SSTO Spaceplanes, or how I learned to stop worrying and love airhogging.

[Jarin]

So, I think I'm gonna give up my long-held prejudice against clipping. As I've started playing with more complicated builds, I've realized that it's just another tool in the box. It's not like it changes the mass you have to lift. The one place I've held out is with intakes, but I think it's time to see what life on the dark side is like.

To my understanding... at its base, "airhogging" is just the act of having lots of intakes per jet engine, yes? Can anybody give me a rundown of the specific methods involved? Or perhaps correct my understanding of the process itself.

[Traches]

Airhogging just lets you run your jet engines much higher than before, which lets you get much closer to orbital velocities on jets, which lets you use almost no fuel getting to orbit when you switch to rockets. You don't have to part clip to do it. The rule of thumb is 4 intakes per jet engine, and the ram air intakes are the only ones worth using.

If you're big on planes, install FAR. It does a good job of killing the advantage of airhogging-- your thrust drops off above mach 5 (which is realistic.)

[SuperBigD60]

Air hogging can still help there, though

The higher you are when you max out your speed, the better off you are, and that has a great deal to do with your intake air.

[Col_Jessep]

For an easy start you want to go to the VAB not the SPH. Allow part clipping and put 4,6,8... RAM intakes on a small octagonal strut and save them as subassembly. Now go to the SPH and add them without symmetry! If you use symmetry to add the glitched intakes you might run into trouble like your craft not saving correctly or the game crashing. 8 intakes per engine is a good number imo. You can even stack the subassembly if needed. Enjoy!

[Zephram Kerman]

In my opinion: clipping yes, airhogging no!

Clipping allows us to build things that should work, but don't because of software limitations. Airhogging allows us to put jets in orbit without trying very hard. But I must admit, I'm no saint when it comes to airhogging. I'll sometimes break my "one intake, one engine" rule and add one or two more intakes, but never more than a 2:1 ratio. (More than that is cheating in my rulebook. But fortunately, there are as many rulebooks as there are KSP players!)

Anyway, the technique relies using the cubic octagonal strut to radially attach another intake (or more). You can also use the front of the airplane tail if it is mounted radially. Or, just use any leftover front-facing node. You can even hide intakes within the vessel, thereby "cheating" with no one the wiser. Mwahahaha! Oops, I shouldn't have told you about that...

[DaveofDefeat]

Step 1: Place those tiny cubic girders everywhere

Step 2: Spam Ram air intakes, 2 per girder

Step 3:???

Step 4: Profit

Then to go to the darkest darkside, use mechjeb to control Intakes and throttle.

[Hodo]

Air Hogging is running ridiculous numbers of intakes per engine. Great examples of them can be found in the Spacecraft exchange forums. Some of the SSTOs designed can be found running something like 20:1 Intake to jet ratio, which is just flat out stupid and would not work in the real world or even in the Hello Kitty-verse.

My rule of thumb is 3:1 intake to jet ratio. As it is HARD, REAL hard to find a real aircraft that has more than that ratio.

As Traches said, FAR does solve the airhogging problem. Not only does it make running jets past Mach 5 impossible, it also makes aircraft near impossible to fly with that amount of drag with the numbers of intakes most airhogs run.

Some of my fastest aircraft have had surprisingly few intakes using the actual speed to boost the airflow into the engines, you know like a REAL plane.

I am fine with part clipping, as long as you dont exploit the debug menu to do it. Sometimes it leads to a better aesthetic look and feel to the craft. I find most of the SSTOs created running the typical airhog setups absolutely horrible. There is one that I find great looks but that is because he was going for a particular look and that is Cruzans "BSG Viper". But that craft does not work at all in FAR.

The only way some of these stock air hog monstrosities even come close to flying in FAR is with the use of Mechjeb. And if you can't fly the craft yourself, because it is that badly designed, then you have no business letting a computer fly it.

[Col_Jessep]

I am fine with part clipping, as long as you dont exploit the debug menu to do it. Sometimes it leads to a better aesthetic look and feel to the craft.

But with the debug menu you can put fuel ducts INSIDE your plane. Looks much nicer. I'm not a fan of visible plumbing on planes. You should try it.

[Shrike42]

Air Hogging is running ridiculous numbers of intakes per engine. Great examples of them can be found in the Spacecraft exchange forums. Some of the SSTOs designed can be found running something like 20:1 Intake to jet ratio, which is just flat out stupid and would not work in the real world or even in the Hello Kitty-verse.

My rule of thumb is 3:1 intake to jet ratio. As it is HARD, REAL hard to find a real aircraft that has more than that ratio.

As Traches said, FAR does solve the airhogging problem. Not only does it make running jets past Mach 5 impossible, it also makes aircraft near impossible to fly with that amount of drag with the numbers of intakes most airhogs run.

Some of my fastest aircraft have had surprisingly few intakes using the actual speed to boost the airflow into the engines, you know like a REAL plane.

[...]

The only way some of these stock air hog monstrosities even come close to flying in FAR is with the use of Mechjeb. And if you can't fly the craft yourself, because it is that badly designed, then you have no business letting a computer fly it.

