mechjeb and new atomosphere rules

[OgreMagi]

just started back on Kps and as with previous updates all my rockets will not work now.

but even things a simple as shooting a sat into orbit is getting difficult.

I cannot get mechjeb to lauch a rocket into orbit as when they start the gravity turn the rocket flips over. I tried farings , fins and several deisngs but mech jeb seems to flip it over around 10,000 meters.

I have updated mechjeb and replaced the files as with other updates so

Anyone know whats the issue.???

[Holyvision]

...did you read the mechjeb release forum pages at all??? Start at the end and read backwards, you have to edit your ascent profile because of the new aerodynamics.

Short answer: read!

:-P

[Caelib]

...did you read the mechjeb release forum pages at all??? Start at the end and read backwards, you have to edit your ascent profile because of the new aerodynamics.

Short answer: read!

:-P

Long answer: don't rely on mods

[Holyvision]

Long answer: don't rely on mods

Quoted for truth!

[BDelacroix]

Yes, you will want to edit the ascent profile. Some of my most stable payload delivery systems do actually work with the auto settings. Generally I set about 30k for the turn begin. 1000km for the speed. 40% for the curve 80-100 for the end turn. 5-10 degrees for the end angle.

Not as efficient as the machine but at least my stuff gets into space where that demon in the air can't tear it apart. I also adjust the acceleration from 20-40 m/s when needed.

The only times my rockets would turn over at about 10k is when the lift ball isn't below the center of gravity.

[pabumus]

I have also found that limiting throttle to 80 ~ 85% can help out a lot too.

[selfish_meme]

Its your rockets not mechjeb, check the flipping rockets threads.

[OgreMagi]

yea, funny how when I take a short absence nothing really changes, the pure players who never use mods, ( boring) and those who simply want to play without having to become a game fanatic....

thanks for the input on flipping rockets thread, I check it out but been playing for a while unless the basics physics has changed I don't think that is the problem. funny how hard it is to find the notes on Mechjeb about altering the lifting profile

hmmm, hard to find the notes on the mechjeb about altering the assent profile, but I will dig it out. thanks for the help,

[SAI Peregrinus]

unless the basics physics has changed I don't think that is the problem.

Aerodynamics changed. Treat it like you would have old FAR.

[selfish_meme]

I use Mechjeb a lot and it has no problems putting a rocket in orbit even without editing the ascent profile. The only ascent profile I edit is for Eve because you burn up a lot quicker and need to go straight for longer. If your rocket flips it is because it is aerodynamically unsound and you are pushing too fast through the atmosphere.

[magnemoe]

I use Mechjeb a lot and it has no problems putting a rocket in orbit even without editing the ascent profile. The only ascent profile I edit is for Eve because you burn up a lot quicker and need to go straight for longer. If your rocket flips it is because it is aerodynamically unsound and you are pushing too fast through the atmosphere.

Pretty much this, found that you want an low turn in an good rocket, if you fly an brick its an good idea to fly up to 15 km before turning.

I use mechjeb on most of my launches and have no issues except it overcorrect on some rockets causing osiliations.

[WOODY01]

My ascent profile that works for most rockets going to LKO:

Start Turn: 1K

End turn:45K

Final Flight Path Angle:3 Degrees

Turn Shape: 67

Heavier awkward rockets or going into high orbits I adjust the start turn higher.

[SciMan]

In case anyone's too lazy to go over to the MechJeb thread, I'll post the settings I use to launch my rockets, along with what kind of rockets they usually are.

Limit to terminal velocity: ON

Limit Acceleration: 25m/s^2

Prevent Overheats: ON (who doesn't turn this on, anyways?)

Angle Of Attack limiter: ON

- max aoa 7.5 degrees

- dynamic pressure fadeout 500kPa

Force Roll: ON

- climbout: 90 degrees

- turn: 90 degrees

Automatic Ascent Path: OFF

Turn shape: 40%

Turn start altitude: 1250 m

Turn start velocity: 150 m/s

Turn end: 45 km

Turn end angle: 5 degrees

Usual target orbit is 125 km, inc 0,6,-6 degrees (Mun/interplanetary or Minmus). But it works for polar launches too.

Rockets that work with these settings: Usually 2 stage launchers (2nd stage makes orbit), control surface fins on first stage, starting atmospheric TWR 1.75 (1.5 to 2.0 TWR should work) The higher end of the launch TWR range tends to start being too steep to be efficient. SRB assist on the first stage doesn't seem to cause problems.

Also, Attitude Adjustment settings (helps stop rocket wobbling):

Auto Tune: OFF

Tf: 0.35 for most 3.75m and 2.5m core stages, 0.25 for most 1.25m core stages. Some 2.5m core stage launchers I have (really simple ones) don't wobble with 0.25 Tf. You want it as low as you can get it without it starting to oscillate, because higher Tf is "slower" to respond.

That's about as much info as I can remember at the moment about my ascent AP settings without actually firing up KSP.

[cybersol]

You are not alone. This spinning thing is something we all initially had trouble with in the new 1.0+ aero until we learned to engineer better rockets.

Spinning out of control essentially comes down to a contest between drag and control. When the drag overcomes your control authority, you go for a spin. You can decrease drag by staying closer to prograde and building a more aerodynamic rocket. You can increase control using engine gimbals, stabilizer wheels, and control surfaces.

Also note that drag increases significantly right around mach one (340 m/s). So you should stay pointed as prograde as possible at speeds around 290-400 m/s.

On a rocket control fins should be as low and outside as possible. If you are using control fins on more than one stage, the CoL needs to stay below the CoM at all times, even as the tanks empty.

I also recommend piloting by hand at first in the new aero. You will spin more but it will happen faster, and you can get a better feel for what is working and what is not.

Edited June 4, 2015 by cybersol

[OgreMagi]

I watched the scott manly video about rockets in 1.0 and that seemed to help. He mentioned that fins will help and hurt.

they will keep you straight but they can limit your ability to change you angle. I am finding that I can launch rockets without fins or mech jeb but it is a grind as each rocket is effectively a custom job to fly/pilot wven with minor changes making the game less fun to play .

SSTO's everything I have seem shows that you have to get bigger ( larger craft) to use them effectively. I tried lower mass sstos and I am still getting problems. Rapiers seem the best compromise with the new atmosphere physics, but you end up with less Dv in orbit.

Has anyone tried the ore/mining /fuel production yet? I haven't got arroud to it .

[Motokid600]

Limiit the AoA to a few degrees. Also... I can't help but notice in everyone of these types of threads people are turning way to late. No matter what the rocket is you need to turn sooner. I start at 350m-400m with my lowest twr builds. That's why people are having so much trouble flipping. By waiting so late to turn your gaining way too much vertical velocity. So when it comes time to turn your rocket has to fight against that velocity to change its vector. And you flip. Turn sooner while the air pressure is low.

Edited June 4, 2015 by Motokid600

[Borsek]

I stopped using mechjeb for ascents as I find it easier to do simple and actual gravity turns. I still use the smart ass feature, but not ascent guidance. That said, values in the ascent curve can be tweaked so mechjeb works perfectly, but launching manually always leaves me with more dV. Launches are a lot easier now that you don't have to turn the rocket manually, just do 90deg angle at 100m/s and keep flying prograde for the rest of the ascent.

Rockets flipping come from design errors and a too big AoA.

[Vanamonde]

Mod-related question moved to the modding section.