I can't figure out my attitude

[KrisKelvin]

When I go into orbit, I tend to ascend vertically to about 30km then pitch over to about 45 for a bit then cut the engines and time warp to the apogee point so I can create an orbit.

My attitude needs to be about 90 degrees (parallel to the earth's surface) before I burn so I can open out the arc into a circle on the other side of the earth.

But in map view, I can't see my attitude relative to the earth so I don't know if I'm firing prograde (which is what I want) or retrograde (which I don't!). 

I realise I have the nav ball, but once I am on my arc the ball starts to move so 90 degrees ain't 90 relative the earth any more.

Any ideas?

[Vanamonde]

I'm having difficulty picturing what you're describing, but this is actually what the navball was designed to help with. Keep flying toward 90 as it is still east regardless of your altitude. 

[KrisKelvin]

9 minutes ago, Vanamonde said:

I'm having difficulty picturing what you're describing, but this is actually what the navball was designed to help with. Keep flying toward 90 as it is still east regardless of your altitude. 

Ok, I have just discovered there is a handy prograde symbol on the navball. So to circularise my orbit I just aim on that and burn. 

My difficultly was not knowing what orientation the ship was in relative to my orbit (so I couldn't tell when to burn). A burn facing toward the planet would not be helpful!!

Thanks I think I have it figured out now.

[AHHans]

1 hour ago, KrisKelvin said:

Thanks I think I have it figured out now.

Great!

Just as a general advice: it helps a lot to learn how to read the navball. I fly most maneuver nearly exclusively with the Information I get from the navball.

Another comment that I have is that the ascent profile that you described (straight up to 30 km, then pitch over 45 deg) if fairly inefficient. (But it works, so don't sweat it!) It is more efficient to pitch over much sooner but not so far, and then follow the prograde direction until you are in orbit. Pitching about 5-10 deg as soon as your rocket is at 50 - 100 m/s speed and then following the prograde vector once it is down to your pitch angle is usually a good strategy. But the exact parameters depend on the rocket (how much TWR and how much drag it has during its flight). Feel free to experiment.

Earlier this year we had a challenge to find the best launch profile for one of the stock craft:

 

[KrisKelvin]

12 hours ago, AHHans said:

....and then following the prograde vector once it is down to your pitch angle

Thanks so much for the advice (people are super helpful here!!). But I don't quite understand the underlined part. Could you clarify what you mean? Surely if I am aligning on the prograde marker, my pitch always be the pitch angle by definition (won't it?)

[AHHans]

1 hour ago, KrisKelvin said:

But I don't quite understand the underlined part.

Sorry, I guess in trying to be more precise I made it unclear.

What I meant is: when you go straight up and then pitch over, then at first your prograde vector will still point straight up and only over time it will come down as you gather horizontal velocity. So don't pitch a few degrees and then go back to straight up just because your prograde vector points there - e.g. by pitching and then immediately hitting the SAS follow-prograde button.

[JoeSchmuckatelli]

3 hours ago, KrisKelvin said:

Thanks so much for the advice (people are super helpful here!!). But I don't quite understand the underlined part. Could you clarify what you mean? Surely if I am aligning on the prograde marker, my pitch always be the pitch angle by definition (won't it?)

I struggled with this too - but it's pretty easy. 

 

If you are looking at a top down view of the navball before & during the first seconds of launch you should see the prograde marker dead center. When you get to 30m/s or so, if you pitch the nose to the east you should see the level flight indicator (if that's what it's called - the shrugging guy shaped doohickey) - that thing moves in time with your key inputs... But the prograde marker lags behind. 

So what you do is, somewhere between 30 m/s and 100 m/s is pitch the nose East about 10 - 15 degrees, wait for the prograde marker to catch up, and then you can manually keep the dot inside the prograde ball (for SAS only pilots} or click on 'hold prograde' (for better pilots) until you get ready for the circ burn (unchecked prograde btw) 

 

Saves tons of fuel 

[KrisKelvin]

1 hour ago, JoeSchmuckatelli said:

I struggled with this too - but it's pretty easy. 

