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Duna Airplanes: Discussion and Advice


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Recently I've been trying to design an airplane to be able to fly on Duna. I've gone through many designs so far, none of which seem to work well. Rocket planes are often too heavy and cumbersome, while electric prop planes never seem to get enough thrust in the thin atmosphere. At this point, I'm wondering if planes on Duna are really that viable in practice. I was wondering what suggestions, if any, might help out, or if it's even worth it in the end?

Edited by Yellowburn10
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Not as viable as on Kerbin or Laythe. Duna's atmospheric pressure is really low compared to Kerbin's pressure. Less dense atmosphere = less optimal for flight. 

You can do it, but you'd need large wing area or a lot of thrust. Before we can tell you if the ends will justify the means, what exactly do you need a fixed-wing aircraft on Duna for that other solutions can't achieve? 

Edited by Orbital_Decay
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10 minutes ago, Orbital_Decay said:

Not as viable as on Kerbin or Laythe. Duna's atmospheric pressure is really low compared to Kerbin's pressure. Less dense atmosphere = less optimal for flight. 

You can do it, but you'd need large wing area or a lot of thrust. Before we can tell you if the ends will justify the means, what exactly do you need a fixed-wing aircraft on Duna for that other solutions can't achieve? 

Well, I was planning a large excursion to the planet in my current career save, complete with a base, rover and a ship to get too and from duna orbit. I thought a terrestrial airplane would be nice for exploration and for getting to certain spots quicker than a rover, but not as resource intensive as a spaceship.

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3 minutes ago, Yellowburn10 said:

Well, I was planning a large excursion to the planet in my current career save, complete with a base, rover and a ship to get too and from duna orbit. I thought a terrestrial airplane would be nice for exploration and for getting to certain spots quicker than a rover, but not as resource intensive as a spaceship.

Well, that's actually quite legitimate.

With requirements like that, I don't see much else that could deliver.

Have any "drafts" yet? 

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2 minutes ago, Orbital_Decay said:

Well, that's actually quite legitimate.

With requirements like that, I don't see much else that could deliver.

Have any "drafts" yet? 

I'm trying two different designs, electro-prop based and rocket power based. My current designs are all essentially proof of concepts, basically trying to see if what I'm trying to do is feasible. None of them so far have made much progress when it comes to actual flight, although I admit I've been working more with props than anything else. Their thrust is abysmal in Duna's atmosphere, but my design incorporated fuel cells for some incredible efficiency. Unfortunately, I haven't gotten much more than around 40 m/s at best out of them so far. I need some more testing with rocket planes for their performance, but from what I've gathered so far, their weight is a real pain to factor in.

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22 minutes ago, Yellowburn10 said:

I'm trying two different designs, electro-prop based and rocket power based. My current designs are all essentially proof of concepts, basically trying to see if what I'm trying to do is feasible. None of them so far have made much progress when it comes to actual flight, although I admit I've been working more with props than anything else. Their thrust is abysmal in Duna's atmosphere, but my design incorporated fuel cells for some incredible efficiency. Unfortunately, I haven't gotten much more than around 40 m/s at best out of them so far. I need some more testing with rocket planes for their performance, but from what I've gathered so far, their weight is a real pain to factor in.

At 40m/s, all you'll really have is an expensive rover that doesn't even drive on the ground. You're looking for quick, long-range transit, right? You'll definitely hit the long-range factor with an electric aircraft. At least you'll have good endurance times. But, that's not fast. You could keep it if you realize you really need endurance more than speed. 

If you go for a faster, rocket-propelled aircraft, you could still get range, but not for very long. You may not endure well with rockets because of the way rockets are.

You also may want to consider "payloads" if you may. An electric aircraft is going to suffer from any additional weight, so one cannot really handle a significant payload. That could cause you some trouble if you want to carry a lot of material with you in flight. A rocket aircraft could make up for a payload with raw thrust if you get down to it. TWRs are really important to keep in mind. You may even understand why if you play long enough. If you have a higher thrust, you can have a higher weight and still manage to keep a good ratio.

So, are you looking more to cover ground and move equipment/supplies, or are you looking to just observe the Dunan landscape below? 

Edited by Orbital_Decay
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With a Nerv design I can get enough range to circumnavigate Duna. If you can get it to LKO it could fly itself to Duna and land. I put a full set of science gear in the bay so a pilot and scientist could tool around and biome hop. In theory you could visit any spot on the planet to collect science and then return to base for refueling. Even with the large wings it doesn't get a huge amount of lift though. I had to do powered landings and pitch up pretty hard at the end to get it to settle in softly. And of course the Nervs are heavy. This one is 24 tons fueled and has a 17 meter wingspan.

k3JDGef.jpg

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Regarding electric propeller planes for duna: You don´t need much power on your plane. You just need more surface area to transmit that energy to the atmosphere.

9LEUFY8.png

I made this experiment at least a year ago, but I don´t think things changed that much on the aerodynamics side, so it should still work.

So in short: Yes, It´s a viable concept. :)

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Duna airplanes are a fun challenge. The toughest part IMO are the fast landings. Possible solutions include huge wings to get enough lift when flying slowly, or reversible-thrust engines to come to a quick stop, or parachutes and an engineer to repack them after each landing.

