Ran across this story about the computer aboard Apollo 11, and a fortuitous 0.1-second difference. LUMINARY was never completely bug free. Allan told me about a fascinating series of events that could have easily prevented the first moon landing and might have caused disaster. Allan was the principal designer of the LM’s descent guidance program which steered the LM by gimballing and throttling the descent engine. Whenever the computer commanded the engine to increase or decrease thrust, the engine (and LM) reacted after a short time lag. Allan’s descent program needed a routine to accurately estimate the new thrust level, which could be accomplished by reading the “delta-V” (change in velocity) measured by the LM’s accelerometers. He wrote a short routine that took into consideration, i.e., compensated for, the engine’s lag time, which TRW’s “interface control document”, full of useful information for the programmers, said was 0.3 seconds. It took 0.3 seconds for the LM’s descent engine to achieve whatever thrust level the computer might request. The final version of the thrust routine, which was put into the LM, was written by Allan’s friend Don Eyles. Eyles was sufficiently enthusiastic about the programming challenge that he found a way of writing it which required compensating for only 0.2 of the 0.3 seconds. The IBM 360 simulator showed Eyles’ program worked beautifully. His routine was aboard Apollos 11 and 12 which landed successfully. However, telemetry transmitted during the landings later showed something to be very wrong. The engines were surging up and down in thrust level, and were barely stable. A guy at Johnson Space Center called Allan and informed him that the LM’s engine was not a 0.3-second-lag engine after all. It had been improved some time before Apollo 11’s launch such as to lower the lag time to only 0.075 seconds. Correction of this item in the interface control document had simply been overlooked. Once this discrepancy was discovered, theIBM 360 simulator was reprogrammed to properly simulate the actual, faster engine. Running on the simulator, Don Eyle’s thrust program, with the 0.2-second compensation, exhibited the surging that had occurred on the real flights. But here’s the most interesting fact: the simulator also showed that had Allan Klumpp chose to “correct” Don Eyles’ program by compensating for the full 0.3 seconds that was printed in the document, the LM would have been unstable and Apollo 11 would never have been able to land. By pure luck, Don Eyles was creative enough to write the thrust routine in a way that kept the LM just inside the stability envelope and allowed successful landings! ...

Seriously? I just ran across this little requirement in signing up for a service that I’m now nervous about using: Username: 3+ lowercase letters and numbers, starting with a letter. Password: 8+ Alpha Numeric characters & must include - 1 uppercase, 1 lowercase, and a number. Special Characters are not accepted! No special characters?!? I haven’t been this annoyed since I figured out my database IDE couldn’t handle a schema password with an @ in the name. ...

Testing to see if glial progenitor cells – the early form of neurons and glia in the brain – can be integrated into human brains that are missing these vital building blocks, scientists have injected human progenitor cells into mouse brains. The human progenitor cells went to the correct locations and performed the correct function in the mouse brains…but then this happened: The human progenitor cells are larger, more complex, and have more staying power than mouse progenitor cells in the brains of mice. Which means that over time, the brains of mice injected with these cells are becoming more…human. Goldman’s collaborator (and spouse) Maiken Nedergaard and her team at the Center for Translational Neuromedicine, also at U Rochester, has tested these mice to see if their humanised brains make them smarter. The hu-mice do seem to condition more quickly, and show signs at the molecular level of differences in synaptic connections that suggest they might be cognitively different. ...

…killed by a health care reform bill, pronounced dead at the age of 233. Who knew democracy was so fragile? Who knew our great American traditions of relatively non-violent political change would be so easily broken. All by one bill. Goodbye, America…killed by a piece of government legislation, passed by a majority of the House and Senate, two bodies that we have the opportunity to radically change every two years simply by voting…not even a Constitutional amendment…. ...

New Scientist mentions a study where old mice are rejuvenated by being conjoined with young mice and sharing their blood supply. Have we learned nothing from science fiction and horror? If there’s one lesson to be taken from hundreds of stories, it’s that creating a Fountain of Youth by harvesting from the young always turns out to be a bad idea. ;)

Subject line from today. Refreshingly straightforward. Disturbingly familiar. “You have not had sex with a Russian girl? Come to us and you shall have it!”

I might think different after a while, but I was kind of interested in MacWorld’s live coverage of the event, so I decided to write down some thoughts to see if they survive as time goes on. I really hope at some point they come out with the iPatch. The iPad is an iPhone I can’t fit in my pocket and can’t use to make phone calls. The iPad is an expensive, but lighter and shinier, netbook where I have to pay extra for an hardware keyboard and comparable storage. The iPad has access to the Apps store, so I can run iPhone apps without having to squint at them. Maybe the iBookstore can force Amazon to start supporting epub? I’d get one over the Kindle DX at a similar price. I don’t know about Kindle 2.0 at its current price point. Unlike the iPhone, I could use it for extended reading. One also assumes the Amazon Kindle app will still work. iWork apps are kind of cool. Could use it for presentations at work. I love the data plan pricing, particularly the pre-pay option. I kind of wonder about the whole 250MB plan. That could be fine on the iPhone, but I suspect people would use video on this more frequently. Might have been an awkward design at 16:9, but I was a little surprised at the 4:3-ish screen ratio. Oh well, it’s not a TV. Games will be prettier, faster, and more involving, but I’d need to pick one up to see whether the size would be awkward for a handheld. I like this gadget, but I just can’t see where it would improve my life in the age of the iPhone and netbooks. I’ve already got light-enough computing in a form factor that’s been around forever, and I’ve got good-enough ubiquitous data access. ...

Twitter: I really want to use Twitter to comment on Twitter suffering a denial-of-service attack. That isn’t happening. I wonder if the attack is actually that impressive, or if it’s just taking advantage of something about Twitter’s setup? NetNewsWire and Google Reader: If you like to get your feeds through a desktop client, but still want to have access to them elsewhere, NetNewsWire 3.2 Beta now syncs with Google Reader. Apparently Newsgator is confident enough in it to shut down their own online feed reader. I’m not sure whether I prefer it to Google Reader, or how well it works yet. (I can confirm it downloads the feeds. I haven’t tested the syncing beyond that, however.) ...

IN CONGRESS, July 4, 1776. The unanimous Declaration of the thirteen united States of America, When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature’s God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation. ...

Each summer I go through the same experience of getting really annoyed with how hot my hair is, and thinking about shaving it off. So, I decided to blog some of the reasons I can think of for not doing it, for future reference. 1. I’m a little afraid that, if my hair started growing back, it would end up looking like Notre Dame QB Jimmy Clausen’s hair did his freshman year. Seriously, that dude had some weird spiky hair going on. ...