 

If you are looking at a top down view of the navball before & during the first seconds of launch you should see the prograde marker dead center. When you get to 30m/s or so, if you pitch the nose to the east you should see the level flight indicator (if that's what it's called - the shrugging guy shaped doohickey) - that thing moves in time with your key inputs... But the prograde marker lags behind. 

So what you do is, somewhere between 30 m/s and 100 m/s is pitch the nose East about 10 - 15 degrees, wait for the prograde marker to catch up, and then you can manually keep the dot inside the prograde ball (for SAS only pilots} or click on 'hold prograde' (for better pilots) until you get ready for the circ burn (unchecked prograde btw) 

 

Saves tons of fuel 

Thanks. So should I shut off the engines at a certain height and then coast to the apoapsis to do the circularization burn? Presumably I shouldn't use the engines all the way? What height should I shut off at? I am trying to figure out the most economical way of getting into orbit.

[AHHans]

1 hour ago, KrisKelvin said:

Thanks. So should I shut off the engines at a certain height and then coast to the apoapsis to do the circularization burn? Presumably I shouldn't use the engines all the way? What height should I shut off at? I am trying to figure out the most economical way of getting into orbit.

You can set the window in the lower left of the screen to "Maneuver Mode" and then to display you current Apoapsis, Periapsis, and the times to reach them. You want the time to apoapsis to increase or stay constant until your apoapsis is where you want your orbit to be. Then you can switch off the engines and coast to your circularization burn. I suggest to first try to do this and get a feel for that.

Then you can refine it even more and try to keep the time to apoapsis from getting too high - having it at just more than 1 min is a good value to aim for. The most efficient way for this with a well built rocket is to pitch over the right amount so that you don't get much over that without throttling down. An easier way to do this is to throttle down when your time to apoapsis gets too high, i.e. to use the throttle to manage your time to apoapsis. 

Edited May 26, 2020 by AHHans

[JoeSchmuckatelli]

1 hour ago, KrisKelvin said:

Thanks. So should I shut off the engines at a certain height and then coast to the apoapsis to do the circularization burn? Presumably I shouldn't use the engines all the way? What height should I shut off at? I am trying to figure out the most economical way of getting into orbit.

So - if looking between what I write and what AHHans writes - go with his.

But what I do as a duffer is switch between map and ship view for the first couple of moments - looking for when I see the white drag lines that show up @  300 m/s to let me know when to throttle down the liquid fueled engine and to know when to expect the SRBs to expend (I generally ramp up the throttle just before I dump them).  Then back to map view and watch my apoapsis and shut off about 75k, letting the rocket coast.  Then I'm immediately opening a maneuver node at apoapsis to get the system to calculate a circular burn.  When I see the perapsis is in space and I have an orbit  I start driving the flight indicator pip to line up with the blue indicator.  Remember - if you have Hold Prograde selected - your pilot will fight you so switch back to SAS... Then I calculate 1/2 the burn and start the burn at t- that number. 

 

It works. 

 

But FYI - AHHans is one of the guys I listen to for advice - so if my duffer method helps, great, but if you want to get gudder, look to him! 

[AHHans]

35 minutes ago, JoeSchmuckatelli said:

Then back to map view and watch my apoapsis

That used to be needed, but recently @SQUAD introduced the maneuver view that can display your apoapsis height and time to apoapsis in the ship view, so there is less need to switch to map view.

38 minutes ago, JoeSchmuckatelli said:

Then I calculate 1/2 the burn and start the burn at t- that number. 

If you switch on "Show Extended Burn Indicator" then you can have the the game do that bit of math for you. And more importantly: have the "warp to next maneuver" stop 1 min before it is time to start, and not 1 min before the maneuver.

And while you are in the settings: switch on "Advanced Tweakables" if you haven't done that already. If you are interested enough in KSP to get here to the Forums, then you'll want that sooner or later.

