Fearless Son

Damn, that thing is glorious. I too have been trying to build a Mk. 3 cargo spaceplane, though I was only trying for one orange fuel tank. However, I ran into the same problem as you with it having trouble getting off the ground before the end of the runway. Landing was a pain too. I think the current stock wheels are just too damn small for something of this size and mass.

Great looking designs. I especially like the Asp, and I may need to try building myself an Auriga (I have been struggling with a Mk. 3 cargo spaceplane for a while now.) I wish there was a way to do it without airhogging though. How many intakes do these things have? - - - Updated - - - Am I the only one who's first thought upon seeing that cockpit was "Quack!"? - - - Updated - - - So I tried duplicating the Asp as closely as I could without the airhogging assembly on the bottom of the wings (I prefer to avoid airhogging so I am exploring other intake methods) and that thing just does not have enough lift to get it off the runway. How do you manage to take this thing off?

New revision of the Stellar Swan: Total part count is over 440, unfortunately. I had to add plenty of extra lifting surfaces to balance the weight. Still cannot lift its nose from the runway, having to run off the edge and turn up over the ocean. Intake is not a problem. The six intakes above this wing here are mirrored below the wing with bi-couplers, each wing is mirrored across the hull, for twenty-four intakes, plus two angled-slightly-down intakes near the front of the craft for twenty six total intakes. Not sure how drag affects a plane based on position relative to the center of mass, but I wanted as many intakes as close to the center of mass and as far behind it as possible to make sure the plane stays stable while air-breathing. As you can see, I also placed a large number of reaction-wheel stabilizers because this thing is so heavy it needs all the help it can get to turn effectively in atmosphere. And the reason for the twenty-six intakes (which I now realize I may need to increase by a few) are these eighteen turbojet engines to get this massive beast off the ground. Originally I had four to six aerospike engines here, but they proved insufficient thrust and the only places I could add them upset the balance of thrust across the center of mass. So I ended up ripping out that whole assembly and replacing it with a KR-L2 Advanced Engine. However, that is sill not enough thrust to get from the apex of my air-breathing flight to orbit. I might need more areospikes to supplement it. In terms of flying profile, this still has some problems. Flying it obviously slows framerate, but I accepted that when I built it. It turns quickly enough, but requires some time before velocity vector becomes parallel with the direction of the plane (it has a lot of inertia, obviously.) When it gets to a certain altitude and speed at full thrust, it has a problem where the nose starts to point upward and I have to reduce thrust to keep the nose where I want it to be. Normally I would think the problem was draining fuel from the front of the craft, but I deliberately lock down the front fuel takes to keep the center of mass forward (and I can transfer fuel back once the rear tanks are exhausted.) So far though this is not too much of a problem because this kicks in just before I have to start reducing throttle anyway to keep accelerating without flameout. Landing has been troubling. I have been able to fly up and turn around in a big arc and head back to the Space Center easily enough. By the time I am lined up with the runway am I essentially falling in an unpowered glide, plane perfectly level with the runway, forward speed less than a hundered meters per second, vertical speed feeling reasonable though it is hard to gauge that considering the framerate is slow. It ends up crashing the plane anyway, then crashing the application. That is some crash! I suspect the mass of the plane has a lot to do with it. Overall, I think I am going to give up on this project, at least until the next update. While I believe the overall design is sound, I am running into the limits of what I believe is practical in stock. I want to wait and see what aerospace improvements were were told is coming are (I hope larger lifting surfaces and engines and intakes are on the way if only to reduce the engineering complexity of something this size.) I am really fond of this design and I hope to refine it with new parts rather than abandon it.

I want to add something to what Liowen said: in both interplanetary transfer and orbital rendezvous, there is one concept that needs to be stressed and that is timing, timing, timing. In either case, you cannot just point in the general direction of your target, thrust on full, and hope for the best. You need to wait for your window of opportunity to come up before you start if you expect to make it with a minimum of fuel. Starting with bad timing will expend literally tons of fuel just trying to make the right corrections. In the case rendezvous with an object in equatorial low-Kerbin orbit (which is probably where you will do most of your rendezvous and get the most practice at rendezvous in general) you want to wait to launch until the target is passing above the Kerbal Space Center. Likewise, make sure your gravity turn is in the direction the target is orbiting so that you do not end up orbiting the opposite direction (which is a huge pain to change once you are in it.) If you can start from an orbit and position close to the orbit and position of your target, rendezvous becomes much easier to manage. The same goes for parking an interplanetary transition module around a target planet and recovering a lander. Be sure to leave the transition module in a good orbit (preferably equatorial) and put the lander down somewhere that the orbit passes approximately above it. Then wait for the right window to come along before blasting off the lander to return to the transition module. Further, this practice will serve you well. Taking from my own experience, I have never been able to get to Duna in a way that leaves me enough fuel to get completely back to Kerbin. I always end up stuck in a high-Kerbin orbit. I do still recover the Duna craft, but I need to send a refueling drone out to rendezvous with the parked Duna craft to give it just enough juice to bring its orbit within Kerbin's atmosphere. If I could not do that rendezvous, I would have lost all Kerbals and plenty of valuable scientific data from that mission.

