Landing a spaceplane on Duna, horizontal landing, no chutes

[Cirocco]

Right so I know there were a few people waiting to see pictures/ video of me pulling this one off. Sadly, the mission has been postponed at least one day since it seems that a few design changes which I though were insignificant between the test version and the one I wanted to use now are in fact a huge deal (wheel positioning being one of them). So I'll have to adjust design, add some improvements and I'll probably try the landing again tomorrow. In the meantime: any additional tips are more than welcome.

The rules I want to abide by are:

a) stock parts only, stock atmo as well.

no VTOL. This spaceplane is supposed to land like a regular old plane. Some retro-rockets or a limited amount of vernor engines is fine, already using that.

c) no parachutes to land. I may use one to slow down. Maybe.

d) no clipping to increase performance. That includes airhogging and clipping wing surfaces to increase lift ratio (which it appears I need more of...)

so yeah, mission postponed, any advice is welcome. I started a new thread because I felt we were kinda hijacking the RAPIER one...

Edited September 1, 2014 by Cirocco

[Tery215]

Try sticking more wings on. Even if you have to put 20 more on.

[Cirocco]

Update: after some significant adjusting of the design and doing some research on easy-to-achieve landing sites, the KSS Dauntless is now capable of slowing down to under 100 m/s in a glide when landing. That should be enough for the landing gear to get through the impact. Will run the mission tomorrow, now all I need is some luck with the terrain. Really, it's the terrain that's the killer, not the atmosphere. I can take measures for the atmosphere. I can't do much about the terrain other than pray.

And I'm not a religious person

Proof of concept:

http://imgur.com/xkPyFtv

63m/s horizontal, 6.1 m/s vertical. Under 100 m/s and 5 m/s respectively is the sweet zone where you can safely land.

It. can. work. I know it can.

I'll show you tomorrow. I'll show YOU ALL!!! *cue maniacal laughter*

[Hodo]

There is a trick to VTOLs.

Design your craft so the CoM does not move or does not move enough to affect your VTOL ability.

It used aerospike rockets for its VTOL engines. They were the only thing powerful enough to lift its bulk on Kerbin, and a bit of an overkill on Ike.

[Cirocco]

It worked. The test worked. Successful landing under simulated conditions using hyperedit.... and I forgot to take screenshots up until the very last moment.

There are no words.

well here's the two that I DID remember anyway. Full mission to be flown tomorrow.

Javascript is disabled. View full album

P.S.: Yes, those are two aerospikes firing to slow down as quickly as possible.

[Cirocco]

There is a trick to VTOLs.

Design your craft so the CoM does not move or does not move enough to affect your VTOL ability.

http://i.imgur.com/HFzfRDl.jpg

http://i.imgur.com/iS69FZT.jpg

http://i.imgur.com/BkeVXUE.jpg

It used aerospike rockets for its VTOL engines. They were the only thing powerful enough to lift its bulk on Kerbin, and a bit of an overkill on Ike.

oh I know how to do VTOL. I just didn't want to in this instance

and designing so that the CoM doesn't move is great for lightweight VTOL, but can be quite problematic for large ships.

[O-Doc]

You need some thrusters underneath to reduce your vertical velocity enough so you don't break your landing gear.

[General Rarity]

You need some thrusters underneath to reduce your vertical velocity enough so you don't break your landing gear.

I am fairly certain landing gear don't break (when extended and pointing not towards space), your ship breaks instead. Unless your talking about landing struts, but this is a spaceplane/horizontal landing challenge/thingy, no?

[Hodo]

oh I know how to do VTOL. I just didn't want to in this instance

and designing so that the CoM doesn't move is great for lightweight VTOL, but can be quite problematic for large ships.

That craft in those pictures is 104 tons on take off. If that is lightweight to you, then you are playing on a different scale.

[Cirocco]

That craft in those pictures is 104 tons on take off. If that is lightweight to you, then you are playing on a different scale.

Interesting. Which techniques do you use to keep the CoM from shifting then? Simple symmetry doesn't cut it anymore when going huge, you need to make sure that the wieght distribution is even on opposite sides of the CoM. How do you ensure that?

