Orbit Temperature

[JimMetalsCeramics]

What is the typical temperature outside the Space Shuttle when it is in orbit?

 

[btrueblood]

Jim,

that's a tough question - if you mean "what is the temperature of an object in the orbiter's payload bay when in orbit", then the answer is a little easier, but still complicated.

Any object in orbit is affected by radiation effects only, and its equilibrium temperature is a function of its thermal emissivity, solar radiation absorbtivity, and how much of the object is exposed to sunlight.

When orbiting with the payload bay open ("normal" attitude), the bay and its doors are always oriented towards Earth. Also, cooling panels are arrayed along the orbiter bay doors (and I think along the interior walls too). This tends to make the radiation source environment a more moderate temperature, and the reduced amount of sunlight coming directly in on an object helps keep temperatures moderate too.

You might be able to download information regarding "GAS" can operating environments from NASA GSFC or MSFC websites. "GAS" stands for "Get-Away Special" and were small aluminum cans for experiments to be flown on the shuttle by schools and small companies, for a nominal fee. There were a lot of documents published by NASA that controlled and specified the care & feeding of the cans.

Outside the payload bay (say on the surface of the "black" thermal tiles on base of orbiter), the temperatures can get pretty damn hot. How hot would depend on the ratio of epsilon to alpha of the tiles, but some rough guesstimates would put the temp. about 450 F.

 

[JimMetalsCeramics]

You walk outside the shuttle and put a thermometer in space. What does it read?

 

[amorrison]

In "black" space it reads 4K
(ie Four degrees kelvin = -269 Celsius = -269 Centigrade)

 

[JimMetalsCeramics]

You're saying that stronauts are space-walking around in 4K areas?

 

[sailoday28]

What is the basis for the 4K ?

 

[amorrison]

The 4k is from the background radiation from the "Big Bang".
Yes the astronauts are in a 4k environment.

The heat transfer(astronaut suit heat loss) is occuring by only radiation as there is no surrounding fluid to produce conduction and convection cooling.

The radiation heat loss from the exterior surface of the space suit is mimimized by selecting a exterior coating that emits minimum heat transfer by radiation to "black" space.

 

[sailoday28]

the original question
You walk outside the shuttle and put a thermometer in space. What does it read?

Can't we say that the tip of the therometer is a portion of a "small sphere" that sees the sun? And then calculate its temperature after a radiation heat balance.

 

[amorrison]

Yes but the temperature will depend on the emmissivity and absorvitivity of the surface materials which are a themselves sometimes (usually?)a very nonlinear function of their temperature.

These radiation emmission/absorptivity curves for some materials are in some(few?) engineering heat transfer texts.

Note: if one assumes perfect reflection (from the hot heat source)and no emission (to space-cold) then the thermometer is completely decoupled from all heat transfer environments -thus the temperature will not/cannot change because there is no heat going in and no heat going out.

One simple situation that can be calculated easily however is if both surfaces are assumed black for all frequencies - - - a WILD assumption for real materials.

 

[unclesyd]

I have two sources that say the ambient temperature in space is 30K. Awaiting a number that you would design to.

The NICMOS IR Detector operates at 80K using mechanical refrigeration. That is a fair approach to space ambient if the 30K is right number. NICMOS initially operated on Nitrogen ice 77K.

The Space Suit, from the people who make the environmental control of same say the skin of the suits see -100°.F to 235°F in space.

 

[amorrison]

The 4K temperature is correct.

From

http://www.eorc.nasda.go.jp/ADEOS/Project/Octs.html

The infrared detector is cooled at 100K by a large radiation cooler. It faces the deep space at temperature of 4K, and emits heat of the detector. The electrical signals are amplified by the specefied gain in Analog Signal Processor, and then converted to digital signals. The digital signals processed in Digital Signal Processor are transmitted to bus module.

Please define the conditions for your 30K.

 

[JimMetalsCeramics]

Again. An astronaut steps out of the Shuttle. The temperature of space two feet in front of them is what??

 

[GregLocock]

Absolutely. It depends how you define temperature. In our everyday surroundings we can usefully talk about something that is strongly related to the RMS speed of the molecules in the item under consideration (although bear in mind that things like wind chill and under-shade requirements indicate that this simple approach is too simple even on earth). Once you get into other environments you cannot necessarily talk about rms particle speeds, and need to talk about heat balances.

Feynman said (loosely) that temperature is
a very misleading and complex measure.


