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September 29, 2021 Archives

Wednesday, September 29, 2021

TRACKING WITH CLOSEUPS: Now, that's a .22

The .22 Eargesplitten Loudenboomer cartridge was developed by P. O. Ackley for Guns & Ammo magazine. Its sole goal was to produce a muzzle velocity of at least 5000 feet per second (fps) or around 1524 metres/second, in excess of Mach 4.2. The cartridge was created by necking down a .378 Weatherby Magnum case to accept a 3 gram .224" (5.56 mm) bullet.

In ballistic testing, the round never achieved the target muzzle velocity, topping out at 4600 fps (1500 m/sec) and a muzzle energy of 3,185 joules, which is almost twice that of the 5.56×45 NATO cartridge used by the AR-15, M-4, and similar rifles, which fires a bullet of comparable size and mass.

It is not clear what would have happened to the bullet immediately after leaving the barrel. At Mach 4, heating and aerodynamic forces would have been extreme, and it's possible a lead bullet might have melted shortly after exiting the muzzle and been dispersed into a cloud of droplets. In any case, with such a light bullet and supersonic drag forces,, the projectile would rapidly lose velocity and energy. But this was intended to set a record, not be practical for anything.

Posted at 15:23 Permalink

THE HAPPENING WORLD: Double-Charm Tetraquark

Here are the research papers announcing and describing this discovery:

Posted at 13:52 Permalink

CONTINUITY: From 1959—“The Art of Gold Beating”: Making Gold Leaf

The thickness of gold leaf is around 100 nanometres, which is the wavelength of near infrared light and only around 2000 gold atoms thick. If you hold a sheet of gold leaf up to a bright light, you'll see light transmitted through it, with a shade of green-blue. I used to think this was an interference effect due to the thickness of the leaf, but it's simply a result of gold reflecting predominately red and green light, giving it its characteristic mellow glow (thanks to special relativity), with the unabsorbed blue and green wavelengths passing through the thin sheet.

Posted at 11:56 Permalink

CONTEXT: Soyuz MS-18 Repositioned to Nauka Module on International Space Station

Yesterday, 2021-09-28, the Soyuz MS-18 spacecraft was undocked from the Rassvet module on the Russian segment of the International Space Station and flown around to the other side of the station where it was docked to a port on the new Nauka module, the first time that port was used. This frees the Rassvet port for the docking of Soyuz MS-19, scheduled to launch on October 5th. Since the Nauka port had not been previously used, the repositioning allowed it to be tested before both ports were required by the arrival of the new Soyuz. Even for such a brief maneuver, the Soyuz crew prepares as if for a return to Earth, as failure to re-dock, for whatever reason, would require they de-orbit and land in Kazakhstan.

This is a time lapse of the repositioning.

And here is the complete operation as it occurred (one hour and 14 minute video).

Posted at 11:24 Permalink