[Cirocco]

You need some thrusters underneath to reduce your vertical velocity enough so you don't break your landing gear.

vertical verlocity is okay, even without addition of vertical thrust. If the landing spot is low enough, the plane provides enough lift, even in Duna's thin atmosphere. That being said, I do use a couple of vernor engines to reduce vertical velocity just a bit more, just to be safe.

I am fairly certain landing gear don't break (when extended and pointing not towards space), your ship breaks instead. Unless your talking about landing struts, but this is a spaceplane/horizontal landing challenge/thingy, no?

Yup, horizontal landing only. A small amount of thrust to slow descent is fine, but this is not a VTOL challenge, it's a HTOL one. As for the landing gear: it doesn't break if you put enough of them on the same line so they all touch down at the same time and share the load. The biggest problem in the later stages of testing was the fact that you come in so fast and the gravity is so low that you're almost guaranteed to bounce and likely clip the surface with a wingtip. And once that happens, you're guaranteed to spin out of control and die horribly. This was solved by putting additional landing gear on the wingtips to ensure they don't crash into the ground and using forward-firing aerospikes to slow down as quickly as possible and minimise the bounce.

[Wanderfound]

Interesting. Which techniques do you use to keep the CoM from shifting then? Simple symmetry doesn't cut it anymore when going huge, you need to make sure that the wieght distribution is even on opposite sides of the CoM. How do you ensure that?

RCS Build Aid and spreading your fuel load laterally instead of longitudinally. It's not too hard to get the CoM -> dCoM distance down to below one metre. Fine tune by shuffling the lateral tanks forwards and backwards small amounts.

[Cirocco]

RCS Build Aid and spreading your fuel load laterally instead of longitudinally. It's not too hard to get the CoM -> dCoM distance down to below one metre. Fine tune by shuffling the lateral tanks forwards and backwards small amounts.

That's the technique I used on lightweight VTOL's, but it seemed it would lead to kind of silly designs when going huge and seemed to become less reliable in bigger designs. Maybe that was just inexperience on my part though...

Whelp, I know the next challenge I'm setting myself: something VTOL related!

Also, what is RCS build aid/how does it work exactly?

[Wanderfound]

That's the technique I used on lightweight VTOL's, but it seemed it would lead to kind of silly designs when going huge and seemed to become less reliable in bigger designs. Maybe that was just inexperience on my part though...

Whelp, I know the next challenge I'm setting myself: something VTOL related!

Also, what is RCS build aid/how does it work exactly?

It's a VAB/SPH utility mod: http://forum.kerbalspaceprogram.com/threads/35996-0-24-x-RCS-Build-Aid-v0-5

The basic function is in balancing RCS. Tell it what direction you're interested in, and it will tell you how much RCS thrust you have in that direction and how many kN of torque is being generated by any asymmetry. It also gives easy visual cues, and updates live while you're placing thrusters. Place one set of linear thrusters on one side of CoM, pick up another pair with your mouse and wiggle them about in vaguely the right position until the torque value is as close to zero as you can get it.

It also does the same trick for non-RCS thrust. Plus it gives you an extra spherical marker for dry CoM (i.e. unfuelled) and measures the distance between wet and dry CoM, also updating this figure live while you move parts about.

Very, very, very useful.

[Cirocco]

oh wow that is a VTOL builder's dream right there. Very interesting mod, will certainly look into it.

Man for someone who prefers stock I'm starting to pile up a good number of mods I either have or need to check out

[Geschosskopf]

Right so I know there were a few people waiting to see pictures/ video of me pulling this one off. Sadly, the mission has been postponed at least one day since it seems that a few design changes which I though were insignificant between the test version and the one I wanted to use now are in fact a huge deal (wheel positioning being one of them). So I'll have to adjust design, add some improvements and I'll probably try the landing again tomorrow. In the meantime: any additional tips are more than welcome.

