BalloonLife,March 2000

12

One of the mainchallenges inlong dis-
tance ballooning is to keep from runnin g
outo ffuel—propane,helium,ballast,
etc.Overthepastseveraldecadesbal-
looninghasmadegreatadvancesinex-
tending the rangeof lighter-than-air flight.
Last year the Breitling Orbiter 3made it
aroun d the globe and then some.
BertrandPiccardandBrianJones,
mission accomplished, landed with three
gallons of propane left. While they could
have flo wn through th e day, it is doubtful
theballoonwould h ave made it throug h
anothernight.Iftheyhadbeenflyinga
sup erp ress ureball oon ,in steadofa
Roziere style, how longcouldthey h ave
stayed aloft? How many times might they
havefl ownaro un dthewo rldina
superpressure balloon?
Never heardof a superpressure bal-
loon? Also known as constant pressure or
positivepressure,there h avebeenvery
few manned superpressure balloons, built
andonlythreepeoplealivetodayhave
pilotedon e.Thesuperpressureballoo n
differsfromaconven tional“zeropres-
sure”balloonbymaintaininga constant
volume.
Intheoryiftheballoondisplacesa
constant volume within its gas cell it will
maintainaconstantaltitude.Byusing
ballast to “trim” the desired b uoyancy the
balloonwillcontin ue toflyatthatalti-
tude.Theen velopemustbenonelastic.
Toovercomethediurnalcycle, thesur-
face finishhas tomaintain thetempera-
ture of thehelium gassothatitwillnot
heatupexcessivelyduringthedaynor
cool down at nig ht. Withou t such features
theinternalpressureswouldbeimpos-
sibletocontainduringthedayandthe
balloon would shrivel upatnight.
Haveyouever seen acartoonchar-
acter holding ontoa balloonastheyrise
everhigherintotheair,andthenthe
balloon finally pops? Then yo u have seen

thenumber oneriskconfrontingsuper-
pressureballooning—howtokeepthe
bubble frombursting.
Gasballo onsusedtoday, includin g
Rozieres, hav ean opening that allows the
gas within the envelope to escape. Rising
intoth e atmosphere, the gas, usuallyhe-
lium, expands. The fabric of the envelope
changesshape andexpands as the exter-
nalp ressuredecreases.Eventuallythe
balloon rises beyond a point th at the fab-
riccan expand and gas is expelled through
theopening.Whenthatdoesn’thappen
the gas cell tears. Thisis what happened
toJ. ReneéandGlobal Hiltonin1998.
Theinflationtubesbecamechokedoff
andcouldnotexpel the gasandthe bal-
looncellsruptured.Traditionalnetted
balloons have been knownto bu rst when
thepilotforgottountietheapexatthe

bottomof the envelope. As a safetyfea-
turegasballoonshave theenvelopeat-
tached at the equator sothat the deflated
envelop e actsasa parachute.
Superpressureballoonshavebeen
usedforalongtimeinhighaltitude
researchp rojects. The Frenchhavehad
superpressureballoonsflyformonths
and makemultipletrips arou nd theworld.
Thefirstuseofsuperpressurefor
manned flight was Thomas Gatch’s failed
Atlanticattemptin1 974.Heandhis
balloonLight Heartdisappeared without
trace. His attempt was also the first to use
th e“jetst ream.”Th eclu st erof
superpressureballoonswasmad eb y
RavenIndustries.
The nextyear Malcolm Forbesan d
Tom Heinsheimeralso attempted to make
anAtlanticattemptusingaclusterof

FlyingUnderPressure

Superpressure balloons are best for flying at one
altitude for a very long time.

by Tom Hamilton

ATMOSAT Americabeing prepared for flight in Gaviota, California.

IMAGE pressure000301.gif
IMAGE pressure000302.gif

BalloonLife,March 2000

14

superpressure helium balloons. Theirplan
was to start on the west coast “testing” the
system as they crossed the North Ameri-
can continent inWindborne. Strong winds
atlaunchstarteddraggingthesystem
along the groundbefore th ey were read y
tofly. A quickactin gcrew member cut
away the helium balloons, sav ing Forbes’
andHeinsheimer’s lives.
“Forbes andI foolishly trieda simi-
lar kind of folly, cluster o f superpressure
balloons,”relates Tom Heinsheimer.“We
wereusingtransparentmylarballoons.
Since these can only take a certain amount
of stress, we needed a cluster of ballo ons
to carry a reasonab le payload to fly across
the Atlantic.”
Heinsheimer stilledb elievedinthe
superpressure theory, but lost any faith in
acluster balloon system. He immediately
began work on asingle cell superpressure
envelope.With Forbes no longer involved
in Heinsheimer’s idea, he needed a fund-
ingsource.
“I worked for the Aerospace Corpo-
rationandwaschairmanoftheSouth
Coast Air QualityManag ementDistrict.
It was sort of a natural connection . Aero-
spacefundedthedevelopmentofthe
ATMOSAT(Atmo sph eri cSatellite)
America. WorkingwiththeAir Quality
DistrictandEPA itwasa natural touse
the superpressure balloon for smog test-
ing. The superpressure was the only real
markerthatwen talongwiththeatmo-
sphere. You couldn’t use a hot air balloo n
becauseitisblastingstuffallov erthe
placeandgoingupanddown,doesn’t
follow the air.
“The whole idea with superpressure is
that once you set it,forget it, it really moves
like the atmosphere. We were able to carry
instruments, dograbtests, do science and
had positive PR. We hada lot of visibility
and people liked it.It heightened the aware-
nessof the air quality. At the same time it
got us some interesting data.
“The problem is that you have got to
designit,buildit,andflyit.Youn eed
somekindof infrastructure.Thewhole
ATMOSAT programwas abouta half a
milliondollardealandIdidn’thave
Forbesanymore.SoI hadtofinda way
todothese things.”
Heinsheimer’s balloon made about a
dozen scientific flights, most in Southern
California. One of the lo nger flights was
madetotestemissionsfromtheFour

