Jon Goff has been doing yeoman’s work in digging into the ESAS appendices. I’ve done a lot of this kind of architecture trade, and it is indeed extremely sensitive to assumptions. And from just this excerpt, while I haven’t read it myself (I can’t find the time from my day job, and I’m glad that Jon did), it sure looks like the game was rigged (which isn’t at all shocking in the context of all of the problems that have arisen). I was simultaneously saddened and amused by this:
I know that Mike Griffin was claiming that part of the reason for doing Ares-I was to teach NASA how to design launch vehicles again, and I guess we have documented proof of the need.
Seriously though, this is a common rookie mistake. You don’t go basing decisions worth tens of billions of dollars on an unvalidated design tool. Now, this isn’t saying that INTROS is a useless tool, just that it obviously doesn’t capture all the state of the art in stage design, and until it does, its results ought to be taken with the appropriate sized (apparently multi-ton) grain of salt.
Well, apparently NASA does exactly that. Or at least it pretends to base them on it. I don’t think that they’re going to pull the wool over Norm’s eyes, though.
One of the things I learned from my CFD days (or would it be “CFD daze”?) was that to get code to iterate stably, and produce results that “looked right”, one often had to add fudge factors called “dissipation terms”, among others.
I learned then that just because the numerical model produces a result, does not mean that it produces a physically valid result.
I have retained that lesson throughout all the climate change modeling discussion.
“I learned then that just because the numerical model produces a result, does not mean that it produces a physically valid result.”
As an ex-software engineer, I know what you mean. In computer science that principle is known as GIGO (pronounced jeejoe which stands for “Garbage In, Garbage Out”
Rand, I too am hopeful about Norm, but (like you) have seen so much s**t go on as far as NASA is concerned. Given past history, I’m not sure of what anyone will actually do when decision time comes.
Sorry made a mistake in my HTML. Here is my last post properly formatted
“I learned then that just because the numerical model produces a result, does not mean that it produces a physically valid result.”
As an ex-software engineer, I know what you mean. In computer science that principle is known as GIGO (pronounced jeejoe which stands for “Garbage In, Garbage Out”
Rand, I too am hopeful about Norm, but (like you) have seen so much s**t go on as far as NASA is concerned. Given past history, I’m not sure of what anyone will actually do when decision time comes.
(Hmm. Rick, is that a regional pronunciation, like jigawatt? In Southern California, I always heard it pronounced guy-go.)
Mike, to tell you the truth I don’t know. I too thought it was pronounced guy-go until I saw this phoenetic pronunciation in a book in the ’70s and I don’t remember what book.
Everybody tells me URL is pronounced “You-Are-Elle.” But since I am not Elle I ignore them and pronounce it “Earl.”