The rules I want to abide by are:

a) stock parts only, stock atmo as well.

no VTOL. This spaceplane is supposed to land like a regular old plane. Some retro-rockets or a limited amount of vernor engines is fine, already using that.

c) no parachutes to land. I may use one to slow down. Maybe.

d) no clipping to increase performance. That includes airhogging and clipping wing surfaces to increase lift ratio (which it appears I need more of...)

so yeah, mission postponed, any advice is welcome. I started a new thread because I felt we were kinda hijacking the RAPIER one...

Howdy Cirocco. Glad to see you're interested in flying on Duna, which sadly is a neglected art. In my sig is a challenge where you can see many people's ideas on how to do, although only 1 of them is all-stock. Still that one (an ion-powered thing) meets the rather rigorous flight requirements of the challenge.

As you've probably noticed by now, the main issue with flying on Duna is getting slow enough to land safely. Entering the atmosphere from space, flying around, and even taking off aren't too hard, but safely landing is a bear due to 1) the rarety of flat ground and 2) the high altitude of most of the surface. This leaves you with 2 basic choices when designing a Duna plane.

The 1st choice is to design so you can land in the depressions, which have the lowest altitude and the biggest expanses of flat ground. This allows for much higher landing speed, so is a much easier design challenge. However, a design that relies on depressions to land rather defeats the purpose of taking a plane to Duna. The reason for having a plane instead of a rocket lander is so you can explore the planet faster and less boringly than using a rover, but depressions only cover about 15% of Duna, which means you can't explore the vast majority of the place.

The 2nd choice is to design so you can land out in the vast dune fields that cover the other 80% of Duna (the remainder being mountains). The average altitude in the dune fields, however, is about 2500-3000m, which equates to like 16-17km on Kerbin, and flat areas are only 200-300m long at best, and rather scattered about. The short LZs require a very slow landing speed (30m/s tops), which the altitude makes very hard to achieve. Plus, the low gravity greatly reduces the effectiveness of wheel brakes, and the thin air reduces the effectiveness of air brakes and chutes. Designing this short of plane is what my challenge is about.

Also note that any plane designed to land out in the dunes will have such a huge amount of wing area that it usually won't be possible to launch it atop a rocket, even in stock air. And anything that can SSTO from Kerbin by itself probably won't be able to fly slow enough on Duna to land out in the dunes. So the main options seem to be to attach a horizontal ascent stage on the back of the plane, which might also include a transfer engine, or (if the plane is small enough) build a cage lifter around it, or lift 2 planes at once facing in opposite directions so their lift forces cancel out.

Anyway, I wish you luck. Flying on Duna is a worthy challenge .

[Cirocco]

Hmmmmm... Had a look at your "Flying Duna Challenge" Geschosskopf. By the looks of it, my own plane (the KSS Dauntless, 3 seater runway-Duna surface-runway SSTDABTK without refuel) meets almost all your demands: at the moment it uses I believe 7 vernor engines on the underbelly to slow vertical descent a little more (it can probably go without, but with is just a bit safer for my kerbals) and since it is full stock, it uses liquid fuel/ox mix, not kethane.

Still, if I redesign a little bit more (get rid of the vernor engines, find a bit more room for even MORE wing surface) I think it would be elligible. As for the bouncing and long decelleration needed after touchdown, I have my own way of dealing with that: two forward facing aerospike engines. As soon as I hit the ground, those two are fired at full throttle in order to slow down the plane as quickly as possible.

[Geschosskopf]

Hmmmmm... Had a look at your "Flying Duna Challenge" Geschosskopf. By the looks of it, my own plane (the KSS Dauntless, 3 seater runway-Duna surface-runway SSTDABTK without refuel) meets almost all your demands.

Even landing at a minimum of 2500m? And being able to fly at least 1/2way around the planet and land again? Well, give it a go then! The more the merrier!

[Overfloater]

Hey Cirocco, did you spread the landing gear as wide as possible? The major problem caused by bouncing on Duna is that the craft easily starts rolling.

Also, putting many landing gear would be a mistake. Minimize the gear so you don't encourage the craft to bounce even higher!

The wide gear should be almost under the CoM, not only it will take most of the strain but also it will be harder to start rolling. One gear under the tail would also help in landing on Duna.

