How to Write About Long Distance Space Travel?

xlr8r321

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#1
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Hello!

I’m currently working out the details for a 3 part novel series, and I am having a hard time trying to decide how to go about explaining how long distance space travel is accomplished in my story. Here is my quandary:
- I need to move a large ship across vast distances within a time period of around 70-100 years. Think Alpha Centauri and several light years distance.
- The ship is headed for a planet that is in the process of being terraformed and that will be completed by the time the ship reaches it.
- I do not want to put the ships inhabitants into some sort of stasis, and generational travel is only somewhat feasible.

Here’s my issue: What is the best type of propulsion to use for such a trip?

I want to use something that is feasible, and that could be potentially realistic, but that I don’t have to explain in depth so that it doesn’t make the novels “hard science” novels.

Any help is greatly appreciated
 

goldhawk

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#2
Special Relativity springs to mind but the ship is moving too slow for it to have much effect. Alpha Centauri is about 4 light-years (ly) away, so "Alpha Centauri and several light years" could be about 10 ly. To travel that distance in 70 years would mean the ship is traveling at 14% the speed of light. The time dilation would be 1.010. The ship's crew would only age 26 days less than those on Earth. This is not even close to the factor you desire.
 

sknox

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#3
Wormhole.

It's going to take some not inconsiderable amount of time to accelerate to get out of our solar system, and an equal if not greater amount of time to decelerate at the other end. If nothing else, you'll have to factor for stress on the human body in both cases. So that's going to eat up a fair amount of time right there. A year at each end? Many months, anyway. Throw a wormhole in between, place it wherever you need to in order to expend the amount of time you want to have pass. That way you can make the trip take a year or ten years or a hundred.
 

xlr8r321

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#4
Special Relativity springs to mind but the ship is moving too slow for it to have much effect. Alpha Centauri is about 4 light-years (ly) away, so "Alpha Centauri and several light years" could be about 10 ly. To travel that distance in 70 years would mean the ship is traveling at 14% the speed of light. The time dilation would be 1.010. The ship's crew would only age 26 days less than those on Earth. This is not even close to the factor you desire.
Yes, you see the issue I’m running into very clearly. I don’t want to get there too quick because the vast majority of the story occurs in space, so I need time to work through the plot. Thank you for thinking it through with me
 

xlr8r321

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#5
Wormhole.

It's going to take some not inconsiderable amount of time to accelerate to get out of our solar system, and an equal if not greater amount of time to decelerate at the other end. If nothing else, you'll have to factor for stress on the human body in both cases. So that's going to eat up a fair amount of time right there. A year at each end? Many months, anyway. Throw a wormhole in between, place it wherever you need to in order to expend the amount of time you want to have pass. That way you can make the trip take a year or ten years or a hundred.
This could certainly work. Part of the journey could occur traveling to and from the wormhole which would give me time to work through the plot. I suppose I could introduce more than one wormhole as well. Here’s a follow up question: where does the wormhole come from? Is it in space already, at specific coordinates? Is it something that the ship creates through some theoretical mechanism? I would love your thoughts on this
 

Serendipity

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#7
You might like to look into Peter F Hamilton's Salvation - he uses quantum entanglement portals to travel between places, but you could for various reasons of reliability say that for humans, they have to be within a certain distance of the portal before they can use it safely.
 

Venusian Broon

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#8
Alastair Reynolds Revelation series is seen as reasonably hard - he is a astrophysicist and get a lot of his details right.

He has interstellar spacecraft that accelerate at a constant 1G for half of the distance, turn round and decelerate at a constant 1G to get you into the system. 1G is great for such a craft because then you have an instant source of perfect 'gravity' for the crew.

Said craft are sub-light, but as long as they can get continuous acceleration the crew can get to amazing distances while still aging not much. Of course to an observer on Earth they will have taken a huge amount of time.

For example see: Space travel using constant acceleration - Wikipedia

I haven't checked the graph, so beware, but it states that the crew of a 1G constant acceleration craft could expect to do a round trip to the Andromeda galaxy (2.5 million light years from us) experiencing about 60 years onboard. However from the frame of reference of an observer on Earth they would be doing the journey (the expected!) tens of millions of years.

You'll also see at the end of the article other SF that has used other schemes and you could use less than 1G and still be quite impressive in distance travelled. They should help with ideas.

Thus you don't need to aim for the closest star, you could just go about anywhere.