[Rhomphaia]

6 minutes ago, AHHans said:

That used to be needed, but recently @SQUAD introduced the maneuver view that can display your apoapsis height and time to apoapsis in the ship view, so there is less need to switch to map view.

If you switch on "Show Extended Burn Indicator" then you can have the the game do that bit of math for you. And more importantly: have the "warp to next maneuver" stop 1 min before it is time to start, and not 1 min before the maneuver.

And while you are in the settings: switch on "Advanced Tweakables" if you haven't done that already. If you are interested enough in KSP to get here to the Forums, then you'll want that sooner or later.

Warp to next maneuver stops warp 1 minute before the estimated time to start regardless of whether you have extended burn indicator on or not.  Personally I prefer to leave it off, since if you are coasting the burn times tend to be calculated using the Sea level thrust of the engines until you pass 70km, doesn't account for cosine losses and is easily confused by complex staging.

[KrisKelvin]

25 minutes ago, AHHans said:

That used to be needed, but recently @SQUAD introduced the maneuver view that can display your apoapsis height and time to apoapsis in the ship view, so there is less need to switch to map view.

If you switch on "Show Extended Burn Indicator" then you can have the the game do that bit of math for you. And more importantly: have the "warp to next maneuver" stop 1 min before it is time to start, and not 1 min before the maneuver.

And while you are in the settings: switch on "Advanced Tweakables" if you haven't done that already. If you are interested enough in KSP to get here to the Forums, then you'll want that sooner or later.

Umm... ok. Not sure how much of this I understand, but I'll try what you suggested.. I think.

1 hour ago, JoeSchmuckatelli said:

white drag lines

what are white drag lines? Do you mean the air resistance patterns around the ship when passing through MaxQ?

[KrisKelvin]

1 hour ago, AHHans said:

You can set the window in the lower left of the screen to "Maneuver Mode" and then to display you current Apoapsis, Periapsis, and the times to reach them. You want the time to apoapsis to increase or stay constant until your apoapsis is where you want your orbit to be. Then you can switch off the engines and coast to your circularization burn. I suggest to first try to do this and get a feel for that.

Then you can refine it even more and try to keep the time to apoapsis from getting too high - having it at just more than 1 min is a good value to aim for. The most efficient way for this with a well built rocket is to pitch over the right amount so that you don't get much over that without throttling down. An easier way to do this is to throttle down when your time to apoapsis gets too high, i.e. to use the throttle to manage your time to apoapsis. 

Ok so I recorded my attempt using the maneuver thing for the first time (so much easier than constantly mousing over the ap and pe points!). Can you tell me if I have done anything wrong? I started the circ burn a bit before reaching the apoapsis (because sometimes I leave it too late and just power back down to the planet!)

 

Here is the recording https://drive.google.com/open?id=1sg_CPdDx_PU98WIsTzHu3C0hndUw3-UE

Thanks

Edited May 26, 2020 by KrisKelvin

[Vanamonde]

Here's a guide I made a while back. It hasn't been updated for a long time, but I believe everything in it is still current. 

 

[JoeSchmuckatelli]

2 hours ago, KrisKelvin said:

...

what are white drag lines? Do you mean the air resistance patterns around the ship when passing through MaxQ?

Yeah - if by MaxQ you mean 300m/s ASL & etc when you get the animation showing where your rocket / plane is going supersonic / dragging -  those things.  I'm not completely up on all the terminology.

 

Also, re above: you can RMB on the Pe or Ap and the numbers will become persistent: really helps when fiddling with the maneuver nodes!  Also works with ascending/descending nodes

From your video: you can more aggressively tilt your rocket over to a full 10-15 degrees to take advantage of the gravity turn.  Like at 30m/s.  Also, it looks (to me) that you get going to fast too low; the drag lines I was talking about show up when you're still in the 3k altitude zone.  When I see those, I throttle back to save fuel.  IOW - you're going so fast in thick atmosphere that you're both fighting gravity and drag, and burning fuel to win.  Also, by not getting fully into the 10-15 degree turn, along with your speed, by 6k you're still pretty much vertical attack - and not in a gravity turn, which carries out through your whole initial burn.  The gravity turn usually burns longer, but your arc also becomes way longer (flatter)  because you are actually converting some of the burn time in the atmosphere into lateral speed, not just vertical speed - which in turn means less fuel used to circularize.

