The difficulty with Hard Sci-fi

I'm not sure how quantum mechanics would help. It might describe what happens on a quantum level, but I don't see how it could be used to make more efficient lenses. Because of the wave-particle duality of light it would be impossible to direct a photon accurately.

 

As a great lover of hard sci-fi—but a complete numpty as to the physics required to get from planet A to planet B—my first question was ...is there a way to store the solar power? Think "graphene" or something like that. In other words, a way to store the solar energy (which could be gathered before the start of the voyage) in hyper-efficient batteries, that would last a long long long time without being recharged.

I think your problem of decelleration could be solved, if you were including an 'engine' of sorts that is powered by battery. (Reverse thrusters?) Ditto any problems with a planet in the way, etc. Surely somebody will be steering this craft, or artificial intelligence will be steering the craft? Surely there will be a WAY to steer the craft, and it's not just a huge bullet. If a planet or large body appears on the 'radar', surely the craft could be programmed to veer away from it, then return to its course?

If there was a similar sun to ours waiting at the end of the journey, this might be known beforehand? In fact, it's the reason this planet was chosen as a destination in the first place?

I do agree with others that the story needs human beings with their perspective on all this to make a story—that the mere fact your spacecraft is going someplace is merely the vehicle for your story, not the reason for it. However, I don't actually mind if all the scientific mumbo-jumbo gets included—as long as it is presented in words of one syllable, so dingbats like myself can walk away feeling smarter at the end of the story!

I would compare this issue to a story about a road trip here on earth. I can read about a cross-country auto trip, and all the things that happen along the way to the people who are travelling, without knowing the history and mechanics of auto design, the roadbuilding process, the science of fuel and its components, etc. All I need is a believable 'car' and possibly enough knowledge about how it works to put gas into it at intervals, check the water and the oil, clean the windscreen, etc. If a situation comes up that requires more knowledge, at least it's there ...but I don't have to write about it.

 

The problem is that the huge amounts of fuel required (whether batteries, rocket fuel, nuclear ramjet etc) would make it impossible to carry the fuel source with you on the ship. It becomes an ever escalating problem in that the more fuel you carry, the more mass you have to accelerate, to overcome which the more fuel you have to carry and so on. It is just impossible. Even if matter/ anti-matter weren't practically impossible (and probably theoretically impossible), you could still never have fuel tanks large enough (or an engine that could contain the reaction).

The idea of a beam craft means that there is no requirement to carry fuel with you, a laser in orbit around the sun simply hits a huge sail on the craft, which accelerates through radiation pressure.

There would be no way to alter the trajectory of the craft, if there is a planet or asteroid or even a gaseous cloud in its path then everyone dies.

 

People would have thought—say, 60 years ago—that it would be impossible to store entire bodies of knowledge, the text of hundreds of novels, movies, the ability to communicate with one another, etc, inside something as tiny as a microchip. Compare the size and capacity of the first computers—the ones that took an entire building to be contained—to what we now routinely hold in the palms of our hands and shove into our pockets or backpacks.

Maybe our thinking about battery size and capacity could change dramatically as well. The thing is ...IF you could come up with power storage that was small, easily carried and lasted a huge amount of time, your problem would be solved, wouldn't it? That might be the key.

I was reading about graphene a while ago, and the incredible untapped potential for power storage that it seems to hold ...and its cheapness to produce ...and that got me thinking.

The main problem will probably be the amount of time the voyage would take, and what the toll would be on the humans inside the ship. Century ships...that's been done before, but until FTL travel is 'invented,' this seems to be the most unsolvable of the problems presented by space travel.

 

But if a car did not exist, you would have to create a realistic and consistent premise for one before you could write about it in a convincing manner. Otherwise you might have it jumping fences and the character's stopping to scoop up shit behind the thing.

I dunno, Moore's law was stated 50 odd years ago (in fact it initially predicted faster development than transpired). Everything we can do now was well within the realms of possibility then.

The main issue is that this needs to occur within a relatively short time period, so must employ a constant acceleration profile, so must employ immense power. FTL won't be invented: wormholes and warp drives are impossible.

 

Just sayin'....

As to my statement about 50 years ago, I was thinking more in terms of what we, the ordinary population, thought at the time. There might well have been scientists who were working on the problem somewhere in the background of our lives fifty years ago. However, I'll amend my statement. One hundred years ago, did scientists know how to condense, store and access information in a tiny microchip? Did anybody realistically think that was possible? Or if they did think this, a hundred years ago, then go back to when they didn't. I'm not interested in pinpointing exactly when microchips were first thought of, but to recognise that there was a time when they did not exist at all, not even in the heads of scientists.

It's your way of thinking about the problem that I'm addressing in my comment. Don't be afraid to think outside the box. I think you are trying to apply what we know right now (fuel is too bulky and heavy to carry on a ship) to what might happen far in the future. If large containers of fuel is your main problem, maybe that's what you should be looking at fixing, in terms of your story.

As for the car analogy, I only meant that in terms of your storytelling, you don't need to tell us all about the workings of the car. Obviously you'll need to know this stuff can work, and as the inventor of the device, you'll need to know how it works. I was only trying to illustrate that how the device works will not be the point of your story. I hope.

