Mon­ster rocket re­peats his­tor­i­cal mis­sion

50 years ago, the most pow­er­ful rocket ever, Sat­urn V, sent the first hu­mans to the Moon. In 2020, NASA will re­peat the le­gendary Apollo 8 mis­sion with an un­manned rocket, when the even big­ger Space Launch Sys­tem is launched for the first time.

Science Illustrated - - SPACE -

up through the at­moshere, where it is sub­jected to im­mense forces due to air drag, af­fect­ing its ex­te­rior. In con­nec­tion with the launch, en­gi­neers’ ma­jor cause of worry is the max Q point. Max Q is the time of the flight up through the at­mos­phere, when air drag is at its max­i­mum. If a rocket sur­vives max Q, it will prob­a­bly re­sist any­thing in space.

Space dreams come true

The air drag in the at­mos­phere and the sen­si­tive weight balance mean that the load must be very con­sis­tent with the forces of the rocket. So, sev­eral dif­fer­ent weight cat­e­gories of booster rock­ets ex­ist. The high­est one, su­per­heav­ies, can lift more than 50,000 kg into an or­bit around Earth. Only this type of rocket can be used, when the great dreams of the space agen­cies are to come true in the 2020s by manned mis­sions re­turn­ing to the Moon and go­ing all the way to Mars.

So, NASA is work­ing on the last de­tails of the Space Launch Sys­tem (SLS), whose fi­nal ver­sion will be the largest rocket ever with a lift­ing ca­pac­ity of 130,000 kg. But NASA is by no means the only player. The Rus­sian Roscos­mos space agency is co­op­er­at­ing with the En­er­gia com­pany to develop a rocket. The project, which is known as the Su­per Heavy Rocket, will be in­tro­duced in 2028. And in China, the CNSA space agency is test­ing the en­gines of the huge Long March 9 rocket, which, with a po­ten­tial lift­ing ca­pac­ity of 140,000 kg, will even out­com­pete the SLS, if it is com­pleted.

It is no longer only the ma­jor na­tional space agen­cies that develop huge rock­ets. The pri­vate space com­pany Blue Ori­gin has an­nounced its next ma­jor project by the name of New Glenn. With a lift­ing ca­pac­ity of 45,000 kg, the rocket is not very large, but un­like other rock­ets, New Glenn can be reused about 100 times. The SpaceX com­pany, which now com­mands the most pow­er­ful rocket, Fal­con Heavy, is busy de­vel­op­ing an even larger craft, the Big Fal­con Rocket (BFR), that will be a com­bi­na­tion of a booster rocket and a space­craft along the lines of the pen­sioned off space shut­tle.

En­gines are im­proved

The ma­jor dif­fer­ence be­tween the new huge rock­ets and their pre­de­ces­sor, Sat­urn V, is the quan­tity of com­puter power. The dig­i­tal revo­lu­tion has had a ma­jor im­pact on what is pos­si­ble in con­nec­tion with mod­ern aero­space ac­tiv­i­ties, par­tic­u­larly when it comes to engine con­trol. When the five pow­er­ful F-1 en­gines of the Sat­urn V rocket were ac­ti­vated, they more or less con­tin­ued at the same

force, un­til the tanks were empty. Fal­con Heavy’s 27 en­gines can vary their in­ten­sity via dig­i­tal con­trol. As soon as the rocket has lifted off from the ground, the main rocket's nine in­ner­most en­gines are turned down to save fuel, un­til the craft reaches an al­ti­tude, where lower at­mo­spheric pres­sure means that the en­ergy of the fuel is bet­ter uti­lized.

3D print­ing makes rock­ets sturdy

Im­proved fuel and more pow­er­ful en­gines that are able to send rock­ets on ever longer mis­sions re­quire con­struc­tion meth­ods that pro­duce durable rock­ets.

Dur­ing launch, NASA’s SLS rocket will be sub­jected to a heavy im­pact, when ac­cel­er­ated from 0 to al­most 30,000 km/h in only eight min­utes. At the same time, the tem­per­a­tures in the in­te­rior of the rocket’s en­gines will reach some 5,000 de­grees, whereas the ex­te­rior hull must be able to re­sist space tem­per­a­tures of hun­dreds of de­grees below zero. In re­cent years, a new weld­ing method and 3D print­ing of engine parts have made things eas­ier.

Or­di­nary weld­ing be­tween two plates con­sti­tutes struc­tural weak­nesses of a rocket hull. It makes the sur­face un­even and so more sub­jected to the forces of air drag, mak­ing it dif­fi­cult to guar­an­tee the metal’s sub­se­quent strength. But with a new method known as fric­tion stir weld­ing, en­gi­neers can ob­tain wider weld­ing. The weld­ing method is car­ried out with a fast- ro­tat­ing cylin­der, which moves along the joint, forc­ing it­self against the plates. The fric­tion makes the plates melt, and the cir­cu­lar mo­tion en­sures an even distri­bu­tion of the molten mass. In this way, you get a wide, tran­si­tional link be­tween the two plates, which al­most be­come one, as the weld­ing hard­ens.

In other cases, en­gi­neers have man­aged to elim­i­nate the need to weld by means of 3D print­ing. 3D print­ers have the ad­van­tage that that they can pro­duce one-piece parts of the rocket with very high struc­tural strength. In De­cem­ber 2017, NASA tested an engine with a 3D printed pogo ac­cu­mu­la­tor, i.e. a sphere­shaped, hol­low de­vice that ab­sorbs the im­pact oc­cur­ring, when fuel flows through the engine un­der high pres­sure. The ac­cu­mu­la­tor re­duces the pogo ef­fect, which is a haz­ardous phe­nom­e­non, that oc­curs when the vibrations be­come self-per­pet­u­at­ing. At worst, the pogo ef­fect could tear the en­tire rocket apart. The 3D printed engine part func­tioned wery well, and NASA aims to take a closer look at which other parts can be made us­ing a 3D printer.

Re­cy­cling causes rocket ma­nia

Fal­con Heavy’s his­tor­i­cal test launch proved that rocket en­gi­neers have come much fur­ther since the hey­day of Sat­urn V. It was clear, when the rocket’s first three stages landed syn­chron­i­cally and ver­ti­cally on the ground after hav­ing launched the load into space; a feat that seemed im­pos­si­ble just a few years ago. Rocket re­cy­cling fi­nally al­lows pri­vate com­pa­nies to of­fer tourist mis­sions into space that peo­ple can af­ford. The Blue Ori­gin com­pany is fine-tun­ing a rocket that can launch a small cap­sule with six pas­sen­gers into space, and the first tick­ets will be put up for sale al­ready next year.

In 2014, the Orion cap­sule was tested for the first time in prepa­ra­tion for the mis­sion around the Moon in 2020. 1 NEW­TON IS THE FORCE RE­QUIRED TO AC­CEL­ER­ATE 1 KG TO 1 M/S IN 1 SEC­OND.

1968 S AT U R N V

2020 SLS

N E S N JE L U J EL K I M

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The le­gendary Earthrise photo was taken by Apollo 8 as­tro­naut Bill An­ders on 24 De­cem­ber 1968.

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