[0.17 Stock] Laythe Irradiator (3-kerb Laythe return capable)

[antbin]

The Laythe Irradiator G

This 550 ton, 190 part, 16 stage behemoth will take a skilled pilot (or a clumsy hack with MechJeb) to the surface of Laythe, and back too (in theory)...

It is made up of four main stages:

1. A six-engined, twin asparagus-stalk ascent stack.
   
2. An interplanetary tug stack (with 6400L of fuel, 3 NERVAs, and an RCS tank for intercept-tweaking).
   
3. A parachute-equipped atmospheric lander that can withstand 8m/s of lithobraking. The lander is capable of reorbiting on Laythe, Duna, and small moons. Warranty void on Eve or Moho.
   
4. An interplanetary recovery stage (with 800L of fuel and a by now very battered NERVA).
   

This album shows a flight plan to Laythe, and this album shows the return phases.

1. Launch to 80 km Kerbin orbit, about 6 degrees before your Jool intercept. Better early than late, and you need time for 1 boosting orbit.
   
2. A bit before the correct escape angle (check your protractor!) burn prograde to boost your orbit up to a 6-hour ellipse.
   
3. 5-1/2 hours later, as you approach your Kerbin Periapsis a second time, burn prograde out to intercept Jool's orbit.
   
4. On the way, adjust your Jool orbit inclination, and hope to rendezvous.
   
5. 75% of the way there, adjust your Jool intercept some more, to aerobrake and (hopefully) put yourself on the same plane and orbital direction as Laythe. You want to hit Jool on the outside of its orbit.
   
6. Aerobrake through Jool to drop your orbit to ~23,000km, just higher than Laythe.
   
7. The ship doesn't have enough fuel to circularize at Laythe orbit, so just boost your Jool Periapsis up to 400km-ish and orbit eccentrically until Laythe intercepts you.
   
8. Adjust your Laythe intercept to try and orbit the equator.
   
9. Aerobrake through Laythe to drop your orbit to 60-80km. Circularize.
   

1. Retroburn when you think you'll hit an island (I recommend the island at -160 Longitude, on the Jool terminator, prograde side. Flat-ish, nice view of Jool floating in space and easier to time your return launch.).
   
2. From here in you have some fuel margin for course corrections, but not much. Drop the interplanetary tug engines and fuel tanks once they run out (but before landing!)
   
3. Once you're deep in the atmosphere and on course, point the lander retrograde and pop the chutes. Don't waste fuel retrobraking.
   
4. White-knuckle it to 500m when the chutes fully open. Check that nothing fell off.
   
5. You must retroburn just before landing. The lander will bounce at 8m/s, explode at 10. On steep slopes (pretty much all of Laythe) you had better land gently or the lander legs will pogo you downhill.
   
6. Congrats! Stretch your legs after 250 days in space
   
7. Wait a few months to launch. Kerbin should be +- 2 degrees to alignment (it's a small target!). Laythe must be at 5 o'clock relative to Jool's prograde orbit. Laythe orbits once every 2 degrees Kerbin alignment, so you don't have a wide window! Better late than early.
   
8. Launch and discard the chutes and lander legs if you haven't already
   
9. Circularize a 90 degree heading, 60km orbit.
   

1. If you didn't take off from the recommended island, you have to wait till just past the orbit-prograde side of Laythe. Just after Jool fully comes over the horizon, burn to escape Laythe retrograde/backwards to make a close (140km) pass with Jool. Don't hit the atmosphere!
   
2. On your Jool pass, as you get about 3 minutes to Periapsis, burn prograde to escape from Jool orbit heading exactly (?) retrograde to its orbit (this is why waiting for Laythe to be at 5-oclock is crucial!)
   
3. Keep burning until you're intercepting Kerbin orbit
   
4. On the way, adjust your inclination and hope to intercept. If not, well, hope you brought lunch.
   
5. If you get intercept, just hit Kerbin. That's enough, pig.
   

Upgrade to the deluxe F model, equipped with MechJeb, Kerbal Engineer, and Protractor plugins (recommended for interplanetary survival).

As the revision number shows, unplanned features are being removed all the time - let me know how it flies for you (and be light on the controls from 16,000-30,000m)...

Edited October 9, 2012 by antbin

[Nate072]

It's not the best looking rocket, but it works excellently! Thanks

[Cydonia]

A bit hacked together but awesome. Only change I made was neatening up the Pod's connection to the rest of the ship with an upside down adaptor.

[jonathan_92]

Geeze, all that just to get to laythe? What did you do, aim your rocket straight for Jool and fire?! A lightly modified nuclear duna lander would do the job! (which is pretty much a lightly modified mun lander) Still, I love me a big can o boom!! Must have been quite a challenge! Great work!!

