High-speed, low-tech plane cooling solutions

[aluc24]

Hi all,

I started a new career in 1.0.5, and now I arrived at a stage where I have unlocked Wheesley engine. Since I like Kerbin a lot, and often do science missions that require me to travel very long distances, I designed a high-speed 3 engine bird, called the Traveler (needs a better name, I think):
[URL="https://static.dyp.im/Thbz3OBkGP/cf405a7380dfd38f29c6ed6a9586d229.png"]
[IMG]https://static.dyp.im/Thbz3OBkGP/large/cf405a7380dfd38f29c6ed6a9586d229.png[/IMG][/URL]

Now it flies okay, can recover from any kind of stall (including spin), has a lot of power, and at 5° pitch and 10,000m altitude it can cruise at 500m/s with a range of around 3500km, almost enough to circumnavigate Kerbin. It even has a emergency parachute. Part count is exactly 30, so I don't even need to upgrade SPH yet.

The only problem is that 5 minutes into cruise mode, it starts overheating. First, the engines, then random parts all over. If nothing is done, engines explode after around 20min or so.

I thought the smart thing would be to add small radiators in a way that would add as little drag as possible. However, radiators are the first to overheat, and in the end, seem to be doing nothing to prevent engine overheat.

I have not yet unlocked precoolers or any of the fancy stuff. I know I could just throttle down, but that would defeat the purpose of the plane.

Any ideas on how I can keep the engine temperature down at low tech level?

[cantab]

Throttling down does sound like the best option. I'd speculate you can go to 80-90% throttle and that will do the trick, any speed drop will be small.

[aluc24]

I tried throttling down one notch, and it brings the speed to 400m/s, requiring higher pitch-up, ruining fuel economy due to unsustainable altitude. Any other solutions?

[GluttonyReaper]

More wing surface might work, gives you more lift, but also acts as heat sinks, or at least it used to.

[aluc24]

[quote name='GluttonyReaper']More wing surface might work, gives you more lift, but also acts as heat sinks, or at least it used to.[/QUOTE]

Yeah, I tried that, but it didn't seem to help the engines. And I really want this thing to go as fast as possible :/

[aluc24]

Also, after several experiments I noticed that even at half throttle, engines still overheat.

[More Boosters]

Well if you fly a bit lower you'll go through more air which results in more heat getting convected away per second.

[aluc24]

[quote name='More Boosters']Well if you fly a bit lower you'll go through more air which results in more heat getting convected away per second.[/QUOTE]

I tried that, but it doesn't seem to work...

[aluc24]

I have attempted around 20 more test flights. It appears that no matter what altitude, speed and throttle level I choose, engines still overheat. Any advice?

[Zephram Kerman]

Some thoughts:
• maybe it's not the engines causing the overheat, but everything;
• radiators seem to work in space, so try "Dark Horse" profile, completely out of atmo for straightaways, turn while pulling out of the dive;
• maybe the thermo settings aren't quite realistic, you could tweak them to what makes sense for your use.

[lrd.Helmet]

Well the wheesley is basically a high bypass engine, which is made for subsonic flight. And since you are flying at 500 m/s that's a lot faster than the speed of sound. The engines and intakes simply can't handle that.

[More Boosters]

I could always barely get past 343 m/s and you're going with 500... You're pushing the envelope hard and the envelope doesn't like it.

Just hang in there until you can get Panther, then you can cruise around at 15km and at over Mach 2 easily.

[Rocket Farmer]

I was just doing a wheesley test contract and noticed the same issue. Internal temperatures climbed whenever I pushed over about 330 m/s (about the speed of sound) the internals started hearing up faster than the external skin. This occurred at 3,000 m above sea level so being low isn't the answer.

It probably is a hard cap allowing short term bursts of speed but not long-term cruising.

Alternatively maybe try going higher. I was able to get wheesleys cruising over 12,000m with an optimal flight pattern. Going higher with significant deployed radiators might help while not running at 100% thrust.

[aluc24]

[quote name='Rocket Farmer']I was just doing a wheesley test contract and noticed the same issue. Internal temperatures climbed whenever I pushed over about 330 m/s (about the speed of sound) the internals started hearing up faster than the external skin. This occurred at 3,000 m above sea level so being low isn't the answer.

