The Efficient Airplane Challenge

[ralanboyle]

I enjoyed @Klapaucius's Inefficient Airplane Challenge but it made me feel dirty. So I've turned it upside down. 

Get from the runway to the Island airfield burning as little fuel as possible. 

There will be two leaderboards. 

1. Overall Fuel Used. 

2. Fuel Used / Take Off Mass. 

Scoring

1. Any fuel you take with you will count as used. So only take what you need. 

2. Give me a shot of your ship in the SPH or on the runway stopped with a view of the fuel on board. 

3. For Leaderboard 2, I also need its mass to be in the shot.

The Rules: 

1. Your craft must be Kerbaled and Command Chairs are not allowed. Use a Command Pod. 

2. It must use a stock engine (non-electric) as its sole source of propulsion. No glitch/kraken/ladder drives. You can use trubo props, but you must attach propellers to the stock nodes and not use offset. 

3. Don't catapult your Kerbal (there's another challenge for that).  That being said, you can expend parts as needed and I won't give you a hard time if you break something on landing. In fact, as long as your kerbal survives, I'll count it.  See rule 6 regarding Leaderboard 2. 

4. For the purposes of this challenge I'll count any dry land on the island as acceptable, and I'll count "landing" as touching down. So, if it rolls into the water after landing, I'll give it to you. As long as Jeb survives.  

5. No bailing out. Your pilot must remain in the Command Module until touchdown. 

6. For Leaderboard 2: Due to mass calculation, you must carry all parts to the island. Losing parts on "landing" is acceptable. 

7. Enjoy

Leaderboard 1 Turbo Prop: 

@OHara 0.6

 

Leaderboard 1 Jet: 

@swjr-swis 1.65

@camacju  1.7

@ralanboyle 2.2

@ColdJ 4

 

Leaderboard 2 Jet:

@ralanboyle 0.00050

@18Watt 0.0008

@Klapaucius 0.0011

@camacju 0.0014

@ColdJ 0.00287

 

Leaderboard 2 Turboprop: 

@ralanboyle 0.00017

@OHara 0.00020

Edited May 15, 2021 by ralanboyle

[camacju]

Are turboshafts allowed?

[ralanboyle]

20 minutes ago, camacju said:

Are turboshafts allowed?

Sure. If they unbalance the score then I'll give them their own leaderboard.  

[camacju]

@ralanboyle Here's a submission without a turboshaft. It uses a Juno engine and a drag occluded fairing.

The general flight profile is to get to just under Mach 1 to avoid any transonic drag losses then cut the engine and cruise the rest of the way to the island airfield. I didn't get the timing quite right -  you'll see I had quite a bit of speed excess at the airfield, meaning I boosted too long.

Craft in VAB. It weighs 639 kg and has 3.6 units of liquid fuel.

On runway, with 3.6 units of fuel loaded

Boosting up to just under Mach 1

Engine cut - glides the rest of the way to the airfield

Pulling up to maintain speed

Detaching the fairing, deploying chute

Landed - 1.06 units of fuel used

 

Edit - I completely missed the requirement that there are no command seats allowed. Guess I'll redo this with a command pod

Edited May 10, 2021 by camacju

[camacju]

Ok, new submission with command pod:

In VAB, mass 1117 kg

On runway, 5.4 units of fuel loaded

Boost ended

Boost was just short of the airfield so I did a second boost. Probably not the most efficient way to go

Fairing and parachute deployed

Landed with 3.04 units of fuel left, 2.36 units of fuel used, and no parts broken.

I think some possible improvements would be:

-Instead of a boost to Mach 1, cruise for a bit at a lower speed and have a bit more wing area to reduce energy lost to drag - maybe?

-Figure out how to boost for less fuel - better takeoff profile, etc

However, if this challenge were to be repurposed for a longer run, then the optimal flight profile would change significantly. Maybe have Dessert Airfield / Baikerbanur (for non-DLC friendly) as well as Island Airfield destinations

[ralanboyle]

Alrighty @camacju; 

As you know, your first submission is disqualified due to the Command Chair. 

Your second entry is great.

It earns 5.4 on the first leaderboard. Remember Scoring rule 1. All fuel you take with you counts.

It earns  0.0048 on the second leaderboard. 

Edited May 10, 2021 by ralanboyle

[ralanboyle]

Alright, 

For some competition, I did a run. 

It uses 2.2 units of fuel and weighs 1546kg. 

