What's the best advice you have for supersonic jet construction?

[YourEverydayWaffle]

So far, this is my technique, which sort of limits what I can achieve with supersonic flight:

• Keep things lightweight
  
• Use as little lifting surfaces as possible, as these do generate a decent amount of drag
  
• Use Whiplash (the bigger jet engines), combined with shock cone intakes
  
• Adding more engines will do you no good (keep it at one if possible), just gets you to top speed a bit faster, with a lower top speed.
  

My current record with jet engines and my own design was a single engine jet with about 600 fuel onboard, which just broke 1000 m/s at about 1 km altitude, followed closely by a two-engine jet with way more lifting ability, which hit 965 m/s at about 200 meters up.

The fastest I've made one so far:

What advice would you give for those designing supersonic jets, now that 1.x.x is in place, and supersonic physics and dynamic engine thrust is far more realistic? What are your records and specs with that advice?

Edited June 3, 2015 by YourEverydayWaffle
added image

[Feradose]

You dont need to cut the weight down that much, my 131 ton cargo plane goes supersonic with three whiplash turboramjets. But its smart to cut down on wings, I guess I shouldnt have used big rectangular wings. Try not to do mach 4 at sea altitude

[ajburges]

Minimize intake area. 4 Structural intakes is plenty for a turbojet. More area is just more drag. Shock cone is interesting for heating resistance though.

SAS is just more mass. As long as you aren't making bombers, control surfaces and pod is plenty of authority.

Design for flight stability. 1 km/s is around the supercruise speed you can maintain for thermal balance. It takes a while to go places so you want to be able to go x4 physics warp. Canards tend to be dangerous because they encourage dynamic instability (plus they tend to be exposed to a lot of heat).

You want enough lift maintain level flight near prograde at 20+ km. While your jets may starve on air, getting your throttle (and thrust) down is how you maintain a good supercruise fuel economy. You need thin air to get rid of that drag.

Struts are draggy. Avoid.

[Red Iron Crown]

A RAPIER will get you up to a higher top speed than a Whiplash, assuming you can get it through the sound barrier (usually requires higher altitude). I like Mk2 fuselages as they combine fuel tank capacity with lifting area, you can get away with little or no wing.

[ajburges]

One problem with Mk2 is you will have higher drag, then again supercruise is about flying high enough for minimal drag regardless and Mk2 does have better capacity and mass efficiency.

I forgot to mention that you don't want radially attached sub-bodies. Those add a lot of drag.

OTOH these suggestions are to optimise the high mach profile. If you actually want to land elsewhere, you need to give some concessions to subsonic performance. Mostly lift and/or control authority. Flying hot dogs also have below average maneuverability.

[Prepper-Jack]

IIRC, I was able to hit ~ 1500 m/s recently with a single turbo at around 20k. Perhaps it could have gone faster - as I was ascending at a 45 degree angle the entire way. The probe core also exploded shortly thereafter, due to all the heat. I relied heavily on pre-coolers for intakes (and fuel). Entire thing was very streamlined (and very light - lacking large fuel reserves and a cockpit).

[YourEverydayWaffle]

A RAPIER will get you up to a higher top speed than a Whiplash, assuming you can get it through the sound barrier (usually requires higher altitude).

Yeah... but the engine sound effect SQUAD made for them is terrible...

Edited June 3, 2015 by YourEverydayWaffle

[antbin]

> getting your throttle (and thrust) down is how you maintain a good supercruise fuel economy.

This was true in 0.90, but I'm not sure if it is true in 1.x since fuel consumption is now proportional only to thrust (isp is fixed). Max thrust (and therefore fuel consumption) goes down with high altitude. High altitude means lower drag. In my experience, rather than throttling down, you should lower thrust by just flying as high as you can at full throttle (often therefore faster)!

If you want to test your theories, why not try them in a turbojet fuel economy / speed challenge that is collecting dust... /plug

Edited June 4, 2015 by antbin

[n0xiety]

>If you want to test your theories, why not try them in a turbojet fuel economy / speed challenge that is collecting dust... /plug

Just checked your challenge. Why did you forbid the use of rapier engine? Rapier is much more efficient at long range flights at really high altitudes + faster. Also i am really curious about why people don't like clipping? Without clipping it is really hard to build good looking planes. I say give the people freedom to build the best plane possible however they like without exploits ofc.

Edited June 4, 2015 by n0xiety