It is stated multiple times across the article that the probe would need a means of changing is trajectory, but not even a hint of idea how that could possibly be done is given. So the most important and blocking aspect of the mission is simply skimmed over, and the rest of it is built upon this omission as if it was something trivial to come up with.
Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
Since momentum is conserved, why not just have a 2 of the 1 g probes strapped to each other with a spring in between. When you need a course correction at 100 AU out (or whatever). The probes calculate how much of a correction is needed, adjusts a screw that tightens or loosens tension on the spring, reorients itself appropriately with a reaction wheel, then the two probes are released from each other, begin pushed apart with the spring. One probe gets the trajectory correction it needs, and the other gets further off course. Maybe with some gravity assists with nearby objects.
Isn’t that basically how a rocket works? Throw stuff out one side to get the thing on the other side moving. Not sure how this would compare to a rocket engine with hyperbolic fuel.
No. Very much no. The spring system would literally throw away half the mass of the craft for, maybe, a 10m/s delta. Fireworks would be more efficient. A pitching machine attached to a huge pile of baseballs would be more efficient (ie the baseballs could be thrown faster).
You can think of the hypergolic fuel as a type of spring. The chemical energy stored in the bonds of the fuel is what pushes the fuel products apart when it reacts. This is what pressure is, it's nothing more than KE of molecules.
The 'spring action' of fuel is very good because there's a lot more energy (per unit mass) stored in the bonds. Orders of magnitude more than a mechanical spring.
Because the specific impulse of the spring is negligible when you’re moving at 1/10c and why would they send a 1g probe if they could accelerate 100kg to that speed? Why do you suppose doubling the weight would be free instead of making the system infeasible?
What would the "screw" push off of? That rotational force would need to go somewhere or be corrected, else the probes would just rotate. I guess a gyroscope could do that, but what you're describing just sounds... very roundabout, and in terms of force, a few kilos of propellant would have the same effect.
This is infeasible for the reason other have mentioned about specific impulse. But surely you can imagine a set of parallel boards with a coil spring between them and a set of cylindrical guide rods to prevent relative rotation between the boards. A motor fixed to one board turns a screw that engages with threaded nut on the other board, mounted on a thrust bearing, and guide bushing that allows a linear movement, but disallows the rotation degree of freedom. Think of the lead screw on a milling machine or lathe.
It's not skimmed over, they cover it near the end in the "Requirements and challenges" section:
> The most challenging phase of the mission may be related to how the nanocraft can transfer from an unbound to a bound orbit and start orbiting around the compact object. All possible solutions should be considered carefully. In the case the transfer is not possible, we may redesign the mission to perform the scientific tests when the nanocraft passes close to the black hole. For example, when the nanocraft is close to the black hole, it may separate into a mother-nanocraft (with a wafer and sail) and a number of small nanocrafts (without sails). The nanocrafts could communicate with each other by exchanging electromagnetic signals. The mother-nanocraft could compare the trajectories of the small nanocrafts to those expected in a Kerr spacetime and send the data to Earth.
Light sales can theoretically be used to not only accelerate away from Earth, but also decelerate at the end of an interstellar journey (see Robert L Forward's work). The practicality of that is another matter.
There’s a really straightforward way to avoid a parabolic trajectory with a black hole. But data retrieval gets a bit difficult.
More seriously, it floors me how often and consistently people forget that the accretion disk is essentially a partial accelerator and crossing or entering it will probably pulverize you to radioactive dust. Possibly before you could hit the event horizon.
> Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years. That also seems incompatible with the weight constraint.
>I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years.
Just spit-balling here. Send out the first batch of probes and then 5 years later send another batch of probes. The first batch of probes does their surveying for 5 years, when the later batch of probes start arriving. The data is uploaded to the late-comers, who aren't on an intercept course. Instead they are on a trajectory that causes them to swing around the black hole, and head on back to earth with the data.
> Send out the first batch of probes and then 5 years later send another batch of probes.
What's the separation there, at 0.33 lightspeed? 1.65 light years? Wikipedia says Voyager is 168.35 AU away, and Google says that's 0.00266 light years. Voyager has 23-watt radio focused by a 3.7m dish and its signals are received by a 70-meter dish on Earth.
So you're talking about a 1g spacecraft signaling another 1g spacecraft over 620 times the distance to Voyager, without any of the beefy equipment that exists on both ends of the Voyager link.
Hmm. Seems like you are you multiplying 5 years by 33% of light speed to come up with 1.65 light years? I apparently didn't explain well enough. The 5 years is for the first batch of probes to gather data over an extended period of time (while in orbit around the black hole). The second set of probes is just a roundtrip "fly-by" to collect the data from the first probes and return it to earth. No reason that the return trip probes would have to be very far from the data gathering probes. Maybe you can't orbit close enough to the black hole at these speeds without getting too close to the accretion disk?
