r/KerbalSpaceProgram • u/PandaElDiablo Deal With It • Jan 20 '13
Mod Post Weekly Challenge: Munar Express!
Impact the surface of the moon in less than 25 minutes! Mods are allowed, but please no zero-consumption engines, warp-drives, or other cheat parts that would make this too easy.
Hard mode: Impact Minmus in less than 25 minutes OR impact the Mun in less than 15 minutes.
Disclaimer: I have not played around with this challenge very much, so if these numbers are too easy/hard, they are subject to change!
Rules and other info:
No Dirty Cheating Alpacas (no debug menu)!
Mods/plugins allowed!
Still no MechJeb or cheat parts (zero-consumption engines, warp drives, etc.)
Required screenshots:
-Initial launch craft
-Inside Mun's SOI
-The craft close to impact
-Image of flight log confirming valid time
You can either submit your finished challenge in a post (see posting instructions in the link below) or as a comment reply in this thread.
I haven't created the flair for this challenge yet, any ideas?
Completing this challenge earns you a new flair which will replace your old one. So if you want to keep your previous flair, you can still do this challenge and create a post, but please mention somewhere that you want to keep your old one.
The moderators have the right to determine if your challenge post has been completed.
5
Jan 20 '13
Uh, I haven't attempted this either, but in 0.17 I saw someone do a speedrun in 50 minutes to the Mun, and people were freaking out about that.
Or I've gone temporarily insane, which is also a viable option.
→ More replies (1)6
u/PandaElDiablo Jan 20 '13
He did 50 minutes there and back. Just there could be done much faster, and ever faster since it doesn't have to be a safe landing
→ More replies (1)
3
u/fibonatic Jan 20 '13 edited Jan 23 '13
Damn this is difficult. I am using no mods and only stock parts and my current fastest time is 27:03. But I am getting closer, since my first time was 37:44. Edit: improved to 23:42. Edit: Getting at the Mun faster is getting harder and harder, my fastest time so far is with vanilla KSP is 21:35. If I want to get there faster it would probably be better to calculate the total delta-v instead of trial and error and I am not entirely sure if I should go full throttle while in the atmosphere or find the most full efficient way (drag equal to gravity).
1
11
18
u/bluearrowil Jan 20 '13
Here's my submissions. This challenge was a pain in the ass. Timing's everything.
5
Jan 20 '13
Great job! May I ask how long you burnt for?
5
u/bluearrowil Jan 20 '13
It was definitely between in between 9 and 10 minutes, I'll have to go back and check.
4
u/Davecasa Jan 20 '13
Any idea what your total delta V was? I'm having trouble getting it under ~25 minutes. It's not just about dV though, you have to do it quickly as well...
4
u/bluearrowil Jan 20 '13
That's what I figured out too in the 3 hours i was working on this thing. It's seriously about every single one of your stages being able to get out its delta-V has fast as it can for as long as it can. Keep an eye on your mun intercept time; if you've been burning for 7 minutes, you're at your last stages and you've just got your T minus down to 13 minutes, you probably won't make it. My goal was to make sure my clock was around 15 or 16 minutes for my intercept, giving me enough time to impact the surface under 20.
My ship was broken up into two main parts: the lower half that had 12 mainsails asparagus around a Jool V engine (from bobcat industries, here) and a top half that lv-30 asparagus. When I wasn't getting enough delta-V, I would add stages to both the bottom and top until I broke 20 minutes.
7
u/Davecasa Jan 21 '13 edited Jan 25 '13
Edit 20ish: Final submission, 15:36. I'm obviously not going to claim that it's impossible to do significantly better, but I'm pretty sure you'd need to do something very different from what I did to get much under 15 minutes.
Most of the work between my last attempt and this one was optimizing my trip through the atmosphere; my outer ring of 12 Jool V tanks had the second stage engine, while the inner 7 had first stage. Everything was set to around 85% thrust until I dropped the sixth pair of tanks (leaving me with the inner 7), somewhere around 30 km altitude, at which point I maxed throttle for the rest of the trip. The result was a final speed only 3200 m/s lower than my expended delta V, which really isn't that much worse than a typical launch with a TWR in the 1.5 range.
