Talk:Beam-powered propulsion

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The problem of diffraction and keeping the beam tight over large distances should be quantified. I believe it is something like: BeamDiameter = Wavelength * Range / EmittingAperture. For typical optical frequencies, I think you will find something like 75 kilometer beam diameter divided by meters of aperture, at a distance of 1 AU. For distances on the order of 1 AU, interplanetary distances, this implies a laser with an aperture on the order of kilometers. Someone check my math, please. DonPMitchell 23:04, 15 November 2007 (UTC)

In the "Direct impulse" section: "His work elaborating on a proposal initially made by Marx." This looks to me like random chaff. I can't find anything backing up a connection to any Marx, but I don't know much about propulsion. Is there anyone who can confirm or deny this line? Avram (talk) 15:22, 23 February 2008 (UTC)

Under "Thermal Propulsion":

The page states that using a laser would give a more efficient method of propelling the ship. It then says this is due to the velocity being proportional to the square root of the temperature. But surely if its an effective proportionality then the velocity should be proportional to the temperature squared. if it was the square root of the temperature then a very high temperature would be needed in comparison to the velocity gained. just a thought. Also I'm doing my A level physics research coursework on the topic of beam powered propulsion so if anyone has any more information let me know. cheers Haydnrobinson (talk) 11:52, 3 April 2008 (UTC)