EOSS Handbook Chapter 3

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  • 3.1. Ascent rate
  • 3.2. Temperature
  • 3.3. Pressure
  • 3.4. Moisture
  • 3.5. Electromagnetic fields
  • 3.6. View from 100,000 feet
  • 3.6.1. How high is 100,000 feet?
  • 3.6.2. Comparisons
  • Miles
  • Paper clips
  • Pop cans
  • People
  • 3.6.3. Earth's radius
  • 3.6.4. Conclusion
  • 3.7. Descent
  • 3.8. Impact

<<Mike Manes>> Any experimental payload should be able to withstand the flight environment to include:

3.1. Ascent rate

800 - 1200 feet per minute (approximately constant at any altitude)

3.2. Temperature

External air temperatures from +40 to -60 degrees Centigrade

3.3. Pressure

At 100,000 feet, ambient pressure is approximately 0.15 psi absolute (about 1/100th atmosphere) or 5 mbar

3.4. Moisture

EOSS balloons have passed through cloud cover, virga (wisps of precipitation evaporating before reaching the ground), and there is a theory about one flight traveling through a cold front causing condensation to foul electronic components. Moisture droplets from the above should be expected during a flight.

3.5. Electromagnetic fields

Strong EM fields at 144 and 425 MHz from the Shuttle transmitter antennas must also be tolerated.

3.6. View from 100,000 feet

<<Andy Kellett>> EOSS launches balloons to see how things are "up there". So it makes sense to have a feel for how high "up there" is. If a balloon were left to itself, with no gas escaping from it, it would go up until it popped. Rather than let the balloon pop and tangle with the payload, EOSS cuts the balloon away from the payload. We want the balloon to get as high as possible, yet we don't want the balloon to pop on its own. So when do we cut the payload and balloon apart? It turns out that for the size and type of balloon EOSS uses and for the weight of the EOSS payload, about 100,000 feet above sea level is the right height to separate.

3.6.1. How high is 100,000 feet?

You can start to get a feel for how high 100,000 feet is by remembering that commercial jets travel at about 30,000 feet. 100,000 feet is about 2/3 of the way through the stratosphere, and the majority of the mass of the earth's atmosphere is below the balloon at that height. You can tell that there are fewer gas molecules at 100,000 feet when you see video from the balloon. The sky is as black as night, but the sun is still visible.

3.6.2. Comparisons

One way to get a better feel for what 100,000 feet is, is to convert that height into different measurement units: Miles

If 100,000 ft is the same as 18.9 miles, we now know that if we walk (at about 3 miles per hour) it will take about 6.3 hours to get 100,000 ft. If you drive (at 55 miles per hour) you could get 18.9 miles in about 20 minutes and 38 seconds. Paper clips

So, is 100,000 ft. far away? If you made a chain of paper clips 100,000 feet long, (each paper clip weighs about 0.5 gram and it takes 10 paper clips to make a one foot chain), the chain would weigh 500 kg (about 1100 lbs). Pop cans

If you stacked pop cans 100,000 ft high, it would take about 259,500 pop cans (each pop can is 4 -5/8 inches high when you subtract out the part of the can that fits inside the can below it). That's about 10,800 cases of pop. People

It would take 16,667 six foot people, standing head to foot to reach 100,000 feet, (even more if they stand on each other's shoulders). So in terms of paper clips, pop cans and human height, 100,000 feet is far away.

3.6.3. Earth's radius

100,000 feet is only 0.48 percent of the earth's average radius. This means if you draw a circle to represent the earth, like Figure 1.


Figure 1
This series of figures do not translate to low resolution GIF files. They are included in the PDF file available by link from the Handbook Main Page. I suggest any educators logging in take this opportunity to demonstrate some ratio equations and math to draw these figures for themselves.

3959 Miles Earth's Radius


and then draw a dot to represent an EOSS balloon at 100,000 feet, it would NOT look like Figure 2.

Figure 2

Instead, it would be a dot like that in Figure 3.

Figure 3

In fact, with the circle we've drawn, it is hard to position a dot to show how 100,000 feet relates to the earth's size. If you draw a much larger circle (so large only a small part of it fits on this page) you can accurately draw a dot to represent 100,000 feet (Figure 4).

Figure 4

So, you can see that in terms of the earth's size, 100,000 feet is hardly a bump.

3.6.4. Conclusion

With the majority of the earth's atmosphere behind it, an EOSS balloon at 100,000 feet truly is at the edge of space. The environment at that altitude can hardly be compared with anything we experience on the surface of Earth. Yet all of us live less than twenty miles from this vastly different place.

3.7. Descent

Descent rate up to 2000 fpm and infiltration of 100% relative humidity air during descent.

3.8. Impact

The payload must stand the rigors of a landing at the above descent rate coupled with a parachute drag for at least 500 m across a plowed field.

Go to Chapter 4 (part a)