How can I launch a projectile to hit something in orbit, using only geological structures and power sources?

Question

As an ancient organism whom currently occupies a large chunk of a planet beneath the surface, I have a pesky issue with an invasive species. These humans have decided to colonize my home, mistaking it for an uninhabited Earth-like planet. There aren't that many of them (yet), but I have a big problem with an orbiting station they deployed that keeps an eye on most of the planet. I want to keep my presence hidden, at least for now, and their ability to see a good chunk of the planet with optical cameras makes it tough for me to operate openly.

After careful observation, I've learned there's a critical weakness in its design: there's a communications "blister" on the outside of the station that allows it to send back what it's seeing, and also allows it to communicate with the rest of the galaxy. I also know that this planet is very remote by their standards; it would take months for someone to make it here or to the next system. As an added bonus, they don't have the ability to fix it themselves, and as far as I can tell this station is fully automated and uninhabited.

My plan is to manipulate the geology of the planet to create a crude gun that can hit this weak spot with a dense rock, ideally making it look like a 'nautral phenomenon'. Let's also say I had millennia to anticipate the need to defend myself, making it just another curious part of the surface before they even got here.

So, I need to make a 'cannon' that:

• Looks like a natural geological formation
• 'Powered' only by what naturally occurs in the crust of a planet (ex. lava, geothermal pressure, etc.)
• Fires a projectile that can survive leaving the atmosphere
• Has enough accuracy to hit a target that's no more than a few meters across
• Ideally can launch my payload when nobody is looking (i.e. the station can't see me), allowing me to make it look like a stray asteroid
• Allows most of the planet to remain inhabitable

It's fine if it's loud; I can always make some rumbling happen in advance and get the colonists accustomed to it. However, I don't want the result to outright kill them or maim them; it would cause less panic if there are no casualties or injuries. I need a month or two to get rid of them properly, and the less they suspect, the better.

Answer 1

It doesn't seem to be possible using "normal" geology. You'd need a supervolcano to attain the required energies, and "piloting" one with the required precision doesn't look doable.

You need to score a direct hit; getting in orbit isn't enough, since any station would have ACS thrusters and be able to both detect a coorbiting incoming missile, and avoid it.

You could perhaps build yourself a single-shot, nuclear long-gun, using a fizzle bomb design (this happens in at least one story that I know of). Basically, you build an inclined well with lightly enriched uranium, fill it with lithium deuteride, and have it explode. Can you do all these things? If you can manipulate magma, then perhaps.

"Natural" reactors have occurred on Earth; of course they never had the least chance of exploding. But if you disseminated the components elsewhere, too, instead of just in the one place, it could be believed to be "just the way the planet is".

The problem will be in accurately guiding the real projectile (you'll need a large number of decoys, otherwise the chances of one single projectile killing exactly the communication blister on an orbiting space station being dismissed as "Aw, tough luck" will be nil). You'll probably have to devise some way of guiding the projectile using fins and single-use steam reaction jets, which also mean controlling it somehow at a distance - can you fork a nonsentient, small scale replica of yourself capable of doing the job and surviving launch? Also, you can't hit the blister with the main projectile - that will be analyzed, so it has to be a normal rock, a piece of the main projectile, while the rest has to lose itself in space or burn at reentry, to leave less traces.

(The above actually solves the accuracy problem somewhat: the controlled vehicle gets shot into orbit, "close enough" to the station. Once it is close enough, it fakes breaking into several fragments - one of which is aimed at the station. At that distance and in microgravity, aiming will be much easier and the shot will require a lot less energy. The launch vehicle doesn't need to be accurate at all).

misdirection - camouflaging

Item 1 on the list is to carefully disseminate volcanoes with very high quantities of weakly enriched radioactive ore. Then, one or two volcanoes are replaced by craters with aging and weathering signs indicating large scale nuclear explosions having taken place in the last fifty thousand years. This, of course, implies precise control of the isotopic composition of rock, as well as the capability of disassembling and reassembling it.

Also, this needs must have taken place before any extensive survey of the planet has been performed, of course; a 50KY old crater that wasn't there six months before would be a dead giveaway.

But if you manage to pull this off, Earth scientists investigating the planet will begin wondering why anyone might have targeted volcanoes with rudimental nuclear devices so many years ago. Then, someone else will develop a theory that some unknown mechanism, somehow, drives radioactive ores to accumulate inside volcanoes' calderas. The conclusion would be immediate - in the right circumstances, either a normal but unseasonable eruption, a "fizzle" eruption, or a much rarer semiaborted nuclear explosion would take place.

