Because most failures are due to the accumulated “power up” time. Once you get past the “infant mortality” phase of electronic failure, components usually settle into a long life of reliability. The real enemy is heat and a couple of decades of operation will cause them to dissipate a lot of it. If you have shared duty (both powered up all the time, which doubles your power budget with no increase in performance), you’ll have two worn out systems when one of them fails. The second failure is sure to come soon after.

Once you protect against temperature extremes and shield against most of the radiation, space is actually a pretty benign environment for electronic storage. True, your components can be zapped by a cosmic ray while it’s sleeping, but that can happen to the active ones as well.

- Jack

Let me tell you a little story in that regard. My first job out of school (slightly after the Earth cooled) was as a flight support contractor to an Air Force satellite program at the Sunnyvale Air Force Station (the “Blue Cube” to all you locals). Our program office was in the older part of the station, which was built in 1957.

Since there are no windows, every room was equipped with battery powered emergency lighting. It was the job of some poor Airman 2nd Class to walk around the whole building once a month and hit the “Test” button on each of the several hundred units in the facility. I’m sure they considered it some useless busywork that the military is so good at creating. After all, the facility was connected to a high-priority service from the local utility which had never failed in the 20 years the base had been there. Even if it did, there were 50 MW of gas turbine generators ready to take over (which had been idling continuously for 20 years).

As you’ve probably guessed, one day while I was there the power from the utility failed. I never found out the reason, but it was highly suspicious since the switch that moved the connection from utility to the generators stuck half way so the facility was completely disconnected. As designed, the emergency lighting came on…and then went right off again in less than 30 seconds. The batteries were lead-acid and were all 20 years old. The plates had all oxidized to the point of uselessness. They could power the lamps for the 5 seconds or so of the test, but the larger system degradation went undetected.

- Jack

SLC: I have had enough of your rude comments. This is your last chance. Shape up, or I will start deleting your comments as they come in, and mark them as spam.

OK, fair enough, I will attempt to politely respond to Mr. Shanes’ comment. It appears that Mr. Shanes’ position (and possibly Dr. Plaits’) is that, unless NASA continues to support the manned space program, Congress will cut back on all spending for space activities. If that’s the case, then it would seem that the proponents of space activities are unable to provide a suitable justification for their program. In that event, then, maybe the space program should be curtailed. I don’t believe for a moment that such justifications don’t exist. The value from the spinoffs alone from the space program (e.g. the computer I am typing this comment on) provide, IMHO, a strong argument all by themselves, even without mentioning the enormous scientific achievements resulting from the program over the last 40 years. It’s time that NASA and its supporters make that case!

My position, and absent the snark, that of Profs. Park and Weinberg is that all of the above would have been achieved if no human had ever gone into space at all. In fact, I would argue that even more spinoffs and even more scientific achievements would have occurred if the funds spent on the manned space program had been spent instead on the various unmanned activities, many of which never got funded due to lack of resources.