Duna Mission, Single Rocket or Assemble in orbit?

[Tyko]

I won't send kerbals on a mission longer than a few weeks without lots of elbow room - like 3-4 seats for each crew member. This necessitates bigger ships, but my conscience is clear

[Spricigo]

 

 I go along the lines of modular spacefaring system. Multiple launches are standard procedure for interplanetary missions. (  However small modules are often launched in batches.) 

[Geschosskopf]

On 6/22/2016 at 9:51 AM, AeroAviation said:

I just want your guys opinion on what the best way to build an interplanetary rocket to bring and return kerbals from the surface of another planet it. I personally would go with docking as its less hassle IMO

It really depends on what you're trying to do when you get there.  This determines the number and size of the mission payloads and the orbits they need to get into.  The more  you want to do, the more stuff you need to move, so the bigger the rocket to get it off the ground, until eventually you reach the limit of your current booster size, budget, VAB size, or engineering skills.  This usually isn't the case for Duna, however, because it's only a stone's throw further from Kerbin (in terms of transfer dV required) than Mnmus.  So for Duna, you usually have all options opens.

I myself tend to prefer using a 3rd option you didn't mention:  flotillas.  That is, a bunch of single launches each carrying its own mission payload and going to the target by itself.  Some of these will probably end up docking at the target as part of the mission.  Their are a number of advantages to using flotillas compared to a single mothership, whether that mothership is launched as 1 piece or assembled in orbit.  These are:

• All the payloads are small so use smaller lifters and transfer stages.  This reduces overall mission cost because the price of boosters doesn't increase linearly.
• Every payload can take its own best course to the target without being encumbered by the requirements of other payloads.  For example, mapping probes that will end up in polar orbits and never interact with any other part of the mission can go their own way from the get-go.
• If you want to do things on multiple bodies (say Duna and Ike), you don't have to move everything around from one to the other, which wastes fuel.  Instead, you send stuff to their own targets individually.
• You have a lot more redundancy and survivability.  A failure of payload probably won't jeopardize the whole mission, and various payloads can be mixed and matched at the target to get home or even extend capabilities that you hadn't thought of to start with.

Now, if all you want to do is flags and footprints at Duna, you don't need anything complex. and it's pretty easy to do with 1 launch.  The main decision is whether to do it "Apollo-style" or not.  By Apollo-style, I mean you have a crew transport vehicle, which is also the interplanetary transfer stage, and a separate lander.  These go out together, the lander goes down and up, the crew transfer back to the transfer vehicle, and the lander is left behind.  This requires docking.  If that's not your thing, then you come home in the upper stage of the lander without docking.

However, if you want to build a permanent colony that's self-sufficient for fuel, hit both Duna and Ike, and/or hit multiple Duna biomes, you have a fairly complex mission.  This is where you should consider doing a flotilla or assembling a mothership in orbit.

[Andem]

Assemble in orbit, with three seperate modules at most, but having two would be better. It really just comes down to what you think would be more fun though.

[adsii1970]

Assemble in orbit!

[tsotha]

 From a dV perspective a Duna shot is only a tiny bit more than a Mün mission, so if you're just going to land, plant a flag, and do some science there's no reason to build your ship in orbit beyond the entertainment value.

[Firemetal]

5 minutes ago, tsotha said:

 From a dV perspective a Duna shot is only a tiny bit more than a Mün mission, so if you're just going to land, plant a flag, and do some science there's no reason to build your ship in orbit beyond the entertainment value.

Yup. Actually you don't even need to assemble a rocket in orbit to go to Jool, and land on Tylo and return.

Also people use nukes for Duna. Why? I have a rocket that can go there and back using only 1.25 and 2.5m parts to get there and back with fuel left! It only uses , a mainsail, two twin boars, a poodle and a terrier.

Duna is quite easy imo. Although it might not be for newbies, you don't need to assemble a ship in orbit just to do a round trip to Duna and back.