Getting my nose up is not really the problem I have, it is dragging the tail where I run into issues. As usual, I position the rear landing gear just beyond the center of mass, to allow it to lift itself. Unfortunately, the rear of the plane ends up so low to the ground that even a minor raise in the level of the nose on a horizontal surface will cause it to drag and engines to get shorn off. I have an idea to move the center of mass back and make this less of a concern. Pictures will follow when I have it implemented.

Did a few modifications to the design. Removed the vertical-thrusting jets in favor of more axially-thrusting turbojets. Added an additional four turbojets, two on each side, in addition to two more jet fuel tanks because I was worried I had a little too little for this many engines to chew through. This brings the total number of turbojets to sixteen. Added a lot more shock cone intakes, bringing the total number to thirty-two intakes. This seems to be the ideal ratio of intake to engine from what I have experienced. The total weighs in at 126.5 tons and 345 parts, which understandably takes a while to fly. But never the less, fly it does, this big baby gets off the ground under its own forward-thrusting jet power, if only just barely. Once clearing the runway, it still coasts while very slowly losing altitude, with the ground falling away toward the shore just slightly faster than the plane falls. I have to wait until I am out over the water before nosing up, lest the rear of the plane trail on the ground. But once that nose is up, the plane is off and climbing strongly. The problem I am now running into is that the plane begins to struggle to stay on course when it gets going high and fast. Partially I think this is due to the high part count, resulting in a little "flex" in the structure that have a subtle effect on its aerodynamics (which I hope the upcoming update will allow me to fix by replacing lots of little parts with a few big parts.) This is controllable though, requiring me to babysit the yoke and make a few minor corrections. However, once I get to a few hundred meters per second and around fifteen kilometers off the deck, this becomes more pronounced, with the plane yawing left and right, overcompensating each time I try to correct, eventually losing meaningful control as it spins. I suspect this is due to the new fuel takes and flow. I can probably solve that problem by removing the new fuel takes, adjusting the fuel to fill up some existing empty tanks more toward the middle of the structure to make up the difference. I might also re-position the intakes to be more toward the back of the plane, resting on the trailing rear of the wing to shift the center of drag back and more toward the middle. That should make it a little more controllable.

Okay, new design is ready for shakedown. Initial trials are promising, I can get it in the air under its own power and in a stable ascent profile. Full trials at transitioning from flight to low Kerbin orbit will follow. But for the moment, I have pictures of the new design to share: She is too big to capture in the space plane hanger in one profile shot, so here she is in perspective. I had to find a lot of ways of extending the wings as much as I reasonably could while still looking aerodynamic, ultimately ending with them in this gentle curve in front and another curve in back to both pull back the center of lift and add more to it in total. Another perspective shot from below. Note that I elected to go with the Mk2 cockpit instead of the Mk3 for weight reasons, and the adapter component I ultimately ended up using gave me lots of room beneath it to cram two pairs of high capacity intakes. Two other pairs of intakes are on each of the Mk2 fuel containers astride the Mk3 hull (though they are ironically mostly empty for total weight and balance reasons) with two more pairs near the ends of each wing. This makes twenty intakes in total with no air hogging. Testing will tell me if I need more than that. The main engine clusters. Eight turbojet engines on each side of the hull, four more turbojet engines at the very rear of the hull, for a total of twelve turbojets. Yes, I realize this is slightly too many for the amount of intakes I have (I understand the ideal is two high capacity intakes for every one engine.) Radially mounted around the rear turbojets are four aerospike rockets. The piece that makes this design workable at all is the extra standard jets balanced across the center of mass on the bottom of the plane. Alone, these give nowhere near enough vertical thrust for VTOL, but they do give just enough upward force to lighten the effective weight of the plane, allowing it to ascend under its own power from the runway, though I still prefer to run it straight off the end of the Kerbal Space Center runway before pulling up so as not to risk dragging the rear of the plane on the runway. Once it gets into a good ascent and is gaining speed, these jets can be deactivated to conserve fuel since they will not be needed or effective at higher altitudes. Actually getting off the runway does still require a little more thrust than the turbojets alone provide, so I trigger a short full burn from the aerospike engines as I get to the end of the runway, giving it just that little extra thrust it needs to get airborne and nose up. Once it is ascending, the rockets can be cut and let the turbojets do the work. I am thinking of naming this design the "Stellar Swan", mainly because the shape of the wings and position of the cockpit call to mind the form of a swan. The white wings and hull certainly do not hurt the image.

Is this twist only on the runway, or is it during flight? If on the runway, that usually indicates that the gear are too close together or the weight is too great on one side. If in the air, I would think it is also the weight distribution. One of the big "invisible" causes of this is the fuel distribution, if fuel is getting used up from a tank on one side of the plane but not on the other, hence one side of the plane gets slightly lighter than the other side and this becomes more pronounced the longer the flight goes on. In short, I recommend checking the fuel line flow. Maybe something is connected backwards?

What I like to do (and someone please correct me if I am wrong) is to look at where my center of lift is relative to my center of mass, then make very slight adjustments to the canards to make sure my center of lift is properly aligned just behind my center of mass. I do not do this wholely, but to a small adjustment in the canard leads to a large change in the balance, so it is great for putting the finishing touches on an otherwise nearly stable design.