From there, someone is bound to wonder whether any such explosion might be brewing just now - and most anyone else will laugh it off. Finding ancient tephra at large distances from the "ground zero" point of origin will make theorists suspect that the geometry of the explosion allow projectiles to reach orbit.

This, however, has a serious drawback - radioactive ore concentration is likely to make the planet really appetizing, and the underlying organism is unlikely to realize that. Now that I come to think of it, this whole plan has one other really weak spot - how is the organism going to know that a fizzle bomb is possible, let alone how to build one without having it detonate prematurely?

(Unless it spent countless aeons researching all kinds of weird science, possibly out of boredom...?)

Answer 2

I think there's a misunderstanding about space going on here. According to the title, you want to get an object into orbit with a cannon of some kind. This can't be done; every orbit includes the point at which delta-V was last spent. If you're launching from some kind of cannon, that means the orbit intersects with that cannon and probably the ground. Rockets in real life get around this by burning their engines again once they're way above the atmosphere.

But you don't need to get an object into orbit to hit something in orbit. You just need to reach the same altitude, which is much much easier. I think a volcano is your best bet; a supervolcanic eruption might be able to launch a rock into space. As I said, not into orbit though.

Answer 3

You may choose a different scenario.

Start with a supervolcano eruption. No, not one to hit the space station. One that will throw enough material into the atmosphere that it blocks most if not all radio-magnetic transmission. The dust in the atmosphere will last for months, even years, so you have plenty of time to get rid of humans while they are cut from their communication and then being invisible from the orbit prepare something to destroy the station in not-so-natural way. Another benefit is that this can change your planet's climate in a way that can itself be deadly at least to some level to the intruders.

Answer 4

Not a chance.

1. You need to give the projectile all of the energy it needs in a very brief space of time (the time it needs to clear the volcano, to mention an example). That is an awesome amount of power. Remember that our rockets carry their fuel with them and burn it as they raise, it is highly inefficient but the alternative method would destroy the rocket at launch.

   You need some sturdy material for your projectile, and worse, you need to reinforce a lot the structure of any volcano, geyser, whatever that you want to use as your energy source. And not only the "cannon", but all around it, because you cannot allow that pressure that you need to build to escape by blowing some other part of the volcano.

   Mind you, completing engineering works of this scale in an active volcano is not an easy task, and likely to be observed by the ship. Overcoming this hurdle is a really unbelievable feat.

2. Precision. The worst one. You are sending an unguided projectile towards a minuscule target in a big sky. Any mistake in the measurements of the target orbit, your projectile weight and aerodinamics, your energy source power, the local weather, and you have nothing but a piece of rock wandering around your planet, almost harmless. Chaos theory says that you will fail.

3. Countermesures. It is difficult to believe that a spaceship by an advanced spacefaring civilization will not have some means of detecting and avoiding a meteorite strike (at the very least just changing its speed to avoid the crash).

Answer 5

Can you manipulate your local equivalent of the Van Allen belts to focus solar radiation and fry the satellite's electronics? Gets rid of the off-world communications and the video link without actually destroying the satellite..

Answer 6

Physics is against you for a number of reasons. To get an exact answer of how badly, you need to define how high the orbit of the spy station is, thus how high your projectile needs to get. The problem, though, is this incredibly approximated math:

1. Your projectile needs to survive the atmosphere and do damage. Let's assume a 8kg iron sphere. An ordinary cannonball, basically.
2. You need to get the thing sub-orbital, for an autonomous sat let's guess something on the order of 2500m/s at release.
3. If my late night math is right, we can translate that via momentum to needing to impart 20,000 newtons of force. In that direction.
4. Converting to kinetic energy, that should be 28kJ?
5. Let's assume you're getting 25% of your released energy converted to useful force, so 80,000 newtons raw.
6. Juggle a few numbers, make some assumptions about losses, and guess you need an explosive force of 200-300kJ under optimistic conditions.
7. Look for an equivalent energy and work out that your energy budget is likely off by an order of magnitude.

Ok, maybe the math is my problem too. Honestly, I don't know what kind of losses you'd get from trying to to make a cannonball travel at more than mach 7. I also don't know how to estimate the extra force needed to compress a propellant gas to the point that it imparts enough force. I don't even know if a cannonball would survive, a meteor with these specs would survive re-entry but for launching the curves get reversed. Compression heating? Ablation effects? Hypersonic aerodynamics near the ground? *shrug*

Anyway, if you want to get that cannonball to hit something in orbit your issue is that you end up needing an explosive force measured in metric tons of TNT, and consequently your "barrel" and projectile has to withstand that while the force is transmitted. You need to concentrate that force too, since it's pressure, the more (chamber) surface area subjected to the force the more energy is needed to get the same acceleration. If you want a better number you'd need a much better physicist than I. Actually I'm hoping someone competent can tell me how many orders of magnitude off I am with those numbers.

