good morning welcome and welcome back to
those of you who've been here throughout
the series if you have been here
throughout the series you have seen
NASA's plans for the next 30 years or so
and the question is do we have to kill
you now
the answer's no this is the civilian
space program and and we work for you so
so you've seen the plan and for the last
two weeks you've actually seen the
program that's underway today to build
the transportation system to take people
into deep space today and next week
we're going to concentrate on two major
problems that that are between us and
being able to execute that plan you saw
the first week of going to Mars with
people and and Jeff Harith is here this
morning to tell you about the problem of
landing people on the surface of Mars
and how we go from interplanetary speeds
down to zero miles per hour safely and
last week we talked about the rocket and
how the rocket accelerates the people
the astronauts and their cargo out of
the gravity well that we live in this
deep energy well that we live at the
bottom of now that once the astronauts
are in space it's very easy to move
around okay only the only force you have
to overcome there is inertia and but the
problem is when you get to the next
destination you've got to take all that
energy the rocket put into you so now
you're speeding along at 25,000 miles
per hour and you got to slow down so now
you're going down the well and you've
got to do go down that slope that energy
slopes safely and that's what you're
going to hear about today
as you know at this point in time we
have ideas about how to do that but we
we can't say we've got the solution in
hand with that I'm going to turn it over
to Jeff Aerith who is the product line
lead at Langley for entry descent and
landing good morning yes oh good morning
everybody
i'm jeff Harith I work here locally at
NASA Langley Research Center and today I
get to talk with you about Mars and the
challenges of safely and affordably
getting humans to the surface of Mars
so first I want to start with an image
does anybody see anything there that you
recognize yell it out alright so you got
the moon and if you can see a little bit
further down there's this tiny little
red dot that is what Mars looks like in
our night sky from here at Earth and in
fact you know from the earliest days
when humans could first look at the
skies they noticed this strange red
light that moved a little differently
than the other stars and so we've been
looking at Mars and wondering about Mars
for an awful long time and as we move
forward we develop new technologies such
as telescopes and we're able to look at
and see Mars in a lot more detail and in
fact over time if you look at the
history of observing Mars you have
people in the 1600s able to determine
that Mars had polar icecaps you had also
there's early observations they were
able to determine the inclination of
Mars or the tilt of its rotation and
then you get into the 1800s and the late
1800s they could see more surface
features and they determined that these
were canals that were built by an
intelligent species on a dying world and
that was in 1894 this was this was the
thinking at the time now of course now
we know that that's not actually the
case but Mars really is a very
interesting place to study so Mars is
the fourth rock from our Sun and is
named after the Roman god of war
Mars is half the diameter of Earth but
twice the diameter of Earth's moon
and in fact if you look at the land mass
of Earth you know took out all the
oceans it's about the same size as Mars
and like Earth Mars has seasons it has
polar ice caps as volcanoes has canyons
as deserts and weather and some of the
things on this start like I mentioned
the inclination in that last slide
Mars is inclination on its rotational
axis is 25 degrees very similar to
Earth's at 23 degrees its day the speed
that it rotates at Earth were 24 hours
at Mars it's only 240 minutes longer at
24 hours and 40 minutes now the gravity
on Mars a lot less it's a smaller planet
so if you weigh a hundred pounds here on
earth you're gonna weigh 38 pounds on
Mars which sounds really good to people
like me yes so and the other thing as
Mars is further away from from the Sun
and so only about 44 percent of this of
the energy that Sun energy solar energy
that reaches earth reaches the surface
of Mars and then next big thing would be
its atmosphere it's got very little
atmosphere compared to earth about one
percent and the composition of that
atmosphere is quite different about 95
percent of its atmosphere as carbon
dioxide we're here on earth that's a
very small percentage on earth we have a
much higher percentage of nitrogen and
oxygen that makes a far air now the
average temperature of Mars is minus 64
degrees Fahrenheit so it's kind of
chilly and but the ranges are if you go
from night at negative 200 degrees
Fahrenheit but then in the hottest days
at the equator it can actually get up to
80 degrees Fahrenheit on the surface and
as I mentioned Mars atmosphere is really
thin in fact it's too thin for liquid
water to survive on the surface it
sublimates directly to a gas so but
however several Mars missions have found
evidence of past water in the Mars icy
soil and in its thin clouds and we'll
talk a little bit more about that
so why Mars well Mars is the most
earth-like of the planets in our solar
system and so by studying these
different areas we're looking at the
history of the climate looking at its
geology we're looking at whether life
could have or ever did arise on Mars and
then also evaluating it for the
potential for human exploration so these
are some of the key areas that were
really interested in looking at Mars for
there's one thing that ties all those
together and that's water understanding
the water on Mars and that is why when
we and the Mars exploration program
where we when we reinvigorated that in
1996 with the Mars Pathfinder mission
the strategy has been to follow the
water and understand the role of water
and we've sent several missions there
and in fact I'll show you a couple
highlights of those here in just a
minute
and so the Mars exploration program is
moving from follow the water in to
looking for the signs of life and
looking for the possibility of human
exploration of Mars so a few highlights
of our relatively recent explorations of
Mars so if we go back to the Mars
exploration Rovers these were the
rover's Spirit and Opportunity they were
sent there one of their main questions
was the answer was there water on Mars
and they definitely answered that Mars
was once soaked in water in fact in this
this slide when I'm showing here these
are perchlorate salts that it found that
can only form in the presence of liquid
water and in fact these particular type
were nicknamed blueberries just because
of their shapes but the Mars exploration
Rovers found seven different types of
formations types of minerals that could
only form in the presence of significant
liquid water so then we move on to our
Mars Reconnaissance Orbiter mission this
particular mission had a
ground-penetrating radar as well as a
very high-resolution camera on it so
what we're able to do with that
ground-penetrating radar if you look at
this is a global map of Mars and we're
looking at the concentrations of h2o or
water within the relative about one
meter up to two meters within the
surface of Mars and as you get as you go
from the yellows into the blues and
Indigo's it's more it's higher in higher
water concentration and so what we prove
with the Mars Reconnaissance Orbiter is
that there is significant water on Mars
particularly toward the polar regions
but there is significant water what we
didn't know is how that exists on Mars
is it large chunks of ice under the
surface is it actually could be lakes
under the surface or is it just loosely
distributed all through the soil or in
different types of minerals so from our
remote sensing we couldn't tell that we
just knew that there was a significant
amount of the out of the element h2o on
underneath the surface and in fact the
estimates are if you brought all of that
water to the surface it would cover the
