Getting Ready for Mars in 110 Degree Heat

prakish
by Ravi Prakash

Who ever thought that being in the desert in the middle of summer would be so much fun?!

I’m working on a mission called the Mars Science Laboratory, the next rover that NASA is going to send to Mars. Its mission is to help us find out whether or not Mars might have offered a favorable environment for life at one point in time (read more about the mission).

I’m part of the group designing the mission’s entry, descent, and landing phase, also known as the “7 minutes of terror.” This is a really exciting part of the mission because we’re trying to slow the spacecraft down from over 12,500 mph (about 5 times as fast as a speeding bullet) to a screeching halt in about 7 minutes! To do this, so many things have to go right in such a small amount of time. Once the spacecraft enters the Martian atmosphere, and because it’s going so fast, the spacecraft gets hotter than the surface of the sun. Then we deploy a parachute supersonically (faster than the speed of sound), fire retro-rockets at a very precise altitude, and gently lower the rover to the surface of Mars on a bridle (see the animation here). No one ever said rocket science was easy!

parachute
Artist concept of Mars Science Lab’s parachute descending to Martian surface.

Since so many things need to happen perfectly, we test things here on Earth before we launch the spacecraft to Mars. One of my responsibilities includes field testing the radar, which will tell the spacecraft how far off the ground it is and how fast it is going during its descent. If the radar doesn’t work properly, the spacecraft could fire its rockets at the wrong time and crash on the surface of Mars. That would be a very, very bad day.

tower
For the test, the radar was suspended between two towers.

To make sure the radar will work on Mars, a group of us went out to the desert two weeks ago to test it out. The weeks leading up to the test were pretty frantic, with numerous hurdles along the way as we were trying to get the system working in the lab. After we got it working, we took it out to the desert where we attached our radar to a cable, which was attached to a pulley, and all of this in turn was suspended between two towers about 400 feet tall. The other end of the cable was attached to a truck. When the truck drove forward, the radar was lowered at about the speed that it will be descending on Mars just prior to landing.

The testing was so successful that we finished a day early, and were able to leave the really hot desert. We ended up with great data that will help us improve our radar so that it will work flawlessly on Mars. The success of this test made the hard work and desert heat all worth it. But when it was all said and done, we were all pretty glad to go back home, rest and then come back to work to start the cycle over for our next two sets of radar tests–on a helicopter and an F-18 jet!

    13 Responses to “Getting Ready for Mars in 110 Degree Heat”

  1. André Brito Says:
    September 9th, 2008 at 2:35 am

    Hello,
    thanks for the interesting post!

    I also have one question. What’s the difference between MSL and the MERs launches that allows for such huge improvement in the payload mass? Is it just the launcher?

    Thanks,
    André

    Prakash says:

    Great question, André! As you alluded to, launch vehicles come in a variety of sizes.
    Generally speaking, the larger the launch vehicle, the greater the cost, so we try to use
    the smallest reliable launch vehicle that can take our spacecraft to its destination.
    The Mars Exploration Rovers, or MER, launched on a Delta II rocket, but Mars Science
    Laboratory, or MSL, is way too big for the Delta II (in terms of both weight and size).
    The Atlas V 541 rocket met our weight, size, and reliability requirements, so we chose to
    launch Mars Science Lab on it.

    An interesting side note is that the payload mass and size affect our landing system too.
    Mars Science Lab is too heavy and big to use the airbag landing system that the Mars
    Exploration Rovers did, which is why we’re using the innovative sky crane method that you
    can see in the animation.

  2. Viet Nguyen Says:
    September 9th, 2008 at 7:12 pm

    I believe the limitation on the spacecraft system mass was mostly dictated by how to land such a large mass and not how to launch it. That’s why the MSL and MER EDL sequences are so different. An airbag landing such as MER’s is not practical for a rover the size of MSL so the unique MSL landing sequence had to be developed. The neat thing is that if it works it’ll prove out the technology to send even larger things to Mars.

