LaACES High Altitude Ballooning

Atmospheric Density By: Henry Hardee

Sina Zarei

Ian Walsdorf

• To determine the density of the atmosphere throughout the flight using the P and T that we find assuming air is an ideal gas.

• To better understand the effects that freezing temperatures and low pressures can have on equipment through the atmosphere.

• To learn about circuits and electronics and attempt a hands on experiment.

Atmospheric pressure reduces with altitude:

-Due to gravity

-The gravitational attraction between the earth and air molecules is greater for those molecules nearer to earth than those further away

-Molecules further away from the earth have less weight but they are also 'standing' on the molecules below them, causing compression

http://www.npl.co.uk/pressure/faqs/atmosaltitude.html

Simple density formula

Boyle’s LawR - is the universal gas constant

- we used 0.000082057 m^3/atm*K

m - is the molar mass (in our we use air) kg

P – pressure atm

T – temperature K

ρ – density kg/m^3

ρ (rho) - is the density of the substance, measured in kg m^3

m - is the mass of the substance, measured in kg

V - is the volume of the substance, measured in m^3

• We are using the DS1621+ND temperature sensor.

• We are using the same pressure sensor that was used on the HASP project last summer. We did this for a few reasons the main one being that we are familiar with the part already.

• BASE -25°C SPAN -110°C• Part # 442-1026-ND

Connections

height (km) height (ft) Temp. (K) Pressure (mb) Pressure (atm) Density (kg/m 3̂)1 3280.8399 290 1000 0.986923267 1.2027289162 6561.6798 282 900 0.88823094 1.1131639973 9842.5197 274 800 0.789538614 1.018369014 13123.3596 268 700 0.690846287 0.9110222765 16404.1995 260 600 0.59215396 0.8049031986 19685.0394 252 500 0.493461634 0.69204647 22965.8793 244 450 0.44411547 0.6432628028 26246.7192 236 400 0.394769307 0.591171849 29527.5591 228 350 0.345423143 0.535425373

10 32808.399 220 300 0.29607698 0.47562461711 36089.2389 214 250 0.246730817 0.40746657212 39370.0788 214 200 0.197384653 0.32597325813 42650.9187 214 180 0.177646188 0.29337593214 45931.7586 214 160 0.157907723 0.26077860615 49212.5985 214 140 0.138169257 0.2281812816 52493.4384 214 120 0.118430792 0.19558395517 55774.2783 214 100 0.098692327 0.16298662918 59055.1182 214 85 0.083888478 0.13853863519 62335.9581 214 65 0.064150012 0.10594130920 65616.798 214 50 0.049346163 0.08149331421 68897.6379 215 46 0.04539847 0.07462513422 72178.4778 216 42 0.041450777 0.06782054723 75459.3177 217 38 0.037503084 0.06107867624 78740.1576 218 35 0.034542314 0.05599861725 82020.9975 219 32 0.031581545 0.05096495126 85301.8374 220 28 0.027633851 0.04439163127 88582.6773 222 23 0.022699235 0.03613604428 91863.5172 223 20 0.019738465 0.03128173929 95144.3571 224 16 0.015790772 0.0249136730 98425.197 225 13 0.012830002 0.02015239131 101706.0369 228 10 0.009869233 0.015297868

gas constant 8.21E-05molar mass of air 29

Expected Values of Results

0

20000

40000

60000

80000

100000

120000

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Density (kg/m^3)

Alt

itu

de

(ft)

Mechanical Design

• We choose to do a double box design instead of using the pink insulation foam we used thin foam board because rigidity and thermal characteristics.

• We used pink insulation and fiberglass insulation between the two boxes to further prevent heat escaping.

• We mounted our temperature sensor outside our inner box and exposed it to the atmosphere to get accurate readings.

• This design has so far been successful.

AUTOCAD DRAWINGS

INNER BOX

AUTOCAD DRAWINGS

BIG BOX

Weight Budget of the Pay Load:

Weight limit: 500 g

• Balloon Sat W/ Sensors & Wires: ~82.40 g• One 9 v Battery: ~46.6.0 g

~126.5g

+

500 g - 329.9 g = 170.1g

• Outer Box

~74.4g• Inner Box

Pressure Test

• Upon calibrating our pressure sensor we found to be a bias error of 2.05 psi. This is due to the fact that due to time constraints we were not able to reference our sensor to a 4 volt source so instead we referenced it to a 5 volt source.

• We put our payload in a pressure chamber and it showed a linear output.

Temperature Test

• We tested our payload by putting the box in an ice chest with dry ice for an hour.

• All of our components were fine when we pulled it out and our data sheet was correct

Impact Test

• The payload was dropped from a height of 10 feet to simulate the force felt upon landing this is because the nominal descent rate is approx. 20 feet/sec.

• We did this test 3 times and nothing was damaged in the process

Acknowledgements

• CSBF• Dr. Guo• Dr. Guzik• Dr. Wefel• Mr. Giammanco• Mr. Ellison• Jeff Kornuta• NASA