surface of Mars about six feet deep the
entire surface so it's a significant
amount of water so what we did then as
we took the Phoenix lander so now we
knew there was water there but we didn't
know as I mentioned what form it was in
so we launched Phoenix and set that to
Mars and landed it in the polar region
and one of the things we noticed right
away from one of the first images back
right after landing this is underneath
the lander you'll see that the landing
rocket sort of cleared away an area and
there's this nice shiny smooth surface
there sorry for is that ice what is that
you know so we took the the arm which
has a shovel on the end of it out right
beside the lander and dug just a couple
inches in and so what you see here this
white area is actually frozen carbon
dioxide or dry ice now remember Mars has
a lot of carbon dioxide so there is an
awful lot of dry ice on Mars but what we
also found which is hard to see in this
bottom left corner it's blowing up there
are these other little chunks and then
within a few hours of that they actually
disappeared so the water sublimated all
right so we dug later brought those up
into our ovens and our sensors and were
able to prove that that was water ice
rick very easy to get to within the
surface of Mars so they're they're
significant water of Mars it's it exists
as ice within the soil as well
potentially deeper down it could be
liquid water we don't know that yet but
there is significant water on Mars as I
mentioned what's the next decade so
we're moving from follow the water to
looking for the signs of life
and that's what our latest mission that
you may have heard of our Science
Laboratory is part of that transition
with the Mars Science Laboratory we
landed the Curiosity rover there about
two years ago and it's beginning this
work of looking for the signs of life
now the most important discovery by
curiosity so far is that ancient Mars
did have environments that could have
supported life if life had arisen on
Mars their environments there as light
light that life as we know it here on
earth could have survived so it looked
at the concentrations of carbon hydrogen
nitrogen oxygen phosphorus and sulfur
they're all there in the right
concentrations they also found looked at
the mineralogy and the Clay's that were
formed in that area and found that there
was significant freshwater actually not
very salty water at all and in fact they
believed if we had been there we could
have dipped a cup in the water and drink
it without any issue so Mars did have
Hobart habitable environments we do not
know to be clear we do not know if life
ever arose or currently may exist on
Mars but we do know that there used to
be environments where it could have all
right so curiosity is really the
monster-truck of Rovers if you look here
these are the other Rovers that we've
sent to Mars our very first one here
with Pathfinder and then the Mars
exploration Rovers and then the Mars
Science Laboratory at about one metric
ton and that one metric ton represents
the limits of our current entry descent
and landing capability so this Rover is
the biggest thing that we know currently
how to put down on the surface of Mars
and that's based on significant
technology investments that were made in
the 60s and the 70s leading up to the
Viking missions in the Viking program
there have been we humans have sent 40
missions to the surface of Mars from
Earth many of those have failed it's a
very hard place to go and in fact if
you're keeping score we've had 16
successful missions versus 24 failures
from Earth but since we're talking about
landers today we've had seven successful
Landers
and we've had eight that have failed so
let's start talking about what it takes
first - how do we get to Mars now you
all had a presentation on the Space
Launch System I believe it was last week
and so the first thing you need and we
won't go into detail because you worry
about that is a big rocket right and
this is the SLS and it begins with a 70
metric ton capability and will grow to a
hundred and thirty metric ton launch
capability and so let's talk about a
little bit about how to launch effects
entry descent and landing so with your
big rocket that leaves you have to
package your payload up on the top of
this rocket inside of a fairing now that
fairing size is limited by what the
rocket can launch and the aerodynamic
loads that are going to be on it and its
purpose is to protect your payload
whatever we're wanting to send to Mars
from the atmosphere of Earth as we're
trying to push through it really quickly
but the size of that fairing limits the
size or the diameter of the vehicle that
we can send to Mars and so why is that
important entry descent and landing well
the larger diameter vehicle that we can
get to Mars the more drag we can create
as we're trying to enter that atmosphere
and slow down and therefore more mass we
can get to the surface of Mars but right
now with our current limitations as I
mentioned before we're limited to about
one metric ton to the surface of Mars
so with that fairing up there we have
our vehicle packaged in it we launch we
accelerate after we get out of Earth's
atmosphere we drop the fairing we now
get up into orbit we check our orbit and
then we ignite the engine again to
accelerate ourselves to escape velocity
and get us on the right trajectory
headed to Mars and that's when we move
from leaving Earth into what we call the
cruise phase so we go from launch and
departure to the cruise phase and cruise
is where we are traveling from the earth
vicinity to the Mars vicinity and now I
have a short video here that describes
how we do that how do you get to Mars if
you want to send a spacecraft all the
way to Mars first you'll need a fast
rocket to escape the pull of Earth's
gravity the heavier your spacecraft the
more powerful your rocket needs to be to
liftoff next make sure you
launched at the right time Mars and
Earth orbit the Sun at different speeds
and distances sometimes they're really
far apart and other times they come
closer together about every two years
the two planets are in perfect positions
to get to Mars with the least amount of
rocket fuel that's important the total
trip is over 300 million miles finally
make sure your aim is right
you can't shoot for where Mars is at
launch time you have to aim for where it
will be when you get there it's a lot
like how a quarterback passes a football
also you may need a few frust to correct
your direction along the way so you
don't miss Mars if all goes well you'll
get to the red planet in about seven or
eight months so here we are we've we've
gone from Earth to Mars we've arrived at
Mars and this is what planet looks like
as we get there and we're getting ready
for entry descent and landing now one
thing I mentioned from the cruise a lot
of people the analogy for that is to
getting as accurately as we need to to
Mars is like making a basketball shot
from New York to Los Angeles now as it
said in that video we're able to cheat a
little bit because we can make small
corrections on the way there but we have
to get we have to get a very accurate
departure from Earth and we've been able
to do that very well the last several
missions and so that that is working
really well
so here we've arrived at Mars this is
what it looks like as we're starting to
get pulled in to Mars gravity well it's
accelerating the vehicle toward Mars and
so we're ready to start introducing and
landing but what really is entry descent
landing and so it is introduced in
landing is about the controlled flight
of the vehicle system through all
appreciable atmospheres including the
city including the safe landing where
that's applicable and so we have to get
from here where in this case relative to
Mars we're going about 13,000 miles an
hour down to the surface and in this
case I'll show you what the the target
was the Gale Crater
this was our landing site for MSL and
what it looked like from as we arrived
at Mars and we have to get from that
13,000 miles an hour down through the
atmosphere to the surface to roughly 0
miles an hour for a nice soft touchdown
that's what you want once you've
