{"id":4797,"date":"2026-06-20T04:00:48","date_gmt":"2026-06-20T02:00:48","guid":{"rendered":"https:\/\/studentmag.unipr.it\/?p=4797"},"modified":"2026-06-18T19:46:11","modified_gmt":"2026-06-18T17:46:11","slug":"la-fisica-dei-film-la-manovra-rich-purnell-in-the-martian","status":"publish","type":"post","link":"https:\/\/studentmag.unipr.it\/index.php\/2026\/06\/20\/la-fisica-dei-film-la-manovra-rich-purnell-in-the-martian\/","title":{"rendered":"La Fisica dei Film: La manovra Rich Purnell in &#8216;The Martian&#8217;"},"content":{"rendered":"<div class=\"fusion-fullwidth fullwidth-box fusion-builder-row-1 fusion-flex-container has-pattern-background has-mask-background nonhundred-percent-fullwidth non-hundred-percent-height-scrolling\" style=\"--link_color: var(--awb-color4);--awb-border-radius-top-left:0px;--awb-border-radius-top-right:0px;--awb-border-radius-bottom-right:0px;--awb-border-radius-bottom-left:0px;--awb-flex-wrap:wrap;\" ><div class=\"fusion-builder-row fusion-row fusion-flex-align-items-flex-start fusion-flex-content-wrap\" style=\"max-width:1144px;margin-left: calc(-4% \/ 2 );margin-right: calc(-4% \/ 2 );\"><div class=\"fusion-layout-column fusion_builder_column fusion-builder-column-0 fusion_builder_column_1_1 1_1 fusion-flex-column\" style=\"--awb-bg-size:cover;--awb-width-large:100%;--awb-margin-top-large:0px;--awb-spacing-right-large:1.92%;--awb-margin-bottom-large:0px;--awb-spacing-left-large:1.92%;--awb-width-medium:100%;--awb-order-medium:0;--awb-spacing-right-medium:1.92%;--awb-spacing-left-medium:1.92%;--awb-width-small:100%;--awb-order-small:0;--awb-spacing-right-small:1.92%;--awb-spacing-left-small:1.92%;\"><div class=\"fusion-column-wrapper fusion-column-has-shadow fusion-flex-justify-content-center fusion-content-layout-row\"><ul style=\"--awb-size:18px;--awb-iconcolor:var(--awb-color3);--awb-line-height:30.6px;--awb-icon-width:30.6px;--awb-icon-height:30.6px;--awb-icon-margin:12.6px;--awb-content-margin:43.2px;\" class=\"fusion-checklist fusion-checklist-1 fusion-checklist-default type-icons\"><li class=\"fusion-li-item\" style=\"\"><span class=\"icon-wrapper circle-no\"><i class=\"fusion-li-icon fa-camera fas\" aria-hidden=\"true\"><\/i><\/span><div class=\"fusion-li-item-content\">\n<p>crediti copertina e sovracopertina <a href=\"https:\/\/www.20thcenturystudios.com\/\" target=\"_blank\" rel=\"noopener\">20th Century Studios<\/a><\/p>\n<\/div><\/li><\/ul><div class=\"fusion-section-separator section-separator grunge fusion-section-separator-1\" style=\"--awb-spacer-height:43px;--awb-svg-margin-left:1.92%;--awb-svg-margin-right:1.92%;--awb-svg-margin-left-medium:1.92%;--awb-svg-margin-right-medium:1.92%;--awb-svg-margin-left-small:1.92%;--awb-svg-margin-right-small:1.92%;--awb-bg-size:100% 100%;--awb-bg-size-medium:100% 100%;--awb-bg-size-small:100% 100%;\"><div class=\"fusion-section-separator-svg\"><div class=\"fusion-grunge-candy-sep fusion-section-separator-svg-bg\" 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);height:43px;\"><\/div><\/div><div class=\"fusion-section-separator-spacer\"><div class=\"fusion-section-separator-spacer-height\"><\/div><\/div><\/div><div class=\"fusion-separator fusion-has-icon fusion-full-width-sep\" style=\"align-self: center;margin-left: auto;margin-right: auto;width:100%;\"><div class=\"fusion-separator-border sep-single sep-dashed\" style=\"--awb-height:20px;--awb-amount:20px;border-color:var(--awb-color2);border-top-width:3px;\"><\/div><span