I suck at getting into orbit

[Tacitus275]

I get my AP at right around 72k but as I burn trying to get an orbit, my AP moves away from me.  Closest I get is an AP of 110km and the lowest at 43k meters

 

https://imgur.com/Npqjdd8

Edited January 28, 2021 by Tacitus275

[Superfluous J]

Stop burning

Essentially your orbit there looks great, except you need a little more fuel left in your rocket when your Ap gets above 70. Make your rocket have maybe 200-300 more m/s of dV, then do what you did there only STOP BURNING when your Ap is at 80 or so.

Then coast up to that Ap, aim prograde, and burn again and your Pe will pop right out of the ground.

Edited January 28, 2021 by Superfluous J

[MKI]

 

58 minutes ago, Tacitus275 said:

I get my AP at right around 72k but as I burn trying to get an orbit, my AP moves away from me.  Closest I get is an AP of 110km and the lowest at 43k meters

 

https://imgur.com/Npqjdd8

 

Once your Ap is above 70km you can stop burning and shut down your engines so you can coast the rest of the way. Once you get to your Ap, you can re-ignite your engines prograde and circularize your orbit, permitting you have enough delta-v. As your applying your delta-v at the top of your orbit, all of that velocity should be applied horizontally, relative to the ground, thus getting you to a nice circular obit.

Continuously burning from launch will increase your Ap as you have seen, however if you apply all your velocity during ascent, your delta-v will be applied in a both horizontal and vertical direction.  The most extreme example of this would be burning all your delta-v at launch, thus making what is essentially a cannon, which creates a purely ballistic sub-orbital trajectory, or more important not a circle ;D

 

I personally over-engineer and build my rockets to reach at least 100km, at which point I can "coast" up to 100km, and continue burning whatever stages/fuel I have left. If you want to be nice to the environment, you can stage before circularizing your orbit so they continue your previous sub-orbital trajectory and thus destroyed. This is what the Space Shuttle did with its orange tank and you can also follow suite to keep your orbit nice and tidy

 

Good luck!

 

Edited January 28, 2021 by MKI
add quote

[king of nowhere]

to expand on what other said, when you burn - any kind of burn - in orbit, you are going to change the orbit on the opposite side. the place where you burn is going to stay exactly the same.

so, if you are inside an atmosphere at 40 km, you can burn as much as you want, you will raise your apoapsis but your periapsis will always stay no higher than 40 km.

for this reason you must wait until you are close to apoapsis before circularizing. when you set apoapsis at 80 km, you like that. you want that part of the orbit to stay there. so you burn in that place.

[Mikenike]

@Tacitus275

Take this thread, it has great advice.

 

 

 

[Echo__3]

Make sure you are using a good gravity turn to get into orbit efficiently. I like to place a maneuver node on my apoapsis in order to help time my orbital insertion burn.

 

[Snark]

15 hours ago, Tacitus275 said:

I get my AP at right around 72k but as I burn trying to get an orbit, my AP moves away from me.  Closest I get is an AP of 110km and the lowest at 43k meters

There are three main reasons why someone might have difficulty getting to orbit-- from your description it's not completely clear which of these you might be running into (possibly more than one):

1. A problem with rocket design (e.g. it doesn't have enough oomph to get to orbit)
2. A problem with the ascent profile during the early part of the burn (e.g. the path you take during the first 20 km or so that you're climbing)
3. A problem with orbital insertion (e.g. what you do as you raise your Ap and then circularize)

The folks who have already posted here have some excellent advice about #3, and some on #2, but it's also possible you could have an issue with #1.

Could you post a screenshot of what your rocket looks like?

Also, what does your early launch profile look like?  i.e. what's your flight path during the first 20 km or so?  (For example:  When the rocket reaches an altitude of 10 km, how fast is it going and what angle from the vertical is it?)

[Tacitus275]

6 hours ago, Snark said:

There are three main reasons why someone might have difficulty getting to orbit-- from your description it's not completely clear which of these you might be running into (possibly more than one):

1. A problem with rocket design (e.g. it doesn't have enough oomph to get to orbit)
2. A problem with the ascent profile during the early part of the burn (e.g. the path you take during the first 20 km or so that you're climbing)
3. A problem with orbital insertion (e.g. what you do as you raise your Ap and then circularize)

The folks who have already posted here have some excellent advice about #3, and some on #2, but it's also possible you could have an issue with #1.

