Ultimate Munar Exploration Challenge

[MaxMurder]

Not sure if this has been sugessted before... but I have found that a Munar landing an return can be accoplished relitivaly easily after some practice. So I tried to complete a tougher objective and came up with a neat challange. Mostly I would like to see the types of crafts ppl build to complete it.

Objectives:

Build a craft that can...

1) fly to the mun,

2) Land in each of the five dark craters on the surface

3) return safely to Kerbin

All three objectives must be completed in a single flight (ie. go to mun, land in crater, travel to next crater, land etc.)

Extra points for:

Landing near the KSC

Completing the mission in less than 24hrs (lifesupport/oxygen limit)

Use only vanilla parts (good luck with this one)

I will be posting screens of the ship I used to complete this challenge once I am back at home!

[Darkshadow]

Perhaps I might be able to achieve it if I use a larger lifter for my Munar lander, then that should free up the 4 tanks I currently use for TMI onwards. I will let you know how I get on.

[Panichio]

I think the ultimate Munar exploration challenge would be to drop of a satellite, scientific instrument of some kind and a rover...then get back to Kerbin!

[boolybooly]

I have tried this and it is possible with stock though I failed on the fifth crater on the first shot due to running out of juice and then when I had redesigned to provide enough juice I kept on breaking the rocket on landing.

Without stock landing struts it is just very very tricky. Little bit of drift or slope and you wave bye bye to your engine.

For your entertainment.

...An Heroic Failure...

[MaxMurder]

Yes I am eagerly awaiting stock lander legs...

[boolybooly]

A Story In Pictures...

Lucky first landing sheared off the booster engines in crater one which the crew named 'Crash Crater' allowing Jeb to use the remaining booster fuel for the first ballistic hop to crater #2 thanks to Bob\'s bodacious plumbing, hence 'Plumber\'s Crater'.

Bill cooked up the ship design on the back of a kornflakes packet one day while raiding the KSC kitchens. He thought it could land on three fins stuck onto the lander stage aft drop tanks, which were meant to be retained even when the tanks were empty to use as landing gear to preserve the lunar hopper\'s engine, which you can see best in screenshot 27. So the forward drop tanks were on seperate decouplers, screenshot 19.

Jeb decided to jettison these (and the booster tanks) by putting the ship in a spin to make sure they got away from the craft without flipping over and colliding with the landing gear. This made Bill feel queasy, but he was a lot better after a fry up in crater three 'Burger Crater', where he became highly skilled in the art of flipping burgers in Munar gravity.

Then the crew took the ship over to the dark side of the Mun, making a landing in Darth Crater though the fuel situation was getting perilous Jeb decided to stick with the landing gear and fired up for the final hop.

The hopper made it to all five craters and then left Munar orbit after dropping the landing gear in 'Junkyard Crater' on the final launch. Successful insertion to Kerbin orbit allowed for an aerobraking pass and reentry close to KSC but not within sight on landing. So Grandpa Kerman had to come and get them in his fishing boat... again.

Flight time 16 hrs 36 mins all stock parts...

[MaxMurder]

wow... way to go... i doubted that this would be possible with strictly stock parts...

[boolybooly]

I have way too much time on my hands !

[Dr Zarreh]

I did something like this (landing in craters and flying above most of the moon) with a TARDIS a few days ago, sadly i took no screenshots... I think i might do it again...

[Kosmo-not]

A tardis? Is that a mod craft?

[samstarman5]

I hope a Kerbal Munar Base is on the blueprints, as it would be fun to practice launching from the Mun as we have been able to from Kerbin.

[MaxMurder]

Finally got around to re-trying this... My bro erased all my pics :\'(

My first attempt was a failure. Fuel was running very low after the final jump but Jeb insisted that he make the final landing before returning to Kerbin... They ran out of fuel at about 90m. However, the second attempt was a complete success! Also this was my first attempt at a direct acent, I usually opt for a parking orbit before a lunar transfer.

This is the ship I used...

Liftoff of the Urist class rocket!

Second stage decouples after MOI

Successful landing!