class=\"icon-wrapper\" style=\"border-color:transparent;font-size:23px;width: 1.75em; height: 1.75em;border-width:3px;padding:3px;margin-top:-1.5px\"><i class=\"fa-angle-double-down fas\" style=\"font-size: inherit;color:var(--awb-color2);\" aria-hidden=\"true\"><\/i><\/span><div class=\"fusion-separator-border sep-single sep-dashed\" style=\"--awb-height:20px;--awb-amount:20px;border-color:var(--awb-color2);border-top-width:3px;\"><\/div><\/div><\/div><\/div><div class=\"fusion-layout-column fusion_builder_column fusion-builder-column-1 fusion_builder_column_1_1 1_1 fusion-flex-column\" style=\"--awb-bg-size:cover;--awb-width-large:100%;--awb-margin-top-large:0px;--awb-spacing-right-large:1.92%;--awb-margin-bottom-large:0px;--awb-spacing-left-large:1.92%;--awb-width-medium:100%;--awb-order-medium:0;--awb-spacing-right-medium:1.92%;--awb-spacing-left-medium:1.92%;--awb-width-small:100%;--awb-order-small:0;--awb-spacing-right-small:1.92%;--awb-spacing-left-small:1.92%;\"><div class=\"fusion-column-wrapper fusion-column-has-shadow fusion-flex-justify-content-flex-start fusion-content-layout-column\"><div class=\"fusion-text fusion-text-1\" style=\"--awb-content-alignment:justify;\"><p><i>The Martian<\/i>, noto in Italia come <i>Sopravvissuto<\/i>, \u00e8 un film in cui l\u2019astronauta Mark Watney, interpretato da Matt Damon, rimane bloccato su Marte e deve aspettare il ritorno dei suoi compagni per essere salvato. Oggi andremo ad analizzare uno degli aspetti pi\u00f9 affascinanti del film: la manovra Rich Purnell.<\/p>\n<p>Durante il film, l\u2019equipaggio della nave scopre che il loro amico, presunto morto, \u00e8 ancora vivo e decide di tornare indietro. Il problema \u00e8 che anche loro sono a corto di cibo e provviste per un prolungamento della missione e il tempo stringe. Rich Purnell, giovane astrofisico del JPL (Jet Propulsion Laboratory), elabora un piano: prevede che la navicella, diretta verso la Terra, anzich\u00e9 rallentare, acceleri sfruttando la gravit\u00e0 terrestre per ottenere ulteriore velocit\u00e0 e dirigersi di nuovo verso Marte. Durante questo sorvolo della Terra vengono inviate le provviste necessarie per portare avanti la missione.<\/p>\n<p>Sfruttare la gravit\u00e0 di un pianeta come mezzo di propulsione non solo \u00e8 realistico, ma \u00e8 una tecnica ampiamente utilizzata in diverse missioni spaziali, come Voyager 1, Voyager 2 e Cassini\u2013Huygens. Questa tecnica si chiama <strong>effetto fionda gravitazionale<\/strong> e, proprio come una fionda, lancia un oggetto, ma senza bisogno di un elastico: ci pensa la gravit\u00e0. Questo stratagemma serve ad aumentare la velocit\u00e0 della sonda, modificarne la direzione e quantit\u00e0 di moto.<\/p>\n<p>Ma in fisica nulla si crea e nulla si distrugge, quindi da dove deriva questo aumento di energia e quantit\u00e0 di moto? Dal pianeta stesso. Infatti, la sonda prende una piccolissima parte dalla quantit\u00e0 di moto del pianeta. Questo \u201cfurto\u201d non ha conseguenze apprezzabili sul pianeta, ma consente alla sonda di raggiungere velocit\u00e0 enormi che richiederebbero quantit\u00e0 gigantesche di propellente. L\u2019effetto fionda ha consentito a molte missioni di diminuire sia i tempi di viaggio sia il carburante necessario.