Help me improve with planes

[king of nowhere]

After doing pretty much everything else, I decided to try an eve ssto (actually not for eve but some similar modded planets, not important anyway; basically, I have to optimize a model).

unfortunately, if there is one aspect of this game that I never mastered, it's planes. Oh, I can fly, I made a few neat propeller-rocket models, but nothing special. I can make a propeller rocket plane that can ssto on kerbin, but eve is another matter entirely.

Anyway, I've seen a few eve ssto, in particular this model used for a single stage grand tour that can ssto on eve with enough fuel left to land on gilly, while carrying mining equipment. I would not copy other's designs (where's the fun in that?), but I have a solid base to start. I certainly wasn't expecting my first experiment to go ssto, or even to get particularly close. But I was at least expecting it to fly. Nope.

this is the plane. 226 tons, more mass should help reduce drag by the square cube law, the working models I've seen are all around 200 tons. 10 wings, it's more than other models I saw, I actually added some because I could not take off. I haven't yet placed the nuclear engines, that will come later - if I can make this work, which is doubtful at this point.

on the airstrip, at low speed, propellers are generating a lot of thrust. so far so good.

but around 100 m/s, I mostly stop accelerating. I can't tell how much is drag and how much the propellers lose power; I know it's easy enough to reach 200 m/s with propellers, so I must assume the plane is making drag

the plane can lift off, but it lost speed

here it recovered a bit, but it's still slower than when it took off. and I can't accelerate it

the plane is very unstable during flight, it tends to pitch down hard unless I correct for it constantly. of course, this causes the plane to have a sinusoidal movement that greatly increases drag. additionally, the plane has a lot of trouble generating lift; I have to point the nose upwards of prograde if I want to stay in the air, else I fall down fast. And I already used 5° angle of attack - I'd have tried for less, but as I said, I wasn't getting enough lift. From what I heard, successful models use lower angles of attack and less wings per mass unit, but I already had a hard enough time getting this design to take off, and I can't imagine what it would take to get it to land in one piece.

The plane is incapable to ascend at more than a few m/s, and it is incapable of going faster than 100 m/s.

the design is very basic, and very similar to other successful planes. yet it barely stays in the air. and I can't tell the difference between this model and others that work.

anyone can enlighten me?

 

 

 

[Lt_Duckweed]

2 hours ago, Dunas Only Moon said:

1. I know R.A.P.I.E.R's dont work on eve and they are for takeoffs only.

Adding rapiers to an Eve ssto for Kerbin takeoff is pointless dead mass and makes ssto'ing off Eve essentially impossible.

2 hours ago, Dunas Only Moon said:

2. Yes... i know about you wanting to test propellors but they will not and cannot takeoff on their own. 

Wrong.  Propellers can get a craft airborne on Kerbin and Eve just fine.  All sea level Eve sstos using breaking ground take off using propellers.

2 hours ago, Dunas Only Moon said:

3. if you want atmospheric flight, use nuclear engines and MAYBE propellors. Dont use propellors for takeoff on eve.

Wrong.  You need propellers to get up to the altitude where your engines will get good thrust and ISP.   You don't even ignite your engines until past 15km.

 

@king of nowhere  the main problems I am seeing with your craft are this:
1. Not enough prop blades.  You have 16 total, 8 per rotor.  At this mass you need to be using about 32 total.  You can do that via 4 rotors with 8 blades each, or if you offset the prop blade base one tick past the axis of rotation (so that the base is on the other side of the axis from the rest of the rotor) you will need substantially less torque and thus can do 16 blades per rotor, but with this setup you have to be very careful as if the blades stall they will kraken. (This setup also makes the prop compact enough to shield in a 1.25m service bay, though it looks a bit clippy so you have to decide if that is something you are ok with).

2. Too much engine mass.  Margins on Eve sstos are very tight, for a craft of this size you should be looking at ~2 vectors, meaning you are carrying 7 tons of dead mass.   Swapping to 2 vectors also means you can mid mount them, so that their dry mass is in line with the CoM and thus does not drag the CoM around as fuel drains.

