Career Duna Landing help

[Chronin]

Greetings to everyone who happens to stumble upon this thread.

I come to you with a problem today: I need to get to Duna in career mode (0.23) and I can't seem to design a ship good enough for it. I've been to Mun, Minmus and around Kerbol many times, and I can get there pretty easily. I want to go to Duna before I go to Eve because of Eve's very high gravity, and so I think that Duna will probably be easier. Let me just put my tech tree here so you guys can see what science I have unlocked.

I'd say I have a decent number of things unlocked, and, from what I've seen, should be enough to get me to Duna. Unfortunately, I am not that great of a ship builder (I suck) and cannot get a good design. My lander isn't bad, but the rest of the ship...

Anyways, there are a couple things that I would like to be able to have/do with this ship. This is a list of things I would like from most important to least important:

1) Must be able to get to Duna and back to Kerbin

2) If possible, I would like it to be manned with a crew of 1 or 2 kerbals

3) While I do have docking ports unlocked, I have not messed around with them yet, so I would probably mess something up if I try and dock two ships together in orbit

4) Reasonable room for errors, I'm an okay pilot, but I can't get to Mun and Minmus with only the Start science node.

5) As you can see, I don't have the amazingly efficient nuclear engines, but I can probably unlock them if necessary.

6) Any science tools I can bring along are very welcome.

If you have a ship that meets at least a few of these requirements, I would be delighted to see them, if only to get some ideas.

Thanks for reading

-Chronin

[Brun]

If you really try to scrape up every little bit of science on Mun and Minmus, you should be able to unlock most of the tech tree without leaving the Kerbin system - or so I've heard. I definitely didn't do it that way on my latest career save, so I'm unable to say for sure if that's possible.

I don't have a stock ship that can make that trip, but I can tell you now that having the nuclear engines will make your life considerably easier, particularly in the "room for error" department.

EDIT: Also I'm assuming you plan to adopt a Mothership+Lander model for this mission, since that's probably the easiest way to go for interplanetary missions like this. If you're uncomfortable with rendezvous and docking, you'll need to make a relatively powerful lifter that can carry both your mothership and your lander into Kerbin's orbit in one launch.

EDIT 2: Actually, if you went Mothership+Lander you'd still need to do a rendezvous and dock (on the return leg). So you're talking a pretty massive craft, especially since nukes are pretty worthless for atmospheric flight.

Edited April 19, 2014 by Brun

[technion]

Whilst I'm sure it can be done, it'll be a much more pleasant trip if you unlock the nuclear engine. From LKO, one FL-T800 tank with an LV-N can manage a Duna flyby, which of course will unlock a bit more to build a lander.

[Rokker]

Landing on Eve can be, and usually is much easier, even with the gravity. This is because it has an atmosphere thick enough for 'chutes to actually work in. On Duna your choices are add infinity + 1 parachutes, a powered landing, or a combination of parachutes and powered landing. The major problem is the return portion. As shown by many videos, especially Scott Manley's Eve series, taking off from Eve is absurdly hard.

Edited April 19, 2014 by Rokker

[Brun]

Landing on Eve can, and usually is much easier, even with the gravity. This is because it has an atmosphere thick enough for 'chutes to actually work in. On Duna your choices are add infinity + 1 parachutes, a powered landing, or a combination of parachutes and powered landing.

I definitely wouldn't recommend going to Eve. He's specifically planning a return mission and given that a return from Eve is pretty much the single most challenging thing you can do in KSP it's probably not a good thing to attempt with only half the tech tree unlocked.

[Rokker]

I definitely wouldn't recommend going to Eve. He's specifically planning a return mission and given that a return from Eve is pretty much the single most challenging thing you can do in KSP it's probably not a good thing to attempt with only half the tech tree unlocked.

Yeah, I noticed that part after commenting and edited my post.

[Claw]

Landing on Eve can, and usually is much easier, even with the gravity. This is because it has an atmosphere thick enough for 'chutes to actually work in. On Duna your choices are add infinity + 1 parachutes, a powered landing, or a combination of parachutes and powered landing.

