Spaceplanes Are Too Hard

[Caelib]

I have about 100 hours of gameplay time into KSP and I love it. Now, let me say that I like challenging games ... but the Spaceplanes in KSP are too difficult. I have watched numerous tutorials and spent no less than 30 hours in the spaceplane hanger designing different craft, but I have yet to be able to get one into an actual orbit.

Personally, I have been able to fly one all the way up to 70,000 meters and get so, so, so, so, so close to an orbit ... but I just cannot come up with a magic combination of lift/balance/etc to carry enough fuel to get into orbit (let alone rendezvous).

Basically, this aspect of the game is too hard -- I've spent almost a week of gameplay time trying to a spaceplane into orbit but that's the extent of my patience so I'm just giving up entirely.

[Schweehog]

so I'm just giving up entirely.

Spaceplanes at the moment are completely useless. The point of spaceplanes in real life is that they cost less, but in KSP there isn't a cost. Also, KSP doesn't have proper aerodynamics, so nothing really flies correctly. Don't give up hope though, they are bound to change both of those major issues.

[Van Disaster]

I use Ferram's aero mod and have been for months so I can't remember what the default physics are like, but it sounds basically like you a) have too much weight ( possibly from adding more fuel ) and you're burning rocket fuel too early or from too low a speed. Wings are lightweight and at high altitude the drag is neglegible, adding more might help you gain a bit more speed before lighting the fires. If you're using nuclear rocket engines - please do, aerospikes are not a great solution for Kerbin at least - then you more or less want a 1:1 relationship with jets, unless you're just using two jets because one would result in symmetry problems.

Add more air intakes - air is a fuel, you can assume it's ducted around the airframe so it's not entirely beyond the bounds of probability ( although it'd be nice if someone added reductions in airflow if the intake was at a ludicrous angle to the engines ), that way you'll get more altitude out of the jets.

Lastly, jets can feed off rocket tanks so you don't absolutely need seperate jet fuel tanks.

[Procyon]

I agree its difficult, I have not been able to make one yet also, I will eventually though. When is do it will be cause for much calibration and a party .

On a serious note, This is one of the main reasons I like this game so much, the sense of accomplishment when you finally pull off something really difficult.

[hapaxLegomina]

Start with a plane you know can reach orbit to work out the nuances of your ascent profile. With >100 hours, I'm sure you've got the theory down, but the confidence boost from actually doing it once or twice can make all the difference.

And, boy, I can't wait until spaceplanes are actually worth it. I would love to fly regular tanker/personnel change missions. I want spaceplane missions to be commonplace and boring, you know?

[Monger]

My impression is, that the whole aircraft parts are not properly balanced with the spaceship parts. This is not THAT surprising, after all the whole aeronautics thing was based on a KSP mod (I think, C7 brought it into the official KSP release).

I think one of the main issues is, that even the biggest wings create a laughable amount of lift. Since the atmosphere of KSP is a little denser than on earth, you should be able to maintain flight with very low speeds. A jumbo jet on earth starts with ca. 200 km/h , so about 55 m/s. Also, that you need so many air intakes until your jet drives reach their speed limit is ridiculous.

Besides this, there is no proper cockpit view, and the ASAS module doesn't unterstand how to properly foils to stabilize a ship.

So, yeah, building space planes is possible, but currently MUCH harder than it should be.

[Tanya Sapien]

I actually recommend Romafarer's Lazor System if you're having problems with keeping your planes stable, it automatically dampens input and prevents oversteering to help keep planes more balanced. Also, the advice others posted before is right and I fully agree with it, more intakes, and a nuclear engine which you only trigger when you're at the very lip of space and burning your last drops of jet fuel. Don't worry about the low thrust of the nuclear engine when trying to achieve orbit, if you take a look at your context menus while at high speeds and altitudes, you'll actually see a drastic reduction in how much power your jet engines are providing, so the crossover to the rocket when your engines flame-out might actually come with a noticeable amount of acceleration.

[EndlessWaves]

but I just cannot come up with a magic combination of lift/balance/etc to carry enough fuel to get into orbit (let alone rendezvous).

Single stage planes are only a subset, and one of the harder ones. If you've only been trying those it's no surprise you're having some difficulties.

Build it more like a rocket with staging so you can drop empty fuel tanks and whatnot.

Can you provide an example of some of your craft? It's not particularly difficult once you get your head around the forces and factors involved.

[Vanamonde]

I completely gave up on spaceplanes 27 times. But the 28th time worked. (I'm afraid to try a 29th time.)

