How do you SSTO to duna?

[Interstellar Yeet]

Okay so I've tried for 2 days straight to land a plane on duna. I can build a plane that has a really good balance of center of mass and center of lift both with full fuel and no fuel, I can get to orbit, I can get to duna even with a 250 ton Mark 3 cargo plane that needs to orbit kerbin 3 times to even get out of its SOI and over to duna. And I can also land on kerbin. However, I CAN'T land on Duna. There's just no way, and it feels like I never will. I can't even control the plane anywhere near duna. All the way from kerbin over to duna is completely fine, takes a bit of time to turn the giant ass plane sure, but near Duna its impossible. The problems start when i get around like 50k or something around there. From that point on I just can't turn the plane around in less than a really long time, and once I start turning I just keep turning the same way forever, I can't stop it. And once I reach 30k in the atmosphere the plane just goes wild and starts spinning everywhere uncontrollably. I've watched every tutorial I could find, even videos that aren't tutorials just to see what they are doing, I've downloaded countless of Duna planes just to cheat them over to duna and try to land, I've tried with full fuel, no fuel, some fuel here and there, balance things out, but same thing every time. Spin spin spin forever. I'm at a loss of words and action, I've got no clue what to do. I've never been more angry at a game than right now. Sure the 2 first days I played was a bit hard and I managed to land on the Mun and Minmus, rendezvous and even dock fairly easily, but this is just (excuse my profanity) dumb. This community has been very welcoming and helpful since the day I made my account, so anybody, please teach me the ways of SSTO's I beg you ;-; 

So, TLDR; How the frick do you land a SSTO on Duna. I must be missing something. Do I need a ton of reaction wheels and RCS thrusters everywhere? Or is it my angle of approach that is wrong, idk. Someone please help me. I refuse to send a rocket there, once I saw all these crazy SSTO videos on youtube I fell in love with the game for the second time and I probably won't use a rocket again, unless I have to. I love building these planes, and I love flying them. Sorry if I seem really salty, cus I am. LOL 

 

EDIT: https://imgur.com/a/h1lOvbV 

Album here of the crafts I've tried so far, I'll try to see if I can find more but I think i deleted most of those I've failed with. 

EDIT 2: https://www.dropbox.com/s/15ayu33jqe2mngh/Lynni.sfs?dl=0 Here's a savefile as well

Edited November 10, 2018 by Interstellar Yeet

[bewing]

Well, first, ya gotta post a craft or a savegame or even just a pic. There are 18 million rules of thumb for building and flying spaceplanes, and we have no way of knowing which you understand and which are tripping you up.

Since your craft is heavy (MK3), it is absolutely going to need aerospikes on the belly to manage a horizontal landing, unless you want to land your SSTO on its tail.

And yes, the atmosphere on Duna is quite thin, so you are going to need a lot of extra time to make turns and stuff. Yes, you will certainly need extra control to fly in Duna's atmosphere. Yes, RCS and reaction wheels, and big control surfaces. The last few seconds before you land usually require a lot of control inputs, unless you want to crash.

But if your plane is going unstable, that has to come down to two things: drag and CoM. That is, too much drag at the front, and not enough at the back -- and your CoM has to be as far forward as possible. So pump all your remaining fuel into your forward tanks. Then you'd better have some method (besides a parachute) of adding drag to the back end of your spaceplane. Use it. Extend your rear landing gear. Open a cargo bay. Slats? Something.

 

 

Edited November 10, 2018 by bewing

[Pecan]

8 hours ago, Interstellar Yeet said:

 I refuse to send a rocket there, once I saw all these crazy SSTO videos on youtube I fell in love with the game for the second time and I probably won't use a rocket again, unless I have to. I love building these planes, and I love flying them. Sorry if I seem really salty, cus I am. LOL 

I'd love to know how you're doing your space maneuvres if you don't have any rockets.  Perhaps that's the problem.

[Interstellar Yeet]

9 hours ago, bewing said:

Well, first, ya gotta post a craft or a savegame or even just a pic. There are 18 million rules of thumb for building and flying spaceplanes, and we have no way of knowing which you understand and which are tripping you up.

Since your craft is heavy (MK3), it is absolutely going to need aerospikes on the belly to manage a horizontal landing, unless you want to land your SSTO on its tail.

