Duna plan - any problems I should work out first?

[Dave Kerbin]

Over in my mission thread I've got my Duna plan worked out. I've never been to Duna (except an ion probe before career mode) and I'm interested in any mistakes or oversights I might have made. This will be an expensive mission risking the lives of 3 kerbals and take longer then the rest of my program combined, so I want to get it right.

Complete plan

http://forum.kerbalspaceprogram.com/threads/53159-Science-leads-to-wonderful-things?p=727072&viewfull=1#post727072

Just the plan slides

http://imgur.com/a/wxQeU

One thought is whether I am going too far with the command pod swapping between landers. While the command pod(s) will need to be seperated and returned anyway it might be safer if both landers have their own pod. It would provide a rescue option if something goes wrong on Ike (use the Duna lander as a rescue vehicle) and further my attempts to ensure that science is preserved at each step (the Ike surface samples would be preserved even if the Duna lander crashed).

Another risk is if the fuel stack on the ship (or the lander on each end) is too unstable - I only have regular sized docking ports and while I think they should be fine during the ejection burn (I can burn at 50% or 25% thrust to reduce G forces) the aerobrake at Duna seems like it might stress the craft too much. An alternative is too pack enough fuel for a thrust only capture at Duna (I know I can do it even at low thrust because I've done a thrust only capture with an ion engine).

Just a note about tech tree - I don't want any tech tree spoilers about where specific parts are. I have researched everything up until the column where nuclear engines are. It's basically a straight line, everything on the left is researched, everything on the right (nuclear engines and beyond) is not researched. I will be making at least 600 science before the Duna mission window to unlock nuclear engines and that tech in the same column that gives you seismic sensors and the last antenna.

[Kulebron]

You need 2000-2100 m/s for the lander, because apart from getting back into orbit you'll need to rendezvous, and before that to deorbit, soft land (can easily cost 200 m/s even with parachutes) and break to save parachutes too. I was descending with them at 200 m/s when they expanded and one of them tore apart the decoupler it was attached to. I landed on the side.

Also you can aerobrake with aerobraking calculator to have apoapsis at Ike's orbit and not need to burn 250 m/s for it. Saves a lot of fuel.

[Kulebron]

Here's my Duna rocket. 2 landers and the whole ship in 140 tonnes. (But I did not make a rover.) For Ike I use the small "space bicycle", a tank with 2 "saddles".

It's weight is balanced, but drag is not, so you have to countersteer in Kerbin ascent a lot.

download

[numerobis]

If you have struts -- which IIRC you should have by now -- you can tie a few from the main body of the space craft to the parachutes (in that order, you can't start on the parachute) in order to hold them on tighter during the descent.

The mission design seems ... ambitious. In particular the practice unmanned landing. If you're doing an unmanned sample return mission, go all the way for a completely unmanned mission, then come off that success (or lack thereof) with the manned mission.

[FoxKit]

For my Duna lander, I brought two of the smaller SRBs with. They have enough power to get you out of the atmosphere, so after that you only need to circularize and burn back to Kerbin which is less than 600 m/s or so of Delta-v. So if you can land on Duna with two small SRBs and a full medium tank of fuel you'll be fine. :3

Your plans seem comprehensive, but I found it actually pretty easy to go from launch to Duna and back with no refueling and no docking. Do double up on drogue shoots for your Duna landing if you have them, though; since the atmosphere is so low, you need to slow down as much as possible or you'll tear your lander apart.

Good lick!

[Dave Kerbin]

If you have struts -- which IIRC you should have by now -- you can tie a few from the main body of the space craft to the parachutes (in that order, you can't start on the parachute) in order to hold them on tighter during the descent.

The mission design seems ... ambitious. In particular the practice unmanned landing. If you're doing an unmanned sample return mission, go all the way for a completely unmanned mission, then come off that success (or lack thereof) with the manned mission.

The reason for the unmanned practice landing is that I want to minimize risk to my Kerbals (I'm playing perma-death, no reverting, somewhat serious roleplay). The Duna landing is the biggest unknown with the least margin for error in this mission - if the parachutes or engines aren't enough, or something breaks, the kerbal will fall to his death. I could do a completely unmanned mission first, but that would take almost half a year from my program. Since parachutes can be repacked in space and carrying the fuel one way in my nuclear cargo ship is relatively cheap I figured I wasn't losing much to greatly improve safety.

[capi3101]

That's a very ambitious plan you have going there; I hope you can pull it off.

About the only thing I'll caution you about is to make sure your transfer stage has plenty of juice. Unless you're using a mod like Protractor, you're probably not going to get the transfer exactly right, and you will need more delta-V than what the delta-V map shows; since this is your first trip out Duna's way, I'd humbly suggest planning for 125% the delta-V with your transfer craft.

EDIT: There's this too. Plan for a powered descent on both worlds unless you're thinking about taking a [KILLER RABBIT OF CAERBANNOG]tonne of chutes on the Duna lander. Seriously. A metric [KILLER RABBIT OF CAERBANNOG]tonne.

Edited October 24, 2013 by capi3101

[Dave Kerbin]

As for parachutes I was planning some kind of Duna mission before my career mode reset and used that calculator.

Here is the rover I was going to send with the mission:

4 Drogues

8 Radials

4 Lithobrakes to protect the wheels (you can't tell but they are off the ground, and the structure is non-rigid so it has some bounce to absorb impact)

And driving away

[Oddible]

Good god man, what have you done!? When I look at your plan, and I hear the words... "I've never been to Duna before", I just see complexity piled on top of complexity piled on top of complexity. And you know what complexity means right? Many, many possible failures. What ever happened to K.I.S.S. (keep is simple stupid!)?

Sending a probe to Duna, good idea. Sending a manned missions to Duna, awesome idea. This insanely convoluted contraption to maximize your Duna trip with so many incipient failures embedded into it... why not wait til you have a handle on interplanetary travel and some familiarity with Duna first? Send a simple one Kerbal lander and get it home safely while minimizing complexity (the name of the game in space travel, which is already inherently complex). Send something like this... see if it works, then think bigger and better...'

(BTW, I don't mean to sound discouraging, your plan sounds incredibly fun... and frustrating... but I'd want some more experience under my belt before undergoing such lunacy!)

[Specialist290]

4 Lithobrakes to protect the wheels (you can't tell but they are off the ground, and the structure is non-rigid so it has some bounce to absorb impact)

<courtesy image snip>

I just want you to know that I'm probably going to steal this idea from you for my own future interplanetary rover missions. Extremely clever!

[Mykill Metal]

Needs more struts.....