PowerPoint Presentation

Gravity Team Total ResistanceJeff WeinellJason MuellerBrittany Dupre

OverviewMission GoalScience ObjectivesTechnical ObjectivesScience BackgroundConclusionReferencesQuestionsMission GoalWe will build a payload to measure Earths gravity field as a function of altitude for heights of up to 100,000 feet, and compare our findings to theoretical and experimental high altitude gravity models.

Science ObjectivesAnalyze and interpret data to find a correlation between changes in Earths gravity as altitude increases.Compare our data to theoretical models. Compare our data to results from previous experiments.

Technical ObjectivesMeet the design specifications provided by LAACES.

Science Background Overview Isaac Newton and his second law of motionGravimeters (absolute and relative)Past and present gravimetry missionsAtmospheric conditions

Isaac NewtonTheorized that an external force was pulling objects towards Earths centerHis second law statesthat the net force on an object is equal to the instantaneous rate of change of that object

Theoretical Gravity ChangeFrom Newtons second law, we can derive the theoretical change in gravity with altitude

Absolute GravimetersA gravimeter is an instrument that measures gravityAccurate for up to about 1.1 microgal

Expensive Hard to transport Takes a long time for accurate measurements

Relative GravimetersInvented by Lucien LaCosteZero-length springPrevious experiments have used a variety of relative gravimeter types: GWR T020GRACEGeosatDUCKY Ia

Lucien LaCosteTwentieth century physicist and metrologistCo-invented the modern gravimeter with Arnold RombergInvented the zero-length spring in 1932

Zero-length SpringsExert zero force if at zero lengthTwisted and coiled springs create tensionCan make pendulums with infinite period

GWR T020More accurate than zero-length springsInvolves levitating a super-conducting sphere in a stable magnetic field

GRACEGravity Recovery And Climate ExperimentMaps Earths gravity field every 30 daysHelps track sea levels, ocean currents, polar ice sheets, and Earths interior structure

GeosatUsed radio altimetry to detect momentary altitude deviations from average orbitAltitude decreases with local gravity increase Altitude increases with localized gravity decrease

DUCKY IaA high altitude balloon payload that measured relative gravity changes Used a Vibrating String Accelerometer (VSA)

Vibrating String Accelerometer

The VSA on the DUCKY Ia payload detected changes in acceleration along a single axis

The difference between the oscillation frequencies of the two strings is proportional to the acceleration along the sensitive axisMeasuring Gravity in a Dynamic Environment

Gravimeters cannot distinguish between gravitational acceleration and acceleration due to external forces

It is necessary to obtain additional acceleration measurements from an inertial reference frame independent of the gravimeter to isolate gravitational accelerationEotvos EffectObjects travelling east appear to experience a decrease in gravitational accelerationObjects travelling west appear to experience an increase in gravitational accelerationVertical component of centrifugal pseudo-force

Atmospheric Conditions from Zero to 100,000 feetTemperature Decreases with altitude in the troposphereIncreases with altitude in the stratospherePressureDecreases as altitude increasesHumidity Approximately 65% in Palestine, TexasWeather dependentTurbulence Greatest in the troposphere

ConclusionTemperature, pressure, humidity, and turbulence will vary during balloon flightWe anticipate that gravity measurements will be most accurate in the stratosphereGravity should decrease slightly with increasing altitude

Referenceshttp://www.globalsecurity.org/space/systems/images/global_topo.jpghttp://www.cosmosmagazine.com/features/online/1678/gravity-ballhttp://www2.mssu.edu/seg-vm/bio_lucien_lacoste.htmlhttp://www.currentresults.com/Weather/Texas/humidity-annual.phphttp://www.ualberta.ca/~dumberry/gravity.htmhttp://www.britannica.com/EBchecked/topic/242391/gravimeterhttp://www.gwrinstruments.com/pdf/Geothermal_Brochure_Prod_Rev1_4PG.pdfhttp://www.cage.curtin.edu.au/~will/grav_anoms.htmhttp://www-scf.usc.edu/~kallos/gravity.htmhttp://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA202985&Location=U2&doc=GetTRDoc.pdfhttp://www.jclahr.com/science/psn/zero/winding/gravity_sensor.htmlhttp://www.merriam-webster.com/dictionary/free%20oscillation

References (continued)http://www.microglacoste.com/fg5Principle.phphttp://www.jpl.nasa.gov/news/press_kits/gracelaunch.pdfhttp://ibis.grdl.noaa.gov/SAT/gdrs/geosat_handbook/docs/chap_1.htmhttp://www.srh.noaa.gov/jetstream/atmos/layers.htmhttp://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/michel.htmlhttp://www.splung.com/content/sid/2/page/newtons_lawshttp://www.nasa.gov/audience/foreducators/k-4/features/F_Measuring_Gravity_With_Grace.htmlhttp://www.cleonis.nl/physics/phys256/eotvos.phphttp://www.leakandflowtesters.com/pressure_decay.htmhttp://observatory.ou.edu/Oct3-11.htmlhttp://www.centennialofflight.gov/essay/Theories_of_Flight/atmosphere/TH1G3.htmhttp://ethesis.helsinki.fi/julkaisut/mat/fysik/vk/virtanen/studieso.pdfhttp://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.htmlhttp://hep.physics.indiana.edu/~rickv/Standing_Waves_on_String.htmlhttp://laspace.lsu.edu/aces/BalloonCourse/Introduction/Intro%201%20-%20Overview%20of%20LA%20ACES.ppt

Questions?