And yes, the atmosphere on Duna is quite thin, so you are going to need a lot of extra time to make turns and stuff. Yes, you will certainly need extra control to fly in Duna's atmosphere. Yes, RCS and reaction wheels, and big control surfaces. The last few seconds before you land usually require a lot of control inputs, unless you want to crash.

But if your plane is going unstable, that has to come down to two things: drag and CoM. That is, too much drag at the front, and not enough at the back -- and your CoM has to be as far forward as possible. So pump all your remaining fuel into your forward tanks. Then you'd better have some method (besides a parachute) of adding drag to the back end of your spaceplane. Use it. Extend your rear landing gear. Open a cargo bay. Slats? Something.

 

 

Thank you that is somewhat helpful. I'll post an imgur album of all the spaceplanes I've tried to land on duna.

1 hour ago, Pecan said:

I'd love to know how you're doing your space maneuvres if you don't have any rockets.  Perhaps that's the problem.

That's easy. I have tons of rockets. I have docked together several rockets in kerbins orbit and flied them over to Minmus and landed them all as a base too, and I'm fairly confident in my rocket building skills so far. And manouvering in space is the easiest thing I've done so far in this game. It's everything else that is hard. Just flying something in any orbit is easy peasy. 

[Pecan]

On 11/10/2018 at 5:25 PM, Interstellar Yeet said:

That's easy. I have tons of rockets. I have docked together several rockets in kerbins orbit and flied them over to Minmus and landed them all as a base too, and I'm fairly confident in my rocket building skills so far. And manouvering in space is the easiest thing I've done so far in this game. It's everything else that is hard. Just flying something in any orbit is easy peasy. 

Then it's very easy.  You build a SSTO lander and use it to shuttle between the surface and orbit.  Refuel on the surface if you're using ISRU, in orbit otherwise.  Aim for 2,600 dV for the round trip and don't forget the monoprop so you can dock with whatever you're meeting in orbit (unless that will do all the docking).  Duna's atmosphere is too thin for parachutes to be useful generally, so just a plain SSTO is best.

Unless your title is wrong and you specifically want to know about spaceplanes.  Although you'll need rockets on that plane.

(waiting for the penny to drop)

[Geonovast]

10 minutes ago, Pecan said:

Duna's atmosphere is too thin for parachutes to be useful generally, so just a plain SSTO is best.

If you pack enough they're good for most of the trip down, you just want a powered landing for the last couple of meters... and obviously an engineer to repack those chutes.

[Pecan]

Just now, Geonovast said:

If you pack enough they're good for most of the trip down, you just want a powered landing for the last couple of meters... and obviously an engineer to repack those chutes.

Agreed, they do work but I've found if you have enough to save a significant amount of fuel on the way down, they add so much mass that you lose more on the way up.  (Sort of, 'in general', there are designs and designs.  It's not a solid rule but I find it easier just to do without them).

[Interstellar Yeet]

2 hours ago, Pecan said:

Then it's very easy.  You build a SSTO lander and use it to shuttle between the surface and orbit.  Refuel on the surface if you're using ISRU, in orbit otherwise.  Aim for 2,600 dV for the round trip and don't forget the monoprop so you can dock with whatever you're meeting in orbit (unless that will do all the docking).  Duna's atmosphere is too thin for parachutes to be useful generally, so just a plain SSTO is best.

Unless your title is wrong and you specifically want to know about spaceplanes.  Although you'll need rockets on that plane.

(waiting for the penny to drop)

Yeah I'm sorry but i meant spaceplanes specifically. https://imgur.com/a/P4Baena I did it tho, no aerospikes or RCS or anything, just the chutes and loading a million saves to manage to land it.  

[Pecan]

1 hour ago, Interstellar Yeet said:

I did it tho (sic)

Congratulations :-)

That's a big old bugger to fly anywhere so I'm not suprised you had trouble but your persistence paid off.  Good for you.

[Interstellar Yeet]

2 hours ago, Pecan said:

Congratulations :-)

That's a big old bugger to fly anywhere so I'm not suprised you had trouble but your persistence paid off.  Good for you.

 Thanks! But yeah it was hell. I was designing planes for 3 days, ragequit for 2 days, then the day after i managed to build a plane that can land on duna and return. Worth it, haha. 

