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Ljas
Finland725 Posts
On April 09 2015 18:52 Cyro wrote: fuel costs with rocket engine are so huge compared to air breathing engines I don't know about that. Then again, I've never built an efficient spaceplane. I can build a standard rocket that can get to a stable 2000km orbit with around 12k. The spaceplane you uploaded earlier costs 41k. I wonder how much reusability comes into play in the long run? | ||
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stenole
Norway869 Posts
On April 09 2015 18:52 Cyro wrote: Kinda funny that i fixed it without even realizing >_______> so i've been thinking, gotta check wing mass etc. With any significant mass on wings, it's probably better to ascend at like 15-20 degrees ish with a spaceplane? how do people usually do that, or generally make craft capable of maneuvering in orbit for a while and returning? I can get to orbit but the fuel costs with rocket engine are so huge compared to air breathing engines I play the game mod-less, so if you have any physics altering mods like FAR this might not apply. I assume you're wondering how to get to space in a normal space plane. The problems lie mostly in the design and not so much the flying. If you have a plane that has enough lift, enough thrust, enough fuel and enough fuel intake, you should be able to gradually ascend to 30000m+ at orbital speed using only air breathing engines. If you want to fly around in space, you need to add rocket fuel and rocket engines as well which means you need to add more lift, air breathing thrust, liquid fuel and air intake. The same goes for if you want to deliver a package into space. You'll need more of the same 4 things. Your design needs to be able to function in the atmosphere, so you need to make sure you have your center of lift always a little bit behind your center of mass. That means you need to make sure that fuel usage and package delivery doesn't move your center of mass too much. This gets a little harder for a larger craft. If you want your craft to be controllable in space (and the transition into space) you need to make sure that the center of mass is right in front of your center of thrust. If you start putting parts assymmetrically, this will force the plane to pull in some unwanted direction. You can somewhat compensate with RCS and SAS modules. Or you can rotate your engines slightly to keep things lined up. What will happen when your engines start running out of air in the upper atmosphere is that they will fail one engine at a time instead of failing evenly. Because the atmosphere is thinner up there, it also means your wings can't compensate as much. So unless you watch your engines carefully while going up, and throttle down, you'll lose control of the craft. You can make all your engines point individually at the center of mass to fix this. What I usually do is ascend at 70ish degrees up until about 10000m, then flatten out to 20 or so degrees. Once your plane is going fast enough or your air intake is starting to get low, you flatten your trajectory even more. It might be better to watch the vertical speed meter than your angle at this point. Eventually your engines will start to die and you need to lower your throttle to keep some life in them. Once your engines are running at such low power that they aren't helping you get into space, you switch to rocket engines and close all the intakes (best done with hotkeys). At this point you pull up to go steeper until you are at about 50000m. The drag should be low enough that it doesn't affect your climb as much. After this, use your rocket engines to push your apolapse etc etc. | ||
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Cyro
United Kingdom20328 Posts
If you want to fly around in space, you need to add rocket fuel and rocket engines as well which means you need to add more lift, air breathing thrust, liquid fuel and air intake. I found the RAPIER engine fit nicely there. A single one was sufficient for lighter plane. I could manually disable air engines symetrically or all at once when approaching high atmosphere, then that engine switches automatically when it's too starved thanks for the post :D | ||
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Jetaap
France4814 Posts
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Cyro
United Kingdom20328 Posts
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Ljas
Finland725 Posts
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Cyro
United Kingdom20328 Posts
I'm also interested in building a space station, but IDK what to make it out of, what to generally do with it or exactly how to make it (i know basic theory for rendezvous but not the little details and i suck at manually docking) | ||
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Simberto
Germany11856 Posts
Especially for launching satellites into lower orbits it should work very well, but theoretically you should be able to scale it up to get much larger stuff into orbit. And once you are in orbit, there is no difference in how you got there. | ||
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Cyro
United Kingdom20328 Posts
