slowest plane

[AeroGav]

On 28/05/2016 at 3:59 PM, DualDesertEagle said:

KILLED IT! 5.8 m/s take off speed!

 

I think I've really pushed the limit tho, and this might aswell be disqualified since I'm taking off with well over 50% throttle and at an angle of 30 degrees.

But should this still count, ur gonna have a hard time beating it!

I've really started splitting hair to make it this far! I've taken off really EVERYTHING that wasn't ABSOLUTELY VITAL to make the plane take off, I've switched to an engine that was a whopping 10 grams lighter than the old one, I've joined the wings together in the middle and swapped the retractable gears to non-retracts of the same weight but with streamline housings to improve the aerodynamics, I've increased the dyhedral to have the plane sit on the ground at a higher angle, I've made absolutely sure that the wheels are mouted straight to minimize friction and I've taken half of the fuel out of the tank! This thing probably has the best lift to weight ratio that can be achieved and it's really just designed to take off, then run out of fuel soon after and fall back to the ground. U can't control anything but the throttle and the in this case absolutely useless thrust vectoring.

 

OMG what kind of aerial Winnebago is that supposed to be Eagle?    Think of all the mass you're wasting on that engine, surely  a Separatron or two would do the job?

 

[Cunjo Carl]

Managed a 0m/s! I don't think it qualifies as a plane, though...

I've been tinkering on this challenge for a while, and have found a couple gems for slow takeoff. Applying them may be beyond me, but wish me luck!

Edited May 29, 2016 by Cunjo Carl
Picture upload troubles...

[DualDesertEagle]

1 hour ago, AeroGav said:

OMG what kind of aerial Winnebago is that supposed to be Eagle?    Think of all the mass you're wasting on that engine, surely  a Separatron or two would do the job?

 

And most likely make it hard to find out the actual take-off speed as u can't control that thing.

Also, I think my actual contest entry with its take-off speed of 8.1 m/s is already hard to beat. And if my second one isn't rejected, which I still think is gonna happen, then I sure as hell have issued a pretty tough challenge to every other contestant.

I'll try the sepratron thing tho, maybe u should have instead of telling me about it.

EDIT: Tried it and it's really not worth it. No difference.

Edited May 29, 2016 by DualDesertEagle

[DualDesertEagle]

37 minutes ago, Cunjo Carl said:

Managed a 0m/s! I don't think it qualifies as a plane, though...

I've been tinkering on this challenge for a while, and have found a couple gems for slow takeoff. Applying them may be beyond me, but wish me luck!

That's technically a vertical take off, so I'm pretty sure it's gonna be disqualified.

[Cunjo Carl]

1 hour ago, DualDesertEagle said:

That's technically a vertical take off, so I'm pretty sure it's gonna be disqualified.

Just a joke! It made me laugh so I thought I'd post it. My actual entry is hovering obstinately at 9ish m/s. Fun to fly, though! By the way, you might try AeroGui for ksp1.05 (I noticed you're a user). It tells you lift, upward forces and mass, which'd be an easy way to check out the angle thing if you wanted. Cheers!

[DualDesertEagle]

9 m/s are a pretty good result for someone seemingly getting into stuff like this for the first time. The very first slow plane I experimented with took off at 13.

 

When are u gonna give us some pics or maybe even a video?

[Cunjo Carl]

2 hours ago, DualDesertEagle said:

9 m/s are a pretty good result for someone seemingly getting into stuff like this for the first time. The very first slow plane I experimented with took off at 13.

When are u gonna give us some pics or maybe even a video?

I guess I was being too coy? Your advice got me started and joyous trial and error kept me going. Here's what I've got! The Dragonfly has 300 basic fins in the place of normal wings. Why? Because basic fins (I learned after plumbing through the part config files) have the best lift/mass in the game! Everything else has 10:1 lift:ton, but the basic fin has 12:1.  A 20% improvement isn't much, but it should be enough to go a whole 1m/s slower, dynamic pressure being the puckish force it is. Sadly, my wing to non-wing mass-ratio is pretty gruesome relative to yours, so the advantage is lost, but it's a fun thought! Relative to the bar to beat, the dragonfly flies a blistering 9.5ish m/s.

