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 drawde
Registered: 11/15/09
Posts: 5,268
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 Re: General Science Thread  [Re: Magash]
#818445 - 08/23/16 02:11 AM (8 years, 4 months ago) |
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King Koopa said:
The amount of pot that Gask smokes is equivalent to a guy shooting heroin on weekends
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Chemical Addiction
 
Registered: 11/20/14
Posts: 1,681
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Re: General Science Thread [Re: Data]
#818448 - 08/23/16 05:46 AM (8 years, 4 months ago) |
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agmotes mentioned earlier that a lot of the debris isn't very magnetic, I asked if we could use magnets to pull the debris into the atmosphere at an angle that would burn it up before hitting the ground.
Quote:
agmotes165 said:
Yea we could do that for part of the debris, but a lot of it is diamagnetic material, meaning that it doesn't react strongly to magnetic fields. It would also be very tricky to control and coordinate orbital maneuvers between either extremely distant magnets, or magnets on board another object in orbit. Even the slightest force between two objects can throw both of the object's orbits off.
I think current protocol for aging satellites is to initiate a controlled re-entry so that the satellite burns up in the atmosphere rather than float out there in orbit, loses contact with the control team, drifts out of orbit, and crashes into something else. That being said, there are several large satellites that have broken in orbit and are now adrift, some weighing as much as 18,000 lbs (Envisat)...which could generate some serious debris if they were to impact something else in orbit. 
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Sure. Don't expect me to compensate your wife and five retarded kids after I've drowned your exposed brain in my semen.
Spider Jerusalem
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Chemical Addiction
Registered: 11/20/14
Posts: 1,681
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how often does this debris enter the atmosphere on its own? or does it stay in orbit? I was just wondering if some of the "shooting stars" people see aren't actually space junk burning up as it decends.
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Sure. Don't expect me to compensate your wife and five retarded kids after I've drowned your exposed brain in my semen.
Spider Jerusalem
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Data
That Guy
Registered: 08/12/08
Posts: 4,038
Loc: Southwestern US
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There are several ways an orbit can lose energy. The most significant mode is through air drag, as the atmosphere does extend over 1000 miles above the surface of the earth (although it gets crazy thin up here). We'll focus on air drag since all other loss modes are negligible compared to this one.
Air pressure varies in low earth orbit from 700 nanopascals at 160km to about 10 nanopascals at 2000km. Since air pressure with respect to altitude is generally a linear relationship above the mesopause, we can easily come up with a y=ax+b style equation for air pressure P(h) through low earth orbit. If we apply the ideal gas law and plug in our pressure function, then a function for air density as a function of height rho(h) can be derived.
P(h) = (-3.75 e-13)h + 7e-7
rho(h) = (-1.64 e-18)h + 3.06e-12
If we look at the definition of drag force:
Fd = (1/2)rho(u2)CdA
where:
rho = rho(h)
u = velocity (m/s)
Cd = Drag coefficient
A = projected area of object (m2)
and consider the example of a standard 1U frame cubesat with the following characteristics:
m = 1.33 kg
Cd = 0.925 (average from tables)
A = .1 m * .1135 m = .01135 m2
and place it at the initial height and velocity of:
uinitial = 17500 mph = 7823.2 m/s
hinitial = about 141,430 meters above earth
then our drag function becomes
Fd = 0.00525u2rho(h)
our acceleration (slowing down) due to drag becomes
a = Fd/m = 0.00395u2rho(h)
and our velocity equation with respect to time (t) becomes:
u(t) = uinitial - a*t = 7823.2 - a*t
Now, because this drag force is so small, and the drop in orbit will occur very slowly, it is safe to assume that the difference in centrifugal force (the imaginary force that flings the object up) and gravitational force (the force pulling the object down) are in balance. This will allow us to define the height above the ground as a function of velocity:
Fc = centrifugal force = (m2u2)/r
Fg = gravitational force = (Gm1m2)/r2
Where:
m1 = mass of earth (5.972 e 24 kg)
m2 = mass of object (1.33 kg)
G = Gravitational constant
r = distance from center of earth to center of object = 6.371 e 6 meters + h
At this point, we can plug these definitions into a rough iterative spreadsheet, just to get a rough estimate of orbital decay time (this would take differential equations to actually solve the true path of the object, but the excel sheet will give us a pretty accurate result in this case).
I stepped the iteration time by 100 seconds per iteration, and calculated out 58 days in orbit (not 58 days until impact, its just that my calculation took up 50,000+ rows, and I got tired of running the simulation)...and only got a 380 meter loss of height (about 0.27% of the orbit height). Since our starting height was technically re-entered from the get-go (87 miles above the surface), a decay rate of 22 feet per day will be the absolute maximum decay rate a standard object will see up there.
The farther up you go, the slower you will need to go to maintain orbit (remember, geosynchronous sats are only moving at about 6900 mph, through much less dense air, and have a lot farther to decay (22,240 miles instead of 87 miles). Since the drag force depends on the density of the air, and strongly depends on velocity of the object, any objects in this area would be orbiting for a lonnnng time.
