Editing Project Echo (section)

=== Echo 1 ===
Echo 1 was {{cvt|30|m}} in diameter, had a non-rigid skin made of {{cvt|12.7|µm}}-thick Mylar, and had a total mass of {{cvt|180|kg}}, weighing {{cvt|71|kg}} at launch. During ground inflation tests, {{cvt|18000|kg}} of air were needed to fill the balloon, but while in orbit, several pounds of gas were all that was required to fill the sphere. To address the problem of [[meteorite]] punctures and keep the sphere inflated, Echo 1 included a {{cvt|15.12|kg}} make-up gas system using two types of [[Sublimation (phase transition)|sublimating]] powders – {{cvt|9.1|kg}} of [[anthraquinone]] and {{cvt|4.6|kg}} of [[benzoic acid]].<ref>{{cite web |last1=Davis and Tanimoto |title=Mechanical Development of Antenna Systems |url=https://descanso.jpl.nasa.gov/monograph/series8/Descanso8_08.pdf |website=NASA JPL |access-date=8 January 2022}}</ref> It also had 107.9 MHz telemetry beacons, powered by five [[Nickel–cadmium battery|nickel-cadmium batteries]] that were charged by 70 [[solar cell]]s mounted on the balloon. The spacecraft was useful to the calculation of atmospheric density and [[radiation pressure#Solar radiation pressure|solar pressure]], due to its large area-to-mass ratio.<ref name=Jones1961/> It was held together with Schjelbond, a proprietary adhesive developed by the [[Gilmore Schjeldahl#Schjeldahl Company|Schjeldahl company]].<ref name="gilmour">{{cite news |last=Gilmour |first=Gerry |date=1999-09-11 |title=A mind for business: Schjeldahl's ingenuity helps keep bread fresh, hearts safely beating |url=http://legacy.inforum.com/specials/century/jan3/week38b.html |url-status=dead |archiveurl=https://web.archive.org/web/20110713032131/http://legacy.inforum.com/specials/century/jan3/week38b.html |archivedate=2011-07-13 |work=The Forum |location=Fargo, North Dakota}}</ref>