Efficient ways to get into orbit (Stock KSP)

[AeroSky]

Hello!

What are some efficient ways to get into stock KSP orbit? Please list them in step by step fashion as much as possible

I've forgotten how to manually get into orbit after using MechJeb a little too much.....

Thanks!

[antipro]

For what I understand the most efficient way to get into a LKO is the gravity turn maneuver.
https://en.wikipedia.org/wiki/Gravity_turn

" It is a trajectory optimization that uses gravity to steer the vehicle onto its desired trajectory. It offers two main advantages over a trajectory controlled solely through the vehicle's own thrust. First, the thrust is not used to change the spacecraft's direction, so more of it is used to accelerate the vehicle into orbit. Second, and more importantly, during the initial ascent phase the vehicle can maintain low or even zero angle of attack."

So probably you have to take off, then you reach 50m/s or so and immediately turn the vehicle 20° or so east direction, SAS prograde and let the gravity steers for you.
Speed and inclination strongly depend on your vehicle properties like TWR, mass, air resistance, etc...

Edited December 14, 2020 by antipro

[AeroSky]

Yes, I've been playing KSP for quite a while now, so I know that

But what do I do if my rocket tips over while attempting a manual gravity turn?

[jimmymcgoochie]

As a general rule of thumb- accelerate vertically to between 50 and 100m/s*, turn to between 5 and 15 degrees*, hold surface prograde until the navball automatically switches to orbital then hold orbital prograde until your apoapsis is the same as your desired periapsis, coast to apoapsis, burn prograde until you get the desired orbit.

* pitch speed and angle are very dependent on the individual rocket- TWR and drag (especially fairing drag)  are your main factors, so higher TWR and less drag will allow you to turn earlier and steeper. Turn too much and you level off in the atmosphere and can easily burn up, turn too little and you waste fuel fighting gravity.

[antipro]

11 minutes ago, AeroSky said:

But what do I do if my rocket tips over while attempting a manual gravity turn?

you have to follow a simple concept: build your rocket like a dart or an arrow, that have a big mass on top and large drag surface on the back.
CoM always have to stay on top of CoL.

Edited December 14, 2020 by antipro

[AeroSky]

4 minutes ago, jimmymcgoochie said:

pitch speed and angle are very dependent on the individual rocket- TWR and drag (especially fairing drag)  are your main factors, so higher TWR and less drag will allow you to turn earlier and steeper. Turn too much and you level off in the atmosphere and can easily burn up, turn too little and you waste fuel fighting gravity.

Hmm. How do I calculate (or how do I know) the TWR, drag, aerodynamics, etc. of my rocket? The only thing I understand is that you should turn earlier if your rocket is going up faster (referring to the higher TWR).

5 minutes ago, antipro said:

build your rocket like a dart or an arrow,

That would be much easier if I had sounding rocket parts or 0.35m (or whatever diameter sounding rockets are) diameter rocket parts. Those look like needles.

[antipro]

3 minutes ago, AeroSky said:

How do I calculate (or how do I know) the TWR, drag, aerodynamics, etc. of my rocket?

In ksp stock the TWR, isp, dV and thrust are reported on each stage, here:

 

for more data use KER

 

[AeroSky]

1 minute ago, antipro said:

In ksp stock the TWR, isp, dV and thrust are reported on each stage, here:

I'm pretty sure that isn't 100% accurate, so I'll just use trusty Kerbal Engineer!

Thanks for all the help! I'd better go read some books about aerodynamics to get better at this 

Also, I assume a TWR of 1.4 to 1.5 is fine, right?

 

[king of nowhere]

3 hours ago, AeroSky said:

Yes, I've been playing KSP for quite a while now, so I know that

But what do I do if my rocket tips over while attempting a manual gravity turn?

if it tips because it is aerodinamically unstable, you fix the rocket. if you can't fix the rocket (say, you lack the technologies) then you don't make a gravity turn, it's going to be more expensive but you have no other choices. if you tipped because you turned too much, you restart the flight and try to make a better trajectory

[Zhetaan]

3 hours ago, AeroSky said:

Also, I assume a TWR of 1.4 to 1.5 is fine, right?

That is perfectly acceptable, and about in the middle of the range that people generally recommend for those starting out with this.

3 hours ago, AeroSky said:

Hmm. How do I calculate (or how do I know) the TWR, drag, aerodynamics, etc. of my rocket? The only thing I understand is that you should turn earlier if your rocket is going up faster (referring to the higher TWR).

