【正文】 這早就是實現(xiàn)登月任務(wù)的太空迷們的夢想。沃納?馮?布勞恩是設(shè)計了土星五號月球火箭的天才，他在自己1948年出版的《火星計劃》一書中便開始籌劃火星探險，在阿姆斯特朗和奧爾德林博士成功登月后不久他便向當(dāng)時的總統(tǒng)理查德?尼克松拋出了一份火星載人航天計劃。But it was not to be. The Apollo Moon programme was shut down early, and the world’s astronauts have spent the past 41 years pootling around in lowEarth orbit. Now, though, spurred by the rise of the buccaneering, privatesector “New Space” industry, which is offering access to the cosmos at prices far lower than governmentbacked rockets can manage, the old dream is enjoying a resurgence. Elon Musk, whose rocket firm SpaceX already flies cargo to the International Space Station (ISS), makes no secret of his Martian ambitions. Two privately run organisations in particular—Inspiration Mars, brainchild of Dennis Tito, an American tycoon who became the world’s first space tourist in 2001, and Mars One, run by Bas Lansdorp, a Dutch entrepreneur—have announced plans to send people to Mars without relying on the resources of a state.但是該計劃并未成行。阿波羅月球計劃早早便被終止，全球的宇航員過去的41年里都在近地軌道中逡巡不前。然而，受到冒險的私營“新太空”產(chǎn)業(yè)能以比政府背景的火箭的價格低得多價格進(jìn)入宇宙的出現(xiàn)的激發(fā)，現(xiàn)在舊夢正在重燃。艾龍?馬斯科毫不遮掩自己對火星的野心，他的火箭公司太空探索技術(shù)公司已經(jīng)在向國際空間站（ISS）運送貨物。特別是兩家私營機構(gòu)“靈感火星”（美國大亨丹尼斯?提托的創(chuàng)意，他于2001年成為世界上第一位太空游客）及“火星一號”（由荷蘭企業(yè)家巴斯?蘭斯多普負(fù)責(zé)）公布了不依靠國家資源將人類送上火星的計劃。Mr Lansdorp admits that, on hearing about his plans, people’s first response is that he must be crazy. But both he and Mr Tito (who started his career as an engineer at the Jet Propulsion Laboratory, JPL, in Pasadena, which runs NASA’s unmanned Mars missions) insist they are serious. Technical studies have been done, astronaut applications are being processed and deals are being signed with the firms that will build the spacecraft.蘭斯多普承認(rèn)，人們在聽到他的計劃后，第一反應(yīng)便是他肯定是瘋了。但是他和提托（其職業(yè)生涯始于在噴氣推進(jìn)實驗室（JPL）擔(dān)任工程師，該實驗室位于帕薩迪納市，負(fù)責(zé)NASA的無人火星任務(wù)）均堅稱自己是認(rèn)真的。技術(shù)研究已經(jīng)完成，宇航員選拔正在進(jìn)行，與建造太空船的公司的協(xié)議也正在簽署中。Both men are motivated by frustration with government efforts, which have gone around in circles—and not orbital ones—for decades. It is the stated policy of Barack Obama’s government to send a crewed mission to Mars in the 2030s. But given the recent history of NASA as a political football (the George Bushes senior and junior both proposed similar missions that went nowhere), and given looming cuts to its budget, few think such a mission will actually happen. As Mr Tito put it when he announced Inspiration Mars: “the way we’re going, we’ll never get started.”數(shù)十年來政府做了不少嘗試，但卻只是團團亂轉(zhuǎn)而已（不是圍著軌道轉(zhuǎn)），這兩個人都是由此化失望為動力。巴拉克?奧巴馬的國策便是要在21世紀(jì)30年代完成火星的載人飛行任務(wù)。但是考慮到NASA最近作為政治足球的歷史（老布什和小布什都提出了類似的計劃，但均不了了之），再考慮到其預(yù)算即將被削減的情況，幾乎沒人認(rèn)為這項任務(wù)真的可以成行。正如提托在其公布“靈感火星”計劃時說的：“按照我們現(xiàn)在的行事方式，我們永遠(yuǎn)都不會有開始。”Cando talk aside, there are good reasons for scepticism. Sending people to Mars will be extremely difficult。 far harder than sending them to the Moon. For one thing, Mars is much farther away. The Apollo missions took three days to get there, but flight times to Mars are measured in months. That would require an utterly reliable spacecraft. The vast distance imposes a munication delay, too. Whereas the Apollo astronauts could talk to their groundbased controllers more or less in real time, Martian astronauts would face delays of up to 40 minutes between asking a question and getting an answer.