Cheers

Greg Locock

 

[unclesyd]

ammorison4,
That is a different IR detector and not nearly as sensitive as the NICMOS IR Detector on the Hubble. NICMOS is cooled by a cryorefrigeration unit operating at the temperatures stated.

The 30K come from NASA literature on designing experiments for space.

The space suit details are for the stated participant in space suit design.

As stated I have an inquiry for some information about relevant temperatures .

I know the 4K is the astronomical temperature, but as you know anything you put in space to measure this temperature will influence the results.

 

[IRstuff]

An unpowered, unilluminated object, in deep space, will equilibrate to approximately 4 Kelvins. You can passively verify that temperature the same way that the COBE satellite measures the space background, e.g., through the blackbody emissions of the object in the microwave regime.

In any region close to the Earth, the temperature can vary from about -160ºC to over 200ºC, based on Table 11-43 "Typical Operating Temperature Ranges for Selected Spacecraft Components," from "Space Mission Analysis and Design," Wertz and Larson (eds) Kluwer 1999, ISBN 1884883108. They devote an entire chapter to the subject, and it's a non-trivial exercise to come up with any sort of answer.

Any non-complex object in Earth orbit will experience radiation from the Earth itself, and will therefore not reach the 4-Kelvin temperature of deep space.

As for infrared detectors, there are a variety of detectors that operate at different temperatures. The standard mid- and long-wave infrared detectors such as those used in Earth weather and surveillance satellites tend to be operated at around 77-80 Kelvins, which is the optimal temperature for Indium Antimonide and Mercury Cadmium Telluride. These detectors usually use liquid nitrogen or Stirling coolers running at liquid nitrogen temperatures for cooling.

Deep space and oold body detectors tend to be operated at 30-35 Kelvins, as that's the optimum temperature for the ultra-longwave infrared detector materials. These detectors usually use a helium cryocooler of some sort.


TTFN

 

[JimMetalsCeramics]

An astronaut leaves the Space Shuttle and space walks 20 yards away from it. The temperature surrounding him/her, independent of his/her space suit or body temperatures is what???

 

[sailoday28]

An astronaut leaves the Space Shuttle and space walks 20 yards away from it. The temperature surrounding him/her, independent of his/her space suit or body temperatures is what???
Unless the below data is old 3K.

From

http://www.unidata.ucar.edu/staff/blynds/tmp.html#Uni\

JimMetalsCeramics (Materials) Sep 7, 2004

3 K - The Temperature of the Universe
The sun and stars emit thermal radiation covering all wavelengths; other objects in the sky, like the great clouds of gas in the Milky Way, also emit thermal radiation but are much cooler. These objects are best detected by infrared and radio telescopes - telescopes whose detectors are sensitive to the longer wavelengths.
In 1965, Arno Penzias and Robert Wilson were conducting a careful calibration of their radio telescope at the Bell Laboratory at Whippany, New Jersey. The found that their receiver showed a "noise" pattern as if it were inside a container whose temperature was 3K - i.e. as if it were in equilibrium with a black body at 3 K. This "noise" seemed to be coming from every direction. Earlier theoretical predictions by George Gamow and other astrophysicists had predicted the existence of a cosmic 3 K background. Penzias' and Wilson's discovery was the observational confirmation of the isotropic radiation from the Universe, believed to be a relic of the "Big Bang". The enormous thermal energy released during the creation of the universe began to cool as the universe expanded. Some 12 billion years later, we are in a universe that radiates like a black body now cooled to 3 K. In 1978 Penzias and Wilson were awarded the Nobel prize in physics for this discovery.

A black body at 3 K emits most of its energy in the microwave wavelength range. Molecules in the earth's atmosphere absorb this radiation so that from the ground, astronomers cannot make observations in this wavelength region. In 1989 the Cosmic Background Explorer (COBE) satellite, developed by NASA's Goddard Space Flight Center, was launched to measure the diffuse infrared and microwave radiation from the early universe. One of its instruments, the Far Infrared Absolute Spectrophotometer (FIRAS) compared the spectrum of the cosmic microwave background radiation with a precise blackbody. The cosmic microwave background spectrum was measured with a precision of 0.03% and it fit precisely with a black body of temperature 2.726 K. Even though there are billions of stars in the universe, these precise COBE measurements show that 99.97% of the radiant energy of the Universe was released within the first year after the Big Bang itself and now resides in this thermal 3 K radiation field.

