Nuts and Volts - September 2008

To get both lines to appear together on the chart, I just plotted the relative change.

Second, even though the balloon burst occurs in a near vacuum, the parachute opens fully within two seconds. The image strip in Figure 12 is a series of stills from a video recorded at 98,000 feet. The images show that indeed the parachute does fully open within two seconds of the balloon burst.

Let’s assume the near spacecraft behaves as if it’s in free fall with no significant drag for the first two seconds after balloon burst. At the

point of burst, the near spacecraft is ascending at a speed of 1,000 fpm, or 17 fps. According to the equations of motion for a mass under uniform velocity and acceleration (d = vt + ½at²), the near spacecraft will fall, 17t + (1/2)(- 32)t², or 17*2 + (1/2)* (- 32)* 22, 34-64, or 30 feet from burst altitude.

The equation for speed is v – at, and this indicates the near spacecraft is falling 17 – 32*2, 17-64, or 47 fps by the time the parachute finally opens. This is equal to a descent speed of 32 mph. In high altitude balloon bursts, the near spacecraft

NEAR SPACE

falls at a speed between 70 and 100 miles per hour. Therefore, it appears a parachute doesn’t do much initially, other than keep the near spacecraft from flipping over and tangling.

Onwards and Upwards,

Your near space guide NV

USEFUL WEBSITES Additional information about parachutes can be found at these websites.

www.aero.com

http://inventors.about.com

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