Scientific Ballooning• Brief history• Electrodynamics over thunderstorms• Balloon types• How a balloon works

Lift (forces)

HistoryFirst hot air balloon – French brothers – 500ft. for about 5 miles in 1783War time usage Many ‘Firsts’ – 1st to cross English Channel - 1785– 1st to cross Atlantic – Double Eagle II - 1978– and Pacific – Double Eagle V - 1981– 1st non-stop around the world – Bertrand Piccard

from Switzerland and Brian Jones from Great Britain in 1999

(http://www.cameronballoons.co.uk/news/pr/rtw/news2.htm)

Other Records• 1960 -- Altitude Record and Highest Parachute Jump: Air

Force Captain Joe Kittinger jumps from a balloon at 102,800 feet on August 16th and sets a world high altitude parachute jump (where he breaks the sound barrier with his body) and freefall record that still stands today.

• 1961 -- Current Official Altitude Record Set: Commander Malcolm Ross and Lieutenant Commander Victor A. Prather of the U.S. Navy ascend to 113,739.9 feet in 'Lee Lewis Memorial,' a polyethylene balloon. They land in the Gulf of Mexico where, with his pressure suit filling with water, and unable to stay afloat, Prather drowns.

• 1988 -- Hot Air High Altitude Record: Per Lindstrand sets a solo world record of 65,000 feet for the greatest height ever reached by a hot air balloon.

• 1995 -- First Solo Transpacific Balloon Flight: February 14-17, Steve Fossett, another around-the-world contender with his Solo Challenger project, launches from Seoul, Korea and flies 4 long days to Mendham, Saskatchawan

• Want More? See http://www.pbs.org/wgbh/nova/balloon/science/history.html

My Experiments:Stratospheric Electrodynamics

over Thunderstorms• Sprites and Lightning• Measure electric field, magnetic field, X-

rays• Balloons in the stratosphere 10 to 15 hour

flights with zero pressure balloons• Coordinated ground-based measurements• (more next lecture)

Sprite scenario

balloon

• Sprite movie

Balloon types• zero pressure, super pressure, weather,

blimp, tethered, cylinder, hot air, party

TetheredAerostat(blimp)NASA semi-trailer

air bladder

He

Hot Air Balloons

• Montgolfier - rigid tissue paper over frame

• Modern types are numerous – nylon, etc

• burners up to 15,000BTU or more

people

ZeroPressure Balloons

• Highest and lightest• Open at the bottom• no pressure difference

across flanks

Sprite BalloonTest flightMay 2002Tillamook, ORBob, Jeremy

Michael

Duct to vent Helium

payload

When balloongets to float altitudeHe has fully expandedand starts venting.Balloon stays at thataltitude

Zero Pressure Balloon

no pressure difference across bottom and sides of balloon(only around the very top)

Super Pressure Balloon• Longest Duration• Sealed Bag• Heavier (double

layered – will not pop like rubber balloon)

Spherical

Superpressure balloon flights1992/3

Launchedfrom New Zealand

Record flightslongest > 4 months

Forces on a Balloon

• Gravity (on the balloon and the gas)• Pressure over the whole surface

Buoyancy – You get ‘lift’ if the weight of helium+balloon is less than the weight of the air displacedSo, how much does air weigh?

First lets talk about Density and pressure

• Density is the technical term for how much mass is in a volume.

• The more mass in a given volume, the higher the density

• density ρ = m/V= mass/volume• Helium is less dense than air because each

atom has less mass than atoms of Nitrogen and Oxygen

Atmospheric Pressure

• Think about an ocean of air above us pressing down

• Air pressure at sea level is 15 pounds/square inch. In other words, a column of air one inch square weighs about 15 pounds

• A 1 square meter column of air weighs 39x39x15 pounds or nearly 23,000 pounds

Lift• Replace a volume of air with something that

weighs less than that volume of air, BUT TAKES UP THE SAME VOLUME, and it will float

• Density of He is much less than the density of air• Same number of atoms but each atom of He is

lighter • Upward Force = Lift = L • Lift on the balloon is

L= (weight of air displaced) –(weight of balloon+He+payload)