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I've been doing a lot more testing recently, and taking everything learned here into account. I've now moved on from testing proof of concepts to actual working prototypes!

 

First is the electro-prop:

3jhJeFH.png

I based this design largely on what KerrMu had posted, and what do you know, the thing actually flew! Sure, it took a moment to get off the ground, but it's far more than any other design of mine. There is a noticeable difference though, mainly this design is powered by fuel cells. While heavier than solar power, it makes a small amount of fuel go a long way. The main improvement with this design over my own was the larger wing design and more efficient design of the engines (I.E. Not enough propellers).

Now the rocket:

5AyOhKC.png

This design has progressed a lot farther than the electro-prop, mainly due to the fact it has a "payload" of a science bay, SAS wheels and a small docking port for refueling. The main difference with this one was switching out the terrier engine I was using before for a NERV engine. I had forgotten that the NERV still works like a charm on Duna, and with it I could make a craft with similar Delta-v as my old designs, but at a fraction of the weight. Plus, I've had much more flight testing with this plane more than anything else, and I've been able to take off, fly and land with reasonable ease for a Duna plane. 

As an unintended feature, this plane also happens to be a Duna SSTO. So there's that.

 

Thanks to everyone for the tips and advice! Hopefully I'll soon have a craft I'm satisfied taking with me to Duna for real.

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Wings are great to get around, and even a few wings on your lander will give it a lot of cross-range to take it to the designated landing site. I find that much easier to do than split-second timing on the de-orbit burn.

The problem I have with Duna planes is takeoff & landing. I'm already struggling with landing in the wild on Kerbin, and Duna's atmosphere doesn't improve matters. However, I had great success with VTOL designs.

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On 8/7/2020 at 11:33 PM, Yellowburn10 said:

Recently I've been trying to design an airplane to be able to fly on Duna. I've gone through many designs so far, none of which seem to work well. Rocket planes are often too heavy and cumbersome, while electric prop planes never seem to get enough thrust in the thin atmosphere. At this point, I'm wondering if planes on Duna are really that viable in practice. I was wondering what suggestions, if any, might help out, or if it's even worth it in the end?

I've successfully flown an electric propeller-driven plane on Duna that worked pretty well and can also do VTOL.  A pair of counter-rotating pusher props on the trailing end of the front wing.  A pair of coaxial counter-rotating helicopter rotors on top of the fuselage for lift at lower speeds or higher elevations, and for VTOL.

Works pretty well, but it only cruises at around 100 m/s so it takes a long time to get anywhere, and like every rotorcraft I've ever tried, I can't use physics warp on it or it goes kablooie.  But it works.

g5Uvgct.png

 

The other context in which airplanes have worked well for me is when they're designed not for cruising around, but rather simply as an orbital descent/ascent vehicle.  A rocket-powered plane works great there; just give it a lot of wing area so it can get its glide speed down.  I put some linear RCS thrusters on the underside, which I turn on for landing to allow it to reduce to a reasonable speed (otherwise it's hard to build a plane that lands on wings alone at less than 80 m/s and they tend to wipe out on landing).  It's not a VTOL, they just provide a bit of lift assist when landing.

Such designs are pretty easy to make, but not well suited for long-distance cruising since they'd run out of fuel pretty quick.

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I love making planes for Duna. The main difficulty is that because of the thin air you will have very high speeds for landing or take-off in a conventional plane, which tends to result in a crater. The solution is to design them as VTOLs or STOLs. The servos in Breaking Ground make it possible to make some pretty elegant designs, but they're by no means necessary. 

Ducted fans work well on Duna, as do homebrew rotors made from elevons. 

Some Breaking Ground-based planes I've operated on Duna:

G2i2zpP.png

Dunabee, a tiny probe plane with rotating rockets. 

R4IDnnJ.png

Skua, an electric VTOL prop craft. Cruises at about 150 m/s, pretty easy to fly. Needs a ton of fan blades to work though. Utterly terrifying to operate on Kerbin because its so insanely overpowered.

qZSHw9y.png

Gabian, a surface/orbital station shuttle. Rotating rockets at the wingtips. 

And here's a pre-Breaking Ground one, a medium cargo transport with fixed VTOL rockets and a flatbed cargo bay:

2RC44tN.jpg

Cyclone. It has roll-on/roll-off cargo and is capable of delivering station modules or a fair bit of fuel to and from orbit.

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Not really VTOL but life like air breaks.
 

I have a decent solution for landing and takeoff on very small spots on Dina.

My airplane is primarily powered by 2 Nervs in the traditional spot at the back of the airplane.

 

however I have 2 small rockets (I forget their name right now) with their thrusters mounted beside the cockpit but aimed forward and down (about 30 degrees below the plane of the plane (that’s a pretty plain plane pun).

So when I am descending I do an unpowered glide and I lock my wheel break.  If I’m coming in too hot I nose up and do quick bursts with my reverse thrusters to slow down.  If I’m coming in too fast I nose down and hit the thrusters to give me more lift.

 

After a few practices you can touch down with around 15m/s of speed which with your breaks locked means you don’t go far.

On takeoff I Lee the nose down and use both sets.  My main engines give me thrust while my lower one pushes the work plane off the ground.  Makes for short runway takeoffs.

 

 

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