Archive for May, 2010
Excellent video of the space shuttle Atlantis making it’s last jump into space.
One slow day at work we watched a NASA feed of a shuttle launch from T-5mins to fuel tank separation (~+8min). One co-worker is a walking encyclopeida of the shuttle and it’s systems so it was like being on a tour of the launch process.
If you notice at launch, water (350,000 gallons in 41 seconds) floods the pad. It’s not to cool things off, it’s added sound suppression because the shockwaves from the engines were actually damaging the Solid Rocket Boosters and Shuttle wings.
The shuttle is clamped down to the pad and won’t launch until the explosive bolts blow and the clamps let go. Hence the impression that the shuttle leaps off the pad. The Saturn Rockets that flew the Apollo missions worked the same way. Astronauts often have colorful ways to describe the feeling of going from rumbling on the pad to instant high-G acceleration.
The shuttle launches “Downrange”. Although it seems it’s going straight up the shuttle is really rolling onto it’s back as it launches; because it’s lateral speed around the earth that sends it to orbit, not necessarily altitude alone.
At an altitude of about 35,000ft the shuttle hits Max Q which is where the speed and air density create the maximum dynamic pressure and stress on the shuttle. After this point speed increases but due to low air density the stresses on the shuttle lower making it a major milestone in the launch.
The Challenger disaster happened around Max Q; when stress on the structure was at it’s peak the SRB mount broke causing the SRB to turn into the fuel tank. As the fuel tank broke up the orbiter veered out of position and the aerodynamic forces at Max Q caused the orbiter to disintegrate (it didn’t actually “explode”).
As the shuttle launches if you listen to the NASA sound feed you’ll hear Ground Control announce the passing of certain Abort Modes.
-First is Return To Launch Site (RTLS). The shuttle would ride until the SRBs burn out (they’re like bottle rockets and can’t be stopped once they’re lit), then shut off main engines, jettison the 3/4 full fuel tank and glide back to Florida.
-Next is Transoceanic Abort Landing (TAL). Upto about +8mins the shuttle can abort, run out the SRBs and main engines then land in Europe about 25 minutes after launch (beat that Concord!). Weather conditions need to be good at Florida and at least one of the three Europe landing sites. Prep at the sites begins 2 days in advance of launch.
-Abort Once Around (AOA) is rare. It’s when the shuttle has too much speed to make Europe but not enough for a stable orbit. The Shuttle would return to a Florida landing 90mins after launch.
-Last is Abort to Orbit (ATO). Basically orbit can be attained, but possibly not as high as they wanted. But it does give the opportunity to think things through and either come up with a solution or find a way down. It’s only been invoked once, the Challenger had one of it’s main engines shutdown during launch but made it to orbit. The mission was salvaged and it landed safely.
Google of course is recognizing the day with a custom header on www.google.com. The trick is that the google title is playable; open up google and hover over the title. It’s worth it for the nostalgia of the authentic sounds alone.
Like most games of the time Pac-Man is Japanese, Paku Man. “Paku Paku” is a Japanese mimetic word for the sound of eating, like “Doki Doki” is the sound of a fast beating heart. So the name comes from the act of eating; converted to latin the Japanese name パックマン becomes Pakkuman, which we simplified to Pac-Man.
The ghosts Inky, Blinky, Pinky, and Clyde are of course American names. The ghosts original Japanese names describe their attack personalities; roughly translating to Chaser, Ambusher, Fickle and Stupid.
Pac-Man only has 255 levels, all are the same; but due to a programming issue the game won’t work past 255. Because computers at their core work on binary a certain number of bits is required to represent the data. In binary 8 bits has a maximum number of 255 (this is why IP addresses don’t go over 255 per octet). Pushing for that 9th bit to be able to count to 256 causes Pac-Mac to only render half the screen.
Perhaps this was a deliberate oversight by the programmers, after all who would ever play a game through 255 levels?
Along with the Atari ET game, the port of Pac Man to the Atari 2600 was one of the reasons for the video game crash of 1983. As good developers fled Atari due to publishing rights arguments games with known good potential like Pac Man were cranked out as pieces of garbage and the gamer market responded by abandoning systems. Nintendo would pick up the pieces 2 years later.
“Back in the day” it was common for a game to be produced by only one or two programmers who would get billing on the title screen. One of my favorites was “Floyd of the Jungle” by a certain Sid Meyer in 1982.
Atari wanted all their games to be “by Atari” on the title screen. Hard working programmers felt they didn’t get the recognition they deserved and fled starting up their own programming companies like Activision.