New path to orbit at least for me, need some help with it.

[Moonfrog]

Ok, I'll start by saying how I normally get to orbit. I tend to go straight up, then 45 then tilt it down maybe. When it reaches 70,000 km at Apoaphis I tend to start, then glide then finish the orbit. I think this is a pretty standard way most people do it.

Been playing around with planes, looking up videos and saw someone do something different. It was with an SSTO plane, but instead of shooting up into space he kinda pushed himself over the edge of the planet. If that makes sense.

So I built a rocket, which has couple of wings on it in its middle stage the one after the solid boosters but before the small engine push into orbit happens. The new path I'm trying to take into orbit like what I saw in that guys video, focuses more on pushing horizontal than going up. Reason why I want to do this, is to figure out if this is a better way of getting to orbit. Or at least an excuse to build different types of rockets with funny wings may not need wings, but so far its helped keep the direction pointing upwards while my rocket points more sideways then it usually does.

Main goal is that Instead of going up in a path like a steep hill. It will be more like a gradual ascent that pushes across the earth then into space out the other end. Guess it would look more like a heightened bridge built on two arches. This should let me arrive in space at 70km as close to my orbit as possible. Not sure how this would change the rocket designs or what u could do with this method, but I need to figure out how to do it first so I can experiment more.

Its actually a lot like how I take off from the mun, I go up a bit to avoid mountains, then go almost straight horizontal to avoid fighting gravity. I kinda want to do something like that on kerbin.

[Taki117]

The issue with doing a spaceplane ascent (Where you go more horizontal than vertical) is that spaceplanes have wings and airbreathing engines. Rockets are...well...rockets, meaning that they are designed to go vertical untul they perform a gravity turn. What will end up happening if you try to do a spaceplane ascent with a rocket is that you will be in the atmosphere far longer than you need to be, resulting in a higher dV to orbit.

If I am understanding your ascent profile correctly you are going straight up to 10km, then pitching to 45 degrees on a heading of 090. If this is the case, that's more or less correct, though after the initial pitchover you should gradually continue to drop your nose, and keep your apoapsis about 1m ahead of your current position.

[Master Tao]

Moonfrog,

You're right, burning horizontally is more efficient in many cases like your example of taking off from the Mun. The biggest issue you run into with stock KSP is the excessive atmospheric drag. You need to get your rocket high enough that the benefits of burning horizontally (Oberth effect and little/no gravity drag) overcome the atmospheric drag losses. Your rocket needs to be fairly high to do that in stock (50+ km?), but much lower if you use Stock Drag Fix, NEAR, or FAR. If you want to experiment with mods, those would let you try that ascent profile more easily.

[micha]

Actually a "proper" gravity turn you start by pitching a couple of degrees shortly after liftoff, and then either literally let gravity pull the nose of the rocket gradually down as you ascend (you need a nicely balanced rocket, also turn off rcs & sas, also might only work with NEAR/FAR), or you very gradually keep pitching over as you ascend so that by 10km you're at 45degrees or so. Once your apoapsis is a minute or so ahead, and you're out of the thickest part of the atmosphere, you can pitch over more rapidly.

As for flying a rocket like a spaceplane, the biggest difference is that a spaceplane accelarates very slowly, using highly efficient air-breathing engines. A rocket does not have that luxury, carrying all it's oxidizer with it. So you should try to get out of the atmosphere (and the drag it causes) as quickly as possible (while staying at or below terminal velocity).

[Wanderfound]

You don't have to have a spaceplane for a spaceplane-style ascent to work, but you do need lifting surfaces and air breathing engines. Try it with conventional rockets and you'll waste all your fuel fighting air resistance; the fuel efficiency of air-breathers makes it worth it, but rockets are too thirsty.

If you are going spaceplane style, the standard method is:

1) Climb as fast as possible to the low-friction air above 20,000m.

2) Level off and build speed while you climb to the edge of the usable atmosphere. By the time you hit 30,000m you want a climb rate of about 10m/s and a horizontal speed of Mach 4 or better. The idea is to extract as much speed and altitude as possible from the jets before lighting the rockets.

3) When the jets start to choke, pull the nose up to 45 and light the fireworks. Do it right and you'll have your apoapsis over 70,000m with less than a minute of oxidising burn.

For a more rocket-suitable "sideways" ascent (no wings or jets required), do a normal gravity turn to start with. But instead of shutting down and coasting to apoapsis when it hits 70,000m, instead keep the rockets lit and pull the nose down to the horizon (or just below the horizon, depending on how fast you're going). You need to constantly monitor your pitch and fine-tune it; too low and you'll plunge back into the thick low altitude air, too high and your apoapsis will get wastefully excessive.

If you have one of the mods that gives you basic flight data (e.g. Mechjeb), what you want to do is watch your "time to apoapsis" figure. If the number is going down, your nose is too low; if it's going up, your nose is too high. Let it drop to start with, but try to stabilise it so that your apoapsis stays about 10 seconds in front of you. You'll need to gradually lower the nose as you accelerate to do this.

Do this right and you can set your apoapsis and periapsis to 70,000m in a single burn; no circularising required. If you were in vacuum this would be the most efficient way to launch; on Kerbin it's a bit more complicated due to the effect of atmospheric resistance. But so long as you spend most of your burn time above 50,000m you should burn less fuel than a traditional style "10,000m, 45 degrees, coast and circularise" ascent.

As they're vulnerable to atmospheric drag, both of these approaches work much better in FAR/NEAR than they do in stock aero's soupy atmosphere.

Edited August 2, 2014 by Wanderfound

[GoSlash27]

My standard ascent profile for lifters:

-Vertical ascent at 1.4-2G acceleration to 7km altitude.

-gradual pitchover and throttle reduction to hit 70* pitch, 1-1.4G acceleration at 15km altitude

-continue pitchover and throttle reduction to hit 45* pitch, .7-1.0G acceleration at 25km altitude

-continue pitchover and throttle reduction to hit 30* pitch, .5-.7G acceleration at 35km altitude

-At "orbit" indication, switch to orbit map. continue acceleration at .5G and pitch as required to maintain desired apoapsis.

At this point, I can either

a) pitch as necessary to maintain to maintain apoapsis while raising periapsis until circularized or

cut throttle until 30 sec from apoapsis, then throttle level as necessary to maintain 10 sec to apoapsis until circularized.

a is more realistic while b is easier. Either profile is *very* efficient.

Best,

-Slashy

[Pecan]

If you want to carry wings around you should be staying in the atmosphere to use them.

If you want to stay in the atmosphere longer than necessary use jets for efficiency.

If you want to use jets build horizontal velocity before altitude.

[Sirrobert]

The reason space planes go like that is to ensure you gain the most use/speed out of the airbreathing engines, before switching to rocket engines.

This is because air breathing engines are way more efficient than rocket engines.

So what a spaceplane does, is build up as much speed as possible with air breathing engines (they need to stay in the atmosphere for that. So they go horizontal). And when they have enough, they point up to leave the atmosphere, and than use rocket engines to circulize