There are many reasons one might have reservations about Robert Heinlein’s 1966 The Moon Is a Harsh Mistress—the peculiar stats, the reliance on a nigh-all powerful AI on the rebels’ side, the inexplicable moment where the narrator creepily objectifies a dead tween as she is violently killed—but for me, Heinlein’s use of kinetic weapons ranks especially high on my list.
I know a lot of you are too young to know what I am talking about—the book is, after all, ancient beyond measure—so a quick explanation: in the novel, the rebels commandeer a linear accelerator to lob cargo pods full of rocks to the Earth. The shock and awe inspired by the orbital bombardment helps to sway the Earth into granting the Moon its independence.
On the surface, this seems plausible. A quick back-of-the-envelope calculation assures one that this would be quite vexing to anyone standing where the rock happens to land: at 11 kilometres per second, each kilogram of rock would have about 60 megajoules of kinetic energy, more than ten times the energy of a kilogram of TNT. Nobody wants more than ten kilograms of TNT exploding on their lap.
But…a moment’s consideration should raise concerns. For example, the rebels are using repurposed cargo vessels. How is it they are able to reach the surface at near-escape velocities without fragmenting on the way down? How did the rebels manage to erase Cheyenne Mountain from existence when (given the numbers in the book) it would take about two hundred thousand impacts to do so? How did the rebels cause a tidal wave in the UK when simple math says the wave would only have been a few centimetres high at Margate?
Heinlein probably relied on a simple but useful technique: he didn’t do the math. Perhaps he didn’t have access to the proper equations (although one can make do with Glasstone’s The Effects of Nuclear Weapons, and who doesn’t have a copy of Glasstone within reach?). Perhaps it was just too fun an idea to ruin it with mere facts. He did succeed in convincing a lot of SF authors that kinetic weapons moving at mere kilometres per second could have nigh-nuclear impact, when in fact they are only about an order of magnitude more energetic than chemical explosives. To get nuclear-weapon-level damage from impactors, either the impactor has to be moving a lot faster than interplanetary velocities or it has to be massive.
Nevertheless, Heinlein’s dramatic licence in The Moon is a Harsh Mistress has inspired a number of authors. Take these four other books, for instance:
Footfall by Larry Niven and Jerry Pournelle (1985)
The dismal prospect of a progressive (and thus feeble) America supine under the Soviet Union’s inevitable and unstoppable superiority becomes a side issue when aliens attack! They use the kinetic gambit: showers of small hyperkinetic missiles and one large one (result: a four thousand megaton impact to the Indian Ocean). The aliens are in orbit around the Earth and cannot be stopped by humans stuck down on the surface of the planet. Oh the humanity!
The hyperkinetic missiles will be familiar to anyone who has read up on Project Thor. These “rods from god” are a proposal that comes up from time to time, their development stymied by trifling obstacles like large orbiting objects being visible, the fact they can only be directed at specific targets at particular points in their orbit, the challenges of maintaining weapons systems in orbit, and the fact there are easier and cheaper ways to accomplish the same goals.
For some reason, the authors grossly overstated the effects of a four thousand-megaton impact detonation for dramatic effect, as I will no doubt have excuse to show in comments. It’s a head-scratcher, because there’s no reason the aliens could not have used a much larger impactor. The lesson here may be “never be too specific about anything the readers can double check.”
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Red Mars by Kim Stanley Robinson
Robinson opts for the large impact option, when the Martian rebels hurl an asteroid dubbed Nemesis at the Earth. Given that the Mars series pays lip service to plausible science, readers may wonder how exactly something large enough to cause mass destruction could reach the Earth without space-capable Earth spotting its diversion and taking steps to deal with the menace in the weeks or months it would take an asteroid moving at plausible interplanetary velocities to approach our planet.
In a rebuke to traditional SF tropes, this is exactly what happens: Earth notices the threat long before impact and takes appropriate steps.
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Scardown by Elizabeth Bear (2005)
Toward the end of this novel, China rebukes Canada by bombarding Toronto (a city in Ontario, FYI) with a 90-metre object moving at 14 kilometres per second. The results are apocalyptic: immediate fatalities in the tens of millions, with more come as the long-term environmental effects kick in. Only a churl would break out their slide rule to calculate that the kinetic energy is probably roughly comparable to the Hiroshima bomb, undesirable from a Torontonian perspective but hardly enough to affect the whole Earth. That is to say, it would be if it reached the surface, which such objects generally don’t. In practice, the object would likely fragment so high in the atmosphere that the surface would remain undisturbed.
