Spaceplane Help

[jkool702]

So I've been trying to build a SSTO spaceplane and cant seem to get it to work. Ive read a few guides and feel like my plane should be working, but its not.

Here are images of it:

http://imgur.com/0kn7TOt,MfUyS4m,oFG4pfs

http://imgur.com/0kn7TOt,MfUyS4m,oFG4pfs#1

http://imgur.com/0kn7TOt,MfUyS4m,oFG4pfs#2

I can't tell if its the plane design or my (bad) piloting skills thats causing it not to work. I usually go at 45 degree ascent to ~10k, 10 degree ascent to ~13k, and then 0-5 degree ascent for the rest. It seems no matter what I do though I top out at around 18k altitude and about 900 m/s speed...I cant seem to get past there. Dropping my altitude to ~16k I can get my speed up to about 930 m/s, but always lose it when I try to ascend again.

Does anyone have any tips on design and / or piloting for the plane?

Thanks!

Also, it seems that if I roll even the slightest bit SAS is completely unable to stabalize it...it continues to roll back and forth trying to stabalize it for literally the rest of the flight...any ideas how to fix that as well?

[kStrout]

Start smaller, that is gigantic for a 2 kerbal plane. Start with 1 kerbal SSTO's and try to make them as small as possible, you will be amazed by their performance, also if you do want to go big, nukes are hard to use because of their small amounts of thrust, try RAPIERs or areospikes instead. But seriously, ram intake - inline cockpit - the big 1.25m fuel tank - rapier add some wings and fly it well, it should get to space.

- - - Updated - - -

Also 900m/s is an acceptable amount of speed for something that big, if you want to go faster, you will need more engines per ton, my suggestion, go smaller instead of adding more engines.

[DeMatt]

From what I can see, you have too much jet engine power and not enough rocket engine power. The slanted Elevon 5's are probably confusing SAS; switch 'em out for 3's or 4's. The zillion Engine Pre-coolers are a waste of space - too little LF compared to the Mk1 Liquid Fuel Fuselage, miniscule Air Intake capability.

I assume you don't have RAPIER engines yet, and are just trying for a low Kerbin orbit with your two kerbonauts; in that case, you might want to look at Scott Manley's

tutorial videos, where he's building a spaceplane with about the same level of technology and performance.

[BlueCanary]

Turbojets won't go much faster than that with that big a craft really, especially since struts now add a lot of drag (I think). Use Rapiers if you've got them, or go for a smaller, less draggy design.

You'll also be getting a lot of drag from all the intakes in the precoolers, normal LF tanks would probably work better and carry more fuel for less weight too.

You're probably best off starting from scratch with a much smaller plane, going for lots of LF, only 1-2 intakes per engine, and minimum drag.

[jkool702]

Thanks for the tips. I will try downsizing and switching the elevons. I will also remove some of the precoolers if their intake isnt worth all that much. I dont have rapiers unlocked quite yet, but they were the next thing i was planning on getting from the tech tree and i have 809 science atm, so I will have them sooner than later (probably sometime today, as I have a mission about to visit jool / bop for the first time which I anticipate will give me loads of science). Thanks for the tips!

EDIT: I'll try and get away with less struts too. That design requires a crazy amount of struts to keep the wings stable (otherwise it flapped like a bird). Again I guess smaller will help me out with that... I'll also check out scott manleys vids

Edited June 21, 2015 by jkool702

[Tex_NL]

Also check out Scott Manley's latest tutorials:

[capi3101]

What exactly are you trying to do with the plane? If you're just trying to send to Kerbals up to orbit, I'd agree with what's already been said.

Guidelines for stock air:

*25% payload fraction

*1 Turbojet/200 kN of rocket per 15 tonnes of mass maximum -or- 1 RAPIER per 13 tonnes of mass

*1.5 kN of SAS per tonne of take-off mass (trust me, this does help matters).

*Plan for ~1800 m/s of rocket

Wings I'm not sure about in stock these days; anymore I fly FAR and the guidelines are different (I'd shoot for a wing root equal to half the length of the fuselage, a wing loading of 0.3 (about the same as a Eurofighter Typhoon) and an aspect ratio of about 2 (same as Concorde or the Shuttle) - both of which can be determined from the estimated mass of the craft). Now, the drag models are closer to one another than they used to be but there's still sufficient difference down in the soup to make any advice I'd give you suspect. Still, if your plane is just sending two Kerbals to orbit, you shouldn't need much wing (your payload is literally just the cockpit - two tonnes, say three for extra bits like batteries and solar panels, 12 tonnes theoretical takeoff mass so a single Turbojet could do the job; I'd recommend pairing it with a pair of Thuds to keep things simple).

Back in the day the advice was 1 unit of Lift Coefficient per tonne of plane; a Delta Wing and Wing Connector A both had a lift coefficient of 2, so a twelve tonne plane would require a pair of two Wing Connector As with a Delta on the end. Couldn't tell you what the guideline is these days...