Even then, I think you're going to have massive distances between tiny probes moving very fast relative to each other. Maybe not 1.65 light years, but communication over Voyager's 0.00266 light years or even a much smaller distance (e.g. Earth to moon) seems insurmountable for two 1g probes.
Also, the probes are in deep space, right? No solar power. Where are they going to get the energy?
>I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years.
Split particle pairs. We just need to repeal the no cloning theorem, maybe if we promise to not use it for FTL communication the legislators would go for it.
People don't realise this, but you can steer perfectly fine with a solar sail. That's because photons transfer momentum not just when they hit the sail, but also when they are emitted after reflection. So just by turning the sail at an angle, you can create a force in any direction perpendicular to the velocity vector. Using a two sail system, you can even accelerate and slow down along a single beam path. So you could theoretically travel to mars with a constant acceleration/deceleration phase (like a flip-and-burn in the Expanse) using only one beam emitter on earth.
Infinite time since we have no realistic way of making such a laser at this time - and anyone trying it is likely to get nuked before they finish their massive death ray.
Depends entirely on the power output of the laser, the dispersal length and the size, weight and reflectivity of the sail. Since we are already talking about imaginary technology, any answer between "slower than current chemical rockets" and "some significant fraction of the speed of light" could be valid.
You explicitly asked for unknown materials. Because there is no known material because such a laser does not exist. We have solar sail prototypes that were using the sun's light, but even they are far off in terms of size/weight ratio and reflectivity.
No, I didn't ask for unknown materials; lasers can be built with known materials. Also solar sails aren't lightsails, and the topic here is lightsails.
> So the most important and blocking aspect of the mission
Idk, i think the fact they are using statistical arguments that there should be a nearby black hole, but haven't actually found any or have any idea where they are, is pretty blocking.
"steering" is a word that can lead to confusion because it leverages the intuition that we have with our ground vehicles.
A change in direction in space requires accelerating the vehicle in some direction, the effect of which is just simple vector addition of the velocity vector of the vehicle.
So if you are going with a huge velocity in one direction and you want to change direction significantly in another direction you have to change velocity (accelerate) a lot in order for the combined vectors to produce a significantly different final velocity vector
Isn't Relativistic time dilation a problem for this idea? To the probe, the trip is only a few centuries but to us on Earth, millions of years. Maybe 0.1c isn't enough to cause this to be a huge problem but I think it is. Perhaps one of you Einstein enjoyers can tell us for certain.
Time dilation is 1/sqrt(1 - (v/c)^2). So at 0.1c that’s 0.5%. Certainly much higher than any human has ever experienced! But not exactly gonna change 100y to 100,000,000y.
No need to be snarky and especially not here re basic science. Time dilation happens exponentially, ie with 0.5c you don't have time going 1/2 slower, rather a miniscule amount. Once you keep approaching speed of light closer and closer, all things go extreme (time, energy required, mass and so on).
Seems like first we need to get out of the gravity well...
Then we need to cure ageing to give people skin in these games...
Then we need to crack FTL or find a way to cryo-sleep or we end up with dystopian science fiction ships of the damned...
What’s be super cool is discovering a! asteroid mass primordial black hole in our solar system. No epic interstellar flight needed.
It would be super hard to detect though. We’d have to spot it by gravitational effects or get very lucky and notice lensing. It would emit nothing unless it happened to be nomming on some matter, and even then it’d be so small that the signal would be weak.
I read somewhere that a black hole with the mass of the moon will absorb about as much cosmic radiation as it emits Hawking radiation. This is a fine line between "the black hole disappears before we can examine it" and "oops, we got eaten by a black hole".
Hey, its not like an analog of "Yeah, lets just throw some more mass at the newly-forming black hole in our neighbourhood", said every human that has ever thrown things into the fire, forever ..
Black holes aren't cosmic vacuum cleaners. They're just super super super compact objects.
I've actually posted this a few times:
If you suddenly transformed the Moon into a black hole of the same mass, it would continue to orbit the Earth in the same spot. It wouldn't suck up the Earth or anything. The ocean tides would continue as normal under the influence of the black-hole-moon's gravity, which would be the same if it was orbiting at the same distance. You wouldn't see a moon in the sky, but if you focused a good telescope on where it was you'd see gravitational lensing. It would be a little smaller than a BB.
If it's in a stable orbit in the solar system, it wouldn't be able to "eat" us. Black holes gravitate exactly the same as any other mass, so it would have the same gravitational effect on Earth as any object if the same mass.
What makes black holes special is that you can get much close to their center of mass than you can with normal objects. When you're that close - inside the radius that a normal density object of that mass would have - then you experience gravity at a much higher strength than normal.
Put another way, even if our Moon was a black hole with the same mass, very little would change except that it would no longer reflect sunlight. Ocean tides on Earth would remain the same. You wouldn't want to try to land on it though...
There was a movie where Moon was a hi-tech 'megastructure' with a white dwarf inside. I wonder if it would be theoretically possible to set up such a mini-dyson sphere around a mini-blackhole.
