Questions about my new universe

[Skywalker_T-65]

I really need to stop with the topic making...two in one day today...on subject though, I need some help with my Sci-Fi universe. And SD.net is the best place to ask for said help. Considering I have rather bad writers block and this > is what I feel like. I have multiple questions but I figure I should start simple.

First off would be this...I'm not a physics major by any means, so I was wondering what would be the best/most efficient powerplant to use. I'm divided between three designs:

1: Matter/Anti-Matter drive (not ST style, to easy to blow up)
2: Nuclear Fusion
3: Nuclear Fission, upgraded with some special mineral Stargate style

The first two are the most realistic (relatively speaking), so that's where I am leaning. As for the third...the 'magic' mineral would increase the power of fission to the level of Fusion, however much that would be. Which do you all feel would be the best? And the second thing would be I'm divided on the drive system...mainly between ion engines and old reliable, aka Chemical Rockets. Nuclear engines would just be too risky. That's all I have for now. And for a little background on my universe:

The story will revolve around a naval officer in the Sol Confederacy, a group of 6 systems centered on Earth. Humans found a crashed starship in the Alps (to avoid ripping off Macross) and through a lot of work rebuilding it eventually got the thing spaceworthy again. The newly christened UERS Constellation was used to explore nearby systems, starting with Alpha Centuari. From there, Sol built more ships and colonized other nearby systems. And to anyone who has read my fanfics on here, you will recognize this as similar to Sol Hope, that is because I am using that story as a practice run. The main universe will be quite a bit different in the end. If anymore details are needed I'll be happy to oblige. Thanks for any help in advance.

[Sea Skimmer]

Fusion would cause the least problems. You can say it works, and that's it. No absurd special handling or net loss of energy like anti matter required, and it may not even involve any bullshit technology (we simply don't know on that bit). It sounds like the power plant has nothing to do with the story either, so all the more reason to take the simplest option which is functional fusion. Trying to explain special minerals seems pointless unless the story is about the strategic important of said minerals and this officer is out searching for them ect...

[Batman]

4. Whatever works. Is there any reason you'd need fusion/M/AM/magically enhanced fission for your story to work?

[GrandMasterTerwynn]

I really need to stop with the topic making...two in one day today...on subject though, I need some help with my Sci-Fi universe. And SD.net is the best place to ask for said help. Considering I have rather bad writers block and this > :banghead: is what I feel like. I have multiple questions but I figure I should start simple.

First off would be this...I'm not a physics major by any means, so I was wondering what would be the best/most efficient powerplant to use. I'm divided between three designs:

1: Matter/Anti-Matter drive (not ST style, to easy to blow up)
2: Nuclear Fusion
3: Nuclear Fission, upgraded with some special mineral Stargate style

Given that the premise sounds like
"1) 21st century humans find advanced alien wreck.
2) ???
3) Profit!"
Your best bet for plausibility would be fusion. Antimatter requires enormous production facilities and is very net-negative in terms of energy. Naquada your magic Stargate ripoff mineral fission idea would stretch your premise into camp. Unless camp is what you're going for. In which case, go with the magic fission.

[Stark]

What difference does it make?

Maybe he's thinking about how it impacts the world; the way energy is gathered, transported, traded and used, the infrastructure required, the way this stimulates or retards conflict, the violence of that conflict, etc. Actually, since it is Yet Another 'Hard Scifi' Worldbuilding Thread, maybe he has specific thematic requirements around endurance, existence or density of basing, or fog of war.

[Junghalli]

3: Nuclear Fission, upgraded with some special mineral Stargate style
As for the third...the 'magic' mineral would increase the power of fission to the level of Fusion, however much that would be.

I'm no engineer but I don't see any inherent reason a fusion reactor would be able to put out more watts than a fission reactor. I suspect practical output would likely be more a factor of engineering limitations like waste heat handling than the energy density of the fuel.

IIRC the reason fusion is considered desireable today is because it involves less radioactive waste and might be doable with easier to acquire fuels, not because it will produce more energy.

Unless the critical issue is exactly how much fuel you need to burn, in which case if you're using this to get 6X more energy out of 1 kg of uranium then you should be able to (going by this) then I submit this is less an enhanced fission reactor than a magical reactor that uses fission as a catalyst, and from a conservation of detail perspective it might be more straightforward to just cut out the fission part and make it a completely handwavium power source.