3. Props too far forwards.  Eve sstos, in order to not carry too much wing into the rocket phase of ascent (and therefore climb too rapidly) are under winged and therefore must adopt substantial angle of attack through the upper prop phase of Eve ascent or on Kerbin takeoff.  This means the props are crabbing through the air at an angle, which causes all sorts of issues thanks to them being very far from the CoM.  Move the props to mid mounted side pylons (or do one fore and one aft to cancel each other's stability effects).  Additionally, I angle my props downwards 5 degrees on my Eve sstos, to better match the AoA in upper Eve ascent (this makes it even more important to mount them at the CoM, so the thrust axis points through the CoM)

4. CoL too far backwards.  Your CoL being substantially behind the CoM means that you have to actively fight the craft to get the nose up AoA for upper Eve prop phase, and for Kerbin takeoff.  You want your at rest CoL lightly ahead of your CoM, which you do by mounting your main wing slightly forward of your CoM.  Doesn't have to be much, just a couple of ticks.  Then to counter the resultant instability this would otherwise produce, you place your horizontal stabilizers as far aft as you can, and with 0 wing incidence.  This means that when you pitch up, the horizontal stabilizers will gain lift proportionately faster than the main wing, since the main wing has angle of incidence already built in (wing lift is ~linear up to about 15-20 degrees AoA, so a pitch up from say 5 AoA to 10 AoA would have the main wing go from 5+5 AoA to 5+10 AoA for 50% more lift, but the horizontal stabilizer would go from 0+5 AoA to 0+10 AoA, for 100% more lift).  This results in the CoL sliding backwards as you pitch up, providing stability, just at a non 0 pitch up AoA.   This makes it much much easier to fly at a non 0 AoA as it won't fight you nearly as much, and it means the craft can adopt a substantially higher AoA on reentry since the passive stability will not be fighting nearly as hard to revert to 0 AoA.

Edited February 21 by Lt_Duckweed

[Dunas Only Moon]

Hi again. So technicaly there are many problems.
1. Bad wings: There are many wings you can use, also, dont refrain from using the move/rotate tool.

2. Weak engines: You have too weak engines and if i were you i would add some rapiers using a radial attachment point or a bi-coupler, also try making it smaller and adding nuclear engines/mining posts to increase range.

3. Lose some weight: Use cargo bays and try using more efficient engines with maybe, just maybe, some mining equipment, try adding radiators.

FYI: I dont speak spanish, and i am on the PS4 too, i hope this helped!

 

[king of nowhere]

58 minutes ago, Dunas Only Moon said:

Hi again. So technicaly there are many problems.
1. Bad wings: There are many wings you can use, also, dont refrain from using the move/rotate tool.

2. Weak engines: You have too weak engines and if i were you i would add some rapiers using a radial attachment point or a bi-coupler, also try making it smaller and adding nuclear engines/mining posts to increase range.

 

...

are you aware that on eve rapiers don't work?

did you read that I'm not concerned about that atm, I am only testing the propellers so far?

Quote

 

3. Lose some weight: Use cargo bays and try using more efficient engines with maybe, just maybe, some mining equipment, try adding radiators.

FYI: I dont speak spanish, and i am on the PS4 too, i hope this helped!

 

i also mentioned that other stuff will be added later, once propeller flight works as intended.

i believe you completely misunderstood everything about my post

[Leganeski]

9 hours ago, king of nowhere said:

I'm not an expert on large propeller planes, but that doesn't look like enough propeller blade area for such a heavy plane.

I would bring the CoL even closer to the CoM so that it doesn't pitch down as much, and add more control surface area in the pitch direction if that would help the plane steer better.

9 hours ago, king of nowhere said:

but around 100 m/s, I mostly stop accelerating. I can't tell how much is drag and how much the propellers lose power;

Propeller blades quickly lose thrust as the airspeed of the blade rises above Mach 1. This means that to reach higher speeds, the blade orientation should be brought closer to forward-backward by changing the deploy angle, rather than increasing the RPM. It looks like you might already be doing this, though, which makes me think that the propellers need to be more powerful.

 

[Dunas Only Moon]

19 hours ago, king of nowhere said:

...

are you aware that on eve rapiers don't work?

did you read that I'm not concerned about that atm, I am only testing the propellers so far?

i also mentioned that other stuff will be added later, once propeller flight works as intended.

i believe you completely misunderstood everything about my post

Ok... 
1. I know R.A.P.I.E.R's dont work on eve and they are for takeoffs only.
2. Yes... i know about you wanting to test propellors but they will not and cannot fly on their own. 
3. if you want atmospheric flight, use nuclear engines and MAYBE propellors. Dont use propellors for takeoff on eve as they will barely fly you upwards.