Also, I mathed out a way to plot the lift curves from the physics.cfg file, and found the optimum angle of attack for lift of 20-22 degrees. This accounts for the fact that higher angles of attack have less vertical component to their lift, which most other sources don't. I posted the technique for plotting KSP's physic's peculiar cubic splines in the "[INFO] KSP floatCurves and you - the magic of tangents"  topic of the addons forum, and it's ultimately pretty easy if anyone's curious to try. You can use it to quantify wing drag, engine thrust curves, all sorts.

Without further ado, behold!

 

Edited May 30, 2016 by Cunjo Carl

[DualDesertEagle]

Great start right there, getting a little nervous that my first entry is gonna get beaten and still don't know if my second one counts...

[Deddly]

5 hours ago, DualDesertEagle said:

still don't know if my second one counts...

Unfortunately, @volcanic_wolf hasn't posted in his thread since 5 April. But looking at the OP, the plane must be able to "completely fly". Based on that, my irrelevant opinion is that your second entry doesn't qualify, since it can only take off.

[DualDesertEagle]

Just now, Deddly said:

Unfortunately, @volcanic_wolf hasn't posted in his thread since 5 April. But looking at the OP, the plane must be able to "completely fly". Based on that, my irrelevant opinion is that your second entry doesn't qualify, since it can only take off.

"completely fly" is a stretchy term here, it could aswell just mean that the plane has to be fully airborne with none of its parts on the ground anymore. But I guess he's the only one who can tell me if it's valid or not.

[volcanic_wolf]

sorry I've been away so long forgot my password but so far dual desert eagle is winning by a mile (3 m/s roughly)

also dualdesertEagle you are fine its valid

 

 

[DualDesertEagle]

YAY!

 

I wonder if it could be beaten tho, anyone willing to try?

Edited June 23, 2016 by DualDesertEagle

[The Thyroid Man]

Maybe I'll put 50,000 wing boards on my plane and have Jeb push it.

[Cunjo Carl]

15 hours ago, The Thyroid Man said:

Maybe I'll put 50,000 wing boards on my plane and have Jeb push it.

I would pay to see this. In funds, of course.

Hm. I think this one's already pushed to its limits on Kerbin. The future lies on Eve, and whichever brave souls decide to take it there.

Beware, math within.

Spoiler

 

Assumptions: Helicopters and flappy planes work on their own principals, but they're against the rules for this challenge, so we can assume a fixed wing. Then we have steadystate flight, fixed mass, low altitude, and a several others assumptions that all jibe well.

Governing Equation: Our governing equation simply says that our lift in the upwards direction must match our weight to fly. From here on, AoA refers to the AoA of your wings, if they happen to differ from your plane's body like they do on mine. Which is weird. Hey, it's cool.
lift*cos(AoA) = mg

How do you calculate lift: "lift coefficient (Cl) then multiplied by the below mach multiplier, dynamic pressure, the wing area, and the global lift multiplier"

Other Substitutions:
Wing lift coeff = 12*mass (this is for the basic fin. Everything else is 10*mass, which is worse)
airDensity = n*MW/V = P*MW/RT
m = massWings + massExtras

Base Equation, followed by substitutions . Putting together the above three sections.
liftAngleCoeff * machMultiplier* .5*airDensity*v^2 * wingLiftCoeff* globalLiftMultiplier * cos(AoA) = (massWings + massExtras)*g
liftAngleCoeff * machMultiplier* .5* P*MW/RT  *v^2 * 12*massWings * globalLiftMultiplier * cos(AoA) = (massWings + massExtras)*g

Solve for velocity, then plug and chug.
v = sqrt[   (1 + massExtras/massWings) *  g   R   T  /(6*liftAngleCoeff*machMultiplier*   P    *   MW  *globalLiftMultiplier*cos(AoA))   ]
v = sqrt[   (1 +     0     /    1    ) * 9.8*8.3*298 /(6*   .857       *      1       * 100194 *.028964*        .036        *  .934  )   ]
units in pascals, kg, K and m. The units won't work out in the equation, because some aspects are based on heuristic.
v = 7-ish m/s (Mileage may vary. Void where prohibited. Manufacturer not responsible for misuse of product.)