[Skywalker_T-65]

Wow, that was more replies than I was expecting. Let's answer the relevant ones...

Fusion would cause the least problems. You can say it works, and that's it. No absurd special handling or net loss of energy like anti matter required, and it may not even involve any bullshit technology (we simply don't know on that bit). It sounds like the power plant has nothing to do with the story either, so all the more reason to take the simplest option which is functional fusion. Trying to explain special minerals seems pointless unless the story is about the strategic important of said minerals and this officer is out searching for them ect...

Hmm...good point. The 'Stargate ripoff' mineral was just a random idea. Like I said, I was leaning towards fusion or M/AM anyway. I can see why fusion would cause the least problems here, since it is safer. I just didn't know which gave more power/efficiency.

4. Whatever works. Is there any reason you'd need fusion/M/AM/magically enhanced fission for your story to work?

Good point. There isn't any real reason that I need a particular one, I was just wondering which one would work best. Which is looking like Fusion.

Given that the premise sounds like
"1) 21st century humans find advanced alien wreck.
2) ???
3) Profit!"
Your best bet for plausibility would be fusion. Antimatter requires enormous production facilities and is very net-negative in terms of energy. Naquada your magic Stargate ripoff mineral fission idea would stretch your premise into camp. Unless camp is what you're going for. In which case, go with the magic fission.

Heh, funny. On a serious note, I did say it would be a Naquada like mineral. I am leaning more and more towards fusion now though, and no I am not going for camp. It's not extremely hard sci-fi, but it isn't particularly soft either. I'm not as in the know about these things as I would like, so I didn't know if M/AM would work better than fusion.

What difference does it make?

Maybe he's thinking about how it impacts the world; the way energy is gathered, transported, traded and used, the infrastructure required, the way this stimulates or retards conflict, the violence of that conflict, etc. Actually, since it is Yet Another 'Hard Scifi' Worldbuilding Thread, maybe he has specific thematic requirements around endurance, existence or density of basing, or fog of war.

While I wasn't planing on making it a huge plot point (like I said in the earlier reply), Stark did hit the nail on the head here. I am working on how it impacts the world. For example: If the Constellation ran off fusion power then you just solved our energy problems. Whereas if it ran on M/AM we have the problem of building AM production plants. And so on from there.

3: Nuclear Fission, upgraded with some special mineral Stargate style
As for the third...the 'magic' mineral would increase the power of fission to the level of Fusion, however much that would be.

I'm no engineer but I don't see any inherent reason a fusion reactor would be able to put out more watts than a fission reactor. I suspect practical output would likely be more a factor of engineering limitations like waste heat handling than the energy density of the fuel.

IIRC the reason fusion is considered desireable today is because it involves less radioactive waste and might be doable with easier to acquire fuels, not because it will produce more energy.

Unless the critical issue is exactly how much fuel you need to burn, in which case if you're using this to get 6X more energy out of 1 kg of uranium then you should be able to (going by this) then I submit this is less an enhanced fission reactor than a magical reactor that uses fission as a catalyst, and from a conservation of detail perspective it might be more straightforward to just cut out the fission part and make it a completely handwavium power source.

I don't know myself, but everything I have heard says that fusion is more efficient and gives out more power. Well I didn't want to just make up a new fuel source entirely (like hypermatter) since it presents certain problems. But again, I am leaning more towards fusion with each post. Actually, yeah, I think fusion works best here from all that I have seen. Even if it doesn't give off more power (like the last poster said) it still should be more efficient. Thanks for all the help, this has given me more things to think on. Now then, since we have that out of the way, what about the second question I asked, ion engines vs. chemical rockets?

I vaguely remember reading in one of the last world-buidling threads that electric engines (like ion engines) are less efficient and slower. But my memory may be faulty. As for the relevance in-universe...it is whichever one can produce more speed/power while still being more efficient. Any ideas?

[Junghalli]

I don't know myself, but everything I have heard says that fusion is more efficient and gives out more power.

Fusion does give more power per kilogram of fuel consumed (IIRC), but this is a seperate issue from how much energy the reactor can generate at any one time. We're talking about the difference between needing a smaller gas tank and having a more powerful engine; the former does not logically automatically imply the latter (although in practice you might be able to get more watts with fusion, I don't know).

