New Player Interested in Hypersonic Flight

[Frog-]

The title really states it all I'm a relatively new player despite owning the game for around a year now I just started playing it more. I've made a couple different designs all capable of hypersonic flight (1550m/s+) but none of them are too stable, turn to sharp and the whole thing explodes and they can't reliably hit it either. I'm doing a challenge with my friend to use only stock parts and air breathing engines to see who can make the fastest plane. This Post interested me but I can't seem to replicate the design of the aurora as there are discrepancies in the pictures. I was looking to see if I could make and improve it but I guess not so I decided to make a post asking for tips on how to make a stable and reliable hypersonic air breathing aircraft in language that wouldn't be difficult for someone who is relatively new to the game to understand. Thanks in advance! 

[edit] The highest I've reaches so far is a bit over 1800 m/s but that one exploded right after because it was unstable and very twitchy. M replication of the aurora couldn't quite reach 1700m/s but was however much more stable. I'm having trouble trying to fuse them.

[Vanamonde]

Welcome to the forum.

I am not one of the airplane people, though, so I can't help you with your question. Someone will be along shortly, I'm sure. 

[DrLicor]

Hey @Frog-, welcome to the forums. 
What is really important is that the plane has to be stable and respond right to the controls as well while 100m/s as flying 1500m/s.
The stock controls aren't doing that right, they allow you to turn a sweet 70 degree bank even when going supersonic with a turn rate that the poor kerbals feet explode due the G-forces. 

A mod I really like is atmospheric autopilot, it let's you fly the plane really sweet, doesn't create big AoA's and most of all, it corrects much better than the normall SAS.
I don't know if you're a fan of realism? But FAR is also a really good mod, it ovehauls the whole stock lift and aerodynamic and gives you a great overview how stable the craft is, what AoA to maintain on certain speeds etc.. 

If you're not a fan of mods, I suggest you to either limit the rudders, elevons etc.. and press CapsLock, so you get the fine controles, the roll, yaw and pitch indicators will turn blue in fine mode and red in normall mode. 
Also, a small design standard, always make sure the CoM is in front of the CoL. The further away the CoL is behind the CoM, the more stable the craft is, but harder to maneuver. To far behind will make your craft an uncontrollable lawndart. 

The way I always build crafts is on the wings I put flaps on the wings, to increase my lift surface during take-off and landing, these don't have pitch,  yaw or roll. On top of those I put spoilers, these are only activated when hitting the brakes. And on the sides of the wings I put some Ailerons with only roll. Way back on the plane on the tail wing, I put the elevons which control pitch only. And on the tail itself the yaw control rudder. 

This way, your crafts has just enough control authority. If taking of proofs difficulty you can also increase the authority or the amount of pitch. 

The longer you make your craft, the beter it handles aerodynamics in relation to fuel storage. I also balances the CoM a bit more to the middle rather than the end of the craft. 

[Frog-]

@DrLicorHey thanks! I have yet to try any of this out but I'm fine with modding so I'll be sure to check those out! Thanks for all the advice!!!!