Kind: captions
Language: en
I'm at the Jet Propulsion Laboratory in
Pasadena and I'm here to see the first
drone that's gonna fly on another planet
it's the Mars helicopter so this is our
baby no way yeah that thing right there
is the actual machine that is going to
take off and land on Mars it's going
with the Mars 2020 mission that is the
Mars helicopter this will be the first
part like in another planet
now it's necessary to say first powered
flight because in 1985 the Soviet Vega
missions deployed two helium balloons on
Venus they transmitted data for over
forty six hours while floating at an
altitude of 54 kilometers in Venus's
dense atmosphere which at the surface
has a pressure of over 90 Earth
atmospheres in contrast Mars has very
little atmosphere only around 1% of
Earth's flying this kind of helicopter
is equal into flying a similar
helicopter on earth at a hundred
thousand feet so you don't know you
don't hear about many helicopters at a
hundred thousand I think forty thousand
feet is probably the record I checked
forty thousand feet is the record
altitude reached by helicopters on earth
85,000 feet is the highest a plane has
ever flown on Mars the air is even
thinner than that right in terms of
density is 1% of what you have in this
room so in this room a cubic meter of
air is about a kilogram yeah the same
cubic meter on Mars will be about 15
grams to 18 grams so that you have to
push a lot of air down yes you gotta
gotta get a lot of air flowing and so
the obvious trick if you will is to spin
the blades faster it can spend between
2300 rpm and 2,900 rpm that is fast it
is fast yes here I'm trying to work out
exactly how fast that is so I look it up
and on earth helicopters typically spin
their rotors at around 500 rpm so the
Mars helicopter will have to spin its
blades five times faster but there are
some limits you know you really really
don't want to get that tips of the
blades breaking the speed of sound can
shockwaves and you get all kinds of
funky
aerodynamics and you know the transonic
flows and things like that so you don't
want to go there so we in our designs
keep the tip Mach numbers down to below
about 0.7 so 70% the speed is very
conservative
one advantage of flying on Mars is that
gravity is only 38% of what it is on
earth even so making the craft
lightweight was essential keeping the
mass of this vehicle contained during
the entire design process has been the
major challenge every single part had to
be considered the entire vehicle is less
than 1.8 kilograms
well less than four pounds that's about
the same as this laptop the blades are a
foam core with carbon fiber layup each
of them is about 35 grams Wow yes it's
quite light yes
35 grams is the mass of six quarters
think about that - 35 gram blades
lifting an 1800 gram helicopter by
spinning 40 times per second in just 1%
of Earth's atmosphere how long can it
fly for it's designed to fly up to 90
seconds a minute and a half of flight
yes to me that sounds like forever when
you're talking about another planet
flying autonomously by itself in 1/100
earth atmosphere I mean come on
like that's a long time it is one of the
questions I had was why didn't they use
a quadcopter design well because on Mars
the blades have to be so long that the
whole craft would barely fit on the
rover two counter-rotating propellers
provides the simplest design they also
generate lift more efficiently when
stacked on top of each other the bottom
rotor sees the sort of the more
compactified flow the top one pulls it
the bottom one sees sort of a more
concentrated flow so the bottom rotor
actually can do better than if they were
separated apart but how do you test a
helicopter designed for conditions on
Mars on earth what would happen if you
just took your Mars helicopter and you
tried to take off on earth I would just
make a lot of noise really and it
probably wouldn't get the full head
speed either because of how much
atmosphere we've got exactly it's like
trying to swim in a thick soup we have a
really amazing chamber here on lab call
the 25-foot space simulator
and in that chamber you could simulate
any kind of atmosphere you want you can
go to Martian pressures you can stay at
Earth pressures whatever you want but
that only took care of half of the
problem that was the aerodynamics aspect
of it there's the other part which is
the gravity we needed a way to fake Mars
gravity here on earth and the best way
that we could figure out to do that was
a gravity offload gravity offload just
means pulling up on the helicopter so it
only has to support about 38% of its
weight just like it will have to do on
Mars and effectively was a high-tech
fishing reel so taking a brush DC motor
a reaction torque sensor and a pulley
mounting that couple stories in the air
and then attaching a fishing string to
the top of the helicopter that would tug
the necessary force required to offload
the differences in gravity an actual
fishing lines yeah
reel fishing line but isn't that
stretchy like don't you want something
that's perfectly rigid so as soon as you
apply the torque it gets applied to the
