Duna.

[KvickFlygarn87]

What is the best setup for a transfer stage? I'm thinking orange tank, quad adaptor, four nukes.

Is the transfer to Duna anything like a Mun transfer?

Aerocapture or not?

Major noob question, I burn RAD+ to increas periapsis with MJ. Where is RAD+?

Will four small lander engines (I think they're called LV-909) be enough to land, or should i take help from a chute?

[Orbiter]

This is an interesting topic, and I am sure that every player has their own specific methods for doing this task. An orange tank with four nukes should do it, though that may be a bit overkill. You can aerocapture, though the burn is a bit different than a trans-munar injection. In order to burn Rad+, I believe that you point directly up (blue side). The engines for lander depends on what twr you get, though chutes always help. I hope this was helpful!

[regex]

It really depends on the payload. I've used a single LV-45, a Skipper, nukes, whatever to get to Duna. The delta-V needed for a transfer stage is quite low so you can use higher TWR engine combinations if desired.

[Awaras]

Yeah, if you do it right, you can get from LKO to Duna orbit with around 1000 dV. Unless you are sending a huge payload, an orange tank is a bit of an overkill.

[Crown]

Maybe you could build a lander and then post a picture here. I am sure you will get a lot of opinions about the best design.

The "best" transfer stage can get you to Duna and back. Depending on your lander weight the power of the transfer stage differs a lot.

A 32m³ fuel tank might be too heavy to get it in a transfer orbit in reasonable time (with a lander). Maybe it is possible to use a more powerful stage to get it in a transfer orbit and then use the nuclear engines. This all of course depends on the lander's weight.

The transfer to Duna is more like a transfer from Mun to Minmus, than like a LKO-Mun transfer. I don't know if it resembles the difficulty, but it might be a good practice.

Yes, like Orbiter said, parachutes always help descending on Duna. It helps reducing your fuel cost. There's a nice thread about parachutes.

[Danger2007]

Depends on the size of load, I think.

I'm taking quite a big load: 12+ tonnes of Ioncross Oxygen tanks, some living space, plus the lander. So I had an orange tank, 3 nukes with FLT 800s to hold them on the side.

I got there no trouble and into orbit without aerobraking. I think I should get back but I'd like to leave the transfer unit in orbit around Kerbin for re-fuel and I'm not sure I'll have enough for that.

But for something entirely stock an orange tank seems to be more than enough.

Here's some disscussion on a lander. I'm trying to stick with a single Poodle.

http://forum.kerbalspaceprogram.com/showthread.php/48103-Sanity-Check-Duna-Lander

[thescientist]

Depends on the size of load, I think.

I'm taking quite a big load: 12+ tonnes of Ioncross Oxygen tanks, some living space, plus the lander. So I had an orange tank, 3 nukes with FLT 800s to hold them on the side.

I got there no trouble and into orbit without aerobraking. I think I should get back but I'd like to leave the transfer unit in orbit around Kerbin for re-fuel and I'm not sure I'll have enough for that.

But for something entirely stock an orange tank seems to be more than enough.

Here's some disscussion on a lander. I'm trying to stick with a single Poodle.

http://forum.kerbalspaceprogram.com/showthread.php/48103-Sanity-Check-Duna-Lander

12 tons? Aren't them a little too much?

[esinohio]

When trying to figure out your DeltaV requirements I've found that the cheat sheets available in these forums are a big help. You can find a great thread here that has a nice DeltaV map as well as a few links to transfer window calculators. This might make planning your Duna mission much easier! Good luck! Be sure to post some pictures over in the Fan Works thread so we can follow your successes!

DeltaV map here : http://forum.kerbalspaceprogram.com/showthread.php/41652-A-more-accurate-delta-v-map

[capi3101]

Okay...so the question is a transfer stage to Duna with a twelve tonne payload.

Assuming you want the transfer stage to get you there and put you in orbit, and do it both ways, it'll need just shy of 2500 m/s of delta-V to do the job (according to the wiki's delta-V map).

You want to use four nuke engines and a quad adapter for propulsion; that's fine - it'll add 9.2 tonnes to your stage's dead mass. So that brings that up to 21.2 tonnes.

Isp is 800 of course.

So, work Tsiolkovsky backwards...

dV=ln(M/Md)*Isp*Go,

therefore 2500 = ln((M+21.2)/(Md+21.2))*800*9.81

therefore 0.318552 = ln((M+21.2)/(Md+21.2))

therefore e^0.318552 = (M+21.2)/(Md+21.2)

therefore 1.375136 = (M+21.2)/(Md+21.2)

therefore 1.375136(Md+21.2) = (M+21.2)

therefore 1.375136Md+29.15288 = M+21.2

therefore M = 1.375136Md + 7.952879, and compare that to tanks.