committed the EDL you're going to
touchdown now hopefully we don't make
another crater but
we want to touch down nice and softly so
let's talk about what the key challenges
are for doing that the first is at Mars
there's too much atmosphere to land like
we do in the moon so what that means is
we're traveling so fast and as we start
interacting with this atmosphere that's
there there is an awful lot of force on
the vehicle there's an awful lot of
heating on the vehicle and the the
atmosphere itself has different winds
has density variations and so all of
these things conspire so that we can't
just do a propulsive descent like we do
at the moon you actually have to use the
atmosphere the next is that there's too
little atmosphere to do it the same way
we do at Earth there's only about 1% of
Earth's atmosphere at Mars and so that
would be kind of like landing the the
Space Shuttle at a hundred thousand feet
here at earth it was just not enough
atmosphere to do it that same way some
of the other challenges are there is a
wide variety of terrain elevations as
well as the types of train to deal with
when we get to the surface and then we
have this issue of we design an EDL
system or an entry descent landing
system here at Earth but we don't have
good ways to test that end to end here
at Earth to test the entire system and
it has to be done at Mars and so that's
a huge challenge for getting a system
that will be reliable and actually work
when we get to Mars so first let's talk
about the atmosphere like I said it's a
very dynamic atmosphere and it's poorly
characterized to date now there are no
large storm systems like we have here at
Earth but the seasonal and the diurnal
variations are actually larger than what
we see on earth and there are large
sometimes global dust storms and that
has huge changes on the density of the
atmosphere and changes how we fly
through it and actually on Mars they're
even dust devils so in this case you
know the Sun can heat the Martian
surface and create winds and sometimes
those winds create dust devils this
particular one was captured by the
hi-rise camera on the Mars
Reconnaissance Orbiter and then we we
created a three-dimensional model of it
so that we can kind of you know fly
around up kinda like you're in a
helicopter
and what you can see here this dark line
on the surface is actually the shadow of
the dust devil which allowed us to
recreate its height and so what you're
able to see from MRO we'll go back to
the original image is that the dust
devil is about a hundred feet wide on
the surface and about a half a mile tall
so it's quite a large one but one of the
things we didn't know before sending the
mars exploration rovers is how prevalent
how common dust devils are on the
surface I don't know if you'll remember
but the those exploration Rovers when we
sent them were only designed for a 90
day life because one of the main reasons
is we thought that dust would collect on
the solar cells and they wouldn't be
getting enough energy to keep themselves
warm and their electronics would fail
turns out dust devils are pretty common
so you can watch their battery life
going down down down and then it gets
hit by a dust devil and cleans off the
solar cells pops back up so now we've
had we've had these exploration Rovers
up there for many many years back they
had their ten-year anniversary
it'll be good one of them is no longer
operating but the opportunity is
actually still operating on the surface
so the point is that the vehicle system
that we're trying to get to the surface
of Mars has to contend with a lot of
atmospheric variability so now let's
talk about the terrain elevations this
is a global map of Mars again and what
we're showing here the black areas are
the parts of Mars that are above two and
a half kilometers in altitude and so
this is the type of access that we'd
like to have to Mars we'd like to be
able to land anywhere the colors are on
this map and what you see here the red
X's are where we have landed and so if
we now look where those actually are
those have actually been all very low
altitudes with our current technologies
and our current entry descent landing
techniques we have to land very low at a
very low altitude so we have as much
atmosphere as possible to work with to
slow the vehicle down and get it safely
to the surface and so this is one of our
big challenges so they're also different
types of terrain hazards Lister you got
mountains craters canyons rocks right
but the point is we do know a lot more
now than we used to so if you look here
in the viking era at the same scale we
really couldn't tell anything about the
surface and then the Mars Global
Surveyor camera hey we could see there's
actually a crater there but can't tell
much more in these days now with our
high-resolution camera on Mars
Reconnaissance Orbiter we start being
able to pick out features in terrain
types and understand better where we're
actually sending these vehicle systems
and can better prepare them for where
they have to land
I mentioned the EDL system verification
problem so it's really because of the
complexity and the environments that
we're sending it to the EDL systems for
Mars generally can't be tested as flown
here at Earth as we intend to fly them
here at earth so we do component tests
here at earth to build models of how the
different pieces of the entry descent
landing system work and then we assemble
those models into an end-to-end
simulation and so all of the models of
the EDL component subsystems are brought
together into this in the end system
simulation so you have models of the the
vehicle mass properties you have models
of the atmosphere that we've been
talking about you have models of the
parachute understand the dynamics when
that when that deploys even get into the
the physics based modeling of the radar
system to understand what kind of
signals you're going to get back from
when and how and how much dust and
material is going to be kicked up as you
get close and how the radar will react
to that so there are a lot of different
models that get pulled into this and the
simulation exercises both the flight
vehicle and the algorithms that
autonomously fly the vehicle in the
virtual environment and that's one of
the things that actually these
simulations are very good at we can push
the system beyond even what were
intending it to fly through we can find
its sensitivity so we we dispersed
different variables such as how well we
know the vehicle center of gravity or
how much wind it might encounter and
that way we can understand better how
this system will perform when it
actually gets there now we run literally
hundreds of millions of these entry
descent landing runs in computer
simulations in the development and the
verification of these
systems and actually now these systems
are so complex that the only complete
system performance verification are
these Indian simulations so let's take a
quick look at what the entry descent and
landing sequence at Mars looks like
alright so we arrive at Mars and we've
had a crew stage which is that little
thing up on the top there attached to us
and helping us get from Earth to Mars
accurately well we we jettison that and
then we turn the vehicle to face the
Mars atmosphere at the angle that we
wanted to to hit the atmosphere and then
in this case I'm showing the the Mars
Science Laboratory sequence we jettison
a balanced mass this is important
because we now have changed the balance
of the vehicle and we do that on purpose
so that when we start flying through the
atmosphere the vehicle won't just fly
straight in like a bullet it'll it'll
fly at an angle of attack it will fly at
a slight angle and that gives us a lift
vector and so we can use that lift
vector to then control and steer the
vehicle and help us slow down or I'll
talk about that some more in a little
bit so we've just in that balanced mass
then we come slamming into the
atmosphere at about 13,000 miles an hour
it starts heating so that heat shield
the rigid heat shield upfront is
protecting us from that it gets up to
about 3800 degrees and then we continue
going through that peak heating and then