ground right right and we did a lot of
testing with different vendors to find
out which fishing line have the best
spring constant for us what does the
helicopter sound like I imagined that in
1% of Earth's atmosphere the helicopter
would be pretty quiet yeah you're still
at 1% but it's still real loud really
yeah we have audio recordings of it too
but it's it's I would characterize it
more like bad something like that
when gravity offload systems working and
the chamber was pumped down the
helicopter thought it was good stuff
how do you actually steer this thing
around and drive it so the way
helicopters work is they have something
called collective and cyclic so what
collectives do is they change the pitch
on the blades uniformly so throughout
the entire evolution you move the
collective the blades will change you
can change your angle of attack you'll
get more lift so that's basically what
you would provides you heat control
right you more you go up
less you couldn't you come down but then
there's something called a cyclic on
helicopters which basically what it does
is it it modulates the pitch as it goes
around so it can pitch it a little bit
more here less here so it kind of like
modulates so what that does is it
provides in asymmetric torque right when
you're pitched up there you get that
additional torque now you get it
depending upon the stiffness the system
you actually get it with that a
gyroscopic lag that can happen
afterwards so once you get an asymmetric
torque the vehicle wants to start
pitching or rolling all right so once it
pitches and rolls you're doing it stable
you are now pointed in a direction and
get respector now has a component that's
horizontal in the direction that you
pitched right so then you start
translating in that direction
I've heard that initially someone tried
to fly it with a joystick yes early
prototype if you were sitting right
there on Mars and we're trying to
joystick it what is it like and it's
almost on flyable and the reason for
that it's the aerodynamics of when you
want to command a roll to the left
because you see yourself starting to
move to the right and you start
commanding a rolls left there's a delay
aspect so that that delay effect makes
it very very difficult for a human to
try and pilot it you can't fly this from
Earth because of the twenty-minute kind
of time delay so you have to really send
sequences so essentially you're gonna
push a button and like 20 minutes later
it'll take off and do its thing and the
right you'll find out the way this flies
autonomously it has onboard gyros
unbowed accelerometers and onboard
camera an altimeter and an inkling
manometer and so using that sensor suite
real-time measurement you know against
terrain and of course the gyros and the
accelerometers sensing onboard the
real-time estimation of the state of the
vehicle is made continuously again you
know hundreds of Hertz and hundreds of
Hertz and then that's fed into the
closed-loop control algorithm that takes
the estimated state and then generates
the correction that's needed at the
blade level and then the blades are
continuously being controlled so when
you see video tapes of our successful
flights right and if the vehicle looks
calm is coming up and hovering and going
literally coming back you know the
machines are working very very fast and
very very hard it just looks very calm
but yes so the the blades are being
continuously controlled that is amazing
how will it handle a gentle breeze a lot
of the movies depict desktop is the big
tough storms as being very aggressive on
Mars the truth of the matter is that 1%
Earth's atmosphere is very little matter
actually hitting you oh I mean you're
using that to lift just exactly exactly
so obviously so there's enough to lift
right but we also need to spend at 2200
rpms to be in the ballpark of lifting
ourselves we built our own wind tunnel
that we put inside this 25 foot chamber
how many fans was it Teddy 960 computer
fans so but it does sound like a like a
jet engine taking off so we built a fan
wall array it's called an open
cross-section wind tunnel where you
don't need the walls just the fact of
having an array of fans we are very
confident of being able to go at 11
meters per second that you in this
vehicle if I had known that somewhere
along the way I'd be building of
internal to do this I would have
probably not taken the job on hey how
long does it take to recharge we can
recharge the whole day so circle day at
Mars right but does that mean that you
could do one flight a day kind of thing
in theory in there yes by design it can
what is the size of the battery between
35 and 40 watt hours total that's
equivalent to just three smartphone
batteries and get this most of that
energy isn't even used for flying it has
to survive temperatures as low as about
minus 82 minus hundred degrees C at
night
so we keep
the battery's warm and we surround the
batteries with our electronics board so
the electronic sports also stay warm
we take approximately two-thirds of
energy just keeping things warm and
warming things up to operate only
