Talk:Space Transport and Engineering Methods/Energy

I've been (intermittently) making my way through the text from the beginning, but only found something to comment on now.

In the introductory Energy section, Beam Sources has no summary text. I'm reasonably confident I know this is about shooting or bouncing photons/particles towards a reciever, but this isn't outlined in the text. Further the subsection Sunlight states that sunlight is highly directional, which is confusing because the Sun is a sphere and emits light in all directions. What is probably missing is the subject of a mirror being used to redirect the light in a certain direction, otherwise it seems I'm still confused.


 * You are correct that section was (a) pretty bare of text, and (b) not very clear. I added words to clarify sunlight is directional relative to a device (ie locally).  It indeed emits light in all directions into space, but on the scale of most devices we might build, the rays are near parallel.

Concentrated Light : "In the case of the Sun, the limit is 5,775K less reflection losses and radiation from the object you are heating."

Why is this? Is that related to the temperature of the surface of the sun? It's not really clear from the context and I think it'd be nice to have a brief explanation about that: "In the case of the Sun, the limit is 5,775K (temperature at the surface of the sun), less reflection losses and radiation from the object you are heating." --NortySpock (discuss • contribs) 01:44, 22 November 2012 (UTC)


 * Yes, the limit is the effective temperature of the light source, which for the Sun is a black body at 5,775K. The second law of thermodynamics states that heat can only flow from a hotter object to a colder one.  No system of mirrors or dishes can violate that rule.  If you managed to heat an object to the Sun's temperature (it would be a plasma by that point), it would be radiating energy away as fast as you could put it in, via the same mirrors or dishes.  I added a few words to clarify this section, but the page as a whole (along with other parts of the book) can use more work.  Danielravennest (discuss • contribs) 02:57, 22 November 2012 (UTC)

In Nuclear Sources maybe put a mention of hybrid reactors that use fission to catalyze fusion? Lsparrish (discuss • contribs) 19:03, 10 February 2015 (UTC)