Smallest Craft for Munar Landing and return.

[Krenn]

This challenge is to use the fewest possible fuel tanks and engines, in order to land a command pod on the Mun and then return it to kerbin.

Rules:

Only one RCS tank is permitted, although you may have as many RCS thrusters as you like.

you may use whichever stock components you like, and only tanks, engines, and boosters count towards your total.

All stock parts, but the landing legs mod is permitted.

Liquid engines are 2 points, fuel tanks are 2.5, and solid boosters are 1.8

The goal is to build a craft with the fewest number of points, and complete the mission.

my current record: 4 engines, 17 fuel tanks, with 12 of the tanks configured as drop-tanks. total: 50.5 points

[dashcunning]

How do you feel about crumple zones?

3 LFEs, 8 tanks.

I screwed up leaving the Mun and used more fuel then necessary. If done properly, I\'m sure you could save some fuel for a short retro burn immediately before landing (the chute gets you to ~25m/s) and have everything survive.

Edit:

A bare bones 1 LFE, 6 tanks, 2 radial decouplers, 2 fuel lines, 1 chute, command pod may be possible. But hell if I\'m gonna annoy myself trying to fly it without ASAS.

[Krenn]

How do you feel about crumple zones?

you mean sacrificing part of your craft during kerbin landing, to survive touchdown? that\'s fine.

[witeken]

I only know the smallest stock craft for orbitting kerbin and landing safely: (from highest to lowest part)

command module

fuel tank

fuel tank

fuel tank

liquid engine (the most powerfull)

[Awaras]

KSP noob here, but I just have to ask two things:

First, how exactly did you bridge the ASAS module? I can see from the staging icons that you have a fuel line connecting the center engine to the fuel tank but I can\'t figure out how you did it.

Second, what use is an ASAS in this case? As far as I understand, an ASAS does not have any stabilization properties by itself and you don\'t have any RCS, gimbaled engines or winglets for it to control...

[Krenn]

KSP noob here, but I just have to ask two things:

First, how exactly did you bridge the ASAS module? I can see from the staging icons that you have a fuel line connecting the center engine to the fuel tank but I can\'t figure out how you did it.

Second, what use is an ASAS in this case? As far as I understand, an ASAS does not have any stabilization properties by itself and you don\'t have any RCS, gimbaled engines or winglets for it to control...

ASAS has the same gryoscope as normal SAS, and weighs the same. he probably has a fuel line from the tank to the engine on the other side of the rocket.

[dashcunning]

The fuel line is hidden inside the rocket (you can zoom into parts), going from the bottom of the tank to the top of the ASAS. When possible, I like to hide fuel lines and struts inside for neatness. The only reason I put the ASAS at the bottom like that was to lower the center of gravity. Normally I place it just under the command pod, but I was having horrible luck landing on slopes (the fuel budget is so tight you don\'t have enough to hover around looking for a nice flat spot). The engine kept snapping off and I got fed up and lowered the CoG. Don\'t know if it really helps all that much, but I landed successfully first time after that. You would save 0.05 mass with the ASAS in the normal spot and not needing a fuel line, but whatever.

The ASAS is able to use the command pod forces. SAS would work, but I don\'t care for the default tuning on it. It\'s not very good and you get over-correction leading to oscillations.

And if anyone would like to try it, I can post an in-depth flight plan.

[LambdaCactus]

The fuel line is hidden inside the rocket (you can zoom into parts), going from the bottom of the tank to the top of the ASAS.

Can you clarify how you do that? So does the fuel line attach on the bottom of the fuel tank? But then what does it attach to?

And if anyone would like to try it, I can post an in-depth flight plan.

I wouldn\'t mind trying it, how tight is the tolerance on hitting the flight plan just right?

[Krenn]

And if anyone would like to try it, I can post an in-depth flight plan.

I\'d appreciate it. I\'d love to see what you consider the most efficient flight plan... I haven\'t been able to reproduce your success yet

[dashcunning]

This rocket is too small to zoom into with it\'s default placement in the VAB. Grab it by the command pod and move it left or right a bunch. Rotate your view around 90° and the rocket is now closer to (or further from) the camera. Now when you zoom (hold middle mouse and mouse up or down), you can zoom into the parts allowing you to see what is on the other side. For the fuel line, I zoomed through the ASAS from below so I could see the bottom of the tank and placed one end. I then zoomed out and placed the other end on the engine. Fuel lines connect to whatever they hit, so even though I clicked on the engine, it connected to the ASAS. The engine draws fuel from the ASAS (don\'t ask me why that works), which draws fuel through the line from the tanks.

http://dl.dropbox.com/u/50454654/Minimal%20Mk11.craft

0) Engage ASAS and throttle up to 100%

1) Stage to launch

2) @15km yaw over to 27° above the horizon on a heading of 90° and re-engage ASAS

3) When the outer tanks/boosters empty, stage to jettison them

4) Cut engine when Ap is 10,800km

5) SoI change occurs shortly after 10,000km. You should be in a hyperbolic (parabolic?) trajectory passing behind the Mun

