Mission to Duna Tips

[theradRusssian]

I am making a mission to duna in sandbox mode.Can any of you give me tips?Thanks.

[HazelPine]

If you plan on landing by chutes, remember that the atmosphere is way thinner than Kerbin's so pack more of them. Also, to land on chutes, you should reenter at the shallowest angle possible, to maximize aerobraking on the way to land. I once landed straight from an interplanetary encounter, and I started gaining altitude after I passed periapsis, a couple hundred meter above the surface. This stops you from going downwards too fast for you chutes to slow you down.

[strigon]

I'm assuming you mean to land and then return?
If it's just getting there, it's no different than going from Kerbin to the Mun, only slightly more intensive and finicky.

For landing, don't bother with a heat shield; Duna's so small, and its atmosphere is so thin that it shouldn't be an issue. Make sure to pack a drogue chute, as there's a good chance without it you won't be able to slow down enough to deploy your main chutes, and leave some extra fuel for a powered landing - just a bit of a boost, even with a drogue and backups, parachutes are still not great on Duna. On that subject, also make sure to maximize deployment altitude, and minimize deployment pressure in the tweakables.

No real trick to takeoff, though; just keep in mind that there is an atmosphere when you build your return vessel, so don't go too overboard. Fins shouldn't really be necessary, but you might want a gimballing engine just in case.

[LordKael]

Duna is really forgiving on aerodynamics, since the atmo is so thin. As a result, you're going to get very little help from parachutes, but taking off is crazy easy. Make sure you pick a good place to land, as there are some pretty wide, relatively steep hills. 

[ag3nt108]

Pick the landing site very very carefully, nothing worse than taking out your solar panels by landing on the side of a mountain and rolling down

[KerikBalm]

yea duna has some steep slopes, aim for the lowlands to maximize your aerobraking possibilities. Prior to 1.1 it was often hard to slow down enough for chutes to safely deploy, but I think the chutes can deploy at higher speeds on Duna now. If having that problem, wings can help a lot to keep your vertical speed low as you bleed off horizontal velocity. While you could spam chutes to touch down without rockets, its a matter of diminishing returns. To reduce vertical speed to 1/2, you need to increase your chute mass by 4x. Going from a 20 m/s to 10m/s descent velocity on chutes only saves you ~10 m/s ... the fuel for a quick retroburn of 10 m/s is going to be less massive than a 4x increase in chute area. So I would stick to 1 drogue and 1 main chute (or pairs of radials)... maybe more for larger vessels.

As with many bodies in KSP, the dV required is so low that you might as well single stage it rather than carrying decouplers and multiple engines. Given the benefit of the atmosphere for landing, the increased dV for ascent still only requires a total dV just a bit more than a Munar landing.

The atmosphere is so thin than vacuum engines work very well. The LV-N works fine with an Isp over 700... and its Duna relative TWR is over 6:1.

If you want to use wings... its a very high landing speed, you should plan on a vertical landing at the end. So... a tailsitter works well:

(it had drogue chutes at the back to slow it down... and main chutes at the front to keep it vertical... unintentionally the main chutes placed with symmetry are clipping with the spotlight in this image)

Otherwise... its much harder to execute a horizontal landing:

and I recommend vertical lift-rockets and vernor thrusters to control pitch as you slow down:

Aerospikes are good for this due to their low profile, and surface attachability (the above image was from an earlier version of the plane... the twin aerospikes for horizontal thrust didn't have enough oomph for my liking, hence the skippers in later design... also note the addition of LV-Ns to make use of the wing fuel capacity)

 

Edited June 20, 2016 by KerikBalm
1.2 -> 1/2

[Scarecrow]

If you have a lander that has plenty of fuel to land on Mun and return to orbit, the same lander can be used to land on Duna and return.  You just need to add a couple of parachutes, as these will do most of the slowing down on descent, leaving virtually all of the fuel available for the ascent back to orbit.  I set the drogue chute to open at 5000m and the main chute to open at 2500m.  Together these drop my velocity to about 28 m/s so you don't need to use much engine to lower it further to a safe landing speed.