Kerbin return module blasts off from the munar surface leaving behind spent fuel tanks and landing gear

On the way home!

[boolybooly]

Nice ship Max.

I have always found it uses less fuel to go with direct ascent in KSP. I think that the lower you are when you reach escape the faster you are going and the faster you get out of the high gravity zone the less speed you lose from trying to reach orbit inside it.

You dont need to reach orbit to escape, so you dont need to spend fuel going sideways when all you want to do is go up.

What I do find though with moon shots is that I have to go up and out of the atmosphere ASAP before angling the thrust to match the apoapsis to the moon orbit, this takes a lot of fuel. When it becomes possible to use the warp on the ground without all sorts of problems then it will be even easier as you can line the up the shot for the moon so you can go straight up.

[Awaras]

Well, here is my contender for this challenge. Unfortunately, I was not able to complete the challenge because I ripped off half my \'landing gear\' winglets while trying to land in the second crater... :\'(

I managed to take off before blowing up my ship and decided to see if I have enough fuel to complete the challenge. I did this by going to each crater, slowing down the lander at 10 - 20 meters altitude and hovering there for 30 seconds, simulating a landing. I was able to fly to all 5 craters and had 2.5 tanks of fuel left for the return voyage (the center tank + 3 half full tanks). Now I just need to learn how to land more good... ;P

[thorfinn]

Very interesting challenge.

I managed to land in 4 out of 5 maria with a almost-stock ship (used two NovaPunch couplers and landing legs: engines and tanks stock) with a decidedly non-optimal route: I 'decided' to visit all the maria on the lighted side first, before going to the dark side (quotes around 'decided' because it was actually an error in reading the navball at 2nd launch). It was a good idea after all, because I flipped the vehicle in the fourth landing since I couldn\'t see a thing. And it would have had just enough fuel to launch back to Kerbin, dang it...

Will post some pix later. Will not attempt again until we get better instrumentation: landing in the dark is too much of a gamble.

Obviously, I could just wait on the ground until my destination is illuminated... but timewarp on the ground doesn\'t work either, so....

This is the vehicle anyway.

I have to thank... somebody on this forum for the idea of daisy-chained drop tanks.

[l00]

I found this challenge a bit late, but there you go!

Stock parts only.

It took more than a day as i managed to find slopes in 2 of the 5 craters, so i was low on fuel...

Landed near-ish to KSC, also because of low fuel, i was afraid to i could not correct my inclination.

Is that considered near? You decide!

[boolybooly]

Nice videos l00. Well flown.

Here is a question for moon hoppers, what is the best angle for a ballistic trajectory like the ones we do hopping between craters?

Also do you want the orbit trace to be fast and low, a circular form or high and slow? Or doesnt it make any difference?

I was thinking the lower you fly the faster you have to go and the higher you fly the more fuel you waste going up and then decelerating coming down, so I was guessing that if you want to go somewhere efficiently you should go as fast up as you go across ie 45°. But I cant prove it, its just intuitive, a guess.

If I do a little sum in my head I see this...

g=2.5

up(m/s) across(m/s) distance(m) flight time(s)

100 0 0 40

90 10 360 36

60 40 960 24

50 50 1000 20

40 60 960 16

10 90 360 4

0 100 0 0

Suggesting that a 45° initial flight trajectory is optimum. Is that right ?

[thorfinn]

45° is the best angle for constant, divergence-less gravity (ie. flat earth), and the trajectory is a parabola.

For long distances, the trajectory is an arc of ellipse, and things are not so simple. Will try to solve that problem after I finish working

[Zephram Kerman]

I haven\'t attempted this challenge (yet), but I have done a small amount of exploration hopping. What seems to work best for me is to adjust the angle based on the distance I want to go.

Each hop must end with a nearly vertical approach. So I aim to overshoot the landing spot, and then clip the arc with a horizontal burn in order to descend straight down. So for example, if I want to go just over the next ridge, I\'ll ascend at about 60 degrees. But in the case of visiting other craters, I\'ll make it more like 30 degrees or lower.

