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MER-A Webcast - Launch Director & Mars Rover
 
Question and Answer Board

Aren from Vermont
What are the rovers made of?
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 beryllium. 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.
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 prescribed orbit and speed)
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.
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?
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 exception. 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 acceptable and safe to continue on with the mission we will then reactivate the daily cycles and mission scenarios that we had planned originally.
Peter from Basel, Switzerland
How fast is the speed to fly to Mars?
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 is 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.
Roy from Tarpon Springs
What is the shelf-life of a rover on Mars?
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.
Raymond from Perth Amboy
How will the samples get back to earth?
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.
Lance from Austin, Texas
Will cameras be mounted on either of the the rockets?
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.
Steve from Indialantic
How do you prevent sending Earth-based microbes via the Rover?
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 Fahrenheit 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.
Charles from Big Spring, Texas
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.
Chelle from Disneyland
When the Delta rockets release the booster rockets, are first three ejected and then the remaining six or are they released three at a time?
Omar Baez:
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.
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?
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.
Callum from Dunfermline
How will it get to Mars without burning up in the force of gases on Mars?
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 traveling 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.
Don from Solvang
What is the reason for two instantaneous launch windows some 38 minutes and 12 seconds apart on MER-A?
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.
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?
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 are 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.
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?
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.