Talk:Nuclear photonic rocket

message: Too bad Sanger wasn't around for the invention of lasers. See my discussion of the relativistic rocket problem. 
http://en.wikipedia.org/wiki/Talk:Relativistic_rocket
(Onerock 23:40, 26 Aug 2004 (UTC)
replies: text: Unfortunately, light is made up of waves and obeys the law of diffraction.  To focus light beams over interplanetary distances requires apertures of hundreds of kilometers in diameter. DonPMitchell (talk) 00:27, 5 July 2008 (UTC)
thread_title: Laser technology

message: I've just substantially rewritten this article, and I'm left with a number of questions we should try to address:
* Why is a hotter temperature better?  Certainly the blackbody radiation flux density goes up as something like the 4th power of temperature, but is this important?  10W of infrared photons carries the same momentum as 10W of ultraviolet, so making things hotter seems to just make things harder to deal with. (probable answer (not clear from article): Higher temperatures produce more photons because the greater difference in temp between the emitter and the background means more photons travelling outwards - radiative cooling goes up as the 4th power.) (121.222.165.152 (talk) 09:52, 12 August 2008 (UTC)
thread_title:  Some questions 

message: The article says that a 100 ton space ship using 3 Mw of laser power for propulsion would achieve speeds of over 500 km/s over 20 years.  However, when I tried to calculate the speed that the vehicle would reach, the result I came up with was that even 100% efficient lasers would only achieve a pitiful 126 m/s.  I may have made a mistake, but I think that the article is wrong.
The setup mentiond in the article seems like a pretty foolish way to build a rocket.  Why use millions of very small lasers instead of a few big ones?  And why use lasers at all when nuclear light bulbs can produce a much higher specific power and ion engines can convert electric power into thrust much more efficiently?--Todd Kloos 06:21, 15 August 2006 (UTC)
replies: text: I get the same result.  Accordingly, I have deleted the section, which really had very little of value after that. Evand 04:15, 17 August 2006 (UTC)

text: I had been just about to fix that error. The information was based upon a old article I had on my computer, and I only recently tried to check the maths myself. I posted it because it is a way such rockets can be built, and 'laser rockets' are often cited in science fiction. Even the most optomistic fission-photonic design I could come up with can only achieve 50kmps. Given the number of articles on nuclear propulsion, would an article highlighting the fundimental limits of such technology be useful? The Rocket page contains much information in this reguard. Even if you assume advanced technology or new physics technology (Nuclear magic rocket?) the very limits of the fuel itself stop you from building the kinds of engines you get in space opera. Upshot of the article being if you make you engine too powerful you'll irradiate your crew, melt your engine or make it a mile across, and could use your fuel up very quickly. Given the lack of direct information about nuclear fuels, I'm not sure this point is made sufficiently clear. ANTIcarrot 12:43, 18 August 2006 (UTC)
thread_title:  Fission Laser Rocket