10 Braving the Elements

reactive as individual atoms: they spontaneously bind togetherto form hydrogen molecules. H2. A flask of hydrogen gas con-tains mariy such molecules, which rcipidly move throughout thecontainer and bounce off its walls. Unlike helium, hydrogen gasundergoes many chemical reactions and explodes when ignitedin air. The reactivity of hydrogen molecules arises because thebond between the two atoms breaks and the free atoms can thenbind to other atQms. A helium atom cannot make bonds andtherefore is u.nreactive. The difference in the chemistry ofhydrogen and helium can have dramatic consequences.

The Hindenburg

Hundreds of men an9. women and a fewchildren craned. their necks skyward asthe leviathan .cruised toward them at 70'mph. Nearly 250 ground crew scurriedabout the 'U.S. Naval air'station at Lake-

hurst, New Jersey. Most had been waitingseveral hours for the thundershQwers toabate so that the airship could dock. Thedrone of four 16-cylinder4iesel enginesstilled the chatter on the ground.. Mahog-any-walnut lamimite'prop'ellers 20 feet indiameter thrust the hulk tow.ard the

crowd. Many of the 37"passengers had rel-atives or American hosts waiting below.Some waved excitedly ITom the windowsof rectangular cabins built into the mas-sive airship's belly. The image of an objectalmost three football fields long pressedinto the consciousness of the earthboundgawkers.

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Aloft. a crew of 54 prepared hurried-ly for descent. Teams of two mechanics

. monitored each engine. Others readiedtrail lines, spider cables, and hand ropes,which would be dropped shortly. Cabinattendants briefed the passengers ondeparture procedures. Dos:;king almostseemed routine to them now. Most of the

crew had worked the world's fir~t regulartransatlantic air route for' exactly a year.Ads in The New York Times regularlytouted their service: "Europe by Air in 21/2days-$400 incl. berth, meals, tips." Inseveral minutes the tired cre,:" wouldleave their floating workplace for some'food and sleep. Sailing above th~AtlanticOcean at a 700-foot altitude lds~ its nov-

elty after several voyages. .In the forward control gondola,

Captain Max Pruss examined the activity

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on the ground to verify the radio messagethat gave him the go-ahead to dock. Noothecman had the ability to maneU\.er thePromethean dirigible as if it were a smalltoy. A repaired tail fin, evidence of ~ pre-vious skipper's mistake, certified theclaim. Captain Pruss vented some hvdro-gen gas through valves on top of the shipand ordered the engines reversee! to brc)kethe craft. 8y dropping water ballast. hetrimmed the floating sausage's nose up afew degrees in preparation for docking.Within rt fe-w minutes. the ship drifted "I

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Imere 75 feet above the ground. Telephoneorders went out to the crew at 7:21 P.i\Lto

drop the 300-foot-long forward trail linesand slow the ..engines. 0;, the ground,teams of men ratEJd to retrieve these ropesami attach them to two mooring cars onrails that encircled the massive steelmooring mast that served to anchor thenose. Unexpectedly, the craft's momen-tum caused it to glide several hundredvards past the mast. One. mooring linesnagged taut and threw the airship off bal-8nce. The engines were revved up and

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The Hindenburg £.yplosiolJ. (The Bettman Archi','e.]

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Captain Pruss yelled to the crew to payout the lines.

Whether it was sabotage, structuralfailure, a faulty vent valve, or simply a ripin a gelatin-painted cotton gas cell. hydro-gen gas leaked out near the vessel's stern.This produced little effect, until thehydrogen ignited-perhaps just from stat-ic electricity. Hydrogen molecules insidethe 16 gas cells within the ship werepoised to. combine with atmospheric oxy-gen and produce watcr vapor. All theyneeded was a spark of energy to start thereaction. Thereafter, the reaction energyitself helped propagate' the chemicalchange. (Ironically, the ship's flotationcells were designed to use helium, an un-reactive gas. However, under the HeliumControl Act the world's sale supplier-theUnited States-limited trade to favorednations.)

When the trail lines dropped. HerbMorrison reco.rded a radio broadcast ofthe year's firSt transatlantic flight by a pas-senger airship. "Passengers are lookingout of the \vindows waving; the ship isstanding still now. The vast motors arejust holding it, just enough to keep itfrom It's broken into flames! It's flash-

ing! Flashing! ". Within seconds a whiteball of flame mushroomed into the sky.

Oxygen 111()1(~cules ",vel'() drawn in 'froll]

the surrounding air by the updraft of hotgases racing skyward. The craft's outerlinen skin burned away to reveal duralu-minum alloy girders and bracing wire.Thunder punctuated the sky whenenough air mixed with pockets of hydro-gen to create explosive mixtures. Hydro-gen gas containing as little as 6°!c,air canexplode. With the disintegration of thedirigible's tail section, the loss of aft liftcausecllhe nose to shoot 500 feet into the

air. The sixteen gas bags inside the shellruptured sequentially and released sevenmillion cubic feet of hydrogen to fuel thefire storm. A wall of flame erupted fromstern to stem in 34 seconds.

Frantic ground crew qnd onlookersraceel to escape the hell above. One didn'tmake it. Terrified passengers leaped fromthe windows, with flames at their backs.The twisted aluminum skeleton. with

intact passenger pods beneath, collapsedto earth in a smoking ruin. Of the 97 onboard, 22 crew members and 13 passen-gers died. Many more were severely in-jured on that overcast May evening in'1937 when the pride of Nazi Germany, thelargest aircraft ever flown, fell victim tothe chemical energy stored in a hydrogenmolecule.

The Periodic Table

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Organizing the elements into tabular form posed a difficult prob-lem for chemists. Early tables simply listed the elements in 'orderof increasing atomic weight. This arrangement, however, pro-

.,:..I~r1"" in<;ioht into the chemistry of the elements. pth,er