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Nemesis Games by James S. A. Corey (2015)
Nemesis Games belongs to the Big Smashy school of orbital bombardment. But because Corey’s setting has two space-capable superpowers keenly invested in tracking each other’s assets, the plucky rebels (alternatively known as the deranged mass-murdering fanatics) have the additional challenge of getting the rocks to their target without being spotted first. This is accomplished with an anti-detection coating. This doesn’t really address the issue of how the IR from the rocket burns needed to divert the rock were concealed. At least Corey was aware that the novel needed at least some handwaving to justify sneaking up on a world with mountain-sized objects when mere 21st-century technology is doing a bang-up job of cataloguing potential impactors (not to mention the fact that we’re not even motivated by the presence of an off-world hostile power).
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No doubt you have your own favourite examples! The comments are below!
In the words of Wikipedia editor TexasAndroid, prolific book reviewer and perennial Darwin Award nominee James Davis Nicoll is of “questionable notability.” His work has appeared in Publishers Weekly and Romantic Times as well as on his own websites, James Nicoll Reviews and Young People Read Old SFF(where he is assisted by editor Karen Lofstrom and web person Adrienne L. Travis). He is a four-time finalist for the Best Fan Writer Hugo Award and is surprisingly flammable.
Strictly speaking, that should be four that get the details wrong and one that didn’t.
For Nemesis Games, you don’t need a chemical rocket to divert an asteroid — a mass driver on the thing would do just as well. Or a gravity tractor. And The Expanse runs on reactionless thrusters (“Epstein drives”), not chemical rockets with bright IR signatures.
To quote from Leviathan Wakes:
Epstein drives are bog-standard mysteriously efficient fusion drives, of the sort found throughout SF, not physics-breaking reactionless drives.
Generally speaking, none of the methods that can be used to divert rocks lend themselves to stealth. Either they involve prodigious amounts of energy over a short time (it doesn’t matter how you get the exhaust up to many km/s, you still need to provide the kinetic energy of the reaction mass stream) or if you’re exploiting flybys, you pay in duration and predictable launch windows.
It might be stretching the definition of “kinetic weapon” more than a bit, but I also remember the beanstalk incident in — was it Green or Blue Mars? — being pretty spectacular.
Stephen Baxter makes uses of large impactors in several stories and novels. Xeelee: Vengeance is one.
We should just let these hard-sf authors off the hook for their terrible physics when everything else — in their view correct politics, especially — more than make up for it.
Umnh,
No. When you claim to be writing “hard sf,” you lose the privilege of handwaving away basic physics errors. Of course, https://www.purdue.edu/impactearth/ — Impact Earth — wasn’t available on the Web back when Heinlein was writing.
———
Bad physics involving kinetic weapons has a long history in fiction. Just look at western movies ;)
Heinlein’s Lunar rebels don’t use repurposed cargo pods full of rocks, they put enough steel around very large rocks that the magnetic cannon can accelerate them to lunar escape velocity. That does beg the question of whether very big lunar rocks could maintain cohesion as they passed through the atmosphere, but it’s not the same as having a bunch of smaller rocks stuffed in a cargo pod. As it is, it still takes multiple bombardments over a couple of days to get Earth to give in,
TMIaHM also represents the second time in consecutive novels that Heinlein wiped Colorado Springs off the map, right after he moved away from there. Makes you wonder what he had against the place.
If you make your hard science fiction too heavy on the science then you lose the fiction part. There is always a trade off, you can have a story or a science text but not both. And I’d rather have a story.
E. E. Smith had perhaps the most realistic consequences of an impactor, given that you can acquire an extradimensional supraluminal planet in the first place.
@swampyankee “Impact Earth” doesn’t appear to be available on the Web now, either, with Flash desupported :-)
Moon is one of my favorite Heinlein’s. I am a total sucker for alien societies and what I know about physics could be printed on a small card.
<cough>windmills</cough>
@7: As I understand it, Bob and Ginny loved Colorado Springs and were bummed that her health required they leave.
@7: The Navy and the Air Force are rival branches – and Heinlein was a Navy man.
aaaaaaauuuuuuuuuuuggggggggggghhhhhhhhhh i’d managed to suppress memory of the windmills.
Not only do SF writers have no sense of scale, as TV Tropes puts it, neither do most other people, including SF readers.