Of course Alastair Reynolds himself, despite nods to 'hard SF', had to introduce a macguffin in the form of the engines that are capable of producing such an acceleration. They just can :)

However talking about being 'realistic' I find the idea that you can terraform a planet in 70-100 years - say if we are talking about a very close star so that we can sort of ignore most of the relativistic effects, very far-fetched! I think terraforming an entire biosphere is a much harder and complex problem than interstellar travel.

(However if it were a constant acceleration ship, and the target was a great distance away, and assuming the terraforming equipment was sent first by itself, then the relativistic effects would give the terraforming equipment a much longer time to work their magic...)
 

Cathbad

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#9
When it comes to Sci-Fi, I know I'm in a minority on this site. But frankly, when I'm reading it, I don't wan
t to be told how everything works!

Okay, you've informed me you're moving at FTL speeds. Fine. I get it. Now move on!

:D
 

Venusian Broon

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#10
When it comes to Sci-Fi, I know I'm in a minority on this site. But frankly, when I'm reading it, I don't wan
t to be told how everything works!

Okay, you've informed me you're moving at FTL speeds. Fine. I get it. Now move on!

:D
:lol:

I can see you don't pay attention to that stuff, the original scheme wasn't FTL. ;)
 

Venusian Broon

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#12
Just an example. I also didn't appreciate the lengthy explanation why the mountains were floating, I don't want phaser schematics, nor did I care to know that Federation starships run on dilithium crystals!

:p
Actually neither do I really, but there is a something I would call 'plausibility' in fiction that is required. And that can be done deftly with little moments of show not tell. i.e. You should know that Federation spaceships run on dilithium crystals, 'cause there are episodes where the engine might blow up (cue eject the engine core, big explosion, enemy destroyed :)) etc... but I don't need to know at all how spaceships in that universe run on said macguffins!

Note, plausibility is not necessarily realism - although it can be. I also equally enjoy fairy tales, fantasy and weird fiction all having wide and varied 'plausibilities'
 

Ihe

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#14
The good ol' Alcubierre Drive could theoretically take you faster than light. If you want to have those 70-100 years, maybe you could get started with the Drive, and then it can break at the convenient time--maybe it was a planned/expected breakage because the Drive can only be used once for a limited time? Or it can be used for short bursts once a year, etc. There are many variations possible for this. Sabotage is always an option too.

You'll have to do the maths to calculate how far it needs to go before "breaking", as well as the cruising speed for the rest of the way, un order to reach your 70 year target.
 

tinkerdan

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#15
From a writers perspective I'm going to guess that the story itself is not about the propulsion so you just have to make something that works within the timeframe of the story.

I want to use something that is feasible, and that could be potentially realistic, but that I don’t have to explain in depth so that it doesn’t make the novels “hard science” novels.

I'll start with this: if you don't have a desire to make them hard science fiction then I'm unclear why you want to adhere to something feasible as in feasible to what we know to day. If you remove hard science and then start speculating about where we might be in the future you may end up with something that contains a lot of hand-wavium that makes it feasible. Authors trying to adhere to feasible from present technology has led to stories in our far future that don't have cellphones. You might want to do a light hand-wavium that you can gloss over quickly otherwise you could end up with a convoluted explanation of things that some future generation of readers are going to just chuckle about because of the heavy handed-wavium.


I’m currently working out the details for a 3 part novel series, and I am having a hard time trying to decide how to go about explaining how long distance space travel is accomplished in my story. Here is my quandary:
- I need to move a large ship across vast distances within a time period of around 70-100 years. Think Alpha Centauri and several light years distance.

I do not want to put the ships inhabitants into some sort of stasis, and generational travel is only somewhat feasible.

If stasis is out and generational travel is only somewhat feasible then it seems like you might be limited to the Lazarus effect. What I mean by that is that you need to have something like Heinlein's Howard families that have longer life spans and can make the trip out and the span of time would have to have room for those people to have families that are started and grown on the ship which requires a ship that can sustain population growth and be capable of feeding and housing that population. A near empty ship at the onset that contains enough variety of life to sustain genetically stable generations both on the ship and at the destination.

Or you need a ship that houses a vast number of people who can grow older than a 100 years and can stifle birth for those years and still be able to undo that to populate the new world.
- The ship is headed for a planet that is in the process of being terraformed and that will be completed by the time the ship reaches it.

