Rocket Science Class by Elon Musk

talk a little bit about sort of the progress you think you've made with SpaceX sure well I mean there's a lot of things where I think I didn't think would be successful so the the plate and the most significant thing is being able to land and at an orbit class rocket Bruce stage and and bring it both back to Cape Canaveral on land and land and be able to land on a drone ship out in the ocean the there is a bit of an education process that's needed to understand orbital dynamics because a lot of people can confuse of like why the heck are you landing a ship landing a rocket in a on a ship in the ocean that seems pretty inconvenient and that the reason is because that going up and staying up is actually about velocity horizontal to the Earth's surface so there's a huge difference between space and/or space and or and orbit it's 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 coastal waters now you're in the Pacific so it's like technically you're in the Pacific but but it's but orbit is like circumnavigating the globe it's a really giant difference and the 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 but then this little little sort of counterintuitive is that the space station is actually zooming around the Earth at 17,000 miles an hour even though it seems like it seems really still you know but it's moving really really fast I mean put them to perspective a bullet from a 45 gun your handgun is 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 that's why that is the tomb escape velocity not escape altitude there's no such thing as an escape altitude there's only an escape velocity you need to be a certain speed to escape the gravity of the earth yeah you can think of gravity is kind of a funnel in space-time so I thinking 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 if you if you spin or spin a marble or a coin on the corn funnel the when it's when it's far out it sort of spins slowly and then as it gets closer its bends faster and faster and if you want if you want if you were to start at the bottom of the coin funnel and you wanted to to to exit you'd spin it horizontally and it would it would spin out and and and that's really how you how you get to orbit yeah so how does the gravity well is like a funnel why you want to land on the ownership in the ocean because in order to get to orbit you all that matters is your horizontal velocity your altitude is doesn't doesn't really matter in fact the the the force of gravity at say the so nominal boundary of space 100 kilometres is almost exactly the same as it is in the strip's the earth is it like if it's a few percent lower than the surface the earth 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 New York 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 that's going up is to get out of the thick part of the atmosphere because that man at high velocity the atmosphere is thick as molasses and so it goes up very briefly but if you look at a long exposure of the the Rockets trajectory you'll see it goes up but it immediately curves over and starts going horizontal and so the at the at the point at which the the at the point which the stage is separate those two stages that the primary Bruce stage which is the most expensive part of the rocket the point of which that's that staging occurs can be as high as Mach 10 but it's so it's going away from the launch site at ten times the speed of sound so you know in order to get back to the launch site you would have to have enough I fuel an oxygen to reverse out that velocity and and 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 it's not about saving money on fuel or anything it's just physically impossible so because another sort of thing about if you're if you're in space is that there's nothing to react against so like whereas an aircraft can conserve 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 in it we if you want to go backwards you have to apply just so much energy as it took you to go forwards in fact twice as much really because you go to zero it out and then you've got a gotta land elsewhere yeah so bottom line is this thing is zing an apt just what was in answer yet super at ten times but it may well be over the ocean Christie ocean covers most of the oh it's it's actually at the point of separation it's not that far away it's maybe a hundred kilometers away from the launch site but it is going like hell in the opposite you know away from the launch site so the the young 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 a very very precise to within about a meter and then the rocket will then go from vacuum through rarefied air at hypersonic velocity and what so when it's it when it's in vacuum it has to obviously you can't use arrow surfaces you have to use the nitrogen Jets to control the the attitude and position and then as it starts to encounter the air we use grid fins because Griffins looked like what sort of like a waffle that they were quite well across a wide regime from both very high velocity hypersonics through supersonic transonic and subsonic so it's hard to it's it's hard to have Aero surfaces that work well across that entire regime and then so once the air forces become high it uses that before grid fins to sort of control its attitude and land itself yes it's controlling it's it's controlling pitch yaw and roll with with the grid fins and and then once those grid friends 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

Channel: Deadly Wise Turtle

Views: 1,076,416

Rating: 4.9324894 out of 5

Keywords: Elon Musk, Space X, Rocket

Id: -6RpfD04fPw

Length: 7min 53sec (473 seconds)

Published: Wed Dec 20 2017

Reddit Comments

[u/nyolci]

This is painfully awkward and embarrassing... Looks like he had picked up his knowledge from short and badly written news articles. Dropping scientific terms here and there just to show off...

[u/geminiqry]

That comment section is bloody traumatic.

[u/Musklim]

"Rocket Science Class".

[u/shitPOSTER-69]

I mean he isn’t the most well spoken person in the world