|
Post by twik on Nov 16, 2011 15:39:06 GMT -4
Appearance - Vivid orange gas according to wikipedia the gas release at white sands was accidental release, not at higer temperature. if nitrogen dioxide was the gas most likely would have been vivid orange not brownish red or red would this be more correct? Well, if you accept wikipedia, they have a photo of concentrated and less concentrated nitrogen dioxide at en.wikipedia.org/wiki/Nitrogen_dioxide . If I were to describe it, "vivid orange" would not be my choice. The concentrated form is rust-red. The less concentrated form is more orange, but that's because it's paler.
|
|
|
Post by gillianren on Nov 16, 2011 15:54:46 GMT -4
i must have been napping the day my kindergarten class dicussed Roy G. Biv's color scheme Were you awake in any science?
|
|
Ian Pearse
Mars
Apollo (and space) enthusiast
Posts: 308
|
Post by Ian Pearse on Nov 16, 2011 16:31:47 GMT -4
To add my two-penn'orth to the oxidiser/fuel debate, how about this site: www.ehartwell.com/LM//SCATSystems.htmScroll down to the propulsion systems sections. A good read, that whole site.
|
|
Ian Pearse
Mars
Apollo (and space) enthusiast
Posts: 308
|
Post by Ian Pearse on Nov 16, 2011 16:44:49 GMT -4
now let me ask again how did the mylar film not get damaged by the 1000 degree rocket stream as the lander touched down on the moon? Could you explain why you think it should, bearing in mind the points made earlier in the thread about the way fluids move?
|
|
|
Post by randombloke on Nov 16, 2011 16:46:57 GMT -4
now let me ask again how did the mylar film not get damaged by the 1000 degree rocket stream as the lander touched down on the moon? Not until you tell me why my oven doesn't melt. I know it was a couple pages back, but it's really quite a simple premise; my gas oven burns natural gas, which has an adiabatic flame temperature of a little over 1900 °C. It is made of mild steel which has a melting point of something around 1400 °C. One of those numbers is smaller than the other; so why does my oven not melt when I leave it on for hours at a time?
|
|
|
Post by trebor on Nov 16, 2011 16:49:08 GMT -4
no heat is introduced or removed. Do you know the difference between heat and temperature? so exhasut gas if, what did you calculate was 1000 degrees at the end of the nozzle, then it will be very close to 1000 degrees period as it expands out into the vacuum. False. As the gas expanded the temperature would fall. and no i did not sleep in science class By all appearances also false.
|
|
|
Post by ka9q on Nov 16, 2011 17:08:31 GMT -4
Well, if you accept wikipedia, they have a photo of concentrated and less concentrated nitrogen dioxide... Actually they're both pure samples. They appear different because they're at different temperatures. At very low temperatures you have pure N 2O 4, which is colorless. As the temperature increases, it starts to dissociate into NO 2, which is red/orange/brown/pick-a-color. Think about lots of NO 2 molecules bouncing around. At low temperatures, it's common for two NO 2 molecules to hit each other and have their nitrogen atoms stick together, forming N 2O 4. But they're not stuck together very tightly, so eventually the N 2O 4 molecule bounces into another molecule and gets knocked apart into two NO 2 molecules again. This goes on continuously, so at any temperature you get what's called an equilibrium mixture of NO 2 and N 2O 4. The higher the temperature, the faster all the molecules move, knocking the N 2O 4 molecules apart that much sooner. Also, faster moving NO 2 molecules are more likely to just bounce off each other instead of joining. The fraction of N 2O 4 falls, the fraction of NO 2 increases, and the redder it becomes.
|
|
|
Post by trebor on Nov 16, 2011 17:08:42 GMT -4
try this walk outside and turn on the hose, wait make it a fire hose just for fun. point it strait down at the ground from say 6 feet on down to 2 feet, and you tell me where the water goes. And the point of this is? The water in the hose is not a gas, also outside there is atmosphere.
