Need help pilotting SSTO's

[XOIIO]

Alright, had a thread a long time ago asking if an SSTO that I made could get to orbit, it would seem I can make ones that can get into orbit, in theory, but I just SUCK ASS at pilotting them. Generally they are on the heavier side and can't take off until the runway drops off, but I just can't get em into orbit even if I can reach 1.2km/s+.

I generally try to build them so that I could use turbojets to actually get my apoapsis where I want, and then an LV-N to circularize and have loads of Delta left over to pop about.

I just can't get the damn things into orbit, I have a few times before but never reliably :/

the current one I have is intended for launching ion sats to explore out to a decent range, it weighs about 20 tonnes, but flies quite nicely and is balanced properly, I just can't get the right damn ascent path :/

[Cmdr. Arn1e]

Would probably be best to ask here: http://forum.kerbalspaceprogram.com/forums/15-Gameplay-Questions-and-Tutorials

[Monger]

Chances are: if you can't get it reliably to orbit, then your ship design needs improvement. I guess your engine design is just barely strong enough to make it into orbit. You need a little buffer. Piloting an SSTO should not be that difficult.

[XOIIO]

Posting this here as suggested:

Alright, had a thread a long time ago asking if an SSTO that I made could get to orbit, it would seem I can make ones that can get into orbit, in theory, but I just SUCK ASS at pilotting them. Generally they are on the heavier side and can't take off until the runway drops off, but I just can't get em into orbit even if I can reach 1.2km/s+.

I generally try to build them so that I could use turbojets to actually get my apoapsis where I want, and then an LV-N to circularize and have loads of Delta left over to pop about.

I just can't get the damn things into orbit, I have a few times before but never reliably :/

the current one I have is intended for launching ion sats to explore out to a decent range, it weighs about 20 tonnes, but flies quite nicely and is balanced properly, I just can't get the right damn ascent path :/

[magnemoe]

First advice use the rapiers at least in the beginning, optionally turbojets and 48-7S, also make small SSTO first.

But main wheels just back of center of mass, it makes it easy to lift your nose, you might want some extra wheels on the wings back and outward increased stablity then landing and to protect the engines then pulling up.

Flying: climb fast up and level out at 20 km, start building up speed, this depend a lot of your plane more intakes let you go higher at lower speeds.

[katateochi]

Start off making a really small SSTO, you can get into orbit on 1 full FL-T400 Fuel Tank and 1 FL-T200 Fuel Tank (with all the oxidizer emptied out).

I'm actually making a set of v light weight SSTO's but they're not quite done yet, but this was posted on KerbalX and is s a good example of how small an SSTO can be.

In terms of flight, this works for small/medium SSTO's. You need to vary climb rates according to weight and thrust;

Take off and pitch up to 45 degrees. climb until you AP reaches 10, pitch to 20. continue to climb until you AP reaches 18, pitch to 10. You may need to adjust this pitch, but you want to be maintaining a climbing rate of about 150-200m/s.

If you go for a small design, (my fav recipe is 2 advanced jet engines and an LV-t30, 2 intakes and the above fuel tanks, sprinkle with wings and season to taste), then you'll be pushing over 1800 ms before you reach a height of 30km. There is a sweet spot which you can hit that enables you to keep running on air breathing engines well up to 35km and greatly reduces your need to bring bipropellent along. To hit this sweetspot you need to have got up to around 1800ms before you reach 27-28km. If you hit it then the engines won't flame out, they will make stuttering noises and slowly fade down 'till they look like dying embers. You don't have to hit it, not all SSTO's can, but if you can hit it you'll hardly need any rocket fuel on the way up.

When the engine do cut out, pull up to 25-30 degrees and switch to rockets. raise ap to ~70-80, pitch to 5, raise to 120 (the atmo will then pull you back down to near 100km).

If you've got the right balance you'll be able to raise your AP to above 70km on airbreathing engines alone. then you just need a quick blast to lift the Ap a little more and then to circularize, but you should have ended up in such a wide sub orbit that circulation will only take ~100-200ms.

[Red Iron Crown]

I'm relatively new to spaceplanes (I'm assuming that's what you mean by "SSTO") and they are definitely a different beast than launching a rocket. The launch profile is very different.

