Question 1: How many prohibited areas are there in the US?
It’s answer number 3. There are only nine parcels of prohibited airspace in the entire US—three of which are in the Washington DC area (which is not surprising). These are P-40 (Camp David); P-56 (A and B); and P-73 (Mount Vernon). The others are P-47 in Amarillo Texas; P-67 in Kennebunkport Maine; P-204, P-205, & P-206 in northern Minnesota; and the newest one, P-49 (effective May 17, 2001), over the Crawford, Texas residence of President Bush.
Question 2: True or false: It is possible for a parachutist in free-fall to achieve a great enough velocity to break the sound barrier.
TRUE. However, you would need a helium balloon, and you would have to get a mile or two above 100,000 feet. The air is thin enough up there so that terminal velocity would actually be greater than Mach 1. (Also helpful is that the speed of sound becomes about 100 mph lower in the thinner air.) By the time such a human projectile reached around 85,000 feet, he (or in the case of Cheryl Stearns, she) would for a few seconds more, be traveling in excess of Mach 1. (For a full story, see High Hopes — and the Headlong Plunge)
Question 3: What is the highest cloud type?
- meteoric vapor trails
- noctilucent clouds
Answer: 4; Noctilucent clouds– they are typically found at altitudes of around 50 miles. They are usually only visible in high northern latitudes at twilight. (The next highest up are nacreous clouds.) This has been presented on a web site, actually: The Highest Clouds) There was a great article about it in an old Scientific American (real old; like June 1963).