Slashdot Mirror
Mars Rovers Update
BoldAC writes "CNN is reporting that engineers will upload a software hack to decrease the recent power drain plaguing the rover Opportunity. The hack works by reducing the power supply to a poorly functioning switch." p3tersen writes "Opportunity has photographed a blue martian sunset (it's blue because of the optical scattering properties of dust in the martian atmosphere). In other news, the rovers are beginning to experience power supply problems due to the accumulation of dust on their solar panels."
Every easy solution has a problem. The problem with this one is that the Mars rovers don't have any arms to rip the layers off.
The dust problem is just indicitave of how difficult it is to plan such a complex mission like going to Mars. Until we do this a few more times and figure out a few more things, a manned mission will have to wait.
I wasn't referring to the articles referenced in the story. I was referring to the Slashdot story itself:
"CNN is reporting that engineers will upload a software hack to decrease the recent power drain plaguing the rover Opportunity. The hack works by reducing the power supply to a poorly functioning switch." p3tersen writes "Opportunity has photographed a blue martian sunset (it's blue because of the optical scattering properties of dust in the martian atmosphere). In other news, the rovers are beginning to experience power supply problems due to the accumulation of dust on their solar panels."
Dan East
Better known as 318230.
How is the motor supposed to pull the correct wire (you wouldn't use thread)? Ten different motors?
What do you do with the tear-off once you pull it? Leave it clumped at the bottom or just have hang around trailing behind the rover or right on top of the panels? Cut the wire you say? Kind of difficult to do that if you rolled the wire up on a spool with a motor. Going to need ten pyros for that.
Don't forget that you have to pack all of this onto the rover and fold up the panels. Better hope your wires don't tangle up and prevent the panels from unfolding.
All of this stuff takes up weight and adds complexity. Do you really want to do all of that?
1. It's going to weight more.
2. It's another potential failure.
3. IF it fails, it can cause other things to fail (say, for example, a switch sticks ON and it drains the battery)
Not installing a wiper or other device to clear the solar panel wasn't an oversight. They made a (probably) well-informed decision not to install such a device. I think the progress so far is remarkable and should be commended. Hopefully they've learned a lot and can make improvements for the next mission.
Hindsight is always 20/20...
How does testing the software determine the heater is going to malfunction?
Given CNN's lack of technical depth, for all we know it could be a command to the rover to tell it not to turn on the heater anymore. Either way, they designed the rovers so they can fix them while they're in space, which is pretty good.
Given the limited amount of storage on the rover, it's a higher priority to make sure the upgrade process works, and that it is possible to fix stuff with software, than to make the rover fix stuff automagically.
Need a Catering Connection
A thread attached to a corner of every plastic sheet running diagonally to the opposite corner and an electric motor that activates when the sheet is dirty.
Stack 10 sheets of this and voila, lifetime of the rover multiplied x10.
Conceptually, this is a great idea, except for one problem:
Every layer of $whatever you put on the panels attenuates some of the light striking the panels. The sunlight is also that much dimmer there (at the very least by the inverse square law of distance from the sun, if not also because of atmospheric conditions), so every single watt-hour those things can capture is critical.
Of course, to compensate for the thin film layers, they could have made the solar panels bigger - but that adds launch weight... not to mention the bigger solar panels would make the whole thing more top heavy and likely to tip over due to wind or ground obstructions, meaning you'd want to add size and wheelbase to this thing, meaning you'd need more solar panels... Do we see a vicious circle yet? [grin]
Fire and Meat. Yummy.
I dont buy this for a second. Removal of fine, electro-statically dust, has been practiced on this planet for centuries if not millenia. There are entire industries based on this practice. I am convinced that it was one of those famous NASA managerial pissing contests that ensured no "feasible" or "practical" solution. Read: the companies which proposed the solutions were not part of the "in" crowd.
This makes things sound worse than they actually are. They are not beginning to experience power supply problems -- they are simply getting less power than they were when it first landed, and they are taking some steps to operate more efficiently.
From SpaceFlightNow, in the report for THURSDAY, FEBRUARY 26, 2004 2215 GMT (5:15 p.m. EST):
From the Reuters report:
What the NASA official (Richard Cook) actually said was: "The vehicle is continuing to perform fine but we are starting to modify our daily process to respond to the decreasing power."
Both the dust accumulation and the decrease of sunlight were anticipated. The lifetime (designed to be 90 days) of each Rover is determined when the batteries can no longer be charged enough to survive the cold nights. Spirit is already 54 days into its 90-day "death sentence".
HCG 50a = 2MASX J11170638+5455016
11h17m06.4s +54d55m02s
Why did NASA stray from 'nuclear' batteries, like they've used with the Pioneer, Galileo, Voyager and Cassini missions? Those could power a rover for years.
Most likely because the batteries would out-last the rover itself. It's a complex machine in a hostile environment- something will fairly soon. The solar panels will probably still be operating well after the rovers themselves have failed.
The key difference you're missing is, in your own words, "on this planet". The fact that the rovers are on mars has two important effects. First, the atmospheric composition, weather conditions, and the nature of the martian dust itself render common dust abatement methods here on earth ineffective. The most common, spraying liquid and wiping, is totally out of the question when the temperature is -20 to -80 degrees C. Second, the inaccessability of a rover on mars means that complex mechanical "wiping" solutions are out of the question-- there's no one there to smack the side of the unit when a cam arm gets stuck, or replace a solar panel when a wiper blade gouges it with a sharp pebble.
If you're so sure there's an easy solution, let's hear it. Your bizarre conspiracy theory makes no sense.
If a job's not worth doing, it's not worth doing right.
They're so incredibly smart, in fact, that they don't even need to convert metric measurements to the archaic system they insist on using.
Don't knock US/SAE measurements, there's a good reason they've stayed around.
For scientific analysis, without question, Metric rules.
But when you're actually building and working on things, most of the time a 10% tolerance is good enough. As a result, usually you can stick your thumb across something and say, "Yup, that's an inch - close enough". The base units are more intuitive, although admittedly the interconversion between units is a bitch - but conversions are more common in analysis than construction/maintenance.
My perspective here? Canada went Metric in 1976. I grew up in Metric. I went to school in Metric, fuelled up my cars in Metric, got a set of Metric wrenches when I was a kid, etc. Heck, you wanna know Metric inside and out? Try taking an engineering degree in Canada!
And yet, I know I'm 6'4" tall, 185lbs. I don't know in Metric.
Every time I work on a car, I want to know first, Metric or SAE? (And I don't mean the speedometer, they've all been Metric in Canada since 1976.) Not because I care which wrenches, sockets and feeler gauges I bring, but because I like working on SAE much more.
Why?
I've had more cars with Metric fasteners and specs than I have SAE, and yet, somehow, I can still just put my thumb across a bolt and know, "Hey, that's not 1/2", that's 7/16"!" Why can't I do that with Metric? I sure which I could, especially since I've got more experience with Metric.
Fire and Meat. Yummy.