These nice pictures are from today’s New York Times, and accompany an article about Curiosity by Kenneth Chang. The captions below are from the article:
The size of a small car, Curiosity is much larger than previous Mars rovers and carries 10 science instruments.
POWER Dust can cover solar panels on Mars, so Curiosity generates its own power. Eleven pounds of plutonium dioxide generates heat, which is converted to electricity and used to recharge two lithium-ion batteries.
VISION Extending 7 feet above the ground, a mast holds Mastcam, a pair of high-definition cameras, and ChemCam, which can measure the composition of rock after shooting it with a laser.
DRIVE Each of the 20-inch aluminum wheels has its own motor.
REACH The rover’s 7-foot arm carries several tools, including a camera, an X-ray spectrometer, and a drill, brush and scoop for collecting samples.
ANALYSIS The rover’s body holds experiments for detecting ground water, measuring naturally occurring radiation and analyzing soil and rock samples delivered by the robotic arm.
And the landing site and path of Curiosity’s planned peregrinations (red line):
This particular image looks just a bit menacing.
and this time, the check box.
Only if you are a chunk of Martian hematite!
how do you convert heat directly to electricity?
http://www.inl.gov/research/mars-science-laboratory/
also, see: http://en.wikipedia.org/wiki/Thermocouple
and
http://en.wikipedia.org/wiki/Thermoelectric_generator
or, more to the point: http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator
thanks.
I use thermocouples all the time to monitor temperatures, but did not know they could be run in reverse.
“Reverse polarity?”
“That is correct, Mister Scott.”
Actually, that is running them in the same direction, from heat to electricity, just with a battery to be charged or powered device to drive instead of a milliammeter calibrated in units of temperture.
But they can be used in reverse, and will generate heat when power is driven through them. If I remember rightly it’s non-Ohmic heat but actually transferred from the inevitable other junction, and if you have a series of thermocouples of alternating polarities, one set will grow hot while the other set grows cold. Isn’t something like that how some small 12v food warmers/chillers for caravans (as we call them, trailers to the US) work?
I think that you’re getting confused with the Peltier effect.
http://en.wikipedia.org/wiki/Peltier_effect#Peltier_effect
Or I’m getting confused ; I thought it only applied to semi-conductors, but apparently not. Oh well, IANAPhysicist.
Same here. Despite my specializing in chemistry, I didn’t know they could be a significant source of electricity. Apparently it will work in these conditions, as there is an extremely cold atmosphere which provides the temperature gradient.
Isn’t it chemistry that obsesses over finegrained reversability?
Many solid state processes works in reverse, as long as they don’t primarily dissipate. In fact, I’m hard put to come up with a counterexample besides friction.
Yup. Having different materials fused together generally suggests microcurrents to this formerly chemically-minded person. And just the computer needs what…. 4 watts? 10 watts?
Before my little reading excursion I didn’t realize such currents were possible from a thermocouple. Apparently the output is proportional to the gradient involved. (So I couldn’t see this working on Venus – or anything working for long, for that matter). I couldn’t see this working well on the moon, either – with no atmosphere to provide cooling. But I could always use enlightening. My physics, chem and thermo is way rusty from underuse, being a social scientist (i.e. bullshit artist).
“with no atmosphere to provide cooling.”
No need for an atmosphere – the elements to be cooled could simply hang out in space and radiate.
I suppose so… as long as they were in the shade. Otherwise, you get radiated on. My limited understanding is that simple radiation into space ain’t all that fast a process compared to how easy it is to have heat conducted/convected off something in contact with something else. Despite the fact that the background radiation temperature averages some 2.7K out there, just hanging out in space isn’t really such a hot way to lose your specific heat. (radiative transfer moves a lot less heat, typically, than conductive transfer).
(how’d that word “specific” get in there?)
dagnabbit.
Not to be redundant, but I hope anyone who is interested in Curiosity looks at this Wind River site (below). The video (fantasy) of the entry is great, and when it finishes, it provides links to JPL videos of Curiosity during its build: the tests and comments by the people who worked on it.
http://www.windriver.com/announces/curiosity/?mkt_tok=3RkMMJWWfF9wsRokuqvBZKXonjHpfsX56u4rW6ag38431UFwdcjKPmjr1YADT8B0dvycMRAVFZl5nRtRFOSHdZZF6A%3D%3D
Eleven pounds of plutonium…
The rover’s body holds experiments for … measuring naturally occurring radiation
Let’s hope they placed that instrument far enough away from the plutonium dioxide power supply.
I’m pretty sure RTG units are well-shielded.
