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150 years into the future, a space faction is in a confrontation with a stronger rival. Our faction is a Kardashev Type I civilization and has a similar technological level to its rival, but the rival is at least 0.1 higher on the Kardashev scale. Both of the confronting factions are defending their systems very well, and they have both realized that there would be extreme difficulties if they tried to siege their rival's systems.

Under these circumstances, our faction decided to send Von Neumann probes to other planetary systems to establish new bases there.

Edit: These probes do not require a supply of raw materials to build the base. (At most, they will bring a small amount of refined material for initial use.) They extract all materials locally.

Edit: The bases will be entirely unmanned. There is no need to send human personnel to the bases once they are built. So we don't have to worry about any passenger ships being detected.

However, the chance of such a probe mission being successful depends on the following factors:

  • For every location where we can launch an interstellar probe, our rival has several positions(planetary systems) within ten light-years distance, from where they can monitor our activities.
  • Our rival has anticipated that we may try to send Von Neumann probes, so they have put a large amount of energy, resources and computational power to track our interstellar launching activities. They have hundreds of thousands of observatories in each of their system, dedicated to watching our activities. These observatories cover all electromagnetic radiations from gamma-ray and X-ray to radio waves and microwaves.
  • Each of our rival's planetary systems can analyze all the data they collected from the observatories within that system in near real-time, but they only have lightspeed communication between their systems (so do we). Despite the slow communication, neither we nor our rival has internal conflicts.
  • The lightest Von Neumann probe we can make weighs 170 tons. We can split our probe into smaller ones that we can launch individually, but this does not decrease their total mass.
  • Our probe should be moving at a speed of at least 0.1c, and must not take more than a few years to accelerate. Otherwise, it would be too slow to make a meaningful impact on the confrontation.
  • Our probes must be able to decelerate when it approaches their target systems. (There are no existing infrastructures in these systems.)
  • If our rival detects our probe during its acceleration, the mission fails. Preferably, our probe should also keep undetected during its interstellar coasting and deceleration.

So the question is: How does our faction launch its Von Neumann probes without its rival detecting them? Is it possible at all? Note that every technology and military operation of the two rivalling factions must work according to the laws of physics we know today.

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    $\begingroup$ @Daron This means that they produce 10 times as much energy. $\endgroup$ May 6 at 15:16
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    $\begingroup$ Like Ireland and Britain. Cool. $\endgroup$
    – Daron
    May 6 at 15:19
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    $\begingroup$ Have you considered a MIRV style strategy? The rival can stop a probe if they detect it - but can they stop thousands of them, even if they can detect them all? What about adding in many decoys that look like the real deal, making it impossible to know which ones are real, requiring a response to all them, as well as making them all arrive at the same time, or staggered in such a way the response force is out of position? $\endgroup$
    – Razmode
    May 6 at 22:15
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    $\begingroup$ You'd also have to come up with a reason why the rival civilization hasn't just swarmed any candidate system with their own von Neumann probes, given that they have a 0.1 kardashev advantage over you, which is massive in absolute terms. $\endgroup$
    – Eugene
    May 7 at 1:51
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    $\begingroup$ @Eugene This. Any viable strategy that our side could use can also be implemented by the rival at a larger scale. $\endgroup$
    – Razmode
    May 7 at 3:14

10 Answers 10

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Antimatter Rocket and Magsail Breaking

Space is huge. A probe is tiny. Use stealth materials for the probe. Let the exhaust go into a direction where there are no enemy observers. Slow down with a magnetic sail. The probe will accelerate rather slowly and will use directional radiators to deal with the drives waste heat. It is probably worth it to build the probe in a Kuiper, Oort or even interstellar location. Either a comet or an asteroid. Deliver the seed package via stealth vessels, which where dropped from torch ships in the inner system, preferably on the far side of the sun from the enemy to throw of their sensors. Sundiving will be hell on the vessels but is should mess with sensors. Alternatively circumplanetary mass drivers on eliptical Orbital Rings or your usual interstellar launch systems could be coopted.

No matter the exact technique, you either have to launch from where they don't look as closely to or use existing systems to launch something that looks normal, but isn't.

Another idea to use Von Neumann probes would be to launch them away from the enemy and to develope strategic depth by colonising yourself out of the situation. You could also order them to turn entire solar systems into weapons. Systems that are far away enough to be more useful in a second strike capacity.

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    $\begingroup$ "Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.” --Douglas Adams $\endgroup$
    – Murphy L.
    May 6 at 19:50
  • $\begingroup$ worldbuilding.stackexchange.com/questions/23313/… Antimatter torch ships are not stealthy... $\endgroup$ May 8 at 16:09
  • $\begingroup$ @GrandPhason ToughSF's stealth in space is possible series has in my opinion a better approach to the issue than Atomic Rockets. I mention that directional stealth has to be used and that one has to accelerate towards an observer with the antimatter rocket. Stealth in space is hard, impractical in most cases and does cost you a lot. But if it were impossible, why is it so hard to map the orbit of every (significant) asteroid? $\endgroup$ May 8 at 22:43
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Mechanically accelerate the probes.

