Land on Laythe and get back to Kerbin KSC with a stock rocket.

[ocf81]

I can't find a thread with this challenge, so I thought I'd put it up here.

Title basically says it all:

- Get to Laythe from KSC

- Land on it

- Get back to Kerbin and land near KSC.

The rules:

-Stock parts only. (no automation or custom parts whatsoever)

-You can use any kind of trajectory.

3 categories:

1: Fist to attain

2: Lowest total trip time

3: Cheapest ride

-10x bonus for landing a 3 man capsule

Edited September 24, 2012 by ocf81

[KD3]

I already did this but it was a few days ago and I ended the mission. So I have no proof

[ocf81]

Can you post a picture of the rocket you used? (Or a .craft file)

[antbin]

I have a 3-kerbal lander that can take off from Laythe (thanks to persistence file edit) and make it back to Kerbin. Now I just have to figure out how to get 47 tons into Laythe orbit.

EDIT:

Well, that took a bit of time and 450 tons of rocket, but at least I'm out of the atmosphere. This should have enough delta-V to make Jool, as long as I nail the transfer orbit and aerobrake.

Also: Mechjeb, deal with it. My computer lags (see missing altimeter) and an all-manual flight will be a good follow-up challenge...

Edited September 27, 2012 by antbin

[antbin]

Nobody else is trying this challenge? It's kicking my ass lemme tell you.

If I can figure out aerobraking, this might just work...

[Koschei]

Use MechJeb's Landing Autopilot when you are approaching, it will give you your orbit after aerobraking.

[DEADBEEF]

Use MechJeb's Landing Autopilot when you are approaching, it will give you your orbit after aerobraking.

The OP specifically states no autopilots.

But yeah, pretty silly rule IMO, especially since the challenge (at least for a three man) requires you to pilot a 500+ ton craft into LKO.

[Bluejayek]

I have a 1400 ton launcher that I can manually pilot into LKO. It iosnt pretty, but it works; delivers a payloadf of about 160-170 tons into LKO. If I can adjust that payload to be a lander, I might be able to complete this.

I haven't been to Laythe yet though. What is its surface gravity/atmosphere like compared to kerbin?

[DEADBEEF]

Slightly less.

[antbin]

Got there, now to land and get home... Time to go outside get some sun.

Edited September 29, 2012 by antbin

[Androsynth]

Here's the maiden flight of the KSS Androsynth II. It uses 103 FL-T400 fuel tanks and 6 Rockomax BACC Solid Fuel Boosters to get a single Kerman to Laythe and back. The return voyage took a little detour, so I'm not even going to mention the total flight time. It's not a 3-man craft, so I originally wasn't going to post it anywhere, but I saw the challenge and figured I'd take part.

<iframe class="imgur-album" width="100%" height="550" frameborder="0" src="http://imgur.com/a/aR902/embed"></iframe>

[antbin]

What do you mean, you weren't going to post because it's a 1-kerb capsule? What's wrong with that? Good work!

What was the flight plan? Any aerobraking? Did you intercept / depart Laythe directly, or via Jool?

I still haven't succeeded in flying the return mission - lining up Laythe, Jool, and Kerbin for a Oberth-assist transfer orbit is... tricky.

[Androsynth]

What do you mean, you weren't going to post because it's a 1-kerb capsule? What's wrong with that? Good work!

What was the flight plan? Any aerobraking? Did you intercept / depart Laythe directly, or via Jool?

I still haven't succeeded in flying the return mission - lining up Laythe, Jool, and Kerbin for a Oberth-assist transfer orbit is... tricky.

I just figured, since the 3-man pod is 5x as massive, that that's going to be the real achievement. I'm fairly certain I wouldn't be able to lug one of those off of Laythe, not with any design I've ever created. Thanks though!

The flight plan was just a straight burn from Kerbin to Jool, using the 7 nuclear engines that the first stages are able to deposit into orbit. No slingshots or anything fancy, just conserving momentum from my orbit and using it to assist with reaching escape velocity. Those nuclear engines are heavy, and 7 may seem like overkill to a lot of people, but they're critical during the Kerbin ascent stages as well. I keep those puppies firing from the moment of launch until their columns start to detach ten minutes later, and they only operate at low fuel efficiency for the first 10 seconds or so. I realize the trip to Jool could've been done with just 1, but it would've put me to sleep moving that much payload with a single engine, and a rocket with a sleeping pilot isn't worth anything.