Landing on Eve, yes. But if you want your kerbals to return it's a lot more effort. (EDIT: Ninjas... )

3) While I do have docking ports unlocked, I have not messed around with them yet, so I would probably mess something up if I try and dock two ships together in orbit

I know this does not answer your request for a ship that meets your design goals. However, I would recommend that you try and practice rendezvous and docking. It opens up a lot more design choices for you and would make building a lander-return vehicle a lot easier. I feel it also gives me confidence to know that if I mess things up, I can still meet up and rescue the guys.

Edited April 19, 2014 by Claw

[Rokker]

I know this does not answer your request for a ship that meets your design goals. However, I would recommend that you try and practice rendezvous and docking. It opens up a lot more design choices for you and would make building a lander-return vehicle a lot easier. I feel it also gives me confidence to know that if I mess things up, I can still meet up and rescue the guys.

Indeed, docking isn't necessarily required for Duna missions but it is extremely helpful.

[Claw]

Here is one idea that someone posted on another thread in this very sub-forum. It is a design that uses mods, but you can perhaps get some ideas.

http://forum.kerbalspaceprogram.com/threads/76853-Duna-lander-with-FAR?p=1097549&viewfull=1#post1097549

[LethalDose]

Point of clarification: When you say "Get to Duna", do you mean Duna *Orbit* or Duna *Surface*?

[Specialist290]

Quick rule of thumb: Almost any rocket that can make it into orbit around the Mun generally also has enough delta-v to make a transfer to Duna (especially if it has a little bit of reserve fuel for corrections and unforseen circumstances), and Duna's atmosphere, though thin, can still allow you to aerocapture into orbit if you aim for a 10-12km periapsis on your approach. A lander that can land on and return from the Mun by itself can also generally make a parachute-assisted landing on Duna and return to orbit (again, especially if it already has a fuel reserve). The main thing you'll have to account for after that is having the delta-v to transfer back to Kerbin, though again, considering you can aerobrake and reenter at your destination, this still ends up being a relatively cheap expense on the delta-v budget by comparison.

[Brun]

The main thing you'll have to account for after that is having the delta-v to transfer back to Kerbin, though again, considering you can aerobrake and reenter at your destination, this still ends up being a relatively cheap expense on the delta-v budget by comparison.

He can also (theoretically) get gravity assists in both directions (from Ike and Mun), and maximize those by thrusting at his Ike-ar/Munar periapses. He could shave off 2km/s (500 m/s for each gravity assist) if he managed to catch both Ike and Mun in the right place, but that's getting very very lucky.

[Claw]

I would presume you want to land on Duna, since you mentioned lander.

Anyway, The Spacecraft Exchange is also a great place to find example craft. : http://forum.kerbalspaceprogram.com/forums/20-The-Spacecraft-Exchange

Here is a thread with quite a few stock and modded transfer/lander craft for the Mun/Minmus/Duna. : http://forum.kerbalspaceprogram.com/threads/37745-Showcase-Post-your-Moon-Planet-Landers-Thread-Lander-building-guide

[Chronin]

Brun

I was actually planning to send a giant mothership into orbit around Duna, send the lander down and return to kerbin with the lander alone. I have the equivalent of five FL-T800 on my lander, and I'm fairly confident it can get back to kerbin alone.

Rokker

The problem with Eve is that my lander is too heavy to get off of its surface, while I should have enough fuel to slow myself down in Duna orbit (9 parachutes help too)

Specialist290

Is that true? Cause I can make it to the Mun and back with fuel to spare, and that's with no gravity turn (I was too lazy to do one)

You guys have been really helpful, so thanks.

Edited April 19, 2014 by Specialist290
Merging sequential posts by same user. Also, don't worry about it :)

[Brun]

Brun

I was actually planning to send a giant mothership into orbit around Duna, send the lander down and return to kerbin with the lander alone. I have the equivalent of five FL-T800 on my lander, and I'm fairly confident it can get back to kerbin alone.

You'd be surprised - regular rockets get significantly less efficient in atmospheres, so you will use up a lot more fuel just due to engine inefficiency on ascent from Duna, not to mention the extra to counteract drag.

This really would be a lot easier if you could dock with that mothership.