A 20t plane should have at least two air-breathing engines, whether Rapiers or turbojets (it can work with one but is much more challenging). Your takeoff issues may be caused by several things, but the likeliest is that your rear landing gear are too far back. Try moving them so they're just aft of the center of mass, this will make pivoting for takeoff before the end of the runway easier. If that doesn't work, try adding more pitch control surfaces or reaction wheels to give more pitch authority.

Once airborne, climb as quickly as is reasonable to 15km, then start leveling off and building speed. The bulk of the acceleration should happen between 20km and 35km altitude, and you should be able to reach to 2km/s or more. If you get your apoapsis out of the atmosphere, ride your jets until they starve for air, then close the intakes and coast to apoapsis and circularize with the rocket engine. If your Ap isn't out of atmo yet, turn on the rocket and point up at about 45 degrees to raise the Ap before circularizing.

I haven't had great results with LV-Ns as the rocket engines for spaceplanes, it's a heavy lump of an engine that requires a fair bit of compromise to incorporate in a design. An aerospike, LV-909, or some 48-7Ss is often better for designs meant to stay in Kerbin's SoI (including the Mun and Minmus). I would stick to the lighter engines until you're more comfortable with getting planes to orbit.

All of the above assumes stock aerodynamics, I don't have enough experience with planes in NEAR or FAR to give good advice.

Edited October 19, 2014 by Red Iron Crown
Typo

[ZedNova]

Make sure your rear landing gear is close to the center of mass, without making it tip backwards with no pressure.

[AmpsterMan]

Going to move this to a more appropriate forum.

[Brainlord Mesomorph]

you might want to look at this thread:

http://forum.kerbalspaceprogram.com/threads/96920-Help-with-a-space-plane-design-how-much-air-do-i-need-How-to-read-the-Air-Intake/page3

one of the last posts is step by step to orbit.

[Vanamonde]

Duplicate threads merged.

[Pecan]

Alright, had a thread a long time ago asking if an SSTO that I made could get to orbit, it would seem I can make ones that can get into orbit, in theory, but I just SUCK ASS at pilotting them. Generally they are on the heavier side and can't take off until the runway drops off, but I just can't get em into orbit even if I can reach 1.2km/s+.

I generally try to build them so that I could use turbojets to actually get my apoapsis where I want, and then an LV-N to circularize and have loads of Delta left over to pop about.

I just can't get the damn things into orbit, I have a few times before but never reliably :/

the current one I have is intended for launching ion sats to explore out to a decent range, it weighs about 20 tonnes, but flies quite nicely and is balanced properly, I just can't get the right damn ascent path :/

SSTO rockets need to have approximately 300m/s more dV than a disposable one so they have enough fuel to de-orbit and land. Otherwise, a couple of drogue 'chutes and fly a normal ascent path. The cost of SSTO rockets is carrying all that extra fuel and used engines there and back so, yes, using jets instead of rockets is more fuel-efficient (but has higher part-count and construction costs). Using jets, follow a normal spaceplane ascent instead of a rocket ascent - make orbital speed (~2km/s) almost horizontal before 30km altitude.

Ditch the LV-N; it's too heavy to take to orbit and no use once you've got there, since you're just coming back. 48-7Ss are the best, since they're so light.

[Laie]

Alright, had a thread a long time ago asking if an SSTO that I made could get to orbit, it would seem I can make ones that can get into orbit, in theory, but I just SUCK ASS at pilotting them. Generally they are on the heavier side and can't take off until the runway drops off, but I just can't get em into orbit even if I can reach 1.2km/s+.

For everything we tell you, you still need to make your own experiences. Really, build a small plane (really small, basically a fighter plane) and try that first. My first spaceplane was huge, and it took me weeks to figure things out -- mostly because every attempt took like 20-30minutes, and there's only so many hours in a day.

Learning it with small planes isn't really easier, but it's a lot faster.

[Kilmeister]

Generally they are on the heavier side and can't take off until the runway drops off

You most likely just need to move your rear landing gear nearer your CoM. A common misconception is that inability to liftoff is due to weight or lack of lift, when it's usually about balance.

[XOIIO]

You most likely just need to move your rear landing gear nearer your CoM. A common misconception is that inability to liftoff is due to weight or lack of lift, when it's usually about balance.

That helped a lot.

Here are images of my craft, I just can't get much into the last layer of atmosphere reliably, I've tried all sorts of things, gradually changing angle of attack, going to the point where my engines are getting low and flattening out, nothing really helps. Highest AP I got once was 48km.

