Geek call.

In the SF novel I am currently repairing (the co-authored one), there is no faster-than-light travel. There can’t be, otherwise the Earth ships could intercept the 600-year-old returning hulk way too fast and too easily.

And yet there needs to be FTL in order for the colony ships to get to distant planets. The colonists are all criminals, the ships are automated, the guards are robots. It’s a one way trip – they make the planet habitable or they die trying. There is no going back.

This does not work if it takes forty years to get there. They’ll all be far too old to do much more than weave a Zimmer frame out of reeds then build a post office and queue in it.

But – if the ship has an FTL drive, there is no way it will take 600 years to get back.

So, SF geeks, what do you think of this?

There is a FTL drive but it’s a one-shot drive. It’s a firework. The process it uses in order to bend spacetime will utterly destroy the device. So it’ll get you a hundred light years away in the space of five years but when you get there, you have no engine. No, you can’t carry two – it’s huge and heavy.

It’s a one-way trip and therefore commercially useless. All it’s good for is sending convicts on that one-way trip. The bonus is that whatever happens, Earth knows the convicts are not coming back. To add to the fun, let’s say that every drive has a 50% chance of atomising the ship mid-flight. There is no way it has any practical civilian or military application.

Six hundred years later, the fastest Earth ships are approaching light speed but nobody has solved the root problem of exceeding light speed – total destruction of the drive (and half the time, total destruction of the ship too).

That gives me a FTL engine six hundred years in the past but still has current military vessels unable to exceed light speed.

Does that work? Is it plausible, and is there any physics that could support such a premise?




44 thoughts on “Geek call.

  1. The problem I had with my FTL engine was maintaining either sub or exact light speed. Thing is you have so much momentum at this power that you push past the speed of light and time goes into reverse placing you in space a nanosecond before you hit post light speed and thus your craft crashes into itself. This of course means you never reach post light speed, so you don’t go back in time which means you don’t crash into yourself enabling you to go past the speed of light, which sends you a nanosecond back in time to the place you were about to hit post light speed.


    • Now that is a serious flaw in FTL. The time reversal would wreck the FTL drive for sure but it would wreck it while you’re still at light speed so there is no way to stop.

      How about a space-bender? Caveats: You have to be in interstellar space to use it or local gravity fields will rip the ship apart. That means it’ll take a few years to get past the heliopause at least, then you can cross a hundred light years in a moment but that puts you outside the solar system you’re aiming at. So a few more years to get to the planet from there. That solves the acceleration/deceleration issue and still has those convicts unaware that they aren’t in orbit around Earth like normal prison ships.

      Also, the forces the machine generates will destroy the machine (with a good chance of destroying the ship too) so there is no going back and it still leaves me with no FTL, 600 years later. The thing will certainly put you into spacewarp but there’s no guarantee it will bring you out. It’s no use except for transporting convicts you don’t want back. By the time Earth ships reach the planet, the convicts will be several generations dead.


      • Space benders are beyond dangerous. If you bring together major gravity or EM fields (depending on which you believe to be the dominant force) of say Alpha Centauri and the solar system the more powerful will rip the other system out of its space and claim it as its own. Our Sun would end up as part of a quadratic system with scores of planets orbiting in bizarre spirographic formations.

        To be honest I can’t see why any advanced society would waste resources on the transport of convicts. If I was in charge of such a society I would either remap the brains of criminals or reincarnate them. Space colonists would simply be frozen embryos in hyper time delayed incubators.


        • ‘Beyond dangerous’ sounds perfect. It has to have been abandoned as commercially useless 600 years later.

          The society on Earth hasn’t advanced. Politicians are still stupid.


  2. I had the vague idea that when you move faster, time slows down a bit. Which would mean that if your outbound convict ships were travelling a bit below the speed of light, time on board the ships would slow down a lot. So even if it took 40 earth years to get them to their destinations, they might have only aged 1 year (or less).

    Don’t take my word for it though. I don’t understand the theory of relativity.


  3. Yes, it seems I’m right.

    From Yahoo answers:

    Same thing would happen in space if a spaceship was traveling 1/2 the speed of light. Everything would look normal to an observer on earth, but time would slow by 1/2 to the astronauts in the spaceship.

    It’s called time dilation.

    Time dilation would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. That is, the ship’s clock (and according to relativity, any human traveling with it) shows less elapsed time than the clocks of observers on earth. For sufficiently high speeds the effect is dramatic.[2] For example, one year of travel might correspond to ten years at home. Indeed, a constant 1 g acceleration would permit humans to travel through the entire known Universe in one human lifetime.[20] The space travelers could return to Earth billions of years in the future. A scenario based on this idea was presented in the novel Planet of the Apes by Pierre Boulle.

