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JackBush

Still struggling to get into orbit ...

Question

I think I'm getting closer; I'm understanding what I have to do. But it's the execution. Often as I'm ascending I find my ship is passing or overshooting the Apoapsis. I came close a couple of times but missed the timing for meeting the node. But how can I keep the Ap rising without catching it and passing it?

I know you're all way past this point but I've spent days trying to understand and get to it and it's very frustrating. I don't have Mechjeb and I don't want to get it, but it's beginning to whisper to me in the back of my head. I very much like Orb8Ter's tutorial and he's gotten me the closest but there's still these little problems I come up against. And I don't seem able to conserve my fuel as he does.

Sorry to babble on.

Edited by JackBush

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A couple of observations to begin with:

.

How does this look?

GsJG2y7.jpg

Edited by Vanamonde

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I think I'm getting closer; I'm understanding what I have to do. But it's the execution. Often as I'm ascending I find my ship is passing or overshooting the Apoapsis. I came close a couple of times but missed the timing for meeting the node. But how can I keep the Ap rising without catching it and passing it?

I know you're all way past this point but I've spent days trying to understand and get to it and it's very frustrating. I don't have Mechjeb and I don't want to get it, but it's beginning to whisper to me in the back of my head. I very much like Orb8Ter's tutorial and he's gotten me the closest but there's still these little problems I come up against. And I don't seem able to conserve my fuel as he does.

Sorry to babble on.

Thank you for not getting mechjeb. Its fun to learn from scratch and that is not a jab at mechjeb.

Your apo is formed entirely from two places: 1) your vertical velocity (if no horizontal velocity exists); 2) your horizontal velocity at the apo. This is oversimplified but drives to my point.

You need high enough vertical velocity, but a fast enough horizontal velocity to prolong your time spent above a certain altitude. In essence, if you gun it straight up..sure you will make it very very high, but you are coming right back down. Similarly, if you gun it straight up, your time spent at the apo is very limited. You extend that time with horizontal velocity.

But of the two lessons above, the most important is your horizontal velocity. And you won't get 2000+ mps when you have only a couple seconds at your apo altitude to complete an orbit (no I won't say circularize. I have no idea why that is trendy to say).

Anyways, this means you need to balance your vertical velocity with your horizontal. But with an atmosphere, you need to do so delicately and not in an aggressive turn.

I shoot for 250-500 mps in vertical within the first 30sec. This is why the first stage is so important and solid booster are amazing. But you need to plan ahead for your horizontal climb while keeping in mind you move faster outside the atmosphere. In essence, make your climb nice and round, but not too round, rather than straight and pointy. This will give you ample time at apo to burn horizontally.

Walkthrough:

At takeoff, depending on the speed (if faster make it slightly more aggressive), IMMEDIATELY turn horizontally about 2+ degrees. You have little atmo resistance and you need to have gravity start helping you with your aim towards the horizon. If you turn too late, it will either be really hard to make the turn and you climb too high/sharp (if you are going fast), or you overturn and the atmo points your ship downward (if you are going too slow).

By setting the degree like this, gravity will slowly point your prograde closer and closer to the horizon as you will slowly accelerate past you 300-500 mps. If it is pointing down too quickly, a lot of the time the cure is acceleration, so just increase your thrust. But too much may kill potential delta v because of wind resistance.

By 30,000 alt, I like to be at about 45 degrees. Compensate accordingly. Slow your throttle as needed. What is important is burn time NOT speed. The longer you burn, the less resistance. Think about it: if you gun it in atmo, you are limited by terminal velocity or the lesser issue of atmo resistance not to the extent of terminal velocity. But by burning long and slow, but in a manner that still gets you out of the atmo, you save all your delta v for lower atmo/no atmo acceleration.

Keep your acceleration consistently and evenly dropping, by gravity, from the 45 deg on through the apo and speed up or slow down as needed (if your apo gets to the altitude you want, you can stop and reignite if atmo slows you down a bit). In that burn, keep the gravity turn going as much as comfortable (20 more deg by 50,000 alt, for example), and use throttle to determine your ultimate apo, pre-final horizontal burn. If you have to, aim below the horizon or higher if you are in the target apo altitude but wish to increase your horizontal acceleration. You don't have to only point prograde once in thinner air.