That's a leaderboeard 2 score of 0.0014. 

 

[18Watt]

Howdy @ralanboyle!  I have an entry for leaderboard 2, although it won't make the top slot.  Takeoff weight is 101,360kg (101.360t), and was loaded with 240 units of LF.  Should give me a score in Category #2 of 0.0024.

Screenshots:

Spoiler

Here's the entry in the hangar.  Two fuel tanks with 120u LF each.  Needed a lot of wing..

To get the weight up, I added ore tanks.  As you can see, I left one empty.  I could have done better by adding more weight, but I still don't think I'd beat your score.  Also, I had to use a lot of struts to hold the ore tanks in place.  Otherwise, they would shake loose on even a gentle landing, taking a lot of the plane with them as they exploded.

Sitting on the runway, ready for takeoff.  Or am I?  Oops, forgot to close the belly doors.

The plane flies great, at this weight takes off at ~80m/s no problem.

I'm climbing here, but in level flight at 1,500m altitude I was getting ~110m/s.

Parked at the island.  I was able to land at ~75m/s, so stopping was no problem.

If I manage to beat the high score for Category #2 I'll post again.  By the way, my game is 100% stock, with BG and MH expansion packs.  

[18Watt]

@ralanboyle, Whelp, that didn't take as long as I thought it would.  I think you can put me at the top of Category #2.  Takeoff weight of 102,379kg (102.379t..), with a fuel load of 120u LF.  That gives me a score of .0012!  There was about a teaspoonful of fuel left when I landed, but I made it!

Screenshots:

Spoiler

Same plane, with a single big jet engine this time.  I adjusted the ore load for a takeoff mass of 102.379t.

Basically it's the same plane though.

On KSC runway, 120u LF.  Hope it'll be enough!

Struggling.  Not much fuel left.

Made it!  On early attempts, the engine flamed-out on final approach.  I would have counted those attempts, because technically I made it to the runway, but on those attempts I had rotten landings which damaged the plane.  Embarrassing.  This time I pulled off a decent landing, and still had fuel in the tanks.

I am frankly surprised that I was able to do better with a jet than turbo-props.  

Also, a design note:  I originally planned to make the fuselage out of Ore Tanks.  Sadly, when I launched it, the loaded Ore Tanks were not able to hold themselves together, the plane self-destructed as soon as it loaded.

[18Watt]

On 5/9/2021 at 9:13 PM, camacju said:

Maybe have Dessert Airfield / Baikerbanur (for non-DLC friendly) as well as Island Airfield destinations

I like this idea.  

[ralanboyle]

5 hours ago, 18Watt said:

I am frankly surprised that I was able to do better with a jet than turbo-props.

I have found jets to always been more efficient than props in KSP. I'd be interested to see someone prove me wrong.

Also, I am glad you went for a heavy plane. Theoretically the most efficient plane for leaderboard 2 should be enormous.  Now, I get to try again...

Edited May 12, 2021 by ralanboyle

[18Watt]

1 hour ago, ralanboyle said:

Now, I get to try again...

I suspect you and @camacju will be able to knock me off the top if you want.  One suggestion if you’re interested would be to tuck a small ore tank in there- surely camacju can fit just one more thing in the coffee can? Might end up needing a few more drops of fuel.  I’m amazed at how much you can do with just a few units of fuel.

[camacju]

Coffee can planes just won't be as efficient as a Goliath powered plane, because the Goliath is larger but has higher specific impulse.

The ideal plane for fuel/mass would probably be something like:

Single Goliath powered, engine is occluded and a shock cone is used for drag purposes instead
As many fairing occluded parts as possible to reduce drag
Big wings

While the ideal plane for raw fuel consumption would probably be something similar to my earlier design but with bigger wings and a better flight profile.

Edited May 13, 2021 by camacju

[camacju]

Ok, here's a quick new submission. I added more basic fins and reduced the initial fuel load to 2.1 units, but left the craft otherwise unchanged. (This is to leave room for later improvement)

In VAB. 2.1 units of fuel, 1188 kg - score of 0.0017

Boost is done, throttling way down to cruise at about Mach 0.5 for the rest of the way. You can see that most of the fuel is used here

Cruising further - I might have been able to cut the engine here actually, but I wanted to be sure of making it to the airfield. I definitely could have launched with 1.9 units of fuel however

Engine cut - I have a lot more energy than I need here

Parachute deployed

Landed

[camacju]

After some ill fated design changes, I managed to get Jeb to the island airfield on just 1700 mL of fuel.