The dry mass of an orange tank is 4 tonnes. Plug that in...

(1.375136*4) + 7.952879 = 13.45342

The wet mass of an orange tank is 36 tonnes. This is greater than 13.45342 - therefore the orange tank actually provides too much fuel.

It turns out that your transfer stage could do the job with as little as an X200-16 and X200-8 tank combo. (Dry mass 1.5 tonne, wet mass 13.5 tonnes, equation comes out to 10.01558). The -16 by itself wouldn't be enough by about a third of a tonne of fuel, though if you could refuel it from some other source for the transfer back (such as a detachable lander from your payload), it'd be worth considering.

Why worry about going with more than enough fuel? If you don't need that much fuel, you don't have to lift that much fuel into orbit to begin with. Helps out your booster...

Other questions....the transfer is closer to a Minmus transfer than a Mun transfer in that there is an inclination change, but it isn't a big one. Usually a <50 m/s burn will do the trick.

Definitely aerocapture but you're going to have to be careful about it - 12,500 m over the surface is (in my experience anyway) an optimal aerobraking distance. If that goes to 10,000, you're going in - so be careful when setting it up.

Take chutes. Take multiple chutes. And expect to burn a little bit with the chutes deployed. Drogues might also be useful if you can pack them on.

Never worked with MechJeb before, but on the maneuver nodes, I assume RAD+ is the equivalent of radial outward, so that's the little blue ball with the legs sticking out from the perimeter (and radial inward has got the legs sticking in from the perimeter, naturally).

Edited September 6, 2013 by capi3101

[KvickFlygarn87]

Thankyou!!

Also, what wizard of a man does those calculations?

[Specialist290]

Also, what wizard of a man does those calculations?

If you're willing to learn a bit and already understand a little math up through high-school algebra, the "wizard of a man" can be you yourself!

"Delta-v" is simply an abbreviated way of saying "change in velocity." When people talk about a rocket "having delta-v," what they're saying is that, given certain values for engine efficiency and the ratio of fuel mass to total mass, their rocket engines can perform enough burns to change their velocity by a given amount in any direction before it runs out of fuel. If you had a rocket with 1000 m/s of delta-v standing still in a perfect vacuum with no other forces acting on it and you burned it continuously until it ran out of fuel, at the end of that burn it would be traveling in the direction you pointed it at a velocity of 1000 m/s. If you were to somehow magically refuel the tanks, flip it around, and burn the engines against the direction of travel, your rocket would come back to a standstill (relative to its initial starting position).

As I usually do, I'm going to highly advise reading three pages over at Atomic Rockets if you're interested in further details about how delta-v works, since the author tries to break it down into layman's terms so that anyone can understand it. You can also get data on the game's stock parts over at the wiki if you want to try a few practical exercises yourself if you want to run the equations yourself (which I'd highly recommend you try at least a couple times; doing the math yourself and changing the numbers to see what happens helped me to understand what was going on, at the very least).

As for the other calculations you'll have to do, a good delta-v chart should give you a good idea on how much delta-v you'll need for any given mission on average (assuming optimal conditions), but if you still want to calculate things yourself, there are tons of resources located in the Drawing Board (link in my sig) that can help you with constructing rockets and planning missions. I'd highly recommend taking a look at some of those.

[capi3101]

I believe both the proper term and the answer to your question is a "steely-eyed missile man"...

Let's just say I've been at this a while, and I had to figure out how to work things backwards for a Duna challenge where you aren't allowed to use nukes (well, you're allowed, but it costs points if you do...). My own payload there was about 45 tonnes all told (CSM + DEM + Rovers); the transfer stage would up doubling that...and then the trick was building a three stage booster that could lift it sans asparagus (again, conditions of the challenge).

[capi3101]

You know what? Depending on your piloting skills, I might suggest going with at least an X200-32 tank anyway. The delta-V maps assume the best case scenario, and if you're like me when it comes to piloting, chances are that you never wind up with the best case...

[Crown]

Also, what wizard of a man does those calculations?

Me.

I do them.

[SRV Ron]

This will place a small probe on Duna. I have since redesigned the probe for better landing stability since it can tip over so easily upon touchdown. Parachutes help to stabilize for landing but rockets are still needed to bring the touchdown speed under 4 m/sec.

[Crush]

When I do interplanetary missions I usually use drop-tanks (many small fuel-tanks which can be detached instead of one large one). You usually have quite large time-windows for burns on interplanetary missions, so you can take the time to check your tanks and drop those which are empty. My favorite design is one FL-T800 surrounded by six FL-T400 linked by fuel-ducts in three groups of two and connected by radial decouplers. The capacity is equal to one X200-32, but it is more mass-efficient to drop the empty tanks on the way.