Mars Rovers Return to Exploration

inkslinger77 writes "The two Mars rovers that have been carefully conserving critical power supplies since June, when the summer dust-storm season began on the red planet, are now springing back to work as the storms subside. Typically, the solar panels on each rover produce about 700 watt-hours of electricity per day — enough to light a 100-watt bulb for seven hours, according to NASA. But this year's dust storms reduced that to as little as 128 watt hours per day. When daily power generation is down to less than 400 watt-hours, the rovers suspend their driving on the planet and stop using their robotic arms, cameras and other instruments. But they are back in action now!"

Re:Amazing

[unfunk]

I was almost sure that at least one of them wouldn't survive the storms, but, fortunately, reality proved me wrong. Go NASA!

I actually think it's kinda surreal, the way they just keep going.
If mankind ever makes it to Mars in the flesh, I hope they bring one back and give it a medal or something.
Maybe mount a plaque at the point where it 'died' on Mars as well.

Re:Next?

[paleo2002]

Are you kidding? These rovers are functioning way beyond their mission parameters. They've collected more data than anyone expected. We've gone from "What if there's water on Mars" to "How much water is there on Mars?". The rovers survived a Martian dust storm! Martian dust storms have been known to cover the entire planet.

Let's put it this way. If your car was as well-designed and resilient as these rovers it would run on empty for 100 miles, drive up mountains, and review your tax returns.

Re:Crazy units

[netpixie]

Bzzt!

> 700 joules per second per hour per day

No, 700 joules per second times hours. i.e. energy per time multiplied by time = energy

A watt-hour is a unit of energy just a a joule is, except its a bit clearer how it relates to other quantities.

And calculating average outputs over a time period where the out put fluctuates wildly is a bit silly.

Re:Crazy units

[isomeme]

I initially had the same objection as you, but then I realized that the "watt-hours per day" unit actually makes sense.

The rovers' solar panels only generate power during daylight, and even then the generated power varies continuously as the sun angle changes. So talking about average power production produces a misleading picture of how the power is actually delivered; in many ways, it's more useful to think about some number of watt hours being accumulated per day as a lump sum, with nights separating those lumps.

Furthermore, the generated power goes into batteries, the energy content of which can certainly be expressed in joules. But it's frequently more useful to express battery energy content in watt-hours, because you frequently want to know how long an N-watt drain can be maintained. So expressing the daily energy accumulation in watt-hours delivered to the batteries simplifies follow-on engineering calculations.