The feature that makes the Starship so well-suited for this job is, of course, its incredible power.

星際飛船之所以能勝任這項工作，當然是因為它擁有驚人的動力。

There's no doubt that a future Starship will have more than enough muscle to send both crews and massive amounts of supplies on their path towards Mars.

毫無疑問，未來的星際飛船將有足夠的能力將船員和大量物資送往火星。

Going up is one thing, but what about coming back down on the Martian surface?

上天是一回事，但回到火星表面怎麼辦？

We are talking about the most complicated maneuver of the entire journey, the make or break moment, and there's a lot more involved in figuring it out than you might think.

我們談論的是整個旅程中最複雜的操作，是決定成敗的時刻，要想弄明白它，涉及的東西比你想象的要多得多。

This is how the SpaceX Starship will land on Mars.

這就是 SpaceX 星際飛船登陸火星的方式。

Let's establish right now that we are not all rocket scientists or physicists.

讓我們現在就確定，我們並不都是火箭科學家或物理學家。

I'm definitely neither of those things, but luckily, we do not need to be geniuses to understand the basic principles behind interplanetary travel.

但幸運的是，我們不需要成為天才，也能理解星際旅行背後的基本原理。

So we're going to keep this all at a very accessible level.

是以，我們將把這一切保持在非常容易理解的水準上。

Before we can talk about landing on Mars, we need to know how the Starship got there in the first place.

在討論登陸火星之前，我們首先要知道星際飛船是如何到達火星的。

The thing that we always have to remember about space travel is that everything is always in motion, and within the context of a solar system, everything is moving in an orbit around the sun.

關於太空旅行，我們始終要記住的一點是，萬物總是在運動的，而在太陽系中，萬物都在圍繞太陽的軌道上運動。

We are currently held in the gravity well of the sun, and the only thing that prevents us from falling down any deeper is the orbital velocity of the Earth, which is approximately 30 km per second.

我們目前被困在太陽的引力井中，唯一能阻止我們往下掉得更深的是地球的軌道速度，大約為每秒 30 公里。

That's how fast we are traveling right now in a big circle around a star that takes 365 days to complete.

這就是我們現在繞恆星轉一大圈的速度，365 天才能轉完。

Mars is further away from the sun than the Earth, meaning that it isn't as far down into the gravity well as we are, and therefore Mars can travel at a slower orbital velocity without falling in, so Mars orbits the sun at around 24 km per second.

火星距離太陽比地球更遠，這意味著它不像我們一樣處於重力井的下方，是以火星可以以較慢的軌道速度運行而不會掉入重力井中，所以火星以每秒約 24 公里的速度繞太陽運行。

Now if we want to leave the Earth in a spaceship and explore the planets, we will become yet another object spinning around in the gravity well of the sun, and just like the planet

現在，如果我們想乘坐飛船離開地球去探索行星，我們將成為在太陽引力井中旋轉的另一個物體，就像行星一樣

Earth, if we were to slow down our orbital velocity, we would start to fall into that gravity well.

在地球上，如果我們減慢軌道速度，我們就會開始墜入重力井。

This will change our orbit in the direction of an inner planet like Venus, and by the same mechanics, if our spaceship starts moving faster than the planet Earth, we will rise up the gravity well, bringing our orbit towards an outer planet like Mars.

根據同樣的力學原理，如果我們的飛船開始以比地球更快的速度移動，我們的重力井就會上升，使我們的軌道向火星等外行星的方向移動。

So traveling through the solar system is all about changing your velocity relative to your starting point.

是以，穿越太陽系就是改變你相對於起點的速度。

The technical term that we use to describe this is delta-v, where delta means change and v means velocity.

我們使用的專業術語是 delta-v，其中 delta 表示變化，v 表示速度。

We typically measure delta-v in km per second, so if the Earth is moving at 30 km per second and you accelerate your spaceship to 31 km per second, you have a delta-v of 1.

我們通常以每秒千米為組織、部門來測量 delta-v，是以，如果地球以每秒 30 千米的速度運動，而你將飛船加速到每秒 31 千米，那麼你的 delta-v 為 1。

By the same measure, if you decelerate your spaceship relative to the Earth and travel at 29 km per second, you also have a delta-v of 1.