    Does that help? It means you don’t need to go faster than light to get your convicts to their destinations. Just put them in something moving near the speed of light, and they’ll hardly age at all. Same on the way back, if needed.


    • That does help. The issue is the recent findings of possibly habitable planets which makes our choice of Sigma Draconis as a host star a little less credible. We’d have to go further out. Time dilation could help with that and also kick the story a bit – the man the heroine wants to destroy is already dead by the time she starts back.


      • Our comments overlapped. Glad it helped. You may need a star with a planet that’s 300 light years away (to make a round trip of 600 years).

        Sigma Draconis is only 18 light yeras away. This might be what you need:

        Astronomers at the European Southern Observatory were able to capture a direct infrared image of a planet outside our solar system – that’s only 300 light years away. The star is circling the star HD 95086, and although the planet itself is massive – about 4-5 times the size of Jupiter, it’s actually the smallest exoplanet that’s been imaged to date.

        Funnily enough, I downloaded data on about 32000 stars a month or two back. I have the idea that the distances of some of them are given. I could try digging out stars at that distance, or any other.


  4. I don’t quite understand your 600 year thing. Do you mean that the convicts come back to Earth 600 years later?

    If so, then with the convict ships travelling at near light speed, they might take 300 years in Earth clock time) to get to their destination, but have only aged 1 year. They then overpower their guards after a year of being on a slow-moving planet, and climb back into the spaceships that brought them their, and spend another 300 years going back to the earth. When they arrive back, they are all only 3 years older, but on Earth 601 years have gone by, and nobody alive on Earth has any memory of them. They’re only mentioned in a few history books.

    Earth spacefleet defences probably wouldn’t be able to catch them on the way back, because they’re moving near the speed of light, and the defence spacecraft couldn’t go very much faster than them. Even if they could, they’d approach them very slowly. They could only be apprehended as they slowed down to Earth speed.(I’m not sure about this, but it seems plausible).


    • “They could only be apprehended as they slowed down to Earth speed.”

      The problem there would be the deceleration from near light speed to Earth-stationary in a very short amount of time (given that you’re postulating they’d avoid spacefleet defenses through lightspeed out, say, around Saturn’s orbit.) Hmmm… of course the deceleration effects in/on the spacecraft itself might be strongly affected at the higher end of the lightspeed speed. Would a rapid deceleration be perceived by the travelers as a much slower deceleration?

      Re the atomizing chances at high speed travel: check out the Hyperion Cantos by Dan Simmons: well-written, extensive, and with some interesting philosophical elements. One of the technological subelements involves near- or FTL (I forget which… it’s been a few years…) that requires the passengers to be reduced to protoplasmic jelly in order to survive the accelerations. USUALLY they can be reconsitituted, but about one out of ten just stays as your favorite flavor of Jello.

      – MJM


      • On the way back, the ship is crawling along. It burned out/used up its speed on the way out. It wasn’t supposed to come back.

        The aliens who sent it back think along the lines of ‘why stamp on the irritating ants one by one? Give them something to take back to their nest’ 😉

        From both Earth and alien points of view, there wasn’t supposed to be anyone left alive…


        • If it’s crawling along, time will go by at the same rate as on Earth.

          The aliens who sent it back think along the lines of ‘why stamp on the irritating ants one by one? Give them something to take back to their nest’ 😉

          If that’s their attitude, wouldn’t they refuel the ship so that it could get back to the nest? Or maybe they don’t provide enough fuel. It takes energy to speed up, but the same amount to slow down. Maybe that could account for “crawling along” near the end of their journey.


          • Alien mindset – they don’t care how long it takes, they don’t care if anyone is left alive or not. They have modified the ship’s control systems so it will get there with their ‘present’ and that is all they care about. Making it go faster would achieve nothing for them, they just want us gone.


      • The deceleration could indeed be a problem. But what if they were deep-frozen to become solid? Then deceleration of many G would have little effect on them in the sense of crushing them. They might even have steel re-enforcing bars frozen into them to make them even stronger and more resistant to deformation at 300 G.

        But it’s not just the physical effects of deceleration that are worrying. While they are travelling at near light speed, a missile launched by defenders might only pursue them at 1 km/hr. But as soon as they start slowing down, the pursuing missile would start catching up. And just as they were ready to disembark, blam!!, the pursuing missile would strike.


  5. There have been a few serious studies made on how FTL might be achieved, for example the Alcubiere drive, and I recall a scheme from years ago that involved shifting the light cone around. All the ones I’ve seen require star draining amounts of energy.