we reach peak deceleration which for MSL
was about 10 G's so now think about that
in regards to humans right we can't we
can't subject our humans particularly
after being in space for a long time -
10 G's so we're gonna have to for humans
slow down a lot earlier and slower right
but for our current state of the art
it's experiencing 10 G's and then we
start maneuvering essentially doing s
turns in the atmosphere to help us slow
down and as we get down closer to Mach 2
we can deploy the supersonic parachute
which helps us slow down a lot more we
drop the heat shield the radar system
then is looking for the surface to find
out exactly how high we are and how fast
we're moving and once it finds that it
drops the
and that our payload in this case for
this mission it was the rover on with a
rocket pack actually called the powered
descent vehicle and it continues slowing
down relative to the surface and touches
down so that is the current state of the
art for entry descent landing at Mars
and I'll show you a little bit more
about that in a few minutes but while
flying through the EDL sequence the
vehicle system needs to be able to land
within a defined area now I showed you
what Gale Crater looked like from orbit
before here's a close-up of it so this
was the the landing area for that Mars
Science Laboratory mission and we
targeted Gale Crater but that was
impossible just a few years ago because
like with when we did the Pathfinder
mission its landing uncertainty was
larger than the crater itself right but
we've gotten a lot better since then and
so here's the landing ellipse or the
landing uncertainty they call it for the
Mars Science Laboratory mission so after
all the calculations we do in
understanding how this EDL system will
perform we're very confident it'll land
somewhere in that ellipse the target of
course is the center and in this case
for MSL we actually did pretty well we
were only about two kilometers away from
the very center of that ellipse but the
point is for humans we need to delete be
able to land in an area that's ten times
smaller than that even so within about
0.1 kilometers of our targeted landing
area so let's take a quick look at how
the sort of the history of entry descent
landing at Mars
I mentioned the Viking mission so Viking
sent two probes to Mars they were
Landers they entered with a rigid 70
degrees fear cone era shell and went and
had a supersonic parachute to a
propulsive descent on the surface now
this was all possible this was the first
landings at Mars right so this is all
possible because of the significant
technology development activities we had
in the 60s and 70s the whose activities
made it possible for us to understand
the 70 degrees fear cone air shell on
how that was going to fly it qualified
this disc gap band supersonic parachute
so that we would be able to use that as
well as the autonomous propulsive
landing
so if we look at some of the more recent
missions Mars Pathfinder it landed a
small Rover there used airbags and I'll
show you that in just a second
Mars Polar Lander was another Lander
sort of like the Viking air but we lost
that one we don't know exactly why but
through the mishap investigation the
most likely scenario was that it's it's
computer was listening to it's touchdown
sensor too early
so it's this touchdown sensor is looking
for a shock
it touches down on the surface to turn
off its landing engines and so what most
likely happened is it's listening to
that too early and then it deployed its
landing legs and shocked the system and
the little sensor thought it had touched
down it turned off the engines and most
likely fill the last 60 meters to the
surface so we then did the Mars
exploration Rovers and so let's let's
take a look at their ETL architecture so
again we have a 70 degrees fear cone era
shell separate from the crew stage and
we're coming straight in to over
ballistically into the Mars atmosphere
so that heat shield protecting us from
the era heating
when going through peak heating and now
peak deceleration and as we get down
closer to Mach 2 because an employee
that's supersonic parachute you know
this we're still flying relatively
horizontally let's play put the
parachute
the parachute is actually working on
slowing us down and sort of tipping us
over and then we can draw the heat
shield right and then here is where it's
different than what we saw before it has
the payload when this tetrahedron
hanging down below and that tetrahedron
has airbags all around it which will
inflate as we get a little closer to the
surface and so those are just like crash
the airbags for your your crashing right
so and as we get within about thirty
meters of the surface these retro
rockets fire bring the entire system
closer to zero miles per hour ropes up
to the surface and then drops it and
that that system that airbag system hits
the surface at about 54 miles an hour
and then bounces along until it stops
now the actual emissions this is a
simulation than the actual missions they
bounced about 30 times before they
stopped and then it deflates the airbags
and then opens the tetrahedron and you
have your payload safely on the surface
of Mars in that case it was one of the
exploration Rovers yes so similar even
it's a rigid heat shield the material
the actual thermal protection system on
the latest ones is called pica and
that's different for the Apollo ones it
was called avcoat so it's a different
material but the same type of idea with
that rigid aeroshell and creating the
shock in front of the vehicle to carry a
lot yeah it bleats it's an ablative as
what's called you burn off part of the
heat shield material exactly yes
the question was how do you avoid
landing on a steep hill or incline and
so one is we characterize how well the
system can do that like what type of
incline could it withstand right and
then we've used our current orbital
assets there to create what are called
digital elevation maps of the area that
we're going to lay on a wide area and so
we understand where these these keep-out
zones are and so we define our landing
ellipse away from all of those bad areas
yes so yes so the balloons were a
composite material its ability was based
on a Kevlar based and then it had a
essentially a gas a gas barrier and
inside to allow it to inflate but they
had a very tough exterior that I believe
was Kevlar based yeah and so we did an
awful lot of testing of those dropping
them on sharp rocks and throwing them
sideways at things to make sure that
they wouldn't rupture within the
parameters of what we were playing or
how we were landing exactly for humans
to Mars we need to be within about a
hundred meter ellipse or 0.1 kilometers
right now we've got about a 4 depending
on depending on lots of things that's
between a 5 & 10 kilometer ellipse what
that we can land in so we're over an
order of magnitude away from where we
need to be and our landing accuracy so
then we had mentioned the Phoenix
mission before and so this is now a more
a modern Lander but still in the same
type of architecture that we did for
Viking so 70 degrees fear cone getting
through the heating same type of
supersonic parachute going to a
propulsive descent and landing which was
which was successful and so now the most
recent one we have is the Mars Science
Laboratory which was landing the
Curiosity rover on the surface of Mars
so this represents the state of the art
so we'll watch how
we got to the surface with MSL so again
same type but much larger same type of
rigid aeroshell drop the crew stage we
now reorient this entry vehicle toward
the atmosphere of Mars we drop that
balance mass member slowly offset so
we'll fly at an angle of attack and so
now we start to get into the sensible
atmosphere alright so the vehicle starts
to feel deceleration it uses rockets
call it a reaction control system to
keep itself oriented correctly and then
here you can see we've done through peak
heating and it's starting to steer back
and forth and these s terms continuing
to slow down gets through peak
deceleration which again for MSL was
about 10 G's and so now we're continuing
to slow down and as we get close to 2 we
