Jet speed

[Benredder]

Ok so I very recently unlocked the basic parts to create planes. I've created a little jetplane that I've managed to get engines on that get the plane up to 100 m/s, but as soon as it gets that far, it stays. It won't go any higher than 100.3 m/s and I can't manage to get the plane in the air because of it. I put more engines on it, but it still won't go faster than 100.3. Any advice or reasons why? 

[Human Person]

Hmm, you could increase the wing area to make the plane capable of flying slower..

[Benredder]

13 minutes ago, Physics Student said:

Hmm, you could increase the wing area to make the plane capable of flying slower..

I'm not entirely sure how to do that with the parts I have 

[mk1980]

can you post a screenshot of your design? it's much easier to understand what you're doing and give suggestions when we can see your design.

also, you can start a "sandbox" game and take a look at the "stock" aircraft that come with the game. maybe you can learn a few things just by looking at their designs and flying them.

[Benredder]

I'm playing on Xbox One, so I'd have to take a picture with my phone and paste it on here and that's not really working out for me right now. I took the advice of Physics Student and that worked for some reason. I just switched out my back set of winglets for a much larger set of actual wings. I also put elevons on the back set. I managed to get it in the air with that and figured out how to fly it, but it is pretty rough flying. It also still only goes about 100 m/s while on the ground, but as soon as i manage to get it in the air, it speeds up to almost 200 m/s

 

Edited September 9, 2017 by Benredder

[Spricigo]

WYou can't include pictures directly in this forum.  You need to host it  somewhere else them post the link to the archieve (e.g. http://i.imgur.com/q9G7iNi.png ) . {Normally the embedded image is show but in  this case I forced to display as link instead. }

100m/s should be more than enough to take off. There is a variety of designing flaws that may cause the issue and we really need a image to visualize what's wrong with your craft. 

 

[Confused Scientist]

Try moving your rear landing gear forward. If you think of the plane of a lever, then the rear set of gears is the fulcrum.

[Kryxal]

100 m/s is 360 km/h, about 212 mph.  Suffice to say you're going at a fair clip and anything in real life that is going to fly, has probably left the ground at that speed

[Cunjo Carl]

@Benredder

Sounds like a drag!

Those little Junos are tricky to learn on. They have very little thrust, and all the parts available at that tech level are draggy unless you get creative (lead culprits being that danged cockpit and any sections where the plane goes from small 1.25m to tiny .625m). My cureall is to use a few Junos! You can add Junos in two common ways- the nicer looking is to place a pair of mk0 fuel tanks onto your fuselage using mirror symmetry. Put small circular air intakes on their fronts, and extra Junos on the back. With 3 Junos you can finally get cooking! You could alternatively use small cones rather than mk0 tanks for a similar effect.

3 Junos isn't necessary for flight, but it makes things a lot easier to learn on. Another thing I'll extol are making sure your front landing gear is placed far enough down that your plane has a slight upwards tilt on the runway, and/or 'pretilting' your wings by rotating them up one 5 degree tick to help catch the wind. Again not necessary, but handy when learning... As a sidenote, beware the swept wings aren't quite as lifty as the other options.

There's a million things to go wrong with planes, so generally speaking please have fun with the process of idea-explosion-repeat and feel free to bug us when something gets frustrating! In the end the effort's definitely worth it.

As others have mentioned, pictures can be handy for diagnosing any trouble (and without one, my suggestions are a bit of a shot in the dark, though your problem feels like a familiar one to me). Even a cellphone pic of your TV can be a handy, it doesn't have to be fancy. With picture in hand, you can upload it to a file hosting service (PostImage is my favorite, but Imgur is very popular here), and then paste the link from that webpage into your post.

I hope that helps! Best of luck with your flyer.

[Benredder]

1 hour ago, Cunjo Carl said:

@Benredder

Sounds like a drag!

Those little Junos are tricky to learn on. They have very little thrust, and all the parts available at that tech level are draggy unless you get creative (lead culprits being that danged cockpit and any sections where the plane goes from small 1.25m to tiny .625m). My cureall is to use a few Junos! You can add Junos in two common ways- the nicer looking is to place a pair of mk0 fuel tanks onto your fuselage using mirror symmetry. Put small circular air intakes on their fronts, and extra Junos on the back. With 3 Junos you can finally get cooking! You could alternatively use small cones rather than mk0 tanks for a similar effect.

