GoSlash27

That's definitely not what *she* said Seriously, it's delivering 6+ tonnes of cargo, so <13 tonnes total is pretty small. Best, -Slashy

cosmos, Sorry, I know I have zero experience with FAR, but I need to point this out: FAR derates turbojet thrust, so you can't have a turbojet powered spaceplane like you do in stock. You'll need to use either RAPIERs or a turbojet/ rocket hybrid with a lot more DV from rockets. I know a guy who's really good at FAR spaceplanes. I'll see if I can get him to help you. Best, -Slashy

Fair 'nuff. Best, -Slashy

^ And again, those big swept wings as vertical stabilizers are holding you back. You don't need rudders or giant tailplanes. They're just unnecessary weight and drag. Just a couple little fins back there are fine to keep you pointed the right way. Best, -Slashy

According to that pic, you're right in the 25-32km "wall". The objective in that portion of the flight is to maintain 20-22* AoA and let speed build on it's own. The faster you go, the more air will be shoved into your intakes. Eventually, you will begin to climb at a more rapid pace. Just gotta be patient... Remember: 22* pitch and let the speed build. Also, you don't have to start throttling back until the engines are pretty dim. If you'd like, I can post pics of what it should look like with your plane. Best, -Slashy

Because saving DV <> saving weight or cost, and these are both engineering priorities. A low t/w launcher may come out lighter overall than a high t/w launcher when the mass penalty of fuel & tankage is less than the mass penalty of adding engines to achieve higher t/w. Likewise, fuel and tankage is cheaper than an equivalent mass of engine, so it can be economically advantageous to design a low t/w launcher. I'm working this problem, and I need accurate numbers to find the solutions. It makes a huge difference if the model is overestimating the "minimum bound" by several percentage points when there's less than 0.1% change in overall vehicle mass between t/w=1.3 and t/w=2.6 (which is, incidentally, the case when using LV-1 engines on Gilly according to arkie's model). Best, -Slashy

Off to play with this spreadsheet... Best, -Slashy

Aye, but they can't necessarily modify them. It's okay; I'll get it sorted. Thanks! -Slashy

Booyah! Now to find a way to convert it to .ods... Minor point: Go= 9.82. Sweet! This is gonna save me so much time!! -Slashy

A lot of times, there's no ready way to solve for the integral of a function in weird forms. If there's a way to do 1/(C+e^(yadayada)), I'm not familiar with it. Best, -Slashy

^ What arma said. Placing ram intakes and engines is easy (they only attach in one spot). Radial intakes... it's just a matter of lining them up according to the local landmarks. And they don't have to be perfect. A little misalignment there won't throw you noticeably out of balance. You just don't want to use symmetry when placing engines or intakes on a multiengine plane or it'll wreck everything*. So what I do is this: While setting up the airplane and getting everything tweaked and balanced, I'll just slap it together using symmetry. Once I've got everything where I want it, I will yank the engines and intakes and place them individually. *Except where you have a single subassembly that contains an engine and all of it's intakes. You can place that using symmetry without suffering starvation thrust asymmetry effects. Best, -Slashy

Cosmos, Sorry, I should've specified: This is only for stock. It will not work for FAR as FAR derates turbojet thrust. I don't use FAR, so I'm not qualified to speculate about what works well using that mod. Sorry! -Slashy

Fire Dragon, No problem! All I had to do to fix it was remove the intakes and engines, then reinstall them without symmetry enabled as I show in the tutorial. First I placed the left intakes, then the left turbojet, then the right intakes, and finally the right turbojet. I removed the references to MechJeb (had to to open it) and set up an action group on button 1 to toggle the intakes and turbojets. You probably want to apply this fix to your original model in order to keep MJ and your action groups how you want them. Good luck!, -Slashy

Arma, I think you can surmise that it would be, simply from your personal experience launching from airless bodies. Any V above Vo is going to exhibit vertical acceleration. It's unavoidable. The argument seems to be whether or not this is important at V< Vo. I think the consensus here (please correct me if I'm mistaken) is that it is. Best, -Slashy

Which brings us full circle. Unfortunately for this model, the V^2/r term is necessary. It has an impact on efficiency throughout the flight. Now... if someone could integrate it into LD's formula in such a way as to not require Matlab, that'd be a huge help for everyone. Best, -Slashy

True, but I'm referring to t/w >= 1, which was the initial condition. Once you're at Vo, that's plenty to get you to orbit or escape with no DV penalty worth mentioning. In fact, if you don't start throttling back around that point, you're liable to overshoot your intended apoapsis. You could hold on longer for Ve, but not a whole lot. That's what I'm sayin'. -Slashy

Aye. So long as Vx < Vo and theta is constrained for Vy=0, "prograde" and "horizontal" are the same thing. By the time Vx = Vo, not only does it not matter what you call theta, but t/w is no longer a factor in efficiency. At that point, it's just burning prograde, either for apoapsis or escape.

LD, All due respect, but they *are* comparable. Both seek to provide a lower bound for Dv efficiency WRT t/w ratio. A model either accurately predicts empirical results or it does not. Apologies, -Slashy

http://wikisend.com/download/731806/FireDragon.craft You'll want to reset the action groups the way you want them, but it's good to go otherwise. You'll probably want to get rid of those giant swept wings as vertical stabilizers. Also, you don't really need active rudders. Best, -Slashy

Okay, that's what your problem was; asymmetric flameout due to o2 starvation. (how on Kerbin did you manage to fly that thing so fast with that going on??) Please check out my tutorial here http://forum.kerbalspaceprogram.com/threads/102182-So-you-want-to-build-a-space-plane Look at the sections regarding multiengine spaceplanes and launch profile. I'll get you the craft file back shortly. Best, -Slashy

So far, so good...

You've definitely got an asymmetric thrust deal going on here. Let me see if I can fix it...

Hang on a sec before you do that...

First issue: The staging was backwards and it launched using the LV-N.

Sorry, not following. What do you mean when you say you "can't"? What's happening? Is it running out of fuel, or you can't get it to accelerate on rockets? Something else? *edit* I tried downloading and installing your craft file, but it says you have "locked or invalid parts". *edit again* I didn't realize MJ was a "part". I've removed the references to it in my copy. Hope it works... Best, -Slashy