Why are rockets so easy and planes so hard?!

[-DDD-]

Seriously, you can't compare chinese fireworks with a modern rocket... It's like to say that they master aerodynamic cause they can build kites.

Edited August 24, 2016 by -DDD-
typo

[MaxwellsDemon]

I think the controls we use matter a lot, as well.  Launching rockets with a keyboard is relatively simple in KSP:  punch a button to fire the engines, go straight up, then gradually push a button to turn east at a certain rate.

Flying a plane on a keyboard is a lot harder-- it's part of the reason why serious flight sim addicts have not only joysticks, but not infrequently steering yokes, pedals, throttle levers, and sometimes basically an entire cockpit.

[Whirligig Girl]

3 minutes ago, -DDD- said:

Seriously, you can't compare chinese fireworks with a modern rocket... It's like to say that they master aerodynamic cause they can buld kites.

You can in KSP though. The thing that makes real rocket science hard and expensive are the turbopumps, the ignition limits, the aerodynamic stress, the fuel selection... I could go on. But in KSP, much of this is simplified. The rockets you build in KSP are more like throttleable, stagable chinese fireworks than they are modern rockets in terms of the forces that you actually have to go simulate.

The reason we didn't have liquid fueled rockets before the early-mid 20th century is because we didn't have suitable fuels, and more importantly we didn't have turbopumps. Turbopumps are immensely complicated machines to build. With all of the plumbing involved in a rocket engine simplified to a single part, we can definitely compare Kerbal rockets to much simpler solid fueled rockets like Estes or Fireworks. Spaceplane engines have a similar amount of oversimplification, but there's a lot more forces that need to balance here, so it ends up seeming harder.

The real world reason we had planes before space rockets was that propellers and simple jet engines are much much easier to build than a large turbopump-driven bipropellant rocket. You can build a solid fueled rocket in an afternoon. You can build a simple jet engine in a week. You can't feasibly build your own turbopump driven rocket engine.

[swjr-swis]

1 minute ago, -DDD- said:

Seriously, you can't compare chinese fireworks with a modern rocket... It's like to say that they master aerodynamic cause they can buld kites.

Yes, in fact you can say that. The first successful planes looked very much like oversized kites with a seat for a reason. They used the same type of structure and even materials, because these were the forms and materials that had up to that point been proven to take to the sky and even generate enough 'pull' to lift people from the ground.

https://en.wikipedia.org/wiki/Lawrence_Hargrave

https://en.wikipedia.org/wiki/Samuel_Franklin_Cody

 

[-DDD-]

2 minutes ago, GregroxMun said:

You can in KSP though. The thing that makes real rocket science hard and expensive are the turbopumps, the ignition limits, the aerodynamic stress, the fuel selection... I could go on. But in KSP, much of this is simplified. The rockets you build in KSP are more like throttleable, stagable chinese fireworks than they are modern rockets in terms of the forces that you actually have to go simulate.

The reason we didn't have liquid fueled rockets before the early-mid 20th century is because we didn't have suitable fuels, and more importantly we didn't have turbopumps. Turbopumps are immensely complicated machines to build. With all of the plumbing involved in a rocket engine simplified to a single part, we can definitely compare Kerbal rockets to much simpler solid fueled rockets like Estes or Fireworks. Spaceplane engines have a similar amount of oversimplification, but there's a lot more forces that need to balance here, so it ends up seeming harder.

The real world reason we had planes before space rockets was that propellers and simple jet engines are much much easier to build than a large turbopump-driven bipropellant rocket. You can build a solid fueled rocket in an afternoon. You can build a simple jet engine in a week. You can't feasibly build your own turbopump driven rocket engine.

this is exactly what i think, i was answerng to those that said that even in RL a rocket i simplier that a plane because in ksp is so...

[Sharpy]

16 minutes ago, -DDD- said:

Seriously, you can't compare chinese fireworks with a modern rocket... It's like to say that they master aerodynamic cause they can buld kites.

But seriously, solid fuel rockets were used by military in 16th century or so.

The true difficulty began with liquid fuel engines, and the first "serious" rocket that crossed Karman line - V2

And yet again, that whole difficulty is in construction of the engine. The flight rules are exactly the same as for solid fuel rockets.

As for kites - untethered ones? If you can build a kite that can fly well without the string drawn to the ground, you did master aerodynamics.

DaVinci made the plans for the first glider, but it was never realized. First working gliders are the 2nd half of 19th century.

10 minutes ago, GregroxMun said:

The reason we didn't have liquid fueled rockets before the early-mid 20th century is because we didn't have suitable fuels, and more importantly we didn't have turbopumps. Turbopumps are immensely complicated machines to build.

Saturn V didn't have turbopumps. It was pressure fed (at least the first stages, don't know about the rest).