[ash73]

I\'ve managed all 5 crater landings, but sadly I ran out of fuel on the return trip and my Kerbanauts are now stuck in orbit...

(edit: completed the return trip after 2-3 more attempts; final stats updated).

[jebbe]

Sorry for bumping this again - I\'ve been trying again and again for the last two weeks, and finally succeeded as well. Unlike others, I didn\'t have the fuel to adjust for a landing really close to the KSC, just landed in the ocean somewhere south of it. It also took me more than 24 hours, but it\'s stock only.

Oh, did I mention that I hate dark side landings? I think especially for those we\'d really need a landing radar!

About the optimum angle: I\'d be very interested in that, must be possible to derive some forumla for it. As has been pointed out already, it\'s straight forward for a flat surface and constant g (45°), but on a sphere with decreasing gravity it could be hard... I\'ll look into it when I get the time.

[closette]

For those interested in the best angle for launching between points on the Mun, I have solved the equations for the lowest-energy elliptical orbit connecting any 2 points on a spherical body (neglecting the Mun\'s slow rotation).

It took a few pages of scribbling, drawing, and calculus but I\'m confident of the results.

The first plot shows that there are many possible ellipses connecting two points on the Mun, which I take to be an angle 2*phi apart, for convenience. Examples shown use locations 120 degrees apart, so phi=60 degrees or Pi/3 radians:

A family of elliptical trajectories which connect two point on the Mun located 2 phi=120 degrees apart (phi=60 degrees).

The smallest diameter ellipse has the lowest energy (since energy = -GM/diameter), and hence the lowest speed at the launch point, so with some calculus I was able to find it:

smallest/lowest energy ellipse connecting two points on the Mun 120 degrees apart (phi=60 degrees)

If you want to check, the semi-major axis a = 100 km (1+Sin(phi)) and eccentricity e = Sec(phi) - Tan(phi).

Conservation of energy gives the launch speed for this lowest-energy ellipse:

v_best = 806 m/s Sqrt{Sin(phi)/(1+Sin(phi))} - this gives 304 m/s launch speed for the example shown.

and the hard part (for me anyway) was to find the best launch angle, which after much work boiled down to a very simple relation:

angle_best = 90 degrees - phi - Arctan(Sec(phi)-Tan(phi)), which when plotted is apparently identical to...

angle_best = 45 degrees - phi/2. (Remember that the origin and target points are separated by 2*phi as measured at the Mun\'s center). So for the example above, that would be a launch angle of 45 - 60/2 = 15 degrees above horizontal. Looks about right!

This trajectory will take you to an apoapsis altitude mid-way between origin and destination of a(1+e) - R, or

apoalt_best= 100km (Sin(phi)+Cos(phi)-1). For the example above this gives 36 km, again looks about right.

This assumes impulsive launches, and neglects the Mun\'s slow rotation, and terrain.

A detailed proof will follow in a few days is attached below as a PDF.

How to use these results: Once you\'ve figured out the crater-to-crater angle (2*phi) - with a Mun map perhaps - the angle and launch speed equations above should give an efficient transfer between them. If you have a high thrust/weight vehicle, just launch it at the best angle, and boost until the ellipse intersects your destination. You can check your apoapsis altitude to see how close to optimum your 'hop' turned out.

Phew! Finally, as an exercise for the reader, what is the optimum theoretical launch angle and speed between two antipodal points on the Mun (diametrically opposite from one another), and what does the resulting path look like?

Happy hopping!

[jebbe]

@closette

These are great results, I\'m looking forward to the derivations! edit: Thanks for the pdf - it\'s really nicely presented, very enlightening!

Maybe this should also go into the howto/tutorial board, since it might help a lot of other people, too.

I\'m not posting the result to the \'exercise for the reader\', since you already told me, and I don\'t want to spoil it for others.

[SpaceGibsy]

I\'ve MADE it.. and as far as i can see the 'smallest' design jet .. http://kerbalspaceprogram.com/forum/index.php?topic=9514.msg140873#msg140873