Edited February 21 by Dunas Only Moon
Usefull stuff

[king of nowhere]

22 hours ago, Lt_Duckweed said:

Adding rapiers to an Eve ssto for Kerbin takeoff is pointless dead mass and makes ssto'ing off Eve essentially impossible.

Wrong.  Propellers can get a craft airborne on Kerbin and Eve just fine.  All sea level Eve sstos using breaking ground take off using propellers.

Wrong.  You need propellers to get up to the altitude where your engines will get good thrust and ISP.   You don't even ignite your engines until past 15km.

 

@king of nowhere  the main problems I am seeing with your craft are this:
1. Not enough prop blades.  You have 16 total, 8 per rotor.  At this mass you need to be using about 32 total.  You can do that via 4 rotors with 8 blades each, or if you offset the prop blade base one tick past the axis of rotation (so that the base is on the other side of the axis from the rest of the rotor) you will need substantially less torque and thus can do 16 blades per rotor, but with this setup you have to be very careful as if the blades stall they will kraken. (This setup also makes the prop compact enough to shield in a 1.25m service bay, though it looks a bit clippy so you have to decide if that is something you are ok with).

I do have 32. It doesn't show well in the picture, but each of those service bays has 2 rotors, each with 8 blades.

Quote

 

2. Too much engine mass.  Margins on Eve sstos are very tight, for a craft of this size you should be looking at ~2 vectors, meaning you are carrying 7 tons of dead mass.   Swapping to 2 vectors also means you can mid mount them, so that their dry mass is in line with the CoM and thus does not drag the CoM around as fuel drains.

 

ok. though it doesn't affect the poor flight performance the plane currently has

Quote

 

3. Props too far forwards.  Eve sstos, in order to not carry too much wing into the rocket phase of ascent (and therefore climb too rapidly) are under winged and therefore must adopt substantial angle of attack through the upper prop phase of Eve ascent or on Kerbin takeoff.  This means the props are crabbing through the air at an angle, which causes all sorts of issues thanks to them being very far from the CoM.  Move the props to mid mounted side pylons (or do one fore and one aft to cancel each other's stability effects).  Additionally, I angle my props downwards 5 degrees on my Eve sstos, to better match the AoA in upper Eve ascent (this makes it even more important to mount them at the CoM, so the thrust axis points through the CoM)

 

 

Interesting. so I am actually supposed to have to point the nose above prograde at kerbin's atmospheric pressure.

I don't understand how that causes issues with the center of mass, but i'll take your word for it.

Quote

4. CoL too far backwards.  Your CoL being substantially behind the CoM means that you have to actively fight the craft to get the nose up AoA for upper Eve prop phase, and for Kerbin takeoff.  You want your at rest CoL lightly ahead of your CoM, which you do by mounting your main wing slightly forward of your CoM.  Doesn't have to be much, just a couple of ticks.  Then to counter the resultant instability this would otherwise produce, you place your horizontal stabilizers as far aft as you can, and with 0 wing incidence.  This means that when you pitch up, the horizontal stabilizers will gain lift proportionately faster than the main wing, since the main wing has angle of incidence already built in (wing lift is ~linear up to about 15-20 degrees AoA, so a pitch up from say 5 AoA to 10 AoA would have the main wing go from 5+5 AoA to 5+10 AoA for 50% more lift, but the horizontal stabilizer would go from 0+5 AoA to 0+10 AoA, for 100% more lift).  This results in the CoL sliding backwards as you pitch up, providing stability, just at a non 0 pitch up AoA.   This makes it much much easier to fly at a non 0 AoA as it won't fight you nearly as much, and it means the craft can adopt a substantially higher AoA on reentry since the passive stability will not be fighting nearly as hard to revert to 0 AoA.

weird, I'm no plane expert but I know that you generally want CoL behind CoM.

And I also suppose the plane is intended to fly poorly at normal atmospheric pressure; it's only supposed to fly in those conditions for a short time, pushing up as much as it can before using rockets.

also, when using rockets my first instinct is to get out of the atmosphere fast, but since I'll have low twr with two vectors, I guess I am supposed to keep flying horizontal - or nearly horizontal - for a while more, until the wings gain more lift, and let the plane be pushed upwards solely by lift from the wings until I am... what? 30k meters?

Will give it a try.