At least some of this, I think, comes from not realizing that a 100-meter sphere doesn’t have a tenth the mass of a one-kilometer one, only a thousandth of the mass.
But James, you left an important question unanswered – did The Expanse get the smashy-smashy physics part right?
@10, there’s a Flash-free version. It’s linked from the Purdue site, but here is the direct link: https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffects/
See, this is why, when I use kinetic impactors, they’re one of two things:
1. Coming in at significant fractions of the speed of light;
2. Planet sized;
I figure once you get into territory of ‘we think this might be what created the Moon’ level of collision you’re probably ok for saying the effects on the target were catastrophic.
Who doesn’t have a copy of Glasstone within reach?
I posted a writeup of my quick back-of-the-envelope calculation (does anyone actually do those anymore?) regarding The Expanse‘s depiction of rocks hitting Earth on another thread, but here it is again (shred at will):-
I love The Expanse, but the writers really botched the numbers at the beginning of this episode. Twice.
First, the physicist that Avasarala is asking for advice estimates an impact energy of 1 – 4 megatons of TNT given an asteroid diameter at 10-30 metres and assumes a nickel-iron core (which seems unlikely given the way it broke up around Venus, but let’s go with it). Assume a diameter of 20m, or a radius of 10m. Density of iron is about 7g/cm^3, and the densities of Pallas and Vesta are around 4.3, so let’s assume 5g/cm^3, or 5,000Kg/m^3. He then mutters something about the velocity at impact of either 3,000 or 30,000 kilometres per hour — I can’t quite tell, and ‘kilometres per hour’ is not a unit a physicist would use, but, again, let’s go with it. Minimum entry velocity at Earth is actually 11 kilometres per second, which is 39,600Kph, so let’s assume that.
Volume (V) = (4/3)pi*r^3 = 4,188m^3
Density (d) = 5,000Kg/m^3
Mass (m) = d*V = 2.094×10^7Kg
Velocity (v) = 11,000m/s
Kinetic energy at atmospheric entry (Ke) = (1/2)mv^2 = 1.26687×10^15J
That translates to an explosive yield at impact (assuming an impact angle of 90° and negligible loss of velocity) of about 300KT of TNT, which isn’t that much — okay, it’s about 10 Hiroshimas, but that’s peanuts (it’s basically the yield of a single Minuteman III ICBM warhead). It’s nowhere near 3-4 megatons, a yield 10 times larger. In comparison, the Tsar Bomba device detonated by the USSR — the largest nuclear detonation in history — had a yield of 50 megatons.
Secondly, the visual that Alex and Bobbie are watching aboard the Screaming Firehawk shows a blast expanding out of the atmosphere and a shock wave spreading across a vast region of Earth’s surface, and the announcer states that the estimated yield is 300 to 400 kilotons. That image is no 300 kiloton blast, nor are those of any of the other impacts shown during the episode.
300KT is puny by even today’s standards. The warheads thrown around by Earth and Mars on The Expanse are enormously more powerful, and Marco Inaros is going to have to lob far bigger rocks if he’s going to teach the Inners a lesson.
In addition to getting the math wrong, SF authors are also very bad at remembering that not all kilotons are created equal.
Ten thousand tons of high explosive would do far less damage than a 10kt nuclear bomb, because high explosive does not produce nearly the same heat or kinetic energy at the point of detonation as a nuclear bomb.
Kinetic weapons (if we stick with rocks small enough to aim and fire at a target) will release more energy per ton than conventional explosives, but they’re still not going to produce the millions of degrees of heat at the point of impact that a nuclear weapon causes at the point of detonation, which means they will have far less dramatic heat and blast effects than a nuke.
@5: I believe some of those impactors in the Xelee Sequence were actually entire galaxies, which is definitely an impressive escalation of scale.
“you can have a story or a science text but not both.”
James, do you think that might be the basis of a 5 Books Where … post? ‘Cause I refuse to think that they really are always mutually exclusive.
One does run into the issue with supers that it’s hard to find targets that really demand large yields, esp given that a lot of the energy will be consumed in wasteful ways. 10 x 100 kt is going to do a lot more damage than 1 x 1MT.
With rocks from space, the characteristics of the atmosphere will constrain choice of impactors. Anything natural under 25 metres across moving at interplanetary speeds probably won’t make it to the surface of Earth.
23: What, books like The Steerswoman, where the science is the story?
