Why We Should Put Rockets On the Moon Reason for||||spacecraft||| Warum wir Raketen auf den Mond schicken sollten Por qué deberíamos poner cohetes en la Luna Pourquoi nous devrions envoyer des fusées sur la Lune Perché dovremmo mettere dei razzi sulla Luna 月面にロケットを設置すべき理由 달에 로켓을 띄워야 하는 이유 Kodėl turėtume paleisti raketas į Mėnulį Waarom we raketten op de maan moeten zetten Porque é que devemos colocar foguetões na Lua Почему мы должны поставить ракеты на Луну Neden Ay'a Roket Göndermeliyiz? 为什么我们应该把火箭送上月球 為什麼我們應該把火箭送上月球

Thank you to brilliant for supporting PBS Digital Studios. Appreciate|||||backing|Public Broadcasting Service|online|PBS Digital Studios

Hey smart people, Joe here.

I'm here with Don Pettit you probably recognize this guy. |||Don Pettit|Don Pettit|||know||person

He's my favorite astronaut that I know. He is||preferred|space traveler|||

Hold on Joe, you only know one astronaut.

That's not important,

you're still my favorite. you are|||

Last time that I was here, we were hanging out, we were ||||||||spending time||| De laatste keer dat ik hier was, waren we aan het rondhangen, we waren

talking about how to drink coffee in space and the cool invention that you ||||consume|space coffee|||||awesome|||

made to do that, and and when we were done I walked over here to this building |||||||||||went||||| hecho para hacer eso, y cuando terminamos caminé hasta aquí a este edificio

to check out this thing.

This is a Saturn five. |||Saturn rocket|

It made me think when I was sitting in here looking at the size of ||||||||||gazing at||||

this thing, because until you're standing up next to this thing, you just do not ||for the reason that|||upright|||||||||

have a sense of how massive the Saturn 5 is.

It took all of this to get just this little bit to the moon and back.

That's the command module. ||control module|control center Ese es el módulo de mando. Dat is de commandomodule.

So why did it take all of that to do this. Entonces, ¿por qué hizo falta todo eso para hacer esto?

That's called the rocket equation. |||rocket|rocket equation

Oh I was told there would be no math. exclamation||||||||mathematics Oh, me dijeron que no habría matemáticas.

So there's a famous saying: the dinosaurs went extinct because they didn't have a |there is||well-known|||dinosaurs||became extinct||||| Así que hay un dicho famoso: los dinosaurios se extinguieron porque no tenían un

space program. |initiative

But we do!

Half a century ago, astronauts got in a rocket a lot like this one to send this tiny little ||hundred years|in the past|space travelers|||||||||||deliver|||

bit up here on a 384,000 km trip to the moon and back. |||||kilometers|journey|||||

And they were able to do it because a lot of extremely smart and dedicated people pushed |||capable||||||||very|||committed||

engineering and chemistry to the limits to create a 36-story tower of carefully-controlled engineering|||||parameters|||||building||meticulously regulated|regulated ingeniería y la química al límite para crear una torre de 36 pisos de

space fire powerful enough to escape this… |||||break free from| fuego espacial lo suficientemente potente como para escapar de este...

…this is Earth's gravity well. |||gravitational pull|gravitational well

This is a way to visualize how anything in the universe with mass causes spacetime itself |||||represent||any object|||cosmos||matter or weight|affects|the fabric of reality| Esta es una manera de visualizar cómo cualquier cosa en el universo con masa causa el propio espaciotiempo

to warp, bending or attracting any other thing with mass. |distort|curving||pulling towards||||| deformar, doblar o atraer cualquier otra cosa con masa.

The more massive the object, the deeper the gravity well, and… well, if you don't ||||||greater|||||||| Cuanto más masivo sea el objeto, más profundo será el pozo gravitatorio, y... bueno, si no

expend enough energy, you're trapped inside the well, unable to escape. use up||||stuck||||not able||

Fortunately, rockets are excellent energy-expending, gravitational well escape devices. luckily|||superior||energy-consuming|gravity-related||| Afortunadamente, los cohetes son excelentes dispositivos de escape de pozos gravitatorios que gastan energía.