But the stability of combustion is a huge thing. Having the fuel and oxidizer portioned ideally, continuously, and regardless of stuff like acceleration, turning around etc. Turbopumps are means to that end, pressure fed systems are somewhat but not much simpler.

[Red Iron Crown]

31 minutes ago, -DDD- said:

Seriously, you can't compare chinese fireworks with a modern rocket... It's like to say that they master aerodynamic cause they can build kites.

Similarly, you can't compare rockets meant to go to space with atmospheric airplanes. Atmospheric rockets are simpler than atmospheric planes. Space-capable rockets are simpler than space-capable planes. Ergo, rockets are simpler than planes. 

[-DDD-]

7 minutes ago, Sharpy said:

But seriously, solid fuel rockets were used by military in 16th century or so.

The rocket used in military in 16th century have in common with a moder SRB only the name.

14 minutes ago, Sharpy said:

And yet again, that whole difficulty is in construction of the engine. The flight rules are exactly the same as for solid fuel rockets.

This is partially correct, but read something about the Saturn V development process (only because is one fo the most documentated) and you will discover a new world. Only for example the pogo oscillation problem wasn't a joke.

18 minutes ago, Sharpy said:

As for kites - untethered ones? If you can build a kite that can fly well without the string drawn to the ground, you did master aerodynamics.

DaVinci made the plans for the first glider, but it was never realized. First working gliders are the 2nd half of 19th century.

If someone discovered something first, it doesn't mean that the thing is easier.

[Whirligig Girl]

14 minutes ago, Sharpy said:

Saturn V didn't have turbopumps. It was pressure fed (at least the first stages, don't know about the rest).

That is absolutely 100% grade A Bul--err... Falsehood.

The engine which drove the Saturn V was a massive construction with a fuel flow rate of 671.4 gallons of propellant a second. You're not gonna do that with a pressure fed engine. What do you think all of the plumbing on this engine is for? Decoration?

The Apollo CSM and LM engines were, if I'm not mistaken, pressure-fed. But not the F-1 or J-2 engines on the Saturn V.

[Sharpy]

1 minute ago, -DDD- said:

The rocket used in military in 16th century have in common with a moder SRB only the name.

[citation needed[

Fuel-oxidizer mix, payload (explosive), combustion chamber, nozzle, aerodynamic stabilization. Anything more important than that that they didn't have that modern SRBs do?

 

Quote

This is partially correct, but read something about the Saturn V development process (only because is one fo the most documentated) and you will discover a new world. Only for example the pogo oscillation problem wasn't a joke.

One more problem that is not simulated in KSP. One more problem with LF engines. A serious difficulty of real-life rocketry not copied into KSP.

Quote

If someone discovered something first, it doesn't mean that the thing is easier.

But it means it was being developed and perfected for a longer time.

Physics that is fundamental for orbital mechanics was Newton, Kepler and Lagrange. When did the first serious works on aerodynamics begin?

[-DDD-]

8 minutes ago, Red Iron Crown said:

Similarly, you can't compare rockets meant to go to space with atmospheric airplanes. Atmospheric rockets are simpler than atmospheric planes. Space-capable rockets are simpler than space-capable planes. Ergo, rockets are simpler than planes. 

I'm trying to say it in the  most kindly manner that i can but this is a very poor syllogism. First you can make syllogism only if there is a perfect dicotomy in the elements (tertium non datur law); second we have the in in accord to the definition of plane and rocket; i'm consideering only rockets that have an pratical purpose, so launcher and not "hobby-graded".

[Red Iron Crown]

1 minute ago, -DDD- said:

I'm trying to say it in the  most kindly manner that i can but this is a very poor syllogism. First you can make syllogism only if there is a perfect dicotomy in the elements (tertium non datur law); second we have the in in accord to the definition of plane and rocket; i'm consideering only rockets that have an pratical purpose, so launcher and not "hobby-graded".

There are other uses for rockets than launching to space, indeed far more rockets have been built to stay in atmosphere than have been built to go to space.

[Sharpy]

I have a feeling you're not quite seeing the point I'm arguing.

Spaceflight is vastly harder than aviation.

But the elements of spaceflight present in KSP are easier in real life, than elements of aviation present in KSP are in real life.

Orbital mechanics, at level present in KSP (two-body systems; multibody simulated by patched conics) and resource management planning (ISp, TWR, fuel ratio) is much easier than aerodynamics as simulated by KSP (lift, torques, moving center of mass, drag changing with speed). Also aerodynamics of rockets is quite simple comparing to aerodynamics of airplanes, even in real life.

The highest difficulty in rocketry is in the engines - and KSP gives you these 'for free', without real-life problems of most real rocket engines.

