大西洋月刊：离开太阳系比到达太阳更容易 [美国媒体]

MARINA KOREN AUG 10, 2018
In a very short time, we human beings haveseeded our corner of the universe with all kinds of signs of our existence. Wehave flung hundreds of satellites into the sky, cloaking the Earth intechnology. We sent spacecraft to swing by planets and moons, to orbit them, toroam their surfaces. A few years ago, we reached the invisible line between theend of our solar system and the beginning of everything else, and then piercedit, hurtling into the darkness beyond.

在相当短的时间内，我们人类已经在我们这个宇宙的角落里播种下了各种我们存在的迹象。我们已将数百颗卫星射上了天，用技术覆盖了地球。我们派出航天器造访行星和卫星，绕其轨道运行，漫游其地表。若干年前，我们抵达了太阳系和其他所有一切开始之地间的无形界限，然后穿过了它，冲进那方幽冥。

This last achievement, humanity’s escapefrom the solar system, was certainly astonishing, a testament to humaningenuity and engineering. But it was much easier than what we’re trying to donext.

人类溜出太阳系这个最终的成就当然会很惊人，这是人类巧思和工程能力的明证。但这比我们接下来设法要做的事简单得多了。



The reason has to do with orbitalmechanics, the study of how natural forces influence the motions of rockets,satellites, and other space-bound technology. Falling into the sun might seemeffortless since the star’s gravity is always tugging at everything in thesolar system, including Earth. But Earth—along with all the other planets andtheir moons—is also orbiting the sun at great speed, which prevents it fromsuccumbing to the sun’s pull.

个中原因和轨道力学有关，它研究的是自然力如何影响火箭、卫星和其他空间技术的运动。落入太阳也许看似不费力气，因为恒星的引力总是牵引着包括地球在内的太阳系中的一切。但地球，连同所有其他行星及其卫星也在以超高的速度绕太阳轨道运行，这阻止了它屈从于太阳的牵引力。

This arrangement is great if you’d like toavoid falling into the sun yourself, but it’s rather inconvenient if you wantto launch something there.

如果你想要让自己避免落入太阳，这种安排便是极好的，但如果你想要往那里发射些什么，就相当不便了。

“To get to Mars, you only need to increase slightly your orbitalspeed. If you need to get to the sun, you basically have to completely slowdown your current momentum,” says Yanping Guo, the mission-design andnavigation manager for the Parker Solar Probe. Based at the Johns HopkinsApplied Physics Laboratory, Guo has been working on the probe for about 17years.

“为了到达火星，你只需略微提升你的轨道速度。如果你需要到达太阳，基本上你必须彻底降低你目前的动量”，帕克太阳探测器的任务设计和导航负责人郭延平（音）表示。以约翰霍普金斯大学应用物理实验室为基地，郭一直致力于这个探测器已长达17年。

Probes bound for deep-space destinationslike Mars can piggyback off Earth’s momentum to fly faster. For a spacecraft tolaunch toward the sun, on the other hand, it must accelerate to nearly matchthe Earth’s velocity—in the opposite direction. With the planet’s motionessentially canceled out, the spacecraft can surrender to the sun’s gravity andbegin to fall toward it. But this is almost impossible with current rockettechnology, so spacecraft have to get some help, in the form of slingshotmaneuvers off other planets, called gravity assists.

飞往诸如火星的深空目的地的探测器可以借助于地球的动量以飞得更快。另一方面，对于一个朝着太阳发射的航天器，它必须在相反方向上加速，以赶上地球的周转速度。由于地球的运动基本上被抵消了，航天器就能向屈从于太阳的引力，并开始倒向它。但在目前的火箭技术下，这几乎是不可能的，因此航天器必须离开其他行星一定距离以弹射机动的形式得到一部分助力，这被称为引力助推。

Spacecraft usually use gravity assists totravel deeper into the solar system; in 2007, the Pluto-bound New Horizonsspacecraft approached Jupiter, dipped into the massive planet’s immense gravity,and then bolted away, moving faster than it approached.

航天器常使用重力助推的方式深入太阳系；在2007年，飞向冥王星的“新视野号”航天器接近了木星，利用这颗巨行星巨大的引力作用下沉，然后以比它靠近时更快的移动速度奔逸着脱离。

This time, the Parker Solar Probe willexperience seven gravity assists from Venus in order to draw closer to thecenter of the solar system. With each pass, the spacecraft will shed some ofEarth’s motion.

这次，帕克太阳探测器为了更加临近太阳系的中心，将会经历七次来自金星的引力助推。每经过一次，就会丧失一部分来自地球的运动能力。

The team behind the solar probe initiallyimagined the spacecraft would get this gravitational boost from Jupiter, theking of gravity assists thanks to its massive size and corresponding gravity.Parker would have needed to swing past Jupiter only twice. The sun “is the mostchallenging destination to reach in the entire solar system without a gravityassist,” Guo says. “Any available launch vehicle—even near-future, the mostpowerful—it won’t be able to shoot a spacecraft to get to the sun. You must usegravity, and not just a general gravity assist—you have to use the mostpowerful gravity assist.”

