Starship Asterisk*

BDanielMayfield wrote:
So, according to your calculations Art, trill seeking interstellar travelers could windsurf such jets? Gnarly, dude!

http://en.wikipedia.org/wiki/Sunjammer_%28spacecraft%29 wrote:

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<<Sunjammer is a solar sail constructed by LGarde for NASA. The largest solar sail to be constructed as of 2013, Sunjammer was named after a 1964 Arthur C. Clarke story of the same name, in which several solar sails compete in a race across the Solar System. Sunjammer is slated to launch in January 2015 as the secondary payload of a SpaceX Falcon 9 rocket, along with the Earth observation satellite DSCOVR.

Constructed of Kapton in order to withstand the extreme temperatures of space, Sunjammer has a width and height of 38 metres, giving it a total surface area of over 1,200 square metres and making it the largest solar sail as of 2013. Despite its huge surface area, Sunjammer has a thickness of only 5 μm, giving it an extremely low weight of about 32 kilograms and allowing it to be stored in a space the size of a dishwasher. Once in space, the large surface area of the solar sail will allow it to achieve a thrust of about 0.01 N—roughly the weight of a sugar packet. To control its orientation, via this its speed and direction, Sunjammer will use gimballed vanes (each of which is itself a small solar sail) located at the tips of each of its 4 booms, instead of thrusters, completely eliminating the need for any propellant other than the rays of the Sun.

In addition to being a demonstration craft, Sunjammer will collect scientific data in its own right. With several instruments to detect various aspects of space weather, Sunjammer may eventually become part of a larger network of solar sails studying the Sun, allowing for the creation of a more robust early-warning system for space weather.

Slated for launch in January 2015, a slight delay from an earlier projection of November 2014, aboard a Falcon 9 rocket, Sunjammer will launch along with the primary DSCOVR Earth observation and space weather satellite. Within two months of launch test various technologies, such as deployment, vector control via altitude vanes, and eventually reaching a location near the Earth-Sun L1 Lagrangian point. Sunjammer will carry two British space science payloads: the Solar Wind Analyser (SWAN) developed by the Mullard Space Science Laboratory of University College London, and the MAGIC magnetometer developed by the Blackett Laboratory of Imperial College London.>>

Ron-Astro Pharmacist wrote:
Is the mechanism for a HH object’s polar jet and accretion disc the same as the accretion disc and jets of active galactic nuclei?

• Presumably.

Ron-Astro Pharmacist wrote:
I am also curious if similar tests have been done in a zero G environment for rotating substances such that occurs as with water going down a drain here on Earth.

I guess what I am asking if there is known symmetry for these phenomena at different size scales?

neufer wrote:

Click to play embedded YouTube video.

Ron-Astro Pharmacist wrote:
Is the mechanism for a HH object’s polar jet and accretion disc the same as the accretion disc and jets of active galactic nuclei?

• Presumably.

Ron-Astro Pharmacist wrote:
I am also curious if similar tests have been done in a zero G environment for rotating substances such that occurs as with water going down a drain here on Earth.

I guess what I am asking if there is known symmetry for these phenomena at different size scales?

Water going down a drain here on Earth is powered by gravity.

An HH object’s polar plasma jets are powered by rapidly revolving polar magnetic helices.

I'm not sure what sort of zero G experiment might be particularly relevant here.

Roland wrote:I just noticed two additional beam trails. One splits off left at about 45 degrees just before the main beam leaves the immage. The other starts low center near the bright star forming and goes off 45 degrees to the right. It is a dark line with lighter edges. Perhaps it is older and fading.

Ron-Astro Pharmacist wrote:Just typing out loud.

nitpicker wrote:I do know that water does not spiral down the drain very easily near the equator, but that is another topic, methinks.

Beyond wrote:

nitpicker wrote:I do know that water does not spiral down the drain very easily near the equator, but that is another topic, methinks.

Wouldn't it also be another... tropic

geckzilla wrote:

BDanielMayfield wrote:So this stellar nursery is “about 1,500 LY away” but how much area is covered? I was wondering how long the jets are.

It's a narrow field of view. If you view the original size you can actually count the pixels and somewhat accurately determine how many arcseconds one thing or another is, because each pixel represents 0.13 arcseconds. That said, the jets actually extend beyond the picture frame. You'd also have to figure out what angle we are viewing them at. I find it impossible to tell if we are getting a near enough to edge-on view that it's negligible or not. If they're pointing somewhat toward us they could be a lot longer than they appear.

Nitpicker wrote:

Beyond wrote:

nitpicker wrote:
I do know that water does not spiral down the drain very easily near the equator, but that is another topic, methinks.