A black hole, or neutron star, would make much more sense in that scenario than a white dwarf.
A white dwarf smaller than the moon seems unlikely, if not impossible. If it were that small, unless it was in the (fast) process of collapsing to a neutron star, it wouldn't have enough mass to remain that compact.
A neutron star or black hole would work fine, because both can easily have radii much smaller than the Moon's.
> “There are just so many things wrong with [the idea of a white dwarf inside the moon],” says Romer. “Now, a white dwarf is a very compact object. But, you know — people have heard of neutron stars — neutron stars are ultra-compact objects, they’re a few tens of kilometres across. White dwarfs are actually about the size of a normal star.”
You can come up with scenarios where white dwarfs are much smaller than a star, but smaller than the Moon is iffy at best.
As for the Dyson sphere idea, the biggest problem with it in this scaled-down scenario is stability. You can't exactly support it with struts, or something.
On that subject, I highly recommend the video "dyson spheres are a joke": https://www.youtube.com/watch?v=fLzEX1TPBFM , by astrophysicist Angela Collier. But you need to either watch all 53 minutes, or skip to near the end, to find out just how literal the title is.
If you set it up at the right radius it would have 1g gravity at the surface, like a little mini-world. It wouldn't be able to hold an atmosphere though, so it would have to have pressurized buildings on it.
Would it? I would've thought there is enough dust in the solar system that it would create constant xray emissions. Even if it's faint, it would stick out like a sore thumb on super sensitive xray telescopes.
An asteroid-mass black hole is around a micron across. It's not going to be nomming on much because the matter distribution inside the solar system isn't that dense.
Any tiny black hole born in the big bang would either have evaporated (if Hawking was right...) or would have grown much larger by now.
Even a moon-mass black hole (0.1mm) wouldn't be eating much, although its gravitational effects would be much more obvious.
If it was asteroid mass, wouldn't it have the same gravitational effect of an asteroid itself? Plus, someone else mentioned it'd be like a micron across, which if my pop-sci understanding of these things is correct, it'd disappear in a poof of hawking radiation.
It would have the same mass, and it would be tiny -- like the size of a hydrogen or helium atom.
AFAIK an asteroid mass black hole wouldn't evaporate yet since the CMB is still warmer than its Hawking temperature. Very tiny black holes would have evaporated earlier in the universe. A black hole evaporates when its Hawking temperature exceeds the ambient temperature.
I remember reading somewhere that it's possible for such a black hole to get captured by an asteroid (or vice versa, I guess), and happily live inside a rock, slowly orbiting inside the asteroid, sucking up atoms here and there.
It would be detectable as an asteroid that's twice as dense as it should be.
We wouldn't have to get lucky if it was on the last stages of evaporating. If it has reached a mass of about a billion kg it would be shining plenty bright to detect, and would only have a few thousand years to live before destroying most life on Earth with gamma radiation.
Related:
"Project Solar Sail" by Arthur-Clarke and others, is a good anthology (stories, essays and illustrations) about the new Age of Sailing (Sailing in Space)via lightships and solar sails.
How do you stop if your solar sail has you going near light speed? Or does it strand you halfway between stars in the doldrums where the force on both sides of your sail equals out from two stars?
You don't stop this type of craft, it's strictly accelerate and coast type of thing.
Also note that "solar sail" is a bit misleading, the (now apparently dead) Breakthrough Starshot design was a big reflector "sail" in space and very many lasers on Earth to power it, it's not actually driven by a stellar wind directly.
This suggests ejecting a secondary mirror in front of the craft to reflect light to brake the original craft: https://arxiv.org/pdf/1604.01356:
"...or by ejecting a reflector that is then used as a braking system (similar to thrust reversal on jets) but this only works if the payload is still within illumination range of the primary laser system"
Solar sails aren't powered by solar wind but by light reflecting off like the probe. But the probe would be powered by laser so not really "solar" sail. Light sail is the generic term.
But if you're going near light speed, the light / particles would be too faint to have any significant effect until you get very close. You'd basically just fly backwards straight into it. Unless your sail is very large and/or the total mass is very small.
I don't think we can just go near speed of light. Even hard vacuum out there contains particles. Heliosphere is chock full of them, then Oort cloud has stuff way bigger than that (or any probe), even if sparsely spread out. Then there is cosmic stuff outside, as Voyager found out.
Getting hit by some random molecule when orbiting Earth or just travelling say 30,000 kmh is one thing. Getting hit by swarms of molecules with say 0.5c can be catastrophic to the material. Now imagine wading through some space dust cloud, or even plasma cloud (ie remnant of some bygone supernova).
Star trek had shields, and for good reasons. Super strong magnetic field may divert some charged particle, but helium molecule is just a helium molecule, no extra charge to play with.
If intelligent life evolved on a planet of a brown dwarf — a “failed” star — that was ejected from its original galaxy deep into intergalactic space, then that species would be spectacularly isolated.
