《那些古怪又讓人憂心的問題》第35期:牛排墜落(3)

For the sake of this simulation, I assume that at lower speeds some type of vortex shedding creates a flipping tumble, while at hypersonic speeds it's squished into a semi-stable spheroid shape. However, this is little more than a wild guess. If anyone puts a steak in a hypersonic wind tunnel to get better data on this, please, send me the video. If you drop the steak from 250 kilometers, things start to heat up; 250 kilometers puts us in the range of low Earth orbit. However, the steak, since it's dropped from a standstill, isn't moving nearly as fast as an object reentering from orbit. In this scenario, the steak reaches a top speed of Mach 6, and the outer surface may even get pleasantly seared. The inside, unfortunately, is still uncooked. Unless, that is, it goes into a hypersonic tumble and explodes into chunks. From higher Altitudes, the heat starts to get really substantial. The shockwave in front of the steak reaches thousands of degrees (Fahrenheit or Celsius; it's true in both). The problem with this level of heat is that it burns the surface layer completely, converting it to little more than carbon. That is, it becomes charred. Charring is a normal consequence of dropping meat in a fire. The problem with charring meat at hypersonic speeds is that the charred layer doesn't have much structural integrity, and is blasted off by the wind-exposing a new layer to be charred. (If the heat is high enough, it will simply blast the surface layer off as it flash-cooks it. This is referred to in the ICBM papers as the “ablation zone.”) Even from those heights, the steak still doesn't spend enough time in the heat to get cooked all the way through. We can try higher and higher speeds, and we might lengthen the exposure time via dropping it at an angle, from orbit.

在我進行模擬的過程中，我假設在低速下某些類型的渦流脫落會使牛排翻來覆去，而在高超音速下，牛排則會被擠壓成半穩定態的橢球狀。但這也只是我的大膽猜想，如果有人真的在高超音速風洞中放入了一塊牛排以取得更準確的數據，請一定把視頻發給我。如果你從250千米的高度釋放牛排，牛排能達到的溫度就更高了。250千米的高度已經在低地球軌道的範圍裏了，不過由於牛排是從靜止開始下落，因而速度比不上那些脫離軌道再進入大氣層的物體。在這種情況下，牛排的最高速度能夠達到6馬赫，這時牛排的外表面可能焦得恰到好處。但很不幸，內部仍然是生的，除非牛排在高超音速下猛地顛簸了一下炸成了碎片。如果從更高的地方落下，熱量就會變得相當可觀。牛排前方的激波將會達到數千度（反正不管用攝氏度還是華氏度都有幾千度），這時牛排的表層會被徹底烤成焦炭。把肉扔到火裏的一個正常後果就是變成焦炭。但高超音速的焦肉面臨一個問題：被燒成焦炭的肉並沒有多少結構強度，因而會被狂風吹走，使得更深一層的肉被燒焦。（如果熱量足夠高，牛排的表面會在被剝離的瞬間被烤熟，這個速度區域在彈道導彈論文中被稱爲“剝蝕區”。）即使在這麼高的高度下，牛排所受的高溫時間仍然不足以把整塊肉從裏到外都烤熟。3我們可以嘗試更高的高度和更快的速度，我們甚至可以通過從軌道以一定角度扔下去以增加暴露在高溫下的時間。

But if the temperature is high enough or the burn time long enough, the steak will slowly disintegrate as the outer layer is repeatedly charred and blasted off. If most of the steak makes it to the ground, the inside will still be raw. Which is why we should drop the steak over Pittsburgh.

但當溫度高到一定程度，或者燒蝕的時間長到一定程度後，整塊牛排就會慢慢解體，因爲牛排的外層不斷地被燒焦並被狂風剝離。如果大部分牛排能夠堅持到最後落到地上，內部仍將會是生的。這也是爲什麼我們要在匹茲堡上空扔牛排。

As the probably apocryphal story goes, steelworkers in Pittsburgh would cook steaks by slapping them on the glowing metal surfaces coming out of the foundry, searing the outside while leaving the inside raw. This is, supposedly, the origin of the term “Pittsburgh Rare.”

有這麼一個流傳的故事，說的是匹茲堡的鋼鐵工人喜歡把牛排摔到剛出爐還在熾熱發光的金屬表面，把牛排的外層烤熟，但內部仍然保持生的狀態。這大概就是“匹茲堡生牛排”的來歷。

So drop your steak from a suborbital rocket, send out a collection team to recover it, brush it off, reheat it, cut away any badly charred sections, and dig in.

所以從一個亞軌道火箭上把牛排扔下來，並派出一支回收小隊把它找回來，擦乾淨，再加熱一下，去掉燒焦的部分，然後就可以開吃啦。

Just watch out for salmonella. And the Andromeda Strain.

要小心沙門氏菌，以及《天外來菌》哦。

1 I mean, intact. Not necessarily fine to eat.

1．我是說，看着沒事兒，吃了不一定沒事兒。

2 I know what some of you are probably thinking, and the answer is no - it doesn't spend enough time in the Van Allen belts to be sterilized by radiation.

2．我知道你們一些人在想什麼，答案是不行——它在範艾倫輻射帶裏待的時間不夠長，不足以通過輻射來消毒。