tetryds

Official FAR Craft Repository

1045 posts in this topic

Did you ever look at the thrust of the ion engine at SL?

I bet you'd need some way to get it up to alt, so it wouldnt be purely ion-powered.

Best I've done is 20km. But at that height I think I just didn't have enough thrust to go any faster or any higher...

Edited by B15HOP_xmen

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https://www.dropbox.com/s/6sor4cabawsiw2g/Untitled%20Space%20Craft.craft?dl=0

My broken ship can someone fix it?

- - - Updated - - -

I want it to be really maneuverable, like F-22 (that's where I got my inspiration)

This ship:

lDofomz.png

The red numbers (and the >0 AoA figure) in that analysis are telling you that the ship doesn't have enough lift to fly at that speed. But the speed is set to Mach 0.35 at sea level. What do the numbers look like at 5km/Mach 0.8 and 20km/Mach4?

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Also, if you want maneuverability, you're going to want to swap out those fin+control surfaces at the back for all moving tail fins.

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Also, if you want maneuverability, you're going to want to swap out those fin+control surfaces at the back for all moving tail fins.

What do you mean?

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I want to learn how to build better planes with FAR by being able to interpret some of the data overlays I'm seeing in this thread. I can Google wave drag and all that, but when it comes to applying that in game with a custom craft I get a bit confused.

I certainly don't have trouble with making craft fly in FAR. But I still follow the more or less old way of assembly with the CoL being just behind the CoM and that's it. Other then that I just go by looks. I don't even open any of data readouts far gives me.

But I need to improve my designs just a bit. The big thing being consistency. So... Maybe someone can point me in the right direction?

https://github.com/ferram4/Ferram-Aerospace-Research/wiki

Seems like a good start. But if anyone by chance knows of any other material I can educate myself with I'm all ears.

Edited by Motokid600

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Seems like a good start. But if anyone by chance knows of any other material I can educate myself with I'm all ears.

I'm still struggling through it, but here's what I've got so far:

* The CoL is now more of a guideline than an actual rule, so...

* Pull up the stability + derivatives and run it. Look at the red numbers and the tool tip describing what they're supposed to be

* Start gently nudging various control surfaces, hitting the calculate button, and see if the number moves in the right direction. Keep tweaking until it's green

* For transonic craft and vessels that have trouble pushing through the sound barrier: turn on the transonic design curves. The green curve is cross-section area. Keep that as smooth as possible. The yellow curve shows how fast the green curve changes. Try to keep the bumps in the yellow line as small as possible. For instance, if you have a section where wings start increasing in size, see if you can match that with a reduction in fuselage size to keep the rate-of-change of the cross-section as small and as smooth as possible.

* The black horizontal lines show scale, so if you have a small craft, the yellow line will look all bumpy but that's because you're waaay zoomed in, graph-wise. Only worry about big bumps in the yellow line if the horizontal bars are getting squished vertically (showing that you're "zoomed-out", graph-wise).

Example: In the first image, see how the yellow line has a serious bump right behind the cockpit where the wings increase the cross-section area. Now in the second image I've replaced the tank with a tail that narrows as the wings increase in size. This keeps the cross-section area changing smoothly (and in fact, decreases slightly -- green line), reducing the bump where the wings start. There's still a huge bump at the end where everything just stops. This is one of my problem areas, but it can be mitigated a bit with careful placement of tail and elevator wing/surface shapes.

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Edited by jrandom

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Honest advice? Less reading, more paying attention to the on screen prompts :) FAR is pretty good at telling you what's wrong, and you're often better off just using the slider gizmos and watching how it affects the numbers than you are trying to research the mathematics of hypersonic flight ^^

Red numbers in the calculations window = problems. Mouse over to see if they're pitch/yaw/roll, then add/modify wings and control surfaces to improve it.

Wave drag should be as low as you can get it, pretty much end of story; just try adding bits to flesh out the fuselage wherever it's narrowing or see if you can make the change of cross section gentler ^^

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https://www.dropbox.com/s/6sor4cabawsiw2g/Untitled%20Space%20Craft.craft?dl=0

My broken ship can someone fix it?