I also echo the thoughts of finding somewhere as flat as possible to land.  My lander put down on what I thought wasn't too steep a slope, but it slid quite a distance after dropping the rovers.  Goodness knows where it would have ended up if the slope had been even steeper.

Video, showing that you don't need anything to fancy to land on Duna:

 

Edited June 20, 2016 by Scarecrow

[Snark]

Moving to Gameplay Questions.

I would actually suggest NOT putting on a lot of parachutes.  Some, yet-- and definitely have some drogues, as folks have suggested. However, don't try to pack on enough parachutes to land safely with.

Instead, have just a few-- enough to slow you to under 100 m/s, but don't try to do much better than that. Then use a brief burst of thrust from your engines to slow down to safe landing speed just before touchdown.

Rationale: because the air is so thin, chutes give much less benefit per kilogram, as KerikBalm mentions. Packing enough chutes to land safely will be really heavy. The first few chutes are worth it, since their effectiveness goes with the square of your speed, but beyond that, rocket fuel is more lightweight. If you're dropping to the surface at under 100 m/s, a hundred kg of fuel will slow you more than a hundred kg of extra parachute.

Be aware that Duna's atmospheric pressure varies sharply with altitude, so it makes a LOT of difference what the surface elevation is of your landing site. Landing in the highlands is much closer to a vacuum landing than it is in the lowlands. Doesn't mean "don't go there" ..  just be prepared.

[Cornholio]

I suggest designing an Apollo style mission where you leave either your main engine structure with a docking port and probe core (so that it is not considered debris and removed from the game dependent on settings) in low orbit around Duna.  Land with the bare essentials for at least your first time just so that you can get a good feel for it.  If you use a LS mod, only bring the minimum for a landing if you plan to return to Kerbin.

As others have mentioned, and just to reiterate:  consider single stage, use drogues, but do not bring too many chutes, be prepared to power land, lander with wide base and low CoM, etc.

One thing no one has mentioned yet is a ladder.  For most bodies in the Kerbol system, you do not need one as monopropellant is enough to get a Kerbal back to their pod.  Duna's gravity IS weak enough to allow you the use of monopropellant, but it is close enough to where if you fall off of the ladder or are having trouble getting to the hatch, you may run out of monopropellant. 

Lastly, Ike is a very similar body to Duna.  Bring enough fuel or consider sending a mission there first with the first iteration of your craft as it has a bit more of a forgiving gravity, does not require chutes, and is a close interplanetary object.

GOOD LUCK!

[KerikBalm]

I would disagree that ike is similar to duna... its more similar to Mun, except with lower gravity, less craters, and larger mountains...

[Greenfire32]

My pro tip? Don't Miss.

[Mjarf]

7 hours ago, Snark said:

Moving to Gameplay Questions.

I would actually suggest NOT putting on a lot of parachutes.  Some, yet-- and definitely have some drogues, as folks have suggested. However, don't try to pack on enough parachutes to land safely with.

Instead, have just a few-- enough to slow you to under 100 m/s, but don't try to do much better than that. Then use a brief burst of thrust from your engines to slow down to safe landing speed just before touchdown.

Rationale: because the air is so thin, chutes give much less benefit per kilogram, as KerikBalm mentions. Packing enough chutes to land safely will be really heavy. The first few chutes are worth it, since their effectiveness goes with the square of your speed, but beyond that, rocket fuel is more lightweight. If you're dropping to the surface at under 100 m/s, a hundred kg of fuel will slow you more than a hundred kg of extra parachute.

Be aware that Duna's atmospheric pressure varies sharply with altitude, so it makes a LOT of difference what the surface elevation is of your landing site. Landing in the highlands is much closer to a vacuum landing than it is in the lowlands. Doesn't mean "don't go there" ..  just be prepared.

One alternative is to have parachutes in clusters mounted on decouplers so that you can get rid of the weight before launching from the surface? One thing I have noticed on my trips to Duna is that the planet seems to be jinxed. On every trip something has gone wrong or has almost gone wrong. I've nearly lost both Jeb and valentina on Duna, it's a surprisingly treacherous planet, probably because I tend to underestimate it.