    So the one way requirement is pretty simple. The drive itself may have problems but the primary issue is that it requires huge amounts of some highly refined fuel, probably toxic and radioactive to boot. Most of the mass of the ship is fuel. Once it’s used up you need a plant the size of Sellafield working for decades to produce more.

    Producing the stuff is difficult, risky, and expensive enough to make a noticeable difference to an economy. It’s not that you couldn’t double the amount of fuel, it’s that you can’t justify more than a 1 way trip politically, or economically.


    • Econonomically is good. It ties in with the use of criminals to colonise. They can’t come back and voters will not support any measures to spend money to let them come back anyway. Criminals gone for good? Damn, if Cameron could promise that he’d be on a landslide!


  6. If the ship is travelling in the Einsteinian universe, then time dilation effects apply. Your limiting factor then is the strength of human bone and tissues; bear with me on this one.

    Imagine we have a pair of one-shot devices. One dumps its entire energy load (matter-antimatter annihilation) into severely bullying the laws of gravity and pushing the ship to near to lightspeed without crushing the crew into reddish meatpaste as it accelerates. The fuel is entirely used up in this process, and as the fuel takes an enormously expensive solar-powered plant orbiting close to the orbit of Mercury to do this, the colonists are most assuredly not refuelling it to get back.

    The second device does the opposite of the first one: it slows the craft down again, by turning kinetic energy into heat and dumping this to space via a heatsink. A few million tonnes of water will do nicely for this; this heatsink would be heated to incandescence by the deceleration burn, giving a huge plume visible for huge distances. Subtle this drive is not; it is a very crude, very obvious civilian drive which no military man in his right mind would touch as it makes stealthy movement impossible.

    These two drive units get your crew to the destination planet at close to lightspeed, and cannot be refuelled to allow a return. Travelling at near-lightspeed in the Einsteinian universe means almost no time passes for those in the spacecraft, though rather more will pass for those outside the craft. Although such a craft is going fast, this time dilation effect means that anything shooting at the craft from outside is only ever going to be engaging with computers; humans think far, far too slowly to be able to respond whilst the craft is in flight.

    All this is Human-built technology; tech built by committees of semi-evolved monkeys. If we assume that the aliens have been in the game of civilisation much longer than we have, then they will have been customising their bodies and minds and will be far, far better at being civilised. The aliens will be using very similar tech to us, but infinitely more refined; something which doesn’t use crude energy systems but instead “borrows” energy from the fabric of spacetime its self to launch, and gives it back in the same way to stop; in this case both the setting off and the arrival are mostly invisible to human-built instrumentation.


      • Creating and isolating antimatter is very, very energy hungry, and the drive machines are actually destroyed by using them. To refuel them, you not only have to create a refuelling system from scratch (one assumes that a shipload of convicts will not have been gifted with a book entitled “How to build an antimatter isolation machine” as this would be tantamount to telling them how to make a planet-destroying missile) but also rebuild the drive systems from scratch, probably without the technological expertise or the materials to do so.


        • It also means the aliens can’t just refuel them or rebuild their drive (they just want the humans to piss off) so they’ll just bundle them aboard and give it a bit of a shove…


  7. A 50% failure rate is way too high, no-one would build such craft. They’d just send the convicts off with a bomb on board and say there was a 50% failure rate.
    I’m not a great one for detailed explanations, unless the book is about the scientists building the device, detail is not needed. After all if you use your mobile phone you don’t start explaining to everyone how it works (unless you are an annoying nerd). Think of how you might explain it to a politician or an elderly relative. Such explanations may not even be correct, and that might be commented on, out of earshot of the politician or relative.


  8. Quick back of a fag packet calculation shows it would take 1 year of accelerating at 1G to reach near light speed. You would travel half a light year in that time. Exactly the same figures for deceleration.
    Time dilation would slightly reduce the subjective acceleration times but once full speed established then time dilation would make the journey very short for the astronauts as Frank says.
    Not sure that helps though.


  9. When a force is applied to a body (any object) so that the body accelerates, the body to which the force is applied becomes a bit shorter during the period of acceleration. If the body is being continuously accelerated, then the body will become shorter and shorter and shorter. According to Einstein, it is not possible for such a body to reach light speed since, if it did so, it would become a perfect plane.
    That is from ‘special’ relativity. Thus, it is not possible to create any sort of engine which could accelerate a body to light speed since the engine itself would be totally flattened. If that is not enough of a problem, consider also Einstein’s conjecture that the mass of a body (that which resists being pushed) would become infinite at light speed. No force in the universe would have the power to push an object which has reached light speed. What Einstein was illustrating by these conjectures is that, not only is it not possible to reach light speed, but it is impossible to reach anything remotely like light speeds.