This supposes, in my mind, that you have sent a previous expedition and requires a timeline of when that was sent out and how many years it takes to terraform. Unless you have some form of rapid communication you could have problems of verifying that the terraforming ship has made it and has commenced and you either have faith and start sending colonists at some trigger point without knowing what they will be arriving to.

Or for instance: the Terraformers take 100 years to get there. The signal takes 4 years to get back. That's 104 years before the trigger to send colonists if they want verification that the Terraforming has started. Or if the want to first establish that they can Terraform then they might add whatever number of years it takes to determine that it's a good fit. By that 104 years a lot could change in technologies for Terraforming. If there is anything they can communicate to assist those Terraforming that takes 4 years unless they have been in communication with that expedition throughout its flight.

Anyway: you definitely have to establish how long it takes to Terraform the world if you expect your colonist to arrive after it is ready. However I am interested in knowing how the Terraforming happens--is it automated and how does that equipment survive that long and how does a 4 year lag effect control of that equipment. If it is a Team of Scientists or Terraformers then how many and since they constitute the first colonists how large will their community be by that time and do they really need those colonist after so many years?

It looks like there are so many other things to consider that it might not matter as much as to how the ship sustains the flight and it might only matter that you establish the timelines for everything in a rigid manner that is tied to the capabilities of whatever propulsion you establish.
-


Here’s my issue: What is the best type of propulsion to use for such a trip?
You are effectively using the propulsion time limits as a plot device to establish that the story takes place in space on this ship and over this period of time and can't really take place anywhere else and then you will be writing a story that uniquely can't happen anywhere else.
 

Al Jackson

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#16
Nuclear Pulse propulsion could be done today (Project Orion) …. Project Orion (nuclear propulsion) - Wikipedia
A form of that system could take you to Alpha Centauri in 133 years , not a bad time frame.
When we have interstellar flight we will also have medical technology to extend live spans to 200 or more years without being decrepit at the end!

Most like in 100 or 200 years it will be possible to extend life to 1000 years of viability that makes slower than light travel a different thing.

Just think of a civilization that is advanced enough that life spans are 100,000 years...
 

Cathbad

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#17
Actually neither do I really, but there is a something I would call 'plausibility' in fiction that is required. And that can be done deftly with little moments of show not tell. i.e. You should know that Federation spaceships run on dilithium crystals, 'cause there are episodes where the engine might blow up (cue eject the engine core, big explosion, enemy destroyed :)) etc... but I don't need to know at all how spaceships in that universe run on said macguffins!

Note, plausibility is not necessarily realism - although it can be. I also equally enjoy fairy tales, fantasy and weird fiction all having wide and varied 'plausibilities'
I "kind of" agree. ;)

Although I don't necessarily want to hear it, the author should know how things work. It usually shows when they do not.
 

sknox

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#18
The whole time relativity thing is why intergalactic doesn't work for me without wormholes, portals, FTL, or similar jump tech. Because if even a couple of centuries pass back home, it pretty much negates communication and trade between worlds. I'm not going to buy a car (or a spaceship) from you if it takes three generations to get here and another three for the check to clear.

People would still go to the stars, but they'd be an entirely different sort. They'd be religious or political refugees, criminals, idealists, and generally people looking to start a whole new life (funny how those go together). People who wouldn't care about "back home." Humanity would be a series of isolated islands.

To the OP: you could place wormholes where and as you please. If the whole travel thing is minor, then just make it one and done. If the travel is the point, have multiple wormholes.

How do they know where to find them? Do wormholes drift? Such things can ramp up tension, and differing opinions among the crew could ramp up conflict.

If the ship can create wormholes (essentially equivalent to an FTL drive), you can still control how many jumps are needed. And, as has been done a hundred times, you can have the tech fail at some crucial point.

You have a whole galaxy of possibilities.
 

Dan Jones

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#19
Here’s my issue: What is the best type of propulsion to use for such a trip?
Depends on your timeframe, but there are some esteemed propulsion engineers (one or two with whom I've worked) who believe that within one hundred years we will have developed and refined existing electric propulsion technology to the point where we could achieve delta velocities of around ∆40km/s. This would allow spacecraft to travel to Mars in 2 months, Saturn in 1.8 years, Neptune in 6.4 years and the very edge of the Solar System well within a lifetime. At these speeds it would take around 22 years to travel 100 Astronomical Units (AU). However, this doesn't really solve the problem of interstellar travel, considering that Alpha Centuari is something like 250,000 AU away.

