Kerbodyne SSTO Division: Omnibus Thread

[Wanderfound]

Revival of an old challenge: http://forum.kerbalspaceprogram.com/threads/112497-Spaceplane-Speed-Challenge-Redux-Minmus-Ice-Races

[eddiew]

Kerbodyne Liftjet.The reusable SRB.

That... that's the knobbliest thing I've ever seen you make xD I'm actually a bit surprised that FAR doesn't throw a strop with regards to all the panels and batteries and science packages on the outside. Last I tried that it was highlighting them as bright yellow drag sources O_o

[blowfish]

That... that's the knobbliest thing I've ever seen you make xD I'm actually a bit surprised that FAR doesn't throw a strop with regards to all the panels and batteries and science packages on the outside. Last I tried that it was highlighting them as bright yellow drag sources O_o

They definitely create drag, but less than you might think. Remember, Cd (what is highlighted in yellow) is referenced to (usually) surface area, so a small part that isn't very aerodynamic will be highlighted even if it's creating much less drag than other parts.

It also matters less with rockets because you're not going as fast at the same altitude - by the time you pick up speed you're already above most of the atmosphere.

[eddiew]

They definitely create drag, but less than you might think. Remember, Cd (what is highlighted in yellow) is referenced to (usually) surface area, so a small part that isn't very aerodynamic will be highlighted even if it's creating much less drag than other parts.

It also matters less with rockets because you're not going as fast at the same altitude - by the time you pick up speed you're already above most of the atmosphere.

Is there any easy way to see the absolute drag that a component is causing? (And indeed the overall drag of the vessel?)

Last time I tried it was on the outside of

and they ascend much more like a plane than a rocket. I've since redesigned and ended up with a little one that fits a small cargo bay and has roughly 2k delta-v by orbit. I feel like it flies better than with bits on the outside, but that could just be the placebo effect

[blowfish]

Is there any easy way to see the absolute drag that a component is causing? (And indeed the overall drag of the vessel?)

I don't know a way to see overall drag (except multiplying dynamic pressure * reference area * Cd as seen in the FAR flight data window), but there is a way to see the drag of individual parts. In the space center scene, click the FAR button and somewhere there should be a show aero forces option. When enabled, you can right click a part in flight and FAR will tell you how much drag and lift (where applicable) a part is creating.

[eddiew]

I don't know a way to see overall drag (except multiplying dynamic pressure * reference area * Cd as seen in the FAR flight data window), but there is a way to see the drag of individual parts. In the space center scene, click the FAR button and somewhere there should be a show aero forces option. When enabled, you can right click a part in flight and FAR will tell you how much drag and lift (where applicable) a part is creating.

Wow, I never knew about that, cheers! I'll give it a go next sesh, will be interesting to see what's dragging and what isn't

[Wanderfound]

That... that's the knobbliest thing I've ever seen you make xD I'm actually a bit surprised that FAR doesn't throw a strop with regards to all the panels and batteries and science packages on the outside. Last I tried that it was highlighting them as bright yellow drag sources O_o

I'd rather do it with shielded panels and inline batteries, but the weight penalty is too punishing on a microprobe. The sooner they eliminate massless parts the better.

[Wanderfound]

I've been wanting to do a vid on how to use FAR analyses to correct aerodynamic flaws, but I actually have a really hard time designing deliberately bad planes.

Anyone feel like anonymously (or not, your call) donating a "broken" plane to be fixed on video? Preferably something that can be fixed while still at least vaguely resembling the original, but with as much diverse red (i.e. spread out throughout the analysis, not just in one area) as possible in the numbers.

[eddiew]

I'd lay odds I have a couple of designs from way back when it was christmas and I was but a mere rookie, that'll show some red at higher altitudes. I'll have a look when I get home tonight, if you're still lacking a donor

[eddiew]

Well since nobody else wants to volunteer their services as n00b builder, I shall offer one of my earliest birds for sacrifice.