 

I'm still puzzled as to why this experimental model would fly so poorly, while an older plane I did (dubbed Arrowhead) had roughly one fourth of the mass, one fourth of the wing surface, one fourth of the propeller power, and it worked very well on kerbin and laythe despite many more sources of drag. but it's not really important at this point. (edit: I went to reread the relevant mission report, turned out that spaceplane also had limited speed and maneuverability at standard pressure, so perhaps it's consistent)

Edited February 22 by king of nowhere

[Lt_Duckweed]

1 hour ago, king of nowhere said:

I do have 32. It doesn't show well in the picture, but each of those service bays has 2 rotors, each with 8 blades.

ah, in that case, can you detail how you have the rotors and props setup in terms of torque, rpm and blade angle?

I always run the props at max rpm, and adjust the prop angle such that the prop AoA is 4.5 degrees, or the highest AoA that can be used before the prop rpm starts dropping, whichever happens first. (In thick atmosphere you will have to run a lower AoA to maintain full rpm, as you are torque limited.  In thinner atmosphere you can run 4.5 degrees, which gives maximum thrust, at max rpm, as you are rpm limited, not torque limited)

Edited February 22 by Lt_Duckweed

[king of nowhere]

42 minutes ago, Lt_Duckweed said:

ah, in that case, can you detail how you have the rotors and props setup in terms of torque, rpm and blade angle?

as you can see, i keep the aerodinamic window open while flying, and I check drag (resistenza totale in my italian interface). the kal controller sets blade angle, I just move it up and down until I find the value that gives me the most negative drag, and I keep adjusting during flight. people talk about angle of attack on the propellers, I guess they are using mods to show it, I don't so trying to calculate it according to air speed and blade speed would be too complicated.

max rpm is defaulted at maximum, though I had prepared a second kal controller to balance that too - I discovered that in dense atmospheres I can get better performance by reducing rpm, though maybe that just happens because the propeller itself is not powerful enough to reach it anyway, so lowering the value to something the propeller can sustain improves stability. anyway, this is just prelimitary testing and I wasn't yet using that. I also considered reducing maximum torque for parts of the ascent to conserve electricity, but again, preliminary testing, so far I just want to have a plane that flies reasonably at standard pressure and up to half an atmosphere. if it can do that on kerbin, it can generally reach 15 km on eve.

 

so, tl dr, I keep torque and rpm at maximum, and I regulate blade angle with the kal controller by experimentally picking the value that will give me the best negative drag

EDIT: when the plane is standing still, I get -1000 kN of drag, so that's about the power of the propellers. as speed goes up, that number goes down, and I have no way of knowing how much of that is due to reduced propeller power, and how much is due to actual drag rising. when I take off at about 100 m/s, total drag is around 0 to 200 kN depending on angle of ascent. I suppose the wings must generate a lot of drag to lift a 200-ton plane anyway

Edited February 22 by king of nowhere

[Leganeski]

57 minutes ago, king of nowhere said:

I keep adjusting during flight. people talk about angle of attack on the propellers, I guess they are using mods to show it

If you right-click on a propeller blade during flight, it will show the blade's angle of attack along with other statistics such as how much lift that blade is producing. This works without any mods, although I don't remember whether it requires enabling some setting like advanced tweakables.

1 hour ago, king of nowhere said:

I discovered that in dense atmospheres I can get better performance by reducing rpm,

I've observed this as well. It appears to be caused by the propeller blades passing the speed of sound, rather than the atmosphere being too dense, because it remains a problem even at high altitudes. In a cold atmosphere like Tekto where the speed of sound is low (~200 m/s), this can be a significant concern. In hotter atmospheres where where the speed of sound is faster, like Eve (~300 m/s) or especially Imterril (~550 m/s), the 460 rpm limit is a much more relevant issue.

The average molar mass and adiabatic index (but not pressure) also affect the speed of sound, so even cold hydrogen-helium atmospheres generally don't have this problem.

[Lt_Duckweed]

4 hours ago, Leganeski said:

I've observed this as well. It appears to be caused by the propeller blades passing the speed of sound, rather than the atmosphere being too dense, because it remains a problem even at high altitudes. In a cold atmosphere like Tekto where the speed of sound is low (~200 m/s), this can be a significant concern. In hotter atmospheres where where the speed of sound is faster, like Eve (~300 m/s) or especially Imterril (~550 m/s), the 460 rpm limit is a much more relevant issue.