- - - Updated - - -

I want it to be really maneuverable, like F-22 (that's where I got my inspiration)

Inspiration, or replica? Cause wave drag area is very high, and would need to be tweaked imho unless you want a replica.

What do you mean?

Parts like "Tail Fin".

Basicly, your elevator authority is very low - if you pull much, the nose doesnt move much.

To put it simply: ur elevator needs moar powar!

PS: You might also want to empty some of those fuel tanks to safe weight.

Edited by FourGreenFields

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I want to learn how to build better planes with FAR by being able to interpret some of the data overlays I'm seeing in this thread. I can Google wave drag and all that, but when it comes to applying that in game with a custom craft I get a bit confused.

I certainly don't have trouble with making craft fly in FAR. But I still follow the more or less old way of assembly with the CoL being just behind the CoM and that's it. Other then that I just go by looks. I don't even open any of data readouts far gives me.

But I need to improve my designs just a bit. The big thing being consistency. So... Maybe someone can point me in the right direction?

https://github.com/ferram4/Ferram-Aerospace-Research/wiki

Seems like a good start. But if anyone by chance knows of any other material I can educate myself with I'm all ears.

I tried my best to explain building planes with help of FAR graph. Those are from old FAR, but everything is pretty much valid for nuFAR. I will going to add new area ruling feature there as soon as I got some time to edit pictures.

You can also check Wanderfounds craft exchange thread for more tips, and Kepitns Basic Aircraft Design thread is usefull too.

If you dont find answer for your question trough those threads, ask here with more specific question.

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This one cuts through the sound barrier like Butter.craft. Requires TweakScale, Procedural Parts, and Adjustable Landing Gear.

The tweakscaled-down engine (0.625-meter J-X4) provides less-than-stellar thrust when taking off, but once up to altitude it screams along nicely. Starts to lose yaw authority around Mach 2.75 due to the small yaw surface, but would probably overheat and explode past Mach 3 anyways. At least, if you have DRE installed. Probably.

Took forever to figure out how to arrange the wings balanced against the intakes while still minimizing wave drag.

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Edited by jrandom

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@Motokid600: it's been a few months since I started developing some FAR tutorial videos, and I have finished remaking the script for the first one (for the third time).

The long time I took was mostly due to an extensive research, the scripts are much faster to put together now, and the first one is ready to go.

I am travelling and will start recording and editing in 8 days, but as I see many people need it, I will hurry up.

I hope no one minds my accent, it's also a major concern as the ammount of information is huge.

I cannot give an ETA, last two times I had to throw it away because it was not as good, and some technical stuff was missing.

I just have one question.

There is a huge jump betwen basics and transonic design, would everyone rather that I go straight for it after the first video or would it be better if I stick to the plan and release them linearly?

Remember that I can't ease up on technical words and will assume you know everything up to that point, so it could end up being confusing for newbies.

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I made a thing and I'm really proud of it. Uses a few mod parts, probably can't take any cargo and is an absolute pig to get to orbit and but the twin RAPIERS do the job well enough. I also happen to think it looks pretty damn cool.

tiaGpDD.jpg

Mods used: KAX, Mk2 Expansion, StockPartRevamp.

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My current money maker... For all missions non-combat related on Kerbin for Science!

75Q8TB2.jpg

I call it the P-4 Dexter.

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@Motokid600.

Thanks so much everyone I couldn't have asked for better replies. As for the tutorial your working on.. Imo.. linear. Regardless it sounds I best brush up on my vocabulary. I look forward to it.

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How to Read and Use FAR Analysis Screens

You can design perfectly well just by eyeball and flight testing; the flight data isn't absolutely necessary. But it does help if you can use it.

The first screen in Ferram is the static analysis screen. This gives you pretty graphs.

It has two options at top: Sweep AoA and Sweep Mach. There are boxes at the bottom which say Lower, Upper and Mach/AoA. This page can produce two different graphs: if you press the Sweep AoA button, it shows the behaviour of your plane from Angle of Attack values between Lower and Upper, at the speed shown in the Mach/AoA box. If you press the Sweep Mach button, it shows behaviour at speeds between Lower and Upper at the AoA shown in the Mach/AoA box.

