I would like to congratulate / curse the KSP development team for....

[James_Eh]

... making the runway and subsequent dropoff JUST long and steep enough for many many heartwrenching moments as space planes struggle to lift off.

Another evening ruined where I had productive, real-life stuff planned. Now I am hooked on achieving liftoff sans tailstrike. Why, oh why, did I ever let my son (who can make these fool plane thingies fly wherever he wants) talk me into trying a radically different approach?!?

(Oh yah - because, KSP.)

[Madrias]

You'll eventually get a plane into the air. If it helps any, take small steps and try building a strictly-atmospheric plane first. The concepts are the same, but it'll get you into the air and learning. Simple rule to live by: center of lift goes behind center of mass.

[sickboy]

what Madrias said, and don't worry, soon enough you'll take off within 10 feet of your starting point.

[James_Eh]

You'll eventually get a plane into the air. If it helps any, take small steps and try building a strictly-atmospheric plane first. The concepts are the same, but it'll get you into the air and learning. Simple rule to live by: center of lift goes behind center of mass.

I should have been far, far more specific. I am trying to tame the power of the RAPIERs to launch a SSTL(aythe) vehicle. I find that (my rudimentary) planes are relatively easy, although I know others have done many amazing things with them. I have made lots of SSTOs too, but this is my first time fiddling around with these newfangled RAPIERS and really large payloads.

I still think that the KSP gang did a great job in designing the exact runway length (and small downslope) to let players have the suspense of the last few metres of runway action. Plus, the two little signposts (or whatever they are) at the very end of the runway are a nice, evil touch. ("Leave wing bits here")

[Madrias]

They did a great job indeed. The runway is just long enough to reach that critical point-of-no-return speed where you can't save the pilot from ending up in the drink, and has just a steep enough downslope to fling some planes into the air (those that would have made it) and smash others down the cliff face below (you know the kind). Add to that those runway endpoint lights that rip wings off, smash landing gear, or break the tail, and you've got the perfect reason to scream.

But one can't blame them, it adds some excitement to a takeoff.

[cantab]

Scott Manley mentioned that you need to be able to get some angle of attack on your wings to lift off (just as you would on a real plane). If the wings are level when the plane's on its wheels, and the elevators are too close to the rear wheels, you can end up unable to lift the nose for takeoff, which results in no flight until the drop off the end of the runway lets you free.

[ArmchairGravy]

I would like to curse the runway humps on the main and island runway because of the number of craft I've pancaked on them.

[KerbMav]

Scott Manley mentioned that you need to be able to get some angle of attack on your wings to lift off (just as you would on a real plane). If the wings are level when the plane's on its wheels, and the elevators are too close to the rear wheels, you can end up unable to lift the nose for takeoff, which results in no flight until the drop off the end of the runway lets you free.

I think wings built at an angle also give better horizontal speed, as the pilot does not have to raise the nose as high to get lift, especially in thinner atmosphere - right or wrong?

[Madrias]

To a degree, yes, angled wings will help, but they will hinder at high speeds (like reentry) by trying to flip the craft. Trust me, I've tried it enough times that I've simply started affixing the front landing gear to a Cubic Octagonal Strut to get the added angle.

If you really want to get off the ground in a hurry: Canards. Lift the nose instead of pushing on the tail.

[Tommygun]

James, take a look at this for ideas that may help.

http://forum.kerbalspaceprogram.com/threads/52080-Basic-Aircraft-Design-Explained-Simply-With-Pictures?p=685737#post685737

Also this mod has a simple parts pack that adds a small amount of lift to the aircraft body and it helps a great deal when taking off.

http://forum.kerbalspaceprogram.com/threads/57662-PorkWorks-dev-thread-Inflatable-habs-and-more!-Current-project-MK2-stock-expansion

[NecroBones]

Scott Manley mentioned that you need to be able to get some angle of attack on your wings to lift off (just as you would on a real plane). If the wings are level when the plane's on its wheels, and the elevators are too close to the rear wheels, you can end up unable to lift the nose for takeoff, which results in no flight until the drop off the end of the runway lets you free.

I haven't spent a lot of time with aircraft in the game, but so far, even with some angle-of-attack, it seems like many aircraft designs will "stick" to the runway, and generate upward lift the instant they get past the end of the runway, but not before. It's strange.

[KerbMav]

A plane rotates around its center of mass. If the rear gear is behind the center of mass the plane cannot raise its nose (on the ground/runway).

Tricky part is to get the rear gear close enough to the center of mass for the plane being able to pitch up - but not to close for it to tilt backwards and sit with its tail on the runway.

Also the control surfaces for pitch have to be built quite a distance from the CoM for them to have enough leverage.

But even then - I have to agree - some designs just seem to be glued to the ground.

[Kerbonautical]

I found with planes its good to have a high TWR. I made a lot of mistakes trying to stick close to what I would use for a launcher 1.6-1.7 but found that by adding a bit more 2.6-2.7 I made it much easier to fly. I can lift extremely heavy planes this way and they actually reach orbit with more Delta V leftover than they would with less TWR since you can have a sharper ascent and then maximize speed while in the thin atmosphere much earlier.

[zarakon]

Like others have said, this is usually the result of having the wheels too far back. Think of your plane as a lever where the wheels are the pivot and your control surfaces are the forces trying to lift the front of the bar.

A few ways to make liftoff easier:

1. Put your rear landing gear closer to the center of mass. This will make it easier to pivot on the runway, but could also make your tail more vulnerable.

2. Angle your wings slightly so that they generate lift while the plane is level. I do this with almost all of my planes, but it does have some drawbacks, especially in planes intended for leaving and re-entering the atmosphere.

3. Adjust your wheels so that the nose is higher off the ground than the tail. This has the effect of angling your wings for lift while on the ground while allowing you to keep them flat for flight.

4. Add control surfaces (canards) at the front of the plane. If your rear control surfaces are having trouble pushing the back of the plane down, you can assist them by pushing the nose up at the same time.

[Franklin]

Scott Manley mentioned that you need to be able to get some angle of attack on your wings to lift off (just as you would on a real plane). If the wings are level when the plane's on its wheels, and the elevators are too close to the rear wheels, you can end up unable to lift the nose for takeoff, which results in no flight until the drop off the end of the runway lets you free.

Yeep. Need to give your plane a reason to want to take off.

Design tip: Raise your back wheels higher than your front (or lower your front so that it's lower than the back) so that your plane is inclined x degrees while on the runway and watch your plane take off on its own, sans-tailstrike.

See profile examples of how planes would otherwise park: http://goo.gl/cAK6gn

It's very rarely straight and flat, and where it is the tail is raised to make clearance when rising for takeoff.

[Franklin]

Or if the gear needs to stay put, tilt your wings for lift, like zarakon said.

[Tortoise]

You build a plane that can't get into the air, and blame it on the runway?!

[Madrias]

As I said, canards. If you can't push the tail down, lift the nose. Sure, some designs seem 'glued' to the runway, but I've found proper application of control surfaces can rip them free and throw them into the sky.

[MGCJerry]

Plus, the two little signposts (or whatever they are) at the very end of the runway are a nice, evil touch. ("Leave wing bits here")

These... Definitely these. I swear that Jebs inventory auditors installed those.. how else does he find all these parts on the side of the road? That "road" must be the runway...