Found the mechjeb setting to show vertical speed so that should help, I'll instead try and focus on that, it's just a pain because I get up to a decent speed between those two atmosphere layers, get reentry effects, and then I end up losing speed after gaining it for a bit and even going totally horizontal I keep losing altitude :/

I also plan on one with a Clamp-o-tron and crew cabin for taking people up to stations/ bases on the mun and minimus, and one with two large cargo bays to launch long range ion or LV-N probes, however I need to learn how to fly these damn things first. I keep getting close, but can't make it.

Edited October 20, 2014 by XOIIO

[XOIIO]

oh yeah craft file: https://www.dropbox.com/s/zcow1y0ujz9uguh/Spaceplane%201.craft?dl=0

[Red Iron Crown]

Great looking plane.

That's an awful lot of intakes, you should be able to run your jets to over 50km with all that air. Since you're using mechjeb, I'd suggest you use the "Manage Air Intakes" and "Prevent Engine Flameout" tools in the Utilities panel, they make it a bit easier to manage. The prevent flameout function is pretty conservative, you can eke out a bit more acceleration if you manage the throttle manually.

Your plane also doesn't have much wing area for its mass, I suspect that you have to maintain a relatively high angle of attack to keep climbing or maintain altitude.

[XOIIO]

Great looking plane.

That's an awful lot of intakes, you should be able to run your jets to over 50km with all that air. Since you're using mechjeb, I'd suggest you use the "Manage Air Intakes" and "Prevent Engine Flameout" tools in the Utilities panel, they make it a bit easier to manage. The prevent flameout function is pretty conservative, you can eke out a bit more acceleration if you manage the throttle manually.

Your plane also doesn't have much wing area for its mass, I suspect that you have to maintain a relatively high angle of attack to keep climbing or maintain altitude.

Thanks, once it's out of testing (pretty much right away) I'm going to call it the SSSSTO (Super .... Single Stage To Orbit)

I've found I can run the jets at around 32km if I get lucky, maybe higher when I get better at horizontal speed, but I'm not sure.

I already use Prevent engine flameout, only tried manage air intakes a couple times, seemed to make it harder to get up high enough, but it shouldn't really. Probably just my crap piloting lol. You are correct about the angle of attack, I tried adding more wing surface but without radically changing the design I can't without moving the lift area before the COM.

Anyways, made it to space!

Just the once so far, but it was pretty good. I got a slingshot off the moon to send my probe out of kerbins SOI (though I should have done it after, no big issue though, it was only a 41 second burn out of the ~45 minutes on that probe), changed the plane's orbit, came down over a nice land mass, unfortunately on the other side of the world, but made a nice gliding touchdown in the highland fields. I could have saved some fuel, but used the last in my LV-N to pick up a tad more horizontal speed as I wasn't sure if I was coming down to fast or not.

This thing costs 101k to launch, unfortunately you only get back 33k for recovery, probably because of the distance, I am going to upgrade the management thing for that, but it seems a tad shallow. I'll aim closer to KSP next time lol. Either way, great way to get probes out of kerbin's SOI, haven't checked compared to a fairly basic probe launcher but I bet it's cheaper too. If not at least it's more stylish.

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[capi3101]

Looks like I arrived late; congrats on getting everything worked out.

I'll go ahead and point you to DocMoriarty's guide; it has some good general pointers on how to build spaceplanes. It pretty much incorporates all the advice folks have already given you on this thread. I know that my big issue with spaceplanes has been design (knowing how many engines I need, how many wings I need, etc.) and this guide has helped me build craft that don't immediately fly into the drink. Only known changes so far for 0.25 - wheels have mass now, so ignore that bit, and the Small Control Surface has been replaced with Elevon 4.

[XOIIO]

Tried making a vertical one too for the heck off it, it's also challenging to get into orbit, probably because I went with a three jet engine design instead of the regular two for looks, adding a decent bit more weight, but it looks really cool! (So I'll have to figure it out). Mechjeb can easily get it to 1500M/s with a modified rocket ascent profile, it's just raising the apoapsis enough after that.

[Red Iron Crown]

If you're using MechJeb for a rocket style ascent, I've found it works well to edit the ascent profile and set the turn end altitude to 20km and adjust the turn end angle to something that will allow a slow climb (some experimentation with different values may be required).