Rapier mode switch issue

[endl]

mode switch for the rapier engines does not kick in for my design.

So I modeled the profile of the F22 for my space plane, im in love with the stability of this design its super maneuverable and practically lands itself while remaining highly compact, my problem is the engines though. since the plane is so compact and runs off of two rapiers for what ever reason i dont get enough thrust for the engines to reach an altitude high enough where the automatic mode switch kicks in. the plane stalls out drops back down while still on a full tank of LF/oxi.

i tried different air breathing configurations but none of them work, its really annoying.

also if someone could tell me at what altitude the auto switch kicks in that would be great.

Edited August 20, 2014 by endl

[Red Iron Crown]

It's not determined by altitude but by a lack of intake air. You can also switch modes manually by right-clicking the engine and pressing "Toggle Mode".

[endl]

thats not the problem though, like i said the auto isnt kicking in, so what are the criteria for it to kick in? its not by air intake so it must be altitude. in which case i need to redesign the engine block so that i can reach a height where the auto kicks in.

otherwise it defeats the whole point of using rapier

Edited August 20, 2014 by endl

[kStrout]

Right click on the rapier, and click the button next to automatic mode. that should make your raipers switch over at around... 25k, depends on how fast you go.

[Red Iron Crown]

Are your Rapiers flaming out? If not they are functioning correctly. You may not have enough wing or thrust to carry you high enough that they run out of air and switch over.

You could also check that you haven't accidentally disabled automatic switching by right clicking the engine.

[Laie]

It really should be lack of intake_air.

However, the few times I used Rapiers I de-activated automatic mode switching, and toggled them myself by action group. I suggest you do likewise.

[WololoW]

How many air intakes do you have on your design?

Have you ever used Action Groups? They are especially helpful for situations like this.

1. Go into the Action Groups section of the SPH(or VAB)

2. Click on "Custom 1", then click on the R.A.P.I.E.R. engine and select "Toggle Mode." (If you added your engines using symmetry, you will only need to do this for one of them and it will highlight and assign both the action group.)

3. If you added the engines on one at a time, repeat the previous step for both engines on Custom 1.

4. When in flight, press 1 on your keyboard and your R.A.P.I.E.R. Engines will swap modes from air breathing to Oxidizer&Liquid Fuel.

Hope it works for you. If you need a visual explanation, let me know and I can boot up KSP and my stream for you and show yah! (Limited time offer, leaving in about 10-15 minutes)

[endl]

Are your Rapiers flaming out? If not they are functioning correctly. You may not have enough wing or thrust to carry you high enough that they run out of air and switch over.

You could also check that you haven't accidentally disabled automatic switching by right clicking the engine.

yes they are flaming out while in auto mode still on air breathing setting

How many air intakes do you have on your design?

atm everything is symetrical in line, i took a picture its in the op. right now i have two nacelle and two radial air intakes. ive used the action groups before but for what ever reason even after toggling them the engines dont kick back on after flaming out.

heres what happens when it flames out

and heres the engines remaining none responsive after a manual toggle

Edited August 20, 2014 by endl

[Red Iron Crown]

I think it's a fuel flow issue rather than the engines themselves. Oxidizer can't reach the engines because it won't flow through a bicoupler from the doubled side (and is likely only connected on one node anyway). Try running fuel lines from the forward tanks to the rear ones.

[Zylark]

One issue I see at a glance is that you don't have enough air-intakes. I can see on the picture you provided that your air-intake is down to zero at an altitude of just a smidge over 20km. R.A.P.I.E.R.S and other jet engines only really becomes useful (read: makes stuff go so fast that it practically throws you into orbit) when at over 30km.

Here's one from my current Career:

Notice all those long rectangular bits bolted on everywhere, those are structural air-intakes from the Spaceplane+ pack. got plenty of those in addition to 14 more conventional radial air-intakes and 4 nacelle intakes. That puppy will reach almost 35km altitude before switching over automatically to LFO. And at that time going so fast, that I only need burn 1-200dV more (basically just to keep speed up whilst still cruising hyper-sonic through the upper atmosphere) to reach an orbit of 200km.

Also, as Red Iron Clown said - fuel flow. Jet Fuel like monoprop isn't that picky. You can leave your tanks wherever you wish and fuel will reach the engines. LFO on the other hand need a direct connected route to your engines. Just as you do with more conventional rockets and LFO fueled engines.

Edited August 20, 2014 by Zylark

[endl]

I think it's a fuel flow issue rather than the engines themselves. Oxidizer can't reach the engines because it won't flow through a bicoupler from the doubled side (and is likely only connected on one node anyway). Try running fuel lines from the forward tanks to the rear ones.

your right this was the problem bicouplers dont say anything about reverse flow, i hit 200k apoapsis with this build after my first successful test.

anyway for clarification the mode toggle is linked to air flow, this test proves it.

@Zylark thanks for the tip it wasnt the airflow, also im trying to play as vanilla as possible only mod im using is kerbal engineer.

cheers for making this a success guys, im only doing this off of 2 t400 tanks, you guys really need to give my kerbavor a try ;p

Edited August 20, 2014 by endl