同樣，如果你的飛船相對於地球減速，以每秒 29 千米的速度飛行，你的 delta-v 也是 1。

And yet if you blast off from the surface of the Earth at 1 km per second, you are not going to begin rising up through the solar system, you aren't going to rise up above the Earth's surface because gravity and atmospheric drag are holding you down.

然而，如果你以每秒 1 千米的速度從地球表面起飛，你並不會開始在太陽系中上升，你也不會上升到地球表面以上，因為重力和大氣阻力會把你壓住。

These natural forces will affect the amount of delta-v required to maneuver the spaceship.

這些自然力將影響操縱飛船所需的 delta-V 量。

This is why it's so hard to get from the surface of the Earth to outer space.

這就是為什麼從地球表面進入外太空如此困難。

The delta-v required to reach a typical low Earth orbit is going to be around 9.4 km per second.

到達典型低地球軌道所需的 delta-v 約為每秒 9.4 公里。

That's a lot of acceleration, and that's why our starship requires the massive power of the super-heavy booster at launch.

這是一個很大的加速度，這就是為什麼我們的星艦在發射時需要超重型推進器的巨大動力。

This is also why the starship needs to stop for a refilling session in Earth orbit before it can continue on to Mars, because we're going to need a lot more delta-v to complete this journey in order to change velocity, we need propulsion, and propulsion needs fuel.

這也是為什麼星際飛船需要在地球軌道上停下來補充燃料，然後才能繼續前往火星，因為我們需要更多的 delta-v 來完成這次旅程，以便改變速度，我們需要推進力，而推進力需要燃料。

The advantage of filling up in orbit is that it resets our starting point.

在軌道上加註的好處是可以重設我們的起點。

From here, we only need another 9.5 km per second of delta-v to reach the surface of

從這裡出發，我們只需要再以每秒 9.5 千米的三角飛行速度到達

Mars, so basically equal to the change required just to escape the Earth's atmosphere.

火星，所以基本上等於逃離地球大氣層所需的變化。

But there is going to be a big difference in the approach we take for the next leg of the journey, because while escaping the Earth was all about speeding up, landing on Mars is going to require a lot of slowing down, and this can be just as difficult to achieve.

但是，在下一段旅程中，我們所採取的方法會有很大不同，因為逃離地球需要加快速度，而登陸火星則需要放慢速度，這可能同樣難以實現。

A fully-fueled starship in low Earth orbit is imagined to have enough thrust for somewhere between 6 and 7 km per second of delta-v.

據設想，一艘在低地球軌道上充滿燃料的星際飛船的推力足以達到每秒 6 到 7 千米的 delta-v。

This obviously is a bit short of our 9.5 km per second necessary to reach Mars, but that's okay, because the same forces that made it so difficult to escape Earth's atmosphere – gravity and aerodynamic drag – are going to work to our advantage when we come in for a landing, effectively increasing the delta-v potential of our starship.

這顯然比我們到達火星所需的每秒 9.5 公里的速度差了一點，但沒關係，因為使我們難以逃離地球大氣層的同樣的力量--重力和空氣阻力--將在我們著陸時對我們有利，有效地增加我們星際飛船的 delta-v 潛能。

So here's how it's going to go down.

所以，接下來就這麼辦。

Okay, we are in orbit around the Earth, but even a few hundred kilometers above the surface we are still firmly caught in the Earth's gravity well.

好吧，我們是在環繞地球的軌道上，但即使在離地表幾百公里的地方，我們仍然牢牢地被地球的引力井所吸引。

The only thing keeping us up right now is velocity.

現在唯一能支撐我們的就是速度。

If the starship were to slow down at all, it would start falling back towards the Earth.

如果星際飛船稍有減速，就會開始向地球后方墜落。

By that same reasoning, if we do the opposite and speed up, then we will continue to rise up into space.

根據同樣的推理，如果我們反其道而行之，加快速度，那麼我們將繼續向太空上升。

Because we are still so close to the Earth, we need a lot of delta-v to fight against gravity.