From what I saw, you're still in the burn straight up, turn 90 style, when you could be going up at a 'varies through 45ish' angle or so for most of the way.

I can't critique the rest: you made it to orbit!  (I like using maneuver nodes, but saw that you used the technique described by AHHans -- and it worked)

 

EDIT - you can see a gravity turn in this vid.  He attacks shallow (5 deg) but it works - you can watch the angle of attack during his burn.  

 

Edited May 26, 2020 by JoeSchmuckatelli

[KrisKelvin]

26 minutes ago, JoeSchmuckatelli said:

Yeah - if by MaxQ you mean 300m/s ASL & etc when you get the animation showing where your rocket / plane is going supersonic / dragging -  those things.  I'm not completely up on all the terminology.

 

Also, re above: you can RMB on the Pe or Ap and the numbers will become persistent: really helps when fiddling with the maneuver nodes!  Also works with ascending/descending nodes

From your video: you can more aggressively tilt your rocket over to a full 10-15 degrees to take advantage of the gravity turn.  Like at 30m/s.  Also, it looks (to me) that you get going to fast too low; the drag lines I was talking about show up when you're still in the 3k altitude zone.  When I see those, I throttle back to save fuel.  IOW - you're going so fast in thick atmosphere that you're both fighting gravity and drag, and burning fuel to win.  Also, by not getting fully into the 10-15 degree turn, along with your speed, by 6k you're still pretty much vertical attack - and not in a gravity turn, which carries out through your whole initial burn.  The gravity turn usually burns longer, but your arc also becomes way longer (flatter)  because you are actually converting some of the burn time in the atmosphere into lateral speed, not just vertical speed - which in turn means less fuel used to circularize.

From what I saw, you're still in the burn straight up, turn 90 style, when you could be going up at a 'varies through 45ish' angle or so for most of the way.

I can't critique the rest: you made it to orbit!  (I like using maneuver nodes, but saw that you used the technique described by AHHans -- and it worked)

 

EDIT - you can see a gravity turn in this vid.  He attacks shallow (5 deg) but it works - you can watch the angle of attack during his burn.  

 

Thanks so much. I really appreciate how helpful everyone is on here with all my dumb questions! :-)

[AHHans]

2 hours ago, KrisKelvin said:

Can you tell me if I have done anything wrong?

You got into orbit, so you didn't do anything wrong!(*)

The main issue that I noticed is that the rocket has a very high TWR. Just the SRBs alone give it an acceleration of 3g directly off the launchpad, and peaking near 6g. (Just be glad that Kerbals are not as squishy as humans. SCNR!) For that case the rule-of-thumb numbers I mentioned (for when you need to pitch and how far) are not the best anymore. Such a high acceleration at the start is always wasteful because you become too fast too low in the atmosphere where drag is much stronger, and you need to carry a too heavy engine around with you.

My suggestion is to just remove the SRBs, you don't need them to get to orbit. (I just tried a re-creation of that rocket.) And that way it is more of a challenge. If you want to make it a bit easier, then remove the extra reaction wheels, the gimbal on the swivel and the terrier give you enough control authority.
[Edit:] O.K. if you do the "circularization" burn right the rocket without the SRBs even has enough dV to get into orbit when going straight up to an AP of 85km and then starting the circularization once it it out of the atmosphere.

2 hours ago, KrisKelvin said:

I started the circ burn a bit before reaching the apoapsis (because sometimes I leave it too late and just power back down to the planet!)

That's fine! I don't think you could gain significant amounts of efficiency by doing that better.

