Why We Should Put Rockets On the Moon

published on July 13, 2020

Thank you to brilliant for supporting PBS Digital Studios hey smart people Joe here I'm here with Don Pettit you probably recognize this guy he's my favorite astronaut that I know hold on Joe you only know one astronaut that's not

Important you're still my favorite last time that I was here we were hanging out we were talking about how to drink coffee in space and the cool invention that you made to do that and and when we were

Done I walked over here to this building to check out this thing this is a Saturn five it made me think though when I was sitting in here looking at the size of this thing because until you're standing up next to

This thing you just do not have a sense of how massive the Saturn 5 is is that it took all of this to get just this little bit to the moon in back that's the command module so why did it take all of that to do this or that's called

The rocket equation oh I was told there would be no math so there's a famous saying the dinosaurs went extinct because they didn't have a space program but we do and half a century ago astronauts got in a rocket a

Lot like this one to send just this tiny little bit up here on a 384,000 kilometers rip to the moon and back and they were able to do that because a lot of extremely smart and dedicated people pushed engineering and chemistry to the

Limits to create this 36 storey tower of carefully controlled space fire powerful enough to escape this this is Earth's gravity well this is a way to visualize how anything in the universe with mass causes space-time itself to warp bending

Or attracting any other thing with mass and the more mass of the object the deeper the gravity well and well if you don't expend enough energy well you're trapped inside the well unable to escape fortunately rockets are excellent energy

Expending gravitational well escape devices but the ability of a rocket to escape a gravitational trap or not depends on some basic rules of physics and chemistry and these rules are written down in the rocket equation

Thanks the rocket equation deals with moving from point A to point B in a gravitational field it tells you how much propellant you need in order to do that compared with how much your total rocket weighs let's explain this idea of

Mass fraction real quick take a typical gas burning car actually don't take a car that's illegal but you don't need very much gas in the tank compared to the total mass of the car to 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 because you're watching the video right now but the point is this car its total weight there's only three four maybe five percent fuel

But that airplane that's 30 or 40 percent fuel what percentage is this thing fuel a rocket per the rocket equation is 85 to 90 percent propellant everything you see here as this rocket is only 10 to 15 percent of the total

Mass of the vehicle and that 10 to 15 percent is the entire structure of the rocket the people the life support all that cool science stuff we want to carry into space there are only one percent of the mass of the total rocket propellant

And all so take 99 percent of the mass of this thing to get the 1 percent of cool important space stuff up there that's correct this is the rocket equation a simplified version of it anyway it was figured out

By a Russian rocket scientist named Konstantin Tsiolkovsky now don't be scared by how mathematical this looks it's actually pretty easy to understand now this is the ratio of the mass of your rocket with a full gas tank

To the mass of your rocket with an empty gas tank he is just a mathematical constant it's roughly 27 2 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

And we lose some of that explosion energy to things like friction and heat engine efficiency and most importantly to gravity and since this is an exponent it means that if we increase the strength of the gravity field we're in

This number goes up really quickly like compound interest and that means the ratio of your rocket that has to be propellant goes up really quickly so the stronger the gravitational field you pretty quickly find out that you need a

Lot of rockets to get a little bit of stuff up and out of your gravity well and up into space so if you're in the business of engineering rockets what can you do to get off a planet Earth you've got the gravity of Earth and we're not

Gonna change that and then you have the energy in Urraca and once you max out what is possible with chemistry then there isn't anymore you max out the energy density and then you plug it in the rocket equation and

You have to abide by what it says think about that a rocket is basically a way to take the energy stored inside chemical bonds and use it to crawl out from the bottom of our gravity well so rocket science isn't just physics we

Have to fill it with chemistry too and we have four maybe five classes of rocket propellants to choose from these days just a handful of chemical options to try to nudge the rocket equation in our favor so the universe is set the

Rules we're just playing the game that's one of the best ways of describing it I call it the tyranny of the rocket equation now I love talking to dawn because I really like how his brain works he

Understands the rocket equation in precise mathematical detail but he's also able to engage his imagination and use this knowledge to answer unexpected questions like what would our space program look like if we lived on a

Slightly different planet say you increase the size of Earth so the Earth's gravitational constant increases if Earth were about 10% maybe 15% bigger we would not be able to make a rocket to carry any useful payload into space in

Essence we could not get off this planet this is shocking news huge new developments this makes me think of somebody do you think there could be alien planets extraterrestrial civilizations who just live on planets

That are too big for them to get off of yeah the sky is not the limit gravity is the tyranny of the rocket equation is also the main thing separating us for making x-wings and enterprises in real life as long as we're using chemistry

For our rockets we're engineering those rockets the edge of what is possible in order to escape Earth's gravity well but what if we could find somewhere else nearby with a smaller gravity well where we could fuel

Up hmm just of where that would be there's a lot of talk about going back to them and you want to go oh I'd go to the moon in a nanosecond it would taking a little bit longer than an annus yeah it takes takes

Three to five days to get to them on its an enabler for allowing human beings to expand into other places in our solar system rocket scientist by the name of Kraft Eric he made one of my favorite quotes if God intended man to be a

Spacefaring species he would have given us a moan if earth had no moan next stop past earth would be Venus or Mars both very difficult to go right out of the box the moon three to five days away there are resources we can use what kind

