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*To*: starship-design@lists.uoregon.edu*Subject*: starship-design: Following the beam*From*: T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)*Date*: Tue, 29 Oct 1996 11:58:02 +0100*Reply-To*: T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)*Sender*: owner-starship-design

Zenon replied: >> The beaming station makes a "focussed" (as far as interference allows) >> and beams it straight forward (in the direction of Tau Ceti). >> In this case not the velocity of the orbiting station is important, >> but it's acceleration (to the center of gravity), which is rather low. >> Low enough for the starship to compensate and change its direction. >> >That is, the ship must go along the helical curve with the >radius equal the radius of the beaming station orbit >(assuming the plane of the orbit is perpendicular >to the direction to Tau Ceti), or along a sinusoid >with amplitude equal to the diameter of the orbit >(assuming the direction to Tau Ceti lies within the plane >of the orbit). I would prefer a plane of orbit that is perpendicular to the direction of TC since we would not have any moments that the Sun is in the view. >Can somebody calculate what lateral thrust (and acceleration, >amounting to a centrifugal force for the crew) >will be needed for such a trajectory ? a=4 pi^2 r/T^2 (a=v^2/r v=2*pi*r/T) Where a = Acceleration in m/s^2 r = The radius of the helix in meters T = Time to make a complete orbit in seconds So say we have a beaming station on Earth: a = 4 * pi^2 * 1.5E11/(3.2E7)^2 = 6.1E-3 m/s^2 Or for the moon around the Earth: a = 4 * pi^2 * 3.84E8/(2.3E6)^2 = 2.9E-3 m/s^2 >However, I wonder if the jiggle of the direction of the beam >due to "directional noise" can be compensated in this way >(may I recall: a tilt of the 100km diameter beaming antenna >by 1/25th of an inch at the edge (i.e., a 1/100 000 000 directional error) >gives a sweep of 100 000 km at 1 ly distance). The only ways to avoid jiggling are to increase the sail/receiver or to make the sender more stable. About the stability of the laser, is a 1 millimeter jiggle not a little bit large? In fact, if we have jiggles of that size, we have to use microwaves. !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Before we go further discussing apertures/jiggles, we should first determine what resonable limits for wavelenghts will be, when we use phased arrays. Timothy

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