Here's a few pictures of my old plane, designed for landing in crappy places (Duna):

Javascript is disabled. View full album

And a recent video, this one was more of a stunt than the previous one, as I didn't plan going to Duna with this craft. But thanks to the crazy amount of lift it made it.

Descent is at 8:30, touchdown at 9:31.

(These 2 crafts rely on air-hogging. But I wanted to give my 2 cents about Duna landings, and i have no idea how air-hogging helps here)

Edited September 2, 2014 by Overfloater

[Volcanix]

Hey Cirocco, did you spread the landing gear as wide as possible? The major problem caused by bouncing on Duna is that the craft easily starts rolling.

Also, putting many landing gear would be a mistake. Minimize the gear so you don't encourage the craft to bounce even higher!

The wide gear should be almost under the CoM, not only it will take most of the strain but also it will be harder to start rolling. One gear under the tail would also help in landing on Duna.

Here's a few pictures of my old plane, designed for landing in crappy places (Duna):

http://imgur.com/a/r9sM2

And a recent video, this one was more of a stunt than the previous one, as I didn't plan going to Duna with this craft. But thanks to the crazy amount of lift it made it.

Descent is at 8:30, touchdown at 9:31.

http://youtu.be/9my1tuCZuC8

(These 2 crafts rely on air-hogging. But I wanted to give my 2 cents about Duna landings, and i have no idea how air-hogging helps here)

Woah.. Man, you build awesome SSTO's. I've already watched nearly all of your SSTO videos, but could you please make a tutorial on how you build these? I really love the design and I'm just getting into spaceplanes, and I would highly appreciate it if you would find the time to do so.

[Cirocco]

Even landing at a minimum of 2500m? And being able to fly at least 1/2way around the planet and land again? Well, give it a go then! The more the merrier!

I'll have to make a bit of design adjustments to meet the 2500 requirement safely (a bit more wing surface mostly) but yes, with proper adjustments I believe she'll be able to do it. As for flying halfway across the planet: she's designed to go from the runway on Kerbin to landing on Duna to coming back to the runway all without staging or refueling. So yes, she can can fly half the planet, no problem .

Biggest issue you might have is the fact that you will NEVER want to try to land her on Duna with a full tank. She's designed to arrive at Duna with her tanks more than half empty (from making orbit around Kerbin and doing the transfer burn). If you try to land the 83 ton fully fueled bulk of her, I'm pretty sure there's no way to stop her from crashing and burning horribly.

Hey Cirocco, did you spread the landing gear as wide as possible? The major problem caused by bouncing on Duna is that the craft easily starts rolling.

Also, putting many landing gear would be a mistake. Minimize the gear so you don't encourage the craft to bounce even higher!

Oh yes, the wide landing gear base is something I learned after the umpteenth time a landing went fine until the plane bounced and the wingtip clipped the surface Now I have gear on the very wingtips

The wide gear should be almost under the CoM, not only it will take most of the strain but also it will be harder to start rolling. One gear under the tail would also help in landing on Duna.

I actually have the bulk of my gear near the tail to take the strain of the impact and avoid tailstrikes (I tend to land nose tilted up). My CoM is quite far at the back though, so the gear is actually relatively close to the CoM.

I did add quite a bit of gear back before I realised that gear on the wingtips was actually what I needed. Maybe losing a few there is not a bad idea, thanks for the tip.

Here's a few pictures of my old plane, designed for landing in crappy places (Duna):

http://imgur.com/a/r9sM2

And a recent video, this one was more of a stunt than the previous one, as I didn't plan going to Duna with this craft. But thanks to the crazy amount of lift it made it.

Descent is at 8:30, touchdown at 9:31.

http://youtu.be/9my1tuCZuC8

(These 2 crafts rely on air-hogging. But I wanted to give my 2 cents about Duna landings, and i have no idea how air-hogging helps here)

I'll have a look at those when I get back home from work, thanks

[Geschosskopf]

I'll have to make a bit of design adjustments to meet the 2500 requirement safely (a bit more wing surface mostly) but yes, with proper adjustments I believe she'll be able to do it. As for flying halfway across the planet: she's designed to go from the runway on Kerbin to landing on Duna to coming back to the runway all without staging or refueling. So yes, she can can fly half the planet, no problem .

