Friday, May 30, 2008

What happens when the science consultant to BSG gives a talk on Halo?

This.

"The apparent gravity on Installations 04 and 05 is close to that of Earth. For a Halo with a radius of 5,000 kilometers to simulate one Earth gravity, it would have to spin with a tangential speed of slightly over seven kilometers per second. That implies that the Halo would rotate once every hour and fifteen minutes, or 19 ¼ times a day."

"An object—a soldier, an Elite, a Scorpion MBT, a Warthog recon vehicle, anything—in direct contact with the surface of the ring would perceive the centrifugal force to be the equivalent of gravity. Anything not in direct contact would tend to follow basic laws of dynamics, but laws that might seem counter-intuitive at first. On the second level of Halo: Combat Evolved (a level called “Halo,” in fact), Master Chief can see a waterfall shortly after making ring-fall.

Figure 2 shows the results of computer simulations of the trajectory of one drop of water over the waterfall if it were subject to Earth’s gravity, and the trajectory of one drop of water on a Halo—assuming that the waterfall is 305 meters (1,000 feet) high and oriented along the Halo’s spin direction. We see that a drop would fall two meters farther on a Halo than on Earth. That’s not a great difference, but if the water flow were oriented perpendicular to the spin direction, it would deflect two meters to the side, which would look odd for somebody used to viewing terrestrial waterfalls."


"The ring’s spin would have an even more pronounced effect on objects with a longer time of flight. While most of the combat in Halo takes place at close range, let’s assume we want to use our M808B Scorpion Main Battle Tank, which fires hypervelocity rounds, as a piece of artillery and fire projectiles at a much greater distance. Entry-level physics students learn about trajectories—that the trajectory of a projectile fired from a cannon takes the shape of a parabola (actually, an ellipse, since the trajectory represents a partial orbit). In the absence of wind, a round fired straight up will return straight down, and completely ruin the day of whosoever fired it. Long range trajectories on a Halo would be quite different. Figure 3 shows the results of computer simulations of long-range trajectories of rounds fired from the inside surface of a 5,000-kilometer ring spinning at nineteen times per day. The assumed muzzle velocity was 1,000 meters per second. Figure 3 shows the trajectories for initial barrel elevations of thirty, forty-five, sixty, and ninety degrees above local “horizontal,” both in the direction of the ring rotation (+X) and in the direction counter to the ring rotation (-X). We can see that a round fired straight up does not, in fact, return to where it was fired, but rather eighteen kilometers downrange due to the seven kilometers per second speed that the round had before it was even fired. Note a marked asymmetry between projectiles fired in the spin direction as opposed to the anti-spin direction. Rounds fired in the spin direction have a greater initial horizontal velocity, and impact the ring sooner than those fired in the direction opposite to the ring’s spin. A rocket fired from a launcher, or a projectile from a fuel rod gun, would suffer similar deflections if it had to travel long range."


Now I want to hear his opinion on the merits of the Viper Mk II versus the Mk VII.

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