<div dir="ltr"><div><div>Sorry to bring this up, but the issue is escalating and I could use some insight from people who've actually parachuted. In the last session the great troll had a couple of extra-large parachutes made, by a talented tailor who had never been introduced to the concepts of parachutes before (he's from a universe in which there is considerably less gravity than most).<br>
<br>The troll has never seen a parachute landing. His sole exposure to anyone who HAD was a few seconds of grabbing a parachute off a WWII plane that was under fire, and then a few seconds of combat while he killed the paratrooper who was fighting to keep his parachute.<br>
<br></div>Here's the question: how hard it is to make your first parachute jump with absolutely no training or experience? What would be some likely outcomes?<br><br>In this case, it wasn't a 500-mile jump to the Ringworld (that may happen after the troll gets out of traction). It was a fall of about 800 feet, in which a secondary parachute opened at about 100 feet up. He was wearing full plate mail and carrying a greatsword and troll maul. According to my reckoning, both of his legs are not only broken, but are effectively maimed - although luckily for him, he's in the best hospital in a high-magic world. Does anyone think that that's unreasonable? Because I suspect that I'm going to get a lot of arguments on this one.<br>
<br></div><div>Also, do you think that his leg armor would survive the fall?<br></div><div><br></div>->Peter<br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sun, Apr 7, 2013 at 1:09 PM, Styopa <span dir="ltr"><<a href="mailto:styopa1@gmail.com" target="_blank">styopa1@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">All credit to Niven. He's an intelligent fellow, and it's not casting any aspersions on him to simply say that the math behind a ringworld is extraordinarily complex, a nearly-unique frame of reference, and one could spend - especially in 1970, when Babbage's Children were barely toddlers - much of one's life down the rabbit-hole of computations trying to "get it right". Personally, I'm much happier that Mr. Niven DIDN'T do so, and instead actually wrote the book, physics-warts and all.<div>
<br></div><div>Frankly it's a fun exercise, and has provided some entertaining discussions between myself, and people who know more about physics than me - actual rocket scientists, some of them. One (probably more usefully) spends most of his day working with the physics of golf balls. (Well, I often do as well, but not to the MATHEMATICS of them. Mine is a more....experimental...approach, using lots of profanity.)</div>
<div><br></div><div>The fact is that (unless for some reason my posts didn't make it to these lists) I've proven with reasonable accuracy that our Armored Troll would fall the 500 miles in 406-some seconds (in a vacuum), and would hit at 000's of miles per hour. Certainly, he'd hit terminal velocity before that, but he would MOST CERTAINLY impact with a most-terminal of velocities - probably several hundred miles per hour.</div>
<div><br></div><div>Oh, and re the 'atmosphere' and 'spill walls' - yes, the point observed is accurate. The height of the walls DIRECTLY impacts the atmospheric densities on the surface of the ring. Assuming as physics-shorthand that the 1g force in the revolving frame of reference is uniform, the <br>
</div><div><br></div><div>I'm NOT an atmospheric scientist, nor do I know any. I'd speculate however that:</div><div>- in this very odd frame of reference, I couldn't find any data on the surface cross section of liquids, but I *suspect* that it would be a shallow parabola, possibly a hyperbola. But for this I'm just going to assume it's uniform in effect at the surface, because in any case I suspect a varying pressure effect laterally would anyway be homogenized by the air shifting around anyway. For this model, assume the cross-section of the atmosphere height is horizontal (to someone on the ring-surface).</div>
<div>- ANYWAY, I checked against atmospheric height and surface pressure for Venus, Mars, and Earth... just to see. It turns out there's a fairly straight log-function that describes the relationship. For Mars (atmos height ~25km) = surface pressure is 600 pascals. Earth (~100km) 101kilopascals. Venus (~250km) 9 megapascals. Assuming that the atmospheric behavior is the same when extrapolated linearly, a 500km-high side wall means probably 100 megapascals....or the pressure of water at 10000m depth (yes, 10km). </div>
<div>The point of this atmospheric diversion?</div><div>To illustrate only that the 500mile spillwalls DON'T necessarily mean it's atmosphere 'all the way up'. In fact, given the quality of the Ringworld Engineers, it would make sense that they would OVER engineer the spillwalls to defend against pretty much anything that would 'cost' the structure airloss, if they could, so 500 mile sidewalls (800km) still still might only mean 100km atmosphere height.</div>
<div><br></div><div>Simple enough...except for our trollish friend.</div><div><br></div><div>Because this means that at least 7/8ths of his 'fall' from the edge (from the PoV of the surface), or of his fling-sideways (from the PoV of an outsider watching), is in vacuum....meaning he's going to 'hit' atmosphere at 000's of mph, relative. </div>
<div><br></div><div>Taking into account the atmosphere, then, suggests that he would fall most of the way without atmospheric hindrance, until he hits atmosphere at something like Mach 7, and really doesn't enjoy the next few moments.</div>
<div class="im">
<div class="gmail_extra"><br><br><div class="gmail_quote">On Sat, Apr 6, 2013 at 9:02 PM, Sven Lugar <span dir="ltr"><<a href="mailto:vikingjarl@gmail.com" target="_blank">vikingjarl@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
Ringworld is based on Larry Niven's book of the same name. I came to
know him fairly well back in the days when we both going to Cons
& to English Regency Dancing events. He always struck me as very
stringent in using his science in books. I remember an occasion of
him discussing the physics of it & also mentioning that it was
based on the work of Dyson (of the "Dyson Sphere concept"). So I
suspect that he is probably correct in his assumptions to make the
concept work. Perhaps someone who is more versed in these things can
shed some light on this.<br>
<br>
Sven<br>
<br>
<div><br></div></div></blockquote></div></div></div></div>
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