That's the reason why rockets are easier IN KSP. You really don't have to argue they are harder in real life. I know they are. It's just that the difficulty varies between various aspects and KSP cherry-picked the easy ones.

 

[-DDD-]

@Sharpy, i won't quote you for not clip to much the thread but:

1 Fuel-oxider mix are not from 16th century, the first cobustion chamber and nozzle that work was the de Laval one used for the first time by goddard in 1914, modern SRB have more subsystem, you can read the SCOM for an overview of the STS ones.

2 I think we was talking about RL, if not sorry.

3 Newton works wasn't intended to understand the orbital mechanic, but the law that order the  universe. But i think we was talking about enginering, not physic, the physic is universal, enginering no.

8 minutes ago, Red Iron Crown said:

There are other uses for rockets than launching to space, indeed far more rockets have been built to stay in atmosphere than have been built to go to space.

Yes but IMHO compare a sounding rocket to a orbitale rocket (in term of complessity) is like comparing a glider to a F-22 in fact of complessity.

[Sharpy]

@-DDD-

1)

- Saltpeter and charcoal. Oxidizer and fuel. With sulfur for a catalyst and secondary fuel added.

- There's about 15% efficiency drop between de Laval nozzle and a simple straight cone.

- a combustion chamber in SRBs is still just a hollow pipe with a hole on one end.

- don't quote STS SRBs on me. Try an unguided Hydra missile instead. It is STILL a modern solid fuel rocket.

2)

- Rocketry IRL can be simple too. Water bottle rockets, to counter the paper airplanes. Small amateur rockets and fireworks to counter RC model airplanes. And so on. The things scale roughly in parallel until you begin reaching the edges of the atmosphere and begin spaceflight. Then, rocket complexity, ummm, skyrockets.

3)

- Newton developed calculus and laws of gravity.

- Kepler observed motions of celestial bodies and described them mathematically.

- Lagrange converted Newtonian's equations into Lagrangian mechanics, which is a great tool to analyze orbital motion. (deriving anything but circular orbits directly from Newton's mechanics gets absolutely hopelessly convoluted).

At that point, one could say orbital mechanics was completely understood. But it was still pretty useless except for astronomy and its derived applications (timekeeping through observing Io eclipsing Jupiter?)

Until Tsiolkovski calculated that LF rocket can get us to the orbit.

 

[Red Iron Crown]

12 minutes ago, -DDD- said:

Yes but IMHO compare a sounding rocket to a orbitale rocket (in term of complessity) is like comparing a glider to a F-22 in fact of complessity.

Not talking about sounding rockets. Guided atmospheric rockets are so simple and useful that they are mass-produced.

You're taking the most difficult type of rocket and comparing it to a much easier type of plane. I stand by my earlier statement, "Atmospheric rockets are simpler than atmospheric planes. Space-capable rockets are simpler than space-capable planes." 

[Xavven]

IRL planes have parachutes during testing, especially when testing how the plane performs in spins. Here's a picture of a hilarious rigging on the F-35 during spin-testing. Fun fact... the F-35 has so much control during stalls and spins that they decided to remove the chute for the remainder of their test flights.

 

[magnemoe]

42 minutes ago, Red Iron Crown said:

There are other uses for rockets than launching to space, indeed far more rockets have been built to stay in atmosphere than have been built to go to space.

Many magnitudes more as in all firework and all military rocket outside of larger ballistic ones stays in the atmosphere. 

16 minutes ago, Red Iron Crown said:

Not talking about sounding rockets. Guided atmospheric rockets are so simple and useful that they are mass-produced.

You're taking the most difficult type of rocket and comparing it to a much easier type of plane. I stand by my earlier statement, "Atmospheric rockets are simpler than atmospheric planes. Space-capable rockets are simpler than space-capable planes." 

Yes, orbital rockets are hard, orbital spaceplanes are way harder so they don't exist in real life. as we don't have good enough engines even if we had it would be hard. 
atmospheric rockets outside of firework is all sort of military rockets, the hard thing about them is control and accuracy not the rocket itself. 

[-DDD-]

8 minutes ago, Sharpy said:

Saltpeter and charcoal. Oxidizer and fuel. With sulfur for a catalyst and secondary fuel added.

Wiki say that first idea of a bipropellant is of goddar, maybe i haven't searched well.

11 minutes ago, Sharpy said:

don't quote STS SRBs on me. Try an unguided Hydra missile instead. It is STILL a modern solid fuel rocket.

A Hydra is more like a missile than a rocket.

14 minutes ago, Sharpy said:

- Rocketry IRL can be simple too. Water bottle rockets, to counter the paper airplanes. Small amateur rockets and fireworks to counter RC model airplanes. And so on. The things scale roughly in parallel until you begin reaching the edges of the atmosphere and begin spaceflight. Then, rocket complexity, ummm, skyrockets.