1184 kg start mass, 1.7 liters of fuel - score is 0.0014

Boost to 110 m/s - this is the point where I can maintain level flight at a -1 degree pitch, which minimizes drag and thus minimizes thrust needed. I keep the throttle at about 5-6% for the rest of the fllight

Engine flames out at this point so I point horizontal to maximize lift to drag ratio and thus glide distance

I'm barely able to glide to the airfield at which point I deploy the parachute just like normal. However I come in a lot lower this time because of the reduced fuel

Landed and no parts broken

Without a pretty major design change, I probably won't be able to improve at all on this design. However I am thinking of some potential changes to this craft. Mainly I want to reduce mass as much as possible. This will reduce the amount of fuel I use for takeoff and for the initial boost, as well as reducing wing area which will cut drag. I can't really think of any other way to improve this.

The benefit of this mass reduction is apparent in the command chair craft that I mistakenly tried to enter - it used significantly less fuel than this craft even though it had a much less optimized flight profile

Edited May 13, 2021 by camacju

[OHara]

On 5/10/2021 at 2:49 AM, ralanboyle said:

If [turboshafts] unbalance the score then I'll give them their own leaderboard.  

The Breaking  Ground propellers allow a way to make perpetual motion machines (bug tracker link) by offsetting the propeller blades to be closer to the rotation axis.   If we limit the props to their default placement, though, turboprops have similar fuel efficiency to jets --- they just get that efficiency at lower speeds.

My unimaginatively-named 'single engine propeller' plane on KerbalX  launching at 2.292 t with 1.2 units (6kg) of fuel can reach the island runway.  0.52 units per tonne.

As per the contest rules, I wheelbarrowed on landing and rolled into the ditch. 

Edited May 13, 2021 by OHara
2.18t of the craft survived the trip off the runway

[swjr-swis]

Entering the MinLF-165, a single-Juno jet to transport one kerbal in a command pod from the KSC runway to the Island, for (1) 1.65 units of LF, scoring (2) 0.0011 on efficiency.

 

 

Spoiler

1.65 units of LF in the tank before take off, and 1508t take off weight, means an efficiency  score of just under 0.0011.

We ditch the landing gear as soon as we can, to save another bit of fuel and drag.

Making the most out of our gilde, and we want to flare to get rid of our speed just before making land.

Well, we only needed the pod (and Jeb) to survive...

 

Full album: https://imgur.com/a/iMZzJeq

Craft file: https://kerbalx.com/swjr-swis/MinLF-165

[camacju]

Here's another craft operating on mostly the same design I had before, but stripped down as much as possible. Inflatable airlocks aren't the most comfy, especially when they're deflated with Jeb inside them, but they are really good for fuel efficiency.

In VAB. 1.3 units of fuel remaining, just above the turboshaft entry, with potential to go down even further. 722 kg mass - this won't win any mass efficiency awards but I'm not going for that.

Airlock is extended on runway

Jeb gets out of a conveniently placed rover and then the airlock is retracted with him in it, so it can fit in the fairing. Kerbals must be very flexible

Lower weight means less wing area, and thus less drag + thrust at a faster cruise speed - great for efficiency

Engine cut with 0.24 fuel remaining - 1.06 fuel actually used (equal to my command chair entry!), and it's possible that it might be pushed below 1 fuel

Parachute isn't the most efficient option but it's certainly the easiest

Landed

Edited May 13, 2021 by camacju

[Conric005]

Hmmm, I have a plane made from a solid rocket booster I made around a year ago. I wonder if I can tweak the design to shed weight/fuel...

[18Watt]

@ralanboyle, I see @swjr-swis knocked me off the leaderboard for Category 2.  Temporarily..

I have improved my big lifter for Leaderboard #2.  Takeoff mass 122,900kg (122.9t), with 100u LF.  That's a score of 0.0008.  Should put me back at the top of Leaderboard #2.  Probably only briefly...

Screenshots:

Spoiler

I think this is about as far as I'm going to be able to take this challenge.  Similar to previous designs, except with a 2.5m fuselage.  Lots of small Ore Tanks to get the mass up, and 3 pairs of wings.  One big jet engine.  And 100 units of LF.  Total mass: 122.900t.

