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Foxster

Parachute-only Duna landing

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Posted (edited)

Considering that Duna is commonly the next planet that most people visit after Kerbin, it can be surprisingly easy to crash there due to the thin atmosphere and so the ineffectiveness of parachutes. 

So I thought I'd see what was involved with getting down to the surface with just a de-orbit burn and maybe a blip of throttle near the surface i.e. without loads of engine braking that wastes dV that could be better used for the return journey. 

Here is what I have so far...

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'Chutes won't open until a minimum speed is reached and there seem to be no stock settings to override this. It is ~510m/s for drogues and 220m/s for main 'chutes. You can change the minimum pressure and altitude that they open at though, as long as the minimum speed is reached. 

So I changed the settings so the drogue chutes open at 4000m and the mains at 2000m to get them working for longer. 

Then there was the matter of getting the speed down enough so that the chutes would deploy at all. The no-engine solution for this was to use some air-brakes, which did the job nicely. Earlier in the game before these are unlocked I suppose some wing parts could be used instead, though they will probably need to be dumped on Duna's surface before lifting off from there. 

With air-brakes, then drogues and then main chutes, the 9t craft above landed OK without any engines braking in one of Duna's wide valleys at near sea level. 

Thoughts?

Edited by Foxster
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On 2017-06-19 at 2:35 PM, Snark said:

Yup, building a Duna airplane is definitely doable, and can be a fun change of pace to try.

The main challenge is getting the landing speed low enough not to break up on landing.  Duna's atmosphere is so thin that even spamming lots of wing area, it can be tricky to go really slow without stalling; and also, Duna doesn't have a lot of really flat areas.  It tends towards gently rolling hills everywhere.  Those gentle hills are no problem at all when you're coming down on parachutes, but they're a major pain in the posterior when you're gliding along at nearly 100 m/s looking for a place to land.

I've had best results when I mount a couple of Vernor engines on the underside of the plane (one in the front, one in the back), with an action group toggling them on/off.  They don't have to be strong enough to lift the plane (I'm not building a VTOL); just enough to provide a bit of assistance. I leave them off most of the time, and turn them on only when I'm about to land.  This gives a few benefits:

  • By providing some lift, it allows me to slow to a more manageable speed for landing.
  • Since I tip the nose up when I flare for landing, that points the Vernors somewhat forward, which means that their thrust helps to slow me down.
  • When it's time for takeoff, it helps me get airborne sooner because the one in the nose helps shove the nose off the ground and get me rotated for takeoff.

 

 

You can do the same thing with nuclear engines and a Mk3 cargo bay, if you want to try something a smidge larger. Doesn't really count as a no-engine landing by that point, of course...

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There's also this tool for finding the number and type of parachutes you'd need in a landing with a desired touchdown velocity:

https://web-beta.archive.org/web/20161225235749/http://ksp.freeiz.com//

As far as the OP, for anything heavier than a microlander, I tend to use a powered descent. Although my rover delivery system comes in at transfer velocity, so I use the inflatable heat shield and parachutes for that particular type of mission.

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