Note that the “naked eye” stars we see in our night sky are all big, bright stars in our immediate vicinity.
Outside of a galaxy the night sky would be black, other than some fuzzy smudges of other galaxies.
It would be a long time before any such species would figure out what galaxies are, what stars are, and their own relationship to those things.
Their study of astronomy would take a wildly different path even assuming they end up at the same conclusions!
And then what? What missions could they envisage, tens of thousands of light years away from the next nearest… anything?
Do we have a good estimate for the density of intergalactic stars? Or how far away from a star will you be on average, when you are, say halfway between the Milky Way and Andromeda?
Apparently this is very new science, the information is still being collected as cutting edge research.
One thing that is clear is that the intergalactic medium has a highly variable density. In the vicinity of a recent galactic merger or near-miss, there would be a smear of stars fading off into the distance.
Conversely, even a fairly quiet and passive galaxy like our own is expected to eject stars at a rate of one every few hundred years from the core region immediately nearby the black hole there.
> If intelligent life evolved on a planet of a brown dwarf — a “failed” star — that was ejected from its original galaxy deep into intergalactic space, then that species would be spectacularly isolated.
Even better, (or worse): A species that evolved on a rogue planet! Without any star!! (heated by it's core or nuclear elements or space magic or whatever)
> It would be a long time before any such species would figure out what galaxies are, what stars are, and their own relationship to those things.
Humans are bad enough with our "We're unique and special!" complex, imagine theirs!! lol
Such a fantastic overview. And here we are, instead of building the infrastructure for accelerating solar sails, we're investing the money in AI-pornbots instead :/
AI porn sells, solar sails are a research project at best. There is no money to be made from space flight, only discovery, and unfortunately capitalist forces far outweigh curiosity.
Even the space race wasn't for science but for politically one-upping the others, doubly so because being able to bring a payload into space also demonstrates they can bring a payload anywhere on the world.
It is stated multiple times across the article that the probe would need a means of changing is trajectory, but not even a hint of idea how that could possibly be done is given. So the most important and blocking aspect of the mission is simply skimmed over, and the rest of it is built upon this omission as if it was something trivial to come up with.
Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
Since momentum is conserved, why not just have a 2 of the 1 g probes strapped to each other with a spring in between. When you need a course correction at 100 AU out (or whatever). The probes calculate how much of a correction is needed, adjusts a screw that tightens or loosens tension on the spring, reorients itself appropriately with a reaction wheel, then the two probes are released from each other, begin pushed apart with the spring. One probe gets the trajectory correction it needs, and the other gets further off course. Maybe with some gravity assists with nearby objects.
https://en.wikipedia.org/wiki/Gravity_assist
also:
Roundtrip Interstellar Travel Using Laser-Pushed Lightsails
https://ia800108.us.archive.org/view_archive.php?archive=/24...
Isn’t that basically how a rocket works? Throw stuff out one side to get the thing on the other side moving. Not sure how this would compare to a rocket engine with hyperbolic fuel.
Only in the sense that throwing a knife at someone is the same as shooting a howitzer at them.
Specific impulse.
As far as impulse goes, the spring will probably be pretty inefficient relative to mass.
The point we are trying to make is that there hardly anything that would be less efficient relative to mass.
No. Very much no. The spring system would literally throw away half the mass of the craft for, maybe, a 10m/s delta. Fireworks would be more efficient. A pitching machine attached to a huge pile of baseballs would be more efficient (ie the baseballs could be thrown faster).
They all weigh a lot more than 1g though.
https://en.wikipedia.org/wiki/Specific_impulse
Please read.
Yes.
It compares in that it doesn't require said hyperbolic fuel. That fuel is heavy and finite.
You can think of the hypergolic fuel as a type of spring. The chemical energy stored in the bonds of the fuel is what pushes the fuel products apart when it reacts. This is what pressure is, it's nothing more than KE of molecules.
The 'spring action' of fuel is very good because there's a lot more energy (per unit mass) stored in the bonds. Orders of magnitude more than a mechanical spring.
But a mechanical spring will reset itself to its natural position once tension is released
Uh, it does - the ‘fuel’ is the other probe.
Notably, this also has a particularly bad ISP?
Also, probes are presumably also heavier and rarer?
That's just a really, really ineffective rocket. A spring has nowhere near the energy density of chemical fuel.
Because the specific impulse of the spring is negligible when you’re moving at 1/10c and why would they send a 1g probe if they could accelerate 100kg to that speed? Why do you suppose doubling the weight would be free instead of making the system infeasible?
Can a gyro work in space? Probably not or all the satellites would be using it instead of gas/ionized gas based propulsion.
Gyroscopes are used in spacecraft / satellites in the same manner they are in aircraft, to measure changes in orientation.
Reaction wheels are used to make adjustments to orientation. See https://en.wikipedia.org/wiki/Reaction_wheel
Thrusters of all sorts can also be used, generally to maintain altitude in satellites, and more generally to provide thrust for space probes.