Craft file here

. Based loosely on a Kerbodyne Goblin, with the brief of getting 6 kerbals and a small cargo (Station Science experiments usually) to LKO with as much delta-v left as possible. Generally arrived with 900-950.

It's flyable, but it gets red lights at all of the usual checkpoints:

- 10km @ mach1

- 20km @ mach 2.2

- 25km @ mach 4

It was using B9 RCS thrusters, which I stripped off, so it can't currently dock with anything xD

[capi3101]

I've been trying to learn how to use FAR for a few weeks now; I've had a single successful plane flight to orbit and have worked on a grand total of three designs. Actually, it was eddiew who clued me into this thread, and he suggested I put up this one:

Destabilizes much past Mach 3. Originally had a Standard Canard for the central vertical rudder, and the horizontal Standard Canards were level with the engines. Actually flew a little better back then but had some fairly horrific sideslip. Latest re-design doesn't take off before reaching the end of the Runway. This plane has never made orbit. All stock parts with the exception of the front gear - which is just a customized 2x Small Gear Bay. I've been told it needs more tailplane and when I dropped by the forums this morning eddiew had suggested putting something in between the tail ends of the outboard nacelle units and the tail end of the fuselage to reduce the drag I'm seeing there.

Actually, any design help here would be much appreciated.

Edited March 13, 2015 by capi3101

[Jovus]

I'm guessing you're seeing the classic rear-delta pitch instability at high speeds, among other things. Try setting those front canards to a deflection around 40 or 50, then set their AoA to -100% and then their pitch response to 50%. What this'll do is turn them from lifting canards to control canards - they'll remain parallel to the AoA most of the time, giving you much greater high AoA stability.

As for not making it off the runway, I'd guess that has to do with wheel placement. (It's the usual suspect.) Either that, or you simply don't have enough pitch authority; in the latter case, replace those delta deluxe winglets on your horizontal stabilizer with some real wings. Or, for extra cool points, remove them entirely, and then make your rear pitch control into 'structural wings' that fill out the gap sections between the fuselage and your outrider fuel tanks.

[eddiew]

...Actually, it was eddiew who clued me into this thread, and he suggested I put up this one:...

Ohai You'll need to supply the .craft file from your /saves/<game>/SPH folder I think ^^

[capi3101]

I'll get it up there when I can get a chance. I'll probably have to ditch the big wheel up in front before I release it for public annihilation consumption.

[Wanderfound]

The latest vid:

Trebuchet fix-up.

[Wanderfound]

Final version of the Trebuchet from the video: https://www.dropbox.com/s/lu0r0fyxuqjqwcf/Spaceplane%20Trebuchet%20Revised.craft?dl=0

[Wanderfound]

Testflight of the Trebuchet:

[Wanderfound]

No cargo bay? No problem.

Kerbodyne Viper. Business and pleasure.

Flight test at http://s1378.photobucket.com/user/craigmotbey/Kerbal/Beta/Kerbodyne%20Showroom/Viper/story

Alternate format at http://s1378.photobucket.com/user/craigmotbey/slideshow/Kerbal/Beta/Kerbodyne%20Showroom/Viper

Craft file at https://www.dropbox.com/s/xuboaxds441auxm/Kerbodyne%20Viper.craft?dl=0

[eddiew]

The latest vid:

http://youtu.be/Ew7ytMVG0Vs

Trebuchet fix-up.

That was fascinating, thank you! I had no idea the mid canards were on yaw control - I can only blame savage n00bery (and hope that I haven't done the same on anything since!) I'm impressed that you managed to completely remove the canards though, I'd kind of assumed that all spaceplanes in KSP needed them, since all but the tiny ones have such things!

