When do you do your Gravity Turns?

[Blind Dead McJones]

My method is to fire straight up until about 10km, then turn towards the prograde vector. Make sure the time to apoapsis increases until it passes 45 seconds, and don't let it fall below that or you will not go to space today. Mind, with especially large rockets* you might need to start your turn later, closer to 15-20km. I'm not sure if this is just an intrinsic feature of big rockets or if I need to refine my technique. Also, all this only applies to Kerbin. On a planet with no atmosphere, you're supposed to start your gravity turn as soon as you lift off, because the lack of an atmosphere means that there's no minimum to orbital height.

*Actually I think it's less about mass and more about thrust-to-weight ratio. Not sure.

[ArmchairGravy]

My method is to fire straight up until about 10km, then turn towards the prograde vector. Make sure the time to apoapsis increases until it passes 45 seconds, and don't let it fall below that or you will not go to space today. Mind, with especially large rockets* you might need to start your turn later, closer to 15-20km. I'm not sure if this is just an intrinsic feature of big rockets or if I need to refine my technique. Also, all this only applies to Kerbin. On a planet with no atmosphere, you're supposed to start your gravity turn as soon as you lift off, because the lack of an atmosphere means that there's no minimum to orbital height.

*Actually I think it's less about mass and more about thrust-to-weight ratio. Not sure.

Yeah, it's TWR. The staging transition usually drops TWR. I know on my builds the end of stage one is around 2.5 TWR, and the beginning of stage 2 is around 1.8. The end TWR on stage 2 is higher, but that transition can slow me down 10-20m/s.

[Tortoise]

Since I use FAR, whenever my TWR and speed is good, not just a certain altitude.

[Bloodlance]

i always forget to turn early so i usually start my turn at 30 000 => to 45degrees.

BUT, my ships and rockets and all are not "normal", when 0.24 is released ill redo my stuff and post some vids here for all to enjoy

[Oafman]

I turn as soon as my poorly designed and over-engineered rocket allows me to do so.

[Superfluous J]

I turn as soon as my poorly designed and over-engineered rocket allows me to do so.

After a year of playing and countless missions that should teach me otherwise, this happens far more often than I'd care to admit.

[WooDzor]

70 degrees @7500

45 degrees @ 15000

and I put the rocket flat as soon as my apoapsis is above 45.000

[rkman]

- vertical to ~10km

- fairly aggressive turn to ~45 degrees pitch, during the last seconds of 1st stage burn (high twr). Steering loss is limited due speed still being relatively low.

The rest of the turn is slow and gradual, thus limiting steering loss in spite of speed being high. Most of that is done with the 2nd stage, which has an initial twr of about 1.8.

- reach ~1000m/s at ~30km alt, pitch ~20degrees. At ~40km alt pitch is near zero.

- end up spending about 4400m/s for 75km orbit.

gravity turn is () ...allow gravity to pull your trajectory towards the surface until you're horizontal.

I think that can be done at any point along the ascent, even if the initial turn is aggressive. Then that initial turn is not a gravity turn, but the rest of the turn can still be mostly due to gravity pulling the trajectory towards horizontal.

The upshot of an aggressive initial turn is that gravity loss is limited due to more of the trajectory being closer to horizontal.

[NecroBones]

I usually start a slight tilt (only a few degrees) to the east by 1km. Then around 10km, I begin a more serious gravity turn, that arcs over gradually, following the prograde marker (mostly).

[xtremespino]

I turn over about 3-5 degrees at the start, but go full out at 10

[federicoaa]

I start the gravity turn when the surface speed is 100m/s, turn slowly watching the time to AP is between 30s and 60s

[Grover]

I use kerbal engineer and turn as my Ap reaches key points. I turn over to 80 after clearing the tower, then from an AP of 20km, for every 10km on the Ap, i roll over another 10 degrees, reducing throttle to keep the time to Apoapsis below 40-60 seconds, depending on the agility and twr of the launcher

[xcorps]

Mechjeb Ascent Guidance.

Begin 7500 End 55000 52.5% curve, corrective steering off, throttle limited to Terminal Velocity.

[Skorpychan]

Burn straight up until about 10k, throttled down to terminal. Then I bank over to about 45 degrees and hit the gas.

When the apoapsis is >70K, I kill the throttle and coast until out of the atmosphere. Then I turn over totally horizontal and burn prograde until I'm orbital.

[Mesklin]

I start gravity turn from 5 km, set pith 80, then each 5 km decrease pith at 10. At 10 km pith is 70, at 30 km pith is 30 and horizontal flight at 45 km. It works very well for rockets with TWR from 1.3 till 2.5. With this sequence you need move to map view for control your apoapsis only when your start horizontal flight.

[Trentendegreth]

i start my turn gradual off the launch pad, being at 45 at around 10k, depending on the rocket, gradual turn till horizontal with an AP> 51k. burn till AP is at altitude of choice, circularize and smile.

[Lichbane1401]

Realistic gravity turns work best for me. For twr of arround 1.2 i wait for 100m/s and then go to ~5 or for twr1.7 at 50m/s and gradually increase that and at about apo of 50km i start going from 45 to 0. This way i use ~4000 dV(I had ~8000 Vacuum dV according to KER and in orbit i was left with ~3200dV)

[OhioBob]

I was also wondering is anyone had done research or knows the most efficient method to preform a gravity turn

Yes, I wrote and performed a series of computer simulations to try to optimize TWR and the gravity turn. For the simulation I used a simple two-stage launch vehicle. I found that the optimum lower stage TWR is 1.64 and the optimum upper stage TWR is 1.31. I found that a slow gradual gravity turn works best. For the given TWR I started the gravity turn at about 5300 m and maintained the pitch angle slightly ahead of the surface velocity vector by about 3 degrees throughout the turn. First burn cutoff ended at an altitude of about 50 km with the vehicle horizontal and the velocity vector about +3 degrees. This put me into a 75 km orbit with the highest possible payload fraction. Every other scenario/iteration I tried reduced the payload fraction.

[TythosEternal]

I outlined the heuristic I use just now on the following thread:

http://forum.kerbalspaceprogram.com/threads/102302-How-do-YOU-launch?p=1588079#post1588079

Summary: I perform a 10 deg pitch-over when apoapsis hits 2000 m, then continue pitching over by 10 deg increments (sometimes more at higher altitudes) every time apoapsis doubles. This heuristic concludes when apoapsis hits 64000 m, at which point I transition to burning tangentially and throttling to maintain a fixed-time-to-apoapsis.

[peachoftree]

When I hit 100 m/s, I turn over very slowly, I aim to be at 45 degrees by 12,000m (FAR)

[GoSlash27]

around 7km and a slow, smooth tilt until i hit my desired apoapsis. but as important as it is to re-educate people on proper gravity turns, teaching people to adhere to the terminal velocity table is a lot more fuel-saving. far too many punch-it pilots.

^This. 10char

-Slashy

[Heagar]

When i perform the gravity turn really depends on the rocket i use.

It may be at 5k up to 15k for various reasons:

• an asparagus design, witch is maxed out and the second pair of tanks is not equipped with engines
  
• a week upper stage, so that i have to accelerate horizontal as soon as possible
  
• a "normal" rocket without any weeker stages
  
• a design without an upper stage where the transfer stage (especially LVN) have to perform the circularization burn