Fuel efficient low atmosphere flight to KSC 2.

[Vostok]

The challenge: fly to Kerbal Space Centre 2 with as little fuel as possible.

Restrictions: No mods. No cheats, (like making one tank have infinite fuel). No flying above the second gradation of blue on the altimeter, I.e. you have to be within atmosphere, not orbiting.

Any type of craft you want, it can be a rocket, a plane, or some kind of combination.

For anybody who doesn\'t know where KSC 2 is, Here is a map.

Good luck, and don\'t forget, it\'s not a race, it\'s all about the fuel.

1. Antbin - 164.6 kg

2. JellyCubes - 209.8 kg

3. SBaL - 342.7 kg

4. Keptin - 488 kg

5. Android089 - 502 kg

Doesn\'t count: Me, but I did manage 500 units exactly. But I didn\'t land, since I did this for the Kerbal Mail service challenge.

[antbin]

Nice! I\'ll get this challenge started. A few clarifying questions:

• 
  [li]Do you have to successfully land at KSC2? What counts as \'arriving\'?[/li]
  [li]The end of the 2nd gradation on the altimeter is at about 30,000m, isn\'t it? That should be plenty of room for anything powered by turbojets. 8)[/li]
  

This ship is unoptimized, but it\'s a start. One turbojet, two delta wings, fueled by two FL-T250 droptanks on pylons plus three body segments.

Flew at full throttle the entire way, cruising at as high an altitude as the engine could manage with about 50/60 units of airflow.

I had (almost) drained the biggest (3rd gen) body tank, and had two Mk3-to-Mk2 tanks left when I taxied up to (through) the launch pad.

So that\'s [tt]2x250 + ~225 = [glow=maroon,2,300]725 kg[/glow][/tt].

Let\'s get this started!

[Vostok]

Here\'s my first attempt entirely low atmosphere flight, no ramjets.

Total fuel used: 1600 kg - 4x C7 Mk1 Fuselage, jet fuel, 2x FL-T500 Fuel Tank

Engines: 2x standard jet engines.

Flight Report: Flew at 1/3 throttle (just enough to keep the engines burning) at low atmospheric level, Engines ran out at the start of the mountain range that KSC 2 is in. Glided the last few kilometres, to land nicely.

Damage: Lost one wing section with aileron whilst taxiing about KSC 2. Kerbals were scared for the whole trip.

Images:

[Vostok]

I\'d say some sort of landing is required, just for the command pod to come to stop on the ground. Although, if you blow up parts on landing and they contain fuel, I\'d say the exploded fuel counts towards the total

[antbin]

OK, take 2, with a bit more tuning I made it on just under 600 units of fuel: 2 x 225kg Mk3 body panels, and one 150kg Mk2-3 adapter. Maybe 590kg? I forgot to check precisely.

Full flight profile here.

Brakes on, Winding up before liftoff

Approaching KSC2

Flyby!

Successful landing.

[keptin]

488kg

I gave this a shot. 2x225kg Mk3 tanks and 1x150kg Mk2-3, just as antbin, with the exception of going for high-aspect wings over a low-aspect delta and U-2 style landing gear to shed some weight.

the Helios IV, run 2:

*edit*, did it in roughly 488kg of fuel...awww yeah. 8)

The trick was changing my flight plan to low and slow--12500m going ~350m/s at a hair less than 1/3rd throttle led to incredible fuel savings. Given how much fuel I had left over, I could probably ditch the weight of the 150kg tank and do it with 450kg clean. It took over an hour, so like hell I\'m going through that again...unless someone can best 488kg

Flight Profile 2, 488kg: https://imgur.com/a/En6Kf#0

[JellyCubes]

Did it with a single FL-T250 with 40.2 kg of fuel left, so it used 209.8 kg of fuel. Took 70 minutes.

• 
  [li]Fuel efficient[/li]
  [li]Fast[/li]
  

Pick one.

[fireblade42]

I did this with 550kg of fuel. It\'s not as impressive as JellyCubes\', but it only took about 27 minutes. I also ran out of fuel about 5 minutes till landing. Used a FL-T250 and 2 Mk2.