I'm thinking totally star wars style ![[image loading]](http://img1.wikia.nocookie.net/__cb20080121180934/starwars/images/3/3e/HyperdriveRing_ICS.jpg) but you could have a symetrical system just attached to the front of the ship (docking thing on nose) | ||
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Simberto
Germany11856 Posts
But generally, building some sort of propulsion device and putting it into orbit first, then docking your spaceplane to it for missions would totally be possible (Also needlessly complicated, but that is a different question entirely) I am not quite sure if any of the other bodies in the Kerbol Systems do have an atmosphere with enough oxygen to use air-breathing engines in it. If that were the case, you could use that idea to do a mission to one of those. (Looking it up, apparently Laythe has Oxygen in it's atmosphere). So i guess this would actually be a viable (And cool) concept for a Laythe mission. For any other mission, while this could work (And be cool) it would also be kind of pointless, as there is really no point in dragging all these Jet engines across the system just to drag them back to Kerbin afterwards. | ||
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Cyro
United Kingdom20328 Posts
BUT MY FUN :D | ||
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Jetaap
France4814 Posts
But after all this is what this game is about, setting your own challenges | ||
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Simberto
Germany11856 Posts
You just need to make sure you have enough fuel on board the propulsion System to Carry your Spaceplane to Laythe and back, and possibly to refuel your Spaceplane for multiple Starts/Landings. Also build a plane that can Land rather well without a runway, it would really suck if it explodes on Laythe. | ||
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Cyro
United Kingdom20328 Posts
Ion engines (would need a huge array of them though) are still interesting to me, because they should give much more delta V if you expend a large percentage of the fuel. I'm thinking a LOT of engines though, like 16-32 ish or maybe more - depends how much weight they add to the craft. If i'm doubling thrust on the ion stage for only a 50% increase in overall craft mass, sure that sounds awesome. I do not know how lack of TWR would impact transferring into a planetary orbit. It might make it difficult to do any more than minmus flyby's with a dockable ion engine array :D | ||
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Simberto
Germany11856 Posts
TWR does not affect your ability to do anything on a planetary scale. You always have enough time for your maneuvers, it just becomes annoying if your TWR is too low because you will have to wait for ages of real time. The only situations where TWR is relevant is landing and starting. And possible some sharp brakes for orbital insertion, but usually it doesn't matter. | ||
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SKC
Brazil18828 Posts
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Cyro
United Kingdom20328 Posts
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SKC
Brazil18828 Posts
It just doesn't make much practical sense to use a spaceplane because it isn't helpful in most planets and the whole point of the moving refueling station is being able to go anywhere. | ||
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Cyro
United Kingdom20328 Posts
will be awesome if this thing flies :D It flew, but not so good returns past ~8-10 way. Not worth the effort to iterate on it | ||
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nimbim
Germany985 Posts
On April 10 2015 01:44 Cyro wrote: I've never done an orbital insertion to a different planet in system before, is it much harder than kerbin to moon transfers? Ion engines (would need a huge array of them though) are still interesting to me, because they should give much more delta V if you expend a large percentage of the fuel. I'm thinking a LOT of engines though, like 16-32 ish or maybe more - depends how much weight they add to the craft. If i'm doubling thrust on the ion stage for only a 50% increase in overall craft mass, sure that sounds awesome. I do not know how lack of TWR would impact transferring into a planetary orbit. It might make it difficult to do any more than minmus flyby's with a dockable ion engine array :D It takes a bit of practice to get decent encounters with your target, but getting into the SOI should be easy. Duna and Eve are obvious first targets because you can use their atmosphere to aerobrake. If you want to bring your Kerbals back home from the surface better try Duna first and Eve after every other planet. Don't stack ion engines like that, that would increase the mass more than it increases the thrust, thus diminishing the efficiency. Basically if you want to use more than 2 ion engines because low TWR is boring, you should rather use a LV-N or maybe a Rockomax 48-7S depending on the rocket's mass. Low TWR does not hurt at all during interplanetary transfers. Multiple burns while you are at your periapsis will make full use of the Oberth effect. http://en.wikipedia.org/wiki/Oberth_effect | ||
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