P.S. (*)You did several things right though! Starting by playing KSP in the first place.

Edited May 26, 2020 by AHHans

[bewing]

My attitude is  .

 

[Zhetaan]

On 5/25/2020 at 2:35 PM, KrisKelvin said:

When I go into orbit, I tend to ascend vertically to about 30km then pitch over to about 45 for a bit then cut the engines and time warp to the apogee point so I can create an orbit.

My attitude needs to be about 90 degrees (parallel to the earth's surface) before I burn so I can open out the arc into a circle on the other side of the earth.

But in map view, I can't see my attitude relative to the earth so I don't know if I'm firing prograde (which is what I want) or retrograde (which I don't!). 

I realise I have the nav ball, but once I am on my arc the ball starts to move so 90 degrees ain't 90 relative the earth any more.

Any ideas?

My first suggestion would be to check a mirror for your facial expression, but it appears that @bewing beat me to that joke.

One thing that I think is important is something that arose because of your confusion in reading the navball.  Attitude is the direction in which you point, but when you talk about 90 degrees being parallel to the planet's surface, you're missing some terminology.  Your 90-degrees-parallel is actually zero degrees of pitch.  Ninety degrees of pitch is straight up (although once you are in orbit, it is probably more appropriate to say that it is straight out).  However, pitch is often considered in relative terms (pitch down three degrees from prograde, for example).

I will say that, in concert with @AHHans, your rocket is extremely high-thrust off the pad.  It's not enough to begin tearing pieces off or cause overheating problems, but one of the things to remember about rocket control is that fins (or, in this case, the solid rocket boosters which on this design work to a similar purpose) help stability by introducing drag at the aft of the rocket.  However, drag increases with thrust.  This is often a good thing, because it means that at least until it causes heating problems, the faster you go, the more stable your rocket is in its flight, but you then get new problems when you try to turn and find that your rocket is so stable that it cannot turn--or, worse, tears itself apart when you try.

Your rocket is totally overpowered for reaching Kerbin orbit, but perhaps you want to do something else with it--add a solar panel and it easily has enough propellant to take a sightseeing tour of Kerbin's moons.  If we assume that the rocket that you have is the rocket that you want to build, then there are a number of ways to get better performance from it.  One way is to reduce the thrust of the solid rocket boosters:  you can reduce that thrust by about half and still be slightly overpowered at the pad.  You can do this with thrust limiters, but you can also do it by splitting the solid rocket boosters into two stages.  Light one pair at launch and the second pair as the first burn out.

Another choice is to improve your flight profile.  You have a mostly-up path, and since you got it into space, that obviously worked, but there is nothing wrong with improvement.  For a typical well-designed rocket, you should build up speed to about 100 m/s or reach an altitude of 1,000 metres, whichever comes first (and I usually try to get both at the same time), and then gently tip the rocket about three degrees to the east of straight up.  Then you keep it turning gently so that you reach forty-five degrees at about 10 km and approach horizontal at about 30 km.  That may seem a bit low to you, but remember that for one thing, that altitude can be adjusted, and for another, orbit is not about going up, it's about going sideways.  The idea is to try to make this as smooth a motion as possible.  Your rocket is overpowered enough to potentially make that difficult, but on the other hand, it's also over-fuelled enough to give you lots of room for error, which means lots of room to learn what works and what does not.

However, I will say that for your rocket, you will want to turn a bit harder and earlier than I would normally recommend.  The reason is because the ideal rocket only should use enough upward thrust to counter the pull of gravity, and it should put the rest to moving horizontally, because horizontal velocity is what puts you into an orbit.  Since your rocket has an abundance of thrust, it can put more to horizontal velocity while still countering gravity.

Lastly, I typically try to keep my apoapsis approximately 30 seconds ahead of me while in the upper atmosphere, until it reaches the target altitude.

On 5/26/2020 at 10:03 AM, KrisKelvin said:

Thanks. So should I shut off the engines at a certain height and then coast to the apoapsis to do the circularization burn? Presumably I shouldn't use the engines all the way? What height should I shut off at? I am trying to figure out the most economical way of getting into orbit.