Also, fission is still pretty energy-dense, unless you're talking about an application were you need enormous amounts of energy in a small package like a plausible physics self-propelled starship (that is to say one that needs to go at least at low fractions of c) I doubt the difference in fuel consumption between fusion and fission would be a big deal. Supplying electricity to a big city for a year you're looking at the difference between needing a few tons of fissionables or a few hundred kg of fusionables, assuming you can get all the theoretical potential energy out of the fuel.

I luv me some fission and/or solar power. I also luv me some chemical rockets.

They might have the value of relative novelty, it seems to me like pretty much every sci fi writer who isn't writing near future goes for fusion and fusion-powered nuclear rockets, if not more exotic stuff.

[Junghalli]

I luv me some fission and/or solar power. I also luv me some chemical rockets.

It might have the value of relative novelty, a lot of sci fi seems to treat fission and chemical rockets with disdain, as things that will certainly be hopelessly obsolete in The Future (TM).

Personally I could easily see those things having a role in a sci fi future. Chemical rockets are a gas-guzzling for big velocity changes like you need to get out of a big gravity well or fly around the solar system, but for stuff like getting around a habitat cluster in orbit of a planet or an asteroid belt they might be perfectly adequate. Given how much easier it seems to be to build a fission reactor than a fusion reactor I could easily see fission still being preferred for a lot of applications for economic or engineering reasons even if fusion is feasible.

Ack, double post. Well, I guess I'll leave this here because I expanded on what I said earlier.

[Skywalker_T-65]

Hmm...looking all of this over...I think I know what I will do now. Though I will reply in order again:

I don't know myself, but everything I have heard says that fusion is more efficient and gives out more power.

Fusion does give more power per kilogram of fuel consumed (IIRC), but this is a seperate issue from how much energy the reactor can generate at any one time. We're talking about the difference between needing a smaller gas tank and having a more powerful engine; the former does not logically automatically imply the latter (although in practice you might be able to get more watts with fusion, I don't know).

Also, fission is still pretty energy-dense, unless you're talking about an application were you need enormous amounts of energy in a small package like a plausible physics self-propelled starship (that is to say one that needs to go at least at low fractions of c) I doubt the difference in fuel consumption between fusion and fission would be a big deal. Supplying electricity to a big city for a year you're looking at the difference between needing a few tons of fissionables or a few hundred kg of fusionables, assuming you can get all the theoretical potential energy out of the fuel.

I luv me some fission and/or solar power. I also luv me some chemical rockets.

They might have the value of relative novelty, it seems to me like pretty much every sci fi writer who isn't writing near future goes for fusion and fusion-powered nuclear rockets, if not more exotic stuff.

That's what I thought. Hmm...good point there. I don't know if you can get more watts out of fusion either, hence why I was asking. These things will have FTL, so they don't need to go to fast in STL speeds.

Which means that it would work better for the smaller ships, but the larger ones would probably be better off with fission correct? I can agree with that, it seems like everything in The Future has to be exotic stuff. (the fusion vs. Fission size point)

It might have the value of relative novelty, a lot of sci fi seems to treat fission and chemical rockets with disdain, as things that will certainly be hopelessly obsolete in The Future (TM).

Personally I could easily see those things having a role in a sci fi future. Chemical rockets are a gas-guzzling for big velocity changes like you need to get out of a big gravity well or fly around the solar system, but for stuff like getting around a habitat cluster in orbit of a planet or an asteroid belt they might be perfectly adequate. Given how much easier it seems to be to build a fission reactor than a fusion reactor I could easily see fission still being preferred for a lot of applications for economic or engineering reasons even if fusion is feasible.

Well good thing I'm not a 'lot of sci-fi writers'. I personally think that even if we get the more advanced stuff the older things will still be in use. I can agree on that, chemical's may be gas-guzzling, but if you have someway to gather the abundant hydrogen and oxygen that is free-floating in space that problem goes away.

Junghalli wrote:
Chemical rockets are a gas-guzzling for big velocity changes like you need to get out of a big gravity well or fly around the solar system, but for stuff like getting around a habitat cluster in orbit of a planet or an asteroid belt they might be perfectly adequate.

Yes, indeed. They aren't even necessarily gas guzzlers - sometimes the acceleration they offer can help make up for the lower exhaust velocity, like when doing Oberth boost maneuvers.