By the time you hit the apo, you will be at a much much higher horizontal speed, but still need to burn to get into orbit.

Burn before, through, and after the apo as needed. I like to aim so my apo stays on top of me (e.g. pointing up more, 5ish degrees, when I am close to it), but too much of this kills potential horizontal delta v accel.

I'm rushing this at work and didn't proof so I hope it makes sense.

Edited by Friend Bear

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This looks good, Hugs. How do you attach the solid boosters so you can get rid of them (without wrecking the rest of the stage)?

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This looks good, Hugs. How do you attach the solid boosters so you can get rid of them (without wrecking the rest of the stage)?

Try and have the boosters attached to the decouplers near their middles, otherwise they have a tendancy to swing inwards and take out your central stack, failing that you can use sepatrons to push them away once you have them.

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I can't help but think there should be an "exodus mode" where KSC is on Duna, and you launch rockets from Duna....

It might be a lot easier to learn things about spaceflight if you started on Duna.

Orbiting is much easier, its moon is closer and easier to get to... its moon has less gravity than Mun.. everything is much easier except landing.

Hyperedit yourself to Duna if launching from Kerbin is really too hard at this time?

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This looks good, Hugs. How do you attach the solid boosters so you can get rid of them (without wrecking the rest of the stage)?

Solid boosters are usually fine without the sepratron since they weigh so little (unless you are using huge ones from KY or NovaPunch). Just make sure you are facing prograde when decoupling and yes, that they are attached in the middle so the ejection is at their center of mass.

If you need sepratrons, you have a couple options:

1) use stock sepratrons, two to a booster, one on either side, faced so they launch the booster they are attached to away from the rest of the vessel. Have them staged with the decoupler.

Make sure you try to connect them to the booster at the booster's center of mass.

2) use KY Heavy Lifter mod. This gives sweet decoupler/sepratrons that are in a single package. The decouple also engages the sepratron booster embedded in the decoupler, itself.

- - - Updated - - -

I can't help but think there should be an "exodus mode" where KSC is on Duna, and you launch rockets from Duna....

It might be a lot easier to learn things about spaceflight if you started on Duna.

Orbiting is much easier, its moon is closer and easier to get to... its moon has less gravity than Mun.. everything is much easier except landing.

I agree. However, learning to land there as the first body with an atmosphere is ideal since it is so light and at such a low altitude. I don't see too many people leaving orbit and re-entering to design their atmosphere based craft meant for other celestial bodies, but I suppose it is possible.

Does that base mod let you do this? I can't remember what it is called, but I do think USI Kolonization has a manufacturing platform you could fly and land there, mine the place, and build, etc.

Edited by Friend Bear

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Thanks Friend Bear. No i don't have sepatrons (haven't even heard of them yet). I'll try fixing the solid boosters more carefully this time.

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Thanks Friend Bear. No i don't have sepatrons (haven't even heard of them yet). I'll try fixing the solid boosters more carefully this time.

They are micro-solid boosters that are, if I remember, in the engine category when building.

The other strategy if the boosters are just too often hitting your main engine once decoupled because they take so long to drift past is to place the boosters lower, about 1/3 of the booster will be below the main thruster in the middle, and putting the decoupler slightly above the boosters center of mass. This will cause the top of the booster, once decoupled, to push away from the rocket more free and clear from the rest. But it is important you place the booster lower because if you don't, the effect also is that the bottom of the booster will spin inward and hit the center.

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Sepratrons are kind of unnecessary. Just spin the rocket up around its central axis before detaching the boosters and they'll be flung away by centrifugal force.

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I've spent most of the day launching and actually getting up there. No problems with fuel any more. It's the tricky bit of getting into orbit. There's something about my burn timing and I feel I'm so close but the thing just won't connect. Apoasis is good and I'm making pretty good circles around Kerbin. It's just something in that countdown and burn. Just for fun, here's what I did to poor old Bill Kernan in the last one. (I have no idea how!)

fsV6ddF Link is http://imgur.com/fsV6ddF By the way, I am uploading screens to Imgur and inserting the URL but that's what happens.

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JackBush,

Are you executing the circularization in map mode? That helps a lot.

I maintain the time to Ap at least 45 seconds until I'm faster than 2km/sec. After that I shut down and coast up to it. Once I get within 15 seconds of Ap, I throttle as necessary to keep Ap 5 seconds ahead until circularized. You can use radial in or out to control where the Ap sits as well as the throttle.

