nasa facts explorer xvi the micro meteoroid satellite

8/8/2019 NASA Facts Explorer XVI the Micro Meteoroid Satellite

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Page 1AAn Educational Services Publication of the

National Aeronautics and Space Administration\lol. I! No. 4(Replaces A-1 -63) / Source of AcquisitionEXPLORER XV / NASA Contractor/Grantee

CROMETEORO D SATELL

Explorer XV I in orb it (artist's conception). Experiment devices are indicated.NASA's Explorer XVI satellite collected and

transmitted information about micrometeoroids-tiny bits of matter speeding through space andsometimes entering the earth's atmosphere.

Micrometeoroids are much smaller than themeteors or "shooting stars" which cross theheavens with bri lli an t effect at certain times ofthe year. Meteors encountered in space areal led meteoroids. The much smaller particlestudied by Explorer XV I are called micro-

Sent into orbi t December 16, 1962, theMicrometeoroid Satellite transmitted data relat-ing to the number o f micrometeoroids encoun-

tered, the force with which they bomb arded thesatellite's structure, their destructive effect, andthe comparative resistance of different thick-nesses and types of mater ials to penet ration bythe micrometeoroids.

Data on the momentum of the particles havehelped determine the mass (amount of matter),distribution, and flux (rate o f flow) of micro-meteoroids in the path of Explorer XVI. Resultsof the studies are expected to contribute to thedesign of future spacecraft by determining whatdamage may be done b y micrometeoroids, andhow to guard against such damage.


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Page 2Explorers I hrough XV are described in NASA FACTS-

TH E EXPLORER SATELLITES (E-10-62).The Explorers are geophysical satellites of various con-

figurations developed to study the space environmentand upper atmosphere surrounding earth, including suchphenomena as radiation, micrometeoroids, tempera-tures, magnetic field, and solar plasm a. Investigationsa t greater distances are accomplished by other devicessuch as the Pioneer, Ranger, and Mariner spacecraft.--M I C R O M E T E O R O I D S - A S PA CE E N I G M ALittle i s known about micrometeoroids. Knowl-

edge about these enigmatic particles stems fromradar and optical tracking of their trails afterthey hit earth's atmosphere and from their im-pacts with instruments of spacecraft. Amongother spacecraft that have provided informationon micrometeoroids are the Explorers I, VII, andVl ll and the Vanguard Ill satellites; the Pioneer Iprobe; and Mariner II, the instrumented vehicle

NASA FACTS (VOL. I I NO. 4)their momentums on striking spacecraft detectors,indicate velocities rang ing from about 25,0 00 toapproximately 160,000 miles per hour.

I t i s theorized that micrometeoroids are grain- asized cousins of the meteoroids. If this i s true,micrometeoroids are composed of iron, silicates,and other substances found o n earth. Analysesof meteorites (meteoroids that have fallen toearth) have revealed that they are constituted ofsuch substances.

Suggestions regarding origins of micrometeor-oids include the possibility that they are pulver-ized remnants of colliding asteroids ormeteoroids, residues of former comets, leftoversof a great cloud of dust and gas from which thesolar system may have been formed, and t'iosenear ear th perhaps have been cast off by themoon.

NA SA technician prepares Explorer XVI for vacuum chambertest in whic h extremes of heat and cold expected in spaceare simulated.

sent from earth to the neighborhood of Venus.Spacecraft have discovered that periodically

there are micrometeoroid showers lasting fromseveral hours to a few days. Comparison ofmicrometeoroid counts provided by satellites nearearth with reports of Mariner II and Pioneer Iindicates that micrometeoroid density tends todecrease with distance from earth. As an exam-ple, analysis of Mariner I1and earth satellite data

ows that micrometeoroids in space near earthe about 10,000 times more abundant than

along Mariner's trajectory in interplanetary space.Calculations of particle speeds, based upon

NASA technicians test four-stage Scout launch vehicle. NoteExplorer XVI in foreground. Covering which protects satel-lite durin g launch, is jettisoned i n orbit.

SPACECRAFT EXPERIMENTSThe experiments o f Explorer XVI were designed

primari ly to tel l what m icrometeoroids can do tomaterials that may be used in future spacecraft.They were also aimed at gathering additionalinformation on these particles.

The satellite's array of instruments and sensorsincludes the following:

i(1 Pressurized cells shaped like half cylinderswith walls fashioned from one-thousandth to five-thousandth inch thick bery llium copper. The @cells contain helium gas held under pressure. A


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Page 4beryllium-copper walls, ( 1 above; 6 penetrationsof its one-thousandth inch thick stainless steelsurface and one penetration of its three-') thousandths inch thick stainless steel surface, (2)above; and one break i n each of the two- andthree-thousandths inch thick copper wire grids,( 3 ) above. N o penetrations occurred in the five-thousandths inch thick beryllium copper ( 1 ) orthe six-thousandths inch stainless steel (2).More than 15,000 meteoroid impacts wererecorded by the impact sensors (5 ). Solar cellsshowed little deterioration (6). The thin plasticsheet covering one cadmium sulfide cell ( 4 ) waspierced so many times tha t the cel l became satu-rated with sunlight and was no longer useful.This was expected.

SATELLITE MEAS UREMENTS A N DL A U N C H A N D O R BIT AL D A T A

Explorer XVI i s built around the spent fourthstage of the Scout launch vehicle. The space-craft i s 2 feet in diameter and 6% feet long andweighs 2 22 pounds.

Traveling in an orbit ranging from about 465to ap proximate ly 7 3 0 miles from earth, the sat-elli te circles the globe every 1 0 4 minutes. Theorbit of Explorer XVI i s incl ined about 5 1 de-grees to the equator, traversing a ground area

launch vehicle now being fligh t tested. The satelliteswi ll w eigh abou t 4,000 pounds and have o surface areaof approx imately 2,000 square feet, contrasted with Ex-plorer XVl that exposes a 25-squ are-foot area. Thick-nesses of experimental materials will be greater thanthose used on earlier micrometeoroid satellites such asExplorer XVI. The satellites' greater size, larger ex-posed surfaces, and increased skin thicknesses areexpected to make new information available as to thepenetra ting power, distribution, and magnitude of mete-oroids and micrometeoroids.

Planned orbits of the satellites are 300 to 600 milesatellites are expected to provideed i n design of large manned and

NASA FACTS (VOL. I I NO. 4)stretching from England to Cape Horn at the south-ern end of South America.

Explorer XVI was launched by a Scout vehiclfrom Wallo ps Station, Virg inia, at 9:33 a.mEST, December 16, 19 62 . The Scout is the Ntion's only launch vehicle powered solely by so11propellants . The four-stage 72- foo t-h igh boostercan orbi t a 24 0-p ound spacecraft or send a 100-pound package of scientific instruments on anup-down trajectory reaching as far as 7,000miles into space.

NASA FACTS forma t is designed for bulletin-boa rd display NASA FACTS is an educational publication of NASA's Divisionuncut, or for 8 x 10% looseleaf notebook insertion when of Educational Programs and Services. Itwill be mailed tocut along dotted lines and folded along solid lines. For addressees who reques t it from: NASA, Educational Publica-notebook ring insertion, punch at solid dots in the margins. tions Distribution Center, AFEE-1, Washington, D.C. 20546.

* U S GOVERNMENT PRINTING OFFICE 1964 OF-742-021For sale by the Super~ntendentof Documc'lts, U.S. Government Prlntlng Office

Washington 25, D.C.-Price 10 cents per copy.

Scout poised for launch of Explorer XVI.

nasa facts explorer xvi the micro meteoroid satellite

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