Yeah, I am familiar with that one. I have gotten spaceplanes into orbit before, just never one quite this big. I actually remembered a trick that worked once for me before and I am applying it to my new design. I use some standard jet engines balanced across the center of mass and positioned to thrust downward while in forward flight. The extra thrust vector directly against the gravity vector helps the excessive mass lift off the ground. Once I get to higher altitude and greater airspeed where the turbojets can shine, I can deactivate the increasingly ineffective lifting jets. Just got a prototype of this into the air carrying appropriate cargo. Pics to follow.

In this case, I do not think that would be sufficient. A plane does not strictly need to be able to nose-up off the runway at Kerbal Space Center due to the runway being elevated. A plane can simply accelerate off the end of the runway, and if it has enough lift and thrust, can then perform a very gentle climb until it achieves sufficient clearance from the rapidly falling ground to point the nose up as far as it needs to for its ascent profile. With my plane though, it fails to achieve enough lift to even maintain altitude once off the runway. The more I think about it, the more I think I need to redesign the whole thing. I will post more pictures of my next iteration.

Okay, so after posting this last night I went back and did some hand calculations (I use exclusively stock so no mods to do it for me.) Comparing the total wing lift with the total mass tells me that I have less than half the wing I need to lift this much. I think that I shall have to redesign the layout again, if only because adjusting the fuel supply in this Mk3 setup will alter the center of mass too much for my taste. Someone mentioned splitting fuel tanks across the cargo bay forward and back, but my concern is that it will also affect the center of mass too much by draining one side before the other. I think I am going to have to go with fuel tanks on the sides of the cargo bay so that adjusting both cargo payload and fuel weight should not unbalance the craft. Maybe put some Mk2 hulls astride the Mk3 hull. I have experimented with "flying wing" type aircraft before, both as a way of cramming more functional components (such as air intakes in the front and turbojets in the back, I dislike most kinds of air hogging) into an aesthetically pleasing package and doubling-up my wing surface area to provide more lift without making a drastically bigger plane, but so far I have not noticed any gain in lift (and in fact most of my planes with that kind of design seem to have much less lift than the sum of the parts lift rating would suggest.) Can anyone elucidate me on the mechanics of making "fat" wings by carefully arranging structural wings together?

Salutations Kerbalnauts, Long time player, first time poster. Since the .90 update, I have been struggling to make an effective heavy cargo spaceplane for delivering large components to orbit in a cost-effective manner. These components are intended to be attached together into more complex structures, such as space stations or larger interplanetary vessels. I have certainly proven I can build effective spaceplanes that can reach low and mid-Kerbin orbits (almost but not quite as far as Mun in one of my models) but only for the lightest of spaceplanes. Building ones that are as heavy as I need this to be has proven much more challenging. Not the least of which is simply getting off the ground. So far, every design I have attempted (and this is only the latest of many) has trouble even getting off the runway. I try to build them with large amounts of wing surface area to give them a lot of lift, but no amount of lift ever seems enough, the speed caps out around 70 M/s by the time I hit the end of the runway on only its turbojets, and only a little more than that if I burn the rockets early to give it just that little extra thrust. Even after getting off the runway, I tend to sink just slightly faster than the ground falls away beneath me toward the shore. Let me illustrate with a few pictures: Above is the side view of my current design. I have included the center of mass, center of lift, and center of thrust indicators for reference. This view of it from above underscores just how much wing I try to put on this thing, though it seems to never be enough. View from below this time, with the cargo bay doors open so you can see the "ballast" I put in here to test the center of mass with a load onboard. My goal is to be able to transport an entire orange fuel container into orbit. It is the volume and mass of it that is more important to my design goals than the amount of fuel itself, since this is not necessarily a tanker, just something that can convey a similar size and mass to this. View from the front, shielded docking port for utility's sake. You can also see that there are sixteen conical air intakes on this thing to ensure plenty of airflow for the engines. And of course the reason for all those intakes being the six radially-mounted turbojet engines on the back, though I fear that may not be enough. Nestled between them is a quad of aerospike engines for atmospheric escape and orbital maneuvering. Detail on the intakes. I angled the ones hanging under the wing slightly downward, because I know a spaceplane of this mass flying at high altitude will likely have some serious incline and I want to ensure my air intake remains relatively efficient during that stage of the flight. And finally, detail on the landing gear. Note the two pairs of landing gear positioned just behind the center of mass. Both are equally level and adjacent to spread the weight of the plane across them so that they do not end up breaking me just by the weight of the plane pushing down. There is also a single landing gear nestled among the engines which actually hangs off the ground while on the airstrip, but the wheel extends just slightly past the radius of the engine cowling to ensure it does not scrape across the ground while taking off or landing. Any advice on how I can get a beast like this actually in the air? I mean, I know smaller and simpler is better, but in this case the size is part of the point. I have seen pictures from other people who have constructed absurdly massive spaceplanes that against all common sense make it to other worlds (very Kerbal) but I would be content just to get this into equatorial orbit and back down again.