Worth remembering that KSP, even with FAR, is not reality, and using your aesthetic sense to determine what would or wouldn't fly based purely on the simplified simulations within KSP's code doesn't mean they'd work worth a darn in reality. Engine efficiency, intakes and compression are all very different because of how tiny Kerbin is vs. Earth. Typical jet airliners cruise at 32-38,000 feet (11.5 km), with one intake per engine. That's the point at which stock KSP jets just start to get 'good', but then the intake air starts dropping off dramatically for everything but ram scoops. The U-2 spy plane routinely operated at 21 km, which is about what you can squeeze out of the turbojet with a single intake. Anything beyond that, and you're entering the realm of fiction.

Heck, the U-2's maximum velocity was about 223 m/s, which is a slow walk compared to what a turbojet can do (because we don't have friction that'll rip the craft apart if we go 10 knots higher than 223 m/s. Kerbal material science is quite good, despite finding all these parts by the side of the road).

Basically, stock KSP is already going well into the world of fiction. Perhaps FAR's variant atmosphere setup brings it more in line with reality (and gives a greater challenge), but you're still sending little green men to the mun and back in about seven days.

Not saying you're wrong, I'm not aesthetically pleased by my air-hogging designs (though they still look like planes). But the ability to push a fictional craft to its theoretical limits in a fictional environment is 'fun' to me. It's a 'what if...' scenario where I can just play within the artificially imposed ruleset and just see what I can do. I'm an engineer and do a lot of my work in simulation programs, but I'd never try to use KSP's simulated environment as a proof-of-concept for an aircraft.

Edited November 21, 2013 by Shrike42

[numerobis]

Shrike42: keep in mind also that the Kerbin atmosphere has a scale height of 5km, rather than about 8.5km for Earth. Pressure at 10km on Kerbin is like pressure at 17km on Earth. And we routinely fly our turbofans up there, no problem.

[allmhuran]

I'd never try to use KSP's simulated environment as a proof-of-concept for an aircraft.

That's a nice way of saying it.

KSP is not an "earth physics simulator", and it is not intended to be. It's a game that has basic physical laws in common with reality, but presents an entirely different universe with different constraints. The fun of the game is not dependent on those constraints being anything like what they would be on earth, for the same reason that, say, Tribes being a fun game is not at all dependent on people having personal jetpacks that work equally well as the few "real" personal jetpacks we have here on earth.

If you *want* to make KSP physics a little closer to real world physics, that's fine, go ahead and install whatever mods you like. But statements like:

"...you know like a REAL plane"

"FAR solves the airhogging problem"

"something like 20:1 Intake to jet ratio, which is just flat out stupid and would not work in the real world or even in the Hello Kitty-verse"

... are non sequiturs. You might think of it like this: Vanilla KSP is a maze in a book of mazes. It has some particular solutions that work, and others that don't. But you can't just draw a line from "start" straight to "finish" and claim that since the real world is actually 3D, not 2D, your solution is a valid one. Something like FAR is just a different maze in the book, requiring a different solution.

Edited November 22, 2013 by allmhuran

[Traches]

That's a nice way of saying it.

KSP is not an "earth physics simulator", and it is not intended to be. It's a game that has basic physical laws in common with reality, but presents an entirely different universe with different constraints. The fun of the game is not dependent on those constraints being anything like what they would be on earth, for the same reason that, say, Tribes being a fun game is not at all dependent on people having personal jetpacks that work equally well as the few "real" personal jetpacks we have here on earth.

If you *want* to make KSP physics a little closer to real world physics, that's fine, go ahead and install whatever mods you like. But statements like:

"...you know like a REAL plane"

"FAR solves the airhogging problem"

"something like 20:1 Intake to jet ratio, which is just flat out stupid and would not work in the real world or even in the Hello Kitty-verse"

... are non sequiturs. You might think of it like this: Vanilla KSP is a maze in a book of mazes. It has some particular solutions that work, and others that don't. But you can't just draw a line from "start" straight to "finish" and claim that since the real world is actually 3D, not 2D, your solution is a valid one. Something like FAR is just a different maze in the book, requiring a different solution.

You make good points, but the drag model is specifically a placeholder. It was never intended to be accurate, or a part of the final game. It was just easy to plan, code, and balance.

[Hodo]

That's a nice way of saying it.

KSP is not an "earth physics simulator", and it is not intended to be. It's a game that has basic physical laws in common with reality, but presents an entirely different universe with different constraints. The fun of the game is not dependent on those constraints being anything like what they would be on earth, for the same reason that, say, Tribes being a fun game is not at all dependent on people having personal jetpacks that work equally well as the few "real" personal jetpacks we have here on earth.

If you *want* to make KSP physics a little closer to real world physics, that's fine, go ahead and install whatever mods you like. But statements like:

"...you know like a REAL plane"

"FAR solves the airhogging problem"

"something like 20:1 Intake to jet ratio, which is just flat out stupid and would not work in the real world or even in the Hello Kitty-verse"

... are non sequiturs. You might think of it like this: Vanilla KSP is a maze in a book of mazes. It has some particular solutions that work, and others that don't. But you can't just draw a line from "start" straight to "finish" and claim that since the real world is actually 3D, not 2D, your solution is a valid one. Something like FAR is just a different maze in the book, requiring a different solution.

