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*To*: Starship design group <starship-design@lists.uoregon.edu>*Subject*: Re: starship-design: the beamed power problem, again*From*: "Kevin \"Tex\" Houston" <hous0042@maroon.tc.umn.edu>*Date*: Wed, 04 Sep 1996 20:59:24 -0500*Organization*: Sadly lacking*References*: <v01530500ae5376b78cc1@[151.168.146.187]>*Reply-To*: "Kevin \"Tex\" Houston" <hous0042@maroon.tc.umn.edu>*Sender*: owner-starship-design

Kelly Starks x7066 MS 10-39 wrote: > > At 10:52 AM 9/4/96, Steve VanDevender wrote: > >Rex (DotarSojat@aol.com) and I have been having a private discussion on > >my assertion that if you are beaming power to a starship to give it a > >fixed ship-frame acceleration, you have only a finite amount of time > >during which you can send power to the ship, no matter how long the > >ship's trip time is. For example, if you are beaming power to > >accelerate a ship at 1 g, you have just short of a year after its > >departure to beam power to it, no matter how far away you are sending > >it, and you must beam increasing amounts of power towards the end of > >that time to sustain the 1 g ship-frame acceleration. > I found another way to note the same thing. A constant 1 G thrust profile mission, takes about 5years ship time and 13.25 years earth time, to go 11.9 light-years. so on the last day, as your ship coasts into target system, the light (microwaves) you are seeing left earth 11.9 years ago, and 13.25 years after the start of the mission. Thus that light must have been emmitted ~1.35 years after the start of the mission (from Earth's perspective) > I beleave the english translation of the following; is that after about a > year of 1G acceleration, the ships moving at near light speed. Since the > microwaves are moving at exactly lightspeed. At some point the beam can't > really catch up with the ship in time to be usefull. > But at turn-around the ship is only moving at a speed of .9905 C. This is because 11.9 light-years is too short a distance to get into the _really_ strange parts of the trip. The gamma for this is "only" 7.27 This is not really all that bad. The microwave wavelength will only shrink or stretch (depending on your direction) by this amount. Same with the the power drop, and the time dialation factor. How about a mission which has a constant beam power, the acceleration would drop off toward the turnaround point. In this case, the crew would start off with earth-like gravity, and towards the middle of the trip, the gravity would be more lunar-like. ( a little less actually, but not for long) The advantage would be simplified beaming requirements, and the disadvantage would be a slightly longer flight time. Questions: What would the top speed relative to Earth be? What is the total trip time. (crew time?) how much of this time is spent at less than 1/2 G? Kevin > Kelly > -- Kevin "Tex" Houston http://umn.edu/~hous0042/index.html

**References**:**Re: starship-design: the beamed power problem, again***From:*kgstar@most.fw.hac.com (Kelly Starks x7066 MS 10-39)

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