How Do You Land On Duna and Get Back

[Rileysam10]

I have been trying to land on Duna (KSP's Mars) for a very long time, and when i say very long i mean very long. I have even set up a fully fledged base on the mun, and explored all of kerbin. I'm in career, so i cant really make a very expensive ship. My VAB is almost finished upgrading, as well as my launch pad, so no need to worry about how many parts i use. I have really been trying this for almost a year now, so some help would be appreciated. I have almost landed on duna before, but i broke up in the atmosphere and now there are about 10 pieces of debris on the planet. I would also like to safely return my kerbal, or drone, depending on if i would like to send a manned mission yet or not. I have been trying to do everything NASA style, as my space program name is IKSP, or International Kerbin Space Program. 

 

-Rileysam10

[Snark]

Hello, and welcome to the forums! 

If you're finding it difficult, you might try an unmanned probe to Duna first, just for landing practice.

If you want to do a land-and-return vehicle, one handy way to practice is to do something like this:

1. save your game
2. launch just the "lander / ascent" part of your duna ship to the launchpad
3. use the "Set Orbit" function on the debug cheat menu to put it directly into orbit of Duna
4. now practice landing it and taking off again. 
5. tweak ship as needed, repeat steps 2-4
6. once you're happy with it, load the save you made in step #1 (to undo all the cheating) and then work from there

General tip for landing on Duna:  use a combination of parachutes and engine.  The air is so thin that if you try to land on parachutes alone, you end up spamming so many parachutes that the mass just kills you; and if you try to use engines-only, that's a whole lot of dV wasted.  You definitely want to have some drogue chutes on your ship, again because of Duna's thin atmosphere-- they can deploy at lower pressures and open at higher speeds.

An example of an easy, cheap, and lightweight way to land on Duna is:

1. Put a couple of the small radial drogue chutes, plus an appropriate number (not too many) of regular chutes.
2. Set the drogues to open fairly high up (say, 4000 meters instead of the default 2500), ditto the regular chutes (say, 2000 meters instead of the regular 1000).
3. Go ahead and trigger all the chutes long before you get down to the appropriate altitude.  They'll deploy when they can.
4. The drogues slow you down some, the regular chutes slow you down further.  Now you're dropping those last couple of hundred meters to touchdown, but pretty fast (like, 20-30 meters per second).
5. Use a brief burst of rocket thrust right before touchdown to slow to a safe landing speed.

 

[Superfluous J]

For taking off from Duna, I like to do a gravity turn as if I'm taking off from Kerbin, only cut everything in half. So I want to be at 45 degrees when I'm 5km up instead of 10km, and by the time my Ap is at about 30 I'm sideways, instead of 60. I try to make sure my ascent vehicle has similar TWR as a Kerbin ascent vehicle, though that can be hard because Duna's so light.

It helps that Terriers (which are great vacuum engines but not so great in atmosphere) work okay even on the surface, due to Duna's low pressure. If your ship's small enough, you can get by with just one of those but testing is the only way to be 100% sure. Like Snark suggests with just landing, I suggest you use the debug menu to put your ship into orbit, land it, and then take off to orbit again to test the entire process before leaving home, at least the first few times you do it.

[bigcalm]

Instead of an all-in-one type vessel, consider sending several vessels around the same time.  As long as you're ok with how to rendevzous you should be fine.

* An interplanetary craft, designed to push your kerbals to and from Kerbin orbit and Duna orbit.  This will need around 4000 ms delta v (from Kerbin orbit)

* A lander - sent separately and not intended to return back to Kerbin.  It's purpose is to rendezvous with the other vessel in orbit, transfer the crew (either via EVA or docking), land on the surface, plant your flag and get back into orbit.  Your lander will need around 2500 ms delta v - half to land, half to get back into orbit.  It'll also need an additional 2000 ms delta v from kerbin orbit to get to Duna.

As snark recommends, I would also recommend adding some drogue chutes to your lander.  However, don't rely on them for safe landing -- Duna does not have a thick enough atmosphere likely to cause you problems - chutes are mainly to help you orient yourself in the right direction so you can burn your engines to avoid smashing into the ground.

Nuclear engines are fantastic for interplanetary because they're the most efficient (vacuum) engine in the game - though they can't normally be used for landing as they're not powerful enough.  Stage appropriately!

 

[archnem]

I've done quite a few Duna landings, with a few different mission architectures, everything from direct, one ship all the way missions to launching an armada of different support craft.

Duna's biggest drawback is also its biggest strength - the thin atmosphere.  I regularly use NERVs on my landers, since even on the ground the air is so thin they still get great ISP.  If this feels too cheaty to you, 909s work great as well. 