|
|
|
Post by ka9q on Nov 16, 2011 17:20:43 GMT -4
The stars are there, but they cannot be seen because, with sunlight flooding the spacecraft, the pupil of the eye involuntarily contracts, and the light from the stars is too dim to compete with the reflected sunlight, as both enter the eye through the tiny aperture formed by the contracted pupil. No, to see the stars, the pupil must be allowed to relax, to open wide enough to let the starlight form a visible image on the retina, Looks like Collins has fallen prey to a common misconception. The pupil responds very quickly to light level changes, but it only provides a small range of sensitivities. The real factor is the sensitivity of the retina, which slowly increases in the dark to far larger values than in bright illumination. This slow response of the retina almost certainly accounts for the inability of most of the astronauts to see stars during the daytime. Although from time to time they may look at black sky without much other light coming in, they usually don't do it long enough for their retinas to dark-adapt enough to see the stars. Also, as you age the iris of your eye becomes less able to open widely, just as your lens becomes less able to change focus. But older people can still adapt to a wide range of light levels. Some drugs, notably opiates, also shrink the iris quite dramatically but people on painkillers can still see in dim light.
|
|
|
Post by randombloke on Nov 16, 2011 17:29:14 GMT -4
how do you guys make the boxed text of posted info? We learned how to use the board instead of triple-posting like a rube. And, your answer, please? About ovens and melting?
|
|
|
Post by trebor on Nov 16, 2011 17:34:37 GMT -4
trebor whats the difference? Care to answer my question... Here it is again : Do you know the difference between heat and temperature? you guys were dead wrong concerning the laws of thermodynamics in a vacuum False. Incidentally, when quoting text from elsewhere it is good practice to give a reference. Is from : 2ndlaw.oxy.edu/entropy.htmlI am curious as to why you have quoted a section on entropy which does not mention temperature at all as your example.
|
|
Ian Pearse
Mars
Apollo (and space) enthusiast
Posts: 308
|
Post by Ian Pearse on Nov 16, 2011 17:45:17 GMT -4
...if the oven is in a vacuum...then it would melt Why? Explain please.
|
|
Bob B.
Bob the Excel Guru?
Posts: 3,072
|
Post by Bob B. on Nov 16, 2011 17:46:13 GMT -4
concening the temperature change of exhaust gas from a rocket engine into a vacuum Entropy and the second law of thermodynamics A gas expanding into a vacuum is the example that so many textbooks illustrate with two bulbs, one of which contains a gas and the other is evacuated. Then, the stopcock between them is opened, the gas expands. In such a process with ideal gases there is no energy change; no heat is introduced or removed. From a macro viewpoint, without any equations or complexities, it is easy to see why the entropy of the system increases: the energy of the system has been allowed to spread out to twice the original volume. It is almost the simplest possible example of energy spontaneously dispersing or spreading out when it is not hindered. so exhasut gas if, what did you calculate was 1000 degrees at the end of the nozzle, then it will be very close to 1000 degrees period as it expands out into the vacuum. and no i did not sleep in science class The expansion is isentropic, i.e. entropy is constant. As the volume increases, pressure and temperature decrease.
|
|
Bob B.
Bob the Excel Guru?
Posts: 3,072
|
Post by Bob B. on Nov 16, 2011 17:47:51 GMT -4
now let me ask again how did the mylar film not get damaged by the 1000 degree rocket stream as the lander touched down on the moon? The stream was wasn't directed at the Mylar EDIT, Oops!
|
|
Bob B.
Bob the Excel Guru?
Posts: 3,072
|
Post by Bob B. on Nov 16, 2011 17:50:44 GMT -4
yes please explain it to me again how exhaust gas bouncing off the moon produces laminar flow away from the lm. The same way as when to turn on you kitchen faucet the water stream spreads out radially across the bottom of the bowl. try this walk outside and turn on the hose, wait make it a fire hose just for fun. point it strait down at the ground from say 6 feet on down to 2 feet, and you tell me where the water goes. Radially outward.
|
|