  3. David Says:
    September 20th, 2008 at 8:55 pm

    “we’re trying to slow the spacecraft down from over 25,000 mph…” Did you mean 25,000 kph? Phoenix entered at around 13,000 mph according to what I’ve read.

    Prakash says:

    Oops!! I goofed that one, David! We are actually entering Mars at around 12,500 mph, slightly slower than Phoenix’s entry velocity of about 12,750 mph. Thanks for catching that mistake! (And we fixed it on my original post.)

  4. Derek Says:
    September 22nd, 2008 at 7:02 pm

    “Since so many things need to happen perfectly…”

    With this design, they better go perfectly. The public is spending probably two billion dollars on this. To see it go splat in the Martian sands won’t make anyone happy. I have great enthusiasm for the rover, but the landing system I am not quite so sure about.

    We’ve seen the Genesis spacecraft plunge into the Earth because of a backwards-installed accelerometer and the Mars Climate Orbiter enter too deeply into the Martian atmosphere because someone didn’t convert their units. Humans are fallible creatures and we should always try to “KISS” (keep it simple stupid) whenever we can. This whole skycrane concept is awesome on paper, but when you are putting two billion dollars behind this untried concept I’m surprised–but happy–the thing even received funding.

    Of course, on Space.com, I’ve been a huge proponent of the whole design. The entire mission concept allows us to visit places we would never even though about with the MER designs. And while I don’t like playing devil’s advocate on an issue I am so excited and gung-ho for, I do believe I can understand how some take the preceding point of view. I have confidence in your ability, but if the American public sees yet another expensive flagship mission crash because someone thought a “skycrane” sounded cool, it will spell disaster for NASA. In such hard economic times and harsh political climes, NASA will be forced to put its programs under the chopping block. Hopefully we can get rid of the space shuttle sooner rather than later because the money it will free up will allow us to move forward. Let’s just hope some people don’t consider exploration of a lifeless planet to be a fruitless one and cut back on the Mars program, too.

    Prakash says:

    You are right that keeping designs simple is essential in making a mission successful. Because Mars Science Laboratory is so much larger than anything we’ve sent to Mars, none of our previous landing designs would work, so we had to be innovative. While innovation can have high risk, it can also have high rewards. Without innovative ideas, we would never have landed a man on the Moon or even gone to space in the first place. The moment we are afraid to try to put innovative ideas into practice is the moment our society ceases to progress.

    While the Sky Crane landing system sounds and looks cool, it was chosen because it is a very elegant design. One of the benefits it has over previous landing systems is that we’re not bouncing around on the Martian surface, so we don’t have to protect the rover from hard impacts. Also, once we touch down on the surface, we don’t have to worry about retracting airbags or egress from the landing petals, so we are pretty much ready to start driving. The list of advantages goes on and on…

    An interesting side note is that many people thought an airbag landing system was a crazy idea, but that landing system ended up working great for the Mars Pathfinder and Mars Exploration Rover missions!

  5. Derek Says:
    September 23rd, 2008 at 8:28 pm

    Thanks for the reply. SKIP DOWN TO NEAR THE BOTTOM FOR MY QUESTION if you don’t wish to read all of this: Again these are pretty much things I’ve already thought about and talked about to others. As I mentioned before, I’ve been a staunch supporter of the MSL design (there are many space buffs who aren’t surprisingly). Some have said that for the two billion or so we spent on MSL we could have sent two or three MER designs to explore other places on Mars and thus give us a broader understanding of Mars. I have said that the powerful instrumentation suite allows us to do much more and gain a deeper, if not broader, understanding of Mars. I say let the orbiters take care of the broader exploration and the landers/rovers take care of the deeper understanding.