Flight Screens

takeoff

eep no fuel

packages bounce right

[Mr_Orion]

Did it with a single FL-T250 with 40.2 kg of fuel left, so it used 209.8 kg of fuel. Took 70 minutes.

• 
  [li]Fuel efficient[/li]
  [li]Fast[/li]
  

Pick one.

I don\'t think this qualifies. It uses the rocket fuel tanks, which weight a lot less, despite having so much fuel. This difference in weight makes the increased efficiency apparent. Not to mention that eventually the atmospheric engines will have their own fuel type.

[antbin]

low and slow--12500m going ~350m/s at a hair less than 1/3rd throttle led to incredible fuel savings.

Very cool, this is what I was hoping to learn from this challenge! 8) There is some optimizing to do here...

About the wing choice - I picked delta wings because the part specs say they have a 1.9 lift, 0.07 mass., and 0.02 drag. The high-aspect wings have the same drag but 1.2 lift and 0.05 mass, right? Without knowing how simply KSP calculates lift, I figured the deltas were a more effective part.

[keptin]

Very cool, this is what I was hoping to learn from this challenge! 8) There is some optimizing to do here...

About the wing choice - I picked delta wings because the part specs say they have a 1.9 lift, 0.07 mass., and 0.02 drag. The high-aspect wings have the same drag but 1.2 lift and 0.05 mass, right? Without knowing how simply KSP calculates lift, I figured the deltas were a more effective part.

So far my experience with high-aspect wings in KSP has been a good one, especially with the altitude challenge. They have 1.6lift/0.05mass=32lift/1mass. Deltas have 27lift/1mass. The downside [in the game] is that high-aspect wings suffer from increased drag, so that gave me the idea to decrease my speed and take advantage of the high lift.

I don\'t think this qualifies.

There aren\'t any rules against it up top, so I don\'t see why it wouldn\'t qualify as long as it\'s not benefiting from the control surface thrust glitch.

[antbin]

All right JellyCubes, let the delta vs. high-aspect wars begin! 190.5kg

(Mostly) full flight profile here

The only thing that worries me is that the ultimate goal is probably to exploit the infinite glide bug =P

[Hrsch]

The only thing that worries me is that the ultimate goal is probably to exploit the infinite glide bug =P

thats what i\'m actually doing.

im still flying for 1 1/2 hours(99% without engines) and used 40,8kg fuel so far.

i need something about four or five mor hours to reach the facility so i think i will stop now.

its unbelievable boring.

but i am sure i could do this with less than 100kg fuel.

if somebody tells me how to use the spoiler-function i will edit my post.

[Kosmo-not]

if somebody tells me how to use the spoiler-function i will edit my post.

The 'nuclear hazard sign'(?) button below the font size drop box will put whatever you have selected inside spoiler tags.

[Android089]

Made it, didn\'t take photos till I actually saw the Kerbal space center. I didn\'t think I would even make it that far.

Uploaded with ImageShack.us

The last tank had 98kg left. For a total weight of 502kg of fuel used.

[antbin]

Uh oh, Hrsch, that looks very very competitive...

Yeah, this challenge can be reeeeal boring. ASAS and trim are your friend (am flying as I\'m typing this).

Unfortunately, ASAS doesn\'t seem to account for Kerbin\'s rotation beneath you, so every so often you have to reset your heading with F-tap, Alt-X (to take out the trim you\'ve put on), and then hold Alt-S to nose up again. Almost makes me want to fly with an avionics package.

[Hrsch]

Kerbin\'s rotation beneath you, so every so often you have to reset your heading with F-tap, Alt-X (to take out the trim you\'ve put on), and then hold Alt-S to nose up again

i found out how to balance the plane so it corrects its pitch by itself(i was surprised how aerodynamic it behaves).

there is no need to correct the pitch manually(while it flew i was in the supermarket.).

but i guess after something like 3 hours i have to increase height(but im not sure).

i hope i didnt misunderstood you

if you want i can upload the ship for you so you can see it yourself.

[antbin]

Hrsch, very cool, so are you gliding with ASAS turned on, or just with a stable plane, neatly trimmed?