Others have mentioned Kerbal Engineer, but your question asks for stock, so aside from the thrust-to-weight readout that is now stock, your other option is to calculate it by hand.  That's not too difficult; KSP gives you the thrust values for each engine in the VAB.  You'll want the (atm) value for launches, rather than the vacuum value.  Add up the thrust of all of the engines that light in the first stage, and that's your total rocket thrust.  I believe that the VAB has a rocket information readout that gives you that total, so you may want to use it.  Now take the weight of the vessel, which is the fully-fuelled (wet) mass (also found in the VAB), multiplied by the acceleration due to gravity where you are, which is Kerbin sea level or 9.80665 m/s².  Divide the thrust by the weight, and you have the thrust-to-weight ratio.

Keep in mind that the thrust-to-weight changes dynamically as you fly.  As you rise out of the atmosphere, your thrust increases and your weight decreases; both of these changes drive your thrust-to-weight up.  Once you get an appreciable fraction of the way to orbit, thrust-to-weight ceases to be so important; your second stage, for example, can even have less than 1 and still make orbit provided that you get enough horizontal velocity from your first stage.

Drag is much more dynamic than thrust-to-weight.  There's a reason the field of study is called aerodynamics, after all.  What this means for you is that you can't calculate it.  Drag is dependent on more factors than you can access, and so your only option is to rely on a mod that calculates or reports it for you.  Yes, it can be done (the game does it, after all), but this is one of those things that really relies on the computer part of your gaming machine.

3 hours ago, AeroSky said:

Thanks for all the help! I'd better go read some books about aerodynamics to get better at this 

I encourage you to do so, but you should know that it is not for the fainthearted; aerodynamics is one area of physics where we have persistent unsolved problems (turbulence in particular; some physicists think we'll have a Grand Unified Theory of Everything before we solve turbulence).  I will warn you that if you get very far into it, then you're going to find a lot more places where KSP uses approximations and other shortcuts to avoid the realities of just how complex aerodynamics really is.

Realistically speaking, you don't need to know aerodynamics to understand the basic principles at work here.  'Pointy rockets work better' is often the overall design principle, and that works just fine in KSP (also in reality; look at a few pictures of the Mercury-Redstone, Gemini-Titan, and Apollo-Saturn rockets, and you'll see just how much the Space Shuttle is an aberrant weirdo in the American space program--but even the Shuttle has pointy parts).  The main concerns to keep in mind are that you want to concentrate your drag and your thrust behind your mass.  This is sometimes difficult to do because fairings are somewhat draggy and engines are heavy, but the solutions to that are fins and payload.  It helps to keep your payload near to the same diameter as the rocket under it, too, so don't have giant fairing balls on top of spindly rockets.  There are exceptions to this principle, which you will encounter if and when you ever decide to try your hand at spaceplanes (see above re: Space Shuttle), but for traditional pointy-bit-goes-up rockets, it'll serve you in good stead.

 

Good luck!

[paul_c]

A rocket shouldn't tip over in a true gravity turn because the gravity turn, in theory, applies the thrust through the centre of the mass. Its one gradual smooth turn once its been initiated. However with the WASD controls applying 0%-100%-0%-100% of turn, its a limitation of KSP. But its worth remembering it ought to be smooth.

As a VERY rough guide, I've had success with trying to "hit":

30deg at 15,000m
45deg at 25,000m
60deg at 35,000m

[JoeSchmuckatelli]

7 hours ago, AeroSky said:

Yes, I've been playing KSP for quite a while now, so I know that

But what do I do if my rocket tips over while attempting a manual gravity turn?

• You need drag at the back (tail fins). 
• You need weight at the bottom (COG lower than center). 
• You need to reduce drag at the top (farings, etc) 
• You need to have enough thrust and vectoring at the bottom to overcome failures elsewhere

I throw some pretty big craft up, and as a clumsy Neanderthal player, I still succeed.  I often start my pitch over at 30m/s.  My launches are not always the most efficient - but they work.

[Spricigo]

On 12/14/2020 at 6:42 AM, AeroSky said:

But what do I do if my rocket tips over while attempting a manual gravity turn?

Revert to VAB and fix the design flaws.

One of the big mistakes of inexperienced players is expecting a lot of "piloting" during the launch when in fact an efficient launch follow a very smooth trajectory to orbit with little to no control input, nothing more than a nudge in the right direction shortly after taking off. 

In some extreme cases not even a control point is required.

Spoiler

 

 

Edited December 15, 2020 by Spricigo

[ConArt70]

I keep my TWR just under 1.6 and go straight up until I'm travelling at 100m/s. Then pitch over ten degrees, lock to prograde and do nothing other than reduce thrust to keep it under 1.6. Generally I'm pitched over to fourty five degrees by the time I get to 15km. MECO at 80km and then burn prograde at apo to circularise. 

Edited December 15, 2020 by ConArt70