They are also relatively simple which brings a host of nice things, including less power generation related hassle.

Moreover, getting you hands on kerosene or hydrogen and oxygen can be a lot easier than the xenon or whatever your ion drive uses. So, it can burn a lot of fuel, but that's ok because fuel is so cheap.


And, of course, habitat clusters rok so hard, and even chemical engines might be overkill in that environment!

Yeah, that is true, they do offer a lot of quick acceleration. But ion's can last longer (continual movement), which I suppose is useless in space where you keep moving until something stops you. And chem rockets are simpler, which means more reliable. Yeah, I said that earlier on in this post. With all the free floating chem fuel in space, it would be easier to replenish fuel. There will actually be habitat clusters in my story, so that random thing there helped.

Given how much easier it seems to be to build a fission reactor than a fusion reactor I could easily see fission still being preferred for a lot of applications for economic or engineering reasons even if fusion is feasible.

Aye. One thing I like to use against fusion is the minimum size and the mass penalty for shielding. You can scale a radioactive heat source way down to tinyness, same for solar. You can scale a fission reactor pretty far down.... but I'm not so sure about fusion. Time will tell.

A side note on this kind of thing though: trying to determine what tech WILL be there in the future is pretty futile and can mess up some of the fun imo.

If you say "I'm using fusion because my predictions of future history point in that direction", that can be ok in doses, but don't let that ruin what you have in mind.

Even if you want to do a scientifically plausible story, you shouldn't be deterred by worrying about if it will actually be used or not. Just pick something that fits your overall idea in your mind, and run with it.

Really run with it too: that's the real fun of hard sci fi. Not picking tech A or tech B. Just grab one, and see where it leads. You may be surprised!

I guess that is true. We just don't know enough about fusion to say for sure. But, that is the beauty of Sci-fi right there. I guess that is true, but I like to have my bases covered. Well of course, this won't be a tech manual after all (though I am making one...knowing my luck once I get this published (if all goes well) it will be debated on here, and I don't want to have to make people work stuff up). That is what I am doing now actually. I am obsessing about this somewhat...I will admit that. Now then, I've decided on something to do with this.

In the story, we can have both fusion/fission engines, along with chemical rockets (ions are just too much trouble). The relevance being that the main characters ship will be a new design using experimental fusion engines. But the rebels (one of the colonies will go rogue) will be using older fission powered ships. The MC (I'll just abbreviate that) ship will be a temperamental beast that can't use to much power through its engines without wrecking them, so that will show that fission is still the better choice. What do you think of that? Also I've worked up said ships design, but I'll put that in a second post...this one is long enough as is...

[Skywalker_T-65]

Double post FTW! On a serious note though, here is what I have worked up for the MC's ship.

A wedge design, not like an ISD though, more like a B2 in SPPAACCEE. Namely since without annoying superstructure in the way, if you turret the weapons (most likely large railguns) you could fire them all forward and all behind. And you could also get a fairly decent broadside here. And it isn’t literally a B2 in SPACE because that would be weird looking to say the least. It is the traditional flying wing design, but with more…meat…in the back. I guess you could go for very wide SD if you will. As for size…2 kilometers long, and 4 wide. I can get into more detail if it is needed to judge the design. What do you think of it so far? Like I said, I can go into more detail, but I don't want to make another super-long post unless it is needed.

[Sea Skimmer]

Hmm...good point. The 'Stargate ripoff' mineral was just a random idea. Like I said, I was leaning towards fusion or M/AM anyway. I can see why fusion would cause the least problems here, since it is safer. I just didn't know which gave more power/efficiency.

Its impossible to know right how much power you'd really get out of M/AM plant, but as I recall most energy release will be wasted in the form of neutrions out of hand, the power plant might end up no smaller the fusion or even much larger. However while the energy return on fusion may not be that high, since its going to take lots of energy to power the fusion system, you can find many kinds of fusion fuel in space, in rather large amounts in some instances given a certain level of processing. Earth's ocean for example is full of deuterium, so would other oceans, and the moon has a fair bit of helium-3 you could mine out of the soil. All anti matter has to be manufactured at a net loss of energy meaning you can't be making it on board. A big enough fusion starship might carry all the equipment needed to self refuel, though it might require stopping for some weeks or even months, and setting up static fuel collection plants as outposts would be straightforward.