Then You Might Combine The Two
Believing that Conrad is once again harping on about that obscure Sixties sci-fi series 'Starry Trex', and the titular space charabanc with which they used to whiz across the galaxy. Art!
The U.S.S. Enterprise
Welllll, only kind of. I also want to add in a few spoilers from 'Leviathan Wakes', the first of 'The Expanse' novels, so avoid if you've not read them but intend to.
'Only kind of' because 'U.S.S.' actually stands for 'Unbelievable Super Sandwich'.
What am I blabbering about now? O I thought you'd never ask! You see, I came across a thumbnail of Richard Feynman, one of the cleverest men of the Twentieth Century, up alongside Ol' Albert, and a Youtube vlog titled "Aliens Will NEVER Arrive" from. the 'Feynman Effect' channel. Art!
Richard was a physicist, thus given to rational analysis and mathematical modelling, which he applied to the question 'Why haven't aliens arrived yet?'
Food As Fuel In his opinion, the fundamental physics of our universe prevents any such thing from ever happening, and he begins with an analogy as explanation. Suppose you were tasked with crossing the whole circumference of Planet Earth ON FOOT, with only a single sandwich to sustain you. Even on a three-decker* you'd only get about 40 kilometres over a single day. Simples! say people, simply load up with more sandwich fuel. Art!
Alas no, because all those sandwiches greatly increase the mass you now have to move, meaning you need to expend more energy, in a positive feedback loop. Conrad wonders if it wouldn't be more efficient to simply construct a single, Super Sandwich, which is where today's title comes in. Art!
ANYWAY the analogue ends up crushing our sarnie-devouring footsore traveller.
Light Speed From an analogy Ol' Rich turns to Proxima Centauri, our nearest interstellar neighbour, a red dwarf 4.2 light years distant. Art!
Given that the speed of light, 'c', is 300 million metres per second, it still takes it 4 year 75 days to get there. To make the journey there in a duration within human lifetimes requires a spaceship to be travelling at a significant fraction of c, say 10%. Thus a one-way trip at 30 million metres per second would take 40 years to get there, instead of the 100,000 we can presently manage.
Of course - obviously! - it isn't that simple, and Ol' Rich explains that a SINGLE kilogram at 0.1 c has been accelerated there by the expenditure of 45 million megajoules of energy, whereas a functional spaceship would mass in the millions of kilos. Art!
Konstantin Tsiolkovsy
Ol' K came up with the Tsiolskovsky Rocket Equation back in Tsarist times, probably as an adjunct of trying to blow up the Hapsburg capitals or somesuch. ANYWAY AGAIN you plug in exhaust velocity and desired final speed to work out how much fuel is required to get there. Art!
In 'The Expanse' series the first few volumes deal exclusively with hard sci-fi concepts, with spaceships using superheated steam for delicate manoeuvring, chemical-burning engines, as well as fusion torches and the fusion Epstein Drive. Nothing beyond the bounds of possibility, and all very, very much limited to sub-light speeds. The background to the novels is that Hom. Sap. has thoroughly colonised the Solar System but timely interstellar travel is beyond them; that enormous vessel you see to port is the 'Nauvoo', a generation ship intended to travel to the Centauri system in a journey taking centuries. Sub-light travel, you see.
Space Is Not Empty The 'Interstellar Medium' is verrrry attenuated but still has a modicum of matter lurking in deep space, principally stray hydrogen atoms and particles of dust.
Ol' Rich, postulating an alien spaceship able to travel at 0.5 c, as they are clearly in a burning hurry to get about the cosmos, meaning it's likely to get a speeding ticket thanks to traversing 150 million metres per second. Or, to put it another way, circling Planet Earth 4 times in a second. Art!
Aliens hauling bottom
I mentioned hydrogen atoms. There are 6.68 x 10²² hydrogen atoms in a single cubic centimetre of water. There is one hydrogen atom per cubic centimetre in deep space, which is rather weedy, until you realise that the alien spaceship is hitting them at 30 million metres per second or 108 billion kilometres per hour. Thus each individual atom impacts like a full-power rifle round - and 15 quadrillion (15,000,000,000,000,000) are hitting the alien ship every single second. Hope they had a good warranty deal. Art!
Then we come to dust particles in the interstellar ether. Ol' Rick mentions that these vary in size from 0.01 microns to 1.0 microns, which are too small to see with the naked eye. A single dust mote hitting the alien ship would result in an explosion equivalent to 43 tons of TNT. The density of dust particles in space is about one per million cubic metres, so the alien ship would be hitting 150 per second, or 6,530 TNT tons equivalent per second.
That illustration by Mark Van Owen above shows the effect of Tauran micro-missile accelerated up to a significant fraction of c, it being no larger than a grain of sand. It hit the military transport our protagonist and caused extensive, though not crippling, damage. And that was only one dust mote equivalent.
Ol' Rich sums up the various methodologies that have been suggested to defeat the assault of hydrogen and dust particles, none of which have solved the problem, and which indeed add more problems to the solution. Art!
This is the second stage of the 'Daedalus' space probe, mounting a beryllium shield atop to protect the main body from impacts. Whether this would work, as it was intended to reach 12% of c, is another matter. Plus the beryllium adds it's own mass to the overall probe total. The 'Daedalus' was never intended to carry Hom. Sap. just so we're clear. Good job, it was going to go an a one-way 50 year journey. Art!
Then there are the wildly exotic 'plasma shields', deploying matter in it's fourth state and able to destroy any hydrogen or dust that gets anywhere near, with the proviso that they need to be 'on' permanently and eat up enormous amounts of power. Art!
Cheating a bit here, as I couldn't find any illo of a magnetic shield for use in deep space. Once again, the magnetic fields might deflect hydrogen atoms, but dust particles are not charged positive or negative and they'd wouldn't roll off like water off a duck's back.
I fear that Ol' Rich was not at all sanguine about any alien visitors in the near future, or the middle future, or the far future, or at all, as the basic physics of our galactic neighbourhood preclude it from ever happening - hence this Snip - Art!
This is why 'Starry Trex' uses a warp drive to avoid buzzkill concepts like reality by scooting around the edges; I believe when the Enterprise goes to 'Impulse power' they are reverting, or resorting, to a fusion/fission/chemical/ion drive that conforms with real world physics. Art!
'The Expanse' gets around interstellar distances and problems by establishing 'gateways' that short-circuit the continuum on a four or five parsec level. Or is that 'Forbidden Planet'? where they also have a hyperdrive that (Cont. Page 94).
Oooops. Another Intro that ran for the entire blog. Believe me, the fictional elements I've mentioned here are merely giving the surface a light buffing, never mind a scrath. We may yet come back to this. I bet you can hardly wait.
* If you know, you know.
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