What would the "screw" push off of? That rotational force would need to go somewhere or be corrected, else the probes would just rotate. I guess a gyroscope could do that, but what you're describing just sounds... very roundabout, and in terms of force, a few kilos of propellant would have the same effect.
This is infeasible for the reason other have mentioned about specific impulse. But surely you can imagine a set of parallel boards with a coil spring between them and a set of cylindrical guide rods to prevent relative rotation between the boards. A motor fixed to one board turns a screw that engages with threaded nut on the other board, mounted on a thrust bearing, and guide bushing that allows a linear movement, but disallows the rotation degree of freedom. Think of the lead screw on a milling machine or lathe.
It's not skimmed over, they cover it near the end in the "Requirements and challenges" section:
> The most challenging phase of the mission may be related to how the nanocraft can transfer from an unbound to a bound orbit and start orbiting around the compact object. All possible solutions should be considered carefully. In the case the transfer is not possible, we may redesign the mission to perform the scientific tests when the nanocraft passes close to the black hole. For example, when the nanocraft is close to the black hole, it may separate into a mother-nanocraft (with a wafer and sail) and a number of small nanocrafts (without sails). The nanocrafts could communicate with each other by exchanging electromagnetic signals. The mother-nanocraft could compare the trajectories of the small nanocrafts to those expected in a Kerr spacetime and send the data to Earth.
Light sales can theoretically be used to not only accelerate away from Earth, but also decelerate at the end of an interstellar journey (see Robert L Forward's work). The practicality of that is another matter.
There’s a really straightforward way to avoid a parabolic trajectory with a black hole. But data retrieval gets a bit difficult.
More seriously, it floors me how often and consistently people forget that the accretion disk is essentially a partial accelerator and crossing or entering it will probably pulverize you to radioactive dust. Possibly before you could hit the event horizon.
Not every black hole has an accretion disk, especially not isolated ones.
So the question there is if it’s worth it for us to study a naked singularity. What would it teach us?
And how do you get into orbit?
Naked singularities lack event horizons, not accretion disks. By definition, black holes are not naked singularities.
Is it worth studying?
Yes. Yes it most certainly is. Whatever we learn will be new.
> It is stated multiple times across the article...
I was a bit confused by your comment, but I think the article you're referring to is not the OP, but the article the OP was commenting on: https://www.cell.com/iscience/fulltext/S2589-0042(25)01403-8...
> Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years. That also seems incompatible with the weight constraint.
>I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years.
Just spit-balling here. Send out the first batch of probes and then 5 years later send another batch of probes. The first batch of probes does their surveying for 5 years, when the later batch of probes start arriving. The data is uploaded to the late-comers, who aren't on an intercept course. Instead they are on a trajectory that causes them to swing around the black hole, and head on back to earth with the data.
> Send out the first batch of probes and then 5 years later send another batch of probes.
What's the separation there, at 0.33 lightspeed? 1.65 light years? Wikipedia says Voyager is 168.35 AU away, and Google says that's 0.00266 light years. Voyager has 23-watt radio focused by a 3.7m dish and its signals are received by a 70-meter dish on Earth.
So you're talking about a 1g spacecraft signaling another 1g spacecraft over 620 times the distance to Voyager, without any of the beefy equipment that exists on both ends of the Voyager link.
Hmm. Seems like you are you multiplying 5 years by 33% of light speed to come up with 1.65 light years? I apparently didn't explain well enough. The 5 years is for the first batch of probes to gather data over an extended period of time (while in orbit around the black hole). The second set of probes is just a roundtrip "fly-by" to collect the data from the first probes and return it to earth. No reason that the return trip probes would have to be very far from the data gathering probes. Maybe you can't orbit close enough to the black hole at these speeds without getting too close to the accretion disk?
Even then, I think you're going to have massive distances between tiny probes moving very fast relative to each other. Maybe not 1.65 light years, but communication over Voyager's 0.00266 light years or even a much smaller distance (e.g. Earth to moon) seems insurmountable for two 1g probes.
Also, the probes are in deep space, right? No solar power. Where are they going to get the energy?
https://en.wikipedia.org/wiki/Betavoltaic_device ?
So skip the communication, and just have the one probe do the gravity assist to get headed back to earth with the data it collected.
>I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years.
Split particle pairs. We just need to repeal the no cloning theorem, maybe if we promise to not use it for FTL communication the legislators would go for it.
We could call them "Sophons" while we're at it.
People don't realise this, but you can steer perfectly fine with a solar sail. That's because photons transfer momentum not just when they hit the sail, but also when they are emitted after reflection. So just by turning the sail at an angle, you can create a force in any direction perpendicular to the velocity vector. Using a two sail system, you can even accelerate and slow down along a single beam path. So you could theoretically travel to mars with a constant acceleration/deceleration phase (like a flip-and-burn in the Expanse) using only one beam emitter on earth.
How long would it take for a person to get to Mars with a sail powered by an Earth-based laser?