因為我們離地球還很近，所以我們需要很大的 delta-v 來對抗重力。

The ship will have to accelerate by 2.44 km per second just to reach a height of geostationary orbit.

飛船必須以每秒 2.44 公里的速度加速，才能到達地球靜止軌道的高度。

Another 0.68 gets us to the height of the Moon.

再加 0.68，就到了月球的高度。

Up here we are finally on the edge of the Earth's gravity well.

我們終於來到了地球引力井的邊緣。

The force of gravity is infinite, but the power of attraction dissipates relatively quickly as you move further away.

萬有引力是無窮的，但隨著距離的拉遠，吸引力會相對較快地消散。

Now all we need is another 0.9 km per second of velocity to escape the Earth's influence completely.

現在，我們只需要每秒再增加 0.9 公里的速度，就能完全擺脫地球的影響。

From this point, floating in the vacuum of space far beyond the Moon, we only require 0.39 m per second of delta-v to achieve our Earth-to-Mars transfer velocity.

從這一點出發，漂浮在月球之外的真空太空中，我們只需要每秒 0.39 米的德爾塔-v 就能達到地球到火星的轉移速度。

This second leg of the journey has used up 3.6 km per second of delta-v, which is at least half of the potential energy in our starship, if not more, and that means that we do not have enough fuel left to successfully land on Mars with engines alone.

這第二段旅程已經耗盡了每秒 3.6 千米的 delta-v，這至少是我們星際飛船潛在能量的一半，甚至更多，這意味著我們沒有足夠的燃料僅靠發動機成功登陸火星。

And here comes the problem that we need to solve.

這就是我們需要解決的問題。

All of the velocity that we acquired to escape Earth's atmosphere and gravity well has got us traveling around the Sun at a significantly higher speed than the planet Earth, which was already traveling at 30 km per second to begin with.

我們為逃離地球大氣層和重力井而獲得的所有速度讓我們以比地球高得多的速度繞著太陽飛行，而地球一開始的速度就已經是每秒 30 公里。

The planet Mars, on the other hand, is orbiting at a speed of just 24 km per second.

而火星的軌道運行速度僅為每秒 24 公里。

So we are moving significantly faster than our target planet, which means that we are going to overshoot the planet Mars and end up stuck somewhere in the asteroid belt unless we start slowing down.

是以，我們的移動速度明顯快於我們的目標行星，這意味著除非我們開始減速，否則我們將越過火星，最終被困在小行星帶的某個地方。

After several months of coasting through the vacuum of space, we need to execute our first deceleration burn.

在真空太空中滑行數月後，我們需要執行第一次減速燃燒。

After flipping the starship around and getting the Raptor engines back up to speed, we have to shave off 0.67 km per second of velocity in order to become captured in the gravity well of Mars.

翻轉星艦，讓猛禽引擎恢復速度後，我們必須每秒減少 0.67 千米的速度，才能被火星引力井捕獲。

This is the first step in what's about to become a very rough ride.

這是即將開始的艱難旅程的第一步。

If we burn off another 0.34 km per second of velocity, then we reach the height of the outer moon Deimos.

如果我們每秒再消耗掉 0.34 千米的速度，那麼我們就到達了外層衛星狄莫斯的高度。

0.4 km per second of further delta-v gets us down to the inner moon Phobos.

每秒 0.4 千米的進一步 delta-v 使我們到達內衛星火衛一。

Here's where things get really tricky.

這就是事情變得棘手的地方。

By slowing down this much, we've already expended over 5 km per second of the potential delta-v in our fuel tanks, and that leaves us with somewhere between 1 and 2 remaining, so we need at least another 4.5 km per second of delta-v to safely reach the surface.

在如此減速的情況下，我們已經消耗了燃料箱中每秒超過 5 千米的潛在 delta-v，剩下的大約只有 1 到 2 千米，所以我們至少還需要每秒 4.5 千米的 delta-v，才能安全到達地面。

In theory, this is still possible as long as we are very strategic about how we use our last bit of fuel, and it's important to remember that everything from here on out is purely speculative.

