Strategy for Very Long Range Airplanes [Stock Only]

[mrxak]

So I've never been much of a spaceplane pilot. Building them never was very interesting to me, flying them even less so. But with Science, suddenly I see spaceplanes as very useful, particularly with conducting atmospheric studies over a variety of biomes in Kerbin's atmosphere. Perhaps in the future when we have biomes for Laythe, they'd be even more useful, since surely a long-range aircraft flying through the atmosphere of a planet so far away would be more efficient than sending multiple landers that take readings as they come down to the ground in various areas of distant worlds.

Now, I understand the basics of spaceplane construction. I can absolutely build a solid, maneuverable craft capable of reaching the altitudes I want and flying around for a while. What I don't know, simply due to my inexperience, is how to tweak a craft for optimal range. To that end, I'm looking for some guidance. What makes for an extremely long-range airplane? I'm talking about around-the-world trips, here. The longer the range, the more biomes can be Science'd in a single trip.

It seems to me that higher altitudes have less air resistance, and so the plane wouldn't have to work so hard to push through it all. On the other hand, higher altitudes have to cover more distance, take more fuel to reach to begin with, and may have more intake needs, which adds weight. There's also the matter of how much lift is really needed, and how big or small a plane I should be building. Or perhaps, I should build some kind of glider that does sine waves through the atmosphere with the engines off much of the time.

So, anybody got a lot of experience with long-range aircraft? I'm not looking for anything that leaves the atmosphere, just something that can cover the most distance possible while conducting Science in either the upper or lower atmosphere (whichever gets the most range) or both (if the ideal elevation is somewhere around the 18km border).

I'm not above copying aspects of another person's spaceplane if anyone has pictures of some range-optimized craft. Please share!

[sal_vager]

Low weight is critical, and yeah you want to get high, you can run your engine at reduced throttle so it doesn't flame out and get serious long range that way.

[vetrox]

Keep it simple.

300 units of fuel and one turbojet can easily get you around kerbin on the right craft.

My biggest tip is learn to use the verticle speed indicator. Once you reach a desired altitude then you want to keep that baby at 0.

Also your ascent profile is important (just like in rockets) but this takes practice and differs alot from plane to plane. I normally fly vertically up to 12km then flatten out to gain speed. However the quicker you can get to your maximum altitude (you wont really know how high that is until you get there) the sooner you can throttle down and save fuel.

The turbo jets lose their 2200isp at around 9km? (might be slightly higher). Theres a few intake spam tricks that can get you to 40km but if you avoid spamming them I find anywhere between 20-30km is about the limit before your craft start to look silly.

The higher you go the faster you can go so although technically you are traveling further. The bonus speed you get cancels it out. The plane i just made for the bsc challenge does 1300m/s at 23km. Other planes I have made will do nearly double that speed at 40km

YOu can never have too much lift. I dont know how real aerodynamics work but in ksp I find that more lift makes maintaing high altitudes alot easier.

Once you are in the upper atmoshpere switch your capslock on so when your making minor adjustments (you will do it alot as you will be flying around the curvature of kerbin) to keep your verticle speed indicator at 0.

I fly in cockpit mode once i get quite high as its easier to see the verticle speed dial. Plus all them old school ananlog dials look pimp.

Those are just how i fly. I could be wrong but i've done plenty of around the world trips. Takes between 30-40 minutes depending on altitude.

Dont go down the rocketry road of "Moar is better". If your plane is starting to get big but cant make it then i always start over. I make planes like i make rockets in career mode. I make them as small as possible to start with then add 1 or 2 things each time until it does what i want.

EDIT: another thing to look out for is jet flameout. If you only have 1 engine this isnt the end of the world but when you have 2 or more 1 jet will flame out and send you into a spin from which you have to expend fuel recovering from. On your resource tab you have intake air. Now i dont know how its worked out but a good rule of thumb is to start throttling back when it gets down to 0.10. Although on single engine craft I have gotten to 0.2 before jet flameout but 0.10 is a good starting point.

Set an action group to turn your jets off to try and salvage the mission. if you get a flameout, turn jets off, throttle to zero wait a moment whilst the non flameout jets lose their thrust then start em up again. If your quick you can normally survive. Remember, theres no quick save whilst in atmo. All Cock ups are permanent

Edited October 31, 2013 by vetrox

[Anton P. Nym]

It actually doesn't take much to make a long-range aircraft; I sent drones like the one above from KSC to both poles, dropping a rover at each, with fuel left over.

-- Steve

[vetrox]

It actually doesn't take much to make a long-range aircraft; I sent drones like the one above from KSC to both poles, dropping a rover at each, with fuel left over.

-- Steve

Ahh kerbins poles. By far my favourite place in the Kerbol system. Im always flying over them. The south pole has some mountains nearby that are great to fly through!

[Franklin]

How did you get that off the runway with the lower tailfin? Or did you launch that from the rocket pad?

edit: And I'm probably gonna rip off that design, ha. I've tinkered around with so many small/light 'drop rover' designs, some with decoupling takeoff rigs and some that drop autonomous rovers like bombs, but that seems to be a far more compact/simple design than I've messed with so far.

Edited October 31, 2013 by Franklin

[Anton P. Nym]

How did you get that off the runway with the lower tailfin? Or did you launch that from the rocket pad?

That's an old design, before I figured out how to make aircraft that can take off from the runway. (derp) So it's a VTOL, boosted up to altitude by two of the small SRBs mounted by radial decouplers. Since then I added a pair of struts to anchor the nosecone to the wings, as physics warp showed a fair amount of bendy-wobbly going on there.

-- Steve

[arq]

Because of the current physics, the best way to go a long distance is as high as possible. By flying very very high (45km), I made a plane that could fly around Kerbin 2-3 times on 220 fuel with 5 intakes and one turbojet. At that altitude, you can fly well-over 2km/s on fumes (engine under 5%). Actually, at one point I had the velocity to be in a 48x35km 'orbit'. I used pWings and StretchyTanks to get the form-factor I wanted, but those mods are 'stock-balanced', so you could do similarly with stock parts.

One tip: Wings generate max lift at ~30deg, but intakes produce max air at 0deg (yes, they do lose air as they face away from prograde). By building in 30deg of pitch to your wings, you can maximize lift while minimizing wing area (and mass, hence drag). However, this makes the plane fly awkwardly at low altitudes because of the abundant lift and high AoA (to land it I had to point down roughly 20deg to maintain a descent), so be careful if you are inexperienced with planes.

[Vanamonde]

Before you invest a lot of time into getting the planes to work, experiment with transmitting data from them. I've just started trying it, but it seems the jets produce relatively little electricity with which to send signals. No point in making a plane that can go places if it can't send the info back.

[Zephram Kerman]

Turbojets, definitely.

In thick air, keep your speed down. (Think of the Goddard Dilemma, although this case is only similar.)

If gathering data while in flight, you'll need a lot of those fixed solar panels, or a very slow duty cycle.

In KSP (not real life) mass affects drag. So it's doubly important to make your plane as light as possible.

All of my sciencey planes have just one turbojet. But if you need two, consider mounting them vertically instead of horizontally. The second one should be on the bottom, so that if it flames out, the resultant force automatically pushes the nose down to safety.