LOG ENTRY: SOL 95 (Feb. 11, 2036)
Today was all about repairs!
The Pathfinder mission ended because the Lander had an unknown critical failure. Once they lost contact with the Lander, they had no idea what became of Sojourner. It might be in better shape. Maybe it just needs power. Power it couldn’t get with the solar panels hopelessly caked with dust.
Setting it on my workbench, I pried open a panel to peek inside. The battery was a lithium thionyl chloride non-rechargeable. I figured that out from some subtle clues: the shape of the connection points, the thickness of the insulation, and the fact that it had “LiSOCl NON-RCHRG” written on it.
I cleaned the solar panels thoroughly, then aimed a small, flexible lamp directly at them. The battery’s long dead. But the panels might be ok, and Sojourner can operate directly off them. We’ll see if anything happens.
Then it was time to take a look at Sojourner’s daddy. I suited up and headed out.
On most landers, the weak point is the battery. It’s the most delicate component, and when it dies, there’s no way to recover.
Landers can’t just shut down and wait when they have low batteries. Their electronics won’t work unless they’re at a minimum temperature. So they have heaters to keep the electronics warm. It’s a problem that rarely comes up on Earth, but hey. Mars.
Over time, the solar panels get covered with dust. Then winter brings colder temperatures and less daylight. This all combines into a big “fuck you” from Mars to your lander. Eventually it’s using more power to keep warm than it’s getting from the meager daylight that makes it through the dust.
Once the battery runs down, the electronics get too cold to operate, and the whole system dies. The solar panels will recharge the battery somewhat, but there’s nothing to tell the system to reboot. Anything that could make that decision would be electronics, which would not be working. Eventually, the now unused battery will lose its ability to retain charge.
That’s the usual cause of death. And I sure hope it’s what killed Pathfinder.
I piled some leftover parts of the MDV into a makeshift table and ramp. Then I dragged the Lander up to my new outdoor workbench. Working in an EVA suit is annoying enough. Bending over the whole time would have been torture.
I got my toolkit and started poking around. Opening the outer panel wasn’t too hard and I identified the battery easily enough. JPL labels everything. It’s a 40 Amp-hour Ag-Zr battery with an optimal voltage of 1.5V. Wow. They really made those things run on nothin’ back then.
I detached the battery and headed back inside. I checked it with my electronics kit, and sure enough it’s dead, dead, dead. I could shuffle across a carpet and hold more charge.
So I knew what it needed. 1.5 volts.
Compared to the makeshift crap I’ve been gluing together since Sol 6, this was a breeze. I have voltage controllers in my kit! It only took me 15 minutes to put a controller on a reserve power line, then another hour to go outside and run the line to where the battery used to be.
Then there’s the issue of heat. It’s a good idea to keep electronics above -40C. The temperature today is a brisk -63C.
The battery was big and easy to identify, but I had no clue where the heaters were. Even if I knew, it’d be too risky to hook them directly to power. I could easily fry the whole system.
So instead, I went to good old “Spare Parts” Rover 1, and stole it’s environment heater. I’ve gutted that poor rover so much, it looks like I parked it in a bad part of town.
Bringing the heater to my “workbench,” I hooked it to Hab power. Then I rested it in the Lander where the battery used to be.
Now I wait. And hope.
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