4 ms·

I don't want to rain on their parade but with a design life of 90 days and the rovers still operating after 6 years (2160 days) this is an engineering failure.

by dmfdmf 16y ago

I don't want to rain on their parade but with a design life of 90 days and the rovers still operating after 6 years (2160 days) this is an engineering failure. Why? These robots were way over built for their mission which means they probably cost much more than they should have. Its one thing to get lucky and extend a mission a few months past the design life but 24 times the design life means they could have been built for much less. I hope the design team goes back and learns from this and incorporates the lessons learned in future missions.

CapitalistCartr 16y ago
I think you're misunderstanding the design parameters. Most of the cost of a mission to Mars is getting there. The actual rover is cheap by comparison, so it pays to pack as much into each mission as the weight limit will allow. The big risk is mission failure, so the design goal is 100% certainty. The result is that the odds of it lasting for several/many times the design life is pretty good. Imagine if your car were designed to be as certain as technology would allow that it would run, trouble free, for 100.000 km. The odds that it wold last many times longer are pretty good.
- camiller 16y ago
  The rovers also had to be designed to withstand the rigors of interplanetary transit and landing on Mars. The driving around bits are less prone to damaging the rovers.
InclinedPlane 16y ago
Cutting back on the design and construction of the rovers such that they had very little chance of surviving significantly beyond 90 days would probably not have reduced total mission cost significantly, due to fixed overhead in designing the instruments and the rover overall as well as the quite significant launch costs. However, it would have drastically increased the risk of failing to survive 90 days and completing the primary mission. Even sending $10 of dime-store electronics duct-taped together to the surface of Mars would cost about $150 million dollars, not including operational costs, that cost structure dictates that you should ensure a pretty high chance of success for your primary mission. As it turns out, engineering the rovers to have a high probability of surviving 90 days and returning excellent science data in that time frame means that you have a significant probability that they will survive for much longer than that or indefinitely. Spending, say, 10 or 20% "too much" on the overall mission cost (a SWAG but not a bad one, I think) in order to ensure a 90-95% chance of completing the primary mission with some lower chance (say 30-50%) of a several years long extended mission is an excellent ROI. In contrast saving a mere 10-20% and lowering the chance of completing the main mission to, say, 50% and the chance of an extended mission to near 0% is not a good ROI at all. P.S. One of the main constraints on rover longevity is power production falloff due to dust buildup. Prior to these rover missions there were a lot of unknowns about dust buildup and as it turned out there have been some rather lucky environmental conditions which have saved the rovers from death that could not have been anticipated before hand.

by dmfdmf 16y ago

CapitalistCartr 16y ago

I think you're misunderstanding the design parameters. Most of the cost of a mission to Mars is getting there. The actual rover is cheap by comparison, so it pays to pack as much into each mission as the weight limit will allow. The big risk is mission failure, so the design goal is 100% certainty. The result is that the odds of it lasting for several/many times the design life is pretty good. Imagine if your car were designed to be as certain as technology would allow that it would run, trouble free, for 100.000 km. The odds that it wold last many times longer are pretty good.

camiller 16y ago
The rovers also had to be designed to withstand the rigors of interplanetary transit and landing on Mars. The driving around bits are less prone to damaging the rovers.

InclinedPlane 16y ago

Cutting back on the design and construction of the rovers such that they had very little chance of surviving significantly beyond 90 days would probably not have reduced total mission cost significantly, due to fixed overhead in designing the instruments and the rover overall as well as the quite significant launch costs. However, it would have drastically increased the risk of failing to survive 90 days and completing the primary mission. Even sending $10 of dime-store electronics duct-taped together to the surface of Mars would cost about $150 million dollars, not including operational costs, that cost structure dictates that you should ensure a pretty high chance of success for your primary mission. As it turns out, engineering the rovers to have a high probability of surviving 90 days and returning excellent science data in that time frame means that you have a significant probability that they will survive for much longer than that or indefinitely. Spending, say, 10 or 20% "too much" on the overall mission cost (a SWAG but not a bad one, I think) in order to ensure a 90-95% chance of completing the primary mission with some lower chance (say 30-50%) of a several years long extended mission is an excellent ROI. In contrast saving a mere 10-20% and lowering the chance of completing the main mission to, say, 50% and the chance of an extended mission to near 0% is not a good ROI at all. P.S. One of the main constraints on rover longevity is power production falloff due to dust buildup. Prior to these rover missions there were a lot of unknowns about dust buildup and as it turned out there have been some rather lucky environmental conditions which have saved the rovers from death that could not have been anticipated before hand.