樂觀的言論只是一方面，還有好幾點值得懷疑。將人類送上火星將會極其困難，比將人類送上月球要難得多。其一，火星要遠(yuǎn)的多得多。阿波羅計劃的宇航員花了三天時間到達(dá)月球，但是到達(dá)火星的飛行時間是以月為單位的。這意味著需要非?？煽康赜钪骘w船。而且遙遠(yuǎn)的距離還會產(chǎn)生通訊延遲。阿波羅計劃的宇航員可以和自己的地面指揮員進(jìn)行近乎實時的對講，而火星宇航員則要面臨長達(dá)40分鐘的應(yīng)答延時。And spending months in deep space would expose a crew to a chunky dose of radiation. Information from the Curiosity rover’s flight to Mars, just published in Science, suggests a crew could expect a radiation dose close to the maximum lifetime limit for NASA’s astronauts. If the sun were to have one of its regular temper tantrums, known as coronal mass ejections, which produce huge bursts of ionising radiation, that limit might be far exceeded.而且在外太空停留數(shù)月的時間會使宇航員暴露在超大劑量的輻射下。好奇號漫游車在其火星航程中獲得的信息剛剛發(fā)表在《科學(xué)》上，表明宇航員將會受到接近于NASA宇航員的最大終生限值的輻射劑量。如果太陽來一次它經(jīng)常性的暴怒，即所謂的日冕物質(zhì)拋射，此時會產(chǎn)生巨大的電離射線爆發(fā)，將會遠(yuǎn)遠(yuǎn)超出該輻射限值。When the stars are right等待時機Both missions hope to use SpaceX’s Falcon Heavy, a planned upgrade of its existing Falcon rocket. But even with access to cheap rockets, flying to Mars without the financial firepower of a government requires clever, and drastic, costcutting. In Mr Tito’s case, this means that although his astronauts will fly within about 140km (90 miles) of the Martian surface, they will not actually land. His mission calls for a twoperson craft—possibly a variant of SpaceX’s Dragon capsule, which is already used to ferry cargo to the ISS—to be sent on a “free return” trajectory to Mars. By clever design of its orbit, the craft can be sent to Mars with a single burn of its rocket engine. From thereon in, gravity takes over. The craft will swing around Mars and emerge on a trajectory precisely calculated to have it reenter Earth’s atmosphere several months later, with only minimal course corrections needed along the way. Orbital mechanics is one of Mr Tito’s specialities. Before he left JPL to bee an investment manager, he designed orbits for Mars probes.兩項計劃都希望使用太空探索技術(shù)公司計劃中的獵鷹重型火箭其現(xiàn)有的獵鷹火箭的升級版。但是即使可以得到廉價的火箭，沒有政府財源支持的火星航天任務(wù)不僅需要聰明才智還要大幅的成本削減。對提托的計劃來說，這意味著雖然他的宇航員會飛至距火星表面約140公里（90英里）的地方，但實際上并不會在火星著陸。提托的計劃需要將一艘雙人飛船可能是太空探索技術(shù)公司的“龍”飛船的一個變體，該飛船已經(jīng)被用來向國際空間站運送貨物送上一條通往火星的“自由返回”軌道。通過巧妙地設(shè)計其軌道，該飛船在飛往火星的過程中只需要使用一次自己的引擎，隨后，動力將會轉(zhuǎn)由重力提供。飛船將會繞過火星，然后出現(xiàn)在一條經(jīng)過精確計算的軌道上，使其可以在數(shù)月后重新進(jìn)入地球的大氣層，期間僅需要最低限度的航線修正。軌道力學(xué)正是提托的專長之一。在他離開JPL成為投資經(jīng)理前，他做的就是給火星探測器設(shè)計軌道的工作。Removing the requirement to land simplifies the task enormously. No plex manoeuvring into a Mars orbit is necessary. No landing craft is needed, nor any survival gear for use on the Martian surface. That saves fuel and, more importantly, launch mass (the overriding concern for any space mission). Mr Tito’s team hopes to wring further savings by launching in 2018, in order to take advantage of a rare set of celestial circumstances that allow a gravitypowered trip to Mars and back in 501 days, instead of the two years that w