There is a bit of an education process
that's needed to understand orbital dynamics, Uhm, because a lot of people are confused of
like "Why the heck are you landing a ship, landing a rocket on a ship in the ocean? that
seems pretty inconvenient", um, and the reason is because that going up and staying up is actually
about velocity horizontal to the earth's surface so um, there's a huge difference between space
and or space and orbit, like space you could think of as like say being the international waters
boundary for the Pacific Ocean. Like if you go, you know, 100 miles offshore you're technically out of...
- Yes.
- ...coastal waters, now you're in the Pacific. - Right!
- So it's like technically you're in the Pacific, but orbit is like circumnavigating the globe. It's a really giant difference and the
reason that things go up and stay up is because you're zooming around the Earth so fast, that your
outward radial acceleration is equal to the inward acceleration of gravity, and so those balance out
and you have a net zero gravity. So when you see the space station, the thing that's little
sort of um, counter-intuitive is that the space station's actually zooming around the earth at
17 000 miles an hour.
- Even though it seems like it's just... - It seems really still, you know, but it's moving
really really fast and put that into perspective um, a bullet from a 45, um, gun in a handgun, um, is
is just below the speed of sound, so the space station is going more than 25 times faster than
that and that's what's needed actually to go up and stay up. And that's why there's the term escape velocity, not escape altitude. There's no such thing as an escape altitude, there's only an escape velocity. You need to be at a certain speed to escape the gravity of the Earth... Yeah, you can think of gravity as kind of a funnel in space time, um, so uh, think of it like a coin funnel like it
really it's very much like that, in you know, but it's obviously a sort of a four-dimensional coin
funnel, but uh, if you if you spin a spin a marble or a coin on a coin funnel, when it's when
it's far out it sort of spins slowly and then as it gets closer it spins faster and faster and
if you want , if you were to start at the bottom of the coin funnel and you wanted
to exit, you'd spin it horizontally and it would it would spin out and that's really how you how you get to orbit, um... - Yeah so, the gravity well is like a funnel...
- How does is that thing intertwined ... why you want to land on the on a ship in the ocean? Because in order to get to orbit you,
all that matters is your horizontal velocity your altitude is just doesn't really matter. In fact the, um, the force of gravity at say the nominal boundary of space, 100 kilometers is almost exactly
the same as it is on the surface of the Earth. Um, is it like if it's a few percent
lower than the surface of the Earth. Um, so in order to go up and stay up the only thing
that matters is how fast are you going horizontal to the Earth's surface, so you have that outward
radial acceleration or think of it like maybe a tetherball or something like that, it's really that
outward acceleration is the thing that matters. And so when the rocket is going to orbit, the
only reason it's going up is to get out of the thick part of the atmosphere, because that at
high velocity the atmosphere is thick as molasses. Um, and so it goes up very briefly but if you look
at a long exposure of the rocket's trajectory you'll see it goes up but immediately curves
over and starts going horizontal and so the, um, at the point at which the uh, the
point which the stages separate, those two stages... Um, the primary boost stage which is
the most expensive part of the rocket, the point at which that staging
occurs uh, can be um, as high as uh, Mach 10. But it's...., so it's going away from the
launch site at 10 times the speed of sound. So in order to get back to the launch
site you would have to have enough uh, fuel and oxygen to reverse out that velocity and boost back all the way to the launch site. And you just don't have, the physics of it
don't really allow you to have that much... it's not about saving money on fuel or
anything, it's just physically impossible. So um, because another sort of thing about, uh, if you're in space is that there's nothing to react against, so like whereas an
aircraft can circle very easily because it's reacting against air, in vacuum there's
nothing to react against. So the only way to go back the other direction is to apply
just as much energy as it took you to go... if you want to go backwards, you have to apply just
as much energy as it took you to go forwards, in fact or twice as much really, because you've got to
zero it out and then you've got to .... - You've got to land elsewhere!
- Yeah so bottom line is this thing is zinging out just zinging out yeah, at super... at ten times faster than a bullet!
