What are the tricks to landing a spaceplane on an extraterrestrial surface?

[davidparks21]

I've lost many a kerbal trying to land a spaceplane on Duna. I've learned the hard way not to try it at any altitude but sea level, and thus I've found about the flattest, lowest region I can. But I still can't quite stick the landing. I can put the plane down with less than -5 m/s vertical speed, and around 70 m/s horizontal speed. But the terrain is just too messy to keep it level and I inevitably veer off course.

The most recent model to make the attempt takes off at 60 m/s from KSC, and can glide land at KSC with relative ease. I usually kick in mild thrusters to control descent on Duna.

Any tips would be great. A few specific questions:

1) Should I engage the brakes while still in the air (before touch down), or should I wait to get stable on the ground before engaging them?

2) Should I move the landing gear out to the wings? These land nicely at KSC, but not sure if I would do better with wider legs on rougher terrain

Edited June 5, 2014 by davidparks21

[Hodo]

I build most of my space planes that go to other worlds with the ability to land as VTOLs. This helps a great deal and makes more sense as I dont have to worry about finding a suitable landing strip of several hundred meters when I only need an area the size of the craft to set it down.

As seen below, a SSTO VTOL Space plane.

And the later variation that landed on Ike.

[O-Doc]

You can't really diagnose without images or a craft file. It sounds to me like a rigidity problem. Do you do steering tests at take-off speed? Also, have you disabled the brakes on your front gear/s?

[eempc]

Yesterday I tried to land horizontally near the easter egg on Duna but after the 20th attempt, I gave up and just did a vertical landing and belly flopped onto the landing gear at 20m altitude.

Very few planes in real life can land on rough terrain and Duna is full of bumpy surfaces. I'm certain it is possible in KSP but you would probably need to build a plane specifically for that.

Correct me if I'm wrong but unless you have airbrakes from the B9 pack, engaging the brake while in midair won't do anything. It will be one less thing to worry about it when you touch down. RCS thrusters are so far the closest thing to airbrakes using stock parts.

Depending on what your plane looks like, more gears might help. My planes used to have 3 gears and would tip over forward onto its left or right "shoulders". Adding 2 more gears stopped that from happening.

[Maelstrom Vortex]

Haven't done it yet, but I have a plan for it. I'm going to use a space plane that has landing gear, but can also deploy cutes. Aim for a nice flat spot, chute down.. then take off from the surface after fixing my chutes.. return to kerbin, repeat on re-entry. Saves all that expended fuel on the descent.

1. After

2. On the wings.. more stable with a broader base.. if you need more belly space, add a pylon or two to hold them on, it doesn't hurt stability much. If you want a REALLY stable base, add a few structural panels below your belly.. mount your wings to those.. and then you'll have a practically flat belly making for nigh perfect gear alignments.

3. Put a pair of gear as near to the rear of your craft as possible if you're going for a horizontal landing to reduce risk of bottoming out your engines.. try to land at a nose up pitch of between 10-20 degrees above horizon. Depending on your engine... keep it at 10-20% thrust.. try to balance your speed or glide it down to less than 70 m/s. If stability is an issue for you on landing, consider a strong inline reaction stabilizer set.. one for the front, one for the rear, should give you great control.

Edited June 5, 2014 by Maelstrom Vortex

[bsalis]

Landing speed is so fast on Duna due to the thin atmosphere, that it is best to not try land like an aircraft.

Simple way to approach this is to make a tailsitter. Parachutes on the nose help land with this configuration.

Either that or vertical lifting rockets (ie. a VTOL, through strictly speaking a tailsitter is still VTOL too).

[KerikBalm]

Or retrorockets to brake without tipping over (as wheel brakes may do).

On some of my designs, I put some 24-77s facing forwards to brake... it doesn't add much weight, nor do I use much dV to stop....

But I also support the parachute idea.

I haven't had much success flying on duna, except under canopy.

The lack of oxygen makes it rather pointless....

I made some electric propulsion, tried to make the stats realistic... but... flying on duna is just plain hard... (the bad aero model with L/D changing depending on airspeed doesn't help).

I don't bother SSTOing to any place but laythe.