You can read about the design at the first link I provided above. Cool that my girlfriend and I recently toured the “Craters of the Moon” monument in eastern Idaho, passing near some of the laboratories where the power generator was designed and built. I had no idea until I looked them up to answer the question Chas posed above.
The isotope should be Pu-238, which is a benign alpha emitter at low energies. A thin plate stops that:
“Plutonium-238, for example, requires only 2.5 millimetres of lead shielding to protect against unwanted radiation.“
I’m surprised the wheels are aluminum – I sorta supposed they were carbon fiber. Maybe that’s been addressed in a Curiosity Q/A somewhere, but I found this reply to a land-based question, suggesting that within a given hard impact range, carbon fiber will shatter while aluminum will bend. Not sure if that’s it, in case any materials-types have further input.
My google fu says it is because they are integrated shock absorbers:
“Inadvertently adding to the rovers’ panache are the spiral flectures. The futuristic-looking “hubcaps” were chosen over dozens of other flecture and spoke options and are designed to absorb shock and to protect the rest of the vehicle during driving. Next Intent, a company in San Luis Obispo, California that specializes in machining complex shapes, manufactured the wheels. The overall wheel design allowed them to machine each wheel from one piece (or billet) of aluminum. Being able to use just one piece of aluminum minimizes what’s called scar mass, or useless leftover material where parts would join and makes the wheel stronger, Voorhees noted.”
Thx!
Here’s another, also taken with MRO’s HiRez camera:
http://hirise.lpl.arizona.edu/images/2012/details/cut/landing_site_annotated.jpg
I hope at some point, they drive the rover to the sky crane crash site. It looks like the skycrane did a fair amount of damage when it hit.
Does anyone here know how fast Curiosity can travel between sites of interests?
Like the MERs initially, they will use the same hazard preventing software. That will improve, as the MERs did continually.
But IIRC the top speed is not much higher than the MERs, probably to save the engines for the long haul.
How fast could the MERs travel?
I recently read 90 meters per hour.
I’ve seen “4cm/second” … which would be 144m/hour.
Whether that would actually be achieved … the science team have this awkward habit of seeing “interesting stuff” and requesting a detour and a photo opportunity.
Several of the rover drivers have accounts on Twitter and tweet regularly about what they’re up to.
The journey is the reward.
They won’t come close, because the wreck is a torn up driving hazard, with remaining hypergolic self igniting and corrosive fuels to boot.
[Originally they intended to use up the fuel before crashing. I don’t know why, but they changed that.]
There no scale superimposed on the photo to show hw far away the sky crane is from the rover. Anyone know?
I heard this in an interview with one of the engineers… If memory serves it is 900 meters. (or was it 600 meters?)
Seriously cool photos.
Although you may not have seen this one which is apparently being suppressed for reasons of national security – and sanity:
http://p.twimg.com/AznK0ryCIAEkRQN.jpg
All of this space exploration stuff began with Sputnik 1, so it seems only a smidgin off topic to mention this here.
http://www.bbc.co.uk/news/uk-england-19164236
Sir Bernard Lovell was a pioneer of radio astronomy, although the popular press seem to obsess over the fact that his telescope was used to track Sputnik 1. He was one of my country’s great scientists but thanks to all the excitement about people riding bikes in circles, nobody seems to have noticed he’s gone.
Sorry for the derail.
A definite loss.
I wonder if they’re going to try to continue with Sky at Night when Patrick Moore dies. He’s not looking well these last few years.
ACCELERATING EVOLUTION ON MARS
What makes this new Mars exploration so special (for me as a radiation biologist) is the fact, that the rovers energy supply is by about 5 kg of plutonium 235, providing about 120 W electric energy for at least five years. Thats fine, I would say from an engineers point of view, and I would also like to drive my old Benz with this sort of low-emission, low-cost and low-maintenace type of fuel.
But the radiation-biologist in me (and I hope you agree somehow) has to wonder about the long term consequences of 5 kg plutonium, a potent alpha emitter, if it comes to its mutatgenic effects in living organisms. Assuming the plutonium is relased from the mars rover and evenly spread over the hypothetical mars ecosphere, it would cause a tremendous rise of the mutation rate in all cells, whether low prokaryotes or in higher and ulti-cellular creatures like plants or animals or anything else in between. This means the 5 years mission of the man-made Mars rover will not only explore the presence of live on Mars, but if there is any, it will also drive evolution by increasing the number of new mutants. So scientists will not only be the silent observers, but active players of an extra-terrestrial evolution of life.
(read more here http://broken-radius.blogspot.de/2012/08/accelerating-evolution-on-mars.html)