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Frostiken

I've been playing this game for like two years now...

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However if you have the CoM in the middle of the craft and the control surfaces far behind and in front, then it does not need to be so nose heavy.

Correct. The best designs put the CoM and CoL very close together, with control surfaces at the very front (canards) and very back. For instance, here's my very successful spaceplane design, the Sleazy Weasel. Note the canard embedded in the leading edge of the wing (just forward of the intakes) and the flap assembly extending from the back of the plane (surrounding the engines):

7NkvmUU.jpg

It's not nose-heavy at all, and it flies perfectly. It's a bit on the heavy side for a small spaceplane (22 tons), due to the extra fuel it carries, but I've got a variant that can get two ion-powered mapping probes into orbit. It's also designed to be able to land on its tail, so I've landed it on Mun and Minmus in the past.

To the OP, don't underestimate the need for precision landings. In the stock game there's no need to pick a specific landing point on most bodies, so rockets work just fine, but go install the Kethane mod and you'll start to see why precision matters; when you need to land on a specific spot on a planet to get the resource you need to get home, you'll see that standard "brick" landers just don't work so well any more on anything with an atmosphere. Once the new resource system comes in, this'll be part of the core game, too, so don't just dismiss it as a mod-specific concern. The bigger problem is that there are too few bodies with atmospheres, and stock jet engines don't work on all but two of them; the aerodynamics you learn on jet planes can be used for rocket-powered planes (great for Duna), but it's not quite the same.

That being said, there's Laythe. Try doing a land-and-return from Laythe using a non-aerodynamic rocket; its gravity is almost as much as Kerbin's, and the atmospheric drag means it takes a lot of delta-V to ascend. If you're lucky enough to actually land on a landmass, you'll likely be on a very inclined surface, which'll make takeoff problematic. My first Laythe landing was with a Kethane-powered Grand Tour lander, and Laythe was the second-toughest ascent (behind Eve, of course). Whereas, spaceplanes are EASY to travel to Laythe; all you need is a way of refueling them at Jool. Once we get the resource system, this'll be a much bigger deal, since you'll want an SSTO lander that can repeatedly land on Laythe and ascend, since you won't be able to strap on new staged boosters each time.

The bottom line is, at present spaceplanes aren't very useful, outside of missions involving only Kerbin and Laythe. They're fun, but there's not much they can do that a vertically launched design can't do much better. The reason we use SSTO spaceplanes as an indicator of skill is that they're just far more challenging than a normal rocket, because you have to manage so many more variables during both design AND flight. For a normal rocket you don't have to worry about the CoM-vs-CoL-vs-CoT positioning (since symmetry handles that for you), or the total amount of lift you have, or the exact positions of the flaps and RCS, or the number of intakes open at any given time and their position, and so on. You don't need multiple engine sets, and you use ASAS to lock in a specific orientation and heading (instead of the "soft" avionics that spaceplanes generally use). And while rockets need to be careful balancing speed versus altitude, for spaceplanes it's much more complex given the need for intake air. With rockets you can always go bigger, adding another stage to the bottom of your design to get more delta-V, but with spaceplanes smaller is often better; you start having to really examine the weights of specific parts, and whether they're absolutely necessary, especially if you're attempting an SSTO design.

So getting an SSTO spaceplane of your own design to orbit is prized, because it's an indicator that you have a deeper understanding of how the game works than you'd ever see in standard rocket use. That's why it's worth sticking with, even if you're having horrible issues; eventually you WILL get it, and when you do, you'll really feel like you've mastered the game. Just don't use the stock planes, because they suck; download one of the many well-tested player designs that have been posted on these forums, and then tweak away. My own design, above, was originally based on eXclipse's excellent "Allium" spaceplane, although almost nothing is left of the original.

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... and I still can't do anything useful with spaceplanes.

Take the completely stock, ships-with-the-game Aeris 4A. It has a rocket engine and everything. And RCS, and a coupler! If anything is designed to get into space, it's this. And it ships with the game, so it should be pretty simple to get into space.

Don't worry, you're not alone. I'm here since 0.10 and haven't successfully done a roundtrip using spaceplanes, so I've sticked to rockets instead. But it's everyone's personal preference.