    People have said that we should use the tried and true MER design, but of course people may say that about other designs before it. Let’s use the tried and true Sojourner/Pathfinder design and retrieve almost no new science. We sorta made a happy medium on this because the landing system was virtually the same except that there was no room for “a mothership” like Pathfinder. It was just the petals pretty much. The Viking used rocket thrusters and so did Phoenix. MSL is obviously much bigger and rocket thrusters would require a massive amount of fuel and make the design wholly infeasible. So yes, I completely understand the concept of the skycrane and hey I support it, but there has been many comments in the community I am a part of about people wanting NASA to essentially send one or two of these rovers every two or four years and make IT the standard platform instead of possibly making MSL the standard platform.

    I explained that doing this of course would mean that these MER-based rovers would be able to only explore equatorial regions and probably not during any major dust storms. Solar power is very inadequate. Then of course then others say let’s retrofit some future MER rovers with RTGs and have them go to non-equatorial regions. I then explain that the MER landing system is very inaccurate compared to MSL’s which prevents us from accessing some landing sites that require higher accuracies during landing, lest it crash on top of plains littered with large boulders or into cliffs, etc. Some people say that there are still several relatively low-risk targets on Mars and that sending multiple craft like we did back in 2003 would help cut back on the risk because if one MSL fails it is a 100% failure but if one MER-based rover fails it might only be a 50% failure if the other succeeds.

    I laid out this comparison:
    MER uses solar panels; limited power, cannot operate long at night, sensitive to atmospheric opacity and thus dust, can only explore equatorial regions.
    MSL uses RTGs; more power, can operate 24.5 hours a sol if they wanted, dust storms don’t really matter, can explore virtually all places on Mars (polar regions only if retrofitted with more heating elements and thus at a cost of instrumentation).
    MERs solar panels means instruments can’t be near as powerful as MSL’s due to limited amounts of power available
    MSLs platform in general allows for a wider variety of instruments and the mechanically capability of transporting them and at a faster pace than MER
    MERs landing mechanism is inaccurate and thus you want to be much more conservative with landing site consideration than MSLs landing mechanism

    >>> So the essential question is, how do YOU substantiate sending MSL at a cost of two billion dollars rather than sending three or even four MERs at the same cost?

    Most likely I will agree with your sentiments, but there are those out there who don’t. If you’d like to read up at all on one of the discussions, there was an article on Space.com about observations from MRO on clay deposits. The article is entitled “Clays Shed Light on History of Mars Water and Possibly Life.” The comments, along with mine (marsbound2024 is my username) stretch across five webpages.

    PS: I am guessing that Eberswalde Crater has been getting the biggest amount of attention followed by Holden Crater fan with the third workshop?

    Prakash says:

    Wow Derek, you’ve done your research! It’s a very fair question to ask why we’re sending one Mars Science Lab as opposed to multiple Mars Exploration Rovers, especially considering the success of those rovers. It ends up being all about the science…

    Science is the primary reason we explore space. However, the bigger the spacecraft, the bigger the launch vehicle, and thus a greater cost. So we have to make a very educated decision about what science instruments we send in order to maximize the science return for the cost of the mission. The science instruments for the Mars Exploration Rovers weighed only 5 kilograms. Each Mars rover, at 173 kilograms, was the lightest rover we could design that could achieve the mission of surviving 3 months while carrying those instruments to various places on Mars. Keep in mind that we have to design the rover to be redundant to countless faults that could occur since we can’t fix a broken piece of the rover from Earth.

    Based on the science findings of the Mars rovers (as well as our Mars orbiters), the instrument suite required to do the next level of science ends up being much more massive than the 5 kilograms the Mars rovers had. In fact, the science payload on Mars Science Lab is more than 80 kilograms! That’s almost half the mass of the Mars Exploration Rovers, and a LOT more science can be done! One might now wonder how Mars Science Lab is only 5 times as massive as the Mars rovers but is carrying 16 times the science payload!

    So to answer your question, the science return of Mars Science Lab should prove to be greater than the Mars rovers because this future rover is able to carry more sophisticated science instruments. If you were to compare the cost of the two missions with respect to the science payload, you could argue that Mars Science Lab gives the public a better science return per dollar because we cost about 4 Mars rovers but have 16 times the science payload!