kick off board mass to recenter
ourselves we don't want to be offset any
more silly can safely deploy the
parachute which there's that supersonic
parachute again the same style this gap
band that we providing but much larger
so now we dropped the heat shield and
the radars looking for the surface and
once it finds the surface and a solution
it's going to drop the rover and the
powered descent vehicle which is the
rover's rocket pack they fire and
continued accellerating the rover
relative to the surface one of the first
things it does though is a big left turn
to get away from the parachute so it's
the parachute avoidance maneuver
and so it's moved away from the
parachute now there's radar system up
front there it's continuing to look at
the surface and understand how we our
altitude and our velocity relative to
the surface and as we get closer there's
an instrument called the Marty
instruments a camera right here that's
also looking at the surface and
comparing features to understand how
much we're moving side-to-side that's
what it's doing there and so now as we
get closer to the surface we lower the
rover on the tether system below this
rocket pack and it continues
decelerating very slowly toward the
surface now and the rover has set its
wheels into a landing configuration
and right now the everything is just
waiting for this touchdown sensor and
once it since it's touchdown it cuts
those tethers and the car doesn't
vehicle flies away to a safe distance
and crashes by the safe distance away
from the rover and one of the big
benefits of landing this way is you've
now got your Rover system on the surface
essentially ready to go all it has to do
is stand up it's remote sensing mast and
it's essentially ready to go as opposed
so the relating that to is the Mars
exploration Rovers that were packed in
that airbag tetrahedron they were folded
up like origami and it actually was I
think it was almost three weeks of
operations to unfold everything and get
them set up and actually ready to ready
to operate and so here we've landed
within our landing ellipse and there in
the back is that it's called Mount sharp
it's the center of that Gale Crater that
we we talked about and it has been it's
been operating for just over two years
and has just now gotten over to the base
of Mount sharp now it's done an awful
lot of science on the way there we've
we've learned that there were small
rivers that even at least knee-deep you
know in that particular area and I'm
again I mentioned the the big discovery
for MSL is the existence of ancient
habitats that could have supported life
so it's done a lot so the point is that
this is the limit of what we can
currently do with our current entry
descent landing technologies and so we
have a significant technology gap look
just along the bottom here this is too
much too many words on the slide but
where we are currently is able to put
one metric ton within about a 10
kilometer ellipse and access about 40%
of Mars surface and so where we need to
be potentially for human missions is
able to land 40 metric tons within a
tenth of a kilometer of our target and
have nearly global access and so it is a
huge challenge it's why ADL at Mars is
considered one of the two biggest
challenges for human exploration of Mars
the other one being radiation protection
which you'll hear more about next week I
believe but nASA has set the goal of
having humans
Mars and the in the 2030s and to
accomplish that we're gonna have to
leverage activities all around it's a
very success or even a goal to be able
to do that within 20 years most entry
descent landing capability roadmaps so
you have to have a consistent effort
over 20 years for us to be able to get
there and so we're going to be
leveraging our international partners
and commercial partners to get their
other missions within within NASA that
aren't just the human exploration
portion of things like our science
Mission Directorate and the missions
that they send the various planets all
of these things are going to need to
combine to help move us stepwise closer
to humans on Mars yes okay yeah so the
question the question is during the
entry when when the the very high
heating portion of entry does Mission
Control lose the radio contact with the
vehicle in control what you think so
first of all we're about communication
time wise we're about 14 minutes away so
the vehicle is actually working
autonomously that whole time there's not
any active control so from the time
we've started entry at Mars right so
when we get that signal 14 minutes has
gone by from the time and it actually
started entering and so it's either
safely on the surface or crashed by the
point we get that signal that it started
okay so but but what does happen during
that entry we there is some radio
blackout and there there are special
radios we use that are very small data
pipes that send us some very small
amounts of data all during that time and
so it's all about the health of the
vehicle and if we have a bad day helping
us understand what happened so that has
that well there's sorry yes the the
question was what causes the radio
blackout it's the ionized flow so we're
slamming into this atmosphere and we're
hitting it so hard that we're
disassociating the species and creating
ions heavy ions and a plasma flow and so
that then surrounds the vehicle
the radio leaves can't get through right
yes so the quick yeah so the question is
is the United States the only nation
that has actually put Landers on the
surface of Mars we're the only ones that
have done it successfully
so there have been Russian Landers the
closest one they believe they got a
signal that had landed but they lost
contact immediately so we're not quite
sure most of the others failed during
launch or failed during during EDL and
there have been European smart Landers
that also failed during the attempt so
the u.s. so far is the only one that has
successfully landed on Mars the mission
so are the missions coordinated with
other countries yes in that even on like
MSL here is an example there are
contributed instruments on the mission
from other countries like France and the
European Union yep absolutely thank you
so landing at Mars is not easy as we
just said we've landed a total of seven
times successfully on the surface of
Mars the point is all of these
successful landing systems have landed
at low elevations at minus one kilometer
or lower we've landed less than one
metric ton and there's been relatively
large uncertainties on our landing
location and this the EDL system so
critical to the overall mission that it
generally drives the mission
architecture and as I've mentioned all
of the current Mars missions have relied
on the technology investments in the 60s
and 70s and we've essentially gotten to
the end of where we can stretch those
technologies where we can go so there's
going to need to be systemic new
investments in new atmospheric flight
systems that are the basis for these
entry descent and landing systems
because that really is the core of EDL
is being able to fly these vehicles
through an atmosphere so the agency has
started working on some technologies
remember we mentioned in the beginning
that we don't have the answer right now
I'll talk about some of the things that
we're working on
so we've developed new thermal
protection systems these are the
materials on the front of the vehicle
that protect you from all that high
heating we've got some new deployable
Aero shell concepts that we're working
on in developing there are mechanical
deployables and there are inflatable
aeroshells now remember the inflatable
aeroshells I'll talk about those in more
detail here in just a few minutes and
then we have what are called the mid l /
D where that's mid lift / drag vehicles
these are more like flying cylinders
into the atmosphere and then we're also
developed new parachutes new supersonic
deceleration systems these systems
actually inflate inside the atmosphere
and create more drag and we're also
working on supersonic retropropulsion
and this is essentially you're in a
supersonic flow and you're gonna fire a
rocket into that and help yourself slow