Of resources primarily propellant imagine if you could make your rocket propellant from resources you find on the moon what can you make rocket fuel out of that you can find on the moon because water rocks

Yeah there's no water on the minute there's water on the moon in the polar regions of the moon some craters are deep enough to be in permanent shadow protected from the sun's rays and recent lunar observations have confirmed that

Frozen h2o persists inside these dark craters using electricity this water could be split into hydrogen and oxygen for rocket propellant water is found throughout the rocky planets where human beads would be interested in exploring

So if you make rocket propellant systems based on hydrogen and oxygen you will at least in concept be able to refuel your Rockets almost anywhere you want to go in our solar 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 or is that just really really hard yeah it's tough to do that it would take a lot of propellant to go from low Earth orbit straight to Mars and come back again would require 8

To 12 Saturn five launches just to stage one mission Wow that's basically the whole Apollo program for just one mission to Mars and here's where a little bit of imagination

Combined with the science we've just learned can show us a solution to another interesting problem now remember how different vehicles require a different fraction of propellant compared to their total mass to go from

Point A to point B a car is a few percent an airplane is 30 or 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 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 to be 30 to 40 percent propellant and thirty to forty percent propellant that's less like a Saturn 5 and more like the

Aviation industry here on earth and we're already pretty good at engineering planes see the dinosaurs they got stuck down here to explore the rest of the solar system like centuries of explorers before us we need to cross over this one

Tall hill see what's on the other side and we've got a much easier climb ahead of us if we start from the moon sound like a pretty good reason to go back and maybe even stay for a while and you'll see some cool rocks while you're up

There too you'll see some cool rocks stay curious as always thank you to our patrons for being part of our community and help making episodes like this possible we couldn't do it without you and a big thank you to brilliant for

Supporting PBS Digital Studios now making YouTube videos is not rocket science but rocket science is rocket science and that means having some serious physics and math and computer science chops but becoming awesome at

Those subjects doesn't have to be dull not with brilliance it's a website and app built for ambitious and curious people who want to excel at problem-solving and understanding the world

Brilliant has over 50 interactive courses the hands-on approach that includes storytelling and code writing interactive challenges a whole bunch of different ways to learn like in

Brilliant scientific thinking course you'll develop a solid foundation in physics while playing with puzzles with brilliant you'll unravel concepts bit by bit and build up to an interesting conclusion while discovering deep truths

In unexpected places check out the link in the description to learn more and a special thanks to these galaxies brain patrons hey hey are you about to make a flat earth joke down in the comments I'm here to tell you to just say no to flat

Earth kids the only buzz I get it's for real science you've been to space can't believenot do this

Related Videos

hey guys techrax here coming at you guys with another giveaway this is gonna be an iPhone 5s two of these brand new phones not the one in this video guys this i...
hey guy there's a popular game in the app store called flappy bird right now and it's supposedly really annoying believe it or not I haven't played ...
hey guys tech Rex here so right here with me I have an Apple iPhone 5s this is the gold one I also have with me some liquid nitrogen yes this is the real deal a...
hey guys techrax here right here I have the iPhone 5s with me this is the champagne or the gold color I still can't really figure out if it's champagne ...
hey guys tear cracks here so this video really exciting video I have the new Samsung Galaxy s5 for you guys this is the long-awaited cellular devices releases i...
everyone techrax here in this video I've got the latest Samsung Galaxy s5 right here as well as the Apple iPhone 5s and we're going to be doing a simple...
everyone techrax here in this video guys have a really exciting device this is the Samsung Galaxy s5 charcoal black and I'm really liking I after seeing the...
everyone techrax here here with me off the Samsung Galaxy s5 this is a perfectly fine s5 it is cracked from the drop test that I had with also one minor neck as...
hey guys tetrax here so in this video I'm going to try and burn the newly released Samsung Galaxy s5 this is the shimmering white 16 gigabyte model and if y...
everyone techrax here so I got my burn Samsung Galaxy s5 and I wanted to see whether the heartbeat sensor would still work the heart monitor on your galaxy s5 a...
hey guys Tech Rex here so I'm really excited to bring you guys a giveaway for my channel but this time I'm actually teaming up with a buddy of mine your...
hey guys techrax here so in this video I'm going to be hopefully instructing you guys how to make your very own a tech sandwich slash burger slash meal so y...
hey guys techrax here so I've got a galaxy s5 here this is the copper gold hopefully you guys can see pretty well it is sunset so it's getting a little ...
hey guys techrax here so right here with me I have a professional deep fryer in here is already some canola or corn or whatever oil I don't know vegetable o...
hey guys techrax here so just trying to make this video short and quick i'm having recently i got five hundred thousand subscribers and yeah most of you guy...
hey guys texture so in this video I have a drop test on the latest LG g3 device now this is actually the gold-coloured LG g3 this has not been released in the U...
hey guys techrax here so in this video we'll teach you guys how to make your iPhone indestructible this is essentially a case that's been around for yea...
hey guys techrax here soon in this video we had a train run over the iPhone 5s so we actually did this in two different instances initially we had a Space Gray ...
hey guys tech cracks here so in this video we're going to be dropped testing the newly released Amazon fire phone this is exclusive for AT&T and I belie...
hey guys techrax here so right here with me I have the Amazon fire phone this is the one I dropped and you know I thought what better what else do I do with thi...