[llamatoes]

I gave up on SSTOS a while back, but I have what I think is a winning design.

[Wait- Was That Important?]

I just don't bother with spaceplanes, with somewhere around 200 hours into KSP.

1.) Building a flight escape system for spaceplanes is far more difficult than a launch escape system for rockets- you can't add too much weight or you'll unbalance the craft, it can't be too large, and the cockpit often has important components like docking ports or, even worse, the cockpit can be an integral part of the plane. For that matter, when taking off from the runway there's a very small change of successfully saving Kerbals if something goes wrong, so you wind up losing alot more Kerbals on planes than rockets.

2.) Piloting planes are hard, and they can become unbalanced in flight or reentry, making it likely you'll lose the ship if not your Kerbals, especially when dealing with large complex planes and heavy payloads.

3.) SSTO's or just spaceplanes, as a rule, require more engineering to lift payloads into orbit. A 20 part LV for me takes 30 tons to LKO, whereas a 20 part spaceplane doesn't even go to space today. Lifting large payloads with spaceplanes is difficult, and it's also tough to carry any appreciable amount of crew with them. I'm aware that there are spaceplanes that can lift 40 tons or so into LKO, but at the same time those planes often have high part values.

I just don't see the appeal, especially with how broken the aerodynamic system is.

[Exclipse]

Spaceplanes are perfect how they are, you just need to learn more.

[Astronox]

When it would be to easy to build a Spaceplane, where would the challenge be to do so?

There are anough mods, so when someone fails to design a spaceplane and don´t cares

for a personal success, he can install mods to get the fail designs to work.

Or download a working one.

I did six spceplanes till now and they all failed. But i dont give up and keep them get better.

[LiquidKameleon]

Last week I really tried my best to create a nice orbit-worthy spaceplane transport stuff to my station, but a plane that can take off by itself and reach orbit without any dispendable boosters is almost a myth. I built and scrapped around 10 different prototypes, and the last one that I believe possibly had enough rocket power to achieve orbit was thereby too heavy to even lift off. The main problem is that they can't be too heavy because they depend on aerodynamic lift while leaving the atmosphere.

[RawChicken]

Spaceplanes are perfect how they are, you just need to learn more.

Exactly.

I also had lots of problems designing a spaceplane till I dd!

It could seem hard, but it isnt really. You need to keep trying and see where your error or failure is.

Ive had tons of failed spaceplanes till I made a few that work like a charm!

How card could rocket engineer be anyways? Spaceplane hard.

[EndlessWaves]

The main problem is that they can't be too heavy because they depend on aerodynamic lift while leaving the atmosphere.

That may be the problem. Wings are great at slowing you down for a landing but they won't do any favours for fuel efficiency. While leaving the atmosphere you should be using them as little as possible - keep them parallel to the direction of travel.

[Cdr_Zeta]

Greetings From The Desk Of Cdr Zeta On Planet Kerbin:

After many hours into the game over the past few weeks, I have been working on the space plane.

All aspects of Kerbal Engineering are taken into account at Kerbin Academy and I am proud to present my livestream where I happen to be ironing out some of the various issues of building these necessary planes:

http://www.twitch.tv/cdr_zeta

Pay me a visit - I am on almost every nite and am working on a suitable rescue plane. I have or will be upgrading some of the various mods, and use mostly stock parts.

The engines are in fact 'VERY' efficient, and have developed both a short and long range version.

I have yet to add the orbital portion, and it 'MUST' be re-useable to be an effective rescue plane.

The planes are mostly for moving parts to different bases, and exploration, and rescue operations for now.

I will be adding a vehicle to my plane and am trying to work out some problems with getting this done.

My planes are very flyable; have to use a gamepad or joystick and the game controller settings do just fine.

I am also still working out balance issues.

Good Luck (!) and hop on over ! I expect to be working on planes for a few more nites !

Cdr Zeta

Edited April 21, 2013 by Cdr_Zeta
typos

[M5000]

I've been trying a lot longer than you to get a working spaceplane, OP, and more importantly a working SSTO spaceplane to add to my grand tour vessel (because a corresponding rocket SSTO would be far too heavy) and I've never gotten a working spaceplane. About to go build though.. Keep going.

