Category Archives: Mathematics

Business, Economics, Mathematics, Media Criticism, Space, Technology and Society

A Belated Christmas Present To My Kickstarter Supporters

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An excerpt from my project that I just wrote:

I’ll conclude with a discussion on mission risk and reliability. SLS supporters make an argument like this:

The greater the number of flights it takes, the more the probability of successfully delivering the elements needed for a Mars mission is reduced, because that probability is a multiplication of the individual probabilities of success of each rocket flight. For instance, if it takes thirty flights of a vehicle with 98% reliability, the probability of mission success (POM) will be 0.98 to the thirtieth power, or only 55% or so. A rocket with the same reliability for which only six flights are required will have a much better POM: 0.98 to the sixth power, or 89%.

Moreover, because of NASA’s superior experience and processes developed over decades, SLS will probably be greater than 98% reliability, compared to those amateur commercial rockets. SpaceX just blew one up last summer, so their demonstrated reliability is only 20/21 (as of the end of 2015), or 95.2 percent. That means that a mission that required thirty successful Falcon flights would only have 0.952 to the thirtieth POM, or about 23%, less than a one in four chance. Why are you trying to sabotage our Mars plans by insisting on using these dinky, unreliable rockets?

I know that because I don’t have a specific quote, this sounds sort of strawmannish, but there have been arguments like this made by SLS proponents for years. And the logic and math seems indisputable, right?

Well, it’s a lot more complicated than that. In fact, a greater number of flights to accomplish a given job actually increases the chance of mission success. And also in fact, this would only be counterintuitive to someone in the warped space industry, stuck in the Apollo and general “mission” mindset. Let’s unpack the above “analysis,” to see why.

First, it assumes without basis that the loss of a single flight causes the loss of an entire Mars mission, ignoring the fact that the lost payload could be delivered on another flight. The only flight failure that could cause mission failure would be one carrying an irreplaceable mission element. But if we have irreplaceable mission elements, we’re clearly doing it wrong.

We could do a reductio ad absurdum, and assume that we are going to deliver everything for a human mission beyond earth orbit and back in a single launch.

Oh, wait! That’s what we did in Apollo!

For Apollo, the Saturn V carried all of the hardware elements described in the DRM, plus propellant. If the launch system failed, the mission failed. The reliability of the launcher put a ceiling on the POM; if the Saturn was 95% reliable, the POM could be no greater than that, and of course it would be less, because of the potential for failure of any of the other mission elements (as happened with Apollo 13, when the liquid-oxygen tank in the service module exploded). For the launch system, it was all or nothing.

Let’s go back to the truck analogy. Suppose we build the house in the factory, ready to live in, and then deliver it to its final destination on a giant truck. It’s a very expensive payload, because of all the value added in the factory where it was built.

Now the success of getting your house to your building site is totally dependent on the truck not crashing somewhere along the way. Would you really want to make that bet? Because trucks do crash with some regularity. And if it happens, you’ve lost a hundred-thousand-dollar (or more) house. Who would insure that?

That’s why we build houses on site from much smaller, less expensive parts, and we add value by assembling them there. That way, if you lose a shipment, it’s not that big a deal. You just send out another load of cheap cement or plywood or studs or drywall, or whatever.

This is the way we do things on earth. There is nothing magical about space that means we should do it any differently there, except that the one time we successfully did what we’d like to do again—send humans beyond earth orbit—we did it the crazy way, because we were in a hurry, and got away with it half a dozen times.

There will be more to come. BTW, I’ve been struggling to find a quote like that, but we all know that people have made that argument. Anything folks can come up with via crowdsourcing would be appreciated, particularly from NASA officials.