It probably is a hard cap allowing short term bursts of speed but not long-term cruising.

Alternatively maybe try going higher. I was able to get wheesleys cruising over 12,000m with an optimal flight pattern. Going higher with significant deployed radiators might help while not running at 100% thrust.[/QUOTE]

Thanks... Tried going higher, but it's impossible to sustain supersonic speed there. It appears my high-speed plane idea will have to wait...

[sal_vager]

How hot do you get? I'm only checking with the Aeris 3A currently but the internal temperature seems to stabilize just above 900k and skin at 720k at 8km and 330m/s.

[aluc24]

[quote name='sal_vager']How hot do you get? I'm only checking with the Aeris 3A currently but the internal temperature seems to stabilize just above 900k and skin at 720k at 8km and 330m/s.[/QUOTE]

I'm not sure how to view temperatures in numbers, but the bars fill up all the way, and parts explode, starting with engines.

[BlueCanary]

Maybe the engines being so close together is causing problems? If they were more seperated, maybe with some winglets added to the engine to radiate away heat, would that help?

[cantab]

[quote name='Rocket Farmer']I was just doing a wheesley test contract and noticed the same issue. Internal temperatures climbed whenever I pushed over about 330 m/s (about the speed of sound) the internals started hearing up faster than the external skin. This occurred at 3,000 m above sea level so being low isn't the answer.

It probably is a hard cap allowing short term bursts of speed but not long-term cruising.[/QUOTE]I think you're right, actually. I remember hearing about the turbofans being rigged to overheat if you go too fast in them.

[samstarman5]

It sure does sound like the Wheesley is your culprit. If you are close to the next tier of aero-engines, then there is nothing wrong with taking your design over to sandbox and trying it with a higher-tier engine type, and see how it performs. Can just call it computer simulation.
Don't give up on this design. That is a nice build, and having it at 30 parts is a boon in itself.

[aluc24]

[quote name='BlueCanary']Maybe the engines being so close together is causing problems? If they were more seperated, maybe with some winglets added to the engine to radiate away heat, would that help?[/QUOTE]

Well, it's internal heat, so I'm not sure if that could be it...

[quote name='samstarman5']It sure does sound like the Wheesley is your culprit. If you are close to the next tier of aero-engines, then there is nothing wrong with taking your design over to sandbox and trying it with a higher-tier engine type, and see how it performs. Can just call it computer simulation.
Don't give up on this design. That is a nice build, and having it at 30 parts is a boon in itself.[/QUOTE]

Okay, I'll have to do that. Anyway, it somewhat beats the purpose of a low-tier plane. I really wanted to make a supersonic plane at as low tier as possible :D

[aluc24]

Tried it with Panthers. At 5° attitude, plane levels out at 12000m and 600m/s with no overheats. Fuel consumption is lower, speed is higher, engine weight is actually less. Is it just me or are Panthers overpowered? Sure, they're next tier after Wheesleys, but usually new tier parts don't make older ones obsolete in KSP.

[GDJ]

You think the Wheezley's are bad at supersonic overheating? Try a Goliath. 3 minutes at 380 m/s and BOOM!

Basically any high bypass jet engine is going to overheat when pushed over 295 m/s. You're fighting air friction and probably too lean a burn.

[martinborgen]

If your only concern is going as high and fast as possible, then yes, the jet engines will all be less and less useful.

[Captain Vlad]

[quote name='BlueCanary']Maybe the engines being so close together is causing problems? If they were more seperated, maybe with some winglets added to the engine to radiate away heat, would that help?[/QUOTE]

I've experienced heat problems with engines being mounted right next to each other, so this was what I was thinking too. I've never encountered it with the Wheesley, but I've never tried sustained high-altitude, high-speed flight with a triple-Wheesley before.

[quote name='aluc24']Sure, they're next tier after Wheesleys, but usually new tier parts don't make older ones obsolete in KSP.[/quote]

I still use the Wheesley's quite a bit. The thrust-reverser makes them VERY handy for rough-field landings.