Help needed on improving my spaceplane

[Dr-Drunk]

Hey all!

So I have a confession... I've played KSP pretty much since the earliest aplha and ever since then I have never designed a succesfull spaceplane.

But recently, with the implimentation of 0.90 I've been looking into a budget way of bringing Kerbals into orbit to man my stations. As such, I present to you: The X-77 Precision! So named because it has never missed the ground once....

So this is the plane. After loads of tweaking the wings and thrust I atleast got it to fly but it still flies like an absolute brick. The turning rate is terrible and once I reach higher altitudes it becomes impossible to keep the nose pointed up wich sends the plane casually drifting down back towards the surface. It doesn't spin out of control or anything and can be landed relatively easilly but it's impossible to get it into space.

Here's some more pictures to help with the troubleshooting process:

So yea as stated.. The goal of this craft would be to take Kerbals into orbit to deliver them to my stations and bring back the Kerbals already there. It doesn't need to be capable of lifting heavy loads and doesn't need an insane amount of Dv. The furthest it would have to reach as far as my current plans go is a 800Km circular orbit around Kerbin where my furthest station is located. So if anyone has any ideas to help me improve this thing, please let me know!

Mods used for this or that I can use parts from:

B9 Aerospace

FAR

Karbonite

KSP Interstellar

Procedural Dynamics

And some others that don't include usable stuff for planes.

Edited January 9, 2015 by Dr-Drunk

[capi3101]

At first glance, your plane has got insufficient lift and insufficient air intake for its mass (I say that; I'm not as familiar with the B9 parts as I should be). I'm also not sold on its level of pitch authority. Its CoM-CoL arrangement is also favorable for stable flight - meaning its maneuverability sucks. Ideally the two would be closer together.

Increasing your lift is probably your best bet for fixing the problem. In stock, you want to should for a combined lift coefficient from all the lift-generating parts to be roughly equal to that of your mass. I don't know if that rule still holds in FAR or not.

[Tank Buddy]

Your CoL is too far back from the CoM. Your control surfaces cannot provide enough torque to turn the aircraft quickly with the CoL as far back as it is. Add canards or move the lifting surfaces forward to improve performance.

Turbojets perform better at higher altitudes compared to the standard jet engines. Also, LV-Ns do not have sufficient TWR (0.11!) to push that plane into orbit, especially without turbojets and with such a heavy ship. I would recommend trying to make a small SSTO from stock parts and experimenting with different mass, lift, jet, and rocket engine combinations. This ship needs MOAR boosters!

[Van Disaster]

* Probably don't need the extra intakes, but I'm not flying it so I can't tell

* Use the other turbojets, those ones run out of puff very early under FAR.

* Don't overlap wings ( biplane ) under FAR, you'll lose lift. You don't have that much wing as it is for the craft mass.

* CoL way too far back - for supersonic craft I generally reckon on putting it *on* CoM in the hangar, it'll move backwards.

I think you might actually get to space with two ( of the other ) turbojets and two NERVAs in that, if you lightened it, taking off the side fuselage pieces and using something smaller like the bigger intake with the Mk1 end to mount the jets on.

You can get away with very little thrust on Mk2 sized shuttles:

Not sure that would reach your 800km orbit though.

Edited January 9, 2015 by Van Disaster

[Starhawk]

I don't use B9 or FAR, but I do love spaceplanes.

I would have to echo the CoL closer to CoM comments above.

Use turbojets instead of jets if you're going to space.

It seems way too heavy to me for your purpose. If you want it that heavy, you need moar lift. My favourite SSTO design takes two kerbals to orbit with a lot of fuel left, and only uses one turbojet and two 48-7s's. The lighter you make it the less thrust you need. And the less lift.

If you only want to take kerbals to orbit, it might be best to start with the fewest, lightest engines possible. LV-N's are great for long range, but they are very heavy to carry all the way up to orbit on a spaceplane. They also have very poor performance in atmosphere.

Good luck!

Edited January 9, 2015 by Starhawk

[arise257]

Agree with all points above. Also, I love the aesthetic of your plane - you'll get it working!

[Van Disaster]

So I bashed out a version of that aircraft using b9 parts, and that works fine too:

but: using B9 already, why not use SABREs?

So I tried out your wing design also:

Well, getting CoL forwards enough to have some control is hard with that design, but it works. Just try not to overlap the ends.

Anyway, jets & NERVAs are workable, that wing is also workable - take some weight off and you should be ok.