 

I am not arguing for the sake of arguing I promise.

Here is an example:
You could say that a phone would appear like magic to someone 500 years ago.
You could also say that FTL travel would appear like magic to someone now.

The difference simply is that a phone does not break any physical laws (it might have broken some unproven premise of the time, which would later be shown to be false.)

Where as FTL does break the experimentally proven special theory of relativity.

 

Oh, I couldn't agree more about FTL. Which means the voyage length would be the most insurmountable story problem. However, creating a battery—charged by our sun or some other sun—that was smaller than we envision today, yet contained huge capacity? I think that's within the realm of possiblity, if you use the microchip as a point of departure in your vision of how this could work.

 

Ok, given that this battery is charged by the sun, why not just have a nuclear fusion reactor on the ship? It would be an incredibly efficient source of energy, but the difficulty is the same one you have with batteries (with the advantage that the reactor would be more efficient). How do you turn that energy into thrust giving an adequate rate of acceleration? I mean batteries aren't going to be able to eject hot gases, or cause a series of nuclear scale explosions as per an orion drive.

I suppose you could drop them off en route to fire lasers at a solar sail, but then they only perform the same function as lenses. And given that the acceleration and deceleration phases of the journey are a tiny fraction of it, and occur relatively close to each of the suns I just can't get my head around what batteries are bringing to the table.

 

Okay, this is where I bow out. I have no idea how this would work. I just was suggesting that perhaps there are more ways than one to look at the problem. Or, rather, to identify the problem in a different way. I'm a big fan of 'what-iffing' as a method of problem solving. Looking for that leap that takes a person away from accepted, accumulated beliefs into seeing things in a new way, from a new perspective entirely. I love 'eureka' moments when it all comes together in an unexpected way.

 

To pick up this torch...

How big would a battery need to be to absorb solar power, whilst near to a sun, sufficient to provide thrust enough to get you through the interstellar void? Bloody big.
Why not build such a battery in Earth orbit, and make it ship-shaped and with living quarters inside?

 

Ha ha ...I like your thinking. Make it entirely out of graphene!

 

Hi guys, let me join

The most effective fuel we know today is anti-matter. When mixed with normal matter they annihilate each other and their entire combined mass is converted to pure energy and radiated away via electromagnetic radiation ( E=m*c^2 ). It is really hard to think of anything more efficient than this.

The main problem is that to accelerate the ship to a speed comparable with the speed of light ( 0.6c as mentioned ) you also need unbelievably high amount of energy :
E=1/2*m*(0.6c)^2 = 0.5*m*0.36*c^2 = 0.18*m*c^2

This is a simplified calculation as for very high speeds the motion energy is calculated with relativistic equitations). If all energy from the matter - anti-matter annihilation is converted to motion energy then 18% of the total mass needs to be fuel for acceleration and 18% of the remaining 82% (0.18*0.82=0.1476 so about 15% of the original mass) needs to be fuel to decelerate so in total 18+15 = 33% of the starting mass of the ship needs to be fuel (the correct amount is higher, but most probably less than 100% )

To reply to the OP : why using lens? Aren't they in the way when the ship arrives? If the ship accidentally hits one of the lens with let's say 0.3c the resulting firework will be really imposing and the generated heat tears up the atoms and leave only free flying nucleus-es and electrons in an inflating sphere.
A few hundred years from now humanity should be able to create a laser beam that is so focused that it's diameter does not change too much with distance. Let's say it's diameter doubles after each lightyear and on Earth the base crew slowly pushes up the power to balance out this effect and provide a stable thrust to the ship.

 

The problem with anti-matter are several (and I am sure you know them); firstly the production of sufficient quantities is not going to be a near technology by any stretch of the imagination. Secondly the containment of the fuel is what will add vast weight, the cooling and magnetic fields. The propulsion will cause immense heat which is likely to result in an unstoppable chain reaction that will destroy the ship, and emit gamma rays which will probably destroy the earth as well. It just isn't realistic any time in the near future, if ever.

I quote the following from Frank Close's Antimatter on production: -

To make a gram of antiprotons you will need 6 x 1023 of them, while a gram of positrons would require 1026. The most intense source of antiprotons is at Fermilab, USA. Their record production over a month in June 2007 produced 1014antiprotons. Were they able to do this every month for a year they could produce about 1015, which equates to 1.5 billionths of a gram, or nanograms. Were we able to retain all of these antiprotons and annihilate them with 1.5 nanograms of matter, the total energy released would be about 270 Joules, which is like five seconds illumination by a feeble light bulb.

A laser with a diameter that only doubles with each light year? Really? This would require the same hand-waving as the use of lenses.

 

You can collapse the wave=particle duality by having the protons interfere with the environment. It will collapse it until it has another interaction with the environment again. That's how the dual slit experiment works. So in deep space you don't have to worry about something un-collapsing the wave, giving more direction to the light, and stopping it from falling out the edges of your laser beam.

 

There are theories of FTL travel that don't conflict with special relativity as we currently understand it.

