of the size of the current MJ module.

[ShroomOfDoom]

OK. So I've gone and installed Kerbal then Mechjeb2. I put it in the gamedata file then I go into the game and install the module onto the ship. When I go to launch I don't have any special windows to open and don't have anything to click on. It's like I don't even have anything installed except something to give me the module. I currently have 2.2 and 2.0 on my machine and have even tried the 1.9 with the different variations of the mechjeb to see if it will work and nothing is happening. This is the most frustrating thing when you do EVERYTHING that you are supposed to do and yet get no results. Any help would be great.

I installed it the same way as always,before the folder change came with the recent big update and it works just fine.

There is one bug i witnessed though: for some reson it takes MJ2 68 years to do a Hohmann transfer to rendezvous with my station O.o

[KhaosCorp]

That's not really an option with Mir, unless you want to create a different launch vehicle to get it to 200-250km, but the Proton that comes with the Soviet Pack won't lift Mir components any higher than ~85km before it runs out of fuel.

-

Does anyone know whether it's possible to easily scale down the radial MJ component that comes with MJ2? I am looking for something I can stick on probes, so about 1/4 of the size of the current MJ module.

And herein lies the problem with pre-made ships.....

try building your own Mir launch vehicle to better suit your needs, or refuel the proton I guess is another option

[Castun]

Does anyone know whether it's possible to easily scale down the radial MJ component that comes with MJ2? I am looking for something I can stick on probes, so about 1/4 of the size of the current MJ module.

Very easy to do actually...just clone the part.cfg in the MechJeb part folder, and adjust the rescale factor. But be sure to give it a new name and ID too, otherwise it will confuse the game on which sized model to use.

[KD3]

-snip- There is one bug i witnessed though: for some reson it takes MJ2 68 years to do a Hohmann transfer to rendezvous with my station O.o

I've experienced this bug too. Does your fps drop when this happens as well? It does for me. Sometimes I am feeling too lazy to rendezvous

[Binkius]

Another "68y 35d" bug report:

When trying to use the rendezvous autopilot, I end up waiting for a 68y 35d Hohmann transfer (matching planes and phasing seem to work fine). I tried searching for this - seems like MechJeb is telling me that it can't make the calculation. What am I doing wrong? Thanks for any help.

Edited June 3, 2013 by Binkius

[SpaceDude]

Very easy to do actually...just clone the part.cfg in the MechJeb part folder, and adjust the rescale factor. But be sure to give it a new name and ID too, otherwise it will confuse the game on which sized model to use.

You are a genius! Thank you so much!

[The_Duck]

I am guessing this is to do with time involved. By preferring higher orbits, you are more likely to have a higher warp threshold - by definition you need to wait for an xfer window, so I guess this is coded to avoid it sitting on 2x warp for hours (realtime).

But I agree, there should be a checkbox for "Force lower phasing orbit".

Yes, MJ will change its orbit before starting the rendezvous process if it starts out in an orbit too similar to the target. The problem is that if your orbit altitude is almost the same as the target's, then it takes forever for you to catch up to the target, since you have similar orbital periods. Lots of people were complaining about MJ waiting many orbits at low altitude with low warp limits before it reached its transfer window for intercept. And some people were starting at exactly the same altitude as their target, which means it will take infinitely long to catch up! So MJ has to switch to a different orbit in these cases before it can start the main rendezvous process.

A checkbox to prevent this sounds like a good idea though; it will let you rendezvous more efficiently if you have the patience for it.

[HoY]

A checkbox to prevent this sounds like a good idea though; it will let you rendezvous more efficiently if you have the patience for it.

I'd be onboard with that

[Innuce]

I used Rendevous Autopilot once or twice. I didn't like how it automatically adjusts your orbit either. Especially if I had already done so.

My preference is to use the Rendevous Planner. You can go down the list manually. That way you can skip the orbit adjustment step, and the whole thing works like a charm!

You do, however, have to have your Maneuver Planner open so you can tell it to execute the next node. Would be nice to add that button in the Rendevous Planner window in the future.