Command Pod Superheating during launch

[SanderB]

Hi all,

I'm trying to launch my rescue rocket with an empty command pod and so far I've lost several due to overheating. I think I launch a pretty normal ascent profile, but while ascending it will super heat, apparantly due to convective flux or something.

Video of the superheating.

http://youtu.be/I4yMb2YqwGM

I don't understand it, the command pod's convective heating flux will spike and plummet near instantly upon me throttling back and forth to 100%. It doesnt make sense to me, why would the command pod superheat due to cv flux but not the parachute? And why does it superheat at all? It doesn't seem realistic.

[StormKat]

Slow down. Your ascent is way too fast.

[Trenchfoot]

Yup. If you start seeing white effects and then red effects on the way up, not only are you wasting fuel, your obviously frustrating yourself. Patience, slow down.

[SanderB]

I don't actually see any heating effects. Up to even 70km near orbital velocity the mk1 pod will be at temperatures of 1200-1400° and the conv flux keeps it there all the way. All the while no re entry effects are visible or any glowing of any part. Almost any part pointed straight into the incoming atmosphere I test at the same altitudes and same velocities have 10-100x less conv flux than the mk1 command pod. How is that even possible?

Edited May 1, 2015 by SanderB

[Valerian]

Hi all,

I'm trying to launch my rescue rocket with an empty command pod and so far I've lost several due to overheating. I think I launch a pretty normal ascent profile, but while ascending it will super heat, apparantly due to convective flux or something.

Video of the superheating.

http://youtu.be/I4yMb2YqwGM

I don't understand it, the command pod's convective heating flux will spike and plummet near instantly upon me throttling back and forth to 100%. It doesnt make sense to me, why would the command pod superheat due to cv flux but not the parachute? And why does it superheat at all? It doesn't seem realistic.

Like the others explained you are going too fast and you are wasting fuel because of too much air resistance.

You should take a look at the terminal velocity table, which indicates the most fuel efficient speeds depending on your altitude: http://wiki.kerbalspaceprogram.com/wiki/Kerbin#Terminal_Velocity_Table

An easy rule I like to follow is to start at full thrust, then to lower your thrust once you hit 100 m/s in order to slowly and gradually increase the speed up to 250m/s when you reach 9000m. After that you can use full thrust and it should be fine.

This was for KSP before 1.0, but it seems to be still more or less valid.

[NathanKell]

Nope, it's totally and completely invalid. That's souposphere numbers.

[jarmund]

For starters, you're going too fast too early.

Secondly, it seems to me that probecores generally don't like heat/drag very much. I've lost multiple probes because of this. In the end, I got around this by just wrapping it in a fairing.

[SanderB]

I've been thinking about fairings and it doesn't seem very convincing because their mass is about 20% the mass of the payload, and that is fitting the fairing as tight as I can without clipping parts through it. At 0:51 in my video I show the parachute being at a stable temperature of 310 whereas the mk1 pod at the same point is 610 under almost the same conditions, how does that make any sense? Both parts face into the oncoming air stream, the parachute being smaller maybe should get a little less flux, but as it stands it gets a whole lot less heat flux than anything else even though it is in front of everything else and under almost the same circumstances as the mk1 pod. I don't understand the difference, I'm not convinced that this is merely about going too fast too low in the atmosphere because there is a very significant disparity between the chute and the mk1 pod.

Edited May 1, 2015 by SanderB

[Alias72]

If you want to gun it you will need to start with a much lower TWR. Drop your TWR to about 1.1-1.2 and you won't over-accelerate.