Summary of possible outcomes of my Spaceplane attempts (taken from another thread):

Load → SPONTANEOUS DISASSEMBLY

Load → Spacebar →RUNWAY EXPLOSION

Load → Spacebar → Runway roll → VEERS OFF RUNWAY

Load → Spacebar → Runway roll → Runway end → FAILS TO TAKE OFF

Load → Spacebar → Runway roll → Runway end → Take-off! → EARLY FLAMEOUT

Load → Spacebar → Runway roll → Runway end → Take-off! → Transition altitude → NOT ENOUGH THRUST

Load → Spacebar → Runway roll → Runway end → Take-off! → Transition altitude → Sufficient thrust → NOT ENOUGH FUEL TO ORBIT

Load → Spacebar → Runway roll → Runway end → Take-off! → Transition altitude → Sufficient thrust → REACHED ORBIT! → NOT ENOUGH FUEL TO DE-ORBIT

Load → Spacebar → Runway roll → Runway end → Take-off! → Transition altitude → Sufficient thrust → REACHED ORBIT! → De-orbit successful → STALL SPIN DURING RE-ENTRY

Load → Spacebar → Runway roll → Runway end → Take-off! → Transition altitude → Sufficient thrust → REACHED ORBIT! → De-orbit successful → Good re-entry → MESSED LANDING

The nearest I've got was #9. Almost became a KSP pro (by my definitions anyway) :D

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It is extremely difficult to get a truly working SSTO space plane. Of the probably 30-40 designs I've toyed with (stock parts, no MJ or anything), I've had only about 5 or 6 of those designs that will reliably take off, reach orbit, de-orbit, and land back on the runway in a single, unrefueled flight. Once I get them to that point, I'll start strapping them with science equipment, maybe lander legs, etc., and use them mostly as scouts. I just like having the ability to make powered landings, use them as crew transfer vehicles, and other similar missions. They are not easy at all, but MAN will you feel accomplished once you've got it figured out!

On a side note, Captain Kalawang's summary of possible outcomes looks pretty much identical to my prototyping process on new designs, with very few exceptions!

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I Always put my COM and COL right on each other, yet my planes all seem to spin out as soon as they hit significant atmospheric drag on reentry. I always end up with small spacecraft designs because larger ones end up too nose heavy for takeoff even with tons of canards and even in a couple of cases groups of sepratrons on the nose for lift assist. Also several of my designs like to somersault as soon as I initiate the takeoff roll. At any rate, every single spaceplane launch is always a gamble even to just get off the runway safely.

Edited by wolfedg

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Ive struggled with spaceplanes for a long time, and only this weekend actually managed to get one into orbit. Of course, It still cant land without refueling in lko, and I cant figure out how to land it horizontally, so it has to do a powered landing onto its tail. Even with the aerodynamics being weird I think it's fun to build one just to build it and see if it'll work. . . watching the sun crest over Kerbin as I finish my burn to establish orbit, all the while watching my fuel with fingers crossed, is an enthralling experience that I think defines the game.

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Space planes specifically are really hard to build right now for a few reasons.

1. You must have a nose heavy space plane throughout all of its operations. Not just a little nose heavy either. A lot nose heavy. That makes getting them off the runway a nightmare. I tend to use 24-77s at the front to rotate the ship for lift off. One could use sepratrons as JATO's I guess.

What? Almost all of my space-planes have the CoL on the back edge of sphere of CoM. That's not very nose heavy. Plus, I don't think I've ever seen a good, efficient space-plane that doesn't leave the runway before the end.

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FAR gave me more flyable spaceplanes in exchange for unpredictably uncontrollable rockets. After the third time my originally stable rocket began doing backflips for no reason every time I moved from the velocity vector I dumped that mod like a bad habit.

It saddens me when people give up on FAR so easily. I'm not a realism junkie, I understand that games should balance gameplay and realism, but FAR makes flight so much more intuitive and realistic I cannot understand why people *wouldn't* want to use it. If everything you've learned about orbital mechanics or aerodynamics came from playing KSP (I myself have learned quite a lot), just realize it is not 100% analogous to real life. You need to stay on the velocity vector or "bad things happen". You can't just strap rockets around an already un-aerodynamic payload and hope it gets into space. Take the opportunity to learn more about how rockets really work, and then FAR will make so much more sense.

Anyway, regarding the stock spaceplanes, I couldn't for the life of me get it to work either. It is terrible. So I made my own design, the Spearrow (click for album):

After the first successful test takeoff and landing he was happy to be alive :)

lV20EL6.jpg

This plane gave me a lot of firsts. First SSTO plane (although I've never made a staged spaceplane to this day), first time docking without mechjeb (I forgot to put it on because it flies so nicely in the atmosphere without it), first time rotating crew of the space station, first time landing back at the runway from orbit (although I overshot my entry by some distance and had to fly back, but I had plenty of fuel :) ) and probably a few others I've already forgotten. It was definitely one of the most challenging things I've done in KSP, but after the first time the rest don't seem so bad.