Real-life rockets usually burn all the way to circularisation.  However, that is because of several reasons.  One of them is the practical inability of rocket engines to be shut off and reignited an infinite number of times:  for a lot of (even most) rockets, the engines are ignited once and that's it.  The Titan and Saturn rockets worked this way.  Even the Space Shuttle Main Engines worked this way:  they were ignited by external igniters on the ground--they did not have the ability to start themselves at all.  Restartable engines do exist (the SPS engine that Apollo spacecraft used in lunar orbit is one example) but they introduce a lot of engineering complexity--especially since rockets typically need to enter orbit only once.

Another reason is that Earth is much larger than Kerbin.  Kerbin has a radius of 600 kilometres.  Earth's radius is nearly 6400 kilometres.  Even though your gravity and altitude above the surface is the same, the curvature of the planet is much more pronounced in KSP, which means that you will get much shorter orbital periods.  That, in turn, means that it doesn't take so much to make a circular orbit--and the difference is enough that, for the available thrust, you often end up needing to simply shut the engines off and coast to a better place to complete your burn.

To actually answer your question, typically, yes, you should shut your engines off and coast.  However, it has nothing to do with your altitude, but rather is tied to the altitude of the orbit that you want.  If you want a 75 km orbit, then you should shut down your engines when the apoapsis reaches 75 km.  If you want a 300 km orbit, then you should shut down when your apoapsis reaches 300 km.  I will note that if you are still in the atmosphere when you do this, then your apoapsis will begin to drop because of air resistance slowing your ascent, but the remedy to that is to simply burn for an apoapsis slightly above what you really want--for example, perhaps 80 km when the intended final altitude is 75 km.

19 hours ago, KrisKelvin said:

Thanks so much. I really appreciate how helpful everyone is on here with all my dumb questions! :-)

Helping is what we do!  But please don't undersell yourself:  you left the dumb questions behind when you started to study rocket science.

[KrisKelvin]

2 hours ago, Zhetaan said:

My first suggestion would be to check a mirror for your facial expression, but it appears that @bewing beat me to that joke.

One thing that I think is important is something that arose because of your confusion in reading the navball.  Attitude is the direction in which you point, but when you talk about 90 degrees being parallel to the planet's surface, you're missing some terminology.  Your 90-degrees-parallel is actually zero degrees of pitch.  Ninety degrees of pitch is straight up (although once you are in orbit, it is probably more appropriate to say that it is straight out).  However, pitch is often considered in relative terms (pitch down three degrees from prograde, for example).

I will say that, in concert with @AHHans, your rocket is extremely high-thrust off the pad.  It's not enough to begin tearing pieces off or cause overheating problems, but one of the things to remember about rocket control is that fins (or, in this case, the solid rocket boosters which on this design work to a similar purpose) help stability by introducing drag at the aft of the rocket.  However, drag increases with thrust.  This is often a good thing, because it means that at least until it causes heating problems, the faster you go, the more stable your rocket is in its flight, but you then get new problems when you try to turn and find that your rocket is so stable that it cannot turn--or, worse, tears itself apart when you try.

Your rocket is totally overpowered for reaching Kerbin orbit, but perhaps you want to do something else with it--add a solar panel and it easily has enough propellant to take a sightseeing tour of Kerbin's moons.  If we assume that the rocket that you have is the rocket that you want to build, then there are a number of ways to get better performance from it.  One way is to reduce the thrust of the solid rocket boosters:  you can reduce that thrust by about half and still be slightly overpowered at the pad.  You can do this with thrust limiters, but you can also do it by splitting the solid rocket boosters into two stages.  Light one pair at launch and the second pair as the first burn out.