But the ability of a rocket to escape a gravitational trap–or not–depends on some basic rules ||capability||||||||field|||is determined by|||fundamental|principles

of physics and chemistry. |the study of matter||the study of matter

And these rules…

…are written down in the Rocket Equation. |recorded|||||

The rocket equation deals with moving from point A to point B in a gravitational |||addresses||||||||destination|||

field.

And it tells you how much propellant you need in order to do that, compared with how much ||indicates|you|||fuel||||||||in relation to|||

your total rocket weighs. |overall||has a weight of

Let's explain this idea of “mass fraction” real quick. Let us|clarify|||||part of mass||quickly

Take a typical gas burning car. ||standard|gasoline||vehicle

You don't need very much gas in the tank, compared to the total mass of the car, to ||||||||fuel tank|||||||||

get from point A to point B down here on Earth

I'm on my way to Houston to talk to Don the astronaut… but you already knew that |||||Houston Texas||speak with||||space traveler|||||

because you're watching the video right now… but the point is, this car, its total ||viewing||||||||||||

weight is only 3-4-5% fuel. |||energy source

But that airplane… that's 30-40% fuel. ||aircraft||

JH: What percentage is this thing fuel? John Henry||proportion|||| JH: ¿Qué porcentaje es este combustible cosa?

DP: A rocket, per the rocket equation, is 85 to 90 percent propellant, which means everything |||according to||||||of total weight|fuel source||indicates that| DP: Un cohete, por la ecuación de cohetes, es 85 a 90 por ciento de propelente, lo que significa que todo

you see here as this rocket, is only 10 to 15% of the mass of the total vehicle. |||||||||||||||system

And that 10-15% is the entire structure of the rocket. ||||whole|design||the entire|spacecraft

The people, life support, and all the cool science stuff we want to carry into space? The||sustenance|sustaining systems||||||equipment||||||

They're only 1% of the mass of the total rocket, propellant and all. They are||||||||||| Son sólo el 1% de la masa total del cohete, con propulsor y todo.

JH: So it takes 99% of the mass of this thing to get the 1% of cool important space stuff |||requires||||||||||||||

up there.

DP: That's correct. ||right

So this is the Rocket Equation, a simplified version of it anyway. |||||||simplified version|form|||in any case

It was figured out by a Russian rocket scientist named Konstantin Tsiolkovsky. ||determined||||Russian||expert in rockets|called|Konstantin Tsi|Konstantin Tsi

Don't be scared by how mathematical this looks. ||afraid|||complex or technical||appears No te asustes por lo matemático que parece.

It's actually pretty easy to understand. |||simple|to verb|

e is just a mathematical constant, it's roughly the number|||||fixed value||

2.72 or so.

And what this means is that when there's an explosion here, how much of that energy

is directed to the rocket going this way. |aimed||||||

We lose some of that explosion energy to things like friction, heat, engine efficiency and, |lose|||||||||resistance||engine performance|engine performance|

most importantly, gravity. |crucially|

And since this is all an exponent, it means that if we increase the strength of the gravity ||||||indicator||||||boost||intensity||| En aangezien dit allemaal een exponent is, betekent het dat als we de zwaartekracht vergroten...

field we're in, this number goes up really quickly. |||||increases|||

Like compound interest. |compound|financial growth

And that means the ratio of your rocket that has to be propellant goes up really quickly. ||||proportion||||||||||||

The stronger the gravitational field, you pretty quickly find that you need a lot of |greater|||||||||||||

rocket to get a little bit of stuff out of your gravity well and up into space. cohete para sacar un poco de material de su pozo gravitatorio y llevarlo al espacio.

So, if you're in the business of engineering rockets, what can you do? |||||field|||||||

DP: To get off the planet Earth, you've got the gravity of Earth… and we're not

gonna change that.

