The blog Fuck Yeah Fluid Dynamics posted some stills from this video recently. The images were fantastic, but I didn't totally understand what I was seeing. Thankfully, FYFD blogger (and aerospace engineering Ph.D. student) Nicole Sharp was kind enough to answer my questions.
What you're looking at is a rocket engine. The video shows what happens to airflow in the engine as it goes from subsonic to supersonic. In the video and the pictures, you can see a dark red line moving down the tunnel. That's the edge of the shockwave that marks the boundary between subsonic air and Mach 1. You should also pay attention to the little black vortices that whirl away from the edge of the engine wall. Those are pretty important.
[I]n recent years, the affordability of airships as well as developments in high-definition cameras, high-powered sensors and other unmanned technologies have turned these oddball aircraft from curiosities of a bygone era to must-have items for today's military. And airships increasingly are being used for civilian purposes.
The federal government is buying blimps, zeppelins and spy balloons, and many of these new-generation hybrid "lighter than air" aircraft are taking shape across California.
"So much is going on with airships in California now," Pasternak said. "It wasn't this way 10 years ago."
Of note, the difference between airships, blimps, and zeppelins:
Left to right: Neil Armstrong, Michael Collins, and Buzz Aldrin, the crew of Apollo 11. Photo: NASA.
On this day in 1969, humans walked on the moon for the first time. The Apollo 11 spaceflight brought Americans Neil Armstrong and Buzz Aldrin to the lunar surface on July 20, 1969, at 20:18 UTC.
Michael Collins, the mission's third member, remained in lunar orbit. All three men returned safely to Earth after an 8-day mission that began with a Saturn V rocket launch from Kennedy Space Center in Merritt Island, Florida on July 16.
This was the fifth manned mission of NASA's Apollo program, which ran from 1963 to 1972 and included 6 missions that landed on the moon. These were the first and last times human beings set foot on another world.
James Oberg at IEEE Spectrum has been following the "disaster-ridden" Russian missile program that lead to last month's spectacular spiral lights display over Norway. He offers some insight into the fascinating political story going on behind the scenes.
Designed to be the next-generation submarine-launched intercontinental ballistic missile (ICBM), Bulava has had 11 test flights since 2005--and has failed most of them, including the last three in a row. ... Beyond the threat to Russia's nuclear deterrent, the problems with the missile have become a major scandal for the Putin/Medvedev government. Hard-line Communist Party critics accuse them of letting the entire Russian military industrial complex decay to the point of danger.