Many questions about SSTO's, Shuttles and spaceplanes in general.

[Janos1986]

I bound the Abort AG for engine switching, Lvl2 SPH here.

Yes, the engines still cut off asymmetrically.

[Starwhip]

I bound the Abort AG for engine switching, Lvl2 SPH here.

You...

You, sir, are a genius!

[Tassyr]

I bound the Abort AG for engine switching, Lvl2 SPH here.

Yes, the engines still cut off asymmetrically.

I just use "1" for mine... And tie it to intake control too.

[Janos1986]

And the intakes are toggled as well obviously.

I haven't unlocked custom action groups yet, and I don't use the Abort sequence with spaceplanes, so...

[Arctodus]

grats! that thing looks pretty slick too! two suggestions to improve it:

1) add a couple more intakes (the long slender radial ones look really nice)

2) if you use the following placement order, your engines will never experience an asymetric flame-out, and you'll be able to use them in the airbreathing mode up to over 30km height: first place all the air intakes you want a single engine to use, then place said engine. Then place all the intakes you want the next engine to use and then place said engine. Repeat until you've placed all engines and make sure you don't use the symmetry tool or alt-click to copy the parts.

For number two, could you possibly build one entire wing with the engine and intakes with no symmetry, and then copy its with symmetry from there? Similar to the way you make liquid boosters on rockets I guess?

[SydneyACE]

Honestly I just manually cut it to rocket engines just before flameout time. I've run into asymmetric flameout about half the time otherwise.

You can get more efficiency and more speed in the atmosphere if you throttle back the engines gradually as they loose intake air. If you're using RAPIERS be sure to change them to manual switching. Us a hot-key to switch RAPIERS, close intakes, and shut-down turbojets at the same time. (You said you're already using a hotkey I see.)

The trick to managing asymmetrical flameouts and getting faster and higher while still in air-breathing mode is this:

1. The last engine you place on the craft will be the first to flame-out. Always. Not sure why, it's just the way the game works. So, if you're using the Mk2 Bi-coupler fuselage that puts the 2 engines in the center, place those 2 last. This way, one of those 2 will be the first to flame out.

2. Now that you know which engine will flameout first, just watch it. On ascent as you get close to flameout, right-click one of the last 2 engines, then Alt+Right-click the other. Now you will see the thrust ratings of each engine. (Zooming in will help to see the read-out better because it won't overlap.) As flameout approaches, one of those 2 engines will start to loose thrust and the reading will start to decrease. Slowly throttle back (using the Ctrl key) a little bit at a time until the thrust reading between the 2 engines is the same.

3. Just keep throttling back slowly bit by bit while climbing at a very shallow angle (around 10m/s VSI). (That's the little gauge with the arrow.) Finally when your speed stops increasing and you stop gaining altitude, this is the time to hit your hotkey and switch to rockets, pitch up to 45* and finish orbit.

You leave a lot of speed and altitude on the table (and thus use way more fuel and oxidizer in rocket mode) if you switch at the first signs of flameout. Once I figured this trick out, my spaceplanes got much more efficient. (You can design them with less oxidizer and fuel, which means less weight, which means better performance, etc.)

Hope that helps!!

Also as someone else mentioned, your spaceplane seems to have more lift than it needs (wings are too big). The extra wings will mean more drag which will make it harder to hit a higher speed in the atmosphere.

I just did a few different trial runs on my plane by adding wings until it became less efficient, then taking them back off.

Good luck! Let us know how it goes!

[Wanderfound]

Got a 0.90 question for people. I've seen a lot of SSTOs in this thread with two air-breathing engines. Is anyone have trouble with asymmetric flameouts? Unless I'm mistaken (and I may be. I've played less than 30 mins of 0.90.... stupid dissertation...), custom actions groups are locked behind the last level of the SPH.

Have they finally fixed the asymmetric delivery of air to multiple airbreathing engines or is there another way people are getting around the crappy fuel logic?

Or are we still using action groups to shut off the engines?

1) As mentioned already, hijack the Lights or Abort action groups. I generally use Abort to close intakes and Lights to toggle Turbojets. I'll also set up the landing lights to toggle on and off with the Landing Gear hotkey, so they're always on when lowered.

2) Keep an eye on your available air and you never need to flame out by surprise. ​Kerbal Flight Data to the rescue once again:

[numerobis]

I just use "1" for mine... And tie it to intake control too.

In the level 2 SPH you don't get numbered action groups. So I'm stuck with using abort for the engines and intakes and RCS to raise the landing gear so the rover wheels can touch the ground.

[Edit: oops, should have read more, I see this has been addressed to death already.]

- - - Updated - - -

Another trick, if you have a Lvl 1 SPH, is to make sure both engines are drawing on the same LF tank. Then you can right-click on the tank and disallow LF flow from there. Both engines will flame out simultaneously when you do that. The trick is that it's hard to click on the little arrow if you wait too long and the plane starts to flip out.

[inigma]

I've been working on a space shuttle. Most beautiful KSP creation ever. Lost it in an accidental game deletion... and all I have is the persistence file. *sniff* - ah well, either I'm challenged now to help develop an add-in that will convert persistence vessels into crafts, or I get to build an even more beautiful shuttle from scratch! Space shuttles. The ultimate in KSP engineering and balance. Don't sweat it. Nasa style shuttles are hard to find the sweet spot (but there are successes, just look at Westi's easy peasy shuttle). Spaceplanes are easier by several orders of magnitude.

[LethalDose]

Okay, so it sounds like there haven't been any improvements to the fuel flow 'logic'. The solutions presented are still work-arounds to the idiocy, though shutting down the fuel flow is a good idea I hadn't seen before. I'll have to remember that one.

[Tassyr]

Fun fact. I can't land or launch a rocket without mechjeb; but I've managed to fly these with just a freaking flightstick and my navball. And land them. And haven't lost a kerbal yet. (though I DID lose a wing.)