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Science: Everything explained by PV=nRT, F=ma=Gm(1)•m(2)/r^2

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Kepler said:
This is very strange. It doesn't make any sense unless you see it really, really large, and also maybe spin through some of the videos out there about the macro structure of the universe.
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One thing that I wonder about astrophysicists that work in that area- how do they deal with a time frame that is well outside the lifespan of this planet? We know that the Milky Way and Andromeda will collide, right? But that will happen after our sun runs out of energy, will grow into a red giant, and engulf the earth. We will quite literally be very much gone.
 
MichVandal said:
One thing that I wonder about astrophysicists that work in that area- how do they deal with a time frame that is well outside the lifespan of this planet? We know that the Milky Way and Andromeda will collide, right? But that will happen after our sun runs out of energy, will grow into a red giant, and engulf the earth. We will quite literally be very much gone.
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I quickly get out of my depth but there is this whole idea of the future light cone in Minkowski space which actually does try to grapple with this from the POV of error. The point at which the error factor dwarfs our ability to predict future events is much sooner than we would intuit. I know at least one guy here actually understands this so Ima leave it alone and if he wants to pick it up he will.
 
Forty-six years ago today, Viking I launched on the first ever mission to Mars. On July 20 that next year, it safely landed on Mars, and started sending high resolution images back to NASA after spending some time in orbit first. Its landing date was the seventh anniversary of Apollo 11 landing on the moon.
 
I want it I want it I want it I want it

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SpaceX has related that there is a shortage of LOX (relax Ralph) that may slow down the frequency of launches. Well I wondered, why doesn't Elon make his own propellants. So I googled how to and came upon this reference in Quora:
In an industrial setting, liquid oxygen is produced by “fractional distillation.” They feed air into the system and cool it way the hell down, and when you get to the condensation point of the gas you’re trying to sell, it just drips out and you collect it in a container.

Having said that, liquid oxygen is a cryogenic you do NOT want to deal with if you’re not set up and well-trained for it. LOX is sitting there in its little container actively thinking of ways to fuck you up. Not only is it capable of freezing things (like your fingers) so hard they’ll shatter if you tap them against the table (and you may as well tap them against the table, because any flesh frozen that hard dies instantly), it makes REALLY good explosives when mixed with any carbon-containing fuel.

John Drury Clark’s book Ignition! describes this…

If Tannenbaum’s mixtures were bad (Stan Tannenbaum was trying to make rocket monopropellants out of nitrogen tetroxide, and blowing up everything in sight in the process), that proposed at a monopropellant conference in October 1957 by an optimist from Air Products, Inc., was enough to raise the hair on the head of anybody in the propellant business. He suggested that a mixture of liquid oxygen and liquid methane would be an extra high-energy monopropellant, and had even worked out the phase diagrams of the system. How he avoided suicide (the first rule in handling liquid oxygen is that you never, never let it come in contact with a potential fuel) is an interesting question, particularly as Jet Propulsion Laboratory later demonstrated that you could make the mixture detonate merely by shining a bright light on it.
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Mad scientist, indeed.
 
Also, there are better rocket fuel stories. Chlorine Trifluoride is probably near the tops in my list. From Derek Lowe

"Iâ??ll let the late John Clark describe the stuff, since he had first-hand experience in attempts to use it as rocket fuel. From his out-of-print classic Ignition! we have:
â?It is, of course, extremely toxic, but that's the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively. It can be kept in some of the ordinary structural metals-steel, copper, aluminium, etc.-because of the formation of a thin film of insoluble metal fluoride which protects the bulk of the metal, just as the invisible coat of oxide on aluminium keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes.â?"


They spilled one ton of it once:
"And even if you don't have a fire, the results can be devastating enough when chlorine trifluoride gets loose, as the General Chemical Co. discovered when they had a big spill. Their salesmen were awfully coy about discussing the matter, and it wasn't until I threatened to buy my RFNA from Du Pont that one of them would come across with the details.

It happened at their Shreveport, Louisiana, installation, while they were preparing to ship out, for the first time, a one-ton steel cylinder of CTF. The cylinder had been cooled with dry ice to make it easier to load the material into it, and the cold had apparently embrittled the steel. For as they were maneuvering the cylinder onto a dolly, it split and dumped one ton of chlorine trifluoride onto the floor. It chewed its way through twelve inches of concrete and dug a three-foot hole in the gravel underneath, filled the place with fumes which corroded everything in sight, and, in general, made one hell of a mess.

Civil Defense turned out, and started to evacuate the neighborhood, and to put it mildly, there was quite a brouhaha before things quieted down. Miraculously, nobody was killed, but there was one casualty â?? the man who had been steadying the cylinder when it split. He was found some five hundred feet away, where he had reached Mach 2 and was still picking up speed when he was stopped by a heart attack."
 
aparch said:
I don't recall there being an Engineering thread, so this science thread will have to do: The New Frederick Douglass Memorial Bridge in DC is gorgeous. This photo is amazing.

https://twitter.com/DildineWTOP/stat...60089669545992
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Should be able to see it perfectly flying in and out of Reagan National at night. Gorgeous job. DC has changed so much in the 20 years I have been here. The architecture and planning are hypermodern and beautiful. The city has undergone as dramatic a revival as anywhere else in the country.

Being the center of a global empire is really good for your skyline.
 
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