starfurry alignment puzzle

From: throopw%sheol.uucp@dg-rtp.dg.com (Wayne Throop)
Newsgroups: rec.arts.sf.tv.babylon5
Subject: Re: Star Fury lauches (and Re: The novel "Voices")

: From: gharlane@ccshp1.ccs.csus.edu (Gharlane of Eddore)
: [...] the 'Fury is initially travelling at right angles to its "forward"
: orientation; but since it's still rotating at (effectively) the same
: speed as the station, its nose will slew around to match the direction
: of its course within 10-15 seconds. 
An interesting puzzle occurs to me [1]. Gharlane points out that, considering things from the viewpoint of the non-rotating frame at rest WRT the station, the starfurry's cute little nose will face its "direction of travel" in a quarter-revolution of the station.

But let's adopt (what I claim is [2] ) a more interesting frame of reference: the FOR in which the launch bay is stationary and nonrotating. Then, centrifugal force pushes the starfurry "down" out of the bay, and as it moves, coriolis force pushes it antispinward, bending its trajectory. Note that in this FOR, the starfurry isn't rotating towards an alignment with a straight trajectory, but rather, its trajectory is bending to match a constant orientation.

So the puzzle is, which happens first, the rotating starfurry of Gharlane's faces parallel with its trajectory, or the non-rotating starfurry of mine faces parallel with *its* trajectory. And of course, which of the two possible directions is mine facing then? Answers below [3].


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Last edited Mon Jun 12 15:41:39 1995 - Last generated Mon Jun 12 15:41:44 1995
[1]
OK, so it's a hopelessly geeky puzzle. It interested me. So, I'm a hopeless geek, OK. Are you proud, now that you've made me cry? Sob.
[2]
I pointed out before that the non-rotating frame is not, IMHO, a very good perspective. After all, in walking out of the south-facing front door of my house, I don't adopt the non-rotating frame at rest WRT the earth, and notice, gee, I'm actually moving leftward at 1500ish kph, rather than southward at 1 or so.
[3]
Answer to puzzle. (Well, my current guess as to the right answer anyhows) starfurry-align.gif

First, I'm ignoring the trivial solution that the starfurry is aligned along its trajectory at launch. Giving that as a solution would (IMHO) render it a trivial "trick" question.

Gharlane's F.O.R. gets the alignment first, at a quarter-revolution. The rotating F.O.R. gets its alignment after a half-revolution. Reasoning from the simpler F.O.R, (that is, Gharlane's) we know that the alignment hasn't happened yet at a half-revolution (because the SF points due "south", but the relative velocity points east, and the pseudovelocity because of the movement of the launch bay tangent points due south; the sum can't point on the north-south line yet).


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Last edited Mon Jun 12 15:41:39 1995 - Last generated Mon Jun 12 15:41:44 1995