I’ve gotten a few comments on this post that I want to respond to on the front page. They’re subjects that I’ve discussed before, but there are probably a lot of new readers here, since many of them presumably came via the link from he whose links must be followed and NRO.

Several people expressed comments along the lines below, but I’ll just respond to this particular one, since it’s pernicious, and I commented at some length on this right after Columbia was lost last year.

I take some offense at the idea that, since we’re planning to replace the shuttle fleet anyway, we can send them up to do more dangerous missions because we don’t need them for much longer. I’m sorry, but if the safety of the astronauts is in question, as you indicated, then we should not send them up. The shuttles may be expendable, but the humans are not.

I’m sorry that you take offense, but any other idea is irrational, despite your claim to be a science and math teacher. Read again what you wrote. You are saying that human life is infinitely precious, and that there is nothing that’s worth its risk.

Now, it’s debatable whether or not a Hubble repair is worth that particular risk, but the attitude expressed here will make the president’s new human exploration plans moot, since we cannot guarantee the safety of astronauts who go to the moon, or even into low earth orbit, let alone Mars.

I know that this will sound politically incorrect, but the reality is the exact opposite of this reader’s commentary. We have more astronauts than we know what to do with, but we only have three orbiters, and they are essentially irreplaceable, since most of the tooling for them and knowledge of how to build them is gone. It would take several years, and many billions of dollars to replace one, and it would be an extremely foolish expenditure. So the decision as to whether or not to save Hubble with a Shuttle has (or at least, should have) little to do with crew safety, and everything to do with whether or not we’re willing to risk a third of the remaining fleet. In my opinion, it is worth it, if the odds are 98% success.

This is why the notion that we should send the Shuttle up without crew is senseless. The major asset at risk is the orbiter itself, and sending it up sans people (as another commenter suggested) does nothing except dramatically reduce the possibility that the mission will be successful, at very high cost. Hubble was designed to be serviced by astronauts, and that’s the most reliable means for it to be serviced this time as well. If a telerobotic mission is successful (and I consider such a mission very high risk–a subject on which I’ll be discoursing further in the coming days), it can be done without Shuttle, and an uncrewed Shuttle adds zero value to a Hubble repair mission.

Let’s get this straight once and for all, folks. The primary purpose of sending an orbiter into space is to deliver astronauts into space–the other cargo capacity is just lagniappe. Unmanned orbiter missions are largely pointless, given their ridiculously high cost, yet the notion continues to surface, among both the public and people who should know better, like Congressmen.

This commenter below is entitled to his opinion that:

Hubble needs to be replaced, and not having a telescope in space for a couple of years isn’t a big deal at all.

But his opinion is apparently not that of the space-interested public, or there wouldn’t have been such a hue and cry when NASA made the decision. There’s no question that Hubble needs to be replaced, but it’s continuing to provide good science (and beautiful images) and given that we’re going to be continuing to spend billions on the Shuttle program, money largely wasted, it would be nice to get a little value out of it for this mission to keep the system alive until it’s replaced with something better.

Finally, as to this:

Your probability calculations tell me (I’m a math and science teacher, for the record) that you have fallen into the infamous “gambler’s fallacy”. Basically, the gambler’s fallacy goes something like this: if I flip a coin, and it lands on heads, then the next time I flip the same coin, it is more likely to land on tails, since the coin should land on heads and tails in roughly even amounts. In fact, the probability on the second flip is still exactly 50/50. What you have said here is equivalent, though with a smaller probability. You seem to be claiming that, because the shuttle has a 98% (or so) success rate, and the remaining shuttles have made a large number of successful trips, that the probability of them being destroying is increasing with each successful mission. While this may be true from an engineering standpoint (since parts and materials degrade over time), you can not reach that conclusion by looking at straight probabilities.

I have no idea how he could so misinterpret what I wrote. I am claiming no such thing, and I don’t know how I even “seem” to be claiming it. I repeat: “At that reliability, there is a forty percent chance of losing another orbiter (which would cost billions and years to replace) in the next twenty five flights. There’s a two in three probability of losing one in the next fifty. That means there’s an excellent chance of losing one over the next ten years, at an optimistic flight rate of five per year.”

My claims are that if there is a two percent chance of loss per mission:

• There is a two percent chance of losing the Hubble mission, which is, after all, a…mission
• There is a forty percent chance of losing an orbiter and crew in the next twenty five flights
• There is a sixty seven percent chance of losing one in the next fifty flights

With which of these statements does our math and science teacher disagree? Which of these statements represents the gambler’s fallacy, or says anything about extrapolating the probability of the success of the next flight from past performance?