Discussion: The formula fits observations within about 10%, which I'm happy with! When actually playing, transient conditions (flappy planes or torque from drag) and bit of downwards thrust can lower the min speed a bit. Ultimately, I'm a happy camper because my theory and experiment have both bean pointing at a 7-ish m/s min speed for the obsessively (and unnecessarily) controlled case with per-tilted wings. I very much like it when theory and experiment agree.

How much does the downwards thrust help? Not much. Here's the math. We're looking for the relative reduction in V for a given change in the mg term.
1 - sqrt[  ( massCraft *  g  - SparkThrust*Throttle*sin(AoA)    )  /  (massCraft * g )  ]
1 - sqrt[  (    2      * 9.8 -     16     *   .7   *sin(30 deg) )  /  (     2    *9.8)  ]
 15ish% improvement . Units in kN, tons.

 

I know, sorry! Who put all this math into ksp . Here's the take homes:

Spoiler

 

The best angle of attack is 21 degrees. It's much better to be a bit high than a bit low. Values in the equation are based on this.

Temp: Your minimum speed will probably be 1.5% slower at night-time relative to mid afternoon. For a given pressure, lower temp means greater air density. 298.2  at just before sunrise ; 308.2  in the early afternoon.

For two otherwise identical craft, the one using basic fins for wings should go 9% slower.

I don't see the gif anymore, but I think DualDesertEagle's case has a massExtras/massWings of about .25 . (4 times more wings than anything else) So that's the number to beat! It's a nice number.

Just using DualDesertEagle's latest as a test case, the downwards thrust will lower the min speed by about 15%. This is well within the bounds of not-worth-caring-about for a fun challenge!

 

Go to Eve
A plane at sea level near Eve 's poles should have a min speed half of that on Kebin! It'll be slightly higher elsewhere because of the higher temps. Someone with their game face on should try it. Beware though, Eve will happily crush your planes with its oppressive gravity, and stifle your rockets with its soupy atmosphere. Hyperedit would probably be a good way to make it out there- landing on Eve is a challenge on its own!

 

Edited June 25, 2016 by Cunjo Carl

[DualDesertEagle]

18 hours ago, Cunjo Carl said:

I would pay to see this. In funds, of course.

Hm. I think this one's already pushed to its limits on Kerbin. The future lies on Eve, and whichever brave souls decide to take it there.

Beware, math within.

  Hide contents

 

Assumptions: Helicopters and flappy planes work on their own principals, but they're against the rules for this challenge, so we can assume a fixed wing. Then we have steadystate flight, fixed mass, low altitude, and a several others assumptions that all jibe well.

Governing Equation: Our governing equation simply says that our lift in the upwards direction must match our weight to fly. From here on, AoA refers to the AoA of your wings, if they happen to differ from your plane's body like they do on mine. Which is weird. Hey, it's cool.
lift*cos(AoA) = mg

How do you calculate lift: "lift coefficient (Cl) then multiplied by the below mach multiplier, dynamic pressure, the wing area, and the global lift multiplier"

Other Substitutions:
Wing lift coeff = 12*mass (this is for the basic fin. Everything else is 10*mass, which is worse)
airDensity = n*MW/V = P*MW/RT
m = massWings + massExtras

Base Equation, followed by substitutions . Putting together the above three sections.
liftAngleCoeff * machMultiplier* .5*airDensity*v^2 * wingLiftCoeff* globalLiftMultiplier * cos(AoA) = (massWings + massExtras)*g
liftAngleCoeff * machMultiplier* .5* P*MW/RT  *v^2 * 12*massWings * globalLiftMultiplier * cos(AoA) = (massWings + massExtras)*g

Solve for velocity, then plug and chug.
v = sqrt[   (1 + massExtras/massWings) *  g   R   T  /(6*liftAngleCoeff*machMultiplier*   P    *   MW  *globalLiftMultiplier*cos(AoA))   ]
v = sqrt[   (1 +     0     /    1    ) * 9.8*8.3*298 /(6*   .857       *      1       * 100194 *.028964*        .036        *  .934  )   ]
units in pascals, kg, K and m. The units won't work out in the equation, because some aspects are based on heuristic.
v = 7-ish m/s (Mileage may vary. Void where prohibited. Manufacturer not responsible for misuse of product.)