[Snark]

1 hour ago, Mjarf said:

One alternative is to have parachutes in clusters mounted on decouplers so that you can get rid of the weight before launching from the surface?

Certainly you can do that (I do it with Eve all the time) ... but it's not just that the parachutes are heavy upon ascent from the surface, it's also that they're heavy just to ship them to Duna in the first place.

If you're sending a massive orbiting mothership and it's just a small lander that goes down to the surface, then the weight of the parachutes isn't such a big deal for the initial sending-to-Duna, granted.

But for me, it always comes back to that diminishing-returns thing.  The first few parachutes, which can slow you to under 100 m/s, give a lot of dV benefit for a fairly small mass investment.  Beyond that, you simply get more bang for your buck by leaving off the extra chutes and just spending a bit of fuel on retro-thrust right before landing.

One of the things I like about Duna is that there's no single "right" way to land there-- it's amenable to a lot of different techniques. 

[Mjarf]

I see your point, it's true that parachutes aren't very efficient on Duna, but I like to foolproof my crafts as much as possible, as I have the occasional brainfart when flying. I guess half the point of the forums is to share our different ways of doing things. You prefer to do things more efficiently, I tend to over-engineer everything. 

[Greenfire32]

1 minute ago, Mjarf said:

I see your point, it's true that parachutes aren't very efficient on Duna, but I like to foolproof my crafts as much as possible, as I have the occasional brainfart when flying. I guess half the point of the forums is to share our different ways of doing things. You prefer to do things more efficiently, I tend to over-engineer everything. 

I've never lost a single Kerbal due to this kind of thinking right here. Sure, it's more economical to just use fuel to slow me down, but what if I use too much getting there? What if it breaks during staging? Better pack some 'chutes just in case.

[SkippydaHippie]

I just this morning finished my first round trip to Duna. It's a nice easy system to get around in. I landed without parachutes, it was pretty easy, just remember you don't need a steep trajectory. I started my accent at about 54km and dropped my periapsis down to 20km, within the atmo but as people have stated, very thin. It'll bleed off some horizontal speed over time so I figured that was my biggest concern; the possibility of the drag dropping me faster than I'm used to in a lander like this. The net result was a nice short burn right at the end that dropped me right on the surface. I was a little alarmed at my rate of decent for just a moment but I was surprised how easy and fun a landing it turned out to be. So land at day, try to make sure it's in a flat area and you got it no sweat man.

I used chutes to land on Duna once.. that was back when I didn't know anything and barely managed to get there through sheer force and a way oversized inefficient vehicle. I built this crazy looking spider like lander, it had a sweet rover that dropped off the front of it, but besides that the thing was super shoddy... Anyways I ran out of fuel about 400 meters above the surface... still moving at like 200 m/s. I don't remember the build, some time ago... But yea, i had the chutes out on the legs, and when they deployed the craft flipped completely over on its back and the spider legs bowed out waaaaay farther than they should have been able to...used the last scrap of monoprop I had left to turn the thing halfway over and drop it right on the engine BLAMMM!! Kerbal on Duna  but man that rover was sweet. A little too sweet, I kinda drove it over a cliff...

[AbacusWizard]

For a medium-sized (and reusable) Duna-lander, I'm fond of a combination approach: two or four aerobrakes to start slowing down as soon as the atmosphere gets thick enough, a few drogue chutes to deploy as soon as it's safe to do so, and then just use the main engine to come to a complete stop once the ground starts looking close enough to be frightening. Everyone gets out, plants flags (and picks them up again, because I am not a litterbug), smiles for the camera; the scientists do science and the engineer repacks the parachutes; everyone back in, and return to orbit to rendezvous with the mothership.

[bigcalm]

A "mission to Duna" is pretty broad.