I use some last minute tweaking to directly intercept Laythe. I'm going pretty fast relative to Laythe at this point, so I aerobrake around 21,000m above its surface and then circularize around 80,000m. There are still two stacks of fuel tanks (unassociated with the lander) left at this point, so there's a decent amount of fuel to maneuver onto a path that gives you the landing site you're looking for.

Landing involves deploying two of the smaller class of parachutes. Those keep the craft upright and slow it down considerably, but it's still a powered landing, with 4 jet engiens and the one nuclear still engaged. I'd disable the nuclear at this point if that were an option, since the jet engines would be sufficient on their own, and would use much less fuel. Still, there's fuel to spare for the trip home, too, so after the landing you can actually buzz around the atmosphere quite a bit before heading up to around 10km and kicking in the two aerospikes.

The only thing that gets back into orbit is generally the capsule, 1 tank, and the nuclear engine. If you choose to skip flying around inside the atmosphere, you may also have about 400 extra fuel and the two aerospikes, but you won't need them. Getting home was just another straight burn, setting up my position around Laythe so that I'll be thrown away from Jool in the direction of Laythe's orbit around it, and waiting for Laythe's position around Jool to reach a point where I'll be thrown from Jool in the opposite direction of Jool's orbit. This path took me straight home with about a third of a tank to spare, allowing me to do some final adjustments and land pretty much right at the space center.

I will say that getting back from Jool is very time sensitive as to Kerbin's location in the solar system. You can head out and realize you've missed your window for an intercept by about six months. For this, I lowered my apoapsis and eventually found a point where I could achieve a rendezvous with very little additional fuel expended.

[Androsynth]

Thinking about it now, it would make more sense to circularize at a much higher altitude above Laythe. I'd spend a lot less fuel adjusting my course to hit my desired landing zone, no? Also descending to the planet would require lower delta-V. Maybe next time I'll try circularizing at whatever apoapsis the aerobrake happens to give me - this generally tends to be high.

[antbin]

Yeah, good thinking - adjusting your Laythe inclination would be much cheaper at high altitude. And inclination is super important with landing targets as small as Laythe's!

However, if I'm not mistaken, reducing your periapsis to land would be more expensive from a high circular orbit.

So Androsynth, you did a direct Laythe intercept both ways! I have been making my mission much more complicated by trying to do Jool aerobraking on the trip out, and gravity slingshotting on the way back. Scott Manley says this should save fuel, but I haven't done the math to figure out how much, and if the added hassle is worth it.

Edited October 1, 2012 by antbin

[Markus Reese]

Well, from my experience, the jool departure does require some special timing to maximize. What I (didn't calculate) found is that if you leave the moon while it is past orbital alignment between jool and kerbin kerbin in a retrograde path, it will have a higher apo/peri ratio. This will cut you closer to jool. When you hit peri, Give it full burn for maximum apo motion. No number, not even sure if I am 100% correct since I have only done by feel, but burning at peri does have a maximum effect on apo. If you leave laythe pro or retro, either way you will have a similar apo. If your orbit is more eliptical, it should be easier to increase your apo at peri. If not, it still is cooler to burn while closer to your orbital body. Remember to always ask yourself this number 1 question first:

What would Jeb do?

[Peppe]

Nobody else is trying this challenge? It's kicking my ass lemme tell you.

If I can figure out aerobraking, this might just work...

How do you get aerospikes on the tri-coupler?

Half the time I can't get the spikes to attach to fuel tanks and have to place a tank a few times and try the spikes again. Did not think it was possible to get them directly on the coupler.

[antbin]

How do you get aerospikes on the tri-coupler?

The aerospike engine has known bugs, but you can work around them. I used an dummy RCS tank to trick the VAB into making the aerospike attachable.

[A Fat Pokemon]

I don't see whats so hard about this you can easily land a rocket in the water and take off again if you don;t reach any land, I've already done this a few times

[etchasketch]

Here is my entry:

http://imgur.com/a/dgyF2

I dont know how long it took. The mission clock was saying 846 days when I got back, but I was hanging around Kerbin for a long time with three of these ships before convoying off to Jool.

