跟读练习: How Reusable Rockets Work - 通过视频学习英语口语
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- Reusable rockets are revolutionizing space flight.
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The movement may have begun with SpaceX and their Falcon 9, but it's quickly spreading across the world.
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Chinese rockets are landing themselves right now, just not always successfully.
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Blue Origin is figuring out how to land their own gigantic rocket booster, and an underdog startup out of New Zealand is looking to
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join the game this year with a reusable rocket of their own.
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For all of the many differences between these vehicles and their builders, there are fundamentals that tie them all together.
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the key ingredients of the reusable rocket.
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And this is what makes them work.
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To begin, we should clarify that when we say "reusable rocket", what we really mean is the booster stage.
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Typically, that's the lower two -thirds of the fully stacked rocket.
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A booster is essentially just a big fuel tank with some engines at the bottom.
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At this moment, there is only one rocket booster in the world that has proven to be consistently reusable, and that is the SpaceX Falcon 9.
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So we are going to use this as our reference point, but the same process will apply to all of the new rocket designs that are in development.
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Now, you might also be familiar with some reusable upper -stage vehicles, also known as orbiters.
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The space shuttle is a famous example.
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The SpaceX Starship is a more modern example, and there have been a few reusable space planes developed in between.
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These orbiters are significantly more complex and diverse vehicles, each deserving their own explanation,
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so we're going to put that subject to the side for today and keep our focus on the reusable rocket booster.
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While the space shuttle may have been famous for its orbiter, this 1980s -era NASA rocket also pioneered a method for reusable boosters as well.
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If we look at how the space shuttle was configured on the launchpad, we have this big orange tank in the middle that holds liquid propellant for the main engines.
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On the back side is the spaceplane, and to the right and left are the side boosters.
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These burn solid propellant, just like a model rocket engine
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and their job is to get the shuttle off the ground and through the most dense section of Earth's lower atmosphere.
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At an altitude of about 45 kilometers, or around four times the height of a commercial airplane,
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the side boosters are released and allowed to fall back down to Earth.
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The reason for this is you don't want your orbiter to carry around any dead weight, so once the booster's job is done, we always separate the stages of our rocket.
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Now this is where most conventional rocket boosters will simply fall back down into the ocean.
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American space launches typically lift off from the east coast of Florida, so by the time stage separation occurs, the rocket is far out over the Atlantic Ocean.
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If you were to dive down to the bottom, you'd find an enormous graveyard with hundreds of old boosters scattered across thousands of acres of seabed.
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This is not an ideal way to operate.
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It's bad for nature, but it's also bad for us human beings too.
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We've taken months or even years worth of highly complex engineering work and expensive materials
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and then we've converted that all into a pile of garbage at the bottom of the ocean
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that only ever contributed about 90 seconds of actual usefulness.
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Now, wasted time and resources is one thing, but it's the wasted money that has really driven the movement towards reusable rocket technology.
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every time you watch a conventional rocket booster fall helplessly back to Earth
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That's somewhere in the neighborhood of 50 million dollars sinking down to the bottom of the ocean.
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Something that you won't find in the rocket graveyard are side boosters from the space shuttle,
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because after stage separation, these rockets actually deployed parachutes and floated softly back down to the water,
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where they'd wait for a boat to arrive and tow them back to port.
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Once all of the solid propellant is burned up, you're essentially just left with two empty metal tubes.
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Now they just need to be cleaned up and refueled before they're good to go for another shuttle launch.
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And for many years, that was the only way to reuse a rocket until SpaceX came along.
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Falcon 9 introduced a new concept to the world of rocketry.
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Vertical takeoff and vertical landing.
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That means we are not just parachuting our way down into the water anymore.
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The booster will guide itself back to the landing pad for a controlled descent.
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which, Begs a question.
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Why didn't SpaceX just go with the parachute method?
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Sounds a lot easier, right?
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And it is, but there's an important distinction to make.
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On the space shuttle, all of the important and delicate flight hardware was inside the orbiter, which landed itself on the ground.
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It didn't get wet.
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Now, on a conventional rocket that doesn't have a space plane attached to it, All of that flight hardware is located inside the booster, so You don't want to get water in there.
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But since you already have all of those computers and electronics onboard that guide the booster off the ground and into space,
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you could theoretically use that same hardware to just run the play in reverse.
