[ Sound Effects ]
Hi I'm Matt.
Welcome back to Mars month on NASA Now.
[ Music ]
"The descent on Mars happens over such a short period of time
that we actually don't have any fail-safes built-in in terms
of being able to switch from one parachute to the next
or being able to turn one engine on and one engine off.
We only have one chance to get this right"
[ Sound Effects ]
There's much more of that ahead,
but first here's what's happening at NASA Now.
[ Sound Effects ]
As Curiosity got ever closer to "a place
where no man has gone before", members of the Star Trek team,
lent their star power to set the stage
for Curiosity's "Grand Entrance".
William Shatner, a pop culture icon and Wil Wheaton,
a successful actor and writer,
both have a huge social media following.
The two provided their own unique style on videos
that were intended to reach far beyond a traditional space
fan base.
To see these videos, visit the NASA Explorer Schools
Virtual Campus.
[ Sound Effects ]
Landing a spacecraft over 200 million kilometers away
with a 7 - 14 minute delay
in communications can create a real nail biting situation,
especially when you only have one chance to get it right.
In June, we caught up with Dr. Anita Sengupta,
Senior Systems Engineer for the Mars Science Laboratory: Entry,
Descent and Landing system.
Dr. Sengupta gave us a complete rundown of the amazing sequence
of events needed for the successful landing
of the Curiosity Rover on the surface of Mars.
[ Sound Effects and Music ]
EDL, Entry, Descent, and Landing is the controlled process
that allows you to get from really, really fast speeds,
just outside the atmosphere of a planet,
to incredibly slow speeds to enable a soft landing
on the surface of a planet.
You use EDL for landing on Earth, you use EDL for landing
on the moon, on landing on Mars, and then depending upon
which planet you're going to,
we'll slightly change the design of that system.
The traditional terminal landing descent
for the Mars Exploration rovers
and Mars Pathfinder rover was to use airbags.
But those airbag can only handle a certain size rover.
In this particular case, we actually had
to use a system called the Sky Crane System
because Curiosity is so big.
This is going to be a groundbreaking,
revolutionary approach to landing on Mars
and we're very excited.
[ Music ]
The Entry Descent and Landing sequence has several
different phases.
The first one is when we initially interact
with the Martian atmosphere.
And when we do that, we experience drag
which is this interaction with the atmosphere
of the face of an entry vehicle.
And that slows us down from hypersonic speeds which is
around 10,000 miles an hour all the way
down to supersonic speeds which is two times the speed of sound,
about 800 miles an hour.
When we reach this supersonic speed
of roughly two times the speed of an airplane,
we pop a supersonic parachute.
That supersonic parachute is about 60 feet in size,
which if you think about it is
about the length of two school buses.
That supersonic parachute then slows us
down to subsonic speeds, which is below the speed of sound,
which is in the order of 200 miles an hour,
we separate from our parachute, and we start free fall.
So, the rover, attached to a little spacecraft
in the back starts to free fall towards the surface of Mars.
Then it fires a total of eight engines, which fire directly
into the ground to help slow it down even further.
We descend this way for about 4 miles
above the surface 'til we get just
about 60 feet above the surface.
Then we start to lower our rover on a tether or a rope,
and this maneuver is called the sky crane maneuver.
We continue to descend towards the surface,
and when Curiosity touches the ground at about just less
than 1 mile an hour, we then separate from this vehicle
above us by cutting that rope.
That little spacecraft flies off to the side,
and then Curiosity has landed, wheels down on the ground,
and is ready to start its mission on Mars.
[ Music ]
Our supersonic parachute is about 60 feet in diameter.
It's the largest parachute we've ever built.
We are deploying it or releasing it
at the highest speed we've ever built
and we are having it experience the greatest amount of load,
amount of force of any parachute ever has on Mars.
The parachute is made out of a material called nylon
and Kevlar.
So nylon, you could think of it as the material
that your backpack might be made out of
or that your tent might be made out of.
And Kevlar is actually the material
that bulletproof vests are made out of.
So the parachute is designed to be incredibly strong,
but also incredibly lightweight.
The parachute experiences a really interesting phenomena
during its flight on Mars because it's deployed
in this supersonic regime.
This is two times the speed of sound.
It actually tends to look like a jellyfish when it's flying
down because it's sort of collapsing and re-inflating.
So Mars represents a really unique environment
for our parachute to operate.
[ Music ]
The descent on Mars happens over such a short period of time
that we actually don't have any fail-safes built-in in terms
of being able to switch from one parachute to the next,
or being able to turn one engine on and one engine off.
So we actually have only one way of getting to the ground.
So for example, we have a single heat shield.
That heat shield has to perform as intended.
We have a single parachute.
That parachute has to perform as intended
and we do have these 8 engines and each one
of those eight engines have to perform as intended.
[ Music ]
Our Entry, Descent, and Landing system is completely autonomous,
which means that we're not communicating with it.
We're not telling it how to do that; it has the brains
on board, the computer on board to do that descent itself.
So sometimes when you hear people talk about EDL,
they talk about the seven minutes of terror
and what this is, is because there's a large distance
between the Earth and Mars, there is a delay time
between when we can communicate back and forth to each other
and so that can be anywhere from about seven to 14 minutes.
Now as a result, we actually don't know
that rover has landed successfully on the surface
until we've actually waited
for that communication to come back to us.
So after seven years of building, designing
and testing our MSL-EDL system,
we've got only one chance to get it right.
So we're looking forward to it
and we're confident we'll be successful.
We all know it was a huge success
and a major accomplishment for Dr. Sengupta and her team.
[ Sound Effects ]
The entry, descent, landing system.
What an incredible series of precise processes happening
at amazing rates of speed at vast distances.
Here's a project where you can test your engineering
design skills.
[ Sound Effects ]
Teachers, we have a great assortment of activities for you
and your students to expand your rocket science knowledge.
Look for the Adventures in Rocket Science link located
on the NASA Explorer Schools Virtual Campus.
[ Sound Effects ]
Well that's it for NASA NOW.
Visit our Facebook page and leave a comment.
Be sure to join us for another special episode during Mars
Month on NASA NOW!
[ Sound Effects ]
NASA Now comes to you from the Virtual Campus
at NASA Explorer Schools.
[ End ]