As a final note, I'm using explosive forces here because achieving the same thing through pressure build up is far less practical, if only because concentrating that force and making a working release mechanism adds lots of problems while increasing mechanical losses. Volcanoes and earthquakes can easily build up and release enough energy to put something in orbit but I'd say it's impossible direct/concentrate that energy into a projectile. Surface area is your enemy with any pressure system.

...

What, you want to know how I'd solve the problem? Blow a few big volcanoes and put enough ash in the atmosphere to obscure the surveillance while you arrange a more permanent elimination of both people and tech. As a bonus, the transmitted footage will send a "really unpleasant place to live" message to whoever views it. Sadly it's probably too much to hope that you can hit their settlement with the lava, but a tsunami would do the job without looking too suspicious to a remote observer.

Answer 7

Assuming an earth-like planet...

Satellites are not meant to land

Strategic heating of the atmosphere combined with a well placed hurricane or five and you can raise the atmosphere to the point where if they aren't watching they might accidentally enter the atmosphere, burn up and crash. As is the ISS actually experiences significant atmospheric drag ramping this up a bit will significantly lessen the life span of satellites in low orbit.

The Good

Changes to surface albedo, minor core cooling, tropospheric disturbances cause no long term losses of mass. It looks completely like a fluke.

The Bad

Anything designed for interstellar travel shouldn't have problem station keeping indefinitely.

The Fix

The observation post was intended to be temporary. It was put in an orbit that would only last 50 years before atmospheric entry. Low so that it could cover more ground faster, but not so low it would need station keeping fuel and thrusters.

Radiation Squeeze

The hypothetical planet has a magnetic field which blocks incoming radiation and ends up trapping it in high orbit much like our Van Allen Radiation belts. These ions are mostly free protons and electrons in belts segregated by charge. There are also limited amounts of positrons and anti-electrons as well as ionized helium floating around. The particles can destroy equipment and will certainly disrupt electronics. If you adjust the magnetic field of the planet to bring the belt into path of the satellite it may degrade its performance to the point where it no longer functions.

The Good

No mass lost. The South Atlantic Anomaly (where the belt reaches 200km above the surface as opposed to 2000km) is a thing so this looks like an unhappy planet to be.

The Bad

Interplanetary craft must deal with solar flares which can be far worse.

The Fix

Protecting the electronics from radiation surges often means shutting them down. If the shutdown needs to be longer than expected or more often than expected the station may be damaged anyway. Time this with a strong solar flare and you might be able to take it down.

Both at once

The planet is looking nice and hospitable. Strong spherical magnetic field nicely aligned with it smooth regular surface. Even flow of a liquid core. It's a relatively cool planet without strong temperature gradients. The sun is entering a maximum of activity but it shouldn't matter, everything is okay inside of the planets magnetic belt. Geologists are reporting that a large glacial lake is about to rupture some time in the next thousand years and it should be a spectacular display.

The earthen dam gave way far earlier than expected but such events have never been observed live. The biggest change and a large layer of fresh water on top of the planets largest ocean. In other notes there is a small magnetic anomaly forming at mid latitudes. There is no projected change to the magnetosphere at this time, but watch for variations in local declination.

Meteorology reports that turbidity is increasing and sea surface temperature is rising. A small dust storm is forming in the basin left by the drained glacier. They expect that a hurricane will be forming in the next 3-5 days and rapidly move to mid latitudes. The first one observed on this planet.

The hurricane has formed. Meteorology is going wild. There hasn't been a storm this big recorded ever on earth. Solar flare predicted to impact in 2 days Observation station going into protective shut down mode. The magnetic anomaly has strengthened. It looks like we are at the beginning of a shift of the planets magnetic poles.

The solar flare was stronger and faster than expected the system only got partially shut down and there are some data corruption issues. The information we are getting is only intermittent. We are attempting a reboot from the ground station.

More data is in coming in now. Full system integrity checks take two hours to complete. There is some sort of radiation anomaly occurring forcing a reset every 93 minutes. Atmospheric craft report the hurricane has only intensified.