Could you post a screenshot of what your rocket looks like?

Also, what does your early launch profile look like?  i.e. what's your flight path during the first 20 km or so?  (For example:  When the rocket reaches an altitude of 10 km, how fast is it going and what angle from the vertical is it?)

I can get really high.... my problem is circularizing the orbit.  What angle do I need to be at...  90 degrees causes me to rise higher.  I try to go slightly down, and that doesn't seem to work either.  https://imgur.com/hSTLv9j

[Echo__3]

2 minutes ago, Tacitus275 said:

I can get really high.... my problem is circularizing the orbit.  What angle do I need to be at...  90 degrees causes me to rise higher.  I try to go slightly down, and that doesn't seem to work either.  https://imgur.com/hSTLv9j

The key to getting into orbit is speed more than altitude.  You need an orbital speed around 2300m/s to get into low orbit around Kerbin. You need to go up initially to get out of the thicker parts of the atmosphere, but then you need to work on your horizontal velocity. Going up, you are fighting gravity the whole time while horizontal you are only working against drag. This is why you need to use a gravity turn.
Each craft is different depending on its TWR and aerodynamics, but I like a starting thrust to weight ratio around 1.3 and try to keep my crafts as streamline as possible. By 4 kms I try to be tilted 20 degrees, by 8km 45 degrees then generally let the craft hold prograde for the rest of the ascent. Once I get an apoapsis at my desired height (usually 80km to 100km I'll create a maneuver node on the apoapsis marker aiming for a circular orbit. Then I'll burn the maneuver node and circularize. Ideally, the circularization burn will not be very big (less than 400 m/s) due to how much the craft has already accelerated horizontally.

[Superfluous J]

1 hour ago, Tacitus275 said:

I can get really high.... my problem is circularizing the orbit.  What angle do I need to be at...  90 degrees causes me to rise higher.  I try to go slightly down, and that doesn't seem to work either.  https://imgur.com/hSTLv9j

One of the fundamental rules of orbital mechanics is, if you want to raise your Pe without changing your Ap, you do your burn at Ap.

To raise your Pe, burn PROGRADE (the marker that looks like ) when your ship is at the Ap, and the Ap is above 70km.

[Spricigo]

1 hour ago, Superfluous J said:

One of the fundamental rules of orbital mechanics is, if you want to raise your Pe without changing your Ap, you do your burn at Ap.

To raise your Pe, burn PROGRADE (the marker that looks like ) when your ship is at the Ap, and the Ap is above 70km.

∆This

The way the OP describes it seems like he is doing the circularisation  before reaching the AP. Or at least he end up doing most of the planed maneuver away from AP.  Just throttle down (or even cut the engines), keeping the apoapsis a few seconds ahead.

 

[paul_c]

Going high does not an orbit make.

The key is to go fast - horizontally.

The screenshot doesn't really give enough info (what is the Ap?) but if you are going 2165m/s with 57m/s left, you (probably - can't remember the exact number) won't get into orbit. And if you do, you won't get back out again for re-entry so you'll be stuck there for ever.

So the whole rocket might need a minor redesign to give it more performance, or you just didn't fly it efficiently (or a bit of both).

[Klapaucius]

Your post title "I suck at getting to orbit" probably describes every single one of us when we started KSP :-)

I found when learning that sometimes it is better to break things down.  As @Snarkmentioned, the rocket may be part of the issue. So, let's just take it out of the equation.  Use something like the stock Kerbal X rocket which has plenty of fuel to get to Kerbin orbit.  Once you succeed, you can then work on getting up using less and less fuel. 

You might also find it helpful to scroll through @Chequers's Orbit Boot Camp challenge.  Several entries include video, and these are rockets working on pretty tight margins. You don't need to enter, just observe what others have done.  Note their flight profiles.

In fact, while I could get to orbit, it was this challenge that taught me how to do it efficiently.