down and so that is another key one and
then of course the the landing systems
from propulsive systems to airbags to
crushable structures being able to
actually safely set down on the surface
so how do we put these technologies
together for humans to actually get to
and explore the surface of Mars so nASA
has done a lot of studies this I'm not
expecting to go through in detail but
this is looking at different
combinations of these technologies and
we're running simulations to understand
how those might work and which ones are
more effective and one of the key
figures of Merit is the arrival mass at
Mars how much stuff do you have to get
from Earth to Mars for this type of
system to work in this study was done
around getting a 40 metric ton payload
to the surface and so in comparing this
we end up actually with architecture
number two winning out it had a very low
mass at Mars so around 84 metric tons
but you'll notice that there is one over
there number eight that's a little bit
less in mass but it's EDL sequence has
many more critical events and it's a
little more risky and so we ended up
saying that architecture 2 is a better
way to go and so that's the thing if we
were to pick today how we were gonna get
humans to the surface of Mars this is
the architecture we would take which is
using an inflatable aeroshell
I'll talk about those in just a minute
using a narrow capture approach again
this is using the Martian atmosphere to
help yourself get into orbit I'll talk
about that as well and then
transitioning to supersonic
retropropulsion and final touched on
autonomous propulsive touchdown as well
so looking at this architecture we don't
see any cliffs we see that it can scale
to the human class missions now there's
a lot of work to get there but there's
nothing that says that it can't be done
so let's talk about some of those
technologies I mentioned the error
capture so this is when the vehicle
system uses active control to
autonomously guide itself into in this
case the Martian atmosphere flying
through that and if you're taking a lot
of energy out and slowing down but then
fly back out of the atmosphere into
orbit so you haven't you didn't have to
carry a bunch of rocket fuel to slow
yourself down to use the atmosphere and
this allows you to use a smaller more
affordable launch vehicles to get the
system there it also allows you to have
a higher payload fraction meaning since
you don't have all that propulsion or
propulsive capability that you brought
with you you can have more payload and
the example here if you're really using
air capture you can have 80% of your
vehicle system your payload as opposed
to if you're doing propulsive it's about
20% so it makes a big difference in the
architecture studies so we need to slow
down more mass at higher altitudes we've
talked about right so the limit of that
fairing size for the size of the
aeroshell that we can bring to mars and
help us slow down is a big limit and I
just have a small image here on that but
this is supposed to represent the rocket
fairing and then that was the MSL shape
and it was as big as we could make it
but if we used an inflatable approach
which here it is stored and here it is
deployed we could carry with us and I
mean we stow it and launch it in an
everything and then we're able to deploy
it or inflate it as we get to Mars and
it's a much larger drag area so the
anatomy of this you have an inflatable
structure there's two main things
there's an inflatable structure and
there's a flexible thermal protection
system the inflatable structure
and both of those by the way in this
case are packed very tightly and forward
of this so you have this nice narrow
vehicle alright so when it inflates it
creates the it uses an inflatable torus
approach or stacked torus approach and
they're straps that halls together and
carry all the loads and I don't want you
to think when I say inflate I don't you
to think balloon right so how people
think of these balloons and they're
squishy and stuff like that this is
actually quite a rigid structure once
it's inflated even with just a few psi
differential and the material is very
durable it's a Cylon base material kind
of like kind of like Kevlar it has a gas
barrier on the inside and all of these
are made to be high temperature material
systems and so so we have that as the
structure but then you know when we when
we come slamming into that atmosphere
we're at 13,000 miles an hour it's going
to get really hot so we need this
flexible because it's gonna be folded up
this flexible thermal protection system
to go on the outside of it and that's
what I guess here so that's a pinkish
material along the outside and that's a
material system that can stand up to
those really high temperatures and so if
we're able to do this it allows us to
land if you remember these images those
are that's our current access it allows
us to be able to land either more mass
to the same areas or the same mass to a
much much higher altitudes and have much
more access to the surface of Mars so
what I want to show you now is a video
of a technology demonstration of this of
this technology and it's that's from a
mission called Erb III or the inflatable
reentry vehicle 3 and it shows the
vehicle system you have the actual video
from the test here this was on the
vehicle and this is an animation showing
kind of what it's doing at the time so
we got to about 291 miles high that's
higher than the International Space
Station we then release the heat shield
and start inflating it and you can see
it's come here in this this Green Line
is its full shape you can see the
inflatable Tauruses and the straps and
then it reorients itself toward the
atmosphere of Earth so that as that
earth gravity well is now accelerating
us from pulling us back down into the
atmosphere
there are sensors on the front here to
indicate you know how high the heating
gets and things like that because we're
testing this material system and then we
also have a new way of creating a lift
vector this instead of dropping mass off
we just shift our payload mass within
this does the same thing of sort of
unbalancing this so that when we fly
into the atmosphere we can get a lift
vector and so here we go into the
atmosphere at Mach 10 the seller eating
and heating and look at this I mean it's
flying very steadily it's hard to even
tell that's what's happening over here
it experienced 20 G's of deceleration
because we were trying to really push
the system and get as much heating as we
could in a real mission that would never
see actually 20 G's but it was a very
successful test and it qualified this
particular material system which we call
the Gen 1 material system to 30 to 40
watts per centimeter squared and what
that means is it would be relevant to
the the MSL class missions that we send
that we're working on right now but we
want this type of system to be able to
work for human class missions and that's
kind of that's the next step that we're
working on we have not done this test
yet but we've started working on it's
called Thor the terrestrial high ed
orbital re-entry test so we're gonna
launch on a much bigger rocket and go up
higher and faster we're actually
catching a ride with Orbital Sciences
Antares rocket and so as they get up
into orbit will drop off and they'll
continue on to the International Space
Station but what they've done for us in
the partnership is they've gotten our
system up to really high velocities and
really high energy and so then we fire
our deorbit motors inflate our new
material system this is now called gen 2
and we're going to come in with five
times the heat rate and 50 times the
heat load that we did in our previous
test testing our new material systems if
these proved out then we're talking
about 60 to 80 watts per centimeter
squared is what we're what we think this
material system can do now that starts
to become applicable to the human class
missions and that's what we're working
for here the one thing this test doesn't
get us is the scale right so we're
flying a 3.7 meter diameter
and that that you know that because that
would be effective for the msl class
missions but for human class missions
