How to high altitude?

[annallia]

First off let me state that I realize that Kerbin is far smaller than Earth so the 15,000 meters I am getting probably translates to far higher than the 21,000 ceiling that the real counterpart is capable of.

That being said... I can't seem to get any jet above 15,000 meters, or at least not significantly higher. Every jet I have tried no matter the intakes flames out at somewhere between 15,000 and 15,100 meters. I have been trying to make a U2 and something which I am calling a next gen SR-71 which have ceilings of roughly 21,000 and 24,000 meters.

Both of them I managed to get reasonably fast, my U2 cruises at just under Mach1 and the SR-X... well it goes over mach 1 before it hits the end of the runway... The problem is I always seem left with a feeling that they should be able to get higher than they are...

My U2 has 4 intakes, 2x ram intakes and 2 of the structural intakes. SR-X has 5 intakes, 1x ram 4x structural.

I played around with both adding and removing intakes, changing which intakes were used, changing engines (didn't care for that one) but they all seem to suffer the same problem of flaming out at just over 15,000 meters, the only difference any of it seemed to make was how quickly I reached that altitude.

Is there anything I can do short of switching to LF/O fuel and using a rapier instead to get them any higher?

Edited June 23, 2015 by annallia

[Xannari Ferrows]

You're getting close to the altitude limit for available intake air [30,000m] It's no wonder your engines flame out. Ram intakes with a Turbojet can get you higher, provided you can generate sufficient lift and TWR.

You want to start off fast in the lower atmosphere. Going at full throttle and taking a steep ascent is nothing to be ashamed of, especially with Rams.

[RCgothic]

As Xannari said, it is possible to build a craft that doesn't flame out up to 30km with a little difficulty, and Mach 1 (320m/s) is about a fifth of the speed you should be able to achieve on air-breathers alone. Sounds like you're not going remotely fast enough, which is why you don't get enough air and flame out. You may be too draggy - too many intakes is a negative, not a plus.

[annallia]

Yes I know why they are flaming out, I just want to know how to get higher

Speed and ascent are not a problem, specially with my revision of the SR I usually pitch up 30 degrees right after takeoff and it maintains that pitch while accelerating till about 10,000 where it caps out on speed ( for that ascent anyway) at about mach 2.8/2.9 and maintains that speed until it flames out... usually just a few seconds later.

Edit- Will try a little more retooling.

While I am doing that, any suggestions on which intakes to use and which not to?

Edited June 23, 2015 by annallia

[capi3101]

Just for point of clarification - you're having problems with Whiplash engines, right? You're not trying to go high on Wheesley engines? Because 15k is about as high as you can get on those things. Even the Whiplash these days doesn't get much above 26k, no matter how many intakes you put on the thing.

Sorry - I know this is a type of question up there with "is your computer plugged in". Just want to eliminate that possibility first before going on to other possibilities.

[Xannari Ferrows]

While I am doing that, any suggestions on which intakes to use and which not to?

Depends on what flight profile you're going for. A low altitude cruising flight would merit a few structural intakes, as they produce less drag, and take in more air in a denser field. High speed low altitude flight would merit a radial intake, a precooler, or a circular intake, as they have efficiency dependence on velocity. High speed high altitude flight would merit a ram intake, as they have increased intake efficiency at higher velocities.

Low speed high altitude flight is a difficult one. It isn't that easy to pull off in the first place.

[annallia]

Can't belive it was as simple as removing all but the ram intake...

Not only did it break mach4 shortly after this its new ceiling is 27,000... That I am more than happy with.

Edit- Also removed the advanced canards, not sure if that helped or hurt it or did nothing, either way I am happy with the new results for this one.

Edited June 23, 2015 by annallia

[mrclucks]

I recently started making ssto planes and accent path that I normally use is 45degrees up to 10km or so, then go to 10-5 degrees and Max throttle if not already. I'm easily able to make it to 19km before i start significantly losing thrust, but if you level out you should still be able to maintain altitude and speed.

Use ram intakes and turbojets with a 1:1 ratio (I usually add one or two more for good measure) .

I've tested planes in both .2 and .3 and that plane works just fine with multiple planes

[NathanKell]

1. KSP heights are 80% Earth heights. So 20km on Earth is 16km on Kerbin.

2. The Wheesley appears to be modeled on an F100 engine (in dry thrust not afterburner) so don't expect U2-level heights.