The average molar mass and adiabatic index (but not pressure) also affect the speed of sound, so even cold hydrogen-helium atmospheres generally don't have this problem.

I've noticed that this is actually an issue at high altitude on Eve since the temp drops sharply with altitude, but for the speeds an Eve ssto reaches before turning on engines, it's a pretty minor gain for a lot of pain babysitting the prop rpm, so it's easier to just let it rip.

[Dunas Only Moon]

On 2/20/2023 at 4:48 PM, king of nowhere said:

After doing pretty much everything else, I decided to try an eve ssto (actually not for eve but some similar modded planets, not important anyway; basically, I have to optimize a model).

unfortunately, if there is one aspect of this game that I never mastered, it's planes. Oh, I can fly, I made a few neat propeller-rocket models, but nothing special. I can make a propeller rocket plane that can ssto on kerbin, but eve is another matter entirely.

Anyway, I've seen a few eve ssto, in particular this model used for a single stage grand tour that can ssto on eve with enough fuel left to land on gilly, while carrying mining equipment. I would not copy other's designs (where's the fun in that?), but I have a solid base to start. I certainly wasn't expecting my first experiment to go ssto, or even to get particularly close. But I was at least expecting it to fly. Nope.

this is the plane. 226 tons, more mass should help reduce drag by the square cube law, the working models I've seen are all around 200 tons. 10 wings, it's more than other models I saw, I actually added some because I could not take off. I haven't yet placed the nuclear engines, that will come later - if I can make this work, which is doubtful at this point.

on the airstrip, at low speed, propellers are generating a lot of thrust. so far so good.

but around 100 m/s, I mostly stop accelerating. I can't tell how much is drag and how much the propellers lose power; I know it's easy enough to reach 200 m/s with propellers, so I must assume the plane is making drag

the plane can lift off, but it lost speed

here it recovered a bit, but it's still slower than when it took off. and I can't accelerate it

the plane is very unstable during flight, it tends to pitch down hard unless I correct for it constantly. of course, this causes the plane to have a sinusoidal movement that greatly increases drag. additionally, the plane has a lot of trouble generating lift; I have to point the nose upwards of prograde if I want to stay in the air, else I fall down fast. And I already used 5° angle of attack - I'd have tried for less, but as I said, I wasn't getting enough lift. From what I heard, successful models use lower angles of attack and less wings per mass unit, but I already had a hard enough time getting this design to take off, and I can't imagine what it would take to get it to land in one piece.

The plane is incapable to ascend at more than a few m/s, and it is incapable of going faster than 100 m/s.

the design is very basic, and very similar to other successful planes. yet it barely stays in the air. and I can't tell the difference between this model and others that work.

anyone can enlighten me?

 

 

 

OK i have to say this... More wings, more blades, and last but not least... less drag. try using a shroud as a nose

[king of nowhere]

On 2/21/2023 at 8:16 PM, Lt_Duckweed said:

Adding rapiers to an Eve ssto for Kerbin takeoff is pointless dead mass and makes ssto'ing off Eve essentially impossible.

Wrong.  Propellers can get a craft airborne on Kerbin and Eve just fine.  All sea level Eve sstos using breaking ground take off using propellers.

Wrong.  You need propellers to get up to the altitude where your engines will get good thrust and ISP.   You don't even ignite your engines until past 15km.

 

@king of nowhere  the main problems I am seeing with your craft are this:
1. Not enough prop blades.  You have 16 total, 8 per rotor.  At this mass you need to be using about 32 total.  You can do that via 4 rotors with 8 blades each, or if you offset the prop blade base one tick past the axis of rotation (so that the base is on the other side of the axis from the rest of the rotor) you will need substantially less torque and thus can do 16 blades per rotor, but with this setup you have to be very careful as if the blades stall they will kraken. (This setup also makes the prop compact enough to shield in a 1.25m service bay, though it looks a bit clippy so you have to decide if that is something you are ok with).

2. Too much engine mass.  Margins on Eve sstos are very tight, for a craft of this size you should be looking at ~2 vectors, meaning you are carrying 7 tons of dead mass.   Swapping to 2 vectors also means you can mid mount them, so that their dry mass is in line with the CoM and thus does not drag the CoM around as fuel drains.

