Hindsight

LOG ENTRY: SOL 90

I’m going to sleep for a week when I get back to the HAB.

After all of the effort and days spent traveling, I had successfully acquired the 200-kilogram hunk of metal that could save my life. Having the capability of communicating with NASA would greatly increase my chance of escaping this planet.

For now, however, I find myself preparing for another fantastic journey across the barren Mars terrain in a cramped, rolling tin can.

I decided to do one final check to ensure that Pathfinder was securely fastened to the top of the rover. Then I was ready for the trip back to the HAB, following the breadcrumb path I had left behind. Only I wish it were breadcrumbs, instead of tire marks in the sand, but I’ve been so fortunate lately, why should I be complaining?

Walking around the rover, I determined that everything was in order. That is, until I walked around to the front wheels of the rover. Small tears appearing in the 4 front and mid tires caught my eye.

From training, I knew that JPL deliberately manufactured each tire for the Mars rover with twelve holes to aid in navigation on soft terrain. The holes were actually put in the tire to spell out “J P L” in Morse code, and could be tracked by imaging technology.

Since JPL intentionally put holes in the tire, how could adding a few tears be a big deal?

I inspected the wheels and determined that there was not significant enough damage done to the tires to compromise the driving and navigation of the rover. Shortly after, I was rocketing at a blazing 25 km/hr toward the HAB.

Looking out of the windows of the rover, I began to think about how long it has been since I’ve had any human interaction. One-fourth of a year spent in isolation.

I was jarred out of my wonderment by a sudden jolt.

Putting on my EVA, I crawled out of the rover muttering how fortunate I’ve been lately. Jumping onto the rocky ground, I immediately noticed the problem. The small tear I had just previously disregarded had rapidly expanded.

How could this happen?

I remember learning about the design of the rover. Thin tread reinforced by two rims and a stiffening ring. All of them connected by wheel flexures to withstand the shock of impact from the rover being dropped onto the terrain from a large height. The tread had been put through intense stress, strain, and simulations of Mars terrain to ensure it could endure mission requirements. How could it possibly be tearing this early in use?

Looking at the wheel a second time, I noticed that the damage to the wheel appeared to be more of a puncture than a tear. I walked several hundred meters from the direction I came and noticed the hazardous terrain I had previously ignored. Directly in the traveled path laid several particularly pointed rocks. After a quick inspection, it was clear to see that the patch of rocks was deeply imbedded in the ground and wouldn’t move upon impact.

The best guess I had was that this unusual condition forced a hole in the tire.

I climbed back into the cockpit of the rover, pulling off my EVA and flopping down into the driver’s seat.  I exhaled deeply and ran through my options.

I could continue on my way back to the HAB, visually scanning the land, avoiding all dangerous terrain to avoid further damage. Then I could wait to do repairs in the HAB, where the necessary tools are. Alternatively, I could stay where I was for an extended period of time, repairing the tire. Of course, there’s always waiting until the rover fairies turn the rover into a chariot and fly me back to the HAB…

 

LOG ENTRY: SOL 95

 

My wish has been granted!

Well, not exactly, but I have duct tape, so there’s that. I patched the punctures with quite a bit of duct tape, which appears to be holding up. Granted, I have been overly cautious about what I’ve been driving over, but I digress. The overall navigation of the rover has been unaffected, but there is a cyclically occurring feeling of having a flat tire.

Luckily I’ve just picked up the HAB’s beacon and think I’ll make it there without any other problems!

At least I believed that for a short while.

As great as living in the rover was for three sols in a row, my body demanded stretching space. I stopped the rover and slid back into my EVA. As I emerged from the dark belly of the rover, I scanned the horizon.

To my surprise, I saw nothing but a vast expanse of orange rock.

I decided to take another rock sample, might as well give the ARES 4 crew something to work with when they arrive. Dropping a few rocks into a sample bag, I lifted my head and stared at the rover. I cocked my head from side to side wondering what made the rover look strange.

It suddenly hit me. Just looking at the chassis, it was clear that the front of the rover was leaning downward. There was a structural flaw. The arms and siding of the rover were angled forward. This in combination with the placement of pathfinder on the front of the rover’s hood caused the front and middle wheels to support more than one-sixth of the designed weight. This excessive force applied on several wheels when driving forward caused extra tearing and puncturing, specifically when pressured against the large, embedded rocks.

I had been wrong all along. The source of the tears was causing a monumental problem. Unlike the strategically placed navigational holes, the tears and punctures were a direct result of the additional force exerted on the front four wheels, and would continue to worsen. It would continue to do so until they became structurally flawed, failing to support the rover, ultimately turning the multi-million dollar Mars Rover into a giant hamster ball.

Looking at the leaning cage of death, I realized how lucky I had been that the front wheels hadn’t had total failure stranding me further.

There was no way I could possibly continue pushing onward. Suddenly the fear of being unable to return to the HAB hit me all at once.

My legs collapsed to the ground as I knelt before the unforgiving Mars terrain. I was tired, tired out of pure exhaustion, and tired of fighting the relentless elements. I slammed my forearms on the hard, barren ground. I would not let this be the end of me.

Trying to regain my composure, I attempted to fabricate a plan to get back to the HAB. The solution wouldn’t require a complete fix of the rover, only lasting long enough to make it back in one piece.  My mind was racing, all along having the fear of failure creeping in the back of my mind. Suppressing all doubt in my mind, I began developing a final plan to make it home.

My options were limited, but I began from the basics. Repositioning pathfinder to balance the stress on the wheels, I could continue driving carefully, avoiding all dangerous environmental conditions.

No, that wouldn’t work. The damage done to four of the wheels has greatly exceeded safe conditions and threatens immediate failure. Simply moving Pathfinder would do little in terms of redistributing weight.

I exhausted nearly every option available. Maybe there is a way I could reconstruct parts of the wheel to support more load. In terms of reinforcing the wheel flexures there are plenty of hard materials which could be attached in a manner to enable the front of the rover to support its large load. This solution has promise, but in the event that the makeshift wheel flexures break or snap under compression would cause more damage to the rover.

My mind and body ached and cried for rest. I crawled back into the rover and was shortly fast asleep.

 

LOG ENTRY SOL 98

Well I’ve come up with an idea.

It’s dangerous and potentially stupid, but I can no longer rely on highly mechanical technologies like duct tape and I’m out of options. I’m prepared to drive the rover in reverse, putting more force on the back wheels, which are relatively unscathed in comparison to the front wheels.

The good news is, I ran some numbers, and there shouldn’t be any tipping or slipping causing the vehicle to flip over.

Finalizing my decision, I centered the pathfinder’s weight across the rover, and began the final leg of this journey.

Carefully I turned the rover in a circle, finessing the positioning to ensure going directly in reverse would return me to the HAB. I gingerly tapped the pedal, gripping the gear shifter tight in my hand. Sweat began beading on my forehead as I continued in a linear path.

As I pulled in closer, I noticed the HAB on the horizon. I was close.

The wheel suddenly strained and began to shake. I clasped my hands hard against the steering wheel, keeping it straight. Any quiver out of line would cause me and the rover to spin and flip.

Fighting with the wheel, I was able to maintain a straight course for several hundred kilometers. Looking over my shoulder, the HAB was now fully in vision.

I closed the remaining distance to the HAB, slowing the velocity as I came to a full stop as I had many times before.

I exhaled deeply and closed my eyes.

 

 

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