I also use parachutes - in my direct missions, the same lander that I use to land on Duna eventually returns to Kerbin. If I just use the amount of parachutes I need for Kerbin, this still will slow my craft to 20-30m/s, and I only have to use a little fuel at the end of the landing to get under 6m/s.  Also, a few airbrakes are really light-weight and help as well.

The trick w/ chutes is twofold.  First, you want tweak them in the VAB to deploy as high as possible and with as little air pressure as possible.  I usually set my drogues to 5000m, 0 pressure, and then stagger my other chutes to deploy in batches between 4000-2500m.  This keeps the chutes from ripping the craft in half by deploying all at once.

Second, the Dunar (Dunan?) atmosphere is gonna be way too thin to slow you down enough for chute deploy before you smack into the ground, even with airbrakes.  You'll need to use your engines to slow you down some before you can deploy the chutes.  How high ofc, depends on the craft in question and your TWR, the higher your TWR, the longer you can wait to burn, and the shorter the burn will be.  But the important part is, you can't count on Duna's atmosphere to slow you down like, at all.

[Stargate525]

My quick and dirty way to design a Duna lander is that if it can hit space on Kerbin using a standard ascent profile, it's got plenty of juice to make Duna. That usually overengineers the lander by quite a margin, but I prefer having surplus fuel. They make for great emergency fuel deposits in case I'm not as efficient for later missions.

[DD_bwest]

early on i always high over estimated what it would take to land and get back, i thought it would take a heck of a lot.  Over time though i realized how little you actually need.  I find the "easiest"  method to be a single launch mission that does not include orbital rendezvous.  but that could be because i really like my Tiny return pod.  The gravity is light enough, and the atmosphere thin enough that a single spark engine is all that is needed to launch from duna, and at 320 ISP its not to bad for heading home either. this tiny simple craft can get you back to kerbin from the surface of duna. its around 2300deltaV.   So if you were to build a lander with a second stage similar in design and purpose, all you have to do is land.  any extra fuel in the landing stage you can use to boost yourself up, detach and head home.  Put the science gear on the landing stage to conserve weight and pull data.     But if you dont like putting jeb in a tin can for so long its not a great method.  as for chutes, a whole bunch of drogues set to open mighty early help a lot and slow you down for your main chutes.  Use the chutes for assistance and engines for right at landing to bring your speed down to something your legs will handle.

it has a z-100 on the back you cant see, and i drained the monoprop.

[Foxster]

DD_bwest is pointing you in the right direction. 

It is extremely tempting with KSP to throw on more things or use the next size up of something. This leads to the mass of a craft ballooning, just like it does with real-life rocketry. 

You need to start with "what is the absolute minimum I need for this mission?". Then think carefully about what can be thrown away along the way, such as science experiments that can be dumped before returning. 

Here's a craft that will get a Kerbal from Kerbin to the surface of Duna and back with a mass of 23t at launch from Kerbin...

Craft file: https://www.dropbox.com/s/tzn3be8pxet1bny/Duna ion mission 5.craft?dl=0

 

Edited December 17, 2016 by Foxster

[Rileysam10]

On 12/14/2016 at 6:49 PM, Rileysam10 said:

I have been trying to land on Duna (KSP's Mars) for a very long time, and when i say very long i mean very long. I have even set up a fully fledged base on the mun, and explored all of kerbin. I'm in career, so i cant really make a very expensive ship. My VAB is almost finished upgrading, as well as my launch pad, so no need to worry about how many parts i use. I have really been trying this for almost a year now, so some help would be appreciated. I have almost landed on duna before, but i broke up in the atmosphere and now there are about 10 pieces of debris on the planet. I would also like to safely return my kerbal, or drone, depending on if i would like to send a manned mission yet or not. I have been trying to do everything NASA style, as my space program name is IKSP, or International Kerbin Space Program. 

 

-Rileysam10

Thank you for all the help! I have been sending duna missions in campaign for a while now, and the space-craft series is called Operio. Operio I was a un-manned mission and sadly failed lifting off from the launch pad, and exploded under its own wait. I later modified my craft so it wasnt so heavy. Operio II was the first unmanned mission to duna. It brought home a lot of science and funds, and with that, Operio III was the first manned mission to duna. Jeb and Bob took the mission. Luckily, Bob is a 3 star and Jeb is a 2 star. Half way to duna, the ion thrusters blew up from a bug. But it wasnt all that bad. The acceleration of the craft would hit duna anyway. I prepared for landing, but the landing gear wouldnt go out. I was getting very worried, the landing gear still didnt go out. With no landing gear, I still managed to hit softly enough that the craft didnt get damaged. I landed perfectly, and got home with enough science to create my next mission. Thank you so much for the support everybody!