Wouldn't it also be another... tropic

Careful, your introduction of another tropic may make this topic entropic.

http://en.wikipedia.org/wiki/Coriolis_effect#Draining_in_bathtubs_and_toilets wrote:

Click to play embedded YouTube video.

<<Contrary to popular misconception, water rotation in home bathrooms under normal circumstances is not related to the Coriolis effect or to the rotation of the earth, and no consistent difference in rotation direction between toilets in the Northern and Southern Hemispheres can be observed. The formation of a vortex over the plug hole may be explained by the conservation of angular momentum: The radius of rotation decreases as water approaches the plug hole, so the rate of rotation increases, for the same reason that an ice skater's rate of spin increases as they pull their arms in. Any rotation around the plug hole that is initially present accelerates as water moves inward.

Only if the water is so still that the effective rotation rate of the earth is faster than that of the water relative to its container, and if externally applied torques (such as might be caused by flow over an uneven bottom surface) are small enough, the Coriolis effect may determine the direction of the vortex. Without such careful preparation, the Coriolis effect may be much smaller than various other influences on drain direction such as any residual rotation of the water and the geometry of the container. Despite this, the idea that toilets and bathtubs drain differently in the Northern and Southern Hemispheres has been popularized by several television programs and films, including "Escape Plan", Wedding Crashers, The Simpsons episode "Bart vs. Australia", and The X-Files episode "Die Hand Die Verletzt". Several science broadcasts and publications, including at least one college-level physics textbook, have also stated this.

In 1908, the Austrian physicist Ottokar Tumlirz described careful and effective experiments which demonstrated the effect of the rotation of the Earth on the outflow of water through a central aperture. The subject was later popularized in a famous article in the journal Nature, which described an experiment in which all other forces to the system were removed by filling a 6 ft tank with 300 U.S. gal of water and allowing it to settle for 24 hours (to allow any movement due to filling the tank to die away), in a room where the temperature had stabilized. The drain plug was then very slowly removed, and tiny pieces of floating wood were used to observe rotation. During the first 12 to 15 minutes, no rotation was observed. Then, a vortex appeared and consistently began to rotate in a counter-clockwise direction (the experiment was performed in Boston, Massachusetts, in the Northern Hemisphere). This was repeated and the results averaged to make sure the effect was real. The report noted that the vortex rotated, "about 30,000 times faster than the effective rotation of the earth in 42° North (the experiment's location)". This shows that the small initial rotation due to the earth is amplified by gravitational draining and conservation of angular momentum to become a rapid vortex and may be observed under carefully controlled laboratory conditions.>>

neufer wrote:

http://en.wikipedia.org/wiki/Coriolis_effect#Draining_in_bathtubs_and_toilets wrote:
<<Contrary to popular misconception, water rotation in home bathrooms under normal circumstances is not related to the Coriolis effect or to the rotation of the earth, and no consistent difference in rotation direction between toilets in the Northern and Southern Hemispheres can be observed. The formation of a vortex over the plug hole may be explained by the conservation of angular momentum: The radius of rotation decreases as water approaches the plug hole, so the rate of rotation increases, for the same reason that an ice skater's rate of spin increases as they pull their arms in. Any rotation around the plug hole that is initially present accelerates as water moves inward.

Only if the water is so still that the effective rotation rate of the earth is faster than that of the water relative to its container, and if externally applied torques (such as might be caused by flow over an uneven bottom surface) are small enough, the Coriolis effect may determine the direction of the vortex. Without such careful preparation, the Coriolis effect may be much smaller than various other influences on drain direction such as any residual rotation of the water and the geometry of the container. Despite this, the idea that toilets and bathtubs drain differently in the Northern and Southern Hemispheres has been popularized by several television programs and films, including "Escape Plan", Wedding Crashers, The Simpsons episode "Bart vs. Australia", and The X-Files episode "Die Hand Die Verletzt". Several science broadcasts and publications, including at least one college-level physics textbook, have also stated this.

In 1908, the Austrian physicist Ottokar Tumlirz described careful and effective experiments which demonstrated the effect of the rotation of the Earth on the outflow of water through a central aperture. The subject was later popularized in a famous article in the journal Nature, which described an experiment in which all other forces to the system were removed by filling a 6 ft tank with 300 U.S. gal of water and allowing it to settle for 24 hours (to allow any movement due to filling the tank to die away), in a room where the temperature had stabilized. The drain plug was then very slowly removed, and tiny pieces of floating wood were used to observe rotation. During the first 12 to 15 minutes, no rotation was observed. Then, a vortex appeared and consistently began to rotate in a counter-clockwise direction (the experiment was performed in Boston, Massachusetts, in the Northern Hemisphere). This was repeated and the results averaged to make sure the effect was real. The report noted that the vortex rotated, "about 30,000 times faster than the effective rotation of the earth in 42° North (the experiment's location)". This shows that the small initial rotation due to the earth is amplified by gravitational draining and conservation of angular momentum to become a rapid vortex and may be observed under carefully controlled laboratory conditions.>>

