Duna atmosphere & spaceplanes

[Jean Deaux]

I've been at this game a while now, but have only fairly recently gotten space planes down. I've successfully flown to Duna and have landed on the surface, but have had to do so as if I were on the mun as the atmosphere does not appear to provide any lift at all on my wing surfaces. The air breathing engines do not get any oxygen to run (not totally unexpected as nothing says it has to be an atmosphere of oxygen) but I'll admit I'm surprised that my wing and control surfaces have no effect on steering or with lift. Is this normal, or is the 64bit updated version got a bug in it? I've got EVE on my to-do list and I've seen posts using parachutes to descend so can I expect to find a fully flyable atmosphere on Eve?

[TheTranceMan]

i took a space-plane to duna ages ago. what i experienced was that only the lowest elevations of the planet's atmosphere gave any effect, and it wasn't much. like flying on kerbin at 45km

[Hodo]

I treat Duna like an airless rock in space. The atmosphere is only there for me to aerobrake past that it is useless. The speeds you need to be going to generate any reasonable lift is impossible to land at, and if you bring enough wing to land at lower speeds your craft will tear itself apart on Kerbin. My solution, oh so long ago, was to create a VTOL SSTO Space plane, that could land vertically, not on its tail, and take off vertically. There were no parachutes involved in the design, just a couple of air brakes, and bit of slick piloting.

[Starwaster]

Jean, think about it, less air means you need a lot more surface area on your wings. Moar wings basically.

And moar control surface. You can't take a plane that works on Kerbin (or Earth) and expect that it will just work on Duna too.

[Blind Dead McJones]

Duna's atmosphere is too thin to fly above ~5km without some serious Kerbal overengineering. This is not a bug, that's just how Duna is.

Eve has the opposite issue, the atmosphere is super thick so you could easily get lift at very high altitudes. That said, a lot of people are convinced that a stock SSTO for Eve is impossible. It's atmosphere is very thick at the lowest parts, and it also has no oxygen so airbreathing engines won't work. It's not for nothing a lot of people call Eve the final boss of KSP.

[Cerberus738]

Only kerbin and laythe have oxygen atmosphere, so they are the only places jet engines will work. Duna needs lots of wing area. Eve needs not very much wing area. Also Eve requires piles of deltaV to escape from. The atmosphere extends up to 90km (where kerbin is only 70km) and you can only use rocket engines. Even for a spaceplane the amount of fuel you need to have with you is absurd.... woot

[Jean Deaux]

You really need to work on that bed-side manner as you're implying no thought was given this subject matter and I find that a bit rude.

Jean, think about it, less air means you need a lot more surface area on your wings. Moar wings basically.

And moar control surface. You can't take a plane that works on Kerbin (or Earth) and expect that it will just work on Duna too.

Thanks everyone! I think what was adding to my confusion was the atmospheric pressure gauge just below the altimeter indicator. Once I hit the light blue area I was expecting "Kerbal like" atmospheric performance. Apparently this is not how this gauge should be interpreted.

[MrXenox]

I was able to bring a modified Aeris 4A to Duna, it could function and land like a plane, I found that it only functioned below about 10 kilometres above sea level.

[Geschosskopf]

The air breathing engines do not get any oxygen to run (not totally unexpected as nothing says it has to be an atmosphere of oxygen) but I'll admit I'm surprised that my wing and control surfaces have no effect on steering or with lift. Is this normal, or is the 64bit updated version got a bug in it? I've got EVE on my to-do list and I've seen posts using parachutes to descend so can I expect to find a fully flyable atmosphere on Eve?

Flying on Duna (as opposed to rocketing) is IMHO the most challenging thing you can do with an airplane. As you know, there's no O2 and there's not very much of anything else. So to actually fly on Duna, you need an EXTREMELY low wing loading along with MASSIVE control authority.

Actually building something that will fly in Duna's air isn't so hard. The hard part is making it fly slow enough to land safely in the small areas of relatively flat ground amidst all the sand dunes. Hence the need for ungodly amounts of wing. And having that much wing presents problems getting the thing off the ground back at Kerbin.

I've got a challenge thread that's been going on for nearly a year now and still getting some action. Flying Duna AGAIN. It has some requirements that make it a bit more difficult than if you were just going there for grins. So far, 11 people have succeeded in it. The 1st post has links to all the successful entries. Check them out for inspiration. And if you're interested enough, actually enter the challenge.

Seriously, you're not a real pilot unless you can fly on Duna .

[Jean Deaux]

Interesting challenge, but I'm currently on the "stock" kick. The only add-ons I typically run are for basic instrumentation/information that I find lacking in the core program. Perhaps one day when I feel like expanding further into mods because clearly from your posts, you're not going to accomplish your challenge without mods.

And BTW, greetings from a fellow Louisianian!

[zarakon]

I've made a couple of Duna planes

1. You want lots of wing surface.

2. Use an LV-N engine. It gets really good ISP on Duna due to the thin atmosphere.

3. If you're going to try to land, do it in one of the low-lying canyon areas. The atmosphere is significantly thicker down there, and that's also where you can find long flat areas to bleed off speed before trying to actually touch down. Braking also takes longer in the low gravity.

[Geschosskopf]

Interesting challenge, but I'm currently on the "stock" kick.

Sirene did this challenge all stock using an ion-powered plane. And IIRC this was back before the ion engines got buffed.

