Help me perfect my first super high altitude plane? B-9 Aerospace parts

[agentweez]

So this is my untitled Test bed airframe for super high altitude research and to prototype SSTO and general spaceplane technology.

In flight tests, she'll reach 1000 m/sec and about 31km and is ALMOST capable of a round-kerbin run. She flies... moderately well with SAS support, she's aerodynamically sound and really flies a lot better once she reaches ~10km and gets over 400m/sec. My problem is I'm having trouble taking flex out of the wing segments, and she doesn't glide worth a damn once she runs out of fuel. In fact, she pretty much just goes into a modified ballistic nose dive as soon as she can't thrust vector anymore (this makes sense to me) but I havent been able to attach wing surfaces that make even the smallest bit of difference once she loses power. Do the wings need to be larger? Can I get away with strapping a booster on her back for her to ignite once she nears the edge of atmosphere to achieve orbit?

Suggestions, modified craft files, etc on how to get her into orbit and or maximizing her ability to glide?

https://dl.dropboxusercontent.com/u/21160358/SSTO%20TEST%20BED.craft - Craft file

[agentweez]

Also: is it possible to get bigger landing gear from another mod pack? I was sorely disappointed that there were no new landing gear bays in B-9.

[Loabstas]

yeah try TT modular wheels

[urablahblah]

You said it falls right down when out of fuel, is that maybe due to the intakes you have? IIRC aren't those things pretty heavy? Also, does you COM shift far forward once your fuel is depleted?

[agentweez]

Im not sure how heavy they are, that's a very good question. It doesn't FEEL too off balance when low on fuel, she just couldn't get her nose up once she dried out. I'll messwith different intakes when I get home

[Kidneythump]

Protip try to design your craft in a way so that the COM doesn't stray to far from the COL even when low on fuel, the easiest way of doing this is using a empty fuselage as well as one full of fuel and just switching between them, this way you can position your engines/intakes/RCS to balance the craft

[Immashift]

You're using mods here so I'll suggest a really useful one - TAC fuel balancer.

It can, in real time on its own, balance all fuel tanks in your craft, as well as lock particular ones from draining, among other things.

It's extremely useful when you have a finely balanced plane.

Also note: Your Center of lift should be slighty behind the center of mass. Too far forward and it will flip out at the slightest touch of the controls, too far back, and your plane will either not want to respond to controls, or will nosedive constantly. I usually get the best results by having the center of lift indicator sort of half inside the upper rear of the center of mass indicator.

[Rune]

Yup, that nice ballistic arc is what happens when you are too aerodynamically stable: you can't take the nose out of prograde no matter how hard you try, so prograde becomes more and more "groundwards". Two solutions: give yourself more control authority (bigger ailerons on the back, or canards on the front). Or make it slightly less stablee (CoL just behind CoM, but both very close). The last one has the issue that it depends on how much your CoM moves around as you empty fuel.

Rune. Also, 1000m/s at 31km is slow. How are you doing in the T/W department?

[Autochton]

I use Taverio's Pizza and Aerospace landing gear, the stock ones become S size, and then adds M, L and XL versions in progressively bigger scales.

For wing flex, I would consider Procedural Wings, or struts until the morning comes. It is possible to add internal strutting by zooming and rotating your camera such that your viewpoint is inside one wing, then you can attach struts from there so that they're hidden from outside the wing.

[Matticus88]

I think front canards will help you alot.

[agentweez]

You're using mods here so I'll suggest a really useful one - TAC fuel balancer.

It can, in real time on its own, balance all fuel tanks in your craft, as well as lock particular ones from draining, among other things.

It's extremely useful when you have a finely balanced plane.

Also note: Your Center of lift should be slighty behind the center of mass. Too far forward and it will flip out at the slightest touch of the controls, too far back, and your plane will either not want to respond to controls, or will nosedive constantly. I usually get the best results by having the center of lift indicator sort of half inside the upper rear of the center of mass indicator.

Yeah, I'm not sure if there's anyway to visualize CoM during midflight, it would be really revealing I think. I'd heard similar claims about how the CoL and CoM should be touching, I'm certain I can do a little bit better than that, this is LITERALLY the first plane I've built that flies straight and true, so I'm cerain I'm making all sorts of rookie mistakes.

Yup, that nice ballistic arc is what happens when you are too aerodynamically stable: you can't take the nose out of prograde no matter how hard you try, so prograde becomes more and more "groundwards". Two solutions: give yourself more control authority (bigger ailerons on the back, or canards on the front). Or make it slightly less stablee (CoL just behind CoM, but both very close). The last one has the issue that it depends on how much your CoM moves around as you empty fuel.

Rune. Also, 1000m/s at 31km is slow. How are you doing in the T/W department?

Not sure, on the T/W Rune, should probably hook up Engineer to it. She never really gets above 1000 m/sec anywhere. Maybe she needs less drag but those intakes are the only thing giving her any go at the really thin atmosphere levels, and she's already pretty streamlined for drag besides the suckers. I really have no clue if there's anyway to visualize CoM in flight, or what reduced fuel weight in the tanks looks like. I was able to determine that she still flies really cleanly when she's hideously low on fuel. Like 5% fuel left she's still very stable in flight. I don't know about her speed, I know she's not moving fast enough in the really thin atmosphere to maintain altitude, I have to fly in the skipping method, diving down to 20-25 km to get a big breath of air, and then scream on full throttle back to her AP, ad infinitum.

I think front canards will help you alot.

Noted, I'll try that out.

I use Taverio's Pizza and Aerospace landing gear, the stock ones become S size, and then adds M, L and XL versions in progressively bigger scales.

For wing flex, I would consider Procedural Wings, or struts until the morning comes. It is possible to add internal strutting by zooming and rotating your camera such that your viewpoint is inside one wing, then you can attach struts from there so that they're hidden from outside the wing.

Awesome tip on the bigger wheels. Are there videos on how to do the internal struts? I tried to find the sweet spot you mentioned to little avail.