[Runequest] Fact check

Peter Maranci pmaranci at gmail.com
Wed Mar 27 08:51:20 EST 2013


Excellent points, Asher!

My problem is that the player is making a full-court press to convince me
that he should be able to do this. But it doesn't seem feasible.

The Ringworld's rotation is 770 miles per second. He'd share that speed
when he jumped...but presumably, he'd slow down in relation to to the
ground. My physics were never good enough to calculate the effects of air
friction and such. But in any case, since we know that the chutes were
rates for approximately 400 pounds, and he's definitely much heavier than
that, I foresee shredding and troll-bombs.

If he has a much larger parachute made, though...I can't help but wonder
how long a 500-mile parachute jump would take. And what would it be like?


On Tue, Mar 26, 2013 at 5:32 PM, Asher Royce Yaffee
<ashersensei at gmail.com>wrote:

> Hi, All,
>    One thing to remember about a ringworld or spinning space station or
> other such structure that gets "gravity" by rotation.  When you drop an
> object inside the environment -- ring, station, what have you -- the object
> does not continuously accelerate.  Ringworld's "gravity" is just about the
> same as Earth's, in that we would be the same weight on Ringworld as we
> would be on Earth.  But that is where the similarity ends.
>    Let's say I paint a big X on the sidewalk, go up the elevator, and then
> jump off a tall building in order to land on the X.
>    On Earth, if I jump off a tall building, I would accelerate
> continuously until either hitting the ground or hitting terminal velocity
> (due to air resistance).  After one second, I would be falling at about 32
> feet/second, or 9.8 meters/second.  After 2 seconds, double my speed.
>  After 3 seconds, triple my speed.  Etc.  The sidewalk below me would
> approach faster and faster.  Barring strong wind, I can reasonably hope to
> land on or near the X I painted.
>    On the Ringworld, if I jump off a tall building, I fall at about 32
> feet/second or 9.8 meters/second -- and that's it.  There is no further
> acceleration due to gravity.  So I watch the sidewalk below approach at a
> more leisurely pace.
>    But there's more.  During my fall, I would observe the X slide out from
> under me.  It would slide to spinward.  Very much like the case of long
> ranged artillery, where the artillery crew have to compensate for the Earth
> rotating underneath an artillery shell in its flight.
>    For any normal jump -- out of trees onto foes, etc. -- on Ringworld,
> the drift would be too small to notice.  But from 500 miles or 800 km up,
> it would matter.  I would have to relearn how to do the math to figure out
> how much the rotational velocity difference would be between the Ringworld
> floor and the Ringworld rim to say how much it would matter.  Let's assume
> that the troll has a strong enough parachute.  On the way down, the troll
> would find that his landing zone is sliding away from him to spinward --
> maybe by 60 mph.  Makes hitting a tree a whole lot more painful, too.
>    Sincerely,
> Asher
>
>
>
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-- 
Peter Maranci - pmaranci at gmail.com
Pete's RuneQuest & Roleplaying! http://www.runequest.org/rq.htm
The Diary of A Simple Man: http://bobquasit.livejournal.com/
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