Communication has been fully restored with with observation station. It seems the planets Van Allen belts have reoriented themselves with the magnetic poles shift. In order to maintain the observation stations integrity we need to shut it down when passing through the anomaly. Unfortunately, the anomaly occurs near apogee. We are trying to schedule a station keeping maneuver but the orbit is decaying far faster then predicted.

Answer 8

Build millions of mirrors reflecting sunlight at it.

Frame-challenge: it doesn't have to be a projectile, you just need to destroy the blister.

Assumption: you have line of sight, the blister is not on the "far side" of the station.

Build several tiny surface formations reflecting sunlight. They can look natural, made of glass, sapphire or other perfectly natural, reasonably reflective material. Mixing and matching allowed. None has to be very efficient (glass does pass most of the light through), you can compensate by a 99% waste by building 100x more.

Aiming is a challenge, but, if you can perceive the station in such detail while it goes around the planet at distance and speed, well, these are the same problems you're already solving. I don't know enough about your nature to say how, but you certainly have the equivalent of a tracking telescope. What remains is, do you have enough cognition to do it millions of times over at the same time?

The effect will be equivalent to a death ray, the blister will melt. They'll be suspicious, but they'll never learn the truth, you don't detect a distributed mirror like this unless you're looking for it. They'll blame design and construction, and suspect sabotage from their own before they suspect you. You're just too unique for them to expect.

Answer 9

On earth, the most common natural looking formation that can shoot rocks is a volcano. Yes, we know that a volcano shoots rocks high above the earth but not outside the atmosphere. So we can just modify the volcano to make the crater thinner, small and more round so that there is perfection in the accuracy. For launching a rock into the orbit we need the rock to be in an aerodynamic shape and have a highly flammable material on the bottom of the rock which can be triggered by the hot lava. So we have a volcano shooting out a rock missile into orbit. But we still won't have the right pressure so we will try to pressurize the volcano from within. We can use a system that lets lava come in but not out so that we have enough pressure and we can use a big door that will be opened when the pressure is right.

This might work but the accuracy will not be so good. So you can just launch it in such an orbit that it will crash with the station in the orbit and not directly hit it.

Answer 10

1. If you want to destroy their station, set a cloud of gas on the orbit (if it's not very high). You will get the most part of your gas back later. Do it several times while the station is on the other side of the planet. The speed of the station will decrease and it will get down. It will get damaged at first. Repeat while they not repair it.

2. Exotic things like atmospheric gas laser, microgravity resonance etc are not practical.

3. Use your strength. Yours is time (on geological scales) Theirs is money.

   • Methodically destroy every habitat ship landing. They will find correlation very soon.

   • They will use robots. Destroy power plants.

   • They will use nano-robots. Destroy stocks and launch sites to prevent them stealing your resources.

   • They will use molecule-level robots to set you to a gray goo. Develop this technology

4. Those monsters will come back. They will set more than 1 station quite far from the planet. So get ready. The maximum reasonable impact is asteroids they will set on you. You are not scared of atomic bombs, aren't you? Well, they would set a mini black hole or something like this to finally get energy from you but I cannot get a solution for this case now.

5. Use energy of your star to get out of the habitat zone in your planet system. May be it would be even profitable for you, you just did not think about it. It will take a lot of time so start right now. If you use some space inside the planet it probably is not critical for you.

6. Split and diversify your bodies for different conditions, impacts and possibilities. This incident will be start of your infinite expansion to the space. They are split by their greed. You will get unite with the new infinite goal that will transform you. Set yourself total on this. They got here to wake up you. This is the aim of any real contact. Get their passion and apply with your planet-wide scale. Make all possible for this, not to get rid of that piece of shit on the orbit.

@Chris Bradshaw presented an elegant solution for big distances, but the Juno Radiation Vault mission proves that even today's shielded electronics can work some years even in radiation belts of Jupiter, which are more intensive than ones for an Earth-like planet

Probably the author will have a strike on the ground. He definitely will win the first one and will have some time to another. Any solutions to rise costs of taking ownership on the planet to unacceptable, including terraforming to temperature and atmospheric conditions unacceptable for invaders. Like on Venus. Oh, mankind is a big pain in the ass.

But wait a minute. "These humans have decided to colonize my home, mistaking it for an uninhabited Earth-like planet."

Are we talking about Earth? Because our thoughts more likely are inspired by our environment, not by something else like Solaris in hundreds of light years somewhere.

The space station is the opposite side for the action. As the center of crazy mind like a Death Star. They think they are only rational, legitimate, self-consistent and independent in all the space around.