Some tips, dunno if they'll be helpful or not, but might as well:

1.) carry as little jet fuel as possible. It becomes dead weight without oxidizer up in space.

2.) using trim (alt w/s/x) is essential, especially in the upper atmosphere. Once you get up to 20km, you might just want to adjust pitch only with trim.

3.) lightweight rocket engines with plenty of thrust are what I've found to be best to achieve orbit.

4.) the center of mass should be slightly forward of the center of lift for best stability.

5.) the transition is crucial. use RCS before switching, and try to turn off jets at last moment.

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What? Almost all of my space-planes have the CoL on the back edge of sphere of CoM. That's not very nose heavy. Plus, I don't think I've ever seen a good, efficient space-plane that doesn't leave the runway before the end.

I think if you edited my plane "Kestrel", you could make a Space-plane that would take off before the end of the runway.

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Don't worry, you're not alone. I'm here since 0.10 and haven't successfully done a roundtrip using spaceplanes, so I've sticked to rockets instead. But it's everyone's personal preference.

Summary of possible outcomes of my Spaceplane attempts (taken from another thread):

The nearest I've got was #9. Almost became a KSP pro (by my definitions anyway) :D

This feels like Deja Vu...your attempts profile looks almost exactly like mine! :D

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As hard as spaceplanes are to make and successfully get to lko Im more of a do the impossible kind of guy so after my first sucessfull spaceplane flight i decided to built a spaceplane with nervas on it and a full kethane package umm..... pretty freakin hard actually but i actually did it and flew it ( after lko refuel ) to laythe with 3000 dv left over.

thats one hell of a challenge. It only took me 30+ hours of design and fail.

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I find the stock SSTO's a bit lacking.

Who uses the stock spacecraft types anyway? Half the fun of the game is in the design.

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This is by far my favorite SSTO, and it's V/STOL too!!

http://forum.kerbalspaceprogram.com/showthread.php/24734-Amphibious-VTOLSSTO-%28Image-heavy%29?highlight=amphibious+ssto

Has darn near perfect balance, but if you're slick with the trim, or at least ASAS, it'll keep a heading no problem. I've flown this bugger to orbit and back quite a few times. Sticking a landing on a specific point is a bit challenging with the stock jet engines, but I've embedded optional aerospikes in the vertical engines for drastic last-minute bursts of thrust if needed.

<3

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It saddens me when people give up on FAR so easily. I'm not a realism junkie, I understand that games should balance gameplay and realism, but FAR makes flight so much more intuitive and realistic I cannot understand why people *wouldn't* want to use it.

There's nothing realistic about rocket backflips.

You need to stay on the velocity vector or "bad things happen". You can't just strap rockets around an already un-aerodynamic payload and hope it gets into space. Take the opportunity to learn more about how rockets really work, and then FAR will make so much more sense.

We have exactly zero stock options and very few mod options for streamlining a payload. Second, I don't think in the history of spaceflight there's been a problem of a massive rocket dumping out 3Gs of force randomly deciding to pitch end-over-end.

Edited by Frostiken

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I Always put my COM and COL right on each other, yet my planes all seem to spin out as soon as they hit significant atmospheric drag on reentry.

This is most likely because of your intakes. The drag an intake generates is an inverse function of airflow, so coming back into an atmosphere they'll be creating a LOT of drag initially; if your intakes are up at the front of your plane, well ahead of your center of mass, they'll cause a spin as the atmosphere thickens. This is why you should assign most of your intakes to an action group; keep them closed until you're above ~10km on ascent, close them when you go to orbit, and leave them closed all the way down during landing. This'll greatly reduce your drag, which'll really help with the spinouts. Alternately, place your intakes behind your center of mass so that the drag actually helps keep you straight. Besides, you don't need much airflow on descent, since you won't be running your jets at full power; for control reasons I usually turn on the jet engines at the minimum amount and leave them there while landing.

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There's nothing realistic about rocket backflips.

See 00:56

Rocket flips *could* happen all the time, were it not for the Range Safety Officer, who will detonate that sucker the moment its telemetry goes the slightest bit cuckoo. While we're not exactly concerned about it in the game at present, if rockets were allowed to flip out as frequently in real life, there'd be a heck of a lot of deaths from rockets veering badly off course and plowing into a nearby neighborhood.