Part of the issue with overpopularity of these is people not thinking about where the energy of a kinetic weapon impact come from. Conservation of energy – you don’t get a huge explosion for free. In a human-deployed Thor-like system, the energy of the impact is just (a small fraction of) the energy you put into launching it in the first place – the same sort of chemical energy that a conventional bomb would release. Thor is actually a pretty inefficient way to convey that energy, in fact.
In the case of a big asteroid impact, you are getting some energy for “free” – the gravitational potential energy of the asteroid falling to earth, and its relative orbital velocity; 10-20 km/s are so. So there the question is how that compares to the capabilities of drives you’re using. You might be able to cause an asteroid to impact with only a few km/s of velocity change if you’re patient, in which case the asteroid is a good deal; but if you need the asteroid to get there in a few months, you’re changing its velocity by tens of km/s, so the energy need for the drive is again greater than the energy of the impact – so why not just use the drive technology to make a bomb in the first place?
The king of impact weapons (and paranoia) is Charles Pellegrino. In Flying to Valhalla and in the Killing Machine, as well as in a speculative science article he urges the pre-emptive use of near c large meteors to wipe out any planet on which life is possible. This is done strictly in self defense – if you don’t, a life form might evolve which would do it to you first. Since he thinks there is no practical defense (because you detect the incoming projectiles mere minutes before they get to you) you have to strike first. It is the only way to be safe.
Help me out– I’m sure there was a novel (possibly a short series) where aliens bombarded earth with small near-light -speed missiles. The stories were set well after the attack.
I thought it was by John Barnes, but maybe not.
“Repurposed cargo vessels” seems to me to over state the strength (or integrity) of the containers intended to deliver rice from Luna to Terra (in Heinlein’s The Moon is a Harsh Mistress), and repurposed by the rebels to deliver rocks for kinetic impact. They’re light steel shells, just enough to take the acceleration of launch (and unmanned, they don’t need to be airtight or anything).
And it seems clear to me that they were loaded with multiple loose rocks, NOT a single carefully-cut block (among other things, they’re intended for loading rice, they won’t have a door big enough to load one single huge chunk!), so dispersion during reentry does seem likely. (Huh; I wonder how full they would be? Because rock is rather denser than rice, and I doubt the catapult can handle a load much higher than usual, so they probably wouldn’t be full of rock.)
I assume what we know about masses of meteors, and observations of which fragment in the atmosphere, dates to before the writing of TMiaHM (mid 60s)? That’s the only excuse I can think of off-hand :-) .
Personally I always assumed they were big chunks of rock and wondered why they needed the casing.
@28 — Was that Pellegrino & Zebrowski’s The Killing Star noted in 27)? In the first chapter or two of the book, 99.995% of humanity is wiped out by a series of near-c impactors.
[EDIT: I meant The Killing Star; The Killing Machine was one of Jack Vance’s Demon Prince novels, which I don’t THINK had any near-c impact events.]
@28: If it’s John Barnes you’re thinking of, that’s The Duke of Uranium and its two sequels.
30: My memory is the accelerator used magnetic fields to accelerate the payloads, so no metal and the payload does not go anywhere.
@27: The Killing Star, I think, not the Killing Machine
David Weber’s Honor Harrington books have several instances of attacks on surface targets using kinetic energy weapons (basically the Thor Crowbars From Space all grown up and equipped with gravitic drives capable of accelerating to large fractions of C). Then in the Mutineers’ Moon series, the Aku’Ultan use Iapetus in an attempt to attack Earth (having routinely used kinetic bombardment to scour planetary systems clean of life-which-is-not-Aku’Ultan).
I was waiting for you to mention Nemesis Games.
@33, I never thought of that until now.🤨
The math is way outta my league; but I think Weber did indeed do well with his KEW strikes; gruesome.
@29 – actually they quite probably could have cut the rock to fit the casing; they have a lot of miners and use lasers to cut tunnels to live in. That’s how Manny Garcia O’Kelly Davis lost his arm, I believe. Even if they used loose rock the shells that were originally used for delivering rice would have had to make it to the surface with the rice intact and uncooked, so there would be no dispersion of the loose rock.
OK, so I have an innovative idea for home delivery of pop-corn.
My problem with Moon was the food export, even before they got to the bombarding earth bit. I don’t care how overcrowded Earth is, if you can grow economically significant amounts of food in underground tunnels, it makes a lot more sense to dig tunnels on earth and grow rice with desalinated sea water than it does to import food from the moon. I guess it’s a variant on the “why colonize Mars when the Atacama Desert and Antarctica are right here” problem.
