英语沙龙全年文本集21 国家应急空中指挥所

21. National Emergency Airborne Command Post The E-4B is designed to provide National Command Authorities (NCA) with a survivable capability to direct and control military forces in all levels of conflict, including nuclear war. Unlike ground-based command sites that are vulnerable to attack, the E-4B has the mobility to escape direct assault. Its communications system is hardened to withstand the massive electromagnetic pulse of a nuclear burst, so that the communication network will function following an enemy attack and enable the NCA to direct a retaliatory1 strike2. As aircraft operations and maintenance are self-contained, operation are possible from a large number of civilian, abandoned or damaged airfields whose number and distribution further increase the E-4B’s survivability. Four General Electric CF6-50E engines give the modified 747-200B a certified maximum take-off gross weight of 362,874 kg. This provides sufficient fuel for the E-4B to remain airborne3 for 12 hours without refueling or 72 hours with in-flight refueling. A 1500 meters runway enables the E-4B to take off with an 8-hour endurance; take-off from shorter runways is possible by further reducing fuel load. Worldwide communication over many links is possible because of the E-4B’s advanced command and control electronics. These are powered by a 1200 Kilowatt4 generator 5 system and include 13 external communication systems operating through 50 antennas6. The ability to access satellite systems reduces ground station dependence and protects against jamming7 and direct tracking attempts. A long range link, established with the high power Very Low Frequency8 (VLF) system, resists atmospheric nuclear effects and is very difficult to jam. 　　The E-4B system is capable of tying with commercial telephone and radio networks and could potentially be used for radio broadcast to the general population. When it is on the ground, it can also be connected to a ground communication network, which can be quickly disconnected. The E-4B accommodates9 up to 94 crew members on three decks with 510m2 of deck space. The upper deck contains the cockpit10 and flight crew rest area for long missions. 国家应急空中指挥所 设计E-4B的目的，是在各种规模的冲突中（包括核战争），为国家指挥当局提供指挥和控制部队的生存能力。 　　不像易受攻击的地面指挥所，E-4B具有躲避直接攻击的机动能力。它的通信系统经过强化，可抵抗核爆炸产生的大量电磁脉冲，因此通信网在遭到敌人核攻击后仍继续运行，使得国家指挥当局能够指挥反击。由于飞机集操作与维修于一体，从大量民用的、废弃或损坏的机场起飞都成为可能，这些机场的数量和分布进一步增强了E4B的生存能力。 4台通用电气公司生产的CF6-50E型发动机，使得改装的747-200B型飞机的 标准 excel标准偏差excel标准偏差函数exl标准差函数国标检验抽样标准表免费下载红头文件格式标准下载 最大起飞总重量为362874公斤。这给E-4B提供了充足的燃料，可在空中飞行12小时无需加油；若在空中加油，则可飞行72小时。一条1500米长的跑道可使E4B起飞，续航8小时。进一步减少燃料负荷后可从更短的跑道起飞。 　　由于E4B装有先进的指挥和控制电子设备，通过许多链路进行全球通信是可能的。这些设备由一个1200千瓦的发电机系统供电，包括13个外部通信系统，通过50副天线来进行工作。 　　能接入卫星系统的能力，减少了它对地面台站的依赖性，并可避免敌方干扰和直接跟踪。用高功率甚低频系统建成的一条远距离链路，可抵抗大气核爆炸效应，且敌人很难干扰。 E-4B系统能与商用电话和无线电网络相连接，并有可能用来对公众进行无线电广播。位于地面时，它也能与地面通信网接通，还能迅速断开。 　　E-4B能在3个总共510平方米的机舱内容纳94名机组人员。上层舱设有驾驶室及远程飞行的机组人员休息室。 1.retaliatory[]adj.以牙还牙的，报复的 2.strike[]n.袭击(尤指空袭) 3.airborne[]adj.在空中的，在飞行的 4.kilowatt[]n.[物]千瓦(特)(略作kw) 5.generator[]n.发电机 6.antenna[]n.[美]天线 7.jam[]vt.[无]干扰 8.frequency[]n.[物]频率 9.accommodate[]vt.容纳，为…提供空间 10.cockpit[]n.(飞行员)座舱