这个太阳探测器背后的团队，最初的设想是从木星得到这种引力推进，由于其巨大的体积及其相应的引力，木星堪称引力助推之王。帕克只需要绕飞临木星两次。太阳“在不借助引力助推的情况下，是整个太阳系中最富挑战性的目的地”，郭表示。“任何可用的发射载具，甚至在不远的将来最强大的也没有能力发射一个航天器抵达太阳。你必须借助引力，而且不只是普通的引力助推，你必须使用最强大的引力助推”。

Such a long detour would have required theParker Solar Probe to run on nuclear power. But about a decade ago, nasa toldthe Parker team it couldn’t build its spacecraft to operate that way. Engineershad to completely rethink their planned trajectory: Solar-powered spacecraft,they believed at the time, would be too far from the sun to function nearJupiter. (Things eventually changed, but not soon enough for Parker; thesolar-powered Juno reached Jupiter in 2016 and has been orbiting happily eversince.)

如此长距离的迂回要求帕克太阳探测器以核动力航行。但在约十年以前，NASA告诉帕克团队它无法造出以那种方式运行的航天器。工程师们不得不彻底重新考虑他们计划的飞行轨迹：当时他们相信，太阳能驱动的航天器离太阳太远了，是无法在木星附近运行的。（情况最终发生了变化，但对帕克来说还不够快；太阳能驱动的朱诺号探测器在2016年到达木星，并且自那以后一直状态良好地绕着轨道运行。）

The Parker team studied its options andsettled on Venus. In some ways, the new trajectory works out well. WithJupiter, the probe would have come closer to the sun, but it would have madeonly two passes. With Venus, the Parker Solar Probe will make 24 passes overits lifetime. The probe will spend more time sampling new territory around thesun and, scientists hope, provide answers to some outstanding questions aboutour star.

帕克的团队研究了它的选项，然后选定了金星。某种程度上，这条新轨迹很好地实现了预期效果。利用木星的话，探测器会飞临到距离太阳更近的地方，但它只能临经两次。而利用金星，帕克太阳探测器在其寿命周期中将会完成24次临经。该探测器将耗费更多时间在太阳附近的新领域中取样，而且科学家们希望，它能为关于我们恒星的一些亟待解决的问题提供答案。

nasa has previously launched severalsatellite missions toward the sun, but the field of heliophysics—the study ofthe sun’s effects on the solar system—remains quite new. The Parker Solar Probewill fly through one of the most mysterious regions of the sun: the corona, theouter layer of hot plasma stretching millions of miles from the surface, orphotosphere. Unlike the photosphere, the corona is visible to the naked eyeonly during a solar eclipse, like the kind that swept across the United Stateslast year.

先前，NASA已经发射过若干次指向太阳的卫星任务，但太阳物理学（即太阳对太阳系影响的研究）领域出现的时间还相当短。帕克太阳探测器将穿过太阳最神秘的区域之一：日冕，它是从太阳表面（或者说光球层）延伸数百万英里的滚烫电浆的外层。和光球层不同，日冕只在日食发生时才能被肉眼看到，就像去年掠过美国的那种。

Scientists don’t know why the corona is sohot; temperatures there can exceed 1.8 million degrees Fahrenheit (1 million degreesCelsius), while the photosphere remains at a comparatively cool 10,000 degreesFahrenheit (6,000 degrees Celsius). Nor do they know how exactly it generatesconstant streams of charged particles that unfurl across the entire solarsystem like tentacles, a phenomenon known as the solar wind.

科学家不知道为什么日冕会如此的热；那里的温度会超过180万华氏度（100万摄氏度），而光球层则会保持在相对凉爽的10000华氏度（6000摄氏度）。他们也不知道它是如何源源不断地产生带电粒子流，就像触角一样在整个太阳系中展开，这种现象被称为太阳风。

Scientists have spent 60 years thinkingabout the solar wind. Specifically, Eugene Parker, the American astrophysicistfor whom the nasa mission is named, first described the dynamics of solar windin 1958. “It was something most people couldn’t seem to swallow. They expressedstern disbelief,” Parker told Rebecca Boyle in Air & Space magazine thissummer.

科学家思索太阳风已经花了60年。特别是美国天体物理学家尤金·帕克，这个NASA任务是以他的名字命名的，他于1958年首次描述了太阳风的动力学。“这似乎是大部分人无法接受的”，这是帕克今年夏天在《航空与航天》杂志中透露给丽贝卡·博伊尔的。



Safe from the sun’s glare, the probe’sscientific instruments will operate at a balmy 78 degrees Fahrenheit (26degrees Celsius).

探测器的科学仪器会在温和的78华氏度（26摄氏度）下运转，以免受太阳的强光照射。

The Parker mission is scheduled to end in2025. After it pings home a final time, the spacecraft will, over the course ofmany years, succumb to the sun’s gravity. There, beyond the pull of anythingelse, Parker will dip closer and closer to our star. Under the scorchingconditions, it will crumble first into pieces, and then into dust. Years afterlearning to leave the solar system, humanity will have finally managed to plungeright into the heart of it.

帕克任务计划在2025年终止。在它最后一次发送信号回家后，经过多年航行该航天器将会死于太阳的引力。那里，在任何别处的牵引力不及之处，帕克号将会下降，离我们的恒星越来越近。在炽热的环境中，它先会碎成碎块，然后化为尘埃。在学会离开太阳系多年以后，人类终将设法径直闯进太阳系的核心。