[Rokker]

When I have questions like this, I turn to NASA for inspiration. I usually use something that mimics either Apollo, plans for the manned Mars mission, or something in between. For example, once an Apollo moon landing mission reached orbit, it still had the 3rd stage (S-IVB-500) attached. This third stage was used to boost it into the Trans-Lunar Injection and then it was ditched (usually purposely crashed into the moon or sent to heliocentric orbit.) and the command module docked to the lunar (though you could have them pre-attached). Once they reach the destination, the service/command module would perform a orbital insertion burn. The lunar module would undock, land, do science and then (this part is very important to the story) leave an entire half of the vehicle behind to shed the weight. In your case this would include all science tools you bring along, remove the data from em and put it in the capsule. This ascent module would then redock with the command/service module which would them perform a burn to return to Earth, ditching the ascent half of the lunar module on the way after moving all collected science into the command module. Once it reached the point at which re-entry is certain, it would ditch the service module.

Now, obviously anything built like this for a Duna mission risks being too large to launch with one rocket. However, the main ideas of it remains true, namely that A)when you have fuel left over from your launch stage, you should us it, and the only 2 things that truly need to return are the people and the science. The lander, the service module, the injection stage, every single part can be expendable as long as the Kerbals and the science make it back in a capsule. Whenever there is a point at which dead weight can be dropped for a weight savings, drop it. If the lander has an empty 2m tank and a poodle on it after landing, then stick a decoupler and 1m tanks and engines on top of it. I have no craft files to give, but I hope that advice helps

tl;dr - stages everywhere and dont turn down free fuel.

You'd be surprised - regular rockets get significantly less efficient in atmospheres, so you will use up a lot more fuel just due to engine inefficiency on ascent from Duna, not to mention the extra to counteract drag.

This really would be a lot easier if you could dock with that mothership.

Honestly, the ISP of engines rises rather rapidly and in Duna's thin atmosphere, while it does have an effect, I think the effect overall is somewhat minimal

Edited April 19, 2014 by Specialist290
Merging sequential posts by same user.

[Pecan]

If you can't dock reliably there's still the option of EVA so you can leave the lander behind in space but recover the science and crew ... as long as you can rendezvous.

[Rokker]

If you can't dock reliably there's still the option of EVA so you can leave the lander behind in space but recover the science and crew ... as long as you can rendezvous.

Yup, that is a pretty good option as well. Might result in some thrown away fuel, but not a lot.

[Dave Kerbin]

I've run numbers on Duna many times and for a single kerbal mission (assuming no mods) there is only a small advantage to any kind of docking. Once you've landed on Duna the amount of delta-v you need to get into orbit and return to Kerbin can be fit into a relatively small craft. You definitely don't need nuclear engines for a mission to Duna.

Just to illustrate that nuclear engines are not required, the ship below can make a round trip from the launchpad to the surface of Duna and back (bottom portion gets it into Kerbin orbit, the 2 fuel tanks strapped to the side get it to the surface of Duna and the middle tanks get it back to Kerbin). Now this isn't the kind of design you should be aiming for right now - you should be carrying more science stuff (you don't have the small Double-C or GravMax instruments so you'll want the Science Jr and Goo containers) and you can definitely carry more fuel to make the trip safer.

Like I said, that's probably not the ship you should use. But there is a core concept to take from it which is that the portion that will return you from the surface of Duna back to Kerbin doesn't need to be big. A lander can, FL-400 tank, Rockomax 48-7S and some support equipment like solar panels and a parachute will do pretty well. You can remove the data from any experiment you run so there is no need to bring them back to Kerbin - just run them on the surface, collect the result and then abandon them when you take off.

A more realistic but maybe a bit overdone Duna expedition can be seen here. I've gone to Duna and collected nearly every scrap of science (even sent a probe to collect data from Ike) at about the same tech level as you (though I've unlocked some more science instruments). You'll note that that return craft is very close to what I described and I attached my science and other support equipment to the sides so that it could be ejected when I was done with it.

[Chronin]

Thanks for the help, this really gave me some nice ideas. Had you replied yesterday I wouldn't have used nukes, but early this morning (in America, at least, I don't know where you are) I went to Minmus and came back with around 700 science, so I know have nuclear engines and some other new parts (not enough for the GRAVMAX though). Anyway, I really like your ship, I myself can never think small. I know simple is good, I know it's more efficient, but my brain doesn't care. Problems with a ship? More Mainsail! Too many Mainsails? More boosters! Etc. etc. I really wish I could think small and simple for once...