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See 00:56

Rocket flips *could* happen all the time, were it not for the Range Safety Officer, who will detonate that sucker the moment its telemetry goes the slightest bit cuckoo. While we're not exactly concerned about it in the game at present, if rockets were allowed to flip out as frequently in real life, there'd be a heck of a lot of deaths from rockets veering badly off course and plowing into a nearby neighborhood.

Is it bad that I laughed when the rockets exploded? Or I realized that my rockets have done each and every one of those crashes and more?

By the way, the Delta-4 crash was caused by the engineers not installing an ASAS unit :P

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Is it bad that I laughed when the rockets exploded? Or I realized that my rockets have done each and every one of those crashes and more?

By the way, the Delta-4 crash was caused by the engineers not installing an ASAS unit :P

Now we know why Jeb is crazy: he's from NASA!! He's seen it all, therefore, Badass flag=1

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We have exactly zero stock options and very few mod options for streamlining a payload. Second, I don't think in the history of spaceflight there's been a problem of a massive rocket dumping out 3Gs of force randomly deciding to pitch end-over-end.

Since others have already pulled up a few clips on youtube, I'll just point out that the word "randomly" doesn't belong there. You may not understand why the rocket decided to pitch end-over-end, but there is always a reason. If you install far, you'd better install some fairings as well, or you'll be limited to aerodynamic payloads. You also need to adjust your ascent. A non aerodynamic payload risks shooting yourself in the foot while using FAR, and the traditional "straight up to 10k, pitch to 45 degrees" under the same conditions is basically carefully aiming at your foot before pulling the trigger. The less aerodynamic the top end of your craft is, the tighter you want to hold to the prograde during launch. Even with aerodynamic craft, I don't pitch more than 10 degrees or so off of prograde if I've got FAR installed.

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I once got a spaceplane into orbit w/o cheats, w/o mods. However it was huge and needed to be refuled after it barley makes orbit.

But my other attempts can be seen here

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Well it has taken me many months of my own experiments and tending the K Prize thread to see how everyone else did it, but I think I have finally distilled the essential factors for making an SSTO space plane so that when a new version comes out I can slap together a space plane from scratch and make orbit and return to the runway first try. As others have said the key is placing center of lift relative to center of mass.

Spaceplane Design Factors 101.

1. Always engineer the center of lift slightly behind the center of mass, but make sure you have sufficient leverage on ailerons to overcome the tendency to nose dive this creates, ie make sure the ailerons are well back from the center of mass. Canards can help lift off but become a liability if the center of mass shifts rearwards during flight, ie towards the engines as the fuel is used up, this makes the craft flip on reentry and landing.

2. Have fore and aft central tanks placing extra tanks parallel to the center of mass (spread out tanks sideways) and not longitudinally to keep center of mass in roughly the same place as the fuel runs out. Use the section with fore and aft tanks to move fuel if necessary to balance out weight distribution. Always try to keep the center of mass in front of the center of lift because otherwise it will try to fly backwards.

3. Place the rear undercarriage only on items which have not had any angular adjustment when placing relative to the main fuselage (and are connected by items which have likewise not been adjusted as the wheels get twisted and attachment points get skewed by adjustments). Place them so the middle of the undercarriage aligns slightly behind the center of mass (when viewed from the side) and adjust as required. This way you get minimal twist on take off and you can pitch the craft nose up balanced on the rear undercarriage to change angle of attack easily. If the wheels are too far back then you cannot lift the nose until you overshoot the end of the runway. If the craft is too long the engine will hit the ground & btw if it wont take off at 100m/s at maximum tilt you need more wings! If the craft falls over backwards after landing the center of mass moved backwards past the wheels.

4. I always use ASAS to help because the flight model can be so unstable. Though ASAS is not working right and is sometimes unusable and can make craft flap like birds and fall out of the sky when engaged. When this happens sometimes reducing the amount of control surface can help so adjustments are not too exaggerated.

5. Use a single aeroengine design to avoid flame out disaster spins. Maximise the number of "ram" air intakes per engine, at least 2:1. Reduce throttle at high altitude to allow the aeroengine to continue to operate with reduced air as long as possible. Optimise speed and climb at high altitude carefully to maximise air intake.

FYI hope that helps.

Edited by boolybooly

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