@8: Planetes has excellent hard science in it, and in Rocket Girls the science is diamond hard. If two Japanese manga can do SF stories that would be possible in the real world, then it’s obvious it’s more a matter of “won’t” no “can’t”
If you get a 100 meter rock up to interplanetary speeds you get a Tunguska level event. Of course you want it to go boom a few kilometers up to maximize the damage. A 20 meter object gets you a Chelyabinsk level event, which will definitely get everyone’s attention without quite killing anyone on the ground.
In the book of Nemesis Games, the only time they discuss specific numbers, it’s a bit more plausible (I suspect they deliberately didn’t mention may hard numbers):
(ie 200km/s, which gets you into the tens of kilotons of kinetic energy per ton of mass)
It’s a bit of a shame that this bit didn’t make it into the TV series, because it’s a nice example of how Amos has picked up a lot of science just by doing a highly technical job. He’s not Timmy from the block any more.
In the books, ship’s drives are only detectable when the viewer is almost directly behind them, so they pick manoeuvrers that will hide their exhaust plume from the inner planets.
wiredog @@@@@ 44
A 20 meter object gets you a Chelyabinsk level event, which will definitely get everyone’s attention without quite killing anyone on the ground.
It also depends on the composition of the object. Stony meteors like Chelyabinsk are much more likely to explode high in the atmosphere, doing less damage to the ground underneath. (The fact that the Chelyabinsk bolide came in at a shallow angle also meant that its explosion was spread out over a line on the ground below, rather than concentrated on a single point as you might get with a more perpendicular impact.)
I believe the Barringer Meteor Crater is thought to be the result of a 30-50m-diameter nickel-iron impactor; one study suggests about 2.5 megatons of impact energy on the ground, plus another 6.5 megatons in the air burst above.
So, depending on the impact angle and the velocity, a 20m nickel-iron object might do more damage on the ground than the Chelyabinsk bolide did.
@41, Yeah, that occurred to me too. Heinlein attempts to handwaved it by highlighting the Moon’s shallow gravity well versus Earth’s deep one making one way transport cheap but still….
Although even that can get ridiculous. I recall a discussion regarding the joint strike plan the UK, US, and France developed. Basically, they’d agreed that the most effective way of using their strategic weapons in the event of a full-blown Big Whoops was to coordinate so some targets didn’t get overloaded with weapons bouncing rubble and while others didn’t have anyonme shooting at them. Even then, Moscow was still supposedly targeted with 30-ish Exciting Physics Devices ranging from a few hundred kilotons to a few megatons.
Yeah, the benefit is you pay in 2.5ish km/s to get 11ish km/s at the Earth end. Since Ek is proportional to the square of the velocity, that’s a nice Ek bonus. It still works out to somewhat better than chemical, nowhere near as good as nukes, and you’re looking at days before the payload gets to its target.
One of the odder applications I’ve seen was Donald Kingsbury and Roger Arnold’s “The Spaceport”.
It featured a linear accelerater in orbit, which would catch and accelerate payloads launched from the Earth at half orbital speed. To balance the momentum lost catching payloads, payloads from the Moon would be sent to the same facility. Basically, it’s sort of a bucket system where stuff going up is counter-weighed by stuff going down.
@40: now I’m seeing the end of Real Genius….
@49: I recall a proposal (possibly a story) to do something similar just for Earth orbit — low-orbit cables that would add KE to up-bound loads and absorb it from down-bound. This would have been a few decades ago; does it ring any bells?
Hans Moravec’s A Non-Synchronous Orbital Skyhook?
Tough SF has an interesting discussion of rotating tethers here.
@51: Rotating tethers turn up in Benford’s City and the Stars sequel.
People have eye-rolling about KSR, but in 2312 he did include a neat answer to most of the kinetic-impactor-as-weapon problems that have been brought up here. In his future world, scientific and computational advances have made astrodynamics predictions far more accurate, so when a shadowy entity wants to destroy an orbital habitat, it launches millions of micrometeorites at different places and times across the solar system with just the right trajectories so that in a period of months or years they’ll all converge on the target and sandblast it to rubble. Each individual impactor is below the size threshold of detection systems and they can all be launched at different times and places with trivial energy per object.
#28, Nancy Lebovits, I agree with Patrick Morris Miller’s #32; the series you’re thinking of is John Barnes’ Jak Jinnaka trilogy, starting with The Duke of Uranium. Mention is made of Earth’s continents being peppered with large circular lakes, the results of kinetic impact attacks from space many years previously.
