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Launch Director
& Mars Rover Question And Answer
Presentation
Aren from Vermont
What are the rovers made of?
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Matt
Wallace:
That's a good question Aren. As you can imagine a vehicle
as complex as these Mars Rovers are composed of all sorts
of different materials, but the primary structural material
that you see here in this model for instance is Aluminum
and Carbon composite material. We use Aluminum as kind
of as staple in the aerospace industry because it's light
weight, it's strong, it's easy to get, it's easy to work
with and form into the shapes that you need, and so use
it all over the rover. We use it for these rocker mobility
systems down here as well as the wheels. We use it up
here on the deck. You can see our low-gain antenna, and
on our high-gain antenna a lot of our mechanisms use Aluminum
as well. The other major structural material is Carbon
composite which is a fiberglass-type material. We use
different types. On the rover you can see it on many places.
This mast for instance is a composite as well as the body.
This whole body is a composite material. And the the substrates
for our solar panels are all composite as well. We use
composite material because it is a lot lighter and mass
is very expensive. We pay a lot of money and take a lot
of time trying to reduce the mass on these vehicles and
so composite is a very useful material for us. We have
a couple of other types materials as you can imagine.
We have some exotic materials. Like for example, this
is actually gold on the outside of the body. We have a
silica aerogel which we use for instance in some of our
insulation materials. We have berillium. We have lithium
in our batteries. You could probably find just about every
element you could want to find on the rover. But primarily
from a structural standpoint, it's composite and aluminum.
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Adam from Toledo
If you lose power to the Delta
Rocket, or lose engines in the
middle of flight, is it possible
to recover the rover? (assuming
that the power loss was before
it reached perscribed orbit
and speed)
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Omar
Baez:
And the answer is Adam, basically probably not. If we
lose power to the Delta rocket we usually send what we
call destruct signals to the rocket. And that's to keep
the public from getting hurt. Basically if it's losing
power it might fall over land mass, etc. and we want to
make sure that things of that size, like this rocket are
destructed into pieces that are a little bit smaller and
easier to deal with and less dangerous with all the propellants
on board. So assuming we did destruct there wouldn't be
much left of the rover. And if it did make it into a lower
orbit it probably wouldn't be a wise idea to go recover
it because it does have ordnance devices and the only
thing I know of that I know that can recover something
in a low Earth orbit is probably the Shuttle. We wouldn't
want something with ordnance going in the bay of that.
So the answer is probably not.
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Charu from Nagpur,India
What if the rovers encounter
a martian sand storm on landing?
Will that affect the mission?
Are there any backup precautionary
measures?
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Matt
Wallace:
Another very good question. Sandstorms are not uncommon
on Mars and so that has always been a concern for all
our landed Mars missions. And this particular mission
is not an acception. One of the reasons we worked extremely
hard to prepare these rovers as quickly as we could was
to get them launched in this launch opportunity. And we
only have a limited number of opportunities to launch
to Mars because where Mars is relative to Earth and they
only line up roughly about every two years. If we miss
this opportunity the next opportunity will be a year to
two years later. And the good thing with respect to sand
storms in regards to this launch opportunity is that it
is just beyond the season when we tend to see sandstorms
on Mars in the areas we're going to. So while it's not
impossible that we're going to land in a dust storm, it's
probably somewhat unlikely. If we were to get a dust storm
or a sand storm on Mars, it depends on the severity, the
dust effects what we call the optical opacity which then
effects our ability to get power on our solar panels from
the sun and if a dust storm is not too severe we could
continue on with our mission in a degraded fashion and
do just a little less science, a little less driving and
that sort of thing. If the sandstorm is severe we may
need to go into a hibernate type of mode. And we do have
contingency plans in the event that that needs to be done.
And hibernate, the rover is pretty smart little fellow
and they have the ability to basically go to sleep and
when they go to sleep they use almost no power. It's just
extremely small amounts of power on the order of just
a couple of watts. But it also means that the rover can't
do much. It can't communicate with Earth. It can't do
science and it can't drive so when it goes into hibernate
mode we'll periodically wake it up to talk to it. And
when we believe its acceptible and safe to continue on
with the mission we will then reactivate the daily cycles
and mission scenarios that we had planned originally.
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Peter from Basel Swiss
How fast is the speed to flight
to Mars?
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Omar
Baez:
Well Peter, the speed that we need to get the spacecraft
going at to leave the gravitational well of Earth and
the Moon 23,042 nautical miles an hour. This is also 37,083
kilometers per hour and that is the speed to get us out
of the Earth's gravity well and headed to Mars.
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ROY from TARPON SPRINGS
What is the shelf-life of a
rover on Mars?