3 Junos isn't necessary for flight, but it makes things a lot easier to learn on. Another thing I'll extol are making sure your front landing gear is placed far enough down that your plane has a slight upwards tilt on the runway, and/or 'pretilting' your wings by rotating them up one 5 degree tick to help catch the wind. Again not necessary, but handy when learning... As a sidenote, beware the swept wings aren't quite as lifty as the other options.

There's a million things to go wrong with planes, so generally speaking please have fun with the process of idea-explosion-repeat and feel free to bug us when something gets frustrating! In the end the effort's definitely worth it.

As others have mentioned, pictures can be handy for diagnosing any trouble (and without one, my suggestions are a bit of a shot in the dark, though your problem feels like a familiar one to me). Even a cellphone pic of your TV can be a handy, it doesn't have to be fancy. With picture in hand, you can upload it to a file hosting service (PostImage is my favorite, but Imgur is very popular here), and then paste the link from that webpage into your post.

I hope that helps! Best of luck with your flyer.

http://imgur.com/ygZKiPt this is my current plane 

[AeroGav]

1 hour ago, Benredder said:

http://imgur.com/ygZKiPt this is my current plane 

 

First thing, it looks like you got 3 size 1 liquid fuel tanks - 1200 units of liquid fuel.   That's a huge amount, unless you really need to circumnavigate 3 times without refuelling all that does is drive up your takeoff and landing speeds.

Second,  those basic swept wings are unique in that their lift rating is half what it should be for their mass.     All other wings have the same lift:mass ratio, and BTW drag is based on lift rating, mach number, air density, and angle of attack, not shape.    So basically , don't use those wings .   Cobble together something out of the basic square and rectangular slabs you also get with the  basic aviation tech.  Those crappy  swept wings are forcing up your takeoff and landing speed by their poor lift.  

Third,  in KSP most drag comes from fuselage parts, and what really creates huge drag is when you join parts together with non-matching attachment node diameters.

So

•  your cockpit (1.25m node) appears to be joined to a 0.625m probe core - this creates drag due to size mismatch 
• the 0.625m probe core (0.625m node) then joins to a mk1 fuselage with a 1.25m node - another size mismatch drag problem
• at the back, it looks like the fuselage ends abruptly - a 1.25m attach node with nothing on it, creating huge "flat plate" drag.   Needs a tail cone or nose cone to cover its back end
• offsetting/clipping stuff doesn't affect drag, (it only moves the point where the aero forces act on your ship)

The best fuselage design for a starter plane like this is to put a 1.25m service bay behind the cockpit (stick your 0.625m probe cores and lumpy stuff here out of the wind) then go to a tail cone connector.      You have generally the right idea clustering size 0 engine nacelles around the main fuselage or hanging off the wing .  Just make sure the arrangement is symmetrical - i hope you've got more than 2 engines in that picture because the two i can see are above centre of mass.    They will tend to pitch the nose down when you throttle up, which could make it tricky to fly.

Edited September 10, 2017 by AeroGav

[Benredder]

1 hour ago, AeroGav said:

 

First thing, it looks like you got 3 size 1 liquid fuel tanks - 1200 units of liquid fuel.   That's a huge amount, unless you really need to circumnavigate 3 times without refuelling all that does is drive up your takeoff and landing speeds.

Second,  those basic swept wings are unique in that their lift rating is half what it should be for their mass.     All other wings have the same lift:mass ratio, and BTW drag is based on lift rating, mach number, air density, and angle of attack, not shape.    So basically , don't use those wings .   Cobble together something out of the basic square and rectangular slabs you also get with the  basic aviation tech.  Those crappy  swept wings are forcing up your takeoff and landing speed by their poor lift.  

Third,  in KSP most drag comes from fuselage parts, and what really creates huge drag is when you join parts together with non-matching attachment node diameters.