The blue line is the Coefficient of Lift. It's good when this is high.

The red line is the Coefficient of Drag. It's good when this is low.

The yellow line is the Coefficient of Manoeuvrability/Instability. You want this to be angling down (like it is here), and it's best that the slope of the line isn't too steep and that its X-intercept (where the yellow line crosses zero) isn't too far above zero.

The green line is lift divided by drag. It's good when this is high.

rPK07yh.png

This picture shows how the plane will act at Angles of Attack between 0° and 25° while travelling at Mach 2.

Sometimes the lines split into two lines. This shows how the plane responds after a stall: you get a sudden loss of lift and increase in drag that lasts until you return your AoA to where the line isn't split any more.

This is the same picture at Mach 0.8. See how the plane can stall at that speed?

M6CfRoR.png

If you click the Sweep Mach button, you instead get a look at a bunch of different speeds with Angle of Attack held constant. This shows Mach 0-6 with a 3° AoA. The bumpiness on the left shows the effect of breaking through the sound barrier.

xLkx98L.png

The second page of Ferram is data and stability derivatives. This produces scary looking numbers.

JmXc3vw.png

To get those numbers, you need to put in values for altitude and speed.

All of the confusing letters that appear when you hover your mouse over the output numbers relate to this picture here:

bodycs.gif

x is forwards, y is sideways, z is down. P is roll, Q is pitch, R is yaw. Don't worry about the Greek for now.

If you hover your mouse over any of the numbers, it'll pop up a tooltip explaining what it refers to. Mostly, however, all you want to do is make as many as possible of the numbers green and as few as possible red.

The one other useful thing on this screen is the "level flight" stuff up top right. If you set the analysis for zero altitude and the speed for whatever you think you can reach on the runway, you can find out how much AoA you need to take off (the "level flight" value). Try to keep that number below ten for easy takeoffs.

Transonic drag and Area Ruling

QMJY7km.png

Go to transonic design and toggle the area curves. The green line shows the cross-sectional area of the aircraft as you move from nose to tail; the yellow line is a measure of how smoothly the green line is changing. Mach 1 Wave-Drag Area is the thing that you're aiming to minimise; if you manage to get the wiggles in the yellow line to the smallest amplitude possible, that is what you'll achieve. The lower the wave-drag, the less power you'll need to get up to speed.

With all of these analyses, you should have your gear toggled up. See how much they affect the outcome here:

xtV7a77.png

How to Apply FAR Aero Analyses

The pretty graphs: use these to check for excessive drag and regions of instability. AoA graph is the more useful of the two.

Numbers: use the Level Flight figure to work on your takeoff speed and flap settings. For the stability figures, check takeoff (0 altitude and .35 or so speed), low altitude (5km and .8 speed), Mach 1 (speed obvious, 10km) and edge of rocketry (25km, Mach 4.5). You want green everywhere. You won't get it, at least to start with.

Hover your mouse over the red ones and use the picture above to work out what the tooltips mean. Once you decode the x's and y's, usually they just mean something like "has a tendency to roll when pitching up" or similar. Sometimes the solutions are obvious (e.g. too much yaw slippage, add a rudder), sometimes they take a great deal of trial and error to sort out.

With the transonic drag stuff, just wiggle parts about and see what happens. To achieve the lowest drag, "fill in" dips in the green line and "shave down" peaks.

Video tutorials: https://m.youtube.com/user/TheWanderfound

Illustrated tutorial: http://s1378.photobucket.com/user/craigmotbey/Kerbal/Tutorials/Hangar%20to%20Landing/story

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My very first MK3 SSTO, which I'm very proud of :) This thing has been capable of lifting anything to LKO so far I have tried to fit into it.

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Edit1

Can somebody tell me how to make these imgur albums work?