And then you have the energy in your rocket propellant, and once you max out what is possible |||||||||||||maximize|||| Y luego tienes la energía en el propulsor de tu cohete, y una vez que maximizas lo que es posible

with chemistry, then there isn't anymore. |||||any more con química, entonces ya no la hay.

That's it? ¿Eso es todo?

That's it.

You max out the energy density, and you plug it in the rocket equation, and you have |||||energy concentration|||insert|||||||| Si maximizas la densidad de energía y la introduces en la ecuación del cohete, tendrás

to abide by what it says. |follow|in accordance with|||it states para cumplir lo que dice.

Think about that.

A rocket is basically a way to take the energy stored inside chemical bonds and use it to ||||||||||contained|||chemical connections||||

crawl out from the bottom of our gravity well. emerge|||||||| salir del fondo de nuestro pozo gravitatorio.

So rocket science isn't just physics.

We have to fiddle with chemistry too. |||experiment with||chemical processes| También tenemos que jugar con la química.

We have 4, maybe 5 classes of rocket propellants to choose from these days, just a handful |||types|||rocket fuels||select||||||a few

of chemical options to try and nudge the rocket equation in our favor. ||choices||attempt||influence|||rocket equation|||advantage

So the universe has set the rules, and we're just playing the game. ||||||||||||game of life

That's one of the best ways of describing it. ||||top|||explaining|

I call it the “tyranny of the rocket equation”. ||||overbearing constraint||||

Now I love talking to Don because I like how his brain works. |||||||||||mind|

He understands the rocket equation in precise mathematical detail. |comprehends|||||exact||specifics

But he's also able to engage his imagination, and use this knowledge to answer unexpected |||||utilize||creative thinking||||information|||surprising questions Pero también es capaz de utilizar su imaginación y sus conocimientos para responder a preguntas inesperadas.

questions, like what would our space program look like if we lived on a slightly different inquiries|||||||||||resided|||somewhat different|

planet.

Say you increase the size of Earth, so Earth's gravitational constant increases. |||||||||||grows larger

If Earth were about 10 percent, maybe 15 percent bigger, we would not be able to make a rocket |||||||larger in size|||||||||

to carry any useful payload into space. |||beneficial|cargo|| para llevar cualquier carga útil al espacio.

In essence, we could not get off this planet. |fundamentally|||||||

This is shocking news. ||surprising|information

Huge new developments. ||advancements

This makes me think of something: Do you think there could be alien planets, extraterrestrial |causes|||||||||||extraterrestrial|worlds beyond Earth|alien

civilizations, who just live on planets that are too big for them to get off of? societies|||exist||||||||||||

The sky's not the limit! |sky is|||boundary ¡El cielo no es el límite!

Whew. exclamation of relief Uf.

Gravity is.

The tyranny of the rocket equation is also the main thing separating us from making x-wings ||||||||the|primary factor||||||X-wing starfighters|spacecraft La tiranía de la ecuación del cohete es también lo principal que nos separa de hacer alas x

and Enterprises in real life. |businesses|||

As long as we're using chemistry for our rockets, we're engineering rockets at the

edge of what is possible in order to escape Earth's gravity well  But what if we could limit||||||||||||||||

find somewhere else nearby with a smaller gravity well we could fuel up? |a nearby location||||||||||| ¿encontrar otro lugar cercano con un pozo gravitatorio más pequeño donde repostar?

Hmm… what could that be? thinking sound|||| Hmm... ¿qué podría ser?

There's a lot of talk about going back to the moon.

You wanna go? |want to|

Oh, I'd go the moon in a nanosecond! |I would||||||an instant

It would take you a little bit longer than a nanosecond.

Yeah, it takes 3 to 5 days to get to the moon. Yes|||||||||

But it's an enabler for allowing humans to expand into other places in our solar system. |||facilitator||permitting|||move out||||||solar system|solar system Pero es un medio para permitir a los humanos expandirse a otros lugares de nuestro sistema solar.

