How much delta v will jet engines give me?

[GoSlash27]

Either you did, in fact, upload the wrong file or else you're the first I've seen to have a downloaded wikishare file be different from what they uploaded.

Whatever's going on there, it's a far cry from KSP spaceplanes, so not likely something I can help you with.

Sorry,

-Slashy

[noahtech]

Here let's try this one: https://drive.google.com/file/d/0B2NoZidKOY53MTZMYjJOeWt6NUk/view?usp=sharing

[numerobis]

That looks like a real craft file. Don't have time to test now.

[UmbralRaptor]

I think engine placement is a bit of an issue...

(This also kills the thrust on those jets)

[GoSlash27]

A few things jump out at me as potential problems beyond what Raptor has pointed out:

Having your wings inclined like that is definitely going to reduce your efficiency and increase your drag.

You're using delta wings, which have just about the worst lift to drag of any wing surface.

For larger wings, I recommend the swept.

Also FWIW the orbital insertion rocket on the back doesn't need to be that big. It's not a dealbreaker, but hey... free weight.

I'll play around with it for a bit...

*edit* yeah, the engines can't make any thrust with those wings behind the exhaust.

Edited December 7, 2014 by GoSlash27

[GoSlash27]

I pulled off the extra wings, aligned the wings and control surfaces, and had a go. It flies just fine this way.

Other observations from my notes:

-Your control surfaces should be mapped to do only what you placed them to do. You shouldn't have your elevators, ailerons, and canards trying to control yaw.

-Your intakes are not assigned to their individual engines properly, and it suffers asymmetric thrust at high altitudes. Unfortunately, this was just enough of a problem to keep it out of orbit.

Here is how you fix that.

Just do what I did and fix the intake assignments and you'll have a good starting point. There are a lot of tweaks you could do to this to make it more user- friendly and efficient. It's almost to the point where you could get by on one engine.

Best,

-Slashy

[GoSlash27]

I relocated the landing gear, fixed the intake assignments/ got rid of the unnecessary intakes, fixed the control surface assignments, and replaced the insertion rocket with a couple 48-7S rockets to save weight.

Do you want the craft file, or would you rather do it yourself for the experience?

Best,

-Slashy

*edit* Just noticed that you had drained all the fuel out of the payload to save weight, so I put it back. It can still orbit that payload, but not with those puny delta wings. Getting from 25-32KM altitude requires traveling at terminal velocity, keeping your pitch under 22 degrees, and still climbing.

I'll beef that up a bit. It'll also be more pleasant around the runway that way...

Edited December 7, 2014 by GoSlash27

[GoSlash27]

Last thread-spamming post from me.

I added a couple radial intakes in the back (shoulda had them all along to make .01 m^2/engine). The wings are 2 pair of swept wings with 3 structural Ds to give us a little positive roll stability.

With the payload fully fueled, this thing has just enough to make a 72x72 orbit, deorbit, and land.

Best,

-Slashy

[capi3101]

-snip-

-Your intakes are not assigned to their individual engines properly, and it suffers asymmetric thrust at high altitudes. Unfortunately, this was just enough of a problem to keep it out of orbit.

Here is how you fix that.

How the heck did I miss THAT? Certainly explains a few things...one more to add to the list. Going to have to fix a couple of my designs, looks like.

[noahtech]

Well I'd like to make the changes myself, but I'd also like to get the craft just as a reference. Btw thanks for the help!

[noahtech]

Wait a minute. Do you mean to tell me that when I turn the jet engines on and off one will be turned on/off before the other one depending on some arbitrary rules that I can't actually work around? D: How on Earth does anyone design space planes then? What's the point of programming the game to not turn both engines on/off simultaneously? I honestly can't think of a single reason for why someone would want that (but I can think of plenty of reasons why someone would NOT want it).

[GoSlash27]

noahtech,

No, the engines will both respond to your throttling and controls simultaneously. The problem is that they can't simultaneously flame- out. The instant one engine flames out, all of the intakes will feed oxygen to the running engine.

This is due to how the game engine works; it deals with each component of your ship in the exact order it was assembled. Left intake, add o2. Left intake, add o2. Left intake, add o2. Left engine, but it's flamed-out, so no air drawn. Right intake, add o2.Right intake, add o2. Right intake, add o2. Right engine and it's running, so give all the air to it.

So the left engine stays flamed out while the right engine keeps chugging away.

I'll get you the craft file shortly...

http://wikisend.com/download/124238/laythe-probe-launch 2.craft

You're welcome, and happy flying!

Best,

-Slashy

Edited December 12, 2014 by GoSlash27

[noahtech]

I can't seem to get it into orbit.

[GoSlash27]

I can't seem to get it into orbit.

Yours, mine, or both?

-Slashy

[noahtech]

Yours. I've already tried it both manually and with Mechjeb.

[GoSlash27]

Okay. Let's see if we can sort it out.

So what seems to be the problem? Are you running out of fuel? Having trouble controlling it?

-Slashy

[noahtech]

Well for most flights I'll start to run out of jet fuel pretty early and then I'll switch over to the rocket engines and they'll run out of fuel too.

[GoSlash27]

Okay. So the problem is that 1) your flight profile is not optimal. and 2) you're kicking in the rockets too early.

Here's my tutorial on how to efficiently fly a spaceplane:

http://forum.kerbalspaceprogram.com/threads/102182-So-you-want-to-build-a-space-plane?p=1582529&viewfull=1#post1582529

Take a look at it and see if you can spot somewhere in your launch that's not in agreement with this procedure.

-Slashy

[noahtech]

Oh I get it! I should focus more on horizontal velocity rather than vertical. Thanks! That has to be the most scenic ascent to orbit I ever did. ^^ Thanks.

[GoSlash27]

Oh I get it! I should focus more on horizontal velocity rather than vertical. Thanks! That has to be the most scenic ascent to orbit I ever did. ^^ Thanks.

So that means you made it??

-Slashy

[noahtech]

Yep. Now I just need to figure out how to set the thread to "answered".

[GoSlash27]

Congrats! Not that you've got the first one under your belt, the rest should come easy.

Yep. Now I just need to figure out how to set the thread to "answered".

If you "go advanced" to edit your OP, it's hiding in there in a dropbox.