 

 

[king of nowhere]

12 hours ago, Tacitus275 said:

I can get really high.... my problem is circularizing the orbit.  What angle do I need to be at...  90 degrees causes me to rise higher.  I try to go slightly down, and that doesn't seem to work either.  https://imgur.com/hSTLv9j

it's not a matter of angle, it's a matter of doing the manuever in the right spot.

you must make the manuever as you are making it, but you must do it only when you are close to apoapsis. you are doing it in the wrong place

[Anonymous49]

On 1/28/2021 at 9:25 AM, Tacitus275 said:

I get my AP at right around 72k but as I burn trying to get an orbit, my AP moves away from me.  Closest I get is an AP of 110km and the lowest at 43k meters

 

https://imgur.com/Npqjdd8

check my thread "How to get into a circular orbit" I had the same problem but it was solved

How to get a circular orbit - Gameplay Questions and Tutorials - Kerbal Space Program Forums

use MJ, use the autopilot it will show you

On 1/12/2021 at 12:41 PM, Popestar said:

To get suborbital, use a gravity turn:

• When launching, make sure the rocket faces east.  That is, when you pitch using the S key, your rocket should turn towards the ocean.
• When you reach ~75 m/s speed, pitch east 10 degrees and hold that.
• When you hit an altitude of ~4000 meters, pitch another 10ish degrees east (you will be in the neighborhood of 20ish degrees at this point) and hold that.
• When you hit an altitude of ~10000 meters, pitch east all the way to 45 degrees and hold that.
• Pay attention to what your Ap is going to be; you may need to switch to map view or use a mod like KER or MJ.  When your Projected Ap hits ~71000 meters, kill the engine and coast.
• Now the tricky part.  Pitch to somewhere between 70 and 90 degrees, and watch the time to hit Ap.  Again, you may need to use a mod (I use MJ).  When the time to hit Ap reaches 15 or so seconds, throttle up and keep throttling until the time to hit Ap hits 25 seconds.  You may need to alter your pitch up or down so as to both not hit Ap AND not go too far beyond 25 seconds.  Several bursts like this will get your Pe to about 71000 meters and keep your Ap at/just below 80000 meters.

Keep an eye on your TWR during all of this.  On the right of the navball is the force bar, right?  That goes up the more thrust you give.  Keep the pointer in that bar just over the first tick mark, and never over the second, any time you are thrusting.

This should help you circularize.  Obviously, once you get the orbit I mentioned above, you can do small thrusts at Ap to get the Pe closer.

I hope this helps!

well yeah this works

[Spricigo]

7 hours ago, king of nowhere said:

it's not a matter of angle, it's a matter of doing the manuever in the right spot.

To be fair is both a matter of angle and doing it in the right spot.

Not only that, but his idea is technically correct, pointing the craft slightly down* is a way to prevent the apoapsis raising too much (or pointing up if one is getting past the Apoapsis before achieving orbit)  Granted, the maneuver become less efficient because cosine losses, but it actually works.

 

*I guess he is not pointing low  enough to fully compensate the misplacement of the burn.

[paul_c]

"Learn the rules before you break them".

In theory, to circularise an orbit ie raise the Pe, you want to burn exactly towards the horizon, exactly at the Ap, to boost the velocity to the needed amount (so that its a circular orbit, ie Pe rises to  match Ap).

In practice, you can't insta-burn because no such engine exists (and if it did, it would tear the spaceship apart with G forces!) but the theory is that its a point in time/space. So we burn near the Ap, in the right direction, for the right time. (Neither can you get Pe and Ap exactly the same because as you burn, the Ap will move away from you or flip to the other side of the orbit etc so you aim for nearly circular; or raise Pe 'enough').

[king of nowhere]

2 hours ago, Spricigo said:

To be fair is both a matter of angle and doing it in the right spot.

Not only that, but his idea is technically correct, pointing the craft slightly down* is a way to prevent the apoapsis raising too much (or pointing up if one is getting past the Apoapsis before achieving orbit)  Granted, the maneuver become less efficient because cosine losses, but it actually works.

 

*I guess he is not pointing low  enough to fully compensate the misplacement of the burn.

technically yes.

but then, technically, no. he can never achieve orbit while burning inside the atmosphere, not without a course correction while outside the atmosphere.