one-third of the energy is available for
flight
do you have insulation on there to keep
it warm yes when you look at that
helicopter right you have the solar
panel on top with antenna on the nexus
at rotor system and then bottom what you
see this cube is what we call the
fuselage you are seeing it now actually
uncovered because you're seeing the last
day of final you are recovering Cena for
delivery to be integrated onto the rover
okay so usually you won't be seeing that
so the center of the cube is the ring of
batteries okay there is space between
the battery and the circuit boards that
you're seeing and then there will be a
shell that we put on called the fuselage
shell and that will close like co2 the
gas around and so the enclosure itself
we're using the co2 gas as the
insulation material oh wow no aerogel no
aerogel we did it was in the it was in
the game it was it was in the
consideration in the beginning and it
turns out that just the co2 as you know
insulator itself was sufficient for us
to close our thermal model right and so
guess why we wouldn't want to use
aerogel if we have a choice wait now
before the helicopter can experience the
frigid conditions on Mars first it has
to get there and that's a reminder that
not only is this an aircraft it's also a
spacecraft it has to survive launch it
necessary have launched loads which you
know easily exceed about ADG no because
of the vibration vibrational loads are
atg yeah then it has to survive the
seven-month trip complete with radiation
and finally after pulling nine G's on
entry into the Martian atmosphere the
helicopter needs to be deployed this is
gonna be on the rover before you take
off does the rover like pick you up and
put you down somewhere we're gonna be
stowed underneath the rover on the belly
pan on our side and there's gonna be
several several sequences of firings of
explosive devices to actually
rotate his right side up and then drop
us on the surface for example the very
last thing the robot does is it's got us
by this bolt
it's holding us you know but this side
then it goes has to drop us right yeah
so how do you undo a bowl on on a
spacecraft you blow it up basically it's
a materials you know undergoes a phase
transition which certainly increases the
the stress in the metal part of the
thing and makes the board break it's
called a frangie bolt then once were on
the surface the rover drives over us it
gets about 100 meters away and then we
have about a two-hour counter internally
where we'll wake up after 2 hours wait
to hear some RF transmissions and if we
do get that link with the rover then
great our base station on the rover what
they should they fly now command first
flight will probably be a mutual selfie
rink this is after all the self eh I
think like that is the goal of the first
flight yes it is in fact no I don't know
the best time to fly this is that
Lebanon block in the morning local time
on Mars and that the reason for that is
we would have come out of the night
where we would have spent a lot of
battery power trying to you know stay
warm well having a clock the state of
charge would have gotten to the point
where you could fly without risking a
brownout on the battery and then you
know dropping the whole craft to the
ground also 11 o'clock is where the Sun
would have warmed up things so we don't
quite have to heat up as much and also
it's not late afternoon where because of
the warmth the density has begun to drop
okay and the winds have begun to pick up
now what we will investigate is after we
get the first couple of flights under a
belt I'm sure we will try to fly in the
afternoon and you know do more
exploratory things but the most
conservative thing we can do is to sort
of pick a mid-morning flight so what is
the purpose of this mission the Mars
helicopter is first and foremost a
technology demonstration to prove that
we can fly on another planet the
helicopter can take colour photos and
videos but its purpose is not to make
scientific discoveries instead it is to
help engineers figure out how to design
and build aircraft for future missions
you can imagine something that's about
30 kilograms carrying you know a two
kilogram science payload doing
exploration acting akka scout like a
small vehicle like this scouting ahead
for some future over or it could be a
gadget that goes and picks up some kind
of samples and brings it back to a
central Lander for more sophisticated
analysis or it could be a completely
standalone craft and maybe more than one
that are exploring places where humans
and Rovers can't get to easily polar ice
carves you know sites of cliffs and so
forth so the real emphasis here is to
try to get back all the engineering data
so that it can inform that future design
flying on other planets will provide a
new dimension in space exploration an
aircraft is faster and capable of
covering more ground than a rover and it
can provide higher resolution imagery
than an orbiting spacecraft so maybe one
day aircraft will be the Companions of
future Rovers or even astronauts
exploring other worlds
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