[Scottiths]

Spaceplanes are really hard to design and fly. Part of the issue is that depending on how you design it, it may have a completly different flight profile than another plane (depending on how much thrust it has). I tried for a long long time to get one to work and it finally worked because I got my TWR up enough to keep the assent profile roughly lined up (only 10 degrees lower) than where the craft was actually pointing. If you have a low TWR on assent then the plane tends to have a velocity vector that is significantly lower than where your nose is pointing.

Here is the plane I built and figured out how to fly. It carries 6 Kerbals in the crew compartment and 3 pilots. The only non stock parts are MechJeb2 (to hold headings) the crew tank (because it looks cool) and 2 modular multi wheels. The flight profile is set Mechjeb to 90.5 degrees (because the stupid runway does not point exactly 90 degrees) with 15 degree up. Once the plane is off the ground (it lifts off slightly after the end of the runway) switch to 90 degree heading with 60 degrees up. At 10,000 meters pitch to 30 degrees. When the air intake is down to .75 switch to 20 degree angle. Once the air intake is .12 fire up the rockets. when the air is down to .1 cut the air jets and cruise up to altitude and circularize. I am left with about 400m/s Dv when all is said and done. You have to make sure that CoG is always in front of CoL and take into account how the fuel is being burned so that it is still (very slightly) behind after all fuel is spent.

If I try to deviate from this assent plan by much I end up failing. If I try to have a lower TWR then the assent plan changes to be a lower pitch because the thrust can't keep up. Anyway, here is a picture of my craft to give you an idea. The only purpose of it is to carry Kerbals to and from my space station.

https://www.dropbox.com/s/4dt4vvlj2jz5h7a/screenshot49.png

*edit*

There are 4 turbojet engines on the back, and on the wings are 2 aerospikes.

[Cdr_Zeta]

Hello,

Nice !

I thought why build space planes to go into space; they are for in the atmosphere...but you could have a space plane on a moon - IE still a rescue vehicle; or a transport.

I also still go with as small as possible to get the job done.

We only need enough fuel for a little over 1/2 an orbit; or maybe 1/3 with a base en route for refuel; but this may add risk; so there is a risk versus efficiency; and time; maybe we dont have alot of real time; a 1/4 or 1/3 orbit looks inviting..I never tought of adding the other fuel for a space portion; but why at 10,000km well I guess I didnt look at where space begins yet; just where the plane goes bonkers; havnt worked that problem yet.

I should consider adding a rocket stage so I can get my range; the only problem is major risk and added weight on landing; I may opt for long range no-space for now and add rockets later; I been too long working on these planes; but I have made major progress and am a happy camper!

Cdr Zeta

[Scottiths]

10,000 Km is where you stop the steep climb because it is where the atmosphere has a nice balance of available air and low drag. If you keep the 60 degree climb above 10,000 you will start to see your air plummet very very fast and you will experience flame out shortly there after. The atmosphere actually ends at 70,000 km (so you have to go to 70,001 Km to actually have a stable orbit)

[Wait- Was That Important?]

10,000 Km is where you stop the steep climb because it is where the atmosphere has a nice balance of available air and low drag. If you keep the 60 degree climb above 10,000 you will start to see your air plummet very very fast and you will experience flame out shortly there after. The atmosphere actually ends at 70,000 km (so you have to go to 70,001 Km to actually have a stable orbit)

The atmosphere ends at 69,040m or so. What you're experiencing is random variance with how KSP rounds the numbers for the orbit, it won't actually degrade over time.

[Scottiths]

The atmosphere ends at 69,040m or so. What you're experiencing is random variance with how KSP rounds the numbers for the orbit, it won't actually degrade over time.

I didn't know that. So I could actually get to 69.5Km and be ok then?

[Cdr_Zeta]

Hello,

Well I didnt get too much into the specifics; I didnt know that atmosphere was available above 10,000KM; 70,000KM thats like 210,000 feet?

I would have to look at that again and take my plane up there and recheck the attitude angles; I wonder if you have to have more wingspan up there to have stability; my plane's wingspan is small so it craps out around 10 - that may me 10km not 10,000km? Well up there anyways haha!

Cdr Zeta

[EndlessWaves]

I didn't know that. So I could actually get to 69.5Km and be ok then?

Actually if you're not flying it yourself then anything with a periapsis above the auto-kill point (circa 25km) is stable despite the fact it's passing through the atmosphere.

Picking up speed on the jets isn't needed but helps efficiency. You should do it at the highest height your jets will function which will depend on the ratio of intakes to jets and can be anywhere between 30km and 10km (although if it's that low you're probably using rubbish intakes, the ram intakes are the only ones worth bothering with currently).