Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site sequent.UUCP Path: utzoo!watmath!clyde!burl!ulysses!harpo!seismo!hao!hplabs!tektronix!ogcvax!verdix!sequent!merlyn From: merlyn@sequent.UUCP Newsgroups: net.physics Subject: Re: Dean Drive Possible? Message-ID: <505@sequent.UUCP> Date: Wed, 16-May-84 13:12:57 EDT Article-I.D.: sequent.505 Posted: Wed May 16 13:12:57 1984 Date-Received: Mon, 21-May-84 05:27:29 EDT References: <715@sri-arpa.UUCP> Organization: Sequent Computer Systems, Portland Lines: 42 > Message-ID: <715@sri-arpa.UUCP> > Date: Mon, 14-May-84 02:41:38 PDT > From: Doug Gwyn (VLD/VMB) > > No, what I had in mind was more like this: > A space-suited person in outer space holds two massive dumbbells. > He takes turns holding them asymmetrically at different distances > and waving them around. After a while the dumbbells are in their > original positions w.r.t. the person but he is now facing some > direction different from the one he started out facing. > I am not sure that this scenario is actualizable; it was told to me > during a discussion of the Dean Drive and freely-falling cats. Supposedly > someone determined that it was possible for a cat to reorient itself > without reacting against the air. > > I would be skeptical except that I haven't been able to come up with a > quick counter-proof (the problem is that the inertia tensor is not constant). How about this... (no dumbells even!)... In space, start your hands at your side. Then, make a large circle forward, up, over your head, backward, down, and back to your sides. If you end up in the same orientation after you complete the circle, you have some pretty strange hands or strange ideas about what happens in space. Really, wouldn't a large massive wheel with a center of rotation aligned with the center of mass of a spaceship affect the rotational acceleration of the ship based on the rotational acceleration of the wheel? Sounds pretty straightforward to me. So, suppose the rotational velocity of the ship is zero, as well as the rotational velocity of the wheel. Then, rotate the wheel one turn (ship relative). The ship will be facing a different direction (rotational position), and still have zero kinetic rotational energy, as will the wheel. I'm not a physics expert, but I do know that it is possible to spin yourself around in space. (Not change linear momentum, however... unless the Dean Drive works.) -- A particularly personal and original observation from the thought-stream of Randal L. ("(null)") Schwartz, esq. (merlyn@sequent.UUCP) (Official Legendary Sorcerer of the 1984 Summer Olympics) Sequent Computer Systems, Inc. (503)626-5700 (sequent = 1/quosine) UUCP: {decwrl,ogcvax,pur-ee,rocks34,shell,unisoft,vax135,verdix}!sequent!merlyn