Edit2

Nvm

Edit3

craft file if you would like to have a go https://www.dropbox.com/s/f4e2twx2yayfn4z/NuFarLaggerNoMore.craft?dl=0

Edited by Mäpä

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Challenge completed. Had already pretty much given up on building a good plane on strict area ruling. And then I didnt notice I had strict area ruling switched on while building a new plane. :D

Doesnt quite calculate the same values every time, but on strict area ruling it seems to stay above a ratio of 15. Most recent values were 18.81 and 15.38. On default settings 25.04.

Called it P6, as it is the 6. plane I've built (not counting replicas). And gave it the nickname "Arrow" because reasons.

Entirely take-offable (yes, that is a word imo :P), flyable, and landable (landable without the thing breaking apart, or rolling over).

Less acceleration than P2, due to higher weight. Instead of using a bicycle landing gear, I used a very narrow nose-wheel landing gear, which makes it way more user-friendly. Nonetheless, still a record plane, nothing for everyday use (although it has built-in Mystery Gooâ„¢ canisters, and 2 thermometers, so it can be used for science).

Has proven to be stable while flying straight at up to Mach 4.9, and is prob stable at even higher speeds too. Even controlable while maneuvering at high speeds, although it is slightly instable on the yaw axis.

Uploaded it on KerbalX.

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The yellow line is the Coefficient of Manoeuvrability/Instability.

You want this to be angling down (like it is here), and it's best that the slope of the line isn't too steep and that its X-intercept (where the yellow line crosses zero) isn't too far above zero.

Some noob reading this could think that yelow line is not so much important, while it is most important stuff to build stable plane.

Yelow line tells you were plane nose will be pushed up(if yelow line goes up) or down(if yelow line goes down) by other foces of influence(gravity mostly) other than pilot control input.

If yelow line is very close to X axis of graph it means that plane is neutraly stable(neither pich up or pitch down without pilot input) which is on the other hand same as unstable plane.

Thing of highest importance is point where yelow line cross X axis of FAR graph. For stable plane you want it to go always down more and more, as you have higher and higher AoA.

To be able to control your plane, you want that yelow line cross X axis in area where is green line positive - positive lift/drag ratio.

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Now that I understand Area Ruling, I built this as a test. Thing will glide supersonic for a long time.

k4Zs4d2.jpg

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Something for early career.

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SETIctt Science planes V1.00 - craft files

There is three variations of same craft. All of them use only 30 parts - maximum allowed for Level one SPH.

Those are build from early available parts in career mode, based on SETIctt mod. You will also need DMagic orbital science mod for all those nice scientific stuff. Plane is made as purpose for stable early subsonic flights, with weak engines available on early tech tree nodes you can't go faster anyway.

I highly recommend to try SETIctt mod. It offers completely new experience for us who prefer to build planes more than rockets.

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Behold for Gloriousness

This is my attempt at a heavy cargo 'bomber like' plane, weighting some 11 tons partially fueled. Using some of those KAX engines I've balanced.

screenshot_2015_05_18_01_43_47.png screenshot_2015_05_18_01_45_17.png screenshot_2015_05_18_01_49_06.png screenshot_2015_05_18_01_50_06.png screenshot_2015_05_18_01_59_18.png

Rolling up at around 120 knots, easy to get up to speed with those powerful radial engines. Really super stable, a pleasure to fly, has a good operational range but climbs really slowly.

screenshot_2015_05_18_02_02_00.png screenshot_2015_05_18_02_03_21.png screenshot_2015_05_18_02_06_09.png screenshot_2015_05_18_02_06_16.png screenshot_2015_05_18_02_10_55.png

Be careful though, or you'll end up undershooting the run way like I did on my first attempt, still it held pretty well and did not crash. Coming in for my second attempt, gently gliding into the runway, really easy to stop, isn't it glorious?

On rockets though:

It seems with the recent FAR it becoming more and more impossible to launch some more simple and traditional fins-less rockets. I've run some tests with this cool prototype.

vls1.jpg screenshot_2015_05_18_02_22_49.png screenshot_2015_05_18_02_46_04.png

The first kinda what I was aiming for, though memory fooled me.... Anyway, even though this kinda of rocket seems super cool, it becomes too bad at turning and thus too unstable... Anyone achieve some kinda design like this in FAR?

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