Do you want to go to Duna and land but not come back?  (4500+1600+1200 ms^-1   Δv)

Return to Kerbin? (4500+1600+1200+1200+1600 ms^-1 Δv) (assumes no aerobraking)

Visit and land on Ike too? (add ~1800 ms^-1 Δv )

Collect data from multiple biomes? (add 2400 ms^-1 Δv for each landing on Duna, 1200 ms^-1 Δv for Ike)

Naturally, the more you want to do, the more Δv you need.  The simplest (go and don't come back) you can do with the same lander you use to land on the Mun.  The most complex -- you want to be looking at sending multiple ships, ultimately with the goal to have the capability to generate your own fuel whilst you're out there (Ore drill + convert-o-tron).  I go one level beyond this - adding UKS and life support mods - my fleets are designed to establish colonies there (and last Duna/Ike window I sent 30 separate vessels!!).

 

 

 

[Montag]

Repeat from other thread:

Would not recommend a space plane to start with. Rockets are simpler.

Duna is not that hard to do with a single launch.  My favorite is to launch a large ship with a Mark 3 cockpit for a lander to land on Ike, land on Duna, and return to Kerbin.  I have the lander separate from a station that has a mobile processing bay that I leave behind.  The station has some Terrier engines and ferries the lander to and back from Ike.  It has enough fuel to ferry and refuel the lander.

[sketchfab]c0a139d53f854b89b2cdf115d402e54a[/sketchfab]
Duna Lander Open by Montag on Sketchfab

https://skfb.ly/FvYJ

Not sure if sketchfab works anymore, but the link will.  This is an older version, before the 10 meter parts.  I would refuel the main launch stage and then send it on its way.  Plenty of dV and excess fuel after Duna capture.  Leaving the station behind with the extra fuel would be an emergency reserve for the future.

[AeroGav]

Space planes can land on Duna,  just make sure it has enough lift rating - ideally 1 lift rating per ton of weight.    Also, one verner motor per 10 tons in the belly can cut down landing speed a lot,  just turn on the RCS and start tapping the translate UP key in the flare.  I usually disable all other directional functions on the thruster so as not to waste fuel.

Here's 3 designs I have made for a Duna mission -

https://kerbalx.com/AeroGav/Astrojet-Citation-X

The one shown in the video has 2 NERVs and a Whiplash.   It has enough fuel to reach Duna and take off to orbit but not return to Kerbin, so the file I have shared on KerbalX   is a hotter version that has drop tanks and separates its jet engines once they flame out.  It has 3700dV in low Kerbin orbit which is easily enough fuel to return from Duna and fly around a bit on the surface.    The craft seats 5 and has an inline clamp-o-tron if you want to try some in orbit refuelling.

To Do - this craft was designed in 1.1.0 and re-entry heat got worse in 1.1.2.,   re-entry on Kerbin is possible (look at my youtube channel) but uncomfortable.   The non-heat tolerant airliner wings require (and tend to create, due to their high lift) a long, gentle, shallow re-entry but this in turn causes heat soak problems in the crew cabin.    It skips sub-orbitally many times before coming down for good so if you added some (retractable, in a service bay?) radiators you could probably cool down in between each bounce off the atmosphere and not come in to land with stuff glowing red.

 

Another design of mine, this time a true single stage vehicle.    It's tiny though,  I imagine you want to bring more than a single mark 1 cockpit and crew member, also the delta v margins on this unrefuelled single stager.

Finally, something much simpler and lower tech - 

https://kerbalx.com/AeroGav/whippynerv

The jet engine on the back stages off, the "tail plane" generates just enough lift to offset it's weight, so the loss of this stage does not produce any change in centre of gravity.

With the jet stage gone, the spacecraft encounters peak aerodynamic heating at mach 5, prompting me to pull up hard..

After passing the "point of maximum pucker" we circularise and find that we still have 2900dV.  Good for a return trip.

[N_Danger]

 I am in the camp of some parachutes. I used 2 radial drogue and 2 radial regular on mine. It requires a burn to slow down for drogue deployment and a final burn at 100 meters to bleed off the last bit of speed (final speed after all chutes deployed was about 20 m/s). The missing leg was due to the kerbal touching a landing leg causing an explosion bug. (which I hope has been fixed with 1.13)

 

It also requires a Service module or station in orbit as it has no direct return to Kerbin capabilities. I used a station and the craft was meant to be re-used multiple times.

And as others have said watch out for slopes. I once slid over 2 KM after landing on a steep slope, Thankfully the chutes stayed open and no explosions occurred.