Sitting on the runway with 100 units of LF.  The plane handles poorly on the ground, I haven't sorted out the squirrely landing gear yet.  I was able to wrestle it into the air, so didn't worry about ground handling.

Made it to the island on 100u LF.  The plane will land at 70-80m/s, but for some reason I keep landing with way too much speed, crossed the threshold on this one at ~125m/s!  The brakes are red-hot after this one.

Fairing deployed to show the guts.  All the ore tanks need to be strutted, otherwise they come loose and become explodey.  I wanted to use the big Ore Tanks, but the 2.5m fairing would not play nice with them.  There's a MKI cockpit to hold Jeb, otherwise it's just wings and ore tanks.  And lots of struts.

The big jet engine is occluded, so I added 2 Shock-Cones to the fuel tanks.  The two Shock-Cones are adequate at 100m/s, but they don't feed enough air during takeoff at slow speeds.  So, I added a couple of radial intakes too.  The engine is still a tad air-starved at very slow speeds, but is able to reach takeoff speed about the time it reaches the end of the runway.

I'm not sure if I really need 3 sets of wings.  It worked..   I had to strut the wings as well, otherwise they had a tendency to break off during loading.  

By the way, drag is almost completely irrelevant on this one.  My cruise speed was ~140m/s, too slow for drag to be a huge factor.

I chose the MKI cockpit because it seemed like it would be very crash-worthy.  Just in case.  I normally try really hard to land airplanes in one piece, but I had a feeling this one was going to be close..

[swjr-swis]

7 hours ago, camacju said:

Jeb gets out of a conveniently placed rover and then the airlock is retracted with him in it, so it can fit in the fairing.

(How are you retracting the airlock with a kerbal inside? The option disappears from the PAW, and a set action group doesn't work at that point.)

Never mind... just noticed the 'deploy limit' can be added to a translation axis.

 

12 hours ago, OHara said:

launching at 2.292 t with 1.2 units

Kudos. The KSP props still entirely elude me. I seem to need at least six of those blades on that same engine to even get enough speed for take off, on a lighter plane, and it burns through its LF before even being over water. All the while the plane is fighting my controls like it's possessed.

 

Edited May 13, 2021 by swjr-swis
ah... deploy limit

[ralanboyle]

Congratulations everyone for your entries today! Due to the close race, please include 5 decimal places in #2 scores. 

Congratulations to @OHara for holding the current top score in both leaderboards. Let's try to match min with a jet, if more people start entering prop planes and widening the gap, I'll create another leaderboard for them. I am surprised by this efficiency. Good work. 

@swjr-swis, great run and great plane. Unfortunately, it does not qualify for #2 because of dropping its landing gear. 

@camacju, I like the "outside the box" thinking but your kerbal does not remain inside a Command Pod and therefore violates rule 5 and the spirit of the challenge. 

Edited May 14, 2021 by ralanboyle

[swjr-swis]

33 minutes ago, ralanboyle said:

@swjr-swis, great run and great plane. Unfortunately, it does not qualify for #2 because of dropping its landing gear. 

Hmm ok, that rule got added while I was busy creating/flying/uploading the entry. Makes sense though.

 

45 minutes ago, ralanboyle said:

if more people start entering prop planes and widening the gap, I'll create another leaderboard for them. I am surprised by this efficiency.

I'm not surprised, props should be more fuel efficient. I did start one to give OHara a bit of direct competition, but I just can't make those props work properly. There's some clue I'm missing about making them produce the thrust they should be capable of, and KSP does nothing to explain what.

[ralanboyle]

Proving that bigger is better I put 30 units of fuel in a 59,094kg airplane and hucked it over to the island. #2 score is 0.00050. 

 

[camacju]

On 5/9/2021 at 8:14 PM, ralanboyle said:

1. Your craft must be Kerbaled and Command Chairs are not allowed. 

This is what you said. There wasn't any specification that it needed to be a command pod, just not a command chair. Airlock is not a command chair

On 5/9/2021 at 8:14 PM, ralanboyle said:

5. No bailing out. Your pilot must remain in the Command Module until touchdown. 

Oh, is this what you meant? The pilot remained in the command module from takeoff to touchdown. Surface operations before takeoff were never mentioned either, nor did the pilot bail out of anything.

Edit: I mean, I could just launch with a command pod bolted on, transfer the pilot, and detach the command pod. That would satisfy the spirit of the "no bailing out" rule while adding absolutely no change to the mission at all

Edited May 14, 2021 by camacju