Infinite time since we have no realistic way of making such a laser at this time - and anyone trying it is likely to get nuked before they finish their massive death ray.
Stipulate that we have the laser.
Depends entirely on the power output of the laser, the dispersal length and the size, weight and reflectivity of the sail. Since we are already talking about imaginary technology, any answer between "slower than current chemical rockets" and "some significant fraction of the speed of light" could be valid.
I don't think that is correct. I think there's a rather disappointing limit on the acceleration a laser sail can reach with known materials.
You explicitly asked for unknown materials. Because there is no known material because such a laser does not exist. We have solar sail prototypes that were using the sun's light, but even they are far off in terms of size/weight ratio and reflectivity.
No, I didn't ask for unknown materials; lasers can be built with known materials. Also solar sails aren't lightsails, and the topic here is lightsails.
If we’re just making stuff up, why not just have a warp drive or something?
Simply. You do Monte Carlo with the probes. You fire 1000 and one or two will have perfect trajectory so that no correction is needed.
I don't think 1000, or even 1000000 are enough if you use random directions. Space is <huge>huge</huge>. This has been posted here afew times https://joshworth.com/dev/pixelspace/pixelspace_solarsystem....
Did you, by any chance, play Outer Wilds recently?
> So the most important and blocking aspect of the mission
Idk, i think the fact they are using statistical arguments that there should be a nearby black hole, but haven't actually found any or have any idea where they are, is pretty blocking.
"steering" is a word that can lead to confusion because it leverages the intuition that we have with our ground vehicles.
A change in direction in space requires accelerating the vehicle in some direction, the effect of which is just simple vector addition of the velocity vector of the vehicle.
So if you are going with a huge velocity in one direction and you want to change direction significantly in another direction you have to change velocity (accelerate) a lot in order for the combined vectors to produce a significantly different final velocity vector
Solar sails. You can fire a shit ton of lasers from the planet (or orbit) at the probes and very,very slowly boost them up to the desired velocity.
Easy fix: change the description to "Interstellar Mission to the General Galactic Vicinity of a Black Hole"
gyroscopes?
Isn't Relativistic time dilation a problem for this idea? To the probe, the trip is only a few centuries but to us on Earth, millions of years. Maybe 0.1c isn't enough to cause this to be a huge problem but I think it is. Perhaps one of you Einstein enjoyers can tell us for certain.
Time dilation is 1/sqrt(1 - (v/c)^2). So at 0.1c that’s 0.5%. Certainly much higher than any human has ever experienced! But not exactly gonna change 100y to 100,000,000y.
Time dilation is exponential. At 0.1c it's definitely measureable but not a practical problem.
No need to be snarky and especially not here re basic science. Time dilation happens exponentially, ie with 0.5c you don't have time going 1/2 slower, rather a miniscule amount. Once you keep approaching speed of light closer and closer, all things go extreme (time, energy required, mass and so on).
Seems like first we need to get out of the gravity well... Then we need to cure ageing to give people skin in these games... Then we need to crack FTL or find a way to cryo-sleep or we end up with dystopian science fiction ships of the damned...
Not in my lifetime I suspect...
What’s be super cool is discovering a! asteroid mass primordial black hole in our solar system. No epic interstellar flight needed.
It would be super hard to detect though. We’d have to spot it by gravitational effects or get very lucky and notice lensing. It would emit nothing unless it happened to be nomming on some matter, and even then it’d be so small that the signal would be weak.
That would be cool.
I read somewhere that a black hole with the mass of the moon will absorb about as much cosmic radiation as it emits Hawking radiation. This is a fine line between "the black hole disappears before we can examine it" and "oops, we got eaten by a black hole".
Hey, its not like an analog of "Yeah, lets just throw some more mass at the newly-forming black hole in our neighbourhood", said every human that has ever thrown things into the fire, forever ..
Sorry, but I have to link the "Hole Lotta Trouble" episode of Pocoyo https://www.youtube.com/watch?v=HL_0OL7vZ44
Yes, you really do.
Black holes aren't cosmic vacuum cleaners. They're just super super super compact objects.
I've actually posted this a few times:
If you suddenly transformed the Moon into a black hole of the same mass, it would continue to orbit the Earth in the same spot. It wouldn't suck up the Earth or anything. The ocean tides would continue as normal under the influence of the black-hole-moon's gravity, which would be the same if it was orbiting at the same distance. You wouldn't see a moon in the sky, but if you focused a good telescope on where it was you'd see gravitational lensing. It would be a little smaller than a BB.
If it's in a stable orbit in the solar system, it wouldn't be able to "eat" us. Black holes gravitate exactly the same as any other mass, so it would have the same gravitational effect on Earth as any object if the same mass.
What makes black holes special is that you can get much close to their center of mass than you can with normal objects. When you're that close - inside the radius that a normal density object of that mass would have - then you experience gravity at a much higher strength than normal.