A paper plane is easier than a water bottle rocket, but this is just imho; but there are a many type of rocket and many type of plane... we can't compare all.

 

17 minutes ago, Sharpy said:

Newton developed calculus and laws of gravity.

- Kepler observed motions of celestial bodies and described them mathematically.

- Lagrange converted Newtonian's equations into Lagrangian mechanics, which is a great tool to analyze orbital motion. (deriving anything but circular orbits directly from Newton's mechanics gets absolutely hopelessly convoluted).

At that point, one could say orbital mechanics was completely understood. But it was still pretty useless except for astronomy and its derived applications (timekeeping through observing Io eclipsing Jupiter?)

Sorry but i can't understand the point of this, the gravity is used also in aerodynamic, is not orbital mechanic-strictly related, and  Tsiolkovski's formula don't apply only on LF fueled engine.

[Xavven]

9 minutes ago, -DDD- said:

A Hydra is more like a missile than a rocket.

It depends on what hydra rocket you're referring to. Unguided hydra rockets are rockets. There is a precision variant called APKWS that is laser guided and could be described as a missile, but in this case is usually referred to as a "guided rocket". Confusing? Yes. Arbitrary? Yes.

[Sharpy]

8 minutes ago, -DDD- said:

A Hydra is more like a missile than a rocket.

The gravity is used also in aerodynamic, is not orbital mechanic-strictly related, and  Tsiolkovski's formula don't apply only on LF fueled engine.

What's the difference between a missile and a rocket, actually?

In aerodynamics, gravity is a constant 9.8m/s^2. Not F=G M1 M2/r^2.

Tsiolkovski's formula lay the groundwork for developing space-capable rocket propulsion. But he was the one that used it to calculate that actually reaching space is possible. And gave LF engine as an example.

[Diche Bach]

1 hour ago, MaxwellsDemon said:

I think the controls we use matter a lot, as well.  Launching rockets with a keyboard is relatively simple in KSP:  punch a button to fire the engines, go straight up, then gradually push a button to turn east at a certain rate.

Flying a plane on a keyboard is a lot harder-- it's part of the reason why serious flight sim addicts have not only joysticks, but not infrequently steering yokes, pedals, throttle levers, and sometimes basically an entire cockpit.

I've found that the joystick is a mixed bag. My work/play station is a lazy boy with a large screen at my feet (when the leg rest is raised). Wireless keyboard and mouse on plywood lapboard.

So where do I put the joystick in this arrangement (and it applies to a more traditional computer work station sitting at a desk chair with screen in front of face keyboard on desk and mouse to side: where to put the joystick?).

Yes, you can put it over on one side . . . I have a piece of plexiglass strapped to my lapboard so that the suction cups of the Saitek will stick to it (somewhat). But this is less than ideal. The joystick should be in your crotch, else if it were a "steering wheel" design: in front of you.

One day, when I'm rich and famous, I'm going to invest in a flight sim build that essentially mimics a real cockpit, but short of that, I find using keyboard for control of in flight sims actually BETTER than using a joystick slapped on the same surface as my keyboard mouse.

Certainly cheaper, less risky, and less hassle than going for an actual flight license . . .

Edited August 24, 2016 by Diche Bach
youtube

[-DDD-]

We are very OT so this is my last reply on the argument but:

Usually a rocket is anything propulsed by an endothermic reaction engine, a missile is a bullets with a internal engine.

and really 9,8 is equal to F=G*M*m/d^2, is only a particular case. When was calculated the athmospheric entry of the MER's they don't have used 9,8.

[magnemoe]

Now making an basic plane in KSP is not hard but a bit more complex than an rocket as you need to balance center of mass and lift and have control surfaces with more care than the four fins on an rocket. landing gear is also an issue. Takeoff and flying is also not very hard if balanced. Landing is harder it require pilot skills, same does landing on bodies with decent gravity and no atmosphere. 
Landing in uneven terrain is hard also in real world even more so. I say they can be compared to making an fast or large rover. 

[Maltman]

3 hours ago, -DDD- said:

Rocket-science easy? Try RO for have a taste, real rocket science is one of the most difficult disciplne of engineering, problem that you don't consider in KSP are very relevant in real life, like aerodynamic stress, or optimizazion... do your rockets arrive in orbit with less than 5% of fuel with a continuous burn? I'm not saying that your desing skills are bad, but in RL rocket science isn't so easy.

 

 

 

I played RO with RPO. Still felt that getting into orbit was not very different than stock. Just needed more boom.

Landing a plane on the other hand ohh nooo. But to be fair 99% of plane woes are those darn tier one landing gear and at least RPO let's you start off with decent gear. Getting supersonic was no problem but then I killed Jeb landing in the desserts of Kazakhstan.