Baum­gart­ner’s suit broke the sound bar­rier

Science Illustrated - - SCIENCE UPDATE -

Felix Baum­gart­ner was the first to break the sound bar­rier in a free fall in 2012, when he jumped from a bal­loon at an al­ti­tude of al­most 29 km. Now, sci­en­tists from the Tech­ni­cal Uni­ver­sity of Mu­nich, Ger­many, have cal­cu­lated how he could ob­tain such a fall­ing ve­loc­ity.

Baum­gart­ner’s suit was a cus­tomised, tight­fit­ting pres­sure suit, which was not par­tic­u­larly aero­dy­namic. Its sur­face was wrin­kled just like an or­di­nary boiler suit.

It is com­pli­cated to pre­dict what hap­pens to the air cur­rents around a fall­ing body, when it ap­proaches the speed of sound. The air be­haves dif­fer­ently, and shock waves and tur­bu­lence de­velop, which func­tion as an aero­dy­namic brake block. But ac­cord­ing to the sci­en­tists’ cal­cu­la­tions, Baum­gart­ner’s wrin­kled suit sur­face sur­pris­ingly did not slow him down, on the con­trary. Whereas the brake block ef­fect would dou­ble, if a smooth body fell in the same way, the ef­fect re­mained al­most un­changed in Baum­gart­ner's case. The as­ton­ished sci­en­tists had to ac­knowl­edge that a sur­face with many in­den­ta­tions and bumps is use­ful, if you wish to fly at the speed of sound or faster.

The ir­reg­u­lar sur­face is prob­a­bly re­spon­si­ble for Baum­gart­ner reach­ing the speed of sound much ear­lier than ex­pected. The re­sults are rel­e­vant to en­gi­neers work­ing on fu­ture pas­sen­ger planes, which will also be trav­el­ling at speeds close to that of sound.

The wrin­kled suit that Baum­gart­ner wore dur­ing his free fall made him break the sound bar­rier much ear­lier than ex­pected.

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