And BTW, greetings from a fellow Louisianian!

I figured as much from your handle . I'm actually from Texas but I've lived here on the bayou long enough to go somewhat native.

[RoboRay]

From a pure "lift" standpoint, I've found that the atmosphere of Duna behaves similar to the atmosphere of Kerbin 10km higher.

So, if you can fly above 10km on Kerbin, you may be able to just barely get off the ground down in the low-lying basins of Duna. If you can fly to 15km on Kerbin, you can clear most of the mountains on Duna.

[Geschosskopf]

From a pure "lift" standpoint, I've found that the atmosphere of Duna behaves similar to the atmosphere of Kerbin 10km higher.

So, if you can fly above 10km on Kerbin, you may be able to just barely get off the ground down in the low-lying basins of Duna. If you can fly to 15km on Kerbin, you can clear most of the mountains on Duna.

When comparing performance at Kerbin to anticipated performance on Duna, start by looking at their atmosphere graphs. For a given altitude on Kerbin, find that pressure then find that same pressure on the Duna chart and read the altitude. However, then you have to take Duna's lower gravity into account, which means add about 1000m to the Duna altitude.

HOWEVER, being able to fly at 15000m on Kerbin will NOT get you over Duna's moutains. The vast bulk of Duna, the endless hilly dune fields, average about 2500-3000m. This corresponds to 16000m on Kerbin for atmospheric pressure. Duna's mountains are often 5000m high but many got up over 7000m, so you need to reach 8000m on Duna to feel totally safe. Of course, if you can get to 6000m, you can still get almost anywhere, you'll just have to fly around some inconveniently long chains of high mountains.

But that's the easy part. The hard part is landing. To have a viable Duna plane for exploration or whatever, you need to be able to operate from the dune fields. This means being able to maintain altitude at no more than 30m/s (slower is better) at 2500--3000m on Duna. This is so you can hit and then stop within the very small areas of flat-ISH ground scattered amongst the dunes. If you're chained to landing only in the valleys, you can't do much exploring.

[Jean Deaux]

Sirene did this challenge all stock using an ion-powered plane. And IIRC this was back before the ion engines got buffed.

Oh really? Hmmm, might have to give that a go after all.

[MarvinKitFox]

Duna's atmosphere is too thin to fly above ~5km without some serious Kerbal overengineering. This is not a bug, that's just how Duna is.

To the original guy.. Note that as McJones says, above 5km flying becomes an exercise in futlity.

Note ALSO that much, even most, of Duna lies above this altitude!!!

If you want to fly an aeroplane on Duna, head for the deeper canyons.

Basically, Duna has too little air to fly in, or to land with parachutes only.

But parachutes work fine for assisting in your landing, especially if you land in a canyon.

[RoboRay]

I did say "most" of the mountains. You're definitely not clearing all of the terrain, though... you do have to stay clear of the highlands.

[Snowwy]

Well I'm very very glad that I started reading here BEFORE trying to send the spaceplane I had staged up for Duna. Guess that bad boy's going to Laythe instead.

[zarakon]

Laythe is a much nicer place to fly

[Geschosskopf]

Oh really? Hmmm, might have to give that a go after all.

The more the merrier! There's a lot of good info on flying on Duna in the challenge thread, most of it written in the blood of Kerbals, so hopefully you'll find something useful .

Well I'm very very glad that I started reading here BEFORE trying to send the spaceplane I had staged up for Duna. Guess that bad boy's going to Laythe instead.

Yeah,if a plane flies on Kerbin, it'll fly on Laythe. The lower gravity pretty much balances the thinner air. But that's what everybody wants to do. Few are those who think about flying on Duna, and fewer still are those who actually do it. Take the challenge .

[RoboRay]

If you really want to fly Duna, may I suggest lighter-than-air?

I haven't used it lately, but I think the Hooligan Labs Airship parts are still being developed.

[Geschosskopf]

If you really want to fly Duna, may I suggest lighter-than-air?.

I haven't used it lately, but I think the Hooligan Labs Airship parts are still being developed.

Yeah, but that's the easy way out. I mean, you can even make an Eve SSTO with those balloons .

[sdj64]

My Flying Duna Again challenge entry was all stock, also. But that was after ion engines got buffed. Now you can make an ion hovercraft that can SSTO on Duna.

I've flown propeller craft (with Firespitter mod) on Eve and some Planet Factory planets and they do fly very well in denser atmospheres. But there is so much drag, if you try to use stock parts to fly on Eve you won't get very far.

Only Kerbin and Laythe have oxygen in their atmospheres for jet engines so you'll have to try something else. If you're staying stock you should probably go with ion or nuclear engines. With nukes you'll need an enormous amount of wing area to lift the engine and all that fuel, but it has high thrust compared to ions. Adding a parachute or two just back from the center of mass makes it much easier to land on Duna. Fly parallel to the ground and open the chute to slow down before landing.

Here's a little ion plane I made for Duna. The RCS is for speed boosts for taking off and also to flip the plane back over if it gets stuck upside-down.

[Geschosskopf]

My Flying Duna Again challenge entry was all stock, also.

And somehow I failed to give you the notice for that you deserve. Fixing that right now. OK, fixed on the leader board. Go take a look .

Pity there is no bonus point for doing it stock. That would move you into a tie for 2nd place. Want me to bring that up for a vote or not?