Endeavour, Houston, We see a nominal MECO.
Welcome to space.
What goes up must come back down.
This is true for the first stage of the SpaceX
Falcon 9 rocket you can see coming in for
a pinpoint landing.
To guide itself to a landing like this it
has to precisely control its fall through
the air.
To do that, it uses these things here, they're
called grid fins.
Some of you will probably be quite familiar
with them.
They can rotate like this, which allows us
to push the top of the rocket around.
Let's have a look at this.
When we rotate a grid fin like this, it will
deflect the oncoming air, which will cause
the top of the rocket to be pushed in the
opposite direction to that deflected air.
And it can move about like this.
If all of the gridfins rotate like this, we
can twist the Falcon 9 first stage.
The effect of this is that we can move the
rocket's top around, which causes the whole
rocket to rotate.
So the oncoming air gets deflected, causing
the rocket to be pushed.
This can help assist us in our push towards
the landing zone, whether that be back on
land or on the drone ship, as we can see here
coming in for a brilliant pinpoint SpaceX
landing.
A lot of you will be familiar with the fact
that SpaceX is developing Starship and Super
Heavy.
Super Heavy is a first stage booster and so
it lands in a very similar way to the Falcon
9 first stage, using grid fins to make a pinpoint
landing.
But the Starship is quite different.
When it lands it's coming back from orbit,
so it's going really fast and it's going belly
first.
Quite different to the boosters.
It controls itself using these large fins
at the back here and these smaller fins up
the front here.
These fins allow us to alter where the centre
of the air pressure is pushing on the vehicle.
The vehicle has a centre of mass as shown
here by this yellow and black ball.
We can rotate around the centre of mass depending
on where the air is pressing on the vehicle,
which is represented by this red arrow.
We can see when we retract these fins at the
back here, we are pushing more on the front
than we are on the back and so this red arrow
is moving up to represent that.
Which causes us to rotate around the centre
of mass, pitching back like this until we've
rotated to the point where that centre of
pressure against the vehicle is now back over
the centre of mass, stopping that rotation.
If we want to undo that rotation, then we
can extend these fins at the back here, causing
the centre of aerodynamic pressure to move
back down, causing that opposite twisting.
Until once again, that red arrow is over the
centre of mass again, stopping that rotation.
This also has the same effect when we retract
these front fins here, except it pitches us
forward instead of back.
We can also rotate in a rolling action by
retracting the fins on one side of the rocket
(the front and the back ones) causing the
centre of pressure to move to one side, causing
the roll.
Until the centre of pressure is back over
the centre of mass.
Then to undo that roll, we can extend the
fins again, causing the centre of pressure
to move to the other side, causing it to roll.
Until the centre of pressure is back over
the centre of mass stopping that roll.
We can also yaw in this twisting action here,
by retracting a fin on the top and a fin on
the opposite side at the back.
This causes something a bit similar to what
the gridfins were doing, with the deflection
of air in opposite directions at the front
and the back, causing this twisting.
The use of these fins allows us to precisely
control Starship's rotation and therefore
control where we're heading when we enter
into the atmosphere, either on Earth or on
Mars.
All of this can allow Starship to make a pinpoint
landing.
I really hope you've enjoyed this video and
I'll see you later.
Right now there is a recommended video and
the subscribe button waiting for you in the
Space Shuttle's payload bay.