We won't even get into orbits higher than that...or the satellites that sit stationary with respect to earth in Lagrangian points. 
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“The Universe is under no obligation to make sense to you” -NDT
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Chemical Addiction
Registered: 11/20/14
Posts: 1,681
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Re: General Science Thread [Re: Data]
#818468 - 08/23/16 08:59 PM (8 years, 4 months ago) |
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Damn you made a simulation just to answer the question? that's what I call a devotion to science/math.
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Sure. Don't expect me to compensate your wife and five retarded kids after I've drowned your exposed brain in my semen.
Spider Jerusalem
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Data
That Guy
Registered: 08/12/08
Posts: 4,038
Loc: Southwestern US
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 I called it a simulation, but it's really just a big excel table lol.
And yea man, I love this stuff and love discussing it with other people. Ideas and questions are how people learn and grow, and maybe even come up wits "the solution" for a particular problem. For insrance, after our discussions, you might ponder and research and figure out the space debris solution, and that would be badass! 
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“The Universe is under no obligation to make sense to you” -NDT
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Data
That Guy
Registered: 08/12/08
Posts: 4,038
Loc: Southwestern US
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Re: General Science Thread [Re: Data] 1
#819578 - 09/24/16 11:51 AM (8 years, 3 months ago) |
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Anybody excited for the Europa announcement from NASA on Monday? It's not aliens, but I'm sure it'll be exciting nonetheless. 
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“The Universe is under no obligation to make sense to you” -NDT
Edited by Data (09/24/16 11:51 AM)
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poor boy
Village Idiot
Registered: 06/07/13
Posts: 16,230
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Re: General Science Thread [Re: Data]
#819590 - 09/24/16 09:26 PM (8 years, 3 months ago) |
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i read that a few days ago and instantly thought about you, in a non gay way... i think... yeah, not gay.
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Learning to love life by living through loss and mistakes
Lessons learned then gradually surfacing, Letting go, stripping naked to scream
I am not perfect nor do I strive to be, I am alive in this world of face first falls and public breakdowns
I'm a retarded, disfigured clown
Dying to be heard through the simple art of letting this heavy wall finally fall
I'm an equal being of no race, or color, a hallucination if you will
Sneaking into the lives of strangers, and letting them fall apart to a new rhythm just to feel better
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Data
That Guy
Registered: 08/12/08
Posts: 4,038
Loc: Southwestern US
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Re: General Science Thread [Re: poor boy]
#819596 - 09/25/16 08:04 AM (8 years, 3 months ago) |
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“The Universe is under no obligation to make sense to you” -NDT
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Chemical Addiction
Registered: 11/20/14
Posts: 1,681
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Re: General Science Thread [Re: Data]
#820310 - 10/17/16 03:14 PM (8 years, 2 months ago) |
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So I've been thinking about the space junk some more and if we can't use magnets, or drones to collect the debris could we physically deflect it with some sort of giant ramp like structure with basic maneuvering (up,down,left,right)?
Try and send it down at the correct angle to burn up the junk, or send it up to the edge of the of the gravitational pull of the planet to slow it down without sending it into space or hitting a satellite. Or finding a way to time the collision of the debri with the "ramp" and angle it properly to shoot it at the sun?
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Sure. Don't expect me to compensate your wife and five retarded kids after I've drowned your exposed brain in my semen.
Spider Jerusalem
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drawde
Registered: 11/15/09
Posts: 5,268
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King Koopa said:
The amount of pot that Gask smokes is equivalent to a guy shooting heroin on weekends
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Chemical Addiction
Registered: 11/20/14
Posts: 1,681
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Re: General Science Thread [Re: drawde]
#820317 - 10/17/16 06:19 PM (8 years, 2 months ago) |
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I figured if the deflector was moving the same way as the debris, just a little bit slower it could deflect the debris without being damaged
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Sure. Don't expect me to compensate your wife and five retarded kids after I've drowned your exposed brain in my semen.
Spider Jerusalem
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Chemical Addiction
Registered: 11/20/14
Posts: 1,681
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how to build your own tractor beam
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Sure. Don't expect me to compensate your wife and five retarded kids after I've drowned your exposed brain in my semen.
Spider Jerusalem
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Data
That Guy
Registered: 08/12/08
Posts: 4,038
Loc: Southwestern US 
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That was pretty neat, we studied standing waves on steel beams under cyclic motion in school. If you take a rope or a slinky, let it hang vertically, and shake the top back and forth, at particular shaking frequencies the rope/slinky will take on this shape.
This is called a vibrational mode, or a standing wave. In reality, the waves aren't stationary, but rather the initial wave travels down the rope/slinky, is reflected in a particular manner determined by the configuration of the end of the beam (as in, whether its attached to a stationary wall/floor, or free swinging, etc.), and overlays back over the original waves on its way back to you're hand. At certain frequencies (natural frequencies), this overlay ensures that certain points on the rope/slinky never move back and forth. The points that aren't moving are called nodes, and the points that have the maximum movement are called antinodes. There are (theoretically) an infinite number of vibrational modes, and each mode comes with an increasing number of nodes/antinodes, spaced closer together along the lenght of the rope/slinky.