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Guide it from space back down to the ground.
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The idea wasn't unique to SpaceX.
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Rocket scientists had been pondering this method for decades, but it was always written off as being simply impossible to accomplish in the real world.
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The New Zealand startup Rocket Lab actually tried to cheat the system with their electron booster.
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What they had planned to do was parachute the rocket down through the sky, and then just before it hit the water, a helicopter would fly in and snatch it out of the air.
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That was a badass plan, but when they actually tried to do it in real life, the helicopter pilot quickly realized this was way too sketchy to be safe,
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and he bailed on the catch attempt at the last minute and the company never tried it again.
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Anyway, back to our timeline here.
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In 2011, SpaceX would begin their quest to achieve the impossible.
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By 2012, they began flying a test vehicle called the Grasshopper.
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a small fuel tank with a single engine, and four fixed landing legs.
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It was designed to fly up about one kilometer and then come straight back down for a vertical landing.
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This kind of maneuver is often referred to as a hop.
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Grasshopper experienced some trial and error, but it was able to accomplish eight successful hops in one year of operation.
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What this test demonstrated was our first necessary ingredient
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for a reusable rocket an engine that can be throttled down to a very low power level.
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In order to land, you need the engine to burn just enough to slow you down, but not so much that it starts to push the rocket back up again.
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This is a delicate balance, and that's exactly what SpaceX was trying to find with Grasshopper.
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In 2013, they began scaling this test up to the Falcon 9.
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That name tells us that this rocket has nine engines, which is a lot.
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Most rockets previous to this had four or five engines at most, but SpaceX knew that they wanted a reusable rocket booster,
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so instead of using a small number of big engines, they chose a large number of small engines.
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This is essential for achieving that balance we talked about earlier.
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By the time our rocket comes in for a landing, almost all of the fuel in the tank has been burned away, so it's mostly just a big empty tube.
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Nowhere near as heavy as it was during launch, so we only need a little bit of power to slow it down.
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A big engine, even running at its lowest power level, is still going to push too hard, and that would actually keep our rocket in the air.
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It wouldn't be able to touch the ground.
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That is what we saw in phase one of Falcon 9's experimental landing program from 2013 to 2015.
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The rocket would fall back from space, over the open ocean, and it would relight
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that one center engine to slow down for a very soft landing on the surface of the water.
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That was the first real -world test, and what SpaceX was trying to prove was the ability to restart their booster engines mid -flight.
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This was not something that any other rocket maker had really needed to consider.
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You light your booster on the launchpad, you burn until it runs out of gas, and then it winds up as another addition to the rocket graveyard.
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But in order to land your booster, it actually needs to stop and restart the engines multiple times on the way back down.
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This is where problems tend to arise.
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Rocket engines are volatile by nature.
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When you light them on the launch pad, you do so in the ideal condition.
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But when you try and do the same thing in mid -air, stuff tends to explode.
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Check out the second test flight of the SpaceX Starship.
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The booster was going to attempt a soft water landing just like what we saw with Falcon 9.
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But as soon as it tried to restart those engines to begin slowing down, Boom!
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Unfortunately, this is the kind of thing that you can only test by doing it live.
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So as more and more reusable rockets join the party, we're probably going to see a nice variety of mid -air explosions.
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It's all part of the process.
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Now, we know that reusable rockets need small engines to land, but they also need a large amount of power to lift off.
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For a rocket to achieve reusability, it's actually going to need more power than a conventional rocket just to get the same amount of mass into space,
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and that's why you'll typically see a big cluster of those smaller engines all tied together.
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We have to remember that a disposable rocket booster is free to burn all of its fuel on the way to space, because it's just going to fall back down and splash into the ocean.
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but a reusable rocket needs to fly all the way to space, reaching a top speed of around 8000 km /h,
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and then it needs to slow all the way back down
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again to reach a speed of zero at the moment it touches the landing pad.
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That requires a bunch more fuel to be held in reserve for the landing.
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We also have to consider that a reusable rocket is going to be heavier than a disposable equivalent, because there's a bunch of extra hardware that is necessary for landing,
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but needs to be carried all the way into space before it really gets used.
