This should be easy to answer and the last part of this contention I'm not fully understanding. Was the radiation from the sun completely absorbed by the outer hull then (during transit)? And did the craft rotate slowly to avoid hotspots and assist cooling. Everything making sense so far.
The spaceship both absorbed and radiated heat away. Any object in space will eventually reach an equilibrium temperature where the absorption and radiation are in balance. What that equilibrium temperature is depends on many factors, such as how much sunlight falls on it, the optical properties of the materials (black vs. white), etc.
The Apollo spacecraft was designed to reflect away a large amount of the radiation that fell on it, thus its equilibrium temperature was on the coldish side. The capsules were keep warm on the inside because of waste heat generated by the electronics. In fact, this heat was excessive and the spacecraft was equipped with a cooling system to remove the unwanted heat. A coolant was used to transport heat from the electronics to radiators on the outside of the service module.
This is why Apollo 13 got cold when most of the electronics were turned off. Without heat being added by the electronics, the spacecraft began to reach its cold equilibrium temperature.
Post by PhantomWolf on Mar 28, 2010 16:08:29 GMT -4
I just thought I might point out that "Radiation" in terms of Heat Transfer, which is what we are talking about here, is different from "Radiation" as in the Ionizing particle or wave stuff that will kill you over time and we talk about elsewhere. Same word, two totally different meanings.
It must be fun to lead a life completely unburdened by reality. -- JayUtah
"On two occasions, I have been asked, 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question." -- Charles Babbage (1791-1871)
What that equilibrium temperature is depends on many factors, such as how much sunlight falls on it, the optical properties of the materials (black vs. white), etc.
You should point out that the optical properties are important at two widely separated wavelengths: visible and the far IR (around 10 microns). They can be the same or they can be very different.
The optical properties at visible and near IR wavelengths (i.e., how reflective the material is to the eye) determine how readily it absorbs heat from the sun. The optical properties in the far IR determine how readily it radiates heat to deep space.
You can get optical coatings for spacecraft with all four combinations: good reflectors at both visible and far IR; good reflectors at visible, good absorbers/radiators in far IR, and so on.
Note that being a good radiator in the far IR means you're also a good absorber in the far IR. This isn't a big deal in deep space where you're exposed to the visible/near IR from the sun surrounded by a lot of cold sky, but it's a big deal in earth orbit and on or in orbit around the moon because of the thermal radiation from both those bodies. It's not possible to design a radiator that can dump waste heat while facing the daytime moon; it has to face the dark sky while being shielded from the lunar surface.
This meant that the lunar module needed another way to get rid of waste heat while sitting on the moon, and that method was to evaporate water. In the future I expect to see sophisticated radiator designs on the moon that are oriented to be shaded from the lunar surface and ideally the sun, though strangely enough the latter is actually less important since you can use materials that are reflective in visible but good radiators in the far IR.
Post by capricorn1 on Apr 10, 2010 17:04:54 GMT -4
Ok, a few more anomalies to debunk. It's always youtube these days, but that's where they can be seen easily I suppose. So...1/ watch?v=UmIWhzTzLn0 (I won't glorify the url).... what's going on with those 'wires'. I don't buy any of this but can't explain it.
2/ TURN OFF SOUND watch?v=cSjgmLoQ48E 43 seconds he falls upwards. What is going on here, it doesn't look like he pushed up from the surface. And at 1 minute, the camera tracks upwards, was this remote control, how did they get it so tight?
Post by Jason Thompson on Apr 10, 2010 17:22:45 GMT -4
Wires: The footage was transmitted on a TV screen, but was recorded for posterity on film (by aiming a film camera at a large monitor). Film is prone to vertical scratches (due to the way it is run through the equipment) and other problems. At one point in their slo-mo replay you can see a couple of other bright anomalies, but since they don't resemble wires they gloss over them. Odds are that at some point vertical scratches on the frame will intersect the astronauts. I haven't looked in detail at the whole lot, but I would bet you could also find examples of vertical scratches that look just like those 'wires' that don't happen to intersect the astronauts. Of course, those clips are never going to be shown to you by a conspiracy theorist....
Falling upwards: His hand is on the other astronaut. He is pushing up off something, just not the surface. Additionally, the pressurised spacesuit had a natural tendency to adopt the 'standing up' conformation, so combine a push-off with a springy suit and the ower gravity, and consider the fact that his muscles still exert the same force as they do on Earth when he's trying to stand up, and you can expect something like this to occur.
Camera tracking: yes, it was remote controlled from Earth. There was a signal delay effect of a few seconds, so quite often you'll see the camera react late to things that happen on the screen (for example an astronaut pops out of frame, and it takes a while for the camera to adjust so he's back in shot).