Fuel efficient plane

[Jokurr]

So just for fun, I’ve decided to create a plane that is tasked with picking up Kerbals from wherever their capsule landed (though if they land in the water they’re kinda pooched), and returning them to the KSC. As the Kerbals might land just about anywhere, the plane needs to have enough fuel to do a full trip around Kerbal.

The question then becomes, what is the most fuel efficient atmospheric engine one can build? What altitude should I be flying at? I noticed that the basic jet engine is listed as having a higher Isp than the turbojet engine, but after running a few tests, I’m thinking this data must be based off of an altitude where the turbojet engine hasn’t reached its optimal Isp. Right now I’m leaning towards using a turbojet engine plane and flying it around 15,000m, would this be close to as efficient as I could get? I’m also thinking there would be no need for more than one engine, is that correct? What should I be using for air intake to optimize efficiency?

[sal_vager]

There was a challenge a long time back, where players had to get as far as possible on as little fuel as possible, the trick was lots of wings.

And I don't mean with the infinite glide bug either, seriously large wings were used and the craft were very slow, but man, they were frugal

[RawChicken]

Yes, so I did a plane for exactly the same reason as you. I used the turbojet engines. With this you can get to a higher altitude and travel faster than with the other jet.

Also, ive noticed its fuel eficience gets higher the higher you get, till a point which i cant remember, where it starts decreasing. So yeah, there is a sweet spot where you get least fuel consuption at a pretty fast speed (+1000 m/s).

Using one engine or 2 depends on how heavy the plane will be and the lift vector (aka wings) it has.

Try a couple desings and keep the best!

[-RanZ-]

Isn't the regular jet a lot more fuel efficient? I am building a small plane I can send to Laythe and would like some efficiency also

[Kerbolnaut]

You'll usually get better fuel efficiency from flying higher. With a fast enough aircraft, you can go around the world several times by making a series of sub-orbital hops out of the atmosphere. If you convert a sub-orbital hop into a proper orbit, you'll be able to circumnavigate the globe as many times as you like.

The easiest way to make sure you can go from anywhere on Kerbin to anywhere else is to make a spaceplane which can go into orbit, land, orbit again, and land again. I've already built a spaceplane which can do that. The tricky part is making a spaceplane which can do that and takeoff/land from almost anywhere on Kerbin. It's difficult to do that with slopes, and I'm not sure if that's even possible with water.

[Jokurr]

Isn't the regular jet a lot more fuel efficient? I am building a small plane I can send to Laythe and would like some efficiency also

At low altitudes it most definitely is. However, I noticed with the turbojet engine once you get above 9km altitude or so, your speed really starts to increase the higher you go, with little change in fuel consumption rate. If you want to fly close to the surface than the basic engine seems to be the way to go.

There was a challenge a long time back, where players had to get as far as possible on as little fuel as possible, the trick was lots of wings.

And I don't mean with the infinite glide bug either, seriously large wings were used and the craft were very slow, but man, they were frugal

I did not realize that wingspan had a large effect on efficiency, I’ll have to try introducing a larger wings and see what the results are. Thanks!

[lobsterbark]

You need to use the turbojets, there not good at low altitudes, but at higher altitudes there is less drag, and plus, when you run out of fuel, you are already at a high altitude and can glide for a long period of time.

[lobsterbark]

Isn't the regular jet a lot more fuel efficient? I am building a small plane I can send to Laythe and would like some efficiency also

Laythe has a thinner atmosphere, and turbojets are a lot more efficient there.

[Fuzzy Dunlop]

Tried this a while back, this was my first attempt.

Acctually was very stable, kept airbourne with no manual control, flew around in huge circles.

I once left in running when I went for night out, when I got back in over 4 hours later it still had almost half its fuel left, I took control but I was drunk and I crashed it.

[spacecake]

I took control but I was drunk and I crashed it.

I think there is a lesson to be learned there

[automcdonough]

it doesn't take much altitude for those..

[satcharna]

I believe the most economic vessel would be a massive solar-powered ion glider. Cool as it might be, the insanely low top speed might very well make you go insane before getting close to the target.

If you're interested in landing on water, the Firespitter addon includes seaplane landing gear.

[Jokurr]

If you're interested in landing on water, the Firespitter addon includes seaplane landing gear.

Cool, I was thinking about searching for a mod that would do this, I didn't want to leave some of my kerbals stranded at sea