Put another way, even if our Moon was a black hole with the same mass, very little would change except that it would no longer reflect sunlight. Ocean tides on Earth would remain the same. You wouldn't want to try to land on it though...
There was a movie where Moon was a hi-tech 'megastructure' with a white dwarf inside. I wonder if it would be theoretically possible to set up such a mini-dyson sphere around a mini-blackhole.
A black hole, or neutron star, would make much more sense in that scenario than a white dwarf.
A white dwarf smaller than the moon seems unlikely, if not impossible. If it were that small, unless it was in the (fast) process of collapsing to a neutron star, it wouldn't have enough mass to remain that compact.
A neutron star or black hole would work fine, because both can easily have radii much smaller than the Moon's.
Here's an article about that - https://www.fandom.com/articles/moonfall-real-life-astrophys... :
> “There are just so many things wrong with [the idea of a white dwarf inside the moon],” says Romer. “Now, a white dwarf is a very compact object. But, you know — people have heard of neutron stars — neutron stars are ultra-compact objects, they’re a few tens of kilometres across. White dwarfs are actually about the size of a normal star.”
You can come up with scenarios where white dwarfs are much smaller than a star, but smaller than the Moon is iffy at best.
As for the Dyson sphere idea, the biggest problem with it in this scaled-down scenario is stability. You can't exactly support it with struts, or something.
On that subject, I highly recommend the video "dyson spheres are a joke": https://www.youtube.com/watch?v=fLzEX1TPBFM , by astrophysicist Angela Collier. But you need to either watch all 53 minutes, or skip to near the end, to find out just how literal the title is.
If you set it up at the right radius it would have 1g gravity at the surface, like a little mini-world. It wouldn't be able to hold an atmosphere though, so it would have to have pressurized buildings on it.
Somebody write a sci fi with this please, just make sure to describe how trash disposal works
If you're interested in black holes and trash disposal, check out the 1978 short story, "The Nothing Spot": https://vintage.failed-dam.org/nothing.htm
>It would be super hard to detect though.
Would it? I would've thought there is enough dust in the solar system that it would create constant xray emissions. Even if it's faint, it would stick out like a sore thumb on super sensitive xray telescopes.
An asteroid-mass black hole is around a micron across. It's not going to be nomming on much because the matter distribution inside the solar system isn't that dense.
Any tiny black hole born in the big bang would either have evaporated (if Hawking was right...) or would have grown much larger by now.
Even a moon-mass black hole (0.1mm) wouldn't be eating much, although its gravitational effects would be much more obvious.
We do not what such a thing anywhere near Earth though. https://arxiv.org/abs/astro-ph/9911309
Only if it evaporates, which it probably wouldn't do for billions of years.
Something of asteroid mass would be above the CMB equilibrium temperature, thus already be undergoing runaway evaporation. From the paper:
"This implies that M must be less than 0.8% of the mass of the Earth"
If it was asteroid mass, wouldn't it have the same gravitational effect of an asteroid itself? Plus, someone else mentioned it'd be like a micron across, which if my pop-sci understanding of these things is correct, it'd disappear in a poof of hawking radiation.
It would have the same mass, and it would be tiny -- like the size of a hydrogen or helium atom.
AFAIK an asteroid mass black hole wouldn't evaporate yet since the CMB is still warmer than its Hawking temperature. Very tiny black holes would have evaporated earlier in the universe. A black hole evaporates when its Hawking temperature exceeds the ambient temperature.
I remember reading somewhere that it's possible for such a black hole to get captured by an asteroid (or vice versa, I guess), and happily live inside a rock, slowly orbiting inside the asteroid, sucking up atoms here and there.
It would be detectable as an asteroid that's twice as dense as it should be.
Could you find it by Hawking radiation?
We wouldn't have to get lucky if it was on the last stages of evaporating. If it has reached a mass of about a billion kg it would be shining plenty bright to detect, and would only have a few thousand years to live before destroying most life on Earth with gamma radiation.
According to this calculator https://www.vttoth.com/CMS/physics-notes/311-hawking-radiati..., the luminosity would only exceed that of the sun for 46.7 nanoseconds, so unless it's much less than 1 AU away we would probably be fine.
Related: "Project Solar Sail" by Arthur-Clarke and others, is a good anthology (stories, essays and illustrations) about the new Age of Sailing (Sailing in Space)via lightships and solar sails.
The most aggressive yet most realistic project we could reasonably do is the SGL Telescope
Won't happen under this administration and really might take a planet-wide effort but it would be incredible
https://www.centauri-dreams.org/2022/07/22/solar-gravitation...
https://www.nasa.gov/general/direct-multipixel-imaging-and-s...
https://www.universetoday.com/articles/a-mission-to-reach-th...
How do you stop if your solar sail has you going near light speed? Or does it strand you halfway between stars in the doldrums where the force on both sides of your sail equals out from two stars?
You don't stop this type of craft, it's strictly accelerate and coast type of thing.