    But all is not lost! Gravity affects space (the General Theory). Again, according to Einstein’s conjecture (which is why Relativity is still only described as ‘a theory), the reason that light is bent as it passes close to the Sun, is that space itself is bent by gravity. If space can be bent, it can also be ‘compressed’ or ‘stretched’. What might be possible (within the imagination) is to construct a gravity machine which can compress space and thus, in effect, reduce the distance between one body and another, but it would be essential that the effect of the machine could be ‘channelled’ like a laser beam. Thus, you would take your machine into near space, point it at a place fairly close to a star which you wish to visit, press button A, and a ‘tunnel’ of compressed space appears just in front of the machine. The machine moves forward one ‘machine length’ into the tunnel. Press button B, and space is restored to normal, but you machine is now at the place near the distant star that you targeted.



    • So according to Einstein, if anyone ever reaches light speed they are flat with infinite mass and there is no way to stop.

      I’m seriously tending to the space-bender machine here.


      • Tee Hee! The whole point of Einstein’s conjectures is that the fact that ‘a body’ cannot become ‘flat’ (ie. having no volume, and thus infinitely spread). It would therefore be contradictory for such a body to also have infinitely large mass. In effect, what this means in reality (and I go here into uncharted territories!) is that there are limits to the ability of, say, steel structures to resist the inevitable pressures from constantly increasing acceleration. As with gravity, there is no escape for human bodies enclosed within the structures – the pressures will affect them equally – as is the case within space capsules on the top of space rockets. Astronauts cannot be protected against mass increases resulting from acceleration other than by special couches and body armour. But that only applies to leaving the gravitational well of the Earth. The acceleration of the rocket acts in addition to the gravitational pull of the Earth – a double whammy. But the speeds involved are minuscule compared with that of light.
        Time dilation is inevitable in these situations. There is nothing special about it. “Time” is just a measure of ‘rate of change’. Imagine an athletic event where athletes run 100 metres in 10 seconds. In a spaceship moving at half the speed of light (which is not possible), the apparent 100 metre course would only be, say, 90 metres on the face of the Earth (because of the shortening of the length of the spaceship). However, clocks would also be affected. They would run more slowly because of a sort of ‘drag’ imposed by the speed at which they are moving. Thus, they would show an elapsed time of 9 seconds rather than 10. Thus, the athlete would still run the ‘100’ metres in ’10’ seconds (in fact, as seen from the Earth, he is running 90 metres in 9 seconds).

        If you ‘see’ the above, you understand relativity to an extent.


        • There’s no time dilation in a space-bending warp engine. You are here today, a hundred light years away tomorrow.

          I already have enough maths in the near-light-speed ship in the later part, I want the earlier ship’s travel as maths-free as possible!


  10. Even if the physics been understood at the ‘Time’ a lack of access to the appropriate technology prevented Canute from properly applying himself to the task of controlling the tide,

    As I digress, the ‘Now’ disappears. All positions in the cosmos have shifted since I installed the first letter of my comment and there is absolutely no possibility of everything returning to former positions and energy states. The scenario of getting ahead of those positions is simply not survivable were it even possible to fuel such a ‘journey’ or idly jaunt across hypothetical worm-holes.


  11. Looking once more at the requirements list, I think I see an opening. The criteria are that the criminals on board the craft are on a one-way trip, and that there isn’t any feasible way for them to return.

    If instead of a magic drive we simply put them on board a craft which is powered by something simple, like a Bussard ramjet (magnetic ramscoop, hydrogen fusion reaction rocket) which needs something exotic like antimatter to keep it burning, and we put them into a sort of induced, very deep hibernation, then we fulfil the criteria.

    This way, we have the exotic, hard-to-make fuel the lack of which prevents their turning round and returning, and we also get rid of these criminals permanently. The trip to their destination will take centuries, even if they manage to come back they’ll not just be forgotten but they’ll be actual historical curiousities rather than dangerous people. The hibernation/storage won’t be without problems, either; too much radiation from cosmic rays or whatever and they’re toast (or rather, they’re toast a few days after being revived).

    The aliens in these circumstances may just want rid of these scum, or may be entirely aware of who and what these people are, and may therefore take a very dim view of our actions. The aliens, remember, will be technologically ahead of us. They will also be biologically ahead of us as well; the logical next steps for human bio-engineering are not super longevity or health, but modifications to brain structure to make us more civilised. Expansion of Boca’s Area (which deals with social interactions and recognising people) would mean we could “know” far more individuals than the current 150-ish number now; that would make us better at living in big cities.

