Basic jet engines VS Turbojet engines

[pauix]

I've finally unlocked the Turbojet engines on my new science save, and I'm gonna upgrade one of my spaceplanes' engines. Is there any big difference between the basic engine and the turbojet besides the engine's thrust? I'm not sure how spaceplanes work and I wouldn't like to screw up one of the few designs I've made that can actually land and take off.

Edited April 25, 2014 by pauix

[luizopiloto]

basic jets works better at low altitudes... and planes with cuise altitude of 12,000m...

turbojets works like A-12 / SR-71 engines... the higher you go, the better it works, best option for space planes, but they consumes more fuel... Not a problem, because you shutdown them once you go above the stratosphere...

[FREEFALL1984]

Yeah, for low level craft use standard jets, the ISP is much better in atmosphere, but the engine requires more intake air, so once you get above about 12km expect a flame out. The turbojets are much better at high altitude and taking this into account you would normally get much better fuel economy overall per km traveled since you'll be travelling about 3 or 4 times faster at 25km than you would at 5km so best to use turbojets even for little jaunts around kerbin

if you wanted to be really really economical during in atmosphere flights, have a couple of turbojets and a couple of standard jets running off the same fuel tanks, and run the standards during takeoff and climbing/landing, and then once you hit 12km switch out to the turbos, you might be carrying an extra 2 ton around with you but overall i find it still more efficient and since they're all breathe the same air you only need the same amount of intakes..

[Claw]

Besides higher thrust and fuel consumption (as noted) they are slighly heavier, which may be a factor for center of mass depending on how small your margin is.

They are fairly swapable. It shouldn't mess up your airplane, but make a separate "version 2" in case you need to do some tweaks.

What you may find is that your plane can get a bit higher and faster. That may cause your plane to misbehave because it hasn't been there before. It might have stability or control issues and it might need some adjustment to go higher/faster. On the other hand, it could be completely fine.

[pauix]

Thanks to everyone for your answers, I'll muck around with both engines and try to make a hybrid plane! Hopefully this time I'll be able to get to the badlands

[Pecan]

...try to make a hybrid plane! Hopefully this time I'll be able to get to the badlands

You won't need to. One turbojet will be sufficient. Just give it plenty of fuel [NB: a 180-unit rocket-fuel tank, with the oxidiser tweaked out is the lightest way to get fuel] and fly high (15km+). What you lose in the fuel consumed you'll make up in the speed you get. Plus, of course, you can glide a long way from 15km up!

[tavert]

Here, have some data (assuming you're not using FAR)

Javascript is disabled. View full album

[Pecan]

Oh man tavert, is your birthday due or something? You keep coming up with such excellent stuff that we all owe you presents!

[tavert]

Just randomly browsing the forums slightly more often the last few days than the few months beforehand. All of these are old calculations, with the exception of the updated engine charts for 0.23.5.

[Pondafarr]

So how does one generate this data? (Great stuff, bookmarked that imgur album!)

[cantab]

Ingame I suppose you'd use an autopilot to cruise at certain altitudes, and right-click to read off the engine performance numbers.