Also note that "solar sail" is a bit misleading, the (now apparently dead) Breakthrough Starshot design was a big reflector "sail" in space and very many lasers on Earth to power it, it's not actually driven by a stellar wind directly.
This suggests ejecting a secondary mirror in front of the craft to reflect light to brake the original craft: https://arxiv.org/pdf/1604.01356:
"...or by ejecting a reflector that is then used as a braking system (similar to thrust reversal on jets) but this only works if the payload is still within illumination range of the primary laser system"
Flipping the sail around would probably be the lightest option, though tricky because the larger sail designs would not be rigid.
Solar sails aren't powered by solar wind but by light reflecting off like the probe. But the probe would be powered by laser so not really "solar" sail. Light sail is the generic term.
You would fold the sail?
That only stops you accelerating, it doesn't put the brakes on
Deceleration is the same as acceleration. You use the light of the star you're approaching to slow down.
But if you're going near light speed, the light / particles would be too faint to have any significant effect until you get very close. You'd basically just fly backwards straight into it. Unless your sail is very large and/or the total mass is very small.
That would not stop the probe from continuing to glide further. He's making a good point here.
Gliding is fine. We whizzed past Pluto with New Horizons. Never stopped, just a photo flyby.
I don't think we can just go near speed of light. Even hard vacuum out there contains particles. Heliosphere is chock full of them, then Oort cloud has stuff way bigger than that (or any probe), even if sparsely spread out. Then there is cosmic stuff outside, as Voyager found out.
Getting hit by some random molecule when orbiting Earth or just travelling say 30,000 kmh is one thing. Getting hit by swarms of molecules with say 0.5c can be catastrophic to the material. Now imagine wading through some space dust cloud, or even plasma cloud (ie remnant of some bygone supernova).
Star trek had shields, and for good reasons. Super strong magnetic field may divert some charged particle, but helium molecule is just a helium molecule, no extra charge to play with.
Nit: shields were just for battle, for this they used the deflector.
> Or does it strand you halfway between stars in the doldrums where the force on both sides of your sail equals out from two stars?
This is actually I "love" to think about:
What would it be like, to be "stranded" in the space far from any stars?
or in the "voids" where there are relatively very few stars/galaxies to begin with?
There must be things drifting there right now...
It would also be the perfect place to HIDE something :)
If intelligent life evolved on a planet of a brown dwarf — a “failed” star — that was ejected from its original galaxy deep into intergalactic space, then that species would be spectacularly isolated.
Note that the “naked eye” stars we see in our night sky are all big, bright stars in our immediate vicinity.
Outside of a galaxy the night sky would be black, other than some fuzzy smudges of other galaxies.
It would be a long time before any such species would figure out what galaxies are, what stars are, and their own relationship to those things.
Their study of astronomy would take a wildly different path even assuming they end up at the same conclusions!
And then what? What missions could they envisage, tens of thousands of light years away from the next nearest… anything?
Do we have a good estimate for the density of intergalactic stars? Or how far away from a star will you be on average, when you are, say halfway between the Milky Way and Andromeda?
https://en.wikipedia.org/wiki/Intergalactic_star
Apparently this is very new science, the information is still being collected as cutting edge research.
One thing that is clear is that the intergalactic medium has a highly variable density. In the vicinity of a recent galactic merger or near-miss, there would be a smear of stars fading off into the distance.
Conversely, even a fairly quiet and passive galaxy like our own is expected to eject stars at a rate of one every few hundred years from the core region immediately nearby the black hole there.
> If intelligent life evolved on a planet of a brown dwarf — a “failed” star — that was ejected from its original galaxy deep into intergalactic space, then that species would be spectacularly isolated.
Even better, (or worse): A species that evolved on a rogue planet! Without any star!! (heated by it's core or nuclear elements or space magic or whatever)
> It would be a long time before any such species would figure out what galaxies are, what stars are, and their own relationship to those things.
Humans are bad enough with our "We're unique and special!" complex, imagine theirs!! lol
It’s where the future hides :)
Sied
What is the point of such a mission? There is literally nothing to see there.
A black hole may be invisible but its accretion disk and the effects on the light being deflected around it are anything but.
Such a fantastic overview. And here we are, instead of building the infrastructure for accelerating solar sails, we're investing the money in AI-pornbots instead :/
Considering AI-pornbots are increasing the derivate of the function, they might actually be the right move.
What are the odds the first alien probe to visit the solar system will be a pornbot or some form of marketing droid?
If you subscribe to the Futurama school of comedy, very high, lol.
https://xkcd.com/1642/
Well, they are both on a mission to a black hole.
AI porn sells, solar sails are a research project at best. There is no money to be made from space flight, only discovery, and unfortunately capitalist forces far outweigh curiosity.
Even the space race wasn't for science but for politically one-upping the others, doubly so because being able to bring a payload into space also demonstrates they can bring a payload anywhere on the world.
At least the AI-pornbots will operate from space. /s
Having read Michael Crichton's Sphere, I think I know how this ends.