When you set up a flat, horizontal steel beam in this manner (you have to mount it to a giant speaker core and use a much higher frequency than you're hand can achieve), then you can sprinkle a little salt or sand over the beam and the sand will line up across the beam at the nodes when one of the natural frequencies is dialed in.
In two dimensions (a horizontal flat plate either supported at the edges or in free space with the same speaker core for vibration input), the different vibrational modes (when sprinkled with sand to highlight the node lines) form interesting patterns. In the video below, the plate is supported in the center, which is also the point at which the vibrational input is transmitted into the plate (aka a Chladni plate).
In the case of the tractor beam, it gets a little complicated. The vibrating medium is the air, the source wave does not move in a straight line but rather radiates out from the speaker in a 3D ripple pattern (much like the 2D ripple pattern radiating out from the Chladni Plate), and the source wave shape doesn't necessarily reflect back over itself to create the 3D standing wave. This is why you have multiple source speakers, so that each source wave overlays over each other to create a 3D field of quasi nodes and antinodes. You can manipulate the relative timing of the source waves to change the spatial locations of the nodes, and thus a small object trapped in a 3D node can move with the node's changing location.
Notice that the objects tend to vibrate or spin while they are levitating, this is because the standing waves are actually constantly changing in the space around node, but the changes happen so fast that the object (which has a very small resistance to acceleration due to its mass) can't get up enough speed to escape the node before the pressure differences across the object flip in the opposite direction, thus keeping the object forever vibrating around the node point indefinitely. In one of the videos you posted, you'll notice that when he puts his hand above the dish to demonstrate how high the ball could levitate, the little ball falls out of the node. This is because by placing his hand into the acoustic field radiating out from the dish, he temporarily reflects some of the sound back down towards the dish, and changes the vibrational mode (I think that he actually destroyed the node field temporarily).
Standing waves can also occur with light. In fact, a standing light wave along a single axis is the heart and soul of all lasers. The optical material and length of the "resonating chamber" must be tailored to the frequency of light that you are trying to produce in order to work correctly. Additionally, complex 2D and 3D electron vibrational modes can be set up on metallic cylinders with various insulator materials to act as bandpass filters for microwave radio transmissions (used heavily in microwave ovens, cell phones, radioastronomy, radar, and high-bandwidth line-of-sight communications relays).
Basically, standing waves in any media are cool as shit 
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“The Universe is under no obligation to make sense to you” -NDT
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Chemical Addiction
Registered: 11/20/14
Posts: 1,681
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Re: General Science Thread [Re: Data]
#822535 - 01/10/17 05:35 AM (7 years, 11 months ago) |
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I wonder if something like that would ever replace conveyor belts, instead of a table with a moving belt, you have a stationary table that you can float stuff over, just give it a little push and it slides down to the end. kind of like air hockey but it never touches the table so there is no friction allowing you to move the object much faster so long as you have a way to slow it down.
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Sure. Don't expect me to compensate your wife and five retarded kids after I've drowned your exposed brain in my semen.
Spider Jerusalem
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Chemical Addiction
Registered: 11/20/14
Posts: 1,681
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actually not a table a duct, so you could have the speakers on all sides and try to keep the object in the middle, the duct could even curve, maybe a new way of shipping.
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Sure. Don't expect me to compensate your wife and five retarded kids after I've drowned your exposed brain in my semen.
Spider Jerusalem
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Data
That Guy
Registered: 08/12/08
Posts: 4,038
Loc: Southwestern US
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That's always possible, although larger objects would require crazy high amplitude sound waves, and really large nodes. For that application, a high temperature superconductor table surface, and a large magnet tray (to hold the object) would get the effect you are looking for, and the lack of high amplitude vibrations would be less destructive to the objects being moved.
Then again, strong magnetic fields can also mess with certain objects too.
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“The Universe is under no obligation to make sense to you” -NDT
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 Thebooedocksaint
Dead Dictator
Registered: 05/11/09
Posts: 5,730
Loc: Wild & Free
Last seen: 6 days, 3 hours
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Re: General Science Thread [Re: Data]
#822568 - 01/11/17 09:58 AM (7 years, 11 months ago) |
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Oh this is a thing.
Oh your name is data now.
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"Je pense, donc je suis (I am thinking, therefore I am)." -Rene Descartes
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Data
That Guy
Registered: 08/12/08
Posts: 4,038
Loc: Southwestern US
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Ya bruh 
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“The Universe is under no obligation to make sense to you” -NDT
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TrueHerbCrystal
Uncertified Oregrowian
Registered: 02/07/09
Posts: 1,352
Loc: Emerald City
Last seen: 6 years, 2 months
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Re: General Science Thread [Re: Data]
#822975 - 01/25/17 02:42 AM (7 years, 10 months ago) |
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Do u believe a monkey/human hybrid is possible?
If so, how much time into the future is needed to create such a beast?
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