If it doesn't have an oxygenated atmosphere, I just use a SSTO lifter, and the rest of the flight is done with a craft meant for operation in a vacuum, or near vacuum (ie, with parachutes).

Single stage to LKO to deploy the:

single stage Kerbin -> Duna and Duna-> kerbin transfer stage

single stage Low Duna orbit -> duna surface -> back to low duna orbit and rendevous with transfer stage

100% reusable, and IMO more fun than SSTD&B (single stage to Duna & Back) - but I find landers and oribtal rendevous to be fun.

[O-Doc]

Very few planes in real life can land on rough terrain and Duna is full of bumpy surfaces. I'm certain it is possible in KSP but you would probably need to build a plane specifically for that.

You need to invest about 5-10% of aircraft weight onto structural integrity. You also need to drop test your aircraft from about 10m on Kerbin using gravity hack. Plus, you need to do full speed taxi tests to make sure that craft doesn't rip apart on landing.

These are good examples of craft built to withstand extra-planetary landing requirements:

Airwolf

Flyingfox

Notice the use of girders and struts in just the right quantities to make the craft evenly spongy yet, still firm enough to resist weight shifting.

Parachutes help if you want to go that way. Vertical landings work too but you get two issues. One, you will use up more fuel thus reducing your payload capacity. Two, you don't get the negation of horizontal forces that rolling landing provides which always has the potential of shearing off parts if you don't stick the landing right, which is more difficult given a plane's usual asymmetry.

[Skorpychan]

Use drogue chutes to slow down ahead of time, maybe?

[davidparks21]

So many good ideas! Thanks everyone. I'm going to send another craft over there and still attempt this. I'm going to try putting a parachute on the back of it and pop it just at touch down like a drag racer. Also going to try disabling the front wheel brake, that was a nice idea. I've gotten landed a few times, it just gets squirly on me and goes sideways before getting the speed under control. Structural integrity looks good, I didn't do the drop test, but I landed it hard at over -10m/s at KSC without a problem.

Engaging your brakes before landing doesn't do anything until you touch down, I just wasn't sure if it was affecting my stability when I touched down. Doesn't seem like it, I tried both ways on a number of landings in the rolling hills behind KSC and didn't perceive any difference, pre-engaging seemed better in-so-far as you don't have to distract yourself from the controls to engage them after touchdown.

Now that I've failed so much I really want to succeed at landing "the hard way" on Dune.

I've also practiced a bunch of landing in the green hills behind KSC throttled up at ~80m/s (similar to the landing speeds at Dune near sea level). Easy job of it, so maybe I've now improved my piloting skills some too.

I'll post some screen shots *when* I finally succeed. ;-)

[kidolvski]

It's really a shame that drogue chutes dissapear when you touch down. Otherwise you could do SR-71 style landings.

You could still try to land the plane with some parachutes, in my experience, it does work, but it's important to use drogues so the sudden G-forces don't rip apart the plane when the main chutes open.

[O-Doc]

If you want to practise hairy landings there's a shelf in the right side of the mountains directly west of the KSC runway. You get a good couple of hundred meters before you run out "road" and it has a nice unevenness to it that will test a craft's grip on the ground. It's my favourite high difficulty landing trial area.

[Mesklin]

For atmosphere less bodies you can use main tail engine for vertical landing on additional legs, like on pictures

[Andrew Hansen]

When I land on Duna, I nearly always use a VTOL. If you use FAR, you can use a high angle of attack and generate a lot more lift (and drag) on flare than in stock.

This is an oldish video, but not too old, in which I send a VTOL SSTO to Duna and back (actually the SSTO runs out of fuel due to my inefficient flying on the burn back to Kerbin). I had 100 m/s left to go.

If I wanted to land horizontally, I would not use a Kerbin-to-Duna-and-back SSTO. I would use a small plane with an external command seat on it powered by an ant engine and some fuel to return to Duna orbit after landing. With a small plane and lots of wings, it would be possible. I think that if you have a landing speed of less than 30 m/s on Kerbin, you should be set for Duna.

[Tortoise]

You can also fire up the engine and slightly burn retrograde before the main chute opens, to slow your speed down further and reduce G's.

But with the chutes, you can just re-pack them once you land. Just EVA a kerbal and right-click the parachute.

