The three astronauts you are referring to died on the launchpad during an exercise (Apollo 1). Virgil (Gus) Grissom was one of them, you'll remember him from the previous programs, he was one of the original 7. His mercury capsule sank and was recovered a few years back, I think it's on display at the Smithsonian (never been there, wish to go sometime). They tragically were burned alive, NASA had overpressurised the capsule with O2 instead of going the safe way and using some inert gas. A short lighted up the O2, fire spread quickly.
Check Grissom's biography <a href='http://www.hq.nasa.gov/office/pao/History/Apollo204/zorn/grissom.htm'>here</a>
My wife's family worked at the cape during those years (she is a Titusville native), albeit on unmanned launchers, but a very good friend worked for Pratt Whitney and designed the engines for the Saturn rockets. He was on the pad that dreadfull day. My friend worked on interesting problems with Von Braun, most notably, multistage rockets like the Saturns had not been tested with a burn of the second stage in orbit in zero G. The combustible, at that point, is freely floating around in the tanks and some gravity needed to be created to push the combustibles down to the supply lines.
The fact that these heroes died on the pad allowed the flight director of Apollo 13 to say "we've never lost Americans during flight, it sure as hell is not going to happen on my watch" I paraphrase, but it's close enough!
That people, Americans at that, doubt that Americans have been to the moon, on the moon, and back just floor my ass!
Soviets had plans to go to the moon too, of course, they freely discussed all their successes, but masked their failures. Russians lost their chance to go to the moon when their rocket distintegrated on the launch pad during lift off. Scientists at NASA, remember the race for space supremacy was on along with the cold war, named the failed russian project to fly to the moon, project kaputnik.
Russians have had many successes with probes, notably to Venus, that we have not had. Their techonlogy was lower grade, but reliable, or apparently so since we can't be sure of failures, although the "City of the Stars" was a favorite spot of ours to spy on.
After the Apollo-Soyouz link up in orbit, an american astronaut (pleonasm I suppose since russians call them cosmonauts) commented on the mechanism that recorded and followed the flight plan. At the base was something akin a copper cylinder, a cursor, and an small motor to spin the cylinder to allow the cursor to follow the grove.