So

•  your cockpit (1.25m node) appears to be joined to a 0.625m probe core - this creates drag due to size mismatch 
• the 0.625m probe core (0.625m node) then joins to a mk1 fuselage with a 1.25m node - another size mismatch drag problem
• at the back, it looks like the fuselage ends abruptly - a 1.25m attach node with nothing on it, creating huge "flat plate" drag.   Needs a tail cone or nose cone to cover its back end
• offsetting/clipping stuff doesn't affect drag, (it only moves the point where the aero forces act on your ship)

The best fuselage design for a starter plane like this is to put a 1.25m service bay behind the cockpit (stick your 0.625m probe cores and lumpy stuff here out of the wind) then go to a tail cone connector.      You have generally the right idea clustering size 0 engine nacelles around the main fuselage or hanging off the wing .  Just make sure the arrangement is symmetrical - i hope you've got more than 2 engines in that picture because the two i can see are above centre of mass.    They will tend to pitch the nose down when you throttle up, which could make it tricky to fly.

http://imgur.com/vEwtnZS I scrapped my old plane and made what I consider to be a mini jetliner 

Edited September 10, 2017 by Benredder

[Palaceviking]

Four wheels?  

[AeroGav]

6 minutes ago, Palaceviking said:

Four wheels?  

If it works, why not.  He won't be able to steer on the ground though.

Having more than 3 wheels does help when landing on rough ground.

[zolotiyeruki]

It looks like you still have 3 of those fuel tanks, which each adds 2 tons to your craft.  I'm also wondering how you rotate the craft for takeoff with that arrangement of landing gear.  I'm not seeing any scientific gear (that you'd be using for collecting science to unlock more nodes in the tech tree), so I'm a bit curious about what the plane's intended use is.  That is, unless this is just for playing around, which is just fine

[Scarecrow]

@Benredder  I made a replica of your second version, with a few changes, and it flies fine.  Start the engines and it rolls down the runway and takes off on its own with no input, and flies pretty smoothly.

The changes I made were to reduce the two top tailfins to just one to save weight.  I removed the rear two landing legs and replaced them with a single small steerable landing gear. This saves weight and allows the plane to be steered on the ground.  It also lowers the back of the craft when sitting on the ground, which is how my version is able to take off on its own.

I can't tell from your picture if the three cylinders that make up your fuselage are fuel tanks or just fuselage sections.  As fuel tanks won't feed to the engines without the use of connecting pipes, and I can't see any of those on your plane, I used fuselage sections.  Again these save weight over fuel tanks, even if the tanks are empty.  The last design change was to use a short cone on the rear of the plane to avoid the risk of a tail strike if I had stuck with the longer version that you have.

Control wise, I set the inner elevons on the main wing to be used as flaps only.  The outer elevons are restricted to roll only.  The rear tailplanes I had set to control pitch and roll, and the tailfin was set to control yaw only.

With no input it takes off at about 100 m/s, or 75 m/s with flaps deployed.  With flaps and a touch of back stick, it will leave the ground at 50-55 m/s. Max speed at low level seems to be around 390 m/s.  I haven't tested to see what the ceiling is.

I hope that helps.  Getting planes to fly nicely in KSP can be quite a challenge but gives quite a sense of achievement when you manage it.

Edited September 22, 2017 by Scarecrow

[Kryxal]

100 m/s is plenty of speed for takeoff, that's 360 km/h or about 225 mph.  Engines mounted high and rear gear far back are probably the culprits.

[Jas0n]

Also, move the back set of gears forward so that they are closer to your center of mass (but not in front of it) so that your control surfaces have more leverage to lift the nose up.

[AeroGav]

3 hours ago, Scarecrow said:

As fuel tanks won't feed to the engines without the use of connecting pipes

Not been true for a long while that....?    Only thing that stops fuel flow is a decoupler, if crossfeed is disabled.   Though I think you can set something in the game option where pipes are required?

[Scarecrow]

5 hours ago, AeroGav said:

Not been true for a long while that....?    Only thing that stops fuel flow is a decoupler, if crossfeed is disabled.   Though I think you can set something in the game option where pipes are required?

I still have a few designs where the fuel doesn't flow from some tanks unless I use connecting pipes, and it's not because I have used decouplers.  I'm not sure how @Benredder has connected his engines to the wings, but I used the small hardpoint pylons, which act like a decoupler.  I have them disabled for staging, so I don't accidentally lose my engines.