Discussion: The formula fits observations within about 10%, which I'm happy with! When actually playing, transient conditions (flappy planes or torque from drag) and bit of downwards thrust can lower the min speed a bit. Ultimately, I'm a happy camper because my theory and experiment have both bean pointing at a 7-ish m/s min speed for the obsessively (and unnecessarily) controlled case with per-tilted wings. I very much like it when theory and experiment agree.

How much does the downwards thrust help? Not much. Here's the math. We're looking for the relative reduction in V for a given change in the mg term.
1 - sqrt[  ( massCraft *  g  - SparkThrust*Throttle*sin(AoA)    )  /  (massCraft * g )  ]
1 - sqrt[  (    2      * 9.8 -     16     *   .7   *sin(30 deg) )  /  (     2    *9.8)  ]
 15ish% improvement . Units in kN, tons.

 

I know, sorry! Who put all this math into ksp . Here's the take homes:

  Hide contents

 

The best angle of attack is 21 degrees. It's much better to be a bit high than a bit low. Values in the equation are based on this.

Temp: Your minimum speed will probably be 1.5% slower at night-time relative to mid afternoon. For a given pressure, lower temp means greater air density. 298.2  at just before sunrise ; 308.2  in the early afternoon.

For two otherwise identical craft, the one using basic fins for wings should go 9% slower.

I don't see the gif anymore, but I think DualDesertEagle's case has a massExtras/massWings of about .25 . (4 times more wings than anything else) So that's the number to beat! It's a nice number.

Just using DualDesertEagle's latest as a test case, the downwards thrust will lower the min speed by about 15%. This is well within the bounds of not-worth-caring-about for a fun challenge!

 

Go to Eve
A plane at sea level near Eve 's poles should have a min speed half of that on Kebin! It'll be slightly higher elsewhere because of the higher temps. Someone with their game face on should try it. Beware though, Eve will happily crush your planes with its oppressive gravity, and stifle your rockets with its soupy atmosphere. Hyperedit would probably be a good way to make it out there- landing on Eve is a challenge on its own!

 

Don't forget we're not only talkin' about a thicker atmosphere but also much higher gravity when it comes to Eve. And I've already been through all the effort of sending the plane in my first entry there, it took much higher speeds to get it off the ground.

 

And I don't think Laythe's atmosphere is much of a difference to Kerbin's atmosphere, as is the gravity.

Edited June 26, 2016 by DualDesertEagle

[Cunjo Carl]

On 6/25/2016 at 5:33 PM, DualDesertEagle said:

Don't forget we're not only talkin' about a thicker atmosphere but also much higher gravity when it comes to Eve. And I've already been through all the effort of sending the plane in my first entry there, it took much higher speeds to get it off the ground.

 

And I don't think Laythe's atmosphere is much of a difference to Kerbin's atmosphere, as is the gravity.

 

Don't worry, took account for all that! Taken account of different gravities, air pressures, air temperatures and average molecular weights. It's interesting what goes in to how much atmosphere your wings have to push off. I've gone on a limb using some formula from real life that KSP may not, and now that you've mentioned it, I'll be sure to send dragonfly out there to check. I was hoping to get someone else a chance for a winning entry, but given what you've said it's much better I don't accidentally send someone on a wild goose chase!

Edit: Looks like it wasn't a wild goose chase. Good to check it, though! Here's a random test craft I made (can't find dragonfly ) in steady flight conditions on Kerbin and Eve, and it looks like Eve's speed is about half that on Kerbin. Perhaps you tested at a much higher altitude near the equator at day? Eve can definitely be worse in certain conditions.