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Most of that excess hardware is going to be needed to help steer the rocket, because going up only requires a very minimal amount of guidance.
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But getting back down, is where the real magic trick begins.
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Following stage separation at an altitude of around 80 kilometers, our rocket booster is going to begin the process of slowing down for a return to the launch site.
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In order to do that, we have to flip the entire rocket around so that the engines are pointing in the opposite direction.
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On Falcon 9, this is done using cold gas thrusters, which are little jets of compressed nitrogen gas.
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Thrusters are located in two pods on opposite sides of the rocket, right near the very top.
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This position gives them the maximum amount of leverage to push the booster all the way over
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and get the top end pointing back at the ground.
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Now we need to fire up all 9 rocket engines to start cancelling out all of the momentum
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that we just built up by flying to space.
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This is called the boost backburn.
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It's going to change our flight path from a big arc
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that goes out over the ocean to a loop that brings us back down to where we started from.
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Once the rocket is going slow enough that it starts to fall back down to Earth, we actually need to flip around again and get the bottom pointing back toward the Earth.
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As we begin to hit the atmosphere, a lot of heat and pressure is going to start building up underneath the rocket,
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and the best way to relieve that is actually to fire up the engines yet again.
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The re -entry burn will slow down the velocity even more and relieve some of that pressure, but the exhaust from the engines will actually push a lot of
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that excess heat away from the rocket and create a sort of protective shield underneath, also known as the jellyfish.
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Once we are through re -entry, the engines are shut down again and the booster goes into freefall.
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This is where steering becomes: Very important.
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One extra item that you'll find on every reusable rocket is a set of aerodynamic grid fins.
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These are able to redirect air as it flows over the booster.
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That allows them to steer the rocket all the way down through the atmosphere.
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This steering is all done autonomously.
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There is no person flying the rocket back down, it's a flight computer that's guided by something called an inertial navigation system.
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which uses sensors on the rocket to determine its position and orientation.
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Then it combines that information with the Global Positioning System or GPS to see exactly where the rocket is in the air.
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Then, that location is checked against a pre -programmed flight path, and if the computer sees any deviation from the plan,
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then it's able to use all of this data to steer itself back on course.
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In the final moments before landing, that single engine is going to relight to begin slowing the booster down, and as the velocity drops,
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so will the engine's throttle setting until it's down at the lowest power level.
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Then, landing gear is deployed, three legs made from a combination of aluminum and carbon fiber are pushed out by decompressed helium gas, and locked into position.
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Now, all that needs to be done is steer the rocket onto the landing pad, and shut down the engine at the moment the landing gear touches the ground.
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SpaceX may be the king of reusable rockets, but regardless of who builds these new rockets, the fundamentals of reusability remain the same.
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As radical as the Starship Super Heavy might be, it operates on a very similar game plan to the Falcon 9.
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It just trades the landing legs for giant robot arms, which is a whole other video.
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Blue Origin's New Glenn will perform the exact same routine as Falcon 9 once it gets going.
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They've already attempted one landing, and the booster exploded when they tried to relight the engines, which, as we've seen, is not uncommon, but they will try again very soon.
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And, maybe, by the end of this year, we might see the Rocket Lab Neutron make its own attempt.
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Will it succeed?
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Will it explode in mid -air?
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Will it smash into the landing pad like a flaming lawn dart?
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We don't know but we get to find out, and that's our favorite part of the Space Race.
