Temperature relation to electronics

[casiothrow]

Does anyone have any experience with the effects of temperature on components in an electronics bay during a flight to say, 25,000 feet? The temperature at higher altitudes becomes low at 25000 feet, and I would like to know if there are any ways I can find out how components such as an altimeter (types such as a micropeak) and a gps (for instance, a bigRedBee) will fare. Would they still operate, and if so, for how long?

I feel like I am missing some obvious information somewhere I can find out.

 

[heada]

Does anyone have any experience with the effects of temperature on components in an electronics bay during a flight to say, 25,000 feet? The temperature at higher altitudes becomes low at 25000 feet, and I would like to know if there are any ways I can find out how components such as an altimeter (types such as a micropeak) and a gps (for instance, a bigRedBee) will fare. Would they still operate, and if so, for how long?

I feel like I am missing some obvious information somewhere I can find out.

At 25k feet there should be no issue. Some of the sensors that are out there have temp compensation built into them as well.

 

[cerving]

All of the integrated digital baro sensors have temperature compensation built into them, the issue is how responsive they are to rapid temperature changes. The short answer is "not very". There was another thread on this subject recently, and it also touched on correction of the altimeter's barometric pressure due to ambient ground baro pressure. For most sport flights, the baro sensor's internal corrections to the STP model is "good enough". BTW, most of the commercial components are also rated to -40C, so low temperatures aren't an issue as far as the actual electronics go.

 

[Voyager1]

Typically, active electronic components are rated to -40 C. The temperature at 25,000’ is about -35 C.

 

[manixFan]

I have flown to 25,000' many times and honestly never really thought about the temperature issue, the rocket spends so little time at that altitude that it likely does not cool off very much. I've never noticed anything unusual on the temperature plots from the altimeters that include that information.

The bigger issue going to 25,000' is how fast you are going to get there. Many of my flights to that range are Mach 2+ and the paint and sometimes the parts suffer a fair amount of 'Mach rash' form the intense surface heating due to friction. So for me I've been far more concerned about heat than the cold temps.

I've also flown with others who have gone much higher and I can't recall a single temperature related issue with the electronics. In all the discussions I've seen about Jim Jarvis' high flights past 100,000, I again don't recall any issues with electronics and temps. But maybe he'll chime in and verify that for sure.


Tony

 

[OverTheTop]

One of the biggest temperature problems you are likely to strike is heating on the pad. I have had several of the mini HD cameras shut down before flight because they overheated in the sun. That was with a white cowling over them too.

Thermal inertia and short durations at altitude will not likely cause you any temperature problems during flight.

 

[OverTheTop]

Here is a MD 54mm flight on an L640DT to about 21500', M1.8 IIRC. You can see the temperature in the NC from launch to landing.

 

[cerving]

That pretty much confirms what I said earlier... the temperature sensor can't keep up with the rocket, although it's interesting that it's registering 10C cooler at landing than at launch (which it of course was not!). I think you can see that given some soak time (i.e. when it's under chute for awhile) the temperature sensor gradually starts to reflect the ambient temperature, but it's still lagging way behind; I would guess that the 30.5C reading was probably closer to what it was at 21,500'. I've seen this behavior in three different MeaSpec/TE sensors, and three different Bosch sensors, the temperature sensor on them are all less than ideal for rocketry. Sometimes you have to make compromises for board space and complexity... using the integrated temperature sensor instead of adding something with a higher slew rate (at the expense of cost, power, and board space) is one of them.

 

[OverTheTop]

although it's interesting that it's registering 10C cooler at landing than at launch (which it of course was not!)

It was actually 10C cooler on landing. The rocket on the pad gets some serious heating in the sun. The convective airflow on the way down takes it back closer to ambient, which was around 30C on that launch day.

 

[cerving]

So that's even worse than I thought... the temperature should have been significantly less than 30C at apogee. You do see how it tends to equalize given enough time, though.

 

[JimJarvis50]

I've also flown with others who have gone much higher and I can't recall a single temperature related issue with the electronics. In all the discussions I've seen about Jim Jarvis' high flights past 100,000, I again don't recall any issues with electronics and temps. But maybe he'll chime in and verify that for sure.

Tony

Attached is data from a flight to 175K. It looks like the temperature drops from about 106F on the pad to 64F at the end of the flight. My experience is that the electronics doesn't "see" the cold temperatures. I suspect that is because there is no air to cool them down.

Jim