There's a more realistic method where radial aiming is used instead of throttling, but we'll save that for another day.

Glad to see you coming along!

-Slashy

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Gold rule : make it simple and light

If you pass your Apoapris, you failed. You dobn't have enough TWR so you can't increase you max altitude (Apoapsis).

As many said : use Kerbal Engineer Redux (KER) mod. With that you'll get reading about your rocket TWR and you delta-V (dV).

There are many vehicles that go to space. the easiest way to do it is to pack a TWR of 1.4 or 1.5 and have 3200m/s dV (3500 with largely safe margin)

Make your first rocket simple. Use 2 stack stages

- One with fins at the bottom which have to set your Apoapsis to 80km

- One with a small engine to circularize.

An easier way to do it is to create a SSTO rocket. They are easy to fly, but are a more expensive. Only one stage

A for flying, there are many videos that explain the proper 1.0 way to go to orbit. I like to turn 5° at 50m/s to aim crossing theb 45° between 8 and 10km. and then flat my trajectory around 25 to 30km (what even my rocket akllow me to do). Don't discard fins before 35km or you may flip.

If you rocket flip : increase fins size (don't hesitate to use wing parts)

If you can't turn : reduce your wing size or add more control surfaces.

And another simple rule : you always want to point your ship are prograde, not more that 5° from it.

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If you pass your Apoapris, you failed. You dobn't have enough TWR so you can't increase you max altitude (Apoapsis).

Not categorically true. There are 2 elements to reaching orbit, being high enough and being circular enough. Apoapsis is only and indicator of the former, speed is the best indicator of the latter.

If you pass you apoapsis while still accelerating rapidly in a horizontal direction, you may find your apoapsis suddenly 'overtaking' you to be in front of you again. This may not be optimal, but if you make it to space who cares?

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If you pass you apoapsis while still accelerating rapidly in a horizontal direction, you may find your apoapsis suddenly 'overtaking' you to be in front of you again. This may not be optimal, but if you make it to space who cares?

Hey it worked for the Shuttle....

What Warzouz said is true in most cases but not all. In fact I had what you describe happen to me recently... passed the ap only to have it over take me again a short time later.

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Made it! YF7lzJ6

http://imgur.com/YF7lzJ6

As you can see it's not completely circular. I got the impression from one video that you can adjust the orbit to make it circular--or anything you want, I guess. If so, how?

And finally, thanks for all your help and advice. Now I have to go practice doing it some more.

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Congrats! Nothing quite like getting into orbit for the first time, most people think it is simple but it really does take a LOT to get up there. In general to change the height of a part of an orbit, you want to fire pro/retrograde at the opposite part of the orbit. So to raise your PE, you want to fire prograde when your ship is at AP. If you want to lower your PE , you would fire retrograde at AP. When your PE and AP start to swap places in the orbit, you're pretty much circular.

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Congrats! Nothing quite like getting into orbit for the first time, most people think it is simple but it really does take a LOT to get up there. In general to change the height of a part of an orbit, you want to fire pro/retrograde at the opposite part of the orbit. So to raise your PE, you want to fire prograde when your ship is at AP. If you want to lower your PE , you would fire retrograde at AP. When your PE and AP start to swap places in the orbit, you're pretty much circular.

Alternatively, a radial burn can adjust both simultaneously. If you're mid- way between Pe and Ap, a radial burn will adjust both at the same time. If you're climbing from Pe to Ap, a radial in burn (pointing straight down) will raise your Pe and lower your Ap at the same time. If you're descending from Ap to Pe, a radial- out (pointing straight up) will equalize them.

I use a mix of throttle and radial along with my prograde burn to make nice circular orbits from launch.

Best,

-Slashy

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Well, when you have to burn radial to go to LKO, you waste a LOT of fuel. Usually, we don't pack fuel for those kind of burn. If you go to LKO with a regular 3200/3300 m/s you pretty much fail when you reach APO to low. You don't have fuel to burn again to change your trajectory. You might burn up fuel that should have been used for circularizing.

Any time I lift off (on Kerbin or on other body) and cross my apoapsis (usually by going to flat too soon with insufficient TWR) no burn could recover my trajectory (with the fuel I usually carry). F9 has always been my only salvation.

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