The aerospike was largely a desperate attempt to get some sort of range in LKO, while I was still holding out against the lure of nuclear power. I'd have liked it to shuttle 6 crew to Munar orbit and back, but never quite managed it. In later times, I've realised that if I'd flattened the nacelles so that the rapiers could operate in pairs, then it'd have had a better chance. And maybe it should even have been 2 rapiers, 1 turbojet, and 2 LV 909s - such are the thoughts that never once occurred to me at the time

Your final version looks so much prettier with the strakes and smoother wing transitions... there's a lot to be said for the theory that you can how easily a plane will go to space just by looking at it.

[Wanderfound]

That was fascinating, thank you! I had no idea the mid canards were on yaw control - I can only blame savage n00bery (and hope that I haven't done the same on anything since!) I'm impressed that you managed to completely remove the canards though, I'd kind of assumed that all spaceplanes in KSP needed them, since all but the tiny ones have such things!

The aerospike was largely a desperate attempt to get some sort of range in LKO, while I was still holding out against the lure of nuclear power. I'd have liked it to shuttle 6 crew to Munar orbit and back, but never quite managed it. In later times, I've realised that if I'd flattened the nacelles so that the rapiers could operate in pairs, then it'd have had a better chance. And maybe it should even have been 2 rapiers, 1 turbojet, and 2 LV 909s - such are the thoughts that never once occurred to me at the time

Your final version looks so much prettier with the strakes and smoother wing transitions... there's a lot to be said for the theory that you can how easily a plane will go to space just by looking at it.

Your best non-nuke option on that design would probably be either the RAP/Turbo/LV-909 combo you suggested (if you flattened the nacelles) or four RAPIERs plus an LV-909 (with the current setup). As well as less weight than the Aerospike, the LV-909 also gimbals; the lack of gimbal on Aerospikes is a nuisance for spaceplanes, 'cos they usually have off-centre CoM.

For a low-tech option, four turbos plus an LV-T45 would work, too.

Canards are rarely required, but often nice. You do need to crank up the authority a bit on your pitch surfaces if you don't have 'em, though.

- - - Updated - - -

Viper N.

Go all the places, do all the science.

Test flight at http://s1378.photobucket.com/user/craigmotbey/Kerbal/Beta/Kerbodyne%20Showroom/Viper%20NS/story

Alternate format at http://s1378.photobucket.com/user/craigmotbey/slideshow/Kerbal/Beta/Kerbodyne%20Showroom/Viper%20NS

Craft file at https://www.dropbox.com/s/xoce1vefrj0j0ip/Kerbodyne%20Viper%20N.craft?dl=0

Edited March 21, 2015 by Wanderfound

[Wanderfound]

Kerbodyne Dart. Is there a shortage of cargo bays or something?

Flight demo at http://s1378.photobucket.com/user/craigmotbey/Kerbal/Beta/Kerbodyne%20Showroom/Dart/story

Alternate format at http://s1378.photobucket.com/user/craigmotbey/slideshow/Kerbal/Beta/Kerbodyne%20Showroom/Dart

Craft file at https://www.dropbox.com/s/7pttukc5s787ymd/Kerbodyne%20Dart.craft?dl=0

Edited March 17, 2015 by Wanderfound

[eddiew]

I'm rather liking these triangular shapes from the Viper and the Dart. The nosecone-delivery mechanism is... interestingly low tech. I may have to look into that, having just fired up a new career run.

[Wanderfound]

It's a nice airframe; swap the nosecone and inline cockpit on the Dart for a normal Mk1 cockpit and you'd have a nice little aerobatics plane.

[Wanderfound]

Kerbodyne Dart GTHO. Zoomy.

Flight test at http://s1378.photobucket.com/user/craigmotbey/Dart%20GTHO/story

Alternate format at http://s1378.photobucket.com/user/craigmotbey/slideshow/Dart%20GTHO

Craft file at https://www.dropbox.com/s/hnn6j1ax9n2sxjs/Kerbodyne%20Dart%20GTHO.craft?dl=0

[eddiew]

Darnit, stop posting fun looking planes for a bit! I don't even have turbojets in my new career game yet and I'm getting SPH withdrawal :<