3. Props too far forwards.  Eve sstos, in order to not carry too much wing into the rocket phase of ascent (and therefore climb too rapidly) are under winged and therefore must adopt substantial angle of attack through the upper prop phase of Eve ascent or on Kerbin takeoff.  This means the props are crabbing through the air at an angle, which causes all sorts of issues thanks to them being very far from the CoM.  Move the props to mid mounted side pylons (or do one fore and one aft to cancel each other's stability effects).  Additionally, I angle my props downwards 5 degrees on my Eve sstos, to better match the AoA in upper Eve ascent (this makes it even more important to mount them at the CoM, so the thrust axis points through the CoM)

4. CoL too far backwards.  Your CoL being substantially behind the CoM means that you have to actively fight the craft to get the nose up AoA for upper Eve prop phase, and for Kerbin takeoff.  You want your at rest CoL lightly ahead of your CoM, which you do by mounting your main wing slightly forward of your CoM.  Doesn't have to be much, just a couple of ticks.  Then to counter the resultant instability this would otherwise produce, you place your horizontal stabilizers as far aft as you can, and with 0 wing incidence.  This means that when you pitch up, the horizontal stabilizers will gain lift proportionately faster than the main wing, since the main wing has angle of incidence already built in (wing lift is ~linear up to about 15-20 degrees AoA, so a pitch up from say 5 AoA to 10 AoA would have the main wing go from 5+5 AoA to 5+10 AoA for 50% more lift, but the horizontal stabilizer would go from 0+5 AoA to 0+10 AoA, for 100% more lift).  This results in the CoL sliding backwards as you pitch up, providing stability, just at a non 0 pitch up AoA.   This makes it much much easier to fly at a non 0 AoA as it won't fight you nearly as much, and it means the craft can adopt a substantially higher AoA on reentry since the passive stability will not be fighting nearly as hard to revert to 0 AoA.

Ok, it took me a long while to test with this stuff because my life got busy.

I tried your suggestions.

1) as already mentioned, I had 32 blades already. I moved them one at the front and one at the bottom.

2) I now have 2 vectors and 2 nervs; I am sure I'll have to add one or two more nervs, but that can wait; right now, it's important to just get this airborne.

3) I angled the propellers downward 5 degrees as you suggested. I removed a pair of wings, since you mentioned those planes are supposed to be underwinged.

4) I moved the CoL forward as you suggested. I forgot the horizontal stabilizers at first, but I tried them now, didn't help.

So, first model.

the first model at least can take off reliably at the end of the runway, without crashing in the ocean half the times, so I guess that's some progress.

but it starts to pitch up

and up. it flips and crashes.

so I moved the CoL back. one tick at a time, until I had a stable plane. here's what I got.

and it flies, but it stops there. It's barely air-worthy. it does not pick up speed. It does not climb, at least not significantly. and it was slowly losing speed.

in eve's greater gravity, this model wouldn't be able to get past 13 km, while it should reach 15 on propellers alone.

 

As I said, after reading again and realizing that I was missing the aft stabilizers, I tried to install them and move a single wing pair forward by two ticks. Plane tipped up again. I'm still stuck with something that doesn't fly well enough

 

[Vanamonde]

If you're still learning to make planes, why not make something smaller and more manageable?

[king of nowhere]

1 hour ago, Vanamonde said:

If you're still learning to make planes, why not make something smaller and more manageable?

a legit question, with a moltitude of answers.

because I don't like making planes. but I have an idea to try a fully reusable whirligig world grand tour, and that mod has 2 eve-like planets.

because I am already capable of making decent planes, and I seem to have hit a wall when it comes to improve there.

because I can easily value the performance of a spaceship and where it is lacking (too much dry mass, too few electricity, too few reaction wheels...), but I don't even know where to start in valuing the performance of a plane (wing angle? propeller power? center of mass? maybe the plane is fine but my flight profile is wrong?). and without being able to value performance, I can't improve.

because starting with something smaller and more manageable is boring.