A rocket scientist named Krafft Ehricke ||||Krafft Ehricke|Krafft Ehricke Un científico de cohetes llamado Krafft Ehricke

made one of my favorite quotes:  “If god intended man to be a spacefaring |||||quote||God|designed|||||traveling in space hizo una de mis citas favoritas: "Si Dios quiso que el hombre fuera un astronauta... maakte een van mijn favoriete citaten: "Als god de mens als een ruimtevaarder had bedoeld"

species, he would have given us a moon” If Earth had no moon, next stop past Earth

would be Venus or Mars, both very difficult to go right out of the box. ||planet Venus||||||||||||from the start serían Venus o Marte, ambos muy difíciles de salir de la caja.

The moon, 3 to 5 days away, there are resources we can use, |||||||supplies|||

What kind of resources? |type||

Primarily propellant. mainly used for|

Imagine if you could make your rocket propellant from resources you find on the moon. Envision||||||||||||||

What can you make rocket fuel out of that you can find on the moon? ¿Con qué se puede fabricar combustible para cohetes que se pueda encontrar en la Luna?

You can't make it out of rocks. ||||||stone materials

Water!

There's water on the moon?

There's water on the moon!

We didn't know this during the Apollo era, but now we have verified there is water on ||||||Apollo program|period|||||confirmed||||

the moon, significant quantities of water on the moon. ||large|large amounts|||||

Water is found throughout the rocky planets where human beings would be interested in |||in all||solid surface||||humans||||

exploring. investigating

So if you make rocket propellant systems based on hydrogen and oxygen, you will at least |||||||using||hydrogen||||||

in concept be able to refuel your rockets almost anywhere you want to go in our solar |theory||||replenish fuel||||any location|||||||

system.

So right now, would we have the ability

to launch a rocket from Earth with people on it and point it directly at Mars? |send off||||||||||||||

Or is that just really really hard?

Yeah, it's tough to do that. ||difficult|||

It would take a lot of propellant to go from Low Earth Orbit straight to Mars and back ||||||||||||Orbit|||||

again, would require 8-12 Saturn V launches just to stage one mission. ||need||V rocket|rocket launches|||||spaceflight operation de nuevo, requeriría de 8 a 12 lanzamientos del Saturno V sólo para llevar a cabo una misión.

Wow. expression of surprise

That's basically the whole Apollo program for just one mission to Mars. |||entire||||||||

And here's where a little bit of imagination, |this is||||||

combined with the science we've just learned, can show us a solution to another interesting together with||||||acquired knowledge||demonstrate||||||fascinating topic

problem.

Now remember how different vehicles require a different fraction of propellant compared ||||types of vehicles|||||||

to their total mass to go from point A to point B?

A car is a few percent, an airplane is 30 to 40 percent, and a rocket is more than 80

percent.

This number is so high because…

…Earth is a really hard gravity hole to get out of. ||||||gravitational well||||

But the moon is a much smaller gravity hole to escape from.

Launch your rocket from lunar gravity, and according to the rocket equation it only has ||||moon|||in accordance with|||||||

to be about 30 to 40 percent propellant…

…and 30 to 40 percent propellant is less like the Saturn V, and more like the aviation ||||||||||||||aircraft

industry here on Earth, and we're already pretty good at engineering planes. aviation sector|||||||||||aircraft

The dinosaurs got stuck down here. |||trapped||

To explore the rest of the solar system, like centuries of explorers before us, we need |investigate||remaining part||||||centuries of||explorers of the|||| Para explorar el resto del sistema solar, como hicieron siglos de exploradores antes que nosotros, necesitamos

to cross over this one tall hill so we can see what's on the other side. |climb over|||||mountain|in order to||||what is||||

And we've got a much easier climb ahead of us if we start from the moon. ||||||ascent||||||||| Y tenemos una escalada mucho más fácil por delante si empezamos desde la Luna.

Sounds like a pretty good reason to go back, and even stay for a while. ||||||||||||||for a bit

And you'll get to see some cool rocks while you're up there too. |you will||||||||||| Además, podrás ver algunas rocas preciosas mientras estás allí arriba.

You'll see some cool rocks.

Stay curious.