Anyhow, I converted to high-aspect and re-flew the same fuselage at an even lower throttle setting (1-1/4 notches). It cruised at about 180 m/s, 10,500m. The final glide into KSC could use some tweaking, but time for me to get to &*&$% work! - 164.6kg

Full flight album here

[Hrsch]

i turned asas on.

164.6kg is awesome.

u used just two wheels?

[keptin]

very cool antbin, I think that\'s close to as efficient as possible, but I was able to ditch the U-2 style gear and go for full 1-wheel glider. Landing is tricky, but I managed it on a test flight. Don\'t have time for another run to KSP 2 though.

[antbin]

u used just two wheels?

ASAS can keep a 2-wheeled ship level on landing (at least until you brake it slow enough not to smash the wings off).

For takeoff, I used detachable pylons on the wingtips, with a skid / wheel attached. Semi-cheating (in that the plane can\'t do a return trip)

How Keptin slows down on landing with 1 wheel is beyond me. ???

[keptin]

It\'s super easy to takeoff with one wheel. The plane sits in takeoff position on the runway, so you just lock ASAS and just throttle up...no skids necessary. To land, you zero throttle and flare up to burn speed before touching down. Moving the ASAS to the front, cockpit, fuel, engine, allows the canards to be further from the wing and provides more control during climb and landing.

HeliosV download: http://dl.dropbox.com/u/66999462/HeliosV.craft

With the weight reduction of one wheel, you will see some fuel savings. The flight plan is just as critical; here\'s what I\'ve got so far for the Helios V:

1. Lock ASAS, start engines and throttle to 2.5 notches.

2. Set heading to KSP 2

3. Set pitch to 18 degrees, set throttle to 1.3 notches (your speed should be around 55-65m/s during the low-altitude climb, 0-5000ft, with climb rate of 10m/s)

4. At 5000m increase throttle to 1.5 notches, climb to 12500m

5. Level off at 12500m, cruise to KSP2

6. Begin landing sequence at ~5000-8000m from landing zone; reduce throttle and altitude.

[antbin]

Keptin, very cool. This is why I love these challenges - Closette\'s Max Altitude challenge motivated a lot of learning about KSP physics!

My hunch for flight plans is:

[list type=decimal]

[li]Lock ASAS, start engines and throttle to 25%[/li]

[li]At takeoff, turn hard to KSP2 heading Edit: Or do a takeoff loop to head 270[/li]

[li]Set pitch at 45 degrees, throttle sufficient to climb at 120-160m/s (see Closette\'s thread)[/li]

[li]At 7000m pulse ASAS and let the nose sink down, throttling down to 1.2 notches[/li]

[li]Cruise at the fastest speed you can, starting from 10,500m and flying according to two rules:[/li]

[li]Hold altitude level. When speed increases, climb slightly by adjusting trim (<5m/s)[/li]

[li]If speed begins to hold steady (or worse, decrease), level off with trim.[/li]

[li]Cut engines and glide when 70km from KSC2, try to just barely clear the mountain![/li]

[li]Glide with plane nose just barely below horizon.[/li]

[keptin]

[list type=decimal]

[li]Set pitch at 45 degrees, throttle sufficient to climb at 120-160m/s (see Closette\'s thread)[/li]

I like your flight plan better and this bit especially stands out. If it\'s anything like real world physics, quickly pushing to high altitude should save more fuel in the long run. The whole 'efficiency' thing on the engines weirds me out how it\'s so efficient at near ground level--I wonder if there\'s documentation on this somewhere showing the actual calculations and what\'s going on.

[SBaL]

Dang...

Just made a trip using nothing more than ~240kg of fuel. (Plane is made for longer flights, so i still had like 660kg of fuel left).

But ofc, it flipped over during the landing and most of it exploded.

So now I\'m of again with a similar plane, but it has a longer wingspan and I\'ve dropped the 'flying' drop tank (which never needed to be dropped during my failed flight).

Fingers crossed. =P

---Edit---

Made it.

Had some troubles with the plane suddenly starting to drop down from the sky and jump up and down for no apparent reason 15-20min into flight. So I had to try a few times with different configurations before it started to behave propperly.

Took an hour, so I doubt I\'ll try to improve that some time soon.

And this time I used 342,7kg of fuel.

But still, I made it.

Guess I\'ll include the craft as well for anyone who\'s interested.