從理論上講，只要我們有策略地使用最後一點燃料，這還是有可能實現的，但重要的是要記住，從現在開始的一切都純屬猜測。

This is our interpretation of the most logistically feasible Mars landing.

這就是我們對登陸火星在邏輯上最可行的詮釋。

If we want to conserve as much fuel as possible for our landing burn, then we need to take advantage of some external forces to slow our ship down to a reasonable velocity.

如果我們想為著陸燃燒節省儘可能多的燃料，那麼我們就需要利用一些外力將飛船減速到一個合理的速度。

Getting down into a circular low Mars orbit would use up most of our remaining fuel, so we probably shouldn't do that.

進入環形低火星軌道會耗盡我們剩餘的大部分燃料，所以我們可能不應該這麼做。

In this case, we might be better served by inserting the ship into an elliptical orbit, so instead of flying in a circle, we're moving in an oval pattern with a low spot, or perigee, close to the planet and a high spot, or apogee, deeper out into space.

在這種情況下，我們最好把飛船放入一個橢圓軌道，這樣我們就不會在一個圓圈內飛行，而是以一個橢圓形的模式移動，低點或近地點靠近行星，高點或遠地點深入太空。

By using this maneuver, we can start to take advantage of both aerodynamic drag and Mars gravity to help us slow down.

通過這種機動，我們可以開始利用空氣阻力和火星引力來幫助我們減速。

The Mars atmosphere is still very thin, but we'll take any help that we can get.

火星大氣層仍然非常稀薄，但我們會接受一切可能的幫助。

We can lower the perigee of our orbit down to the point where the ship actually dips into the upper atmosphere of the planet.

我們可以將軌道的近地點降低到飛船實際進入行星上層大氣的位置。

By doing this very carefully, we can actually catch some atmospheric drag and lose a small amount of velocity before getting flung back out to our apogee, where, if we've done this properly, the gravity of Mars will pull us back in to repeat the process over again.

如果操作得當，火星的引力會將我們拉回火星，再次重複這一過程。

Every time that we dip into the atmosphere, we gain a little more of that precious delta

我們每進入大氣層一次，就能多獲得一點寶貴的三角洲資源

V bringing us closer to the velocity we need for a soft touchdown on the planet's surface.

V，使我們更接近在地球表面軟著陸所需的速度。

But we can't keep this maneuver up indefinitely, eventually we need to transition from a shallow dip to a full-on dive through the Martian atmosphere.

但我們不能無限期地保持這種機動，最終我們需要從淺浸過渡到完全潛入火星大氣層。

It's actually pretty difficult to achieve a landing trajectory for Mars because the planet is only around half the size of the Earth.

實際上，火星的著陸軌道很難實現，因為火星只有地球的一半大小。

That means the angle of attack necessary to get down below the sky is pretty steep.

這就意味著，要下降到天空以下，所需的攻擊角是相當陡峭的。

This means you need a lot of energy pushing the vehicle down in order to prevent it from skipping off and shooting back up into space.

這意味著你需要大量的能量將飛行器向下推，以防止它跳出並重新射入太空。

Again, we want to save our engines until the last possible moment, so that force to push the ship down deeper into the atmosphere needs to come from somewhere else.

同樣，我們想把引擎保存到最後一刻，所以把飛船推向大氣層深處的力量需要來自其他地方。

This is why the original SpaceX designed for an interplanetary transport system, in 2016, had an aerodynamic lifting body in the upper stage.

這就是為什麼 SpaceX 在 2016 年為星際運輸系統設計的最初方案中，在末級採用了空氣動力升力體。

Starship is much smaller than ITS, so it doesn't need as much aerodynamic force, but the methodology is still pretty much the same.

星際飛船比 ITS 小得多，所以不需要那麼大的空氣動力，但方法還是差不多的。

On its final approach, Starship is actually going to flip over and come into the atmosphere upside down.

在最後接近時，"星際飛船 "實際上會翻轉，倒著進入大氣層。

So that's with the belly and tail pointed up and the nose pointed down.

