Robert Frost 在quora上有关航天的回答收集(五)

为什么航天飞机引擎的声音从地面听起来听起来像是爆米花或者小型而快速的爆炸呢?Why do the space shuttle engines sound like loud popcorn or small rapid explosions from the ground?

The Space Shuttle, during launch, was as loud as an undistorted sound can possibly be in Earth’s atmosphere – 194 dB.

航天飞机在发射时的声音,就像地球大气中未失真的声音一样大-194 dB。

A sound is produced when air molecules are vibrated back and forth, producing a wave of alternating higher pressure and lower pressure regions. At 194 dB, the low pressure region is a vacuum and can’t get lower, so the amplitude of the wave is capped.

当空气分子来回振动时会产生声音,从而产生一波交替交替的高压和低压区域。 194 dB处的低压区域是真空状态,不会降低,因此波的幅度受到限制。

That is why it sounded like a crackle and not a smooth roar. The sound wave produced by the Space Shuttle had an amplitude greater than the atmospheric pressure limit, resulting in the wave being clipped at 194 dB.

这就是为什么它听起来像啪啪声,而不是平稳的轰鸣声。 航天飞机产生的声波的振幅大于大气压力极限,导致该波被限制在194 dB。

In addition, there were also multiple supersonic flows interacting with each other.

另外,还有多个超声速流互相作用。

@ Andrew Karam

I was able to see two Shuttle launches, both in 1982 – from 14 miles (the first one) and 3 miles (the second). Even at 14 miles we could clearly hear the engines – including the popping. And at 3 miles, it was a whole-body experience. We were engulfed in the roar, and I swear I could feel my internal organs shaking as well. It was the single most impressive thing I have experienced.

我看过两次航天飞机发射,都是在1982年,分别在14英里(第一次)和3英里(第二次)处。 即使在14英里处,我们也可以清楚地听到引擎声音,包括爆裂声。 在3英里处,这是一次全身心的体验。 我们被怒吼所吞没,我发誓我也能感觉到我的内脏也在颤抖。 这是我经历过的最令人印象深刻的事情。

答主答:

Great photo!

如何向国际空间站供水? 是从地表运输普通水,还在空间站上使用氢和氧合成的?How is water supplied to the International Space Station? Is it in form of regular water or do they synthesise using hydrogen and oxygen?

The ISS has a regenerative water system. Urine and sweat and condensation are recycled and used as potable water. This greatly reduces the water transportation to the ISS, but no system is 100% efficient, so water is still transported to the ISS.

ISS拥有高效的再生水系统。 尿液,汗液和冷凝水被回收并用作饮用水。 这极大地减少了将水输送到ISS的过程,但是没有一个系统能100%地回收,因此仍需要将水输送到ISS。

American water is transported in CWCs (Contingency Water Carriers). These are Nomex bags with combitherm bladders. They can be sent up in any of the commercial cargo vehicles and in the Japanese HTV cargo vehicle.

美国的水以CWC(应急水运工具)运输。 这些是带有组合气囊的Nomex袋。 它们可以在任何商用货运载具和日本HTV货运载具中发送。

Russian water is transported via two different mechanisms. There are water tanks in the Progress cargo vehicle. There are also metal canisters, called EДВ. Within the Russian service module there are tanks called Rodnik that hold a 45-day contingency supply. Water for nominal use usually comes from EДВ.

俄罗斯的水是通过两种不同的机制输送的。 Progress货运载具中有水箱。 还有一些金属罐,称为EДВ。 在俄罗斯的服务模块中,有一个名为Rodnik的水箱,可以容纳45天的应急供应。 名义上使用的水通常来自EДВ。

The amount of water carried depends on the level of the supply onboard the ISS and on the available cargo mass in the cargo vehicle.

运载的水量取决于国际空间站上的供水量以及货运载具中可用的货物质量。

国际空间站上的人们是如何庆祝圣诞节的?How do people celebrate Christmas at the International Space Station?

The crew planning schedule accommodates eight holidays per year, so the crew will get together and review the list of observable holidays and select four for their six month increment. The list includes holidays from America, Russia, Europe, Japan, and Canada. That means the crew might have two Christmases – the December 25th celebrated by America, Europe, and Canada and the January 7th Orthodox Christmas celebrated by the Russians.

机组计划时间表每年有8个假日,因此机组将聚在一起并查看可以的假期列表,并选择4个假日个作为六个月中的休闲时间。 该假日列表包括来自美国,俄罗斯,欧洲,日本和加拿大的假期。 这意味着机组人员可能有两个圣诞节–美国,欧洲和加拿大庆祝12月25日,俄罗斯人庆祝1月7日东正教圣诞节。

On the selected holidays, the ground tries as hard as possible to not schedule the crew for many tasks. It’s a rare chance for the crew to relax and celebrate.