[Zephram Kerman]

I like to use a combination of wings, parachute, and thrusters to land. Makes things super easy. If you like the kethane turbine, that and the wings can cruise around to explore large areas and pick the perfect landing site.

The DERP4 (Duna Environment Research Prototype mk4) probably has too many wings. After experimentation, I think it would have been fine with half that. But it sure was a joy to fly it around. Perfect for scouting colony sites or locating anomalies. Thanks to the generator, drill, and converter, it can refuel and continue to explore indefinitely.

I'll make a better video of it... someday.

[davidparks21]

Yeah! Stuck the landing, finally! That was seriously HARD!!! And on my last attempt before I was going to give up entirely!

I used the parachute just before touch down, even with the parachute I failed 5ish times. Brakes are near worthless on the surface of Duna, the gravity is so low you skim across the surface, this is the key reason it's so hard I think, it's really easy to skim and get yourself sideways.

So deploy a parachute just as you touch down, that helps, then lean on the reverse RCS immediately after you kick off the parachute - it'll drop off as soon as your wheels are down, and you won't be out of the woods by then, RCS are your real "brakes". Engage the landing brakes before you ever touch down (you've got too much to worry about to deal with them after touchdown), they'll eventually do some good, it doesn't hurt any to engage them beforehand. Oh, and find the flattest, lowest spot you can (I actually did this at 1000 m, stupid, but I was gunning for being close to the anomaly.

A look at the results, thanks for all the ideas!!

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[Maelstrom Vortex]

You use a space plan design very similar to my own. Did you launch yours like a shuttle or horizontal takeoff? Just curious.

[Kasuha]

To land horizontally on Duna, you need a lot of wing area. Atmosphere is very thin and you need to compensate for it.

The approach is to descend fast so you don't lose much speed and lift (but only as fast that you're still able to level the flight), then fly along the surface till you bleed enough speed to be able to touch down.

For braking, you need to have front wheels with brakes switched off. And you need the wheel base to be sufficiently wide or the Duna surface will turn you upside down.

I was able to land on Duna horizontally and with no thrust applied with this plane.

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Edited June 7, 2014 by Kasuha

[davidparks21]

You use a space plan design very similar to my own. Did you launch yours like a shuttle or horizontal takeoff? Just curious.

Horizontal take offs and landings, with a whole lot of retries on Duna.

@Kasuha that's a goregeous little plane, I can't believe it lands on Duna, the wing surface looks so small! I would think it would come down way too hard. You didn't make the whole trip without refueling did you??

@Andrew Hansen that was a pretty awesome video! Nicely done (and well edited), I enjoyed watching it!

[Kasuha]

@Kasuha that's a goregeous little plane, I can't believe it lands on Duna, the wing surface looks so small! I would think it would come down way too hard. You didn't make the whole trip without refueling did you??

Thanks, unfortunately the plane got nerfed with 0.23.5 as the inline docking port is now over 0.8 t heavier. And there was no refueling on that trip. There seems to be very little fuel left when leaving the atmosphere but that's because I disabled fuel in the rocket tank. I wanted to dry out the two jet fuel tanks but save whole rocket fuel tank for transfer.

[Superfluous J]

(note, the first 10 minutes or so are setup)

[ArcFurnace]

I'm going to try putting a parachute on the back of it and pop it just at touch down like a drag racer.

As you found out, stock parachutes are automatically cut loose as soon as you touch the ground, but the RealChute Parachute Systems mod rewrites things so that you have proper drag chutes, among other things. They might come in handy.

Edited June 7, 2014 by ArcFurnace

[Kasuha]

(note, the first 10 minutes or so are setup)

That's kind of exactly how my Duna landing went on - including the horrible failures phase. And the moment I added wheels to wingtips I nailed it on first attempt too

I just didn't have the luxury of quicksaves in atmosphere by that time.

[Superfluous J]

I just didn't have the luxury of quicksaves in atmosphere by that time.

After flying to the Desert Temple (and not knowing where it was) in 0.23 I decided to never fly again... until they gave us in-atmo quicksaves. Now I'm building planes for everything!

Well not everything but most things where there's atmosphere involved.