    If we assume the aliens have made brain adjustments like this, then they won’t suffer as many of the ill effects of managerialism and working in big groups that we do; they’ll cooperate better and be a lot more group-orientated than we are. That will boost technological change and technological perfection, and reduce crime rates a lot. They’ll regard our actions of deporting criminals as barbarously vile and horribly primitive and effectively sub-sentient. The general alien feeling will be “What a load of idiotic, vile, uncivilised morons from bongo-bongo land, and they’re trying to export their scum to our turf! Let us send the scum back forthwith with a nasty note attached.”


    • The hibernation is out because they can’t hibernate on the way back. The ones who come back are many generations later, and Earth is just a legend. A promise. Sort of like Heaven for the religious. Thing is, when they do get back, they find the rest of humanity has utterly fucked up the promised land – but I don’t want to say too much!

      So no hibernation. They have to get there in 5-10 years and the one they are aiming at is only 18 light years away. That might have to change due to the modern madness of planet-finding, we might have to go further out.

      So far I am tending towards a drive that bends space but destroys itself in the process. It will have to be used out of interfering gravity wells so the ship will take a few years to get out of the heliopause and another few years to get back into the target system. I just like the idea of advanced technology that isn’t actually much use apart from getting rid oif undesirables.

      The aliens are smart enough, when ciontacted, to realise that the species they want gone also wants to go home. They will not hand over superior technology to these cometitors for planets but rather than mess about with a war, they’ll send them home. The aliens care nothing about whether the humans make it home, as long as they are gone – and the device following their ship eventuially gets to its target.


  12. Google on Miguel Alcubierre and see about his proposed FTL drive; lots of problems including vast power requirements and the use of ‘exotic matter’ which doesn’t actually exist except as a theoretical construct to make some of the science and wilder physics pan out.
    NASA are however taking it sufficiently seriously to try some preliminary work on the theory, so who knows?
    One of the commenters above said that at 1/2 light speed, time would slow by 1/2; this is actually not so, as the effects of relativistic time dilation only become really apparent at much higher speed, the dilation effects following a curve, not a straight line. If your non-FTL ship goes at 90 to 95 percent of light speed, it would have a marked effect, so that a trip of four light years would take ‘only’ about five years ship time. Better yet is about 99.9 percent.
    As far as the FTL ships being one way, thats easy, if the exotic matter ‘ring’ which allows the ship to exceed light speed fails when power is turned off at the end of the journey, the trip is one way. Since said ring would be about 10 to the minus 32 mm thick, it is possible it could fail during flight; instant oblivion as an FTL object hits the normal space/time continuum.


    • The big problems I see with FTL are first – it’s too damn cliche. Even Star Trek didn’t have FTL (except in one film where they used it to go back in time and steal some whales). Second – time reverses and third – your mass increases. So if you have a huge mass at c+1 and not enough power to slow it down, nobody can help you because you are in the past… There are too many issues that geeks (who all read SF) will bring up.

      I remember a long-ago TV interview with an author of cowboy books. He said that the readers will know the subject, and when he put a Colt ’45 revolver with cartridge bullets in a story, he had loads of letters pointing out that the story was placed two years before the gun was invented. The year he had set it in, Colts were still loaded with black powder and ball and although they had six chambers the cowboys usually only loaded five – because they didn’t all have Clint Eastwood holsters. The gun was tucked into their belt and pulling it out fast might accidentally shoot their balls off. So they left it on the empty chamber.

      Readers notice these things. It has to be not only plausible, but plausible to SF readers who are massively geeky and who will spot the flaws. In fact, they’ll be looking for the flaws.


  13. As far as the one way FTL engine… the field generated by the engine, affects the ship, and everything in it, except the engine itself. Say, it puts out a globe shaped FTL field, but the core of the globe (and power source) has to project out from itself, and therefore can’t cover itself. Once the ship drops out of FTL travel, the field collapses in on itself,and takes the generator/power source into a mini-wormhole. No way to return, ship left with conventional propulsion to land and colonize wherever.


    • I like that. It can be explained in a short paragraph without getting into any detail (all writers live in terror of that long chapter in ‘Moby Dick’ that explains all about whaling).


  14. I wonder how long a couple of super magnets in the oort cloud would take to capture all the iron that is likely to be there. I don’t know what the largest amounts of iron you can get before gravity begins to collapse it but a couple of supermassive magnetic orbs at this threshold, rotating at high velocity around each other has got to produce an energy field of some sort. Whether this field is of any use I have no idea.


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