VOA科学技术2024--Why Is Helium Causing Problems with Spacecraft?

Helium leaks have been a major problem for spacecraft and rockets.

Recent reports about Boeing's Starliner and SpaceX's Polaris Dawn mission have involved problems controlling helium. Recently, the Starliner had a helium leak in a propulsion system. Polaris Dawn also had helium issues on its ground equipment.

Helium leaks have affected¹ past missions including the Indian Space Research Organization's Chandrayaan 2 and the European Space Agency's Ariane 5.

Recently, Reuters news agency explored why spacecraft and rockets use helium, and why it can cause problems:

Why is helium used on spacecraft?

Helium is inert², meaning it does not chemically react with other substances. It also does not burn. Helium's atomic number is 2, making it the second lightest element after hydrogen.

Rockets need to reach exact speeds and altitudes to maintain their orbits. Heavier rockets need more energy to fly and use more fuel. They also require more powerful engines, which are costlier³ to develop, test, and maintain.

Helium has an extremely low boiling point of -268.9 degrees Celsius⁴. This means that it remains⁵ a gas even in extremely cold environments like space. That is an important quality because many rocket fuels are stored at low temperatures.

Helium is not toxic⁶. But it cannot be breathed on its own because it displaces oxygen. Humans need oxygen to live.

How is helium used in rockets?

Because of its special qualities, helium is used to pressurize fuel tanks. It helps ensure fuel flows to the rocket's engines without stopping. Helium is also used for cooling systems.

As fuel and oxidizer are burned in the rocket's engines, helium fills the resulting empty space in the tanks, maintaining the correct pressure inside.

Because it is non-reactive, it can safely mix with other contents in the tanks.

Is helium more likely to leak?

Helium's small atomic size and low molecular⁷ weight mean its atoms can escape through small spaces or seals in storage tanks and fuel systems.

However, because there is very little helium in the Earth's atmosphere, leaks can be easily detected. This makes the gas important for identifying possible problems in a rocket or spacecraft's fuel systems.

In May, hours before Boeing's Starliner spacecraft made its first attempt to launch an astronaut crew, sensors⁸ inside the spacecraft detected a small helium leak. The American space agency NASA spent several days studying the leak before deciding it was low risk.

Additional leaks were detected in space after Starliner launched in June. Such discoveries played a part in NASA's decision to bring Starliner back to Earth without its crew.

As a result, two NASA astronauts who flew to the International Space Station aboard a Starliner capsule will need to return to Earth on a SpaceX vehicle early next year.

The frequency of helium leaks across space-related systems, some engineers say, has shown an industry-wide need for innovation. Innovation is needed in the design of valves and the mechanisms⁹ that tighten¹⁰ them. A valve is a mechanical device that controls the flow of a gas or fluid.

Can another gas be used?

Some rocket scientists have experimented with gases such as argon and nitrogen, which are also inert and can sometimes be less costly¹¹. Helium, however, is much more common in the space industry.

In Europe's new Ariane 6 rocket, designers replaced the helium that was used in the rocket's predecessor¹² Ariane 5. The Ariane 6 has a new pressurization system. The new system changes a small amount of liquid oxygen and hydrogen propellants to gas, which then pressurizes those fluids for the rocket engine.

That system failed in space, however, during the final part of Ariane 6's otherwise successful launch in July. The failure of the new system added to the international rocket industry's list of pressurization difficulties.

Words in This Story

propulsion - n. the act of driving forward or onward¹³

mission -n. a flight by an aircraft or spacecraft which has a specific goal

altitude - n. the vertical¹⁴ elevation¹⁵ of an object above a surface (such as sea level or land)

toxic - adj. containing or being poisonous material

detect -v. to discover or find

frequency -- n. the proportion or percentage of items in a particular category in a set of data

innovation - n. the introduction of something new

predecessor - n. one that precedes or comes before

propellant - n. something that drives forward or onward

1 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

2 inert   

adj.无活动能力的，惰性的；迟钝的

参考例句：

• Inert gas studies are providing valuable information about other planets,too.对惰性气体的研究，也提供了有关其它行星的有价值的资料。
• Elemental nitrogen is a very unreactive and inert material.元素氮是一个十分不活跃的惰性物质。

3 costlier   

adj.昂贵的( costly的比较级 )；代价高的；引起困难的；造成损失的

参考例句：

• Alligator skin is five times more costlier than leather. 鳄鱼皮比通常的皮革要贵5倍。 来自互联网
• Disagreements among creditors can be costlier still. 债权人之间的分歧会加大重组的费用。 来自互联网

4 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

5 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

6 toxic   

adj.有毒的，因中毒引起的

参考例句：

• The factory had accidentally released a quantity of toxic waste into the sea.这家工厂意外泄漏大量有毒废物到海中。
• There is a risk that toxic chemicals might be blasted into the atmosphere.爆炸后有毒化学物质可能会进入大气层。

7 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

8 sensors   

n.传感器，灵敏元件( sensor的名词复数 )

参考例句：

• There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
• Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时，有很大变化。 来自辞典例句

9 mechanisms   

n.机械( mechanism的名词复数 )；机械装置；[生物学] 机制；机械作用

参考例句：

• The research will provide direct insight into molecular mechanisms. 这项研究将使人能够直接地了解分子的机理。 来自《简明英汉词典》
• He explained how the two mechanisms worked. 他解释这两台机械装置是如何工作的。 来自《简明英汉词典》

10 tighten   

v.(使)变紧；(使)绷紧

参考例句：

• Turn the screw to the right to tighten it.向右转动螺钉把它拧紧。
• Some countries tighten monetary policy to avoid inflation.一些国家实行紧缩银根的货币政策，以避免通货膨胀。

11 costly   

adj.昂贵的，价值高的，豪华的

参考例句：

• It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
• This dictionary is very useful,only it is a bit costly.这本词典很有用，左不过贵了些。

12 predecessor   

n.前辈，前任

参考例句：

• It will share the fate of its predecessor.它将遭受与前者同样的命运。
• The new ambassador is more mature than his predecessor.新大使比他的前任更成熟一些。

13 onward   

adj.向前的，前进的；adv.向前，前进，在先

参考例句：

• The Yellow River surges onward like ten thousand horses galloping.黄河以万马奔腾之势滚滚向前。
• He followed in the steps of forerunners and marched onward.他跟随着先辈的足迹前进。

14 vertical   

adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置

参考例句：

• The northern side of the mountain is almost vertical.这座山的北坡几乎是垂直的。
• Vertical air motions are not measured by this system.垂直气流的运动不用这种系统来测量。

15 elevation   

n.高度；海拔；高地；上升；提高

参考例句：

• The house is at an elevation of 2,000 metres.那幢房子位于海拔两千米的高处。
• His elevation to the position of General Manager was announced yesterday.昨天宣布他晋升总经理职位。