Perfect ascent profile!

[Ekku Zakku]

I've been playing KSP for over a year now, so this ain't my first rodeo lol (I'd even put myself on Scott Manley's level), but I just had my first totally perfect ascent profile (following the prograde marker all the way to orbit).

While launching a small little Mun lander that I wanted to try out, I started a very slight (< 5%) gravity turn at around 2-3 km and followed the prograde marker the whole way up. Turns out my fuel, weight, and TWR were all balanced perfectly to make it happen! Reminded me of real life launch vehicles that do the same thing, and their orbit is at just the right (or nearly) altitude at MECO.

Has anybody else here just had a perfect launch or a perfect rocket like this? Usually I launch much heavier stuff or rockets with much higher TWR, and end up having to burn way off prograde to stop myself from cutting off the engines and coasting to apoapsis.

EDIT: also turns out I had just a perfect amount of fuel to land on the Mun, return to Kerbin, and make a powered landing (since I didn't pack a parachute). Lucky me XD

Edited August 25, 2013 by Ekku Zakku

[User Unrelated]

no... even though my rockets are always (almost always) perfectly symmetrical, they always seem to find a way to go crazy and start leaning to one side way too much...

I would put myself at the level of... uh... a pair of Scott's socks.

[Ekku Zakku]

no... even though my rockets are always (almost always) perfectly symmetrical, they always seem to find a way to go crazy and start leaning to one side way too much...

I would put myself at the level of... uh... a pair of Scott's socks.

Haha XD you'll get better in time, I'm sure. I was just born insanely smart and so I've had a knack for just about anything I do -.- I mastered rendezvous and docking after just two attempts (and I even succeeded in those attempts lol).

Anywho, it seems like smaller rockets (mostly 1.25 m parts) are a much closer analog to real life rockets, in terms of getting to orbit and resembling their appearance. They also never go crazy for me either lol, that's probably why I was able to do this in the first place; I doubt I'd ever be able to replicate that kind of ascent profile in a larger rocket.

[tom1499]

Yeah, the 1 meter parts do seem to portray actual rockets more realistically. For example, a small Mercury-Redstone clone might portray the real thing closer than a large DeltaIV clone.

[Bothersome]

Yea you will eventually learn when to start your gradual gravity turn based on the rate of increase in speed your craft is doing. Then you pretty much make every launch a nice one.

Every different craft has a different ascent profile. Experience eventually tells you when is best to start the turn. Waiting till 10k to start is usually always "not it".

The 10k thing was just an easy way to explain to beginners how to get started. And so many people have taken to it as a law or something. But how would someone explain to a newbie how and when to make a gravity turn without a wall of text and graph or few?

[RoboRay]

I've been playing KSP for over a year now, so this ain't my first rodeo lol (I'd even put myself on Scott Manley's level), but I just had my first totally perfect ascent profile (following the prograde marker all the way to orbit).

While launching a small little Mun lander that I wanted to try out, I started a very slight (< 5%) gravity turn at around 2-3 km and followed the prograde marker the whole way up. Turns out my fuel, weight, and TWR were all balanced perfectly to make it happen! Reminded me of real life launch vehicles that do the same thing, and their orbit is at just the right (or nearly) altitude at MECO.

Has anybody else here just had a perfect launch or a perfect rocket like this? Usually I launch much heavier stuff or rockets with much higher TWR, and end up having to burn way off prograde to stop myself from cutting off the engines and coasting to apoapsis.

I've been experimenting with ascent profiles on my Apollo/Saturn V and have it just about right where I want it...

http://youtu.be/smuZsxxarhg

Stage 3 shut-down is in a 100km by 60km orbit, with the spacecraft at periapsis. This requires only a mild 80m/sec or so circularization burn, while staying low (40-60km) for most of the horizontal acceleration to maximize efficiency.

(I'm filming a movie that recreates the Apollo 15-17 "J-class" moon missions, which is why I had that video handy.)

Edited August 25, 2013 by RoboRay

[arq]

I've always meant to try running the numbers through a numerical simulation to work out a dV-optimal profile and the necessary TWR through the process. Maybe I'll get around to it one day.

[M5000]

Yeah, my Falcon-9 works exactly perfectly like this. Feels good man.

[HavinAlmassi]

I've been experimenting with ascent profiles on my Apollo/Saturn V and have it just about right where I want it...

video=snipped

Stage 3 shut-down is in a 100km by 60km orbit, with the spacecraft just past periapsis. This requires only a mild 80m/sec or so circularization burn, while staying low (40-60km) for most of the horizontal acceleration to maximize efficiency.

(I'm filming a movie that recreates the Apollo 15-17 "J-class" moon missions, which is why I had that video handy.)

It's telling me the video you posted is private. Can I get on the list?

[RoboRay]

It's telling me the video you posted is private. Can I get on the list?

Oops, sorry about that... I must have miss-clicked. It should be working now.

[Masked Turk]

Is there some sort of calculator tool which can auto-figure this out?

[Ralathon]

Is there some sort of calculator tool which can auto-figure this out?

Not when launching from a body with an atmosphere or without infinite fuel enabled.

The differential equations you end up with are unsolveable analytically when the thrust to weight ratio varies, it has to be done numerically. So you need to feed the calculation with all sorts of info: stage setup, weight, ISP, max throttle etc to find the optimal path.

Here's a paper on the algorithm you'll need to figure it out.

[Ekku Zakku]

Here's a paper on the algorithm you'll need to figure it out.

Damn o_o remind me to never get into the space industry... I hate maths XD

[JakeGrey]

I believe the argument for beginning your gravity turn after the 10km mark is that the atmospheric drag is much lower, meaning that there's less chance of ripping a less-than-perfectly stable rocket design apart if you overcook it a few degrees. You also don't want to be trying any delicate manouevres until your solid boosters have flamed out and been safely jettisoned.

[KevinTMC]

I believe the argument for beginning your gravity turn after the 10km mark is that the atmospheric drag is much lower, meaning that there's less chance of ripping a less-than-perfectly stable rocket design apart if you overcook it a few degrees.

Yup. That's why I don't risk an earlier turn unless I'm flying a smallish rocket.

Also, it's my understanding that the bigger the beast, the more urgent it is to get it out of the lower atmosphere...and straight up is the fastest way.

[Ekku Zakku]

Yup. That's why I don't risk an earlier turn unless I'm flying a smallish rocket.

Also, it's my understanding that the bigger the beast, the more urgent it is to get it out of the lower atmosphere...and straight up is the fastest way.

Yeah, with me if I end up starting a gravity turn too early, it's generally because I've got too low of a TWR, and in that case going sideways too early does nothing good at all.

[nhnifong]

Yeah, with me if I end up starting a gravity turn too early, it's generally because I've got too low of a TWR, and in that case going sideways too early does nothing good at all.

Seems that speed is really the variable that determines when you can start your turn.