 

[btrueblood]

Jim Metals Ceramics wrote (several times):

"An astronaut leaves the Space Shuttle and space walks 20 yards away from it. The temperature surrounding him/her, independent of his/her space suit or body temperatures is what??? "

Jim, I apologize if my earlier post left you confused. Your question, though, has a flaw in it -- you're making a reference to something that doesn't exist. The right answer is "THERE IS NO TEMPERATURE IN SPACE" (for the same reason that no one can hear you scream). Temperature, you will remember from physics class, is a measure of the rms (or average) velocity of a collection of atoms/molecules. You can talk about the temperature of a space suit, or the temperature of some other object in orbit, but you can't talk about the temperature of something that isn't there (a vacuum). There are no molecules (or at least not enough to worry about from a heat transfer point of view) in space, or in any vacuum. In order to figure out "how hot a thermometer will read" in a vacuum, (or, by extension, what temperature will a given body equilibrate to) you should refer back to my original post - it depends on its radiation heat transfer properties. To look up the relevant chapters in a physics text, search for "Stephan-Boltzman" and "radiation heat transfer".

I spent many years working for a couple different rocket manufacturers, so I have a bit of experience in the subject. Whether to paint the fuel lines/valves with high-e paint, or wrap with gold foil, depended a lot on how well somebody could calculate the view factors, and what the surrounding objects were probably going to equilibrate to. The people who worked at the second rocket factory made a mistake somewhere in one set of view factor calcuations, and it ended up that our thrusters ran a bit too hot on the Magellan (venus radar mapping) mission. Never failed or caused too much trouble, but worrisome just the same. A while later, we learned that one of our customers made a mistake in the calcs for the pressurization lines for Mars Observer; the lines got too cold, the fuel vapors from the tank froze in the lines and got pushed into the oxidizer tank when the valve was fired prior to orbit insertion; bye bye orbiter.

Ben Trueblood (ex astro guy, now a mech design guy)

 

[jmw]

Of course, what any contact thermometer will tell is is its own temperature.
You hope for it to reach thermal equilibrium with its environment and for it to report on the temperature of that enviroment. Usually the mass of the temperature sensor is low compared to the mass of the enviroment.
Not in space.
A conventional thermometer might take a while to reach that point.

From our earth perspective space is a vacuum.
However, that isn't the same as saying that the density (matter distribution) is uniform. In near earth orbit there will be escaping gases etc. I would expect the sun to be the biggest source of ejected matter once we are significantly away from the earth (where is that?).

Within the solar system there is quiet a variation in density and once out of the solar system density drops off some more.

With this density variation will come a temperature variation. So while 4K may be the temperature of the universe, or as IRStuff says, the temperature in deep space, that is probably the mean temperature. It may not vary much between the stars but within the influence of a solar system it will surely increase.

So what is the temperature variation in different parts of the solar system? and what is the limit of the solar system if we use temperature as a boundary i.e. where is the limit where the temperature is indistinguishable from the mean temperature of deep space?





JMW

http://www.viscoanalyser.com

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[btrueblood]

Sigh.

JMW, you wrote:

"So what is the temperature variation in different parts of the solar system? and what is the limit of the solar system if we use temperature as a boundary i.e. where is the limit where the temperature is indistinguishable from the mean temperature of deep space?"

My reply: temperature variation of what? Of a massive object, including a "low-mass temperature sensor", answer: 4K. Reason: the variation of gas/plasma density just doesn't factor into the heat transfer, radiation dominates.

If you want to talk about the temperature of the gas/ionized gas/plasma/dust etc. that forms the interstellar medium, you can do so (do a google search on the terms interstellar medium, interstellar gas temperature, etc.), but be careful -- "temperatures" as used by cosmologists/astronomers are a tricky statistic having more to do with available energy (including ionization energy) than temperature as you or I learned in thermo class. Also remember that the typical density of the interstellar medium is .0001 molecule, atom or ion per cubic centimeter; here on earth we breathe a gas with a density of about 10^19 molecules per cubic centimeter. So, while some places in the solar system and outside of it may (we are told) have a "cloud" of gas measuring 10,000 degrees Kelvin, you could "stand" in the middle of that cloud and (without your suit heater on) freeze solid to 4 K. Why? Because there just isn't enough of that 10,000K around to affect you, either directly or by radiation transport.

Back to the original question, I guess the right answer would have been to ask "why do you want to know" If the answer came back "to see how cold my orbiting science experiment would get" see prior posts. If the answer came back "because I want to discuss interstellar plasma physics", then see the previous paragraph.