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Matt
Wallace:
I like this question. I like the way it was asked. We
don't normally talk in terms of shelf life, but what we
talk about is mission duration and primary mission duration,
but it's essentially the same thing. The question is just
how long can it survive on Mars and our primary mission
is designed to keep us there for 90 Martian days. And
a Martian day is roughly equivalent to an Earth day and
so we are talking about on the order of about three months.
Once we go beyond that we start moving away from the high
summer time and it starts to get colder. We start to get
less sunlight and we start to get somewhat power limited.
And if we make it to 90 days we certainly could go beyond
that. The primary mission is designed for three months
for each rover.
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Michael from Australia
What do you enjoy most about your job?
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Omar
Baez:
Well it's the fame and the fortune. Well not really. There's
no fame in it and there's hardly any fortune in it, but
I tell you the two things I really enjoy in my job as
launch director and launch manager of this mission is
the honor of being a spokesman for a team of so many brilliant,
hard-working people and being their voice in the readiness
to go launch this thing. That's probably the number one
thing that I enjoy the most. The other thing that I enjoy
is the adrenaline rush that you get when you're working
problems late into the count and you resolve that and
all the sudden you're in a very quiet moment of solitude
and you look over to the spacecraft manager and you're
about to put up a mission that he worked on this mission
for probably the last two to three years and some missions
folks have worked their whole career and so it's quite
sobering to see.
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raymond from perthamboy
How will the samples get back
to earth?
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Matt
Wallace:
That's a good question. We get asked that question a lot.
And the answer is that the samples will not come back
to Earth physically. This particular mission is not designed
to bring rocks or soil or anything back from Mars. That's
a fairly difficult endeavor and the down the road NASA
will develop the technology and the capability to do that.
We're in the process of working that issue right now.
As you can imagine, it's hard enough launching a rocket
here on Earth. Trying to launch one off of Mars and get
it back to Earth without anybody else there would be pretty
difficult. Although some day we hope to be doing that
that's not what this mission is designed to do. On the
other hand what this mission is designed to do it to bring
back an awful lot of information on the material on Mars.
And so the way we do that is we have various science instruments
and we get various science instruments on Mars. It's called
"in situ" or "in the situation," if
you will, science, and so we collect the material. We
save it on board in the memories of the spacecraft and
rover and we transmit it back to Earth so that the scientists
and engineers can look at it here. But this particular
mission will not bring any samples back.
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Lance from Austin, TX
Will cameras be mounted on either
of the the rockets?
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Omar
Baez:
Lance, we'll have cameras on both missions. MER-A will
have one aft-facing camera, that’s facing the ground
as we're lifting off on the first stage of the rocket.
MER-B will have an aft and a forward facing camera on
the second stage so you'll actually be able to see the
lift off and you'll be able to see the spin-up of the
MER-B rover as we separate and push it into its third
stage flight.
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Steve from Indialantic
How do you prevent sending Earth-based microbes via the
Rover?
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Matt
Wallace:
That's a good question. This mission was designed to go
to Mars and to look for whether or not Mars ever was conducive
to the formation of life, to look for evidence of water,
and those sorts of things. And so it's very important
that if we're going to look for aspects of life, to not
bring life with us. We don't want to contaminate our own
science lab, if you will, and so we go to quite extraordinary
efforts to make sure that doesn't happen. There are a
number of things we do. First of all, when the hardware
is built before it's delivered for assembly into the spacecraft,
it has to be cleaned, in one form or another, of all microbial
life. And the way we do that is we either clean it with
various cleaning agents, or the second way to do that
is to heat it up over 200 degrees Farenheit for an extended
period of time in a dry environment. And that will also
kill the microbes. Once it gets to a point where it's
going to get assembled into the spacecraft, we have to
do some other things as well to make sure that it doesn't
get recontaminated. We're continuously cleaning the spacecraft.
That's something we do just every single day and every
single operation of every day. And we also spend a lot
of time making sure that our garmenting is appropriate,
and we dress up much like a surgeon would dress up, going
in to perform surgery, we use sterile gloves, we use sterile
overalls and face masks to make sure that we're not breathing
onto the flight hardware, we use booties over our shoes,
and we keep the environment in which we do the assembly
and testing very clean, by constantly filtering in and
blowing clean air through those test areas. And so those
are the ways in which we make sure that we don't take
life with us to Mars.
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Charles from Big Spring,TX
How will you insure that the vehicle will come to a stop
right side up? Does the rover have a base station like
the one Sojourner used? |
Matt
Wallace:
That's a very good question, and the answer is that
when the rover lands on Mars, this rover will be folded
up, the mast will be down, these panels will get folded
up into a tetrahedron, and the whole rover will squat
down, and on to what we call a base petal of the lander.