Another choice is to improve your flight profile.  You have a mostly-up path, and since you got it into space, that obviously worked, but there is nothing wrong with improvement.  For a typical well-designed rocket, you should build up speed to about 100 m/s or reach an altitude of 1,000 metres, whichever comes first (and I usually try to get both at the same time), and then gently tip the rocket about three degrees to the east of straight up.  Then you keep it turning gently so that you reach forty-five degrees at about 10 km and approach horizontal at about 30 km.  That may seem a bit low to you, but remember that for one thing, that altitude can be adjusted, and for another, orbit is not about going up, it's about going sideways.  The idea is to try to make this as smooth a motion as possible.  Your rocket is overpowered enough to potentially make that difficult, but on the other hand, it's also over-fuelled enough to give you lots of room for error, which means lots of room to learn what works and what does not.

However, I will say that for your rocket, you will want to turn a bit harder and earlier than I would normally recommend.  The reason is because the ideal rocket only should use enough upward thrust to counter the pull of gravity, and it should put the rest to moving horizontally, because horizontal velocity is what puts you into an orbit.  Since your rocket has an abundance of thrust, it can put more to horizontal velocity while still countering gravity.

Lastly, I typically try to keep my apoapsis approximately 30 seconds ahead of me while in the upper atmosphere, until it reaches the target altitude.

Real-life rockets usually burn all the way to circularisation.  However, that is because of several reasons.  One of them is the practical inability of rocket engines to be shut off and reignited an infinite number of times:  for a lot of (even most) rockets, the engines are ignited once and that's it.  The Titan and Saturn rockets worked this way.  Even the Space Shuttle Main Engines worked this way:  they were ignited by external igniters on the ground--they did not have the ability to start themselves at all.  Restartable engines do exist (the SPS engine that Apollo spacecraft used in lunar orbit is one example) but they introduce a lot of engineering complexity--especially since rockets typically need to enter orbit only once.

Another reason is that Earth is much larger than Kerbin.  Kerbin has a radius of 600 kilometres.  Earth's radius is nearly 6400 kilometres.  Even though your gravity and altitude above the surface is the same, the curvature of the planet is much more pronounced in KSP, which means that you will get much shorter orbital periods.  That, in turn, means that it doesn't take so much to make a circular orbit--and the difference is enough that, for the available thrust, you often end up needing to simply shut the engines off and coast to a better place to complete your burn.

To actually answer your question, typically, yes, you should shut your engines off and coast.  However, it has nothing to do with your altitude, but rather is tied to the altitude of the orbit that you want.  If you want a 75 km orbit, then you should shut down your engines when the apoapsis reaches 75 km.  If you want a 300 km orbit, then you should shut down when your apoapsis reaches 300 km.  I will note that if you are still in the atmosphere when you do this, then your apoapsis will begin to drop because of air resistance slowing your ascent, but the remedy to that is to simply burn for an apoapsis slightly above what you really want--for example, perhaps 80 km when the intended final altitude is 75 km.

Helping is what we do!  But please don't undersell yourself:  you left the dumb questions behind when you started to study rocket science.

Thanks so much for taking the time to write all this. As I wait for the SpaceX lift off, I'm going to try some of this out.

 

23 hours ago, AHHans said:

The main issue that I noticed is that the rocket has a very high TWR. Just the SRBs alone give it an acceleration of 3g directly off the launchpad, and peaking near 6g. (Just be glad that Kerbals are not as squishy as humans. SCNR!) For that case the rule-of-thumb numbers I mentioned (for when you need to pitch and how far) are not the best anymore. Such a high acceleration at the start is always wasteful because you become too fast too low in the atmosphere where drag is much stronger, and you need to carry a too heavy engine around with you.

My suggestion is to just remove the SRBs, you don't need them to get to orbit. (I just tried a re-creation of that rocket.) And that way it is more of a challenge. If you want to make it a bit easier, then remove the extra reaction wheels, the gimbal on the swivel and the terrier give you enough control authority.
[Edit:] O.K. if you do the "circularization" burn right the rocket without the SRBs even has enough dV to get into orbit when going straight up to an AP of 85km and then starting the circularization once it it out of the atmosphere.