- It may well be over the ocean, because the ocean covers most of the... Oh it's actually, at the point of separation it's
not that far away, it's maybe 100 kilometers away from the launch site, but it is going like hell in
the opposite, you know, away from the launch site, so the only way to really land
it is to have it continue on that arc, that ballistic arc and then land far out to
sea on a ship that's that's pre-positioned to a particular latitude and longitude, very
precise, to within about a meter, uh, and then the rocket will then go from vacuum through
rarefied air at hypersonic velocity, uh so when it's in vacuum it has to, obviously
you can't use aero services, you have to use uh, nitrogen jets to control the,
um, the attitude and position. You see the first stage is already being
turned around and you can see the nitrogen from our attitude control system helping guide
it back. And stage separation has been confirmed! And you can see the first
stage there flipping back, use the nitrogen thrusters... And then um, as it starts to encounter the air, um we use, um grid fins because grid fins,
uh, look like sort of like a waffle... And as you guys have noticed the grid fins have deployed on the side boosters as well as the center core, those work to help guide the boosters
back to a nice targeted soft landing. Um, they work quite well across a wide regime from
both very high velocity hypersonics through supersonic transonic and subsonic. They're stowed at the base of the vehicle and made up of state-of-the-art carbon fiber and aluminum honeycomb Stage 1 transonic Um, so it's hard to have aero services
that work well across that entire regime and then, uh, so once the air forces become high... The cape getting closer and closer... Ah, what a cool view! The first stage is passing through the
cloud layers right now... - It uses the um the four grid fins to sort of control its attitude...
- To land itself. Yeah it's controlling pitch yaw and roll with the grid fins, um, and then once and those griffins will then position it to where it's fairly close
to the ship and then it will light, in this case three of the nine engines to arrest the velocity
and then drop to one engine for precision right before landing. - Right. So why, why is that important,
why has this moment been important for you? Just a very tough, uh, engineering problem.
In the last 12 months or so I've come conclusion that it can be solved, um, and
and I think SpaceX is going to try to do it! Falcon 9 is essentially standing on the shoulders
of titans, as they like to say in literature. We've built upon a lot of those lessons the things
that NASA has learned we've taken that but used kind of a clean sheet of paper that says how can
you build a rocket knowing that we want to do things that have not been done before? Well, so in order to reuse the boost stage, which is about 70% of the cost of rockets... For the first stage, it starts its engines back up... it flips itself around and the whole first
stage is re-entering the Earth's atmosphere and slowly making its way back down for a landing
on a drone ship that is out in the Atlantic Ocean. Landing legs have deployed... And Falcon 9 has landed! - What cost is that, how much is it?
- Um, well I mean it's sort of on the order of 30 to 35 million dollars. - Right, so you want to save that. - Yeah, I mean it's like I try to tell my team it's like imagine there was a pallet of cash that was falling through the atmosphere and it was gonna burn up and smash into
tiny pieces would you try to save it? - Right, right, right!
- Probably yes!
- Yes, okay! - Yeah, that sounds like a good idea!
- Right, okay!
- Aha! Um, so, so yeah so we want
to get it back and that way we don't have to make another one! Oh, my God! Landing operators move on to 11.100 on
recovery one and recovery two This configuration is about four times the thrust of the Saturn V moon rocket, um, - Four times the thrust of the biggest rocket
humanity ever created before
- Yeah - Yeah, um, I mean, in as one does...
yeah um the universe appears to be 13.8 billion years old, Earth is like four and a half billion years old you know another half billion years or so the sun will expand and probably evaporate the oceans and make life impossible on Earth, which means that if it had taken consciousness ten percent longer to evolve it would never have evolved at all....ten percent longer... ...and I wonde,r I wonder how many dead one planet civilizations there are out there in the cosmos that never made it to the other planet and ultimately extinguish themselves or were destroyed by external factors... probably a few... Channeling Carl Sagan: "Look again at that dot, that's here, that's home that's us, on it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was lived out their lives... The aggregate of our joy and suffering, thousands of confident religions ideologies and economic doctrines, every hunter and foranger, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species lived there, on a mode of dust suspended in a sunbeam... Our planet is a lonely speck in the great enveloping cosmic dark, in our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves... the Earth is the only world known so far to harbor life, there is nowhere else, at least in the near future to which our species could migrate This is not true! This is false: Mars! and I think Carl Sagan would agree with that, he couldn't even imagine it at that time... - But why, Elon? Because this... because like, why do we need to build a city on Mars with a million people on it? in your lifetime, which i think is kind of what you've said you'd love to do? yeah i think it's important to have, um, a future that is inspiring and appealing, I mean I just think that they're like there have been reasons that you get up in the morning and you want to live Like why do you want to live? what, what's the point? What what inspires you, what what do you love about the future? And if if we're not out there, if the future does not include being out there among the stars, uh, and being a multi-planet species I find that it's incredibly depressing, if that's not the future that we're gonna have, um...