And the lander has three sides, it looks like a pyramid.
So when it lands, it's cocooned inside these airbags
and the airbags surround this pyramid shaped lander.
When the lander comes to rest and the airbags are retracted,
in the event that the lander is on a side, the motors
that open the petals in the lander are strong enough
that they can drive the lander basically back onto its
base petal. It can drive it open and flop the base petal
down onto the Martian surface so that the rover is basically
right side up. And from there we intend to stay just
like that, so that we don't have to deal with the situation
that Charles has asked about.
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Chelle from Disneyland
When the Delta rockets release
the booster rockets, are first
3 ejected and then the remaining
6 or are they released 3 at
a time?
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Omar
Baez:
Jon, the answer to that is, I've got to take you back
a little bit. The lights - there's nine solid rocket motors
on the Delta II. We light six of them on the ground. As
we're going through the atmosphere, we will expend those
six solid rocket motors. Towards the end of its life,
we'll light the other three, making that total of nine.
One second after those last three are lit, we'll jettison
three of the rockets. One second later, we'll jettison
three more of them. And during this time, we'll be still
flying on three of the air-lit solids for the next 65
seconds after that point and then we'll jettison those.
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Chelle from Disneyland
How far into the mission is the spacecraft's distance
calculated in "nautical miles"? What is the
reason for using the nautical mile?
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Omar
Baez:
That was a good one! I had to go do some research on that
one and I spent some time doing that. The reason we do
it – humans are lazy. And the Earth is composed
mostly of bodies of water. And the way most charts have
been written down, has been a system of Mercator projections,
that means latitude and longitude. And the way that is
broken up is into squares over the Earth, a matrix of
squares. Each one of those points inside of those squares
are divided into hours, degrees, minutes, and seconds.
And one minute in that Mercator projection system is equal
to 60 nautical miles. So the reason we use that is the
charts are available, it's a system that's been used for
many years, all the folks doing navigation over the oceans
have been using it, the aviation industry uses it. And
it was just easier to adopt, and that's why we use it.
But you could really use any other system - you'd just
have to chart things in that other system that you chose.
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callum from dunfermline
How will it get to Mars without burning up in the force
of gases on Mars?
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Matt
Wallace:
Another good one, Callum. As I mentioned before, the
rover is going to be cocooned inside this lander for
landing. And the lander itself is surrounded by what
we call an aeroshell. It's a conical shaped thing, with
a heat shield on the bottom, and it looks an awful lot
like lunar capsules, if you've ever seen those, that
come back through the Earth atmosphere. And we use exactly
the same process as they used on those Apollo missions
when they came back through. The capsule protects us,
it has a heat resistant coating all around it, and it
protects us as we hit that outer atmosphere of Mars.
We're travelling on the order of about 17,000 miles
an hour and when you hit atmosphere at that speed, it
certainly generates an awful lot of heat. The bottom
of the capsule is a heat shield, as I mentioned before.
It's what we call an ablative heat shield. What that
means is that it burns away, it takes the heat away
from the vehicle by burning away. It's made up of a
silicone-impregnated cork material, believe it or not,
and it gets extremely hot, and it burns away, and as
it burns away, it takes the heat off the flight vehicle,
and eventually once we're through the outer atmosphere,
and we've slowed down enough that we can deploy a parachute,
we pop off that heat shield and the lander rappels down
and away from the back shell, and we're pretty much
through the dangerous portions of the entry relative
to the hot gases that Callum's asking about. So, good
question.
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Don from Solvang
What is the reason for two instantaneous launch windows
some 38 minutes and 12 seconds apart on MER-A?
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Omar
Baez:
Good question, and the answer to that is, if we had one
instantaneous window, the chances of missing it would
be great and there's a lot of effort to hit that window,
a lot of work behind it, hours and hours of work to hit
that one second. And a boat straying into the area, or
a glitch in something, could really put a dent in the
whole day and then you'd have to delay another day. So
we chose another window and what you've got to remember
is that when we launch one of these rockets, the goal
is to hit an arbitrary point in space, arbitrary selected
point in space, and what happens is when I hit the first
window which is at 93 degrees, this point is here. If
I miss that, the Earth is turning as the time clicks off.
So I have to shoot another azimuth to hit that same point
in space. So we're very comfortable with launching from
the east coast here at 93 degrees, and the next azimuth
that we'd like from the east coast is 99 degrees. And
they worked out well in the mission design for both of
those reasons. We have a max, also, on the amount of time
in between these two periods, and that's because I can
only keep the liquid oxygen on board the Delta rocket
at a certain quality necessary for flight for about 80
minutes. So I'm limited in how many opportunities I can
have for an escape mission such as MER-A.