這就是肚子和尾巴朝上、鼻子朝下的樣子。

This way the lift generated by the body is going to push the vehicle towards the surface on a steeper angle to achieve entry.

這樣，車身產生的升力就會以更陡的角度將車輛推向路面，從而實現入水。

We're also going to start losing a lot of velocity thanks to aerodynamic drag.

由於空氣阻力，我們的速度也會開始大幅下降。

Once the angle of attack is set, the Starship is going to flip around into the more traditional belly flop maneuver that we've seen on Earth.

一旦設定好攻擊角度，星際飛船就會翻轉，做出我們在地球上看到的更傳統的腹部翻轉動作。

This is all about creating the maximum amount of drag that is physically possible and getting the velocity down, but this force can only accomplish so much.

這就是要在物理條件允許的情況下產生最大阻力，並降低速度。

The maximum speed of a freefall is something that we call terminal velocity.

自由落體的最大速度我們稱之為終端速度。

Imagine you jump into a bottomless hole.

想象一下，你跳進了一個無底洞。

Your body will accelerate as you fall up until a certain point when the drag and buoyancy of your body equalizes with the force of gravity and your speed becomes constant.

你的身體會隨著下落而加速，直到某個時刻，你身體的阻力和浮力與重力相等，你的速度才會保持不變。

One way that we cheat terminal velocity is by using a parachute.

我們欺騙末端速度的一種方法是使用降落傘。

This greatly increases drag and slows down our terminal velocity.

這大大增加了阻力，減慢了我們的末端速度。

Starship isn't going to use parachutes, so there's going to come a point where the aerodynamic drag of the vehicle has done all that it's going to do and we reach terminal velocity.

星際飛船不會使用降落傘，所以會有這樣一個時刻，即飛行器的空氣阻力已經完成了它要做的一切，我們達到了末端速度。

Due to the thinner atmosphere, terminal velocity on Mars is around 5 times faster than on Earth.

由於大氣層較薄，火星上的末端速度約為地球上的 5 倍。

In other words, that means you only get 1 fifth the delta-v accomplished by belly flopping through the air on Mars compared to what we've already seen Starship do on Earth, which means that it's going to require more engine power to land on Mars than it does on Earth.

換句話說，與我們在地球上看到的 "星際飛船 "在火星上的表現相比，在火星上的空中翻滾只能獲得五分之一的 delta-v，這意味著在火星上著陸需要比在地球上更大的發動機功率。

This is why fuel is such a major concern here.

這就是為什麼燃料在這裡如此重要。

Assuming that everything up until this point has gone correctly, the Starship's engines will fire up one last time and flip the tail towards the surface, at which point the fuel in the rocket's header tanks will provide just enough delta-v to bring our ship perfectly in sync with the surface of Mars and we touch down...softly.

假定在此之前一切順利，星際飛船的引擎將最後一次點火，並將尾部翻轉至火星表面，此時火箭頭部燃料箱中的燃料將提供足夠的ΔV，使我們的飛船與火星表面完全同步，然後我們......輕輕地著陸。

Now that's a lot of stuff that has to go right, and there is zero margin for error.

現在，有很多事情都要做對，不容有失。

You either score 100% on the exam or you die.

要麼考 100 分，要麼死。

So by knowing all of that, we can appreciate that landing on Mars is going to be incredibly difficult in a massive vehicle like the Starship.

是以，瞭解了這一切，我們就能明白，要想乘坐像 "星際飛船 "這樣的大型飛行器登陸火星，難度可想而知。

It's much easier for NASA to land smaller and lighter vehicles on Mars because the potential delta-v of your fuel is determined by the mass of the vehicle and the efficiency of the engine.

對於美國國家航空航天局來說，在火星上著陸體積更小、重量更輕的飛行器要容易得多，因為飛行器的品質和發動機的效率決定了燃料的潛在δ-v。

So one pound of fuel accomplishes more change in velocity for a lighter ship than it does for a heavier ship, and there is a limit on the amount of fuel that we can bring to Mars.