Unfortunately I only started screenshots once on Laythe, and was too stressed to take more while taking off. The interplanetary stage got me all the way into Laythe atmosphere, and two parachutes and a small engine burst got me onto Laythe with almost full tanks and two solid rocket boosters.

The launch from Laythe was hard, and I only just crawled into orbit with the nuclear engine and about 1000L left.

I got home by burning escape velocity out of Laythe, then burning retrograde from Jool to get a close approach to Jool (150km), then burning escape velocity from Jool, then waiting until out of Jool SOI and burning retrograde for home. Certainly not the most efficient route, as I didnt wait for anything to line up. Good news for repeat missions, should have plenty to get home once off Laythe.

I tried to land near KSC, but I had only 10L left and couldn't be bothered constantly reloading to get reentry just right. So points off there.

Points gained back by completely stock 0.17 (no mechjeb) and 3-kerb capsule.

I will post the craft file later, but it has about 320 parts I think.

[antbin]

Here is my entry

Etchasketch, nicely done! I like your lander's "wide stance", very useful on Laythe. SRBs are a good idea too (much lighter than a pair of aerospikes).

Are the 3-1m adapters on the lander fuel tanks a nod to aesthetics? They're just extra weight, no?

Also, when did you lose the members of your convoy, if you don't mind me asking?

[etchasketch]

Etchasketch, nicely done! I like your lander's "wide stance", very useful on Laythe. SRBs are a good idea too (much lighter than a pair of aerospikes).

Are the 3-1m adapters on the lander fuel tanks a nod to aesthetics? They're just extra weight, no?

Also, when did you lose the members of your convoy, if you don't mind me asking?

Thanks.

The "wide stance" was adopted after numerous failed landings on Duna due to the centre of gravity being so high with nuclear engines. The extra weight it adds is just part of doing business in space.

Personally, I'm not sold on the SRBs, I just threw them on there out of frustration with other landers failing to make orbit. Since they are the first to go on takeoff, it doesnt matter how heavy they are, but something is needed to get everything out of the atmosphere quickly. I might experiment with more aerospikes, or more (bigger) SRBs.

The adapers are mostly for looks, but they also shift the centre of thrust down a bit. Also part of the "wide stance" requirement I guess. As for the extra weight, its nothing compared to the fuel weight.

The other members of my colony are happily orbiting Laythe right now. They were not as successful at launch as this one, and so they will bide their time before attempting landings as they are very low on fuel in the interplanetary stage, and takeoff pretty much requires almost no fuel use on landing (parachutes).

Running three missions at a time really keeps you on your toes tho, since by the time you get orbiting around Jool with one, the others may have been crashed or ejected into deep space days ago.

[etchasketch]

Here is the craft file:

https://docs.google.com/open?id=0Bymod7ge4lGYM1dJRDJaeTlrY2M

I changed the first stage to use less parts (30 less at 282) but it's still pretty volatile. I have it sitting on the VAB pad instead of using clamps because I cant get clamps to stop destroying everything. If anyone has tips for that, let me know.

There are 15 stages, most are for takeoff from Laythe. You can move them around while in flight to optionally deploy parachutes or discard landing gear.

Don't use full throttle on takeoff. Also, there's no ASAS

If you get into orbit with the last booster stage full then there's lots of fuel to get to Laythe (with some aerobraking in Jool and Laythe itself).

Keep the interplanetary stage on until you're just about to land, then discard it and pop parachutes. The legs are quite sturdy, and should be able to take most landings (warranty not implied).

Have fun!

[antbin]

Whew, finally made it back, with the help of MechJeb. I'm amazed that you guys are flying this manually. Dang! I have no idea how I'd do the 3 aerobrake/capture maneuvers without help. Had 30L of fuel to spare, after a KSC targeted landing.

Screenshots are uploading, for now I'm writing down my mission plan for the next try at this...

Return album (with lots of orbital planning) here

Edited October 2, 2012 by antbin

[Androsynth]

Heheh. I not only flew it manually, I also didn't bring a SAS module of any kind. I always liked to skip the extra weight, and it gives me good incentive to try to keep the craft stable. My first attempt at putting my lander on Laythe involved a powered landing, with no SAS, no parachutes, and only jet engines for thrust. The latency on the throttle for jet engines made it almost comic. I had to ask my girlfriend to leave the room after the fourth failed attempt, because it was getting embarrassing.