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本课的词汇与口语要点
这节 B2 级别的口语课以视频“How Reusable Rockets Work”为素材。 视频中反复出现的词有：rocket, booster, engine, landing, reusable。 这段视频共有 153 个句子、2580 个单词可供跟读。 讲话部分时长为 14:42。 说话人语速自然，每分钟约 176 个词，接近日常对话。 只有 80% 的单词属于英语最常用的 3,000 词，词汇难度较高。
视频中的重点词汇
视频中最难的 15 个单词，附发音和释义：
| 单词 | 发音 | 释义 |
|---|---|---|
| booster 名词 | /ˈbustɚ/ | 助推器 |
| shuttle 名词 | /ˈʃʌtəl/ | 梭子 |
| steer 动词 | /stɪɹ/ | 掌舵, 驾驶 |
| parachute 名词 | /ˈpæɹəʃut/ | 降落傘 /降落伞 |
| graveyard 名词 | /ˈɡɹeɪvˌjɑɹd/ | 公墓 墓地, 墳地 /坟地 |
| explode 动词 | /ɪkˈsploʊd/ | 爆炸, 爆發 /爆发 |
| separation 名词 | /ˌsɛp.əˈɹeɪ.ʃən/ | 分割, 分離 /分离 |
| vertical 形容词 | /ˈvɝ.tɪ.kəl/ | 豎的 /竖的, 垂直 |
| throttle 名词 | /ˈθɹɔ.tl̩/ | 風門 /风门, 節流閥 /节流阀 |
| deploy 动词 | /dɪˈplɔɪ/ | 部署 |
| ingredient 名词 | /ɪnˈɡɹiːdi.ənt/ | 成份, 材料 |
| relieve 动词 | /ɹɪˈliːv/ | 安心, 放心 |
| startup 名词 | /ˈstɑɹtˌʌp/ | 初創公司 /初创公司, 新創企業 /新创企业 |
| velocity 名词 | /vəˈlɑsəti/ | 速度 |
| delicate 形容词 | /ˈdɛl.ɪ.kət/ | 微妙, 纖巧 /纤巧 |
视频中出现的短语动词
| 单词 | 释义 |
|---|---|
| back down 动词 | 做出讓步 /做出让步 |
| slow down 动词 | 減速 /减速, 放慢 |
| check out 动词 | 退房 |
| come along 动词 | 陪伴, 陪同 |
| figure out 动词 | 弄清楚 |
| find out 动词 | 找出, 查明 |
| go up 动词 | 上昇 /上升, 上去 |
视频中的语法
说话人最常用的结构，并附上视频中的原话：
| 结构 | 视频中的用法 |
|---|---|
| 被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的 | was configured · are released · is done |
| 现在完成时 have/has + 过去分词 — 过去发生但与现在仍有关联的事 | has proven · have been · We've taken |
| 定语从句 who / which + 从句 — 补充说明人或事物 | engines, which is · thrusters, which are · arms, which is |
需要注意的发音
说话人用了 21 次缩略和弱读形式，例如 don't, we've, didn't。请按听到的简短形式来说。
- “th” 音: throttle /ˈθɹɔ.tl̩/, thruster /ˈθɹʌ.stɚ/, underneath /ˌʌndɚˈniθ/
- “sh” 和 “zh” 音: shuttle /ˈʃʌtəl/, parachute /ˈpæɹəʃut/, separation /ˌsɛp.əˈɹeɪ.ʃən/, accomplish /əˈkɑm.plɪʃ/, deviation /ˌdiː.viˈeɪʃən/
- 长单词——注意重音位置: separation /ˌsɛp.əˈɹeɪ.ʃən/, ingredient /ɪnˈɡɹiːdi.ənt/, velocity /vəˈlɑsəti/, helicopter /ˈheliːˌkɔptə(ɹ)/, aerodynamic /ˌɛəɹəʊdaɪˈnæmɪk/
中文母语者容易读错的音：
- /v/ — 不要读成 /w/，上齿轻触下唇: graveyard /ˈɡɹeɪvˌjɑɹd/, vertical /ˈvɝ.tɪ.kəl/, relieve /ɹɪˈliːv/, velocity /vəˈlɑsəti/, deviation /ˌdiː.viˈeɪʃən/
- 词尾辅音 — 要读清楚，后面不要加元音: parachute /ˈpæɹəʃut/, graveyard /ˈɡɹeɪvˌjɑɹd/, restart /ˈɹiːˌstɑɹt/, explode /ɪkˈsploʊd/, ingredient /ɪnˈɡɹiːdi.ənt/
- /r/ 和 /l/ 的区别: throttle /ˈθɹɔ.tl̩/, relieve /ɹɪˈliːv/, helicopter /ˈheliːˌkɔptə(ɹ)/, freefall /ˈfɹiːˌfɔːl/, kilometre /kɪˈlɑmɪtəɹ/
如何用这段视频练习
- 先完整听一遍视频，不要开口，记下不认识的单词。
- 先用 0.75 倍速逐句跟读，熟练之后再回到正常速度。
- 录下自己的声音并与原声对比，特别注意 booster, shuttle, steer 这类单词。
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。