EDIT: Just hope 2700 delta V is enough to get home :O I'm still landed on Duna since I am busy doing stuff

Edited November 12, 2018 by Interstellar Yeet

[Guest]

If you want to use a plane on Duna, it'll have to be a rocket-assisted VTOL or STOL. Otherwise you'll just plow straight into a dune; the air is too thin and the gravity too low to slow down to a safe landing speed otherwise.

Else just use a conventional lander that slows down with parachutes and fires a puff of retro rockets for the final touchdown.

 

[Plusck]

The only time I managed to land "properly" on Duna was with a very light plane with lots of wing, in KSP version 1.1.3. Definitely not able to SSTO from Kerbin.

I can't find any screenshots of the plane on the ground but the number, and names of, the savegames I made at the time are telling:

131 Duna glider 3rd attempt.sfs
131 Duna new glider landing.sfs
131 Duna planes arrival.sfs
132 Duna glider crashed.sfs
132 Duna planes better arrival.sfs
132 Duna planes final arrival.sfs
132 Duna planes post burn.sfs
133 Duna glider better crashed.sfs
133 Duna plane landed upright.sfs

...

[Hodo]

Duna you have to treat like a zero atmosphere planet.  The atmosphere is kind of a joke.. much like Mars in real life.  Even with parachutes you could still be going supersonic on impact with the ground.  So the best bet is retro rockets or some kind of decent rocket to slow your speed and let you land like a VTOL.  

[XLjedi]

I tried a conventional landing on Duna about 3 or 4 times with a Mk3 SSTO carrying a ISRU rover.  I was finally successful, but definitely came in very fast and had to deploy drag chutes.  In hindsight, probably would not attempt that approach again.  Contemplating a few different options now...

Edit:  I managed to locate the pics!

It was no small feat...  If I tried it again with this craft, I'd definitely add 2-4 more drag chutes, and probably anticipate crashing at least 2 or 3 times in the process.  So would have to be working from a save game in orbit just to be safe.

Edited November 12, 2018 by XLjedi

[Pecan]

20 hours ago, Interstellar Yeet said:

 Thanks! But yeah it was hell. I was designing planes for 3 days, ragequit for 2 days, then the day after i managed to build a plane that can land on duna and return. Worth it, haha. 

EDIT: Just hope 2700 delta V is enough to get home :O I'm still landed on Duna since I am busy doing stuff

Should be enough, especially since your re-entry/aerobraking at Kerbin will save a load.  "Officially" (dV maps) it's a 2,300 m/s trip.

By the way, I really understand the "3 days, ragequit 2 days, then the day after I managed ...".  A lot of things go like that in KSP (rendezvous, docking, etc) but (space)planes especially.  Like the other things they take practice and then it suddenly all falls into place (instead of falling apart).  The best news is that once you do 'get it' with designing planes there's a lot you can do very quickly.

[AeroGav]

On 11/10/2018 at 7:18 AM, Interstellar Yeet said:

Okay so I've tried for 2 days straight to land a plane on duna. I can build a plane that has a really good balance of center of mass and center of lift both with full fuel and no fuel, I can get to orbit, I can get to duna even with a 250 ton Mark 3 cargo plane that needs to orbit kerbin 3 times to even get out of its SOI and over to duna. And I can also land on kerbin. However, I CAN'T land on Duna. There's just no way, and it feels like I never will. I can't even control the plane anywhere near duna. All the way from kerbin over to duna is completely fine, takes a bit of time to turn the giant ass plane sure, but near Duna its impossible. The problems start when i get around like 50k or something around there. From that point on I just can't turn the plane around in less than a really long time, and once I start turning I just keep turning the same way forever, I can't stop it. And once I reach 30k in the atmosphere the plane just goes wild and starts spinning everywhere uncontrollably. I've watched every tutorial I could find, even videos that aren't tutorials just to see what they are doing, I've downloaded countless of Duna planes just to cheat them over to duna and try to land, I've tried with full fuel, no fuel, some fuel here and there, balance things out, but same thing every time. Spin spin spin forever. I'm at a loss of words and action, I've got no clue what to do. I've never been more angry at a game than right now. Sure the 2 first days I played was a bit hard and I managed to land on the Mun and Minmus, rendezvous and even dock fairly easily, but this is just (excuse my profanity) dumb. This community has been very welcoming and helpful since the day I made my account, so anybody, please teach me the ways of SSTO's I beg you ;-; 