A look into railgun physics and design

Railguns, however, do not have these limitations. Since the force on the projectile is proportional to the current applied, there is no theoretical limit to the amount of force applied to the projectile. This means the maximum range and velocity are without theoretical limit. Of course, due to the presence of atmosphere, gravity, friction, and other forces, limitless force is impossible...

Your people have a very long space railgun fired by a capacitor. They have overcome problems of friction using magnetic levitation and superconducting rails. With the railgun they can accelerate the probes to the desired speed within the railgun. Probes leave the system travelling at speed.

Once en route the probes maneuver as necessary by release of compressed gas jet. This gas is cold, as is all gas released from compression and so has minimal heat signature.

This is outside the range of the OP but also important: slowing down. Excess velocity is shed on arrival via gravity assist with the star, aerobraking and then explosive jettisoning of materials needed for interstellar travel.

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  • $\begingroup$ Nice senior thesis. One quibble on the quote though. The forces on the rails can be quite high, so even with superconducting and magnetic levitation the strength of materials would become important, and maybe a big EMP pulse too. $\endgroup$
    – UVphoton
    May 7 at 0:15
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    $\begingroup$ Space is big so the railgun could be long like a normal railway. $\endgroup$
    – Daron
    May 7 at 6:02
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    $\begingroup$ @UVphoton - I have in my mind that the opposite reaction for a railgun is a force pushing the rails perpendicular to acceleration of the projectile. A cool thing about "space is big" is that it might not be necessary to use maximum acceleration if the rails are very long. The force pushing rails could be less than on terrestrial short railguns. $\endgroup$
    – Willk
    May 7 at 15:14
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    $\begingroup$ @Willk that sounds reasonable. It would be interesting to think about the electromagnetic radiation it might emit when shot, but that would likely be perpendicular to the direction of the shot, so maybe not a problem. $\endgroup$
    – UVphoton
    May 7 at 18:23
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If nano tech is available(?). You covered pretty much all of the bases, so the only thing I can think of is, to deploy small swarms nanites into the systems Ort Cloud / Kuiper Belt. Each swarm is tasked with building components of the Von Neumann probes. and are instructed to build them within existing asteroids / comets etc to shield them from detection. Saturate the system with these swarms. each nanite would be nearly impossible to detect, detection is more probably after construction has started. But if they find one, there's still more somewhere. They will expend a great deal of resources to weed them all out, and there is a high likelihood that some will still get though.

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Distract their sensors

The distance is pretty huge. While at that distance they could detect the immense amount of power needed to accelerate over a hundred tons to 0.1C, that would be much harder if their sensors were distracted.

Build a massive number of lasers and fire them at the solar systems monitoring you. The heat and light will make it much harder to spot the acceleration among the messy signals.

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Mimic the signature of high energy particles

The different planets of interest are bombarded by high energy cosmic rays, gamma ray bursts or other natural phenomenon.

Given the advanced tech, they know where a bright source of natural particles and the statistics of the particles that are leaving the source, so they add in a few more from that direction that have a similar signature.

If the natural source is something like a pulsar, or jet caused by something falling into a black hole or some other high energy process, a few tetra watts giving the probes energy can hide in the high energy background.

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Johhny von Neuman's Flabberghasting Probuliser

enter image description here

What is a Neumann probe made of? I will tell you now my friend -- the probe is made of smaller probes.

Once daddy probe reaches full speed he separates into a cloud of baby probes that scatter over a few hundred million square kilometers. Baby probes are much harder to detect and they can talk to each other to blend in with background particle flows.

When all the baby probes reach the planet they reorganise into a town centre which you use to build Villagers:

enter image description here

The Villagers say Prostagma and start chopping down trees and mining gold and build a colony under your enemy's nose.

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  • $\begingroup$ Sorry, but I still have a question about how did the daddy probe accelerate? It needs at least Terawatts of power, which can be seen easily in nearby planetary systems, and cause the mission to fail. $\endgroup$ May 6 at 15:43
  • $\begingroup$ @VegetableNewMan Even if they see the probe taking off they still don't know where it is going. It will take them years to intercept the probe. By then it has moved somewhere else and is also invisible. $\endgroup$
    – Daron
    May 6 at 15:49
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I suggest laser propulsion for the acceleration phase.

The reason stealth is hard when accelerating is waste heat. Any method of propulsion will produce lots of it, and heat is easy to detect.

However, with laser propulsion the power source is not on the probe but in your solar system, and hence the waste heat will be generated there. Since you're on the Kardashev scale you're already generating many terawatts there all the time, so hopefully the extra power for accelerating the probes will get lost in the noise.