But even accepting to make something smaller and going incremental? I already have several propeller planes that can ssto from kerbin with considerable payloads, despite sacrificing a lot of performance to luxuries like good iva view or fancy add-ons. the next logical step is eve. and I already had a model that could reach 13 km on propellers, then it could not orbit. I got the feeling that if only I could improve flight performance a little bit and gain a couple more km of elevation, ssto would be within my grasp.

also, because making planes in general doesn't seem to apply much to making something capable of eve ssto. stuff like angling the propellers or putting the CoM behind the CoL goes against the basics I knew of planes. and I am keeping the same mass/wing ratio that worked on smaller planes, but this time it's not working.

but perhaps more to the point, I am actually doing exactly that: something simpler and more manageable. So far, what I am trying to make is a plane that's 4 times heavier than my previous heavier model, that has similar wing and propeller ratios, and that flies. And I'm stumped, because I'm doing all the stuff that worked to make smaller planes, and it's not working anymore. I'm not even worrying about rocket flight so far, those rockets are only there to simulate the mass.

EDIT: I mean, this is Arrowhead, possibly my most successful spaceplane

it has a mass of 50 tons, its propellers generate 200 kN of thrust, it's got 4 wings, it flies easily on kerbin - though it's not very maneuverable. It reaches 7-8 km before needing the rockets, and it carries to orbit its dry mass of 20 tons, plus a bunch of spare fuel, so it's got almost 50% mass ratio to orbit. Despite using draggy Mk2 parts (I needed them for kerbalism reasons) and having that docking port on top and a similar one on the bottom interfering with a smooth flight.

As first step, I tried to make a plane that was 4-5 times heavier, I gave it 1000 kN of propeller thrust, 16 wings before I got talked into reducing them, and I streamlined everything to remove all the inefficiences arrowhead had. I fully expected to get something that would fly better. Instead I got something that can barely manage level flight at sea level, and I have no idea why.

 

I may have underestimated the task, but really, given that I've already taken all the steps before, what else could I do as practice?

Edited March 4 by king of nowhere

[Dunas Only Moon]

On 3/4/2023 at 2:51 PM, king of nowhere said:

a legit question, with a moltitude of answers.

because I don't like making planes. but I have an idea to try a fully reusable whirligig world grand tour, and that mod has 2 eve-like planets.

because I am already capable of making decent planes, and I seem to have hit a wall when it comes to improve there.

because I can easily value the performance of a spaceship and where it is lacking (too much dry mass, too few electricity, too few reaction wheels...), but I don't even know where to start in valuing the performance of a plane (wing angle? propeller power? center of mass? maybe the plane is fine but my flight profile is wrong?). and without being able to value performance, I can't improve.

because starting with something smaller and more manageable is boring.

But even accepting to make something smaller and going incremental? I already have several propeller planes that can ssto from kerbin with considerable payloads, despite sacrificing a lot of performance to luxuries like good iva view or fancy add-ons. the next logical step is eve. and I already had a model that could reach 13 km on propellers, then it could not orbit. I got the feeling that if only I could improve flight performance a little bit and gain a couple more km of elevation, ssto would be within my grasp.

also, because making planes in general doesn't seem to apply much to making something capable of eve ssto. stuff like angling the propellers or putting the CoM behind the CoL goes against the basics I knew of planes. and I am keeping the same mass/wing ratio that worked on smaller planes, but this time it's not working.

but perhaps more to the point, I am actually doing exactly that: something simpler and more manageable. So far, what I am trying to make is a plane that's 4 times heavier than my previous heavier model, that has similar wing and propeller ratios, and that flies. And I'm stumped, because I'm doing all the stuff that worked to make smaller planes, and it's not working anymore. I'm not even worrying about rocket flight so far, those rockets are only there to simulate the mass.

EDIT: I mean, this is Arrowhead, possibly my most successful spaceplane

it has a mass of 50 tons, its propellers generate 200 kN of thrust, it's got 4 wings, it flies easily on kerbin - though it's not very maneuverable. It reaches 7-8 km before needing the rockets, and it carries to orbit its dry mass of 20 tons, plus a bunch of spare fuel, so it's got almost 50% mass ratio to orbit. Despite using draggy Mk2 parts (I needed them for kerbalism reasons) and having that docking port on top and a similar one on the bottom interfering with a smooth flight.

As first step, I tried to make a plane that was 4-5 times heavier, I gave it 1000 kN of propeller thrust, 16 wings before I got talked into reducing them, and I streamlined everything to remove all the inefficiences arrowhead had. I fully expected to get something that would fly better. Instead I got something that can barely manage level flight at sea level, and I have no idea why.

 

I may have underestimated the task, but really, given that I've already taken all the steps before, what else could I do as practice?

Try making ssto's to places like the mun, minmus and my favorite, duna. but make them small, not big like that first one.

im kinda late to this so my apoligies.