So, TLDR; How the frick do you land a SSTO on Duna. I must be missing something. Do I need a ton of reaction wheels and RCS thrusters everywhere? Or is it my angle of approach that is wrong, idk. Someone please help me. I refuse to send a rocket there, once I saw all these crazy SSTO videos on youtube I fell in love with the game for the second time and I probably won't use a rocket again, unless I have to. I love building these planes, and I love flying them. Sorry if I seem really salty, cus I am. LOL 

 

EDIT: https://imgur.com/a/h1lOvbV 

Album here of the crafts I've tried so far, I'll try to see if I can find more but I think i deleted most of those I've failed with. 

EDIT 2: https://www.dropbox.com/s/15ayu33jqe2mngh/Lynni.sfs?dl=0 Here's a savefile as well

I'll take a look at your craft in a minute,   but if you want  a rolling horizontal landing on Duna you're going to need to employ at least two of the following methods.   Three is better,  and all four is best of all

• MOAR WING.            Duna's thin atmosphere means landing speeds are just over double what they are on Kerbin, despite the low gravity.   Your spaceplane needs to be able to land on Kerbin at less than 35m/s even if you're using brake chutes and lift thrusters.   I did have a super STOL SSTO that had very strong landing gear and a stall speed of 20 m/s on Kerbin that was able to set down down on Duna without using thrusters or parachutes,  but 30-35 is a more realistic goal.            Note,  the extra wing area can make it harder to milk top speed out of your air breathing engines, because it will generate so much lift it wants to zoom to such high altitudes they can't produce thrust, before the jet engines hit their design top speed.     OTOH,   those extra wings make good fuel tanks for NERV engines and will give a really high lift/drag ratio in the upper atmosphere once the jets quit.      So,   spam big S wing parts, don't use any fuselage liquid fuel tanks, keep all your fuel in the massive wings.   The only oxidizer you bring should be for the Vernor thrusters.
• VERNOR THRUSTERS.    One downward firing Vernor per 10 tons of weight is enough to halve your landing speed on Duna, thanks to the low grav.  If you have a lot of vernors,  it might be worth putting them in a service bay so they don't cause drag on the climb out of Kerbin.
• MOAR LEGZ.   The basic tricycle landing gear setup is not very stable.    Craft self disassembly usually results from the plane getting sideways then rolling,  or  the nose, wingtip or tail striking the ground.        Consider a 5 leg setup.  Office chairs in the EU have to have 5 legs for a reason !     One nose gear for steering.        Fit a pair on the main wing not far behind the Center of Mass but as far out towards the wing tips as possible (prevent wing tip dig in).   Finally,  mount a pair on the rear fuselage close together to prevent tail strike.     The rear pair should have friction control turned way up ,  the nose gear have friction way down.   Why two rear legs when they are so close together, and why tweak friction ?   For the same reason that (most) cars are engineered for understeer ,  the back end should have much more grip than the front,  that way it wants to plough straight on rather than spin out or get sideways.
• DRAG Chutes.     Popping a drag chute on touchdown makes a successful landing more likely for two reasons.   The main one is that all this drag at the back end keeps the plane going prograde  and makes it less likely to skid sideways and flip if a wheel hits a bump.   The minor reason is that it stops you quicker, so you are less likely to encounter a bump in the first place.

[AeroGav]

One slightly unrelated point to add as a fifth tip  - CRASH TEST.

Your airplane should have a combo of resilience, crumple zone and low landing speed such that you can fly your SSTO at stalling speed into the side of the VAB.   The building should collapse but everyone on the SSTO should walk away.  If this is the case,  your little guys are in with a shout..

A 5 leg landing gear design, an extra vernier thruster or some braking chutes would have made this thing easier to put down...