在选定的假期中,地面人员会尽力不安排船员执行许多任务。 这是船员们放松和庆祝的难得机会。

They have a few decorations they can put out, including a tiny Christmas tree and stockings.

他们可以摆出一些装饰品,包括一棵小圣诞树和长袜。

If a cargo vehicle recently arrived, there might even be a few small gifts for the crew.

如果最近有一辆货运载具抵达,甚至可能会给船员一些小礼物。

They will obviously take advantage of the ISS communication assets to video-conference or telephone with their families and then they’ll eat Christmas dinner together, and maybe sing some Christmas carols, and/or watch a Christmas videos uplinked to them by the ground.

他们显然将会利用ISS的通讯资源与家人进行视频会议或电话,然后他们将一起吃圣诞大餐,也许会唱一些圣诞颂歌,和/或观看地面上传给他们的圣诞视频。

为什么STS(航天飞机)使用28V DC电源而不是更“标准”的12 / 24V DC?Why did the STS (space shuttle) use 28V DC power rather than 12/24V DC which is more “standard”?

What you are observing is not really a physical difference, it’s just different conventions for defining the system. Aircraft often do use 24-volt batteries. They use 28-volt generators, though. We want the generator to produce excess voltage that can be used to keep the battery charged. Similarly, for a 12-volt battery, a 14-volt generator would be typical.

您所观察到的实际上并不是物理上的差异,只是定义系统的不同约定。 飞机经常使用24伏电池。 他们使用28伏发电机。 我们希望发电机产生可用于保持电池充电的多余电压。 类似地,对于12伏电池,通常是14伏发电机。

Aviation tends to define the system based on generator voltage while other industries, such as automotive, tend to define the system based on battery voltage. Your 12-volt car battery is probably connected to an alternator putting out 14-volts.

航空倾向于基于发电机电压来定义系统,而其他行业(例如汽车)倾向于基于电池电压来定义系统。 您的12伏汽车电池可能已连接到输出14伏的交流发电机。

As for why 28-volt instead of 14-volt – there are a few reasons. One is that higher voltage means smaller wires can be used, saving weight and thus fuel. Another is that during early days, someone came up with a really good and light 28-volt generator that worked well with other aviation equipment and it became common and then a standard,

至于为什么用28伏而不是14伏的原因,有几个原因。 一种是较高的电压意味着可以使用较小的电线,从而减轻了重量,从而节省了燃料。 另一个原因是,在早期,有人想出了一种非常轻巧的28伏发电机,该发电机可以与其他航空设备很好地配合使用,后来成为一种普遍的标准。

我们可以通过望远镜看到宇航员在国际空间站上工作吗?Can we see astronauts working on the ISS through a telescope?

Yes, with some effort and luck.  In 2009, a Dutch astronomer named Ralf Vandebergh managed to capture an image of astronaut Joe Acaba, working outside the ISS.  Vandebergh accomplished this using a ten inch (25.4 cm) reflector telescope with an attached video camera.

是的,有些努力和运气。 2009年,一位名叫拉尔夫·范德伯格(Ralf Vandebergh)的荷兰天文学家成功拍摄了在国际空间站外工作的宇航员乔·阿卡巴(Joe Acaba)的照片。 Vandebergh使用带有连接摄像机的十英寸(25.4厘米)反射镜望远镜实现了这一目标。

Here is one of the images he captured.

这是他拍摄的一张照片。

And in 2011, British amateur astronomer Martin Lewis managed to capture astronaut Steve Bowen during an EVA while the Space Shuttle was docked.  Martin used an 8.75 inch (22.2 cm) reflector telescope.

2011年,英国业余天文学家马丁·刘易斯(Martin Lewis)设法在航天飞机停泊期间捕获了宇航员史蒂夫·鲍恩(Steve Bowen)。 马丁使用了8.75英寸(22.2厘米)反射镜望远镜。

Here is his image.

And here is an image from astrophotgrapher Thierry Legault, also showing Steve Bowen.  Legault also used a 10 inch reflector.  Legault is well known for the amazing pictures he has captured of the ISS.

这是来自天文摄影师Thierry Legault的图像,也拍到了Steve Bowen。 Legault也使用了10英寸反射镜。 Legault 以他为国际空间站拍摄的惊人照片而闻名。

【译注:NASA提供了追踪空间站的信息,还可以把空间站经过你所在地上空时的时间以邮件形式提醒你。不过好像只能选择美国的地区。 https://spotthestation.nasa.gov/

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