Biggest issue you might have is the fact that you will NEVER want to try to land her on Duna with a full tank. She's designed to arrive at Duna with her tanks more than half empty (from making orbit around Kerbin and doing the transfer burn). If you try to land the 83 ton fully fueled bulk of her, I'm pretty sure there's no way to stop her from crashing and burning horribly.

Yeah, the challenge specs aren't quite what you're trying to do here. You're just trying to get there and back again, whereas the challenge envisions the plane as a component of a long-term, wide-spread exploration/colonization project. The challenge plane is intended to allow exploration all over Duna and/or be a connection between several scattered bases that's superior to or at least more interesting than a rover. There is, for example, no requirement at all that the challenge plane ever leave Duna, although there is a requirement to be able to refuel it at Duna if it uses consumables.

[Cirocco]

Yeah, the challenge specs aren't quite what you're trying to do here. You're just trying to get there and back again, whereas the challenge envisions the plane as a component of a long-term, wide-spread exploration/colonization project. The challenge plane is intended to allow exploration all over Duna and/or be a connection between several scattered bases that's superior to or at least more interesting than a rover. There is, for example, no requirement at all that the challenge plane ever leave Duna, although there is a requirement to be able to refuel it at Duna if it uses consumables.

I know that leaving Duna isn't a requirement, but seeing as she's able to make orbit around Duna, she can fly pretty much anywhere on the planet. Just make orbit, adjust inclination if necessary, de-orbit at target and done. And refueling is possible through the nose-mounted shielded docking port, but seeing as that docking port isn't on any standard/fixed height, it might a bit difficult to do a refuel on the ground.

The initial objective was runway-Duna surface-runway, but I think she doubles up as a Duna plane for this challenge. She'll just have a ton of superfluous air intakes, air breathing engines, liquid only tanks, etc...

That being said I do like the challenge of flying on Duna so I might make a dedicated stock plane for this challenge. I'm thinking a long-range Duna plane capable of transporting 10 or so kerbals between bases. With that in mind I do have a question: do you object against the use of nuclear engines as propulsion method? If you're going for a transport/exploration plane then I can imagine that a radioactive exhaust might be less than desirable

Edited September 3, 2014 by Cirocco

[Geschosskopf]

I know that leaving Duna isn't a requirement, but seeing as she's able to make orbit around Duna, she can fly pretty much anywhere on the planet. Just make orbit, adjust inclination if necessary, de-orbit at target and done. And refueling is possible through the nose-mounted shielded docking port, but seeing as that docking port isn't on any standard/fixed height, it might a bit difficult to do a refuel on the ground.

Except that the challenges specifically says this doesn't count. All trips between points A and B on Duna have to be within the atmosphere, supported by wings or helicopter rotors, and not so fast as to be ballistic.

[Cirocco]

Except that the challenges specifically says this doesn't count. All trips between points A and B on Duna have to be within the atmosphere, supported by wings or helicopter rotors, and not so fast as to be ballistic.

oooooh missed that bit. In that case I'm not sure. I estimate she'll have about 2000 m/s delta-V left after touching down, don't know how far that would get you. Don't have a clue how much you'd have with the liquid tanks fully filled. Probably in the range of 5000 m/s or so.

I'll have a look at making a dedicated Duna plane for this challenge then. I do like flying at Duna.

EDIT: Make that two dedicated planes. I've been thinking about making my own Duna base anyway, I could use these in my own program too. One I imagine will be a single-seater exploration plane, the second one a mass crew transport. 10 or so kerbals from one side of Duna to the other should be feasible. MORE EDIT: Had another read of the rules. Make that a two or three seater exploration plane.

ANOTHER EDIT: man I wish 0.25 was here already. SP+ parts would make a large Duna plane so much easier and cooler-looking.

Edited September 3, 2014 by Cirocco