But the technology could be pushed, in theory, to generate vastly increased velocities, potentially up to 154km/s.

So how does it work? Electric propulsion uses three main components: a thruster, propellant, and a power supply. Your thruster, powered by the power supply, fires the propellant particles into a chamber where they are ionised, creating a neutral plasma. This plasma is then accelerated in one of two or three different ways (electrostatic, or separation of electrons and ions and induction of separate electric fields) as a jet through an exhaust. If you remember your Newton's 3rd Law of motion, this thrust acts against the outer environment (in this case, space), and generates thrust. The jet can be accelerated to induce a steady, constant acceleration, and in theory you can reach some very high speeds indeed using this method, at a high efficiency.

The thing about this tech is that it's theoretically scalable, so if you increase the power to accelerate your electrons, you get more thrust. But to generate this sort of power you need a nuclear power supply, which is kinda dangerous (not to mention extremely expensive, although you could theoretically use cheaper Americium as a fuel rather than plutonium - in fact Americium is a byproduct of plutonium processing (I can't remember which isotopes though).

So you don't just need to make a more efficient propulsion system, you need to make the spacecraft itself into the propulsion system. To do this you could have to create a spacecraft that would be capable of generating its own substantial, superconducting electromagnetic field, and electrical currents running across it in the range of millions of electron-volts, probably using in the region of dozens of Megawatts of power. Alan Bond, who used to work at Reaction Engines, has postulated that such a vehicle would look like a Flying Saucer, which is is pretty cool. The craft would weigh about 15 tonnes, require tungsten shielding, some serious heat rejection / radiator capability to dissipate the heat generated (which would be substantial)

So that's sort of getting there, although strictly speaking is probably not enabling interstellar travel (I've done some back-of-a-fag-packet sums, and I reckon it'd still take, er, 8,400 years to reach Alpha Centauri using the upper performance levels of this capability). Even so, this represents the limits of what we currently know with existing tech*, and would enable us to get to the very edges of the Solar System (the Oort Cloud etc). Which is still cool.

But - and this is important - you're writing science fiction, so if you just want to convey a realistic piece of futuristic engineering, all you have to do is massage the figures, use a bit of handwavium to get around the nuclear problem and you could pass this off easily as a viable futuristic piece of space propulsion kit in a couple of hundred years' time that could reach Alpha Centauri or wherever.

Of course that's assuming that the various countries of the world can work together sufficiently harmoniously to make it work. Not impossible, as space is one of the few areas where the world does see, to be able to cooperate and collaborate on a global scale. Not that there aren't disagreements. Note the planned Lunar Gateway. But that's a whole other story...

It's worth mentioning that almost all of the "engines" that are depicted in SF are some form of electric propulsion thruster. The Enterprise has an Ion Thruster (not the Warp Drive, which is basically magic :)); the Battle Cruiser in Star Wars uses Gridded Ion Engines, and so on.

*Alternatively you could use solar sails, but that is still theoretical tech and I don't know much about that!

ETA: I forgot to mention, for this propulsion method, you will need a propellant that is safe, non-contaminating and inert. Kerosene is not an option here as it's not efficient enough. Really you'd want stuff like Argon, Krypton, Xenon, those sorts of guys who play nice and won't explode when they get irritated. Also, if you land on a planet with water you could use cryogenics to separate it into liquid hydrogen and oxygen, which you could then use as more fuel. So it's a pretty flexible system, too.
 
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OHB

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#20
This is just my opinion, and you're free to ignore it: If it's not hard sci-fi, then I'm not sure you even need to explain the propulsion system. Tech in soft sci-fi can take a black box approach. The readers don't have to know how something works to know that it does. Really, it would only need explaining if you plan to have something go wrong with it (eg. engine breaks, core melts down and explodes).

I like to use the Alien movies as examples. In the original Alien, we have no idea what is propelling the ship (at least, I don't remember it being explained), because it has nothing to do with the story. In Alien: Covenant, we know they use light sails. Why do we know this? Because they break in disastrous fashion, which serves as a plot point. If everything is fine with the propulsion system throughout your entire series, then you really don't need to delve into the techno babble. Just say, "With our fuel [you can give it a fancy, made-up name if you want], it'll take us [insert number] years to get to [insert destination]." I'll believe you. But again, this is just my opinion.
 
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