是以，對於較輕的飛船來說，一磅燃料帶來的速度變化要大於較重的飛船。

Starship would be much easier to land on Mars if it were lighter, but SpaceX needs it to be so gigantic to accomplish the goal that Elon Musk has set out, which is building a self-sustaining city of 1 million people on Mars.

如果 "星際飛船 "更輕，登陸火星就會容易得多，但 SpaceX 需要它如此巨大，才能實現埃隆-馬斯克設定的目標，即在火星上建造一座可容納 100 萬人的自給自足的城市。

SpaceX is working hard on increasing the delta-v of the Starship.

SpaceX 正在努力提高 "星際飛船 "的 delta-v。

They want to make Starship V2 longer with bigger fuel tanks while also making it lighter at the same time and adding three more Raptor vacuum engines.

他們希望星艦 V2 的長度更長，燃料箱更大，同時重量更輕，並增加三個猛禽真空發動機。

The third version of the Raptor is currently in design and will probably offer higher efficiency and therefore more delta-v potential.

猛禽 "的第三版目前正在設計中，很可能會提供更高的效率，是以也會有更大的 delta-v 潛力。

Now there are other more long-term solutions as well.

現在還有其他更長期的解決方案。

Consider Mars' outer moon Deimos.

考慮一下火星的外圍衛星狄莫斯。

The delta-v required to move from low-Earth orbit to the orbit of Deimos is only around 5.3 kilometers per second, that's a lot more manageable and imagine if you could build an outpost or a Mars gateway at the orbit of Deimos.

從低地球軌道移動到狄奧摩斯軌道所需的 delta-v 僅為每秒 5.3 公里左右，這要容易得多，想象一下，如果你能在狄奧摩斯軌道上建造一個前哨站或火星網關，那將會是多麼美好的事情。

Now we have the potential to refuel the ship so that it can make the hardest part of the journey with more than enough delta-v to spare.

現在，我們有可能為飛船補充燃料，使其在完成最艱難的一段旅程時，還能有足夠的三角飛行速度。

This buys you a margin of error that would increase the safety of a Mars landing by orders of magnitude.

這樣就有了一定的誤差餘地，可以將火星著陸的安全性提高几個數量級。

So yes, landing a fully loaded Starship on Mars is going to be logistically insane.

所以是的，在火星上著陸一艘滿載的星際飛船在邏輯上是非常瘋狂的。

This is one of those situations where SpaceX won't know anything for certain until they try.

在這種情況下，SpaceX 在嘗試之前無法確定任何事情。

We've seen this twice now with just launching the Starship and both times it exploded in mid-air.

我們已經兩次看到這種情況了，僅僅是發射星際飛船，兩次都是在半空中爆炸。

Learning to land on Mars is more than likely going to be a similar affair.

學習登陸火星很可能也是類似的事情。

They are much more likely to fail before they succeed.

他們在成功之前更有可能失敗。

They could fail multiple times, it's going to require a spectacular amount of willpower to make this work, to not give up, and probably more than a lot of people are genuinely prepared for.

他們可能會多次失敗，這需要驚人的意志力才能成功，才能不放棄，這可能超出了很多人的真正準備。

And then eventually, we try to do this with people on board.

最終，我們會嘗試讓人們參與進來。

And calling this ambitious seems like an incredible understatement.

說它雄心勃勃似乎有些輕描淡寫。

But over the history of humanity, we've accomplished the impossible many times over.

但在人類歷史上，我們已經多次完成了不可能完成的任務。

So what's one more?

那麼還有什麼？

Join us back here every week for more updates on everything aerospace industry and interstellar exploration related.

請每週回到這裡，瞭解更多有關航空航天工業和星際探索的最新資訊。

Make sure to give the video a thumbs up today if you liked it, that really helps us out for real.

如果您喜歡這段視頻，請務必在今天為它豎起大拇指，這將真正幫助我們。

And subscribe to the Space Race for more videos just like this.

訂閱太空競賽，獲取更多類似視頻。

We do one long form essay and one news update every week.

我們每週撰寫一篇長文和一條新聞。

And if you'd like more, we've got two more on the screen for you right now.

如果您還想了解更多，現在螢幕上還有兩個。