<\/p>\n<p>Quasi sempre si \u00e8 utilizzata la gravit\u00e0 di Giove, il re tra i\u00a0 pianeti del nostro sistema solare, per massimizzare l\u2019effetto. Pi\u00f9 grande e veloce \u00e8 la rotazione del pianeta, maggiore sar\u00e0 l\u2019accelerazione ottenuta. Ma nessuno vieta di fare lo stesso con mondi pi\u00f9 piccoli come la Terra. Questo \u00e8 esattamente quello che accade in <i>The Martian<\/i>.<\/p>\n<p>Fin qui la pellicola rimane abbastanza realistica, ma ci sono alcune considerazioni da fare. Come ogni film che si rispetti, l\u2019intera manovra \u00e8 stata abbastanza semplificata. Infatti le finestre orbitali reali sono rigidissime e nel film tutto avviene in tempi molto favorevoli alla trama. Nella realt\u00e0, missioni e lanci richiedono che i pianeti si trovino nella giusta posizione e che tutto avvenga in momenti estremamente precisi affinch\u00e9 la traiettoria funzioni correttamente. Non si tratta semplicemente di muoversi da un punto A a un punto B, come sulla Terra.<\/p>\n<p>Nello spazio, infatti, sia il punto di partenza sia quello di arrivo sono in continuo movimento, e bisogna calcolare la traiettoria corretta per non mancare il bersaglio e, soprattutto, per impiegare meno tempo possibile. La finestra di lancio \u00e8 l\u2019intervallo di tempo durante il quale una partenza permette di raggiungere il bersaglio desiderato. Tutto questo richiede calcoli e correzioni incredibilmente precise. Oggi utilizziamo supercomputer, ma in passato gran parte delle operazioni matematiche venivano eseguite quasi interamente a mano e con fogli di calcolo.<\/p>\n<p>La pellicola<i>,<\/i> pur semplificando tempi, calcoli e condizioni operative, riesce a rappresentare correttamente il principio fisico alla base delle missioni interplanetarie: sfruttare la gravit\u00e0 dei pianeti per ottimizzare energia e traiettorie. \u00c8 proprio grazie a idee come questa che sonde veramente realizzate hanno potuto raggiungere regioni dello spazio altrimenti inaccessibili.<\/p>\n<p><i>The Martian<\/i> mostra bene un aspetto importante della scienza moderna: anche le soluzioni pi\u00f9 \u201cimpossibili\u201d nella narrazione possono avere solide basi nella fisica reale, a patto di comprendere a fondo le leggi che governano il moto nello spazio.<\/p>\n<\/div><\/div><\/div><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"<p>L&#8217;effetto fionda gravitazionale che sfrutta la gravit\u00e0 e la rotazione del pianeta come propellente naturale<\/p>\n","protected":false},"author":8,"featured_media":4798,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[25],"tags":[113,202],"autore":[204],"class_list":["post-4797","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cool-tura","tag-film","tag-scienza","autore-andrea-salvemini"],"acf":[],"_links":{"self":[{"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/posts\/4797","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/comments?post=4797"}],"version-history":[{"count":7,"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/posts\/4797\/revisions"}],"predecessor-version":[{"id":4802,"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/posts\/4797\/revisions\/4802"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/media\/4798"}],"wp:attachment":[{"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/media?parent=4797"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/categories?post=4797"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/tags?post=4797"},{"taxonomy":"autore","embeddable":true,"href":"https:\/\/studentmag.unipr.it\/index.php\/wp-json\/wp\/v2\/autore?post=4797"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}