Answer 11

OP you specified earth-like but this is usually used to define atmosphere makeup and temperatures - what about a smaller planet (lower escape velocity), natural geologic formations that are much taller than the ones on earth due to tectonic activity? One could create something that is essentially a space-sling from a spot that is much higher altitude and solves most of your dilemmas. People on the ground might not even notice that there is something in the slingshot, which would be moving at a much higher velocity and could be released with pinpoint accuracy during the normal rotation of the earth.

Hell, you could have some kind of natural vine, native to the planet, that 'unintentionally' created a space elevator that the parasites utilized to ship materials to and from the station at one time. Then one day, when the planet's spin managed to line up with the station, suddenly let out a lot of extra line, swinging the end of the elevator in to the blister and destroying it, then retracting it immediately. No muss, no fuss.

Answer 12

Have you considered putting the orbiting station in a low orbit that needs occasional re-boosting to stop it de-orbiting? Spy satellites are often in low orbits to get the best detail in their pictures. The International Space Station would crash after about 15 months if abandoned.

If you can knock out the communications and any automated re-boosting mechanism, the satellite would burn up and take all the evidence of what happened with it so nobody can tell the difference between a software bug, a manufacturing defect, and a meteoroid strike.

Then if the gun from LSerni's great answer could fire something as radioactive as the heart of the Chernobyl sarcophagus, you could claim it only needed to get within a few tens of meters. All the humans see is their satellite has stopped responding and they can't tell why, and it burns up on re-entry before anyone can get there to investigate.

Answer 13

1. What is the most energetic phenomenon a planet might have access to? I here assert this to be impacts from extraplanetary objects.

2. Could an impact from an extraplanetary object propel material off of the impacted planet fast enough to escape the gravity well of the planet? Yes - a meteorite loosed from Mars was in the news some years ago as potentially containing fossil microbes. An ancient rock blasted loose from Earth was recently discovered in a collection of moon rocks.

3. Could rocks blasted loose from the planet by an impactor disrupt an orbiting satellite? I think yes. Clearly a rock moving fast enough to reach the moon could do some damage if it hit something en route. I would assume this moon-destined rock was one of many and that the impact would produce a shotgun-like giant cloud of rock.

4. Could a planetary super creature induce an impactor to hit? This is where it gets tricky. Let us assume the creature can manipulate the planet's magnetic field by altering magmatic flow. A magnetic field can induce a current within a conductor moving within it; metal asteroids / meteors would be conductors. The current within the moving asteroid generates heat. The energy to create this heat is taken from the kinetic energy of the moving asteroid thru the magnetic field, thus slowing the asteroid. This slowing /heating would occur for a meteor moving perpendicular to lines of force, not parallel. http://adsabs.harvard.edu/full/1946PA.....54..482R

Thus by manipulating magnetic fields, the creature could steer a meteor to some degree, possibly inducing a meteor to hit in such a way as to launch a cloud of rock at escape velocity, obliterating the satellite.

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This induced mega impact is kind of a bold maneuver given the creature calls the planet home. But if it can steer nearby asteroids to some degree, why not steer a small one into the spacecraft and leave out the massive impact part? Even this would take great effort on the part of the creature as well as knowledge of asteroids in the vicinity (which it might perceive, at least periodically, if it were an electromagnetic creature).

It might miss the first several times it tried. In fact for the story I like the idea of it missing every time but then realizing that the alteration of the magnetic field actually was greatly altering the stream of charged particles from the solar wind. Rather than whack the satellite with a fast moving piece of metal, it rearranges the planet's field so charged particles are funneled down onto the satellite, producing a quiet death from a thousand cuts.

Answer 14

Blow up a supervolcano, like when Krakatoa and others dusted the stratosphere and caused their Little Ice Ages... in your case, you might want a plume of sand and stuff to reach even higher, and the pesky newcomers might consider it a quirk of the unexplored new planet. The cloud of sand, ice particles or whatever else small and hard, roaming at orbital speeds at the height of that station would probably not even be detectable until too late - that is when they make it look like cheese. Maybe it will not even look much like cheese at first sight, when the particles are small, but breaking the atmosphere (cooling) and tearing (and short-circuiting) the cables in the station does the job and looks like a natural accident. Also you don't really need to hit just that radio blister, the whole station would do, and not a very good precision to make the hit (a fast dust cloud can be bigger than the station).

Note: This was the sort of tech discussed for the star wars between Earth-bound superpowers, to take out satellite constellations by bringing up a cistern of water and blowing it up - after a few rotations and dealing the desired effect, the icicles would sublimate away or fall and burn in the atmosphere, and not contaminate the orbit for later launches.