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Mario from Gravelbourg
What is the MER's scientific equipment for tests? How
do you control the rover properly considering the time
the controller's signal takes to go and come back?
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Matt
Wallace:
Mario's going to be a journalist, he snuck two questions
in there on us in one shot! I'll answer the second one
first. It takes about nine minutes to send a signal from
Earth to Mars. At the time when we land, there's about
a hundred million miles distance between Earth and Mars.
And it takes somewhere on the order of 9 or 10 minutes.
And that is a challenge. You can't joystick this thing
like you would a radio controlled car. And the way in
which we get around that is we plan - we put a lot of
autonomy on the rover. We give it the capability to do
a lot of things with just a few sets of high level commands.
And so that we only have to command it once, or maybe
twice, a day. So that we don't have to spend a lot of
time communicating with it and it doesn't have to spend
a lot of time communicating with us. And we don't have
to wait every time we send it a command. I mean, if we
had to, say, move forward a little bit, and then wait
nine minutes for that command to get there, and wait another
nine minutes for it to come back, every time we had to
move the rover just a little bit, it would take an awfully
long time and wouldn't be very efficient and we couldn't
do nearly as much science as we need to do. And so we've
given the rover an awful lot of smarts so we can basically
say "we want you to get there," and it will
figure out how to get there. And we can tell it to "go
investigate that rock," and it will figure out the
best way to do that. So we have some very capable software
engineers who have given us the ability to do that and
save a lot of time and do a lot more science. Relative
to the science that we can do, this is a very powerful
little machine, and I'll talk about a couple of them briefly
here. Up on the front - you can't see it on this model,
I don't think - there's an arm tucked up underneath. And
that arm is about the same size my arm, actually. And
it moves in very much the same way. It's got a shoulder
that moves in elevation and azimuth, it's got an elbow,
and it's got essentially a wrist. We call it a turret.
It can move in a couple different directions as well.
So all told, we have five degrees of freedom on the arm.
And at the end of the arm, we have some very powerful
little science tools that have been in development and
design and built for a long time now. And so the objective
is to find an area that we're most interested in, and
then we'll move the arm out, and just to give you one
scenario, we might use the rock abrasion tool, which is
on the end of that arm to abrade away the outside, oxidized
layer of the rock so that we can get down closer to the
core of the rock to find out what it's made of. Now once
we've abraded that away, we rotate the turret and we can
use one of our spectrometers. We have what they call a
Moss-Bauer spectrometer, which is designed to look for
iron minerals, and we have an Alpha Proton X-Ray Spectrometer
which is a bit of a mouthful, but essentially it looks
for various elements in the rock. In addition to that,
we have a microscopic imager. And all these things ar
roughly the size of sample size that we've abraded away
with this rock abrasion tool. Another very powerful piece
of science hardware that we have on board on the top of
this mast, and it's a spectrometer as well, it's an imaging
IR spectrometer. It's called "Mini Thermal Emissions
Spectrometer" and the actual spectrometer is down
inside the body of the rover, under here. And what we
do is we have an optical path, just like a telescope on
a submarine, up to the top of the mast and out this little
hole, and we can look out at the spectral signatures,
the IR spectral signatures, of…, for instance, possibly
that little area that we abraded away, but we can also
look out into the distance to look at various rocks and
soils and formations, and by getting an understanding
of what those spectral signatures are, make good decisions
about what direction we want to go, what things we want
to investigate on Mars. So we've got a lot of science
on board, and we're going to get a lot of good information.
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ARNOLD from LOS ANGELES
Can the two rovers talk to each other and can they help
each other if an emergency comes up... like bad communications
with Earth?
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Matt
Wallace:
Good question. It turns out that the two rovers cannot
talk to one another. They are going to land very far apart
on Mars. And so we don't have a radio system that would
allow them to talk to one another. Instead what we have
are two different radio systems that allow us to talk
either directly to Earth with what we call our X-Band
system, or we can talk to one of the orbiting NASA or
ESA satellites that either are or will be in orbit around
Mars at the time that we land. There are going to be three
of those. Each of those has a UHF receiver and transmitter,
and the rover has one as well. And so that about twice
a day, we have the ability for about five minutes each
during a pass of an orbiter, to communicate with those
orbiters. So while they can't talk to one another, they
have the choice of talking directly back to Earth or to
one of the orbiters.
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Curator:
NASA Official:
Web Development: JBOSC Web Development Team
Last Updated:
July 23, 2003
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