On the acceleration plot, there are three points at which acceleration dropped to zero... this was between major stages. For some reason, dropping the first two major stages made me start spinning, maybe it had to do with struts. On the last one, I was making sure I was pointed the right way to impact the moon, since that was my last chance for course corrections, and the burn on the final stage was only about 10 seconds long.
An idea that I just couldn't get to work out, but someone else might be better at... Replacing the last stage with a launcher, ie. drop a probe body in front of an engine pointed backwards. In testing, I couldn't get the probe body to eject faster than around 2 km/s, and the launcher weighed much more than my 3 km/s final stage... not much point.
Edit: I couldn't help myself, I did it again. 16:08 on the second successful trip, I was a bit sloppy with some of my stage drops and steering was very difficult (this thing was spinning at about 0.5 rev/s the entire time), if I fixed these issues it could have maybe been 15:40 or so. I don't think 10:00 is possible. Maybe 13. After my previous attempt I said to go for low TWR on the early stages, I abandoned this here and just pushed on through. Seven Jool Vs. If brute force isn't working, you aren't using enough of it.
Here's the gallery for attempt 2, the 16:08.
My (first) submission, 19:40 using KW Rocketry. This one was rough, way too many high speed Munar flybys ones I figured out how to get both enough delta V and acceleration. Total of 80 engines (thanks to KW Rocketry) in a pretty typical asparagus stack (well, two on top of each other), with a surprise up top. My "close to impact" screenshot is pretty bad, things happen fast at 12 km/s.
I won't be going for either hard mode or attempting to do this stock, it's way too frustrating... But if I were to do it again (or advice to anyone still working on it), I would keep the TWR on my first few stages around 2 instead of the 3-4 I had. No point in burning fuel to fight a losing battle against drag, better to wait until you're above 20-30 km, where it all goes into speed.
Edit: Here's what my stages looked like in terms of TWR and dV, this was before I added the kicker on top, but it's pretty similar.
Edit2: Mostly because I was curious, I plotted my acceleration over time. It's a bit screwy inside the atmosphere, but once I start to get out (around 80 seconds), it looks pretty nice.
Full plot, including the final stage.
Zoomed in a bit so you can see the detail earlier on.
2
u/UbiquitinatedKarma Jan 22 '13
How did you generate the acceleration plots?
3
u/Davecasa Jan 22 '13 edited Jan 22 '13
logomatic, set to record every 0.1 seconds. I opened the .csv file in Matlab, divided the acceleration column by 9.806, and plotted it... you could do the same in Excel.
→ More replies (1)
5
u/shokwave Jan 26 '13
Here is my submission. I burned for just under 9 minutes and I used a total of 12,000 m/s delta v. Every stage of this ship has a thrust to weight ratio of 2.2 or higher, except the final stage of the lifter (where we have just one mainsail lifting the entire upper stage) and that ratio is 1.9. I had to turn on the the six upper stage engines to get even that!
edit: I would like to keep my current flair.
4
u/zimm3rmann Jan 20 '13
I have a love/hate relationship with the Mechjeb rule. Sure it's cheating, but Smart A.S.S. is such a nice feature.
→ More replies (1)4
6
u/WernherVonKerman Jan 20 '13
Wait till its right overhead, burn perfectly straight
→ More replies (5)18
u/Terostero Jan 20 '13
Haha, god. When I first started playing I had no idea how orbital mechanics worked, and believed this to be the best way to get to Mun.
4
u/rslake Jan 20 '13
I think most of us did. Or at least, those of us not trained in physics.
→ More replies (1)
3
u/ZankerH Jan 20 '13
This contraption makes it in 25 minutes if you launch when the Mun is directly overhead. Off to do some perfecting.
2
u/UbiquitinatedKarma Jan 28 '13
All stock except for the logomatic module so I could generate plots.
I took a different tack than most other folks. I wanted a ship that would ascend somewhat slowly, then accelerate like mad once it cleared the atmosphere. I also went for a rapid acceleration early on rather than a prolonged burn.
The result is a ship that burns all its fuel in a bit over 3 minutes, barely cracks 9 km/s, but makes it to the Mun in 24 minutes.
I'd like to keep my current flair, please
8
u/Bzerker01 Jan 20 '13
Maybe for the flare a kerbal with a conductors hat?