For context, this takes place about 300 years in the future. The space city in question is located in a nebula, completely man-made (not build upon any preexisting foundations like an asteroid etc.), densely populated and continually expanding, and possesses a surrounding force-field in order to create a habitable environment within. It is isolated from the control of any sole government and is established as a hub for interplanetary diplomacy. Thus, it needs to be mostly or completely self sufficient, but does receive shipments of outside goods.

What I would like to know is:

  • would drawing and converting power from developing stars within the nebula be a feasible way to power the city

  • are there any dangers presented by this location either to the city or the ships traveling back and forth

  • what steps could be taken to minimize or protect against such dangers

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    $\begingroup$ Wouldn't this just be solar power? $\endgroup$ – Willk Apr 30 '19 at 20:21
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    $\begingroup$ Some clarification would help:the Latin "nebula" is much like the English word "cloud" - of...what? smoke? water vapor? - you get the idea. Interstellar nebulae are of similar diversity, See here: novacelestia.com/space_art_stars/nebulae.html Many of your energy requirements and habitability specifications will depend on this type. Given that some nebulae are actually 'shells' from stellar explosions, hazards are very possible. $\endgroup$ – Joe Apr 30 '19 at 20:43
  • $\begingroup$ It would be great so long as no one ever lights a fire XD! $\endgroup$ – Rob Apr 30 '19 at 20:46

The densest nebulae are not much dense. They usually have up to 105 particles per cm3. For comparison, air is like 1019 particles for the same volume. Mars's own atmosphere is around 1017 range, I believe (1~2% of Earth atmosphere pressure when at the same temperature, mostly CO2).

If you were naked inside a nebula, you would be as good as exposed to hard vacuum.

You would have problems for objects going interstellar, which will have more wear damage than if they were going through space. 1 light year of nebula travel would be equivalent to many thousands of years of hard vacuum travel.

For energy harvest, if you are going to build dyson spehres around stars in a nebula, that wouldn't be different from stars outside nebulas. The stars' solar wind would push much of the nebula material away anyway. You will have a drop in efficiency if you beam up energy among stars, but if you have the technology to do that, you've probably reached a point where you can also make vacuum tunnels inside the nebula, which would remove the problem with ship wear damage too.

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  • $\begingroup$ I suspect that radiation pressure alone might be enough to create said vacuum tunnels $\endgroup$ – John Dvorak May 2 '19 at 14:47
  • $\begingroup$ I don't think we'll be building dyson spheres in 300 years :/ $\endgroup$ – Innovine May 2 '19 at 15:07
  • $\begingroup$ @Innovine OP mentions a force field around a nebula, which is a structure much larger than the solar system. If you can build that, a Dyson sphere is child's play. $\endgroup$ – Renan May 2 '19 at 15:26
  • $\begingroup$ @Renan I think OP means that the city is surrounded by the forcefield, not the entire nebula $\endgroup$ – Innovine May 2 '19 at 20:35

Well, there are three different kinds of Nebulae: classical, Diffuse, and Planetary.

Nebulae themselves are made of different types of ionized gases and such. Dense places eventually form stars and some scientists believe the rest of the universal goop is used to build planets.

Also how Nebulae form is important. They can be created from an interstellar medium, stars, and supernova explosions.

Classical types include things such as dark nebulae and supernova remnant.

Diffuse Nebulae give off some radiation and moderate visible light.

Planetary Nebulae are stars that die and create a Nebulae, leaving a white Nebulae in the center (the original core star). Scientists say that when the sun dies it will create this.

The possibility of nuclear and radiation energy could be harnessed. The problem is in high amounts those things are usually deadly to most life in vast quantities. That would be an optimum power source but the world would either have to be outfitted to withstand nuclear radiation and other radiation (people, plants, and all). SO either they have been built to survive this or avoid all exposure with the outdoors (i.e wear thick clothing, live underground, live in buildings with thick walls).



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