 

Edit: In retrospect, why I did the Kerbin flight over the arctic is beyond me. Fit with the vibe, I guess. I wonder if the colder temperatures there enhance lift?

Edited July 1, 2016 by Cunjo Carl
doin some doublechecks

[DualDesertEagle]

Ok, u've definitely beaten my speed but now I do have to ask once more: Do attempts in other atmospheres count, @volcanic_wolf  ?

 

How do I "mention" ppl so that they can see it btw? For now I just copied the mention from another post.

Edited June 26, 2016 by DualDesertEagle

[Deddly]

1 hour ago, DualDesertEagle said:

How do I "mention" ppl so that they can see it btw? For now I just copied the mention from another post.

Just type "@" as the first character and continue by typing the first few characters of the person's name. It's a little hit and miss, but it usually works. 

 

On topic: I agree that there are a number of questions that OP needs to answer

[Cunjo Carl]

2 hours ago, DualDesertEagle said:

Do attempts in other atmospheres count, @volcanic_wolf

Yeah, I agree. I'm not really sure what to make of it. "Taking it to Eve" is kinda a cool way to continue the battle, but it's not really the plane that's any different...

 

[volcanic_wolf]

yes but it won't count except for against other planes in the same atmosphere

 

[DualDesertEagle]

Phew, thought I'd end up in 2nd place

[Cunjo Carl]

8 hours ago, volcanic_wolf said:

yes but it won't count except for against other planes in the same atmosphere

Yay, I have first place on Eve!   It was a cool bit of math though, right?

[vosechu]

@DualDesertEagle have you considered a two wheel variant like the U-2? Might save a little weight! https://en.m.wikipedia.org/wiki/Lockheed_U-2

[DualDesertEagle]

I know the U2 very well and have even built a rough replica of it in KSP before, but I already have the slowest plane (on kerbin) with the least amount of parts and the best weight-to-lift ratio. My 2nd submission is gonna be very, VERY hard to beat, if it's possible at all. I'd like to see someone do it tho, to show me I haven't reached the limit yet.

[Cunjo Carl]

     Pardon the earlier post-in-progress! I've been watching SGDQ while assembling this, and was just barely able to submit and save progress before Twitch ate my browser.

     I wasn't really planning to return to slow planes. I'd already hunted down and came to understand most of the mechanisms and design tradeoffs involved, so the only thing left was taking the time to build it. For me, unless I'll learn something or it makes me laugh, I've got to move on! With this in mind, unwittingly while doing dishes, I designed a plane with predicted 'low 6s takeoff', and christened it the "Fin to Win." ... Fin to win?  Welp, I guess it's happening.

Fin to Win:

Spoiler

Fin to Win

Hop! Using basic fins lowers the minimum speed dramatically (a whole .6m/s!) thanks to their singularly excellent lift to weight ratio. After that the craft flies at 6.3m/s thanks to its 30 degree downwards thrust, which has become an acceptable norm. This craft would otherwise do about 7.3m/s, very close to the 7m/s ideal speed with basic fins.

     I'm quite happy with this, but of course we always have our eyes set on improvements, so let's give a couple ideas their due!

The Fosbury Flip:

Spoiler

The Fosbury Flip

Flip! This plane lifts off at 4m/s thanks to the "Fosbury Flip", the Kerbal plane equivalent of the Fosbury Flop. Things torquing against the COM (like wings and wheels) can create a transient off-the-groundedness that can briefly appear as flight. The COM stays low, but the plane lifts off the ground! Of course, I had to go Kerbal with the concept. Flip.

The Cheater Effect:

Spoiler

None Shall Pass says the plane with it's arms held broad.

So, the upwards tilt of the engines generates a very non zero amount of lift. The more drag we can provide, the more of this engine lift we can enjoy while keeping our speed low! Does it work? Well....

    Well, perhaps improvements was too strong a word .

Edited July 3, 2016 by Cunjo Carl