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Coasters to Face G-Force Limits?
jonerik writes "NBC News is reporting that today New Jersey will begin examining the possibility of placing limits on roller coaster G-forces. Pointing out that the G-forces on coasters are considerably greater than even those experienced by astronauts and race car drivers, legislators on both the state and national levels want to start reining in coaster G-forces which have been blamed for a number of injuries and deaths over the past few years. Pansies. Why do they think people ride roller coasters to begin with?"
Space launches have steadily reduced their peak G forces over the years. During the Mercury and Gemini programs, the Astronauts were exposed to as much G force as modern jet fighters do in a dogfight, and for as long. The heavier Saturn launch system of Apollo was gentler, and the Space shuttle is very tame by comparison. Russian cosmonauts still get a better (in roler-coaster terms) ride than their American counterparts.
Given how tame the shuttle is, maybe it's technically true, if misleading, to say that roler coasters give the rider more G that an Astronaut experiences. (They did after all say "astronaut", not "cosmonaut") A space shuttle jockey, just barely goes over 3G. Some roler coasters may peak at 5. But here's the difference: The shuttle sustains the 3G for the entire duration of the post-SRB-separation boost. That's several minutes of continuous burn. I doubt whether any roler coaster ever peaks over 3G for more than 2 or 3 seconds at a time, if that.
The physiological risks associated with high G are not determined by the magnitude of the G alone, but mainly by other factors:
The duration that high G is sustained. Long duration deprives the brain of blood long enough to cause very bad things to happen. No real risk there on roler coasters.
The onset-rate. How suddenly the G force starts and stops. High onset rates cause all kinds of problems, including back and neck problems, inner ear problems, and even brain dammage in extreme cases. Once again, no issue in a well-designed roler coaster.
Head movement. High G forces, especially combined with high onset rates, are aggrivated by sudden head rotation. This can be a problem even if the G forces are only momentary. Inner ear problems can result. Roller-coaster designers have little control over this factor, so perhaps it is a real concern.
Negative G. (Negative means the blood rushes to your head). High negative G can cause all kinds of problems, including burst blood vessels in the eyes. I've personally never heard of a roler coaster that goes beyond about -0.5G or so, and even then for less than a second, so I doubt that this is an issue.
Sudden transitions from positive to negative, or vice-verca. All the bad things associated with high positive G are accentuated if it immediately follows a period of negative. And vice verca if negative follows a period of positive. This will become a real issue if roler coasters ever start exploring the negative regime. Frankly, I doubt that they will. The average rider views positive G's as exhilirating fun, but would find negative to be obnoxious and uncomfortable.
Frankly, I'm much more worried about the structural design and maintenence of the coaster than the G-profile. But then, I've flown to WAY higher positive and negative G forces than either roler coaster or space shuttle experience, and I know the breathing techniques, and I know to keep my head relatively still. Roler coasters all seem really disappointing to me.
Not to have their bodies exposed to more forces and danger than most astronauts ever experience
From the original post:
the G-forces on coasters are considerably greater than even those experienced by astronauts and race car drivers...
I flew military jets for 9 years, and I think these comparisons are crap. When people used to ask me how jets compared to roller coasters, I would tell them that the two experiences are totally different. It's a matter of scale. Sustaining 4G or more for even 10 seconds, let alone 30 or 60 seconds or more, is an experience that simply cannot be reproduced by any rollercoaster that can fit in a theme park. The effects of the sustained G are DRAMATICALLY different than the one or two second hits (or three or four...whatever) felt on a high performance rollercoaster.
I recently road with my brother on a rollercoaster that I considered to be quite exciting, with corkscrews and consecutive loops, and when it was over he asked me how many G's he thought we had pulled. Based on the sensations I had felt (compared to my years in jets) I guessed 1.5-2. I was surprised to see a brochure later that claimed the ride pulled 6G. The two or three second hits just didn't have time to register.
Another example: a person using an ejection seat pulls an ongodly amount of G -- something like 30 or 60, although the actual number escapes me. Obviously this is enough to kill a man, but the brief time period involved make it survivable. I've known people who ejected and were able to walk around with no problem immediately afterward.
The point is that comparisons to astronauts and race car drivers is misleading. The maximum G must be examined only in conjunction with the period of time over which the G occurs. Brief hits DO NOT COMPARE to sustained G. Maybe rides should be limited and maybe they shouldn't, but the forces faced by astronauts are not part of the debate.
Evil is the money of root.
In this context, positive and negative Gs are relative to the body orientation: positive Gs are directed from head to feet; negative Gs are directed from feet to head.
In physics, there may be no difference between positive and negative Gs, but there are definite physiological differences in how the body reacts to positive and negative Gs, and how much the body can tolerate in each direction. Like the previous poster said, negative Gs cause increased blood pressure in the head, which can lead to bursting blood vessels. Contrariwise, positive Gs cause decreased blood pressure (and flow) to the head, and can eventually cause blackouts.