CHEGR 2683 Chemical Engineering Principles 1 Program Website: http://www.eng.ysu.edu/~dprice/dpricehome.html

Spring 2006 Results for SI

GPA 10+ = Students who attended 10 or more study sessions

Previous Project

Chapter 2

•Units of Measurement •Force/Weight

Sep 30 1999 9:23PM

Mix-up doomed spacecraft Mars orbiter lost in miscommunication By MARK CARREAU Copyright 1999 Houston Chronicle

An embarrassing mix-up with its aerospace contractor over the use of English and metric units of measurement led to the navigational errors that caused last week's loss of the $125 million Mars Climate Orbiter, NASA said Thursday. The probe destructed early Sept. 23 as it was maneuvering into orbit around Mars after a near 10-month journey from Earth. Errors that crept into maneuvering commands sent from Earth based on discrepancies from the two systems of measurement allowed the spacecraft to sweep within 37 miles of the Martian surface rather the intended 93 miles. The probe broke apart or overheated in the atmosphere as a result of the failure to convert the units of measurement. The errors were repeated throughout four major maneuvers and other smaller steerings during the Climate Orbiter's journey, which began with a Dec. 11, 1998, liftoff from Cape Canaveral, Fla. Previously, NASA had believed a one-time error in the last of the major maneuvers, Sept. 15, was responsible for the loss. With Thursday's disclosure, the space agency embraced responsibility for the mistake, rather than haggle over sharing blame with Lockheed Martin Astronautics, the Denver-based aerospace company that builds its Mars probes and furnishes

Quote from H. Klesch, B.E ChE 2004 August Mack Environmental

Lastly, for all the young kids who hate converting, it's amazing how much converting you really do in a job. Everyday I am converting from English to metric and vice versa, or the boss will ask what equivalent units there are for something and what it means or given a number, put it in a way we can understand. Most of the time though we have to report in certain units only and all the information is in units long from the one you want.

Quote from D. Oaks Former YSU ChE Sophomore

I will be going to OSU in the fall and they said I have the knowledge of a junior. They were impressed with the fact of CHEMCAD being introduced so early and knowing Excel. They only use Excel for printing imported things.

Common Units in Engineering

Rest of the World • kg or metric tonne • m • m 3 or liter • N • J or kW-hour • W • Pa or kPa or bar United States • lb m • ft or ton (short/long) • ft 3 or gallon or barrel • lb f • Btu or hp-hour • hp • atm or psi or in. Hg or mm Hg or torr

Common Errors

• Metric tonne or American Engineering ton • Fluid ounce or mass ounce • lb m or lb f • American Engineering gallon or Imperial gallon • Barrels: – 1 Barrel US liquid = 31.5 gallons – 1 Barrel US oil = 42 gallons

Engineering Calculations must Always be Correct with Respect to Units of Measurement

1

ft

3 

7.4805

gallon

1



7.4805

gallon ft

3

1



ft

3

7.4805

gallon

Convert 1 Imperial gallon into ft 3 1

Imp gallon

1

m

3 220.83

Imp gallon

35.3145

ft

3

m

3  0.1599

ft

3

3

Convert 100 m /day to gallon per minute (gpm)

100

m

3

day

1

day

24

hours

1

hour

60

min

264.17

gal m

3  18.345

gpm

Force and Weight

• Force = Mass x Acceleration – Newton, lb f • Weight = Mass x Acceleration of gravity – Newton, lb f • 1 Newton = 1 kg accelerating at 1 m/s 2 • 1 lb f = 1 lb m accelerating at 32.174 ft/s 2

Weight of 10 kg on Earth

F

 10

g



F



ma

 10

kg kg

2 205

kg lb

2

m / s , m ft / s

2

s

2

s

2

ft m

1

N

1

lb f s

2

kg m s

2 

N

32 174

lb ft m

 22 05

lb f

Weight of 10 lb m on Earth

F



ma

 10

lb m s

2

ft

1

lb f s

2 32 174

lb ft m

 10

lb f