Corners power plant in New Mex ico. The
flight landed108milesnorthinUtahat
nightwhentheyranout of altitudewith
rising terrain.
“TheATMOSATwasjustafirst
attempt, a p rototype,” says Heinsheimer.
“Itwasbuilt fromwovenKev lar witha
mylar film over it. The ten meter balloo n
wasbuilttorupture at100millibarsof
pressure.Wegroundtesteditto50and
flew it at 35 millibars. It was not capable
ofdoing a day/night cycle without throw-
ingoutballast.”
Ac cord in gt oRo gerBark er,
Schjeldahl b uilt the balloon, on the agree-
ment that noonewouldever know that.
Barkermad eanumberofflightswith
Heinsheimer including a memorable plea-
sure flight along the southernCalifornia
coast.
“We took off at the o ldNike b ase in
PalosVerdes,flewoutovertheocean
towardCatalina,camebacktowardthe
peninsula, up the coast to the n orth, flew
directlyo verLAX at2,000feet, swung
aroundparallelin gthemountainsand
landedindowntownLos Angelesat the
Coliseuminthegrassyarea bythe Na-
tional History Museum. Wethrew out the
trailropeandtoldabunchofFrisbee
players to tie it around a tree. The balloo n
flewaton ealtitude,justfollowingthe
willy-nillywindsthat day.“
Thelastfligh toftheATMOSAT
came in May 1984. The Fédération Aéro-
nautique Intern ationale had recently cre-
atedtheAS,or superpressure,category
for ballo ons. Withfree heliumleftover
fromtheGordonBennettgasballoo n
race in Palm Springs, Barker made a solo
flight andestablished distance and dura-
tion records for AS-4 size and up of 22.9
milesan d sevenhours49 minutesaloft.
As one of the quirks of aeron autical
recordsetting, the ATMOSAT was now
in the reco rd books un der two categories.
Heinsheimer,previoustothenewcat-
egorybeingestablished, flew 571miles
on one flight andhad ano ther flight of 32
hoursand32minutes.Bothofth ese
recordswere intheAA-4categorythat
stoodas national records until surpassed
inthe 1990’s.
Bytheearly80’sJulianNotthad
come to the conclusion that superpressure
was the way to circumnavigate the world
by balloon. “The balloon was made out of
a rather conventional woven nylon with a

fairlyconventionalpolyurethanecoat-
ing.The strengthmemberswere Kevlar
[load] tapes,” Nott says.
Nott made twoflightsoftheproto-
typ ein Australia. Atwo hourtest flight and
aflightacross Australiathat setthreerecords
forAS-6categoryandabove:altitude
17,767.93feet;distance1,486.03miles;
duration 33 hours, 8minutes, 42 seconds.
“Ithoughtweweregoingdowna
good track,” says Nott tod ay, referring to
thetesting. “Whatwe learnedfromthat
prototype was how to make a very effec-
tivesuperpressureballoon .I feltthatit
wasgoingtobeenormouslyexpensiv e.
Atleasthalfamilliondollars.Inthose
days it was an impossible amount to raise
for aflightaroundthe world. Theother
thingthatwasnotsogoodaboutit,the
superpressureballoon is wonderful ifyo u
want to fly at a constant level. But on an y
practical fligh t withacrew yo uhaveto
change altitu de.”
Th el as tat tem ptt ou s ea
superpressure balloon was January 1991.
40-year old Fumio Niwa, a technical en-
gineer for a Japanese co mputer firm, died
ofhypothermiaafterhissoloPacific-
crossingballoonfailed.Niwareported
hearing a loud “p ow!” The balloon began
to descend and Niwa was forced to ditch.
Itwashissecondattempttocrossthe
Pacific. The first, in mid-February 1989,
ended with an ocean ditching some 1,50 0
milessoutheast of Japan.
While hot air, gas, andRoziere bal-
loons trace their lineage back to the eigh-
teenthcentury,man nedsup erpressure
ballooningisarelativelynewdevelop-
ment. Coy Foster’s upcoming flights will
extend the bo dy of knowledge. How suc-
cessful willhe be?
“Thesuperpressureballoonisde-
signedto fly at onealtitu de.” saysNott.
“If Coy does it right he should be able to
fly to the east coast [from Plano, Texas].
If he really does it right, he should be able
tofly