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“ NASA announced that they had identified the Power Control Unit (PCU), which is part of the SI C&DH, as the source of the problem” So they had a spare PCU tha

“ NASA announced that they had identified the Power Control Unit (PCU), which is part of the SI C&DH, as the source of the problem” So they had a spare PCU that they switched to. Hubble was launched in 1990. Is 30+ years normal for a continuously operating PCU? What is the expected lifespan of the “new” PCU that has been sitting this whole time?

ceejayoz 5y ago
Not just continuously operating, but in a very harsh environment. Impressive.
BeefWellington 5y ago
NASA's hardware is deployed in anything but normal circumstances, so normal for them vs normal for the consumer are vastly different things. Given the longevity and how well engineered things are for their other projects, I'd have to say yeah it seems pretty "normal" to me. It seems like they overengineer and quality control to the point of doubling planned mission length, if not longer. My cynical take on it is they do it this way because of the nature of their funding rather than any specific engineering goal.
- rtkwe 5y ago
  Part of the source of the discrepancy is the planned mission is basically just what they get initial funding for not everything they would like to do and the entire mission length they'd like to use. Because launch costs are such a big part of the costs of ever replacing a Hubble or a Curiosity it makes sense for them to last longer than they're funded for because most likely they'll continue to get some funding a long as there's good science and the equipment is still usable. Also the cost of failure is pretty high, if you have something break early there's not another rover/satellite program there to replace it the science just doesn't get done until the next program in 10 years gets sent unless someone else was sending a similar device to that destination.
Steltek 5y ago
Anyone claiming to have a real answer to that would be torn to pieces by Richard Feynman. I think you'll need to be satisfied with best guesses and a metaphysical "as long as it lasts".
izacus 5y ago
The designed life expectancy of Hubble as a whole (and thus, by extension the minimal designed life expectancy of all components) was 15 years. It's now been operating for 30 years, doubling its design lifetime and intent to be replaced.
phonon 5y ago
The original PCU was replaced in 2001. https://esahubble.org/about/history/sm3b_replacement_of_pcu/ https://esahubble.org/about/history/sm3b_replacement_of_pcu/

ceejayoz 5y ago

Not just continuously operating, but in a very harsh environment. Impressive.

BeefWellington 5y ago

NASA's hardware is deployed in anything but normal circumstances, so normal for them vs normal for the consumer are vastly different things. Given the longevity and how well engineered things are for their other projects, I'd have to say yeah it seems pretty "normal" to me. It seems like they overengineer and quality control to the point of doubling planned mission length, if not longer. My cynical take on it is they do it this way because of the nature of their funding rather than any specific engineering goal.

rtkwe 5y ago
Part of the source of the discrepancy is the planned mission is basically just what they get initial funding for not everything they would like to do and the entire mission length they'd like to use. Because launch costs are such a big part of the costs of ever replacing a Hubble or a Curiosity it makes sense for them to last longer than they're funded for because most likely they'll continue to get some funding a long as there's good science and the equipment is still usable. Also the cost of failure is pretty high, if you have something break early there's not another rover/satellite program there to replace it the science just doesn't get done until the next program in 10 years gets sent unless someone else was sending a similar device to that destination.

Steltek 5y ago

Anyone claiming to have a real answer to that would be torn to pieces by Richard Feynman. I think you'll need to be satisfied with best guesses and a metaphysical "as long as it lasts".

izacus 5y ago

The designed life expectancy of Hubble as a whole (and thus, by extension the minimal designed life expectancy of all components) was 15 years. It's now been operating for 30 years, doubling its design lifetime and intent to be replaced.

phonon 5y ago

The original PCU was replaced in 2001. https://esahubble.org/about/history/sm3b_replacement_of_pcu/ https://esahubble.org/about/history/sm3b_replacement_of_pcu/