How far you want to extrapolate, and the extent to which you want to hand-wave, is determined by just how "hard" you want the SF to be. There are sub-categories within hard SF that are broken down in chart reproduced by John C. Wright, here: http://www.scifiwright.com/2014/12/diamond-hard-sf-to-mushy-soft-sf/

 

Quantum mechanics is not an area I am particularly strong on. But the wave function persists until the photon is observed interacting with its environment. This does not permanently collapse the wave function. In the double slit experiment the wave function occurs until such time as the photon is observed hitting the rear sheet of paper, if the photon is reflected the wave function then resumes. I don't even understand your last sentence. The only thing that will collapse the wave function would be the observation of a photon hitting the solar sail (or another object).

 

I think this is true, and it's not enough to say that certain parts of a theory have been experimentally verified and therefore no future technology could conflict with our current understanding. Our understanding is incomplete, and there are aspects of the theory that have never been empirically tested, including taking an object like a spaceship and accelerating it to near-light or FTL speeds.

By analogy, think of the Central Dogma of molecular biology from a few decades past, which posited that genetic information could only flow in one direction. The theory was in place, and so well-accepted that it was labeled a "dogma." It was empirically verified, because people were able to experimentally show that the information flowed in the accepted direction. What they didn't know at the time was that our understanding was incomplete, and information does in fact flow the other way. If you had written a SF story when the central dogma was accepted as the whole story, and had information flowing the other way, I suppose people might have said it wasn't "hard" SF and that you'd thrown impossible elements into the story, but a decade or two later would it suddenly become hard SF when it was shown to be possible?

 

I agree, but we have accelerated particles to near light speed and we know that their mass exponentially increases. Saying that we can't be sure this would occur with a space ship because we haven't tested it on a spaceship is sophism.

 

Perhaps, but no more so than stating conclusively that FTL travel is impossible because our current understanding of the universe tends to indicate that is may be.

 

Well, it is theoretically possible; via warp drives or wormholes (although this is questionable and relies on negative energy which probably does not exist). No one is arguing that; the argument is that it is practically impossible particularly within the timelines of my book.

 

I see. That makes sense. Plus, I've always liked the idea of these kinds of beam ships. Science fiction writer, and physicist, Dr. Robert L. Forward, had an idea for decelerating them that used a secondary sail system on the craft. When it was time to decelerate, the first sail system used to accelerate was jettisoned from the craft, and light reflected from it impacted the secondary system to slow the craft.

I don't know if you can get the whole article here, but it is worth a look: http://arc.aiaa.org/doi/abs/10.2514/3.8632

 

Thanks, I have read around this. While I understand what he is getting at, it has been shown (by peer review, at work and don't have the links handy) to be practically impossible because there would be insufficient energy from a laser positioned 12 odd light years away to decelerate the craft (again within the timelines of my book).

I know this all sounds rather anal, but I want minimal hand waving.

 

I can see where that would be the case, but if you're using lenses then the deceleration would be more effective, wouldn't it? In any event, it's all very interesting and I think makes for good elements to a SF story.

 

Yes, that is absolutely true. The energy needed to accelerate a ~1000 tons spaceship to 0.6c is so enormous that we do not have the technology to produce it in the near future (be it in the form of anti-matter, nuclear fusion/fission or a huge laser beam). You must use some kind of shortcut here like "very large and VERY efficient solar panels placed VEERRRY close to the Sun"

Maybe the solution of this problem will be the most plausible one (technically) whatever kind of container you imagine. I mean we know how to store anti-matter with present technology so making it better and better is not something that is unbelievable (think about how communication evolved in the past few decades)

Yes, and even without the propulsion the ship will produce so much heat (just to operate the control, communication and life support systems) that is hard to radiate away, which is the only way heat can be get rid of in space. In addition space is not totally empty, extremely sparse particles float around and in case of very high speeds they cause friction that slows down the vehicle and heats up the hull.
Hand waving and techno-babble might be better here than stating that the propulsion system works with 99.9999999999999999% efficiency and does not produce too much heat.

That's nice but this is the current situation. How much energy did we produce in form of electricity 100 or 150 years ago? How much do we produce now? The same applies to anti-matter.
In the future we will create hydrogen from water (we have plenty of that) and then helium from the hydrogen via nuclear fusion. 0.7% of the mass of hydrogen is converted to energy during the process so 1000 g of H2 becomes 993 g of He and the energy equivalent of 7 g. In theory this energy can be used to produce up to 7 g of anti-matter (but most probably less). The question is how and this is where you need to come up with a plausible idea (or ignore the problem and just say "in the 'To The Stars Project's' thermonuclear power plant 1 kg of hydrogen produces 993 g helium, 4 g anti-matter and electricity for the surrounding area").[/QUOTE]

Yes. Using the lenses show the reader how much effort is needed to reach to the stars but you can achieve the same goal by writing about a 100 km/miles long laser located in space.
Of course the dramatic value is increased if the crew gets very excited every time the ship approaches one of the lenses and needs to bypass it by moving sideways out and then back into the beam. It's your choice and as others said already only the background of the story of your characters.