The limits of chemical rocket engines.
限制的化学火箭发动机。
The spacecraft, with its nuclear rockets, would be launched on top of a conventional chemical rocket.
带有核燃料火箭的宇宙飞船可在普通化学燃料火箭上发射。
Once in space, ion engines steadily propel a spacecraft until it travels faster than it would have using a chemical rocket.
一旦进入太空，离子发动机将稳步推进航天器，最终达到的速度会比使用普通火箭的更高。
The exhaust velocity, though, is enormous—more than ten times that of a chemical rocket—and this makes ion propulsion extremely efficient.
但其排气速度却异常惊人，大约为化学燃料火箭的十倍—这使得离子推进器的效率非常高。
Then, once the vehicle had ascended to high-Earth orbit, above about 800 kilometers, the nuclear reactor module would detach from the chemical rocket and start up.
这样，当普通燃料火箭到达地球轨道约800公里高度时，核反应堆舱会脱离化学燃料火箭，并开始工作。
In technical terms, chemical rockets have low maximum velocity growth, which means that their exhaust velocities are not high enough to impart very high speeds to the rocket.
从技术上讲，化学燃料火箭的最大速度增长比较低。这就是说，它们的排气速度还不足以将火箭的速度增加到非常快的程度。
One might think that fusion propulsion requires some exotic fuel to propel a rocket a million-or-so-times more energetically than standard chemical fuels.
有人可能会认为聚变推进需要一些能量高于标准的化学燃料一百多万倍的稀有燃料推进一个火箭。
So far NASA is exploring two options for propulsion there? A nuclear thermal rocket and a chemical engine.
迄今为止NASA研究了两种前往那里的备选推进器：核热火箭和化学发动机。
It thus needs to carry less fuel than a rocket, and no chemical oxidant to burn that fuel, as a rocket would.
这种火箭需要携带的燃料也减少了，并且不需要化学氧化剂。
Scientists at the Centers for Disease Control and Prevention tested the formula for the presence of perchlorate, a chemical used as the main ingredient in solid rocket fuel.
疾病预防控制中心的科学家专门针对高氯酸盐对配方奶进行了检测。
By comparison, the chemical power generated by a rocket equals one half the thrust times the exhaust velocity.
相比之下，火箭的化学能功率是推进力的一半乘以排气速度。
By comparison, the chemical power generated by a rocket equals one half the thrust times the exhaust velocity.
相比之下，火箭的化学能功率是推进力的一半乘以排气速度。
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