NASA的新火星着陆方式.doc

NASA Bets Big Rover On Novel Landing Scheme Aug 1, 2011 By Frank Morring, Jr.Washington 1 2 3 4 Next Page NASA will try a completely new—and scary—technique to land the largest rover yet on the surface of Mars next year, in a spot that scientists hope will tell them whether the planet can, or ever could, support life. 2012年虽然是电影中的地球毁灭之日，不过NASA还是打算继续实施自己的火星探索计划。NASA计划在2012年发射一个大型漫游车到火星表面，用来进一步探究火星上是否曾经存在生命，是否可以供人类居住。这个漫游车名为“火星科学实验室”，从名字上就可以看出它功能多、个头大。“火星科学实验室”重850千克，有6个轮子，大小和常见的家用轿车差不多。所以，如果要用常见的伞降方式把它着陆到火星表面，就要携带一套巨大的降落伞。这对地球上的航空伞降和近地轨道飞船伞降返回来说，不是什么大问题，毕竟不需要把这套东西送离地面太远，消耗的飞机或者火箭燃料有限。但如果是火星登陆，为运送降落伞系统而消耗的燃料就有些难以承受了。因此，NASA打算另辟蹊径。 Crews from the Jet Propulsion Laboratory (JPL) and Kennedy Space Center are in the final stages of preparing the $2.5 billion Mars Science Laboratory (MSL) for an Atlas V launch to the red planet as early as Nov. 25. If all goes as planned, the probe will reach Mars next August and begin its harrowing 6-min. descent through the atmosphere. After an entry that includes a temporary shift in the capsule’s center of gravity to gain lift before parachute deployment for a precision approach, the lander will go into a rocket-powered hover and lower the rover to the surface on nylon cords. Engineers at JPL adopted the “Sky Crane” landing technique because, at 850 kg (1,870 lb.), the six-wheel rover, dubbed Curiosity, is more than twice as heavy as the twin Mars Exploration rovers (MERs) combined. That makes car-sized Curiosity too large for the parachute/airbag combo used so successfully by the Pathfinder mission’s Sojourner rover and the two MERs, Spirit and Opportunity. 着陆舱进入火星大气层以后，要先调整重心位置来获得更大的升力，然后释放出一部“飞行吊车”，漫游车就用多根尼龙绳吊在下面。“飞行吊车”启动火箭发动机降低下降速度并控制姿态，最后打开降落伞实施精确着陆。JPL的工程师们 指出，MSL重850千克，大约是前两台火星漫游车重量之和的两倍还多。由于个头太大，已经不适用降落伞+气囊的降落方式了。 “It has to be a propulsive entry, and then it becomes a question of where do you put the propulsion stages,” says Peter Theisinger, MSL project manager at JPL. “Do you put it over the rover or under the rover? I