Ok, I'm going to remove the SRBs

[KrisKelvin]

Looking at the video Joe posted above, I see you can lock the steering to the prograde marker! That's cool. I did wonder what those things on the left of the navball were!

Although I just tried that and it doesn't get you into orbit! I was still only pitched over about 10 degrees at 100km altitude!

So when would you use that?

Edited May 27, 2020 by KrisKelvin

[JoeSchmuckatelli]

42 minutes ago, KrisKelvin said:

Looking at the video Joe posted above, I see you can lock the steering to the prograde marker! That's cool. I did wonder what those things on the left of the navball were!

Although I just tried that and it doesn't get you into orbit! I was still only pitched over about 10 degrees at 100km altitude!

So when would you use that?

It works, presuming you have enough pitch early enough to start the gravity turn.  If, on the other hand, you still have too much lift, or did not initiate the turn in time, your 'prograde progress' won't be as dramatic.  Also, if you hit Hold Prograde too early your pilot will prevent the maneuver from happening!

Way back when - before I knew about using the 'hold prograde' (or, perhaps before the marks next to the navball existed)  -- you had to manually goose it.  IOW - you had to keep tapping the W or D or whatever key you started with to keep the dot in the prograde circle, once the prograde circle caught up with your dot.  It still works.

So, what I would do, did and still do with OKTO controlled craft (pilots without Hold Prograde available) is go for 15 degree pitch (feel free to play around with the actual degrees, btw to find what works for the craft you're building... you will know if you've gone too far when your craft begins to somersault!).  The aggressive pitch,  which I used to start at 100 m/s or 1,000m has changed - now I start at about 30m/s, hold the 15 degrees until the prograde marker catches up to it and I see the craft is stable - is then (and only then) do I click 'Hold Prograde'.  If I don't have a skilled pilot, then I still have to do the watch and tap thing - because if you've done it correctly, the ship begins to turn without you doing anything; the prograde marker somewhat steadily descends from 15 through 45 and realistically all the way to 90 (which, paradoxically is actually zero as mentioned above).

 

The really nice thing - and you know you're doing it correctly, is that you end up with a really long arc; such that when your apoapsis is 75 k or so, the end of your arc is often 1/4 or more of the whole circumference of Kerbin.  That makes for a long coast up to apoapsis which lets you have the time to set up a maneuver node to circularize.

Edited May 27, 2020 by JoeSchmuckatelli

[KrisKelvin]

27 minutes ago, JoeSchmuckatelli said:

you had to manually goose it.  IOW - you had to keep tapping the W or D or whatever key you started with to keep the dot in the prograde circle, once the prograde circle caught up with your dot.  It still works.

 

Err... yes! What do you think I've been doing all this time! I assumed that was the only way of steering!

I'm afraid I don't know any of your abreviations. OKTO, IOW?

[Snark]

On 5/25/2020 at 2:35 PM, KrisKelvin said:

But in map view, I can't see my attitude relative to the earth so I don't know if I'm firing prograde (which is what I want) or retrograde (which I don't!). 

I realise I have the nav ball, but once I am on my arc the ball starts to move so 90 degrees ain't 90 relative the earth any more.

The nav ball always shows which way you're pointing relative to the ground.  The brown part is the "ground", the blue is the "sky", and the dividing line between them is the horizon.  So if you want to be pointing "horizontally", i.e. parallel to the ground, then just use WASD controls to move the crosshairs until they're on the "horizon" of the navball.

 

On 5/25/2020 at 2:35 PM, KrisKelvin said:

When I go into orbit, I tend to ascend vertically to about 30km then pitch over to about 45 for a bit then cut the engines and time warp to the apogee point so I can create an orbit.

+1 to the earlier comments that this happens to be a really inefficient path to orbit (i.e. wastes a lot of dV).  If it works for you, then great!    Just, be aware that following a different, more efficient curve would allow you to get to orbit with less fuel required, so your rocket can go farther.