they're gonna need to be 18 to 23 meters
in diameter but we will have proven out
the load capability as well as the heat
rate capability for this system so I
also mentioned supersonic
retropropulsion it's being one of the
key technologies so in this case we're
coming in at supersonic speeds and we
need to continue slowing down and so
we're gonna fire rockets into that flow
and continue slowing slowing down the
vehicle now we're partnering with SpaceX
on this and so we have some describe
data minute we have a computational
fluid dynamics to understand how these
these Jets are going to interact with
this oncoming flow we've done Windtunnel
tests and now we're partnering with
SpaceX who is one to use supersonic
retropropulsion to return its first
stage of its rocket as part of their
business plan and so we've partnered
with them to get the data from those
tests and we actually have at this point
and so we're able to where we're
starting to use that data understand
what the real next steps should be for
for developing this technology is one of
the keys is the the particular
configuration is very important for
supersonic retropropulsion to understand
how how you're gonna fire these Jets to
keep your vehicle stable and to slow it
down but again this is something that is
being demonstrated with SpaceX and the
NASA will move it forward on how we need
to develop that for human class missions
at Mars sir
so I'm going to try to repeat make sure
I understand so you're wondering within
the launch fairing of our rocket if we
can't stack a greater number of smaller
loads within that but using the smaller
smaller diameters okay so the what we've
done is studies based on you know look
at the different sizes of vehicles that
that we need and doing multiple launches
or multiple vehicles looked at in space
assembly of of different vehicle systems
and the trades always come back that we
it's more advantageous to be able to
have that larger diameter Aero shell
right so that's why the high head in
this case the hypersonic inflatable
decelerator gives us so much of an
advantage and did I answer your question
oh so okay so it's a reliability yes
your reliability issue so yeah that's
what the the systems are being designed
to be highly reliable but then I think
what you might be getting at is like
with the Viking missions we sent two
Landers even with the Mars exploration
Rovers we sent two of those and really
in case one failed you know we had
another one that was that was there and
ready and so I can't say for certain
that we'll do that with the the human
missions but we're gonna make sure with
the human missions we make sure the
systems are reliable most of the
landings are without humans they're
going to be pre positioning resources
and getting things and everything is
there and turned on and ready before
those humans ever leave Earth and so if
there is a failure then we wouldn't be
something humans we'd be sending another
mission to pre position yes
so the question is for the inflatable
heat shield structures what type of gas
do we use to inflate so in the tests
that we've done to date we've done
nitrogen it's in there and now we're for
this last test I mentioned Thor we're
actually going to use freon because
we're limited in our in our sinner body
and freon is going to be a denser give
us more performance out of our inflation
system so we're going to use the freon
gas there it's that is correct it's it's
but it's a pretty it's a relatively
small amount and we're using it
exo-atmospheric Lee but we do but we do
it is it is what's inflating the
structure and it will come back in yeah
yes
yes exactly and I'm gonna get to that in
about a slide or two I think exactly so
yeah so the question was that we or the
statement was that we need to take extra
payload to Mars to be able to get them
back home and that that's absolutely
correct the last thing I want to mention
on the EDL technology challenges is that
being able to precisely land we
mentioned that but also being able to
avoid hazards that we may not have
mapped or didn't know about as it's
landing so the first part is precision
landing and that has to do with knowing
very accurately where you are and the
vehicle being able to know where it is
on a map and accurately navigate to a
point and so our current yeah this is
just representative our current
knowledge of where we are so that's our
error ellipse but if we like a certain
technology like what's called terrain
relative navigation so a map in the
vehicle actually knows the area very
well and it's taking pictures of the
surface and can find itself on that map
and redirect itself to an accurate point
you then get this tiny little circle of
knowledge error of your location so
that's a potential way of getting our
landings more accurate we also have
hazard avoidance so this is using
special sensors such as wide arse and
other other instruments and cameras
during the descent to understand hey
there may be hazards right where I'm
trying to land and having the ability to
divert to a safe site but still within
the requirements of your mission so now
we get to your question about what do we
need to take along right so if we're
looking at the 40 metric tonne missions
this would be two Landers going there
for 40 metric tonne mission to Mars and
so the first Lander has the very first
thing is the Mars ascent vehicle so this
is how the astronauts would get back off
of Mars also has the multi-mission
surface exploration vehicle it has a
fission surface power unit has to go
fetch Rovers it has a drill and then an
ISR your Institute resource utilization
so a unit that can actually process the
atmosphere and/or the ice and water at
Mars into useable elements for the
mission and then of course there would
be a science instrument package as well
and the second Lander bringing the
astronauts would also bring the
inflatable habitat as well as the second
surface fission power unit and the
second Mars surface exploration unit so
figuring out how to package that and put
that all together right and get it to
Mars and so here's the current concept
or a current concept how we would
package that into a lander and on the
bottom and the base of this Landers you
would have packed away the inflatable
aeroshell that we talked about right and
so the current studies are looking at 40
metric ton missions as well as 70 I mean
27 metric ton missions and 18 metric ton
missions and that gets to the trades for
how many launches you'd want to make if
you could do it with smaller launch
vehicles and a but a larger number of
launches is that better or what so those
are the trades that are going on now yes
well so it would but it's it's not
immediate right and we would be storing
the water inside of container so it
wouldn't sublimate from there but if we
just brought liquid water to the surface
yeah exactly right all right so so this
light includes the high ed system and
then if we're looking at what an entry
at Mars might look like with the human
class system we have the inflatable
aeroshell with our Lander system being
protected inside of that and this this
inflatable aeroshell would be 18 to 23
metres across so what much wider than
the barn here so it's a very large air
shell so point is you've seen what we're
doing the exploration and so you've
heard about SLS and we're working with
our commercial partners to have access
to the ISS as well as to low-earth orbit
and creating that supply line whereas
the SLS that NASA is going to
concentrate on is about getting beyond
Earth orbits or beyond the earth gravity
well and we're developing that from our
initial 70 metric ton capability to the
130 metric ton capability that will
carry the spacecraft the crew the cargo
of equipment to deep space destinations
such as Mars and really this is going to
be the platform to continue you know
America's tradition of human spaceflight
now my mind I believe that we humans can
and will you know get to the surface of
Mars and in fact remember the picture I
showed you in the beginning I showed
what Mars looks like from Earth here's
what earth looks like from Mars taken by
one of the Rovers that tiny little speck