As a hint for the future, Aerobraking around Jool can save you a TON (or literally several tons) of fuel. Then use laythe's atmo to aerobrake summore! I managed to do it and just barely hit a small land mass along the equator. Rovers are a lot of fun on the surface

Edited October 1, 2012 by jonathan_92

[antbin]

Thanks for the comments - did those with good computers / more than 2fps on launch find the rocket controllable? I have to use Mechjeb on ascent because my lag is so bad. The last 'asparagus' stage (the one with the fins) had a tendency to twist the rocket into uncontrollable spinning, before I added the last set of struts.

Agreed about the looks needing a bit of cleaning up, Nate & Cydonia... I was trying to keep the weight down to a bare minimum, to have a chance of doing the "get to Laythe and return" challenge. Still haven't managed to fly it all in one try, though.

Geeze, all that just to get to laythe?

Hey hey, this thing can get 46 tons of 95%-fueled atmospheric lander to the Laythe surface! All that is to get back to Kerbin.

Edited October 1, 2012 by antbin

[Androsynth]

Hey Antbin, it seems like both versions include modded parts. Would you mind uploading the stock version?

[antbin]

it seems like both versions include modded parts.

Oh dang, sorry! I accidentally left MechJeb on the "G" version!

I've removed it (with a text editor mind you), so please let me know if the .craft file works now! If not, I'll remove it properly from the VAB when I get home.

Edited October 1, 2012 by antbin
Oops, I left MechJeb on!

[jonathan_92]

I think with Aerobraking and gravity assists you could make a lander/return vehicle with 20-30 tons. It's gravity is similar to Duna no? Just remember to spam your hull with parachutes and struts on the parachutes so that you use as little fuel for landing as possible. Your transfer stage is going to have to be the biggun' though. You'll use up a lot of fuel trying not to crash, or fly off into interstellar space if you get your aerobraking wrong. But still not as much as if you just burn retro to capture. Also, doing your burns to change your encounter perapsis way ahead of time saves tons of fuel. (set your conic patch draw limit to like 3-5 , and draw mode to 3 so that you can figure this out in advance.) Oh, and making your orbits pro-grade helps too. Sounds like a lot, but my first Jool probe was a great learning experience, the forums help a lot too!

You're doing good using those nuclear engines though! However, I think you could probably 86 the aerospikes and their fuel tanks to drop your weight. Nuclear engines do pretty well in thin atmo and low gravity. Could be wrong, you'll have to check the specific impulse.

[Androsynth]

The updated craft file works great. Oh man, antbin, you've outdone yourself. This rocket is unlike anything I've seen before. I can't believe you got the 3-man pod there and back. That maneuver where you graze Jool's atmosphere on the return trip, that blew my mind! Very nice work.

[antbin]

Oh man, antbin, you've outdone yourself.

ohstopityou.jpg

Seriously though, I'm envying etchasketch's lower part count. I'm not done with this, I'm going to try and design a ship that my computer can fly at more than 2fps...

[Androsynth]

My KSP is telling me that etchasketch's part count stands at 282, to your 187 on the G model. Yours also uses a LOT less fuel. Am I missing something? Also, I had issues with the parachutes breaking off the command pod upon final descent to Kerbin. I was probably going to fast when I deployed them or something, although I've had this issue in the past, but only when the chutes are attached at an angle. Did you run into trouble with this at all?

Edited October 3, 2012 by Androsynth

[antbin]

I had issues with the parachutes breaking off the command pod upon final descent to Kerbin.

Whoops, that's a bug. Nope, never had that problem (but to be fair I've only returned once). Is it on first or second opening? Not sure how to fix it, besides using 1 strut.

Re: parts, you are right... I guess I was looking at the lander only. He uses 3x1600L tanks which is worse for staging but saves 6-8 parts.

[Androsynth]

Actually, it wasn't the "parachute part" that broke off, it was the parachute itself, which simply disappeared. I think it has to do with the angle of the chute relative to the part, perhaps an attempt to simulate the cord being cut from rubbing against the rim, or I don't know what.

[antbin]

Ah! I have had that problem a few times, I agree that it seems like a 'cord fraying on craft' kind of thing, but I think it has more to do with quick reversals of chute direction. It usually happens to me if my craft is tumbling with the chutes open, for example on the atmospheric lander I sometimes lose 2 of 8 (horizontally mounted) chutes before the craft stabilizes.

[Androsynth]

That seems to make sense. I wonder if one of the developers can shed any light on this behavior.

[antbin]

I wonder if one of the developers can shed any light on this behavior.

I think it's intentional - for example, on a chutes + powered landing, if you're not Mechjeb (like me) and overthrust, you can accidentally start climbing... at which point all your chutes disappear/vanish and you had better be able to power it all the way down!