FLL Team 90 Thermostat Data

[Jeremy Trains]

At the begining of the mission, before the payloads took off, the temperature stayed the same. When it started going up, the temperature dropped but then, the temperature went up and down, keeping it above 10 degrees celsius, which showed that the heater was working well. Then at about 140 minutes into the mission the temperature went to about 25 degrees celsius. That also showed that the heater worked very well during the mission.

 

The chart of the data is called FLL Team 90 ThermostatChart.xls and the original file from the NXT is called FLL Team 90 Thermostat.txt. Both of those files are on google groups under the page files. To get the temperature at a certain time I created a program to say the time at each temperature or degree. Then I combined the temperature and time to make the chart. 

[Brian Davis]

Very nice! It looks like your payload might have been much better
insulated than mine was. What did the inside look like? For instance,
was the temperature sensor very close to the heaters, or close to the
NXT, or close to the lid or side of the payload?

--
Brian Davis

[David Levy]

There are some pretty good pictures of the payload heaters location in
the payload, the relative size of the payload container to its
contents, as well as the position of the temperature probe. See the end
of the document uploaded by Pooja named: "FLL_Team_90_HALE_Payload.pdf"

Eric wrote:
> Also remember, that we filled the payload with the foam peanuts to
> help cushion the contents. Your students might want to think about
> whether that helped or hurt in terms of keeping the payload warm (I
> have my theories, but it should be an interesting exercise for them).
>
> Eric
>
To tell you the truth, the team stopped thinking of the readings as
measurements of "inside payload" temperature after you had revealed
something very interesting to the team:

from Eric's June 9 posting:
http://groups.google.com/group/hale-teams/browse_thread/thread/2a2cce1ceca342e3

" REMEMBER: the heater works via radiation, not conduction or convection
because there is no air. Thus, you want to position the heater in such a
way that it has direct line of sight to the component(s) you are trying
to keep warm.
Eric "

So this really became an exercise on measuring the temperature between
the resistors which were also in the proximity of the NXT battery
compartment. The latter being the component the team intended to keep warm.

WOULD ANYONE FROM FLL90 guess what impact the packing peanuts may have had?

David

[Eric]

True, but the heater was positioned right underneath the NXT right? So
I would agree that the peanuts would have kept the radiation from
reaching the motor and UV sensor, but the NXT should have been toasty
warm (which is the most important component).

On of the biggest problems we *think* student payloads commonly have
is that they are not well sealed. On the way up as pressure decreases,
the hot inside air gets forced out - which is not necessarily bad.
However on the way down, the cold outside air gets pushed in. The more
holes, the colder the payload gets - especially on the descent. We
have never done any experiments to confirm this, but we often see the
coldest temperature (inside) during descent, not ascent. Your payload
was actually quite well sealed - only small holes for the UV sensor
and pinwheel axle. What do you think about the impact of the peanuts?

Eric

On Aug 18, 10:31 am, David Levy <david.l...@restonrobotics.org> wrote:
> Brian Davis wrote:
> > Very nice! It looks like your payload might have been much better
> > insulated than mine was. What did the inside look like? For instance,
> > was the temperature sensor very close to the heaters, or close to the
> > NXT, or close to the lid or side of the payload?
>
> > --
> > Brian Davis
>
> There are some pretty good pictures of the payload heaters location in
> the payload, the relative size of the payload container to its
> contents, as well as the position of the temperature probe. See the end
> of the document uploaded by Pooja named: "FLL_Team_90_HALE_Payload.pdf"
>
> Eric wrote:
> > Also remember, that we filled the payload with the foam peanuts to
> > help cushion the contents. Your students might want to think about
> > whether that helped or hurt in terms of keeping the payload warm (I
> > have my theories, but it should be an interesting exercise for them).
>
> > Eric
>
> To tell you the truth, the team stopped thinking of the readings as
> measurements of "inside payload" temperature after you had revealed
> something very interesting to the team:
>

> from Eric's June 9 posting:http://groups.google.com/group/hale-teams/browse_thread/thread/2a2cce...

[David Levy]

"What do you think about the impact of the peanuts?"

I suppose one or more of the following:

1) Insulation: esp. for the UV sensor which was not in the vicinity of
the heating unit.
2) Volume: eliminated a large air pocket that could be detrimental to a
well sealed payload
3) Conductivity : possible statically charged packing peanuts could help
transfer the radiation generated from the heater ( but would there be a
negative impact on our electronics?)

Now you got me thinking about the peanut colors. I doubt DHL would have
used two types of packing peanuts so why did we get different types of
peanuts back ( green and white)? I guess the easy answer is that you
kept all the peanuts together in one bin. However I wouldn't rule out
the possibility that you intentionally used different packing materials.

OK those are my best guesses.

David

[Eric]

No particular meaning to the different colored peanuts. I keep them
for reuse - so I have a big box full of various colors.

Eric

[Brian Davis]

On Aug 19, 10:21 am, David Levy <david.l...@restonrobotics.org> wrote:

> "What do you think about the impact of the peanuts?"
> I suppose one or more of the following:
>
> 1) Insulation: esp. for the UV sensor which was not in the vicinity
> of the heating unit.

Well, think about this - did the UV sensor have a heat source? If not,
then it was maintaining it's temperature, if at all, based on the
amount of heat it initially had. It was indeed "insulated", in that it
had trouble exchanging heat... but it was insulated *from* the heat
source, so it likely got rather cold.

> 2) Volume: eliminated a large air pocket that could be detrimental to a
> well sealed payload

Well... why would a big air pocket be a problem? Upon descent, the
payload is essentially empty, so that amount of cold air (that
ultimately would be warmed by the payload components) pushed into the
payload on descent would be proportional to the empty volume...

> 3) Conductivity : possible statically charged packing peanuts could help

> transfer the radiation generated from the heater...

Actually, static electricity has nothing to do with heat transfer, so
the electrical properties of the packing peanuts I suspect are a
complete red herring (where did that term come from, anyway?).

> Eric wrote:
>
>> True, but the heater was positioned right underneath the NXT right? So
>> I would agree that the peanuts would have kept the radiation from
>> reaching the motor and UV sensor, but the NXT should have been toasty
>> warm (which is the most important component).

David, think about it like this. Without air in the payload, the only
way heat gets transfered is via radiation - which travels in straight
lines (only!). So for a bit of heat energy to escape the payload, it
has to travel in a straight line until it hits something... likely a
packing peanut within a cm or so. Then it is absorbed and re-emitted,
but probably in the other direction, not "outward" per say, just "in a
new direction". With lots of things to hit, this bit of heat (call it
a "photon"... it makes you sound smart :) ) has to take a whole lot of
bounces and reemissions until it can finally escape from the
payload... so it takes longer for heat to escape.

--
Brian Davis