Mathematics, Media Criticism, Political Commentary, Science And Society, Technology and Society

The Cruz Climate Hearing

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Mark Steyn’s thoughts in the aftermath:

In the US Senate, at least on Tuesday, senators wander in and out constantly. Their five-minute “question” sessions are generally four-minute prepared statements of generalized blather followed by a perfunctory softball to “their” witness, after which they leave the room without waiting to hear the answer – and then come back in when it’s their time to speak again at which point the staffer feeds them the four-minute blather they’re supposed to be sloughing off this time round. The video doesn’t capture the fakery of the event because under Senate rules the camera is generally just on whoever’s speaking. Whether this meets the “decorum” of the Senate, it certainly doesn’t meet the decorum of life; it’s a breach of the normal courtesies – and, frankly, Americans are the chumps of the planet for putting up with it. Since the 17th Amendment, senators have been citizen-legislators like any other, and so their contempt for the citizenry who have graciously consented, at their own time and expense, to appear before them demonstrates a profound misunderstanding of the relationship.

Take this guy Brian Schatz, the Senator from Hawaii. He did his shtick, lobbed a softball at his witness, Rear Admiral Titley, and stood up to leave. I said I’d like to respond, and he demurred on the grounds that he was outta there, he had to get back to washing his hair or whatever. I said I’d still like to respond to what he said, and so I did – to an empty chair. A pseudo-parliament is a fine place in which to debate pseudo-science, but “decorum” has nothing to do with it.

There is another kind of basic rudeness, which I have never experienced in a real parliament. If you’re moderating a panel discussion on C-SPAN with five panelists, it’s generally considered polite to distribute the questions broadly. In this case, the Democrats asked no questions of anyone other than their guy – Rear Admiral Titley. For example, there was some extensive discussion of the satellite record: They have the scientist who created and developed the satellite temperature record sitting at one end of the table: John Christy. This is a remarkable scientific accomplishment. Yet they directed all their questions on the subject to the bloke down the other end – Rear Admiral Titley, who knows no more about the satellite record than I do. This is like inviting Sir Isaac Newton to a hearing on gravity and then only asking questions of Mr Timeserver sitting next to him. It may represent the “decorum” of the Senate but in any other area of life it would be regarded as insufferably ill-mannered.

…Unfortunately, the “decorum of the Senate” means that there are never any debates and only performance art, procedurally rigged to the advantage of the posturing preening senator. It’s easy for Fabius Maximus to fight vainly the old ennui at this particular bit of performance art, but in fact it was most unusual. I’ve been told that there’s never been an occasion where two witnesses turned the tables on a senator and bombarded him with questions. If that’s the case, Americans shouldn’t wait another 200 years to do it again. No citizen should consent to be insulted to her face by a mere elected representative.

Certainly, Senator Markey, like so many cowardly bullies, didn’t take it well. He was supposed to come back for his scheduled second round of questions. But, after that exchange, he declined to return.

I have pretty low expectations, particularly from that moron Ed Markey, but I was still surprised and appalled at the ignorant douchery on display by the Democrats.

[Late-afternoon update]

Here are some reflections from Judith Curry.

Business, Economics, Mathematics, Media Criticism, Political Commentary, Science And Society, Technology and Society

Mark Steyn’s Testimony

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There will probably be some reportage of yesterday’s hearing, but Anthony Watts has his written testimony.

[Update a while later]

Bishop Hill has the video of Mark shredding the climate fascists on the committee.

[Update a couple minutes later]

Here is the video: A State Ideology.

[Update a few minutes later]

Here’s the story from Michael Bastasch.

[Late-morning update]

Here’s some whining at The Hill by some idiot from Texas, who thinks that Judith Curry is a “denier.”

Education, General Science, Mathematics, Media Criticism, Political Commentary, Science And Society, Technology and Society

Peer Review

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(From a surprising source) let’s stop pretending that it works.

They can’t do that. It cuts the legs from under one of the primary weapons they use against critics of catastrophic anthropogenic climate change.

[Update a few minutes later]

Related: Senator Cruz’s climate hearing with Judith Curry, John Christie, Mark Steyn et all is today at noon PST. Get out the popcorn.