This does require that you can make a perfect mirror, so that all of the incoming laser light will be reflected by the probe (be sure to aim the reflected beam away from the enemy!), with only a negligible amount heating up the probe. That requires some kind of mildly unrealistic future-tech, but maybe you can handwave it with superconducting meta-materials or some such.

On the other hand I don't think you can avoid detection while decelerating, so forget stealth at that point and just decelerate as quickly as possible using whatever you have available. Then you have twenty years or so to build the biggest base you can. (Ten years before you're detected, and then another ten years after that before anything can reach you.)

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Sneak in with other celestial bodies

Detection is one step, identifying another. You want to reduce both as much as possible.

Detection can be difficult to fool. Space is big, but it's also empty. Our current methods can detect a wide range of small objects throughout our solar system! That doesn't mean it's perfect. There's plenty that is too dark and difficult, if not impossible to detect. A comet from deep space can easily blindside us. Recently one was noticed only after it passed us. Your civilisation will be much better at it. Better technologies and more distributed places to detect from will make it much more difficult. Still it is possible to try come in from unexpected angles in the solar system. In addition, be as cool as the space around it, don't let any electromagnetic radiation like light reflect off it and don't move too fast to disrupt gravity even more with the weight.

Even with these measures preventing identification is your best bet. A stealth probe can still stand out. A stealth probe might be identified as a probe just because of it's unusual stealth characteristics. Make it look natural and you'll get much further.

Embed the probe in a natural phenomenon. Though you mught think to embed it in a known comet that comes along every so often, it's weight and characteristics are probably too well known. Unexpected celestial bodies happen frequently though. Throw an ice and rock comet from deep space. The trajectory will take it into a solar system. Because of the sun and gravity of planets it can start breaking up a bit, shedding rock and ice. This can be seen as a dust trail of a comet. Some of it might come close to a planet or moon, crashing down on it.

The probe itself is hidden in a rock and ice shell, making it look like it's just a random iron holding piece of debris. To navigate it must use a 'mechanical' means of propulsion. Simply throwing a part of the rock away while a long distance from a planet will give the right trajectory. This way nothing can identify obvious rocket trails.

The probe uses the rock as a heat shield if going into an atmosphere. Landing is difficult, but maybe the probe is good enough to just crash land. If not, you might have to break the illusion there. So close to the target it might already be past any real scrutiny of the enemy, as they mainly focus further afield. In addition, the planet or moon might give off enough interference.

The only problem then is launching it. 10 light years is a big distance, but soace is so much bigger. Go even further to setup and throw a bunch of rocks in the right direction. It will take a long while, but it's a sure way you can get a van Neuman probe past the enemy.

You might hide it by sending out mining parties in big numbers, mining many asteroids. This is something suggested in RL as well. That means they can move within the detection range, but send out a probe towards a good rock away from the mining operation. Using the miners speed and just detatching the probes can be enough to get them where they need to be. If even that is difficult they can launch the whole rock formation themselves. It'll be dark and hard to spot, and using mechanical propulsion, trowing part of the rock out, they can change direction and come from an unexpected side, making it look independent from the mining operation.

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Flechette Launched Probes and some Deception

Launch a tubular object that contains thousands of tiny Von Neumann probes inside of it. When it enters the system, shoot the probes (inactivated) in a mist towards the target area, using electromagnetism so there are no emissions or heat signatures. Then, the enemy will certainly have captured the launcher, wait a few weeks and activate the probes to begin clumping together. Set them to work on an uninhabited celestial object, and bam, you have your ready made base. Or you could just set something up like the Star Forge from Star Wars Legends, ready to deploy countermeasures, in the system, taking materials from the star.

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Contact one of the primitive civilizations in their sector.

Your civilization resides on Alpha Centauri, a hub of learning and reason. But just a few light years away is Earth, a backward and benighted planet that may never reach a Cardassian level of civilization, let alone any other kind. But as a Centaurian, you're too civilized to squash vermin; you leave the Earthlings to their own devices.

The Earthlings have picked up a signal with designs for a small, compact power plant, just 150 tons, which promises limitless energy to their planet. Needless to say, the relevant gun-gang keep this data very tightly secret on a single continent, one unfortunately not well monitored by Centaurian agents. All the Earthlings need to do is build it, allow it to burrow deep into the geothermal center of their planet ... and a few years later, most of the planet's mass will spray out as an unstoppable tide of trillions of killer robots ready to wipe Centauri from the face of the cosmos.

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  • $\begingroup$ Sorry, I didn't make it clear that, in my setting, humans have not found any alien civilization. The conflict is sort of a "civil war" of human civilization. (We should probably call them "descents of human civilization," because AIs/posthumans are in charge of strategy, R&D and industry on both sides of the confrontation.) $\endgroup$ May 7 at 14:50

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