6) Do a retro burn until Pe is 2-3km

7) At Pe, burn on a heading of 270° to remove horizontal velocity

8) Re-orientate vertically and land. Good Luck

9) Get into a 5km eastwards orbit

9a) Liftoff and head towards the horizon on a heading of 90° and burn until Ap is 5km then cut engine

9b) At Ap, burn again until Pe is 5km

9c) This doesn\'t take much and it\'s easy to overshoot and waste fuel like I did. Be careful

9d) A lower orbit would be more efficient but it\'s more fidgety and doesn\'t allow for 5x time compression. You would also need different values for 10) and 11)

10) When you pass in front of the Mun (the rocket is on the Mun\'s forwards orbital line), aim towards 40° below the horizon on a heading of 90° and engage ASAS

11) When your aim-point becomes the horizon, burn until speed is 800 m/s

12) SoI change occurs shortly after 2,000km. You should be in an elliptical orbit with Pe in or very close to the atmosphere

13) Retro burn so Pe is ~30km

14) Hopefully you are heading for land. Water landings are not survivable w/o a retro burn while land landings destroy the rocket but not the pod

15) Stage to pop chute

16) Immediately before landing, retro burn to slow to a safe landing. If you don\'t have the fuel, cross your fingers!

Notes:

This probably isn\'t 100% efficient. It\'s close though, easy to replicate, and it worked for me.

This was with 13.1. I don\'t see why it wouldn\'t work for 13.2 though.

[LambdaCactus]

Nice trick! I didn\'t realize about the zooming, I\'ll have to figure out how it works on my Mac trackpad.

Fuel lines connect to whatever they hit, so even though I clicked on the engine, it connected to the ASAS. The engine draws fuel from the ASAS (don\'t ask me why that works), which draws fuel through the line from the tanks.

I read somewhere here that the way the parts objects are modelled, the engine requests units of fuel from the part above them in the stack, and this request repeats to the next part above until the upper object says 'false: I have no fuel'. This allows the upper fuel tanks to return their fuel down the stack first. The fuel lines essentially work like jumpers so when the engine asks the ASAS, 'gimme fuel?', it responds with 'yes, I got some from above', thanks to its fuel line.

[closette]

Very nice dashcunning, I think your design and flight plan are close to bare-bones optimal. I calculate that your take-off thrust/weight ratio is about 2.2, just where you want it so that when you are up to speed you can keep the ratio just above 2 while in the atmosphere.

[Kryo]

This challenge is to use the fewest possible fuel tanks and engines, in order to land a command pod on the Mun and then return it to kerbin.

Rules:

Only one RCS tank is permitted, although you may have as many RCS thrusters as you like.

you may use whichever stock components you like, and only tanks, engines, and boosters count towards your total.

All stock parts, but the landing legs mod is permitted.

Liquid engines are 2 points, fuel tanks are 2.5, and solid boosters are 1.8

The goal is to build a craft with the fewest number of points, and complete the mission.

my current record: 4 engines, 17 fuel tanks, with 12 of the tanks configured as drop-tanks. total: 50.5 points

hmm how do you do that what you did with your fuel lines? if i build something like that, the engines will always empty the tanks on the top of them first, and afterwards the connected ones.... What am I missing?

[dashcunning]

how tight is the tolerance on hitting the flight plan just right?

I forgot to respond to this. It\'s hard to say. The one time I landed successfully on the Mun, I returned successfully. But I screwed up leaving the Mun. Don\'t know how much more fuel I would have had if I did it properly. As it was, I had essentially zero left after getting into a 51km aerobraking orbit. I was trying to save that for a landing retro burn, but aerobraking at that altitude takes forever (hence the 39 hour mission time in the final screenshot). I got impatient and said f it and used the last of my fuel next time I was at Ap. Which only lowered Pe from 51km to 28km, so hardly anything.

Room for improvement would be:

Steps 2 and 4. The current controls and instrumentation lack the precision to make significant gains there though IMO.

Step 6. The lower you can get this, the better you are. A better pilot than myself could probably come in at something ridiculous like 500m and follow the retrograde vector all the way down at 100% burn.

Step 9. Lower orbit is better.

Steps 10 and 11. The ideal burn would put you into an orbit with the Pe just barely in the atmosphere. At which point you run a script that keeps sending the increase time compression key press while you go do something else.

[RNSP]

urm...mine has 1 fuel tank and 1 engine 1 asas nd then the stock lander parts eg winglets radial decuplers...so isn that the best or what??

[LambdaCactus]

urm...mine has 1 fuel tank and 1 engine 1 asas nd then the stock lander parts eg winglets radial decuplers...so isn that the best or what??

Seriously? 1 fuel tank wouldn\'t get you out of the atmosphere, let alone to the moon and back.

[UmbralRaptor]

urm...mine has 1 fuel tank and 1 engine 1 asas nd then the stock lander parts eg winglets radial decuplers...so isn that the best or what??

Stock propulsion, not cfg-edited...

[RNSP]

ohh i thought you just meant the lander soz