right there I blew it up for you all
right so you're here so that is
everything everybody that we know every
road every building every city on that
tiny little speck it just it for me it
really puts things into perspective and
so you know these these are some of the
challenges that that we're working on
today and trying to get humans to the
surface of Mars and I like to think
about what's going to be real tomorrow
and so I have a quick little video for
you
be happy to take any questions you might
have
yeah good
so the question has to do with on Mars
or the moon because it's like Mars yes
so the question has to do with how long
astronauts can stay on the surface of
Mars versus being able to send robots
that can stay there longer so actually
with the the architectures for human
exploration of Mars they can stay there
for quite a long time and in the initial
missions range we're looking at short
duration first if to show that we can
get to the surface and get back off
successfully but with the Institute
resource utilization they can actually
potentially stay there quite long as
long as we resupply them with a couple
main things but they'll be able to
produce their own oxygen and serve other
the key things that they would need so
we could have long-term stays on Mars
right most likely but yeah that we're
actually trading those things right now
we actually don't know exactly what how
and when we're going to put humans on
Mars and how long we'll have them stay
and part of it does have to do with the
orbital mechanics right so where and
Mars are in relation to each other if we
put them on the surface and then what it
takes to get them back to earth so
essentially when we when we go there and
we're gonna stay more than just a few
days they're gonna be there for almost
two years they can be there for two
years yeah well it won't be that we
don't do that the first try will
actually do it most likely pretty
quickly bring them back the first time
yeah one second oh there yeah
so the question is is whether we
actually need lift with the inflatable
heat shields for control so it's this is
one of the ways that were that we are
looking at controlling it so we we do
one lift in some form we can generate it
different ways but we do want lift so
that we can guide these vehicle systems
to get them to more accurate landing
locations that's the main reason so we
get a lift vector that we can control
sure so the question is if Langley is
the lead Center for EDL and what is our
part in it right I get that right ok so
there are really four NASA centers that
work an entry descent and landing and
that's Langley and JPL and Ames Research
Center and the Johnson Space Flight
Center now we all have different parts
Langley would I would think it's easy to
say we lead the technology development
of it so these these new technologies
and developing how we are going to put
people in the surface of Mars I think
Langley is significantly involved in all
the activities that are going on with
new ETL technologies now there are some
like the deployable the mechanically
deployable air shell that's being led at
Ames but we're supporting them and
helping them with that and so it really
is it's a team effort around the agency
so the question was costs for making
this this dream a reality and actually I
cannot answer that for for the entire
human mission right and so we're looking
at you know just the technology
demonstrations and being able to get
there and then we're working with the
architecture folks which you saw I think
the very first week here about the
evolvable mars campaign and how it
leverages activities from across the
agency and so I don't know Steve D do
you have a better answer for that for
what what it'll cost so yeah we've
looked at that a lot and just so you
know I think today NASA gets about 17 to
18 billion dollars a year and the human
exploration part of that is eight with
the eight we do International Space
Station all the work on the station and
we're developing the rocket and Orion as
well as doing some technology work and
of course you know we work for the
president at NASA the president says
we're getting enough however depending
on when you want to get humans to Mars I
think it's safe to say that we we may
need to spend more at maybe we're
getting about 75 cents on the dollar we
need so we need we need a marginal
increase if we want to actually meet
that schedule goal of getting there in
the 30s yeah
so there's certainly or certainly
thought given to it so we yeah we have
been littering the surface of Mars since
the 70s right
but each vehicle system that we sin
there goes through these planetary
protection and we make sure that we are
not sending you know bugs from earth and
germs from Earth and things like that
but yes the the some of the vehicle
system parts and pieces and the systems
that are no longer functional are just
sitting there on the surface of Mars now
usable well in the sense maybe some
maybe some future human mission
absolutely could use some of the
material but that's not in our plans at
this point we would we wouldn't count on
that so the question is are the people
who are gonna walk on the surface of
Mars alive today so we can get people to
Mars by the end of the 2030s right but
given the way government works and how
it's most likely gonna be the 2040s so
yes I would say they are yes
so yeah that's one of the technology
areas that's being worked on different
types of Lacombe you know propulsion to
get us to Mars faster and that you I
don't know if they'll talk about that
next week but that's with radiation
protection and the exposure during that
cruise stage one of the ways we can
mitigate that is actually getting to
Mars faster not taking the the six to
eight months to get there and so there's
there's direct propulsive there's some
technology called VASIMR drive and some
other things like this that could
potentially decrease that time to Mars
and that's really a key potentially key
for the humans it's not so much of an
issue for the pre positioning of the
cargo missions and things like that so
we can use more efficient and slower
methods like solar electric propulsion
that would allow us to get there over a
longer period of time but we can also
use that to slow ourselves down as much
as we can getting close to Mars and
therefore the landing systems could be
more capable when we get there yes
absolutely it is yeah so so is the
rotational direction of Mars factor
factored into the landing so yes well
you can't go either way so retrograde or
pro-grade but there we go we go with the
rotation normal yes
right sorry yeah okay so the question is
exactly so the question is why aren't we
using laser communication instead of
just radio communication to get
information back from Mars from our
vehicles to up to now yeah we have been
using the radio communication we
actually have experiments that are
planned to go to Mars to do laser comm
main thing is though to use it during
entry descent and landing we have this
variable atmosphere to deal with and so
if it's real dusty and issues like that
we don't know that we'd be able to get a
good laser signal and in those critical
times right so we still want to have
strong radio signal to a satellite that
could then relay it through a laser
comment so that's why we're looking at
laser comm in our orbital assets and
another benefit of the laser
communication is it can send a lot more
information I mean right now we have a
few assets there that communicate
through radios and there think of them
as pipes relatively narrow pipes that
we're sending data through and there's
this big backlog of data and images
waiting to go through these pipes
whereas if we get laser communication
working we'll be able to get a lot more
data back if the question was about the
radio blackout or whether it was about
the time delay if it's about the time
delay though the laser and the radio
wave travel at the same speed so there's
still even with laser communication 14
minutes right it still could still be
the same time - exactly thank you all
very much
for the last lecture on the radiation
protection problem
you