(It’s a really interesting series, not just for that relatively minor bit of worldbuilding. I’ve described it as both a homage to Heinlein juveniles and a deconstruction of Heinlein juveniles.)
@@@@@ 7
I read that Heinlein doomed Colorado Springs so often because it had been deemed the safest place in the US from nuclear strike, and then they built NORAD. It irritated him a little.
32. Patrick Morris Miller and 54. bruce-arthurs
Thank you, I thought it was that series, but when I looked at the summary on wikipedia, it didn’t seem to have the bombardment.
41. Nickp
In re agriculture in the moon: Governments are fabulously wealthy, and sometimes they take on large projects that don’t make sense.
General question: I’ve heard that navigation at close to light speed over long distances isn’t feasible, so there’s no need to be worried about that sort of an attack from distant civilizations. True?
The problem with any place known as the safest place in case of nuclear attack is always guaranteed a nuke of its own on a “just in case” basis, simply because it is reckoned the safest place. If you want a real safest place in case of a nuclear attack, well other than it being on another planet because there is no safe place but if it is to be on this world, then you want a place nobody ever considered at all. As soon as it is known, it stops being so.
Ah, memories of the couple determined to escape the radioactive frying pan the UK would become in a nuclear war by moving to an out of the way, obscure island chain few in the early 1980s gave any thought to: the Falkland Islands.
@58: Like the farmer who moved away from Mananas after the first battle of Bull Run – he picked a quiet place called Appomattox https://en.wikipedia.org/wiki/Wilmer_McLean
Why would anyone think the Malvinas would be a safe place in a nuclear conflict? It has always had a strategic UK naval function ever since the UK occupied it, it would be guaranteed a strike no matter what.
Just to come back for a moment to
the reliance on a nigh-all powerful AI on the rebels’ side
This element is so sloppy, it makes the whole story seem like either a parody or a really cheap trick.
I enjoy the rocks, accurate or not. Possibly my favorite element; I certainly wouldn’t want them taken out. Not that I would object to more realism, but for a first pass it doesn’t seem at all necessary.
On another topic, having made mistakes in print, I’m just glad the windmills weren’t one of mine. These things happen. A bit like injuring yourself around the house – it generally happens just as you’re feeling quite pleased with whatever it is you’ve accomplished.
IIRC Larry Niven used a kinetic weapon in one of the early Man-Kzin War stories, where the humans destroyed a target on a planet in Kzin-occupied Alpha Centauri system with an impactor that was accelerated to a considerable fraction of light speed (hence, almost impossible to stop if not detected very, very much in advance).
Nevertheless, it didn’t do that much damage, but was meant more as a morale booster for the occupied humans: we haven’t forgotten you, we are coming. Can’t recall the name of the story, though.
Some of my most traumatic experiences in box office at the theatre followed immediately on the heels of a feeling of calm assurance that I knew what I was doing and that things were going well. For example, my discovery mid-way through selling tickets for a popular show that if a software update gets pushed, it shuts down the printer for longer than I had before box office closed. As a consequence, I try to keep my anxiety levels just short of throwing up.
The only thing I know of worse than “this is going well,” is “At least it can’t get worse.” It can always get worse. To quote Malvina Reynolds:
@50 chip137
Kind of like this inclined plane railroad?
https://www.inclinedplane.org/history/
@63
In AA we talk about “the bottom” when things get so bad we finally get sober. For some of us the bottom is realizing that we will, soon, be dead, and it won’t be pretty. (Some don’t stop there, though..)
Or, as I’ve said (may be quoting someone) on occasion, “Sooner or later we’ll all be dead, and this will all be over.”
Heinlein didn’t have the computing power that you take for granted. It would have been hand calcs on paper and sliderule.
Niven and Pournelle had orders of magnitude better computing resources but still would have been time consuming to work out for no improvement in the final work.
Even now, Sithrak oils the spit.
(from the stupendously NSFW Oglaf)
So do the rods in Anathem fall into this category?
There’s a piece of flash fiction, WH40K fanfic I think, that crops up on social media from time to time that I think is relevant. It takes the form of a memo from a senior Imperial figure to the various fleets reminding them that while “Rocks are free”, the cost in fuel, time, as well as the repairing the resultant wear and tear on ships mean gathering asteroids for kinetic bombardment isn’t recommended…
@66: Heinlein did do paper and slipstick calcs for his books… sometimes. He and Virginia spent three days grinding out orbital elements that informed one single line of Space Cadet.