Nitpicker wrote:

neufer wrote:
http://en.wikipedia.org/wiki/Coriolis_e ... nd_toilets

That article is misleading, neufer. Obviously, there are ways to counteract the "natural" direction of the water spiral, or to stop it spiralling completely. Many sinks are too small to observe any spiral (without forcing one). And toilets in Australia typically have a lower water level than toilets of American design, so Australian toilets are much more turbulent and typically never spiral when flushed. But bathtubs are typically big enough to produce a spiral when draining, and statistically speaking, water draining from bathtubs in the Southern Hemisphere will have a slight tendency to spiral in the opposite direction, compared with the Northern Hemisphere. And again, statistically, bathtubs that are closer to the equator tend to take slightly longer to drain.

• Should we to believe the Australian or the Austrian

http://en.wikipedia.org/wiki/Ottokar_Tumlirz wrote:
<<Ottokar Tumlirz (17 January 1856, Weipert - 4 May 1928) was an Austrian physicist. He received his education at the University of Prague, obtaining his doctorate with a thesis on the expansion of sound and light waves (1879). At Prague he worked as an assistant to Ernst Mach (1838-1916) in the institute of experimental physics. After serving as a lecturer for several years in Prague, he relocated to the University of Vienna in 1890 as an assistant to Joseph Stefan (1835-1893). During the following year he was appointed associate professor of theoretical physics at the University of Czernowitz, where in 1894 he attained the title of "full professor". From 1905 to 1925 he served as a professor at the University of Innsbruck. Following his retirement, he was succeeded at Innsbruck by Arthur March (1891-1957). His scientific research largely dealt with the specifics of thermodynamics and electromagnetism.

In 1908 Tumlirz described careful and effective experiments which demonstrated the effect of the rotation of the Earth on the outflow of water through a central aperture, in a paper entitled "New physical evidence on the axis of rotation of the earth".>>

http://sites.apam.columbia.edu/courses/apph4200x/prl-bathtub-vortex-2003.pdf wrote:

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Anatomy of a Bathtub Vortex
Received 11 March 2003; published 5 September 2003

A. Andersen1,2,*, T. Bohr1, B. Stenum2, J. Juul Rasmussen2, and B. Lautrup3

1The Technical University of Denmark, Department of Physics, DK-2800 Kgs. Lyngby, Denmark

2Risø National Laboratory, Optics and Fluid Dynamics Department, DK-4000 Roskilde, Denmark

3The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark

Abstract: We present experiments and theory for the “bathtub vortex,” which forms when a fluid drains out of a rotating cylindrical container through a small drain hole. The fast down-flow is found to be confined to a narrow and rapidly rotating “drainpipe” from the free surface down to the drain hole. Surrounding this drainpipe is a region with slow upward flow generated by the Ekman layer at the bottom of the container. This flow structure leads us to a theoretical model similar to one obtained earlier by Lundgren [J. Fluid Mech. 155, 381 (1985)], but here including surface tension and Ekman upwelling, comparing favorably with our measurements. At the tip of the needlelike surface depression, we observe a bubble-forming instability at high rotation rates.>>

Nitpicker wrote:

geckzilla wrote:

BDanielMayfield wrote:So this stellar nursery is “about 1,500 LY away” but how much area is covered? I was wondering how long the jets are.

It's a narrow field of view. If you view the original size you can actually count the pixels and somewhat accurately determine how many arcseconds one thing or another is, because each pixel represents 0.13 arcseconds. That said, the jets actually extend beyond the picture frame. You'd also have to figure out what angle we are viewing them at. I find it impossible to tell if we are getting a near enough to edge-on view that it's negligible or not. If they're pointing somewhat toward us they could be a lot longer than they appear.

Based on a scale of 0.13 arcsec/pixel, I figure the full resolution image height of 1327 pixels spans ~2.88 arcmin (roughly 4 Jupiters). At a distance of 1500 light years, this represents ~1.25 light years, top to bottom, or in other words, each pixel represents about the orbital diameter of Neptune.

Nitpicker wrote:You may believe both, one, or neither.

Chris Peterson wrote: As predicted by theory, and verified by experiment, the Coriolis "force" is nowhere near strong enough to create a preferential vortex direction in different hemispheres in toilets, sinks, bathtubs, or swimming pools.