[Interstellar Yeet]

12 hours ago, AeroGav said:

I'll take a look at your craft in a minute,   but if you want  a rolling horizontal landing on Duna you're going to need to employ at least two of the following methods.   Three is better,  and all four is best of all

• MOAR WING.            Duna's thin atmosphere means landing speeds are just over double what they are on Kerbin, despite the low gravity.   Your spaceplane needs to be able to land on Kerbin at less than 35m/s even if you're using brake chutes and lift thrusters.   I did have a super STOL SSTO that had very strong landing gear and a stall speed of 20 m/s on Kerbin that was able to set down down on Duna without using thrusters or parachutes,  but 30-35 is a more realistic goal.            Note,  the extra wing area can make it harder to milk top speed out of your air breathing engines, because it will generate so much lift it wants to zoom to such high altitudes they can't produce thrust, before the jet engines hit their design top speed.     OTOH,   those extra wings make good fuel tanks for NERV engines and will give a really high lift/drag ratio in the upper atmosphere once the jets quit.      So,   spam big S wing parts, don't use any fuselage liquid fuel tanks, keep all your fuel in the massive wings.   The only oxidizer you bring should be for the Vernor thrusters.
• VERNOR THRUSTERS.    One downward firing Vernor per 10 tons of weight is enough to halve your landing speed on Duna, thanks to the low grav.  If you have a lot of vernors,  it might be worth putting them in a service bay so they don't cause drag on the climb out of Kerbin.
• MOAR LEGZ.   The basic tricycle landing gear setup is not very stable.    Craft self disassembly usually results from the plane getting sideways then rolling,  or  the nose, wingtip or tail striking the ground.        Consider a 5 leg setup.  Office chairs in the EU have to have 5 legs for a reason !     One nose gear for steering.        Fit a pair on the main wing not far behind the Center of Mass but as far out towards the wing tips as possible (prevent wing tip dig in).   Finally,  mount a pair on the rear fuselage close together to prevent tail strike.     The rear pair should have friction control turned way up ,  the nose gear have friction way down.   Why two rear legs when they are so close together, and why tweak friction ?   For the same reason that (most) cars are engineered for understeer ,  the back end should have much more grip than the front,  that way it wants to plough straight on rather than spin out or get sideways.
• DRAG Chutes.     Popping a drag chute on touchdown makes a successful landing more likely for two reasons.   The main one is that all this drag at the back end keeps the plane going prograde  and makes it less likely to skid sideways and flip if a wheel hits a bump.   The minor reason is that it stops you quicker, so you are less likely to encounter a bump in the first place.

I managed to land my plane the way it is in the file. Only thing I did is I pulled the NERV fuel tanks a bit up and the lower wing too so that they wouldn't crash as easy into the ground, and I also pulled the landing gear a bit down. I popped my 2 chutes first at landing, then the 3 other chutes, then I sailed away for a pretty long time and jumped 2-3 times until I had finally stopped. Took me bloody 2 and a half hours to land that thing!

 

https://imgur.com/a/JlYaq4F is 2700 delta V enough to bring this bad boy home? 

Edited November 13, 2018 by Interstellar Yeet

[KerikBalm]

I do 100+ ton payloads to orbit in SSTOs with 40%+ payload fractions...

I do mk3 cargobay shuttles that can take modules down to the surface of duna and back up to build and relocate surface bases.

I did a SSTO and duna back just once... no thank you... not worth it. Single Stage To Orbit is worth it... Single Stage To Duna is not.

I would much rather have an SSTO carry a lander that detaches, than to try and land a Kerbin SSTO on Duna.

If you insist, you'll want: breaking parachutes, because its low gravity and rough terrain. Trying to keep a plane stable as it barrels over uneven ground at >100 m/s is not my cup of tea...

better yet: retro rockets

Better yet: hover rockets

Other good options are tail sitter designs with parachutes at the front so landing on the tail is super easy. That requires a lot of thrust to take off on kerbin (at least 1/8th of your wet mass would be engines if you do a vertical takeoff on jet thrust alone), but you'll then have a super easy time breaking mach 1. Alternately you can make some tail sitter designs that can also take off vertically on kerbin.

 

As to the turning radius... that air is thin... Duna may be low gravity, but inertia doesn't depend on gravity. To go from going 500 m/s east to 500 m/s north (a 90 degree turn) in even 30 seconds (3 degrees per second), requires an acceleration of at least 23.5 m/s.

High flying speeds (due to lower atmospheric density) = more change in velocity needed to turn

lower atmospheric density = lower forces generates by wings = much longer turning times.

Try to turn to fast (using RCS or reaction wheel torque), and you AoA will be way to high, stuff stalls, center of drag shifts... losing control is a possibility.

Keep your AoA low.