  6. ed Says:
    September 26th, 2008 at 3:36 am

    when the rocket to mars will be lounched? i wonder when first human will arrive on mars and is it posibble to live there :)

    Prakash says:

    Currently the Mars Science Lab is scheduled to launch sometime in the Fall of 2009. Since this is coming up very soon, we’re in the process of putting the spacecraft together right now! While this mission will not carry any humans, it can be considered a precursor mission that helps us learn more about Mars before we do send humans.

    As far as sending humans to Mars, there are several challenges. One example on the engineering side is the landing system. Sending people to Mars also requires sending over habitats, supplies, and a rocket to send them back to Earth. Landing these things would require a novel landing method that would allow us to repeatedly land something 10-20 times bigger than the Mars Science Lab, and land it in a very precise location. Right now, if we point to a place on Mars, we have the ability to land our spacecraft within 12.5 kilometers of that point. For landing humans and their supplies, we would need to be able to land within a few meters of that target point so that the people, habitats, and supplies are all together!

    On the physiological side, the astronauts would need to be able to survive space radiation during their transit to Mars as well as the harsh climate once they got to Mars. This is an extremely short list of the many challenges that NASA is facing to send humans to Mars. I don’t believe there is a concrete date set for sending humans to Mars, but it is still a long time away considering all the challenges that need to be addressed. This is something that people in school right now could look forward to working on when they graduate!

  7. Derek Says:
    September 30th, 2008 at 3:28 pm

    Michael Griffin, NASA’s current Administrator, has hopes of putting a man on Mars by 2037. The Mars Science Laboratory should hopefully be launched around the fall of next year. No, it is not possible to live on Mars in its current state because it has almost no oxygen, extremely little atmospheric pressure, high radiation, pretty much no water in most places, and extremely cold temperatures for the most part. Now if we built our own pressurized habitats then yes.

  8. Bucher Says:
    February 24th, 2010 at 12:32 am

    That was a good reading and informative. You obviously know your stuff!

  9. Iniquez Says:
    April 5th, 2010 at 9:30 am

    Its not my habit to comment on blogs, but I find this one pretty inshgtful and entertaining to read. Thanks. :)

    Free Energy Resources

  10. Cucchiara Says:
    April 19th, 2010 at 6:08 pm

    cool picsxx

  11. Ankush Gupta Says:
    April 29th, 2010 at 12:20 am

    Hi Prakash,

    I read your paper “Mars Science Laboratory Entry, Descent, and Landing System Overview”. My question is how the PDV will make sure that rover does not land on an unstable terrain (lets say a very big and steep rock). Will it apply some intelligent algorithm to make sure that?

    Thanks

    JPL Media Relations responds:

    The candidate landing areas are selected after careful assessment that they have little slope and few large rocks. The descent system cannot steer the spacecraft away from individual hazards. It is designed to keep the spacecraft within the target area about 20 km long. This means that a much smaller area needs to be certified acceptable in terms of rocks and slope, compared with the earlier descent system used by the Mars Exploration Rovers, which had target ellipses more than three times that length.

  12. Schoene Says:
    May 4th, 2010 at 12:54 pm

    Fantastic post, can I link to this from my blog?

    thanks…

  13. Les Burks Says:
    May 25th, 2011 at 9:14 pm

    I have just been watching a programme on solar eclipses and the effects of the solar wind and it occured to me that no one has ever mentioned solar winds of stars other than sol.

    Is it possible to detect the solar winds of distant stars. If so can this data be used to scan the EM spectrum of these solar winds.

    If this were possible, surely we would be able to detect deflections in these solar winds created by the gravity well and magnetic fields of nearby planets.

    Your comments would be appreciated,

    Many Thanks,

    Les Burks, Retired Telecomms/Electronics Engineer.

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