And he totally bobbled the relativity calculations in Time for the Stars that a junior high schooler could do on the back of an envelope, to three decimals, in a minute or so.
The Moon Is a Harsh Mistress “ancient beyond measure”?? Hey, I was 16 when that was published! I’m not dead yet.
On a smaller scale and more recent
The bombs made of reinforced concrete plus laser guidance used by the RAF in the Iraq war as tank killers.
Is this a fact or fiction
@72: fact, or at least the guided concrete part – dunno if tanks specifically. JDAM packages are designed to strap onto a dumb bomb and turn it into a smart bomb; if you just need thump, not kaboom, you can attach them to anything the right shape and size.
Not really. The Martian easily manages to do both, for example. And in many of the examples given here we’re literally talking about just changing a couple of numbers in the dialogue to make it more accurate without changing the actual story at all.
Getting your science right doesn’t mean you have to spend a lot of time describing it in the actual novel.
“How is it they are able to reach the surface at near-escape velocities without fragmenting on the way down?”
As has already been noted, they were tossing rocks banded with steel, but that’s actually immaterial. What difference does it make if the rocks fragment?
1000 tons of rock hitting at high velocity is still the same energy whether in a single piece or in multiple pieces.
@62 Possibly Destiny’s Forge?
@72
I call it fiction. I used to live near where the raf trained. Half those pilots could drop a bomb and miss the ground.
@77 it is fact sources retired sergeant of an anti tank platoon,
Retired SO from the RAE.
As the payload breaks apart into smaller pieces, surface area to volume increases. As a result, atmospheric braking soars, the forces acting on the fragments soar, and the pieces continue to break up and the cycle repeats. Or to put another way, the object explodes in the upper atmosphere.
@79 — Although that’s why some of the “blow up the asteroid/meteor/comet before it hits the earth so it just burns up in the atmosphere” stories have the opposite problem — if the impactor is big enough to be a planet-wrecker on any significant scale, breaking it up might mean that it won’t make craters on the surface (or as many craters, or as big), but it’s still going to dump all of that thermal energy into the atmosphere with deleterious effect.
Yeah, turning the sky into a giant oven is what the experts call “bad” but you need a large object for that to be an issue.
kayom @@@@@ 60
Why would anyone think the Malvinas would be a safe place in a nuclear conflict? It has always had a strategic UK naval function ever since the UK occupied it, it would be guaranteed a strike no matter what.
I don’t know; I have the impression that any “strategic naval function” for the Falklands kind of went away after the Royal Navy stopped using coal. When the Argentines invaded in 1982, the British military establishment consisted of several dozen marines with small arms and… that was it.
Not to mention the fact that the great-circle distance from the south-westernmost Soviet ICBM base (Dombarovskiy Air Base) to the Falklands is something like 16,000 km, which is beyond the range of almost all land-based Soviet ICBMs, and would have required a ballistic-missile sub travel into the South Atlantic, where they probably wouldn’t have been able to the hit the US. So I’m guessing the Soviets put zero effort into trying to target the Falklands.
@80
That answers the question I’ve asked before and not gotten a good answer to. Thanks.
@74 – the Martian
The science in the Martian is pretty good…. except for the setup to get him stranded to begin with. He had to cheat to get a plausible scenario where Mark would be left behind.
(From what I understand, I’m not an expert)
72/73: the story is gen, but the interesting bit, which might bear on James’s post, is that it didn’t work. The idea was to hit tanks hiding in cities where the blast radius of the bomb would be unacceptably dangerous to civilian bystanders, but it turned out that the inert lump was very much less easy to control than the explosion – it tended to burrow under buildings or cartwheel across the surface at unpredictable angles for surprising distances from the aim point.
Shades of a demolition whose video I watched where instead of falling straight down, some of the potential energy of the standing building was transformed into kinetic energy of objects moving sideways, to the tremendous surprise of the crowd watching from what they had been assured was a safe distance.
@86
Surely you’ve heard of the Oregon Highway Department’s somewhat less than successful attempt to remove a dead whale from a beach?
Dave Barry’s article on whalemageddon was the first piece of his I read.
@85 Thank you for exposing those two windup @78.
Although they both stated use of the concrete kinetic was it open desert where I presume the side effects would not matter.
