Hypersonic flight

[IamKerbal]

I am trying to build a hypersonic mach 5 (1800ms) plane. any tips or tricks?

[kspenjoyer1234]

I've built a hypersonic plane before (only 1400 m/s aka mach 4 though), here's some tips to make something similar to that. Keep the plane small, I made mine around 4 mk2 inline cockpits (It's the cockpit I used for my craft) long, excluding the engines. Use small wings, only around the size of a small delta wing, I used 2 wings on the front and 2 wings on the back, to make up for the lack of lift. Keep the landing gear small, but make sure they're retractable. For engines, I would avoid using a Rapier as they consume a lot of fuel and aren't as efficient in the atmosphere like other jet engines are. Also, make sure to avoid liquid fuel engines. They run out a fuel fast. I know I'm a little late to this post, but I thought it would help others that come across this post with their planes.  

[jimmymcgoochie]

Use Whiplash engines, avoid Mk2 parts as they produce lots of drag, accept that the things that make a good high-speed aircraft (small wings, low profile, low drag) also make a terrible low-speed aircraft (low lift, limited control, high takeoff/landing/stall speeds) so be prepared for some challenging handling characteristics.

Or just throw MOAR ENGINES!!!!1! at the problem, that usually fixes it.

[DeadJohn]

Are you playing with or without mods?

Without mods, RAPIER is the fastest jet engine but might not be able to reach 1800 ms as a jet. Use its rocket mode for the final burst of speed.

1800 ms risks nose overheating. Don't use the typical Mk1 pointed nose because it doesn't have high heat tolerance. Use a high heat tolerance air intake or nosecone, or mk2 cockpit despite extra drag.

There are a lot of weird designs you can try without using RAPIER at all. You could try a rocket plane with droppable jet engines to shed weight after climbing, or try a normal jet with radial or wingtip SRBs.

[Tecorian]

Also Cargo Bays are producing a lot of drag.

Try wings from the OPT Mod for the MK2 bodys (scaling them down with tweakscale)

I have best results for supersonic vehicles and spacegliders with the OPT mod.

Edited September 3 by Tecorian

[JeDoesStuff]

On 6/17/2024 at 7:03 PM, IamKerbal said:

I am trying to build a hypersonic mach 5 (1800ms) plane. any tips or tricks?

The maximum spee you can achieve with a rapier engine is 2100m/s at sea level, but you need a very specific craft for that and it wont be very useful. Conventional SSTOs get to around 1600m/s, and ones that use special drag reduction techniques with part clipping and fairings can get to 1700m/s+. note that the speed of sound changes depending on altitude and temperature. If you are optimizing purely for top speed, use a engine plate occluded fairing to achieve 0 drag and no wings, clip everything into the fairing, and fly very close to sea level. Without hyper optimization, 1800m/s+ should be achievable. If you're looking for a more practical design that isnt as glitchy and more aesthetic, here's a few tips:

• Root Fairing: A root fairing does not apply the drag of the fairing body, and if you occluded all the nodes of the fairing it will produce very little drag. If you make sure everything is in the fairing except for wings, it will minimize drag. If you don't do this, you wont be able to go as fast, but you can still achieve very fast speeds.
• Wing Area: In my testing, the optimal amount of wings for high speed is 1 wing area per 8 tons of craft.
• Altitude vs Heating: Obviously, sea level has the highest speed of sound, but heating at that altitude will prevent high speeds. The optimal altitude to fly at is 17600m above sea level
• Minimize Intakes: I've seen some differing statements on this, but I've personally been able to fuel up to 8 Rapiers with one shock cone. I would recommend not doing this, as 4 Rapiers per shock cone is the most convenient.
• Wing Incidence: If you aren't occluding everything on your craft, add a little bit of inflection to your wings. What this does is minimize the surface area of the craft that is pointed into drag, and thus reduces the drag of the craft. Ideally, you'd want to angle them 3.5 degrees, but that isn't easy with stock tools, so the smallest locked increment whilst holding shift works well enough.
• Use Rapiers: Rapiers are the only engine in the game that produce significant thrust at Mach 5, so its a must for this.

Hope this helps!