Liquid engines don't maintain power

[geo950]

I'm new so this may be an obvious answer, but anyway: I'm trying to get into orbit, but for some reason my liquid engines are acting weird. They only hold power at about 1/3 throttle and it wavers up and down. It also cuts out randomly then cuts back in. I have electric charge. It happens to mechjeb as well.

Thanks

[MaxxPower]

Jet engines or rocket engines?

Jet engines require a certain amount of intake air, or they will cut out. And their thrust varies with speed and intake air.

[geo950]

LV-t45 and LV-t30, the two earliest unlocks in career mode. They may be rocket engines

[NathanKell]

Does your throttle display (on the left of the navball) waver too?

[geo950]

yes it does

[NathanKell]

Got joysticks connected? Did you configure them?

If not, do you press shift or control any? (or anything else to change throttle)

[moogoob]

If you have Mechjeb installed, check to see if any utilities are checked on. Some of them will affect your throttle (limit to acceleration for example)

[geo950]

No joysticks. I have limit to terminal velocity and prevent overheating on. But when this problem occurs it's nowhere near terminal velocity or overheating.

[Gaarst]

Check your key bindings to see if any key has two functions, this can be a very frustrating thing on non-english keyboards (speaking from experience).

[Cebi]

Post a screenshot with your rocket during those troubles you describe with open ascent autopilot window so we can better help you.

[Draslin]

No joysticks. I have limit to terminal velocity and prevent overheating on. But when this problem occurs it's nowhere near terminal velocity or overheating.

Don't assume that. Remember the aero dynamics have changed since mech jeb was designed originally. By turning your rocket you are increasing drag which in turn limits how fast the rocket can move, also know as terminal velocity.

I not sure it's a bug in mech jeb, I just think its something you can't really utilize anymore with the improve aerodynamics. Drag was more or less constant before the update from what I've been able to figure out.

Test it out. Turn on sas and don't change direction while you have limit terminal velocity on. Then turn the rocket a bit, you should see the throttle drop. I've seen it bottom out entirely when I've turned too much spreading drag across the long axis of the rocket.