That's nice, I said my reasons and I am sticking to them, like them or not. That is the beauty of KSP, I can play the game how I want to, and you can play the way you want to. I don't bash peoples designs that are hog monstrosities, or completely impractical asparagus blocks of tanks and rockets. I often find some of these Dr. Zeus contraptions to be quite entertaining, more so when I download some of them and place them in my sandbox just to see how they explode. But again my way is not the right way, and your way isn't either. Not going to debate reality or game world physics with people on the forums for a game that isn't even complete yet, simple as that.

[allmhuran]

You make good points, but the drag model is specifically a placeholder. It was never intended to be accurate, or a part of the final game. It was just easy to plan, code, and balance.

Sure. Eventually the current drag model maze will be replaced with some other drag model maze, which will require different solutions.

[allmhuran]

I don't bash peoples designs that are hog monstrosities, or completely impractical asparagus blocks of tanks and rockets

I would say that calling them stupid or impractical counts as "bashing" them. And it would be inappropriate to do so, since in the vanilla KSP maze they are neither stupid nor impractical but are, in fact, entirely correct and functional solutions.

[Teirusu]

As far as Part Clipping goes, I always enable it. I do not consider part clipping a 'cheat' for two main reasons.

A) You can already clip parts fairly easily without it being enabled: Stick an engine on the BZ-52 radial plate, pick up the plate and rotate it around. Tada! Engine clipped into the tank. Works for anything stuck to a surface mountable piece. The game doesn't bother to check for collision with any of the parts attached to the piece that your moving. Just the root part. All enabling part clipping does in the debug menu is disable checking for collision with the root part that your moving around. Moreover, enabling part clipping tends to fix those issues where your trying to attach something in symmetry.. but it won't do it, even though nothing is apparently 'colliding'.

NASA and aero-space companies don't have to deal with 'part clipping'. They just engineer the stuff to fit together how they need too. They don't deal with pre-manufactured parts that they can't modify to suit their needs. Heck, when have you ever seen a rocket with batteries stuck to the sides?

In anycase, as for air intakes, I'll typically do anything from 1 to 4 intakes per engine, depending on the plane and if it 'looks' okay doing so. I won't just stack them. For instance, I'll use the stack coupler plates to attach more then 1 intake in front of the engine, like this:

Where it stimulates an extra-wide air intake, or a high-bypass turbo-fan engine.

[Hodo]

I would say that calling them stupid or impractical counts as "bashing" them. And it would be inappropriate to do so, since in the vanilla KSP maze they are neither stupid nor impractical but are, in fact, entirely correct and functional solutions.

Not sure what you mean by "maze", so a bit confused there. When I read the word maze I think of a maze, or labyrinth, not something that has to do with game code.

But in response to your statement.

I, unlike others, do not post in someone thread about someones craft that they may have spent hours working on or is their first working SSTO, plane, rocket or whatever and say, "meh, thats impractical.." or anything to that affect. I may say, "I like the design, but unfortunately it may not work for me." Which is me saying, good job on your craft, but not my taste. And to me thats no different than me saying, I am a Ford man not a Holden fan.

If someone asks me privately what do I think about a certain craft they have made, I will tell them privately. But I will not come out and bash someones work publicly, I may offer advice on how to improve a faulty design or tweak something to get a bit more performance out of it. But I will not just tell them its junk start over, or here download one of MY craft.

I have been building SSTOs for a while now in KSP, both stock and mod. When it comes down to the brass tacks, I couldnt stand the stock KSP lack of aerodynamic code, and actually fell in love with the FAR and DRE mod. Now they are the first two mods I install when ever I have to reinstall KSP. I wanted a harder, closer to real life flight code. Something where I could build a plane that looks like it could exist in the real world, and it behave like a real aircraft, not like some wondermagicalmysterymachine.

Now there are a few of my SSTO space planes that are just down right fugly, but they weren't designed with looks in mind. Others are quite good looking but perform like shaved bricks. But vast majority of my space plane SSTOs perform quite well and look pretty decent. Even my stock maching bird challenge mach 6 in FAR craft is based on a real life aircraft, the Mig-21. But that is because I like the look of that craft. But being a military history nut, I knew the Mig-21 was designed not with looks in mind but performance and specific speeds in mind, when it came out it was one of the fastest most nimble aircraft in the air. So my craft followed that design theory. And it performed well within specs and exceeded my goals and yet it can do better with a few more fine tuning runs and tweaks.

It runs 2 ram intakes, with a small nose cone in the center, and it topped out at 2170m/s at a low altitude of 24km. But is it the best looking plane I have ever made, no. Is it the fastest in atmosphere jet I have made, no. Is it a airhog, nope.... What is it? It is mine and I am proud of it. And that is all that matters to me. And to be honest that's all that should matter to anyone who builds their stuff in this game and posts pictures of it.

[allmhuran]

Sorry, by "maze" I was just continuing on with my analogy from the previous post, probably should have been clearer about that.