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World's Largest Nuclear Fusion Rocket Engine Begins Construction
Nuclear fusion propulsion technology has the potential to revolutionize space travel in terms of both speeds and fuel usage. The same kinds of reactions that power the Sun could halve travel times to Mars, or make a journey to Saturn and its moons take just two years rather than eight.
It's incredibly exciting, but not everyone is convinced this is going to work: the tech needs ultra-high temperatures and pressures to function.
To help prove the viability of the technology, the largest ever fusion rocket engine is now being built by Pulsar Fusion in Bletchley, in the UK.
The chamber, some 8 meters (26 feet) long, is scheduled to start firing in 2027.
As you might expect, replicating the Sun inside a rocket isn't easy. At the center of nuclear fusion propulsion is an ultra-hot plasma locked inside an electromagnetic field, and scientists are continuing to figure out how to do this in a stable and safe way.
"The difficulty is learning how to hold and confine the super-hot plasma within an electromagnetic field," says James Lambert, CFO of Pulsar Fusion. "The plasma behaves like a weather system in terms of being incredibly hard to predict using conventional techniques."
Machine learning could help make this box of wild weather a little easy to map. Pulsar Fusion has partnered with Princeton Satellite Systems in the US to use supercomputer algorithms to better predict how the plasma is likely to behave, and how it might be more precisely controlled.
If scientists are able to get everything functioning as intended, temperatures of several hundred million degrees will be reached in the chamber, making it hotter than the Sun. The surplus energy released could potentially drive rocket speeds of 500,000 miles (804,672 kilometers) per hour.
The particular type of engine we're talking about here is a Direct Fusion Drive (DFD), in which the charged particles create thrust directly, rather than converting into electricity. It's more efficient than other options, and as it's powered by atomic isotopes, doesn't need a huge fuel payload.
"You've got to ask yourself, can humanity do fusion?" Pulsar Fusion CEO Richard Dinan told TechCrunch. "If we can't, then all of this is irrelevant."
"If we can – and we can – then fusion propulsion is totally inevitable. It's irresistible to the human evolution of space."
As well as making round trips to planets much shorter, nuclear fusion also promises to provide almost unlimited, clean energy for life here on Earth.
However, scientists think it'll be demonstrated in space first, where the lack of any atmosphere and the ultra-cold temperatures are more conducive to reactions.
注释：
fusion: n
表示"核聚变; 融合；"，means " union of atomic nuclei to form a heavier nucleus, usually with energy being released"，如：Nuclear fusion is the energy source that keeps the sun alive.核聚变是使太阳保持活力的能源。There is now a worrying fusion of information and entertainment. 现在信息和娱乐已经出现令人忧虑的相互融合。
propulsion: n
表示" 推进；推进力"，means "the act of propelling; a propelling force"，如：This aircraft works by jet propulsion. 这架飞机是喷气推进的。
viability: n
表示"可行性"，means "capable of being done in a practical and useful way"，如：And finally I'll discuss the viability of the project. 最后我要谈谈这一项目的可行性。
replicate: v
表示" 复制"，means "make or do or perform again;"，如：Viruses usually replicate at the primary site of the entry. 病毒通常在侵入的位置复制。
plasma: n
表示"等离子体；", 如：His rocket harnesses a nuclear process to produce a hot gas plasma. 他设计的火箭能利用核反应过程产生的一种高温的气态等离子体。
Pulsar: n
表示" 脉冲星"，如：They discovered a new pulsar wake. 他们发现了一个新的脉冲星尾迹。
isotope: n
表示" 同位素"，means "one of two or more atoms with the same atomic number but with different numbers of neutrons"，如：Later he named these separate forms isotopes. 后来他称这些不同的形式为同位素。
inevitable: adj
表示" 不可避免的；必然(发生)的"，means "which cannot be avoided or prevented from happening; certain to happen"，如：You'll have to bow to the inevitable. 你将不得不向不可避免的事态低头。
payload: n
表示" 有效载重；负载；"，means "the front part of a guided missile or rocket or torpedo that carries the nuclear or explosive charge or the chemical or biological agents"，如：The space rocket carries a satellite as a payload. 宇宙火箭运载一个卫星作为其有效载荷。
conducive: adj
表示" 有助的；有益的"，means " likely to produce;helping(an especially desirable result) to happen"，如：Fresh air is conducive to health. 新鲜空气有助于健康。
中文简要说明：
核能分成两类：核分裂(Nuclear Fission)与核聚变(Nuclear Fusion)，相比于现在已被大量应用的核分裂，核聚变的能量更强，残余辐射物质更少，因此被视为「终极能源」。虽然理论上可行，核聚变却还没有实用化，不过一间新创公司打算越级挑战，他们要打造世界最大的核聚变火箭引擎，以测试技术理论。
科学警报(ScienceAlert)报导，假如把核聚变推进技术应用到太空，那么「航向星大海」会比现在要容易与快速，前往火星的时间从9个月减至3个月，前往土星及其卫星的旅程，从8年缩短为2年。
这项技术需要超高的温度和压力才能发挥作用，为了证明该技术的可行性，位于英国布莱奇利(Bletchley )的「脉冲融合」(Pulsar Fusion) 新创公司，正在建造有史以来第一座，也是最大的核聚变火箭发动机，长约8公尺，计划于 2027 年开始点火。
正如物理课本所说，核聚变就是太阳的发光发热原理，想要复制太阳并不容易，因为我们实在没办法有恒星那么大的体积与质量。因此科学家是设想创造出一种比太阳更高温更高压的环境，那是锁定在电磁场内的超热电浆体(plasma，也称等离子体)，电桨体就像流体一样难以捉摸，科学家们正在研究，如何以稳定和安全的方式掌握它们的特性。。
「脉冲融合」公司的财务主管詹姆斯•兰伯特(James Lambert)说：「困难在于学习如何在电磁场内，保持和限制超热的电浆流体，它们的行为就像天气系统，使用传统技术很难预测。」
利用超级计算机与AI学习技术，或许可以帮助我们更容易地绘制出电浆体狂野天气的地图。该公司正在与美国普林斯顿卫星系统合作，使用普林斯顿的超级计算机，试图更好地预测电浆体的可能，以及如何精确地控制。
如果科学家们能够让一切按预料运作，那么引擎腔内的温度将达到数亿度，比太阳表面还要热上3倍。如此高的温度一但释放，其能量可使火箭速度达到每小时 80.4万公里，也就是223.5公里/秒，这速度极为夸张，是第3宇宙速度(飞出太阳系的速度，约16.7公里/秒)的13倍，没几年就能飞出太阳系。
首席执行长理查德丹恩(Richard Dinan)说：「我们必须自问，人类能进行核融合吗？如果我们做不到，那么我们就无法真正前往太空；如果我们能，而且我相信真的可以，那么核聚变火箭是必要的。它对人类进化成太空居民是关键工具。」
不过，目前的核聚变实验都不能长期维持，现在就要做太空火箭是否可行？该公司的科学顾问认为，或许太空才是合适的核融合实验场，太空中缺乏大气层和超冷的温度，更有利于核聚变反应。
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