PLANE PROBLEM!

[Anonymous49]

i had a small mk2 spaceplane ready in the SPH. I wanna fly it. Into orbit. I've flew quite a number of planes (2 to be exact). One of them is the 4 engine commercial jet and the other is a failed single juno powered plane. While as I wanted to continue to push this forward, I unleashed the new jet plane - The Fighter 1 SSTO. 

The 4 panther engine and 2 swivels give a good amount of thrust, After reaching 100m/s I took off but then many drag came from the front according to the aerodynamic forces thingy (F12). There was a ton of drag at the back but basically nothing that gives drag in the front. What's the problem? Thanks!

[RealKerbal3x]

@Anonymous49 Exactly that. You've got way too much drag in the back. I don't think you need that many intakes, while I don't recognise the circular intakes you're using they'll probably be enough on their own and you should be able to get rid of the radial intakes and reduce your drag.

You could probably also put those RCS tanks and batteries into a cargo bay to further reduce your drag.

Edited March 9, 2021 by RealKerbal3x

[Anonymous49]

40 minutes ago, RealKerbal3x said:

@Anonymous49 Exactly that. You've got way too much drag in the back. I don't think you need that many intakes, while I don't recognise the circular intakes you're using they'll probably be enough on their own and you should be able to get rid of the radial intakes and reduce your drag.

You could probably also put those RCS tanks and batteries into a cargo bay to further reduce your drag.

ok

[Guest]

I agree about the drag (draggy items on lifting surfaces == covering solar panels with huge lights)  but also you don't have anywhere near enough lift areas for me. I like to design mine so the wings have at least the same area as the body (think would it glide if no power). 

TBH though, that thing looks so long if you launched from the vab launch pad, the nose would probably already be in space 

[Anonymous49]

11 minutes ago, FruitGoose said:

I agree about the drag (draggy items on lifting surfaces == covering solar panels with huge lights)  but also you don't have anywhere near enough lift areas for me. I like to design mine so the wings have at least the same area as the body (think would it glide if no power). 

TBH though, that thing looks so long if you launched from the vab launch pad, the nose would probably already be in space 

SPH didn't I say it?

still not working, looks like a bone now

not working still

[Guest]

6 minutes ago, Anonymous49 said:

SPH didn't I say it?

still not working, looks like a bone now

Yes you did, I was being sarcastic and missed off “instead”. 

Might have to scrap the concept or make drastic changes then. Some design ideas just don't work regardless of what you try

 

[Anonymous49]

2 minutes ago, FruitGoose said:

Yes you did, I was being sarcastic and missed off “instead”. 

Might have to scrap the concept or make drastic changes then. Some design ideas just don't work regardless of what you try

 

how to change it??

[Guest]

3 minutes ago, Anonymous49 said:

how to change it??

I didn't want to say thank without sounding rude but I think you'd need wings as wide as the sph for that plane to work. I don't think it can be saved TBH. It's just too long and un-planelike. Sorry.

[Anonymous49]

made it shorter, still flipped...

[jimmymcgoochie]

I don’t mean to sound rude, but that plane is ugly. Huge engines dangling off the back, excessively long and with some really weird wings scattered along its length; I’m not surprised it doesn’t fly well. The weight is pushed too far back with all the engines and most of the fuel in the rear third of the plane, causing it to flip so it travels heavy end first. The middle wings’ control surfaces will do nothing for you except a little roll control as they’re right in the middle of the plane, so will exert absolutely no force for pitching, and one tiny tail fin is probably not enough for something that long.

You seem to be trying to do too many things at once with this plane- is it intended for passenger transport, payload deployment, both, something completely different..?

My advice is to chop several of those fuel tanks out, move the jet engines much further forward and try to balance the mass better by repositioning the fuel tanks and passenger cabins/cargo bays so that the centre of mass is ahead of the centre of lift, regardless of if the tanks are full or empty, then configure the fuel priority to keep it there. Specialise for a single purpose e.g. carrying passengers into space, rather than trying to do too many things in one design (you could make a separate cargo variant by swapping the passenger cabins for cargo bays later). You should also make sure that your landing gear isn’t too far back otherwise you’ll never be able to get off the ground before running out of runway and landing will also be tricky.

[Snark]

On 3/9/2021 at 7:55 AM, Anonymous49 said:

made it shorter, still flipped...

This is the first time you've mentioned flipping, but looking at your design, I'm not surprised that it's aerodynamically unstable and wants to flip backwards in flight.

The problem is that your CoM is in the back of the plane (you've got the back end loaded down with heavy engines, and nothing very massive in the front).  A craft with a CoM in the rear is always going to want to flip-- it's unstable, like trying to throw a badminton birdie with the feathered end in front.

So if you're having instability problems, my advice would be to move the CoM significantly farther forward.