ULTIMATE AVIATION CHALLENGE: Fly an aircraft around the world

[Phoxtane]

Well yeah. That's why it's the ultimate challenge and all that. But then where would Kermankind be if upon encountering some slight difficulty, such as the fact that the task at hand is impossible, everyone threw their arms up in the air and buggered off to the pub instead?

Stressed, boring, and quite drunk I presume. 8)

[comradephil]

I typically solve that by making a duplicate of the fuselage parts I use, with fuel storage set to zero. Then I just put fuel-containing parts near centre of gravity, and empty fuselages elsewhere.

The problem, obviously, is reduced fuel capacity relative to the plane's size.

Ideal solution would be ability to cross-feed fuel tanks so that they all drain at the same rate, which would negate any movements of the centre of gravity...

Indeed, I think that that's something that'll have to be implemented when spaceplanes are.

[Tiberion]

I downloaded the solar array mod and ran some numbers.

one C7 engine depletes 1 c7 stanrdard fuselage tank in almost exactly 4 minutes at default throttle, which comes out to 3.12 fuel units per second (henceforth fU/s)

Putting 4x solar arrays on the tank dropped it to 2.14 fU/s at an added mass of 1.6 Mass Units (henceforth mU) (0.4 mU per solar panel)

So doing maths on that means it would take 13 arrays working on one tank to offset the drain of one standard C7 engine, adding 5.2 mU.

So if you can design a plane that:

Has a tank large enough to attach 13 arrays to

Can carry 5.2 mU of dead weight

stay aloft with 1 standard C7 engine

then theoretically you can fly forever*

Gonna build a BigWing glider later and see how much I ca squeeze out.

Might be an interesting alternative to trying to drag a bunch of fuel up there and keep it aloft.

*Forever being as long as you can stand to fly really slowly, babysitting a machine that would like to fall out of the air)

WARNING: Using this will actually make your fuel consumption negative, and you can make the fuel amount go past the tanks starting value. If you let it go long enough, depending on the data type the fuel is stored in, you could encounter an overflow error and crash the game, so take care

It would take a long time, though.

[foamyesque]

Alrighty, doing this in 10.1 with a fixed drag model.

Hour 1:

I have slightly more than an hour's worth of fuel left at that throttle setting. I don't think I'm gonna make it. =(

[millsw]

I've done it...outside the atmosphere ;P 8)

[Warringer]

You know... with the new upper atmosphere you can simply leave the lower and go on an orbit.

[Tiberion]

I have slightly more than an hour's worth of fuel left at that throttle setting. I don't think I'm gonna make it. =(

It says you went 957KM over land, unless I am mistaken the planet is 1200KM.

You were 80% around, as long as your course was mostly circular.

My testplane without any solar cells is averaging 900km an hour, so slightly slower than yours, unfortunately I am only getting about 45minutes of fuel in the air right now.

[Kryten]

The diameter of the planet is 1200km, so the circumference is about 3700km-meaning he was more like 25% of the way.

[Tiberion]

Heh yes.. that does make more sense.

Geometry FAIL.

[fauxjargon]

It would be cool if we had atmospheric-only engines which have a much higher fuel economy - if you don\'t need to carry oxidizer then your fuel will go much further. Modern turbofans are spectacularly efficient and of course, you wouldn\'t see many long-haul flights if those aircraft had to carry their oxygen with them. A rocket running on liquid oxygen and RP-1 (which is basically kerosene, so very similar to jet fuel) requires 2.7 times (by mass) as much liquid oxygen as fuel. Plus, insulation to help keep it cool - you don\'t need that for kerosene. So, if you want to try and build an atmospheric flight vehicle, its fair to say that you can legitimately improve fuel economy by a factor of 3.7 (pretending you have no oxidizer in those fuel tanks). In addition, one could reasonably go to a factor of 5 or 6 to compensate for the differences in thermal efficiency between a rocket and a turbofan engine. If you\'re making a fighter plane improve your fuel efficiency by maybe a factor of 4 because a turbojet is not as efficient as a turbofan by a long shot.

I have 'atmospheric flight only' versions of a couple different fuel tanks that do not change in mass as they empty - in the interest of fairness I just set their dry mass to their wet mass - this keeps my flight characteristics consistent throughout my burns. I have my fuel economy (thrust same, burnrate 20%) in my 'atmospheric flight only' engines increased by a factor of 5. IMO these are reasonable changes and don\'t feel like cheating to me.

I think that expanding Kerbal Space Program\'s capacity to include more interesting atmospheric flight possibilities is maybe a more interesting (from my point of view) angle than more space stuff. Kerbal Air and Space Program?

[Sordid]

Air-breathing engines are planned, but for the time being the rules of the challenge are what they are. Yes, I\'m aware it\'s quite impossible. That\'s why it\'s the ultimate challenge and all.

[koberko]

Hi guys!

I\'m currently testing my plane, but on smaller scale; plane is currently flying for 1h and 30min and has crossed 850 km with 3 tanks of fuel (one hour of powered flight and till now 30min of gliding)... When it will be done with gliding stage, I\'ll scale up design, to see how far that will go... and gliding could take a while; now it has constant forward velocity of 30m/s and drop rate of some 1-2m/s... and it\'s still at 2300 m

I\'ll post images when flight will be over.

[Sordid]

That sounds promising. Whaddya know, it might actually be doable. Keep us informed, FOR !!SCIENCE!!

[Tiberion]

Just for a rough idea, if you can average 200m/s it will take over 5 hours to go around. Gliding doesn\'t work right in game since we don\'t have aerofoils modeled and drag is probably too high (as soon as you cut thrust you immediately slow down to 30-50m/s if you can stay mostly level....) so its REALLY slow, and the time would be.. much more.

[koberko]

Here is couple of images of test plane... I have canceled glide due to ridiculously slow speed (it stabilized at 15m/s, and drop rate of just 0.2-0.5 m/s).

I have made another one, but I couldn\'t make him stable by him self (with help of SAS), so he didn\'t fly well on his own (It required small adjustment every couple minutes). And that\'s not good, because I plan to make it 'automated' so that I can leave him to fly over night.

[SteevyT]

And that\'s not good, because I plan to make it 'automated' so that I can leave him to fly over night.

For that to work it has to be stabilized without SAS\'s.

[Tiberion]

a 'blue' tuned SAS can hold it at a +pitch sufficient to keep it aloft, given enough thrust. Getting enough fuel to keep up that much thrust for 5 hours aloft is definitely a big challenge

[SteevyT]

Don\'t the SAS\'s hold a fixed direction? 1/4 of the way around the planet the plane will be pointed straight up.

[Kryten]

They don\'t have to; there are a few mod ones that don\'t.

[Tiberion]

Hmm, I think the blue one was holding with respect to the ground, I flew it for an hour and didnt notice pitch increasing.

If thats the case, you wont be able to do it unmanned, since it would be an issue even at level flight since we don\'t have aero-modeling to stabilize planes on the pitch axis.. not that you can really maintain true level flight with reasonable thrust currently.

[Kryten]

The blue isn\'t fixed relative to anything; it just damps unwanted movement and kills rotation, like the simple in the command pod.

[foamyesque]

I will defeat this challenge yet, even if I need to resort to staging to do it.

[foamyesque]

I have a plane that can do this. Now to wait twenty+ hours.

[Guest Flixxbeatz]

This one could probably do it:

...just needing more fuel conservation tactics practice o_o

[foamyesque]

It has the fuel. I don\'t know if it has the balance or if I have the patience. We\'ll see! =)