@87: Julian May used the whale story in The Many-Colored Land which is where I heard it first (in retrospect, it’s a very Miles Vorkosigan idea)
75: I should acknowledge that air resistance is only an issue on planets with air. Toss a thousand tonnes of bb-sized gravel at the Moon and all of them will reach the surface at speed. Mars has an atmosphere but not much of one, so it is in much the same boat.
@72: The tank killers in Iraq that I am aware of were depleted uranium rounds.
Nobody wants to mention Babylon-5? (Though it’s not a book, so I suppose it’s off-topic technically.) But the Centauri do bombard Narn with kinetic weapons.
@41/56: In tMiaHM, the Moon is a dumping ground for undesirables, mostly outright criminals; RAH was clearly thinking of Australia, without all the details about levels of freedom that the real Australia had. Given that people were there and that energy was plentiful (some analog of Douglas-Martin sunpower screens?), Earth could demand that transportees produce grain on pain of not getting other high-value supplies they needed (vitamins? bio-available minerals?) and couldn’t yet produce; the effort it required was Not Their Problem. Bear in mind that RAH massively underestimated the cost of getting to the Moon (even allowing for a more-efficient 3-part transport system); IIRC, at least one of his short stories showed passengers paying $30 per pound (which also had to cover life-support items that cargo wouldn’t need).
@0/@61: Mycroft wasn’t a purpose-built AI; he was an accident that became self-aware due to sheer disorganized size — the discussion makes clear that no well-run computer shop would have put that many pieces together.
@64: now I have this irretrievable image of Space Funiculars. TYSVM. (But note that the tethers don’t require that loads move simultaneously, only that the loads balance over time.)
As I understood from Nemesis Games, the rocks were accelerated farther away and if it’s not close by then the signature would not be noticeable from Earth with a lot of more drives much closer flitting around.
@90: Putting Miles Vorkosigan and Aiken Drum in the same room would be a very bad idea.
I’ve read (but cannot confirm) that the Israeli Air Force would use inert warheads in Maverick missiles used to target tanks. The missile’s kinetic energy would knock off the turret, leaving the tank salvageable.
@95: Quite. I
I don’t agree that spotting incoming massive objects is easy or straightforward. At least with hard sf it should be fairly time consuming and error prone. Spotting Earth orbit intersecting objects takes time and luck. 1) The objects don’t have to be coated in anything special to be hard to spot since many asteroids have low albedo and are almost invisible naturally. 2) In order to predict the course of a rock you have to observe it over time and even then projections are only so good for so long. 3) Rocks are gravitationally affected by each other and the planets all the time, not to mention collisions. So even if a sufficiently advanced observer has catalogued all of the asteroids they should not be hugely surprised to see them change course. 4) Predicting how all asteroids will move/collide over long periods of time is probably computationally impossible. That’s the sort of problem that would take as yet incredibly unrealistic quantum computing. 5) Even if all of the above were solved – how do you stop a big rock? Every current idea is hugely problematic, to say the least.
Not to mention the fact that any rock coming from the direction of the Sun relative to Earth would be impossible to spot until far too late to do anything (whatever that would be) about it. Also, in the Expanse universe spotting a drive plume among asteroids would be far too common to take note of since asteroid mining is a primary industrial activity of the solar system. What’s more we know there are extra solar objects that come whizzing through the neighborhood occasionally and we have absolutely no way of tracking these.
The situation is as if the Earth is a tiny bug flying through a stadium where mobsters are having a machine gun shoot out with the FBI. It doesn’t really matter if the bug can see the bullets because it can’t do anything about them even if it could. The only reason it hasn’t been hit is down to it’s incredible smallness in relation to the stadium.
@100: Absent some very peculiar (i.e., very-long-period comet or extra-solar) orbits, coming at earth ‘from the direction of the sun’ would be a pretty tricky feat to manage. Magic drives or being willing to wait ten thousand years or more for your impact are ways around it, but are kind of impractical for a weapons system. The only really feasible way to do it is to start out in Earth’s general vicinity to start with (eg. the Moon). And at that point it’s pretty simple to observe things incoming and/or shoot back if you really want to.
John @@@@@ 100
Also, in the Expanse universe spotting a drive plume among asteroids would be far too common to take note of since asteroid mining is a primary industrial activity of the solar system.
Ah, but that’s what computers and statistical analysis are for. (And, depending on how long the drive plume lasts, you can use your observations to estimate how much acceleration/deceleration is going on, and then estimate the mass of what’s being pushed, and in what direction. Which might allow you to identify suspicious cases, and focus more detailed observations on those.)