NASA selects a plan to "swarm" Proxima Centauri with tiny probes(sciencealert.com)
sciencealert.com
NASA selects a plan to "swarm" Proxima Centauri with tiny probes
https://www.sciencealert.com/nasa-selects-a-wild-plan-to-swarm-proxima-centauri-with-thousands-of-tiny-probes
136 comments
This happens constantly. Some random scientist at one of NASA's dozen's of labs write a speculative proposal, and all the news articles say "NASA plans to do X".
What's a more accurate and neutral title?
Breakthrough Starshot is a scam and I can't believe that NASA is falling for it.
1. Extremely high duty cycle 100 gigawatt laser. (edit: now apparently it's an "array" because someone with a brain mentioned that a 100 gigawatt laser is ludicrous) That's right 7 peak summer output Grand Coulee Dams and 12 Palo Verde nuclear power plants with all reactors operating simultaneously COMBINED would be needed to power this laser.
2. "Swarm" (jfc buzzwords) craft that are currently impossible to create. The swarm behavior including networking, sensors, radio, and command and control do not exist and are impossible at a simple base level when considering RF energy requirements even with far-future theoretical energy harvesting technology.
3. Perfectly-spherical-frictionless-cow-ifying the EXTREMELY REAL effects of space weather. Forget the interstellar medium, these things will be blown out of the beamwidth by the time they reach jupiter's orbit from solar winds alone.
1. Extremely high duty cycle 100 gigawatt laser. (edit: now apparently it's an "array" because someone with a brain mentioned that a 100 gigawatt laser is ludicrous) That's right 7 peak summer output Grand Coulee Dams and 12 Palo Verde nuclear power plants with all reactors operating simultaneously COMBINED would be needed to power this laser.
2. "Swarm" (jfc buzzwords) craft that are currently impossible to create. The swarm behavior including networking, sensors, radio, and command and control do not exist and are impossible at a simple base level when considering RF energy requirements even with far-future theoretical energy harvesting technology.
3. Perfectly-spherical-frictionless-cow-ifying the EXTREMELY REAL effects of space weather. Forget the interstellar medium, these things will be blown out of the beamwidth by the time they reach jupiter's orbit from solar winds alone.
> 1. Extremely high duty cycle 100 gigawatt laser. (edit: now apparently it's an "array" because someone with a brain mentioned that a 100 gigawatt laser is ludicrous) That's right 7 peak summer output Grand Coulee Dams and 12 Palo Verde nuclear power plants with all reactors operating simultaneously COMBINED would be needed to power this laser.
That's not how this stuff works. You would use some sort of large capacitor/battery bank which is charged by a much smaller power draw over a long time, and then dump the energy over a short time.
The laser array currently operating at the National Ignition Facility has a peak output of 500 TW, more than three orders of magnitude higher than the number you called ludicrous. Obviously Starshot would be applying that power for a much longer time interval, and indeed would be a global undertaking dwarfing NIF. But it doesn't need 100GW of dedicated power plants.
That's not how this stuff works. You would use some sort of large capacitor/battery bank which is charged by a much smaller power draw over a long time, and then dump the energy over a short time.
The laser array currently operating at the National Ignition Facility has a peak output of 500 TW, more than three orders of magnitude higher than the number you called ludicrous. Obviously Starshot would be applying that power for a much longer time interval, and indeed would be a global undertaking dwarfing NIF. But it doesn't need 100GW of dedicated power plants.
Do they not need to run it/them continuously for years for a solar sail approach to make sense? NIF is not a good comparison for exactly that reason.
No, the acceleration phase is only for a few minutes. (I agree with you that if it requires 100 GW of power for years, his criticism would be accurate.) After a few minutes, the probe is already so far away from Earth that you can't focus the lasers effectively on it.
From wikipedia:
> ground-based lasers would then focus a light beam on the crafts' sails to accelerate them one by one to the target speed within 10 minutes, with an average acceleration on the order of 100 km/s2 (10,000 ɡ)
Well damn, then. I missed that when I was reading about it before. https://en.wikipedia.org/wiki/Breakthrough_Starshot
> ground-based lasers would then focus a light beam on the crafts' sails to accelerate them one by one to the target speed within 10 minutes, with an average acceleration on the order of 100 km/s2 (10,000 ɡ)
Well damn, then. I missed that when I was reading about it before. https://en.wikipedia.org/wiki/Breakthrough_Starshot
NIF's laser works for only 1microsecond, took over a decade to build and the price was over 3.5 bln.
"Peak current for the system exceeds 100 million amperes and the peak power exceeds 1 terawatt (1 trillion watts)"
https://lasers.llnl.gov/about/how-nif-works/power-conditioni...
Peak NIF power is actually only ~a nanosecond. And I acknowledged that Starshot would be a global undertaking that dwarfs NIF. I'm just saying that it's wrong to say this is going to require 100 GW of industrial power plants.
> > high duty cycle
This means that the laser is on most of the time.
If the laser has 70% efficiency, and is on 35% of the time, you need 100 / .7 * .35 = 50GW average (and 100 / .7 = 142GW when lasing). Any storage you have would have to be long term, because you need to lase when the spacecraft is overhead and not at night.
This means that the laser is on most of the time.
If the laser has 70% efficiency, and is on 35% of the time, you need 100 / .7 * .35 = 50GW average (and 100 / .7 = 142GW when lasing). Any storage you have would have to be long term, because you need to lase when the spacecraft is overhead and not at night.
He's using it to mean "high duty cycle over a time-period of minutes". That would be relevant if his criticism was "we don't know how to build lasers that use that much power for that much time" (which is true, currently), but in fact his criticism was that it would require industrial power plants capable of outputting 100 GW (which is wrong). The big power draw of 100 GW over ~minute timescales is for the purposes of launching one probe. After that your power draw stops and you can recharge for as long as you want before the next probe launch. So it's not high duty cycle over timescales longer than hours or days or years.
The thing is, it'd fundamentally different from lasers that have timescale of microseconds or less. He mentioned "capacitor banks."
Launching 20 per day over a 10 minute span each is 200 minutes; you still need 12GW average over the day.
And you need an insane amount of storage-- if 12% of the energy comes directly from the power plant, you need to store 53 terajoules, which is about 60,000 tonnes of lithium batteries per daily shot. (It's more than that, because you're power/discharge rate limited, and it's going to wear out that minimum amount of batteries quickly).
Launching 20 per day over a 10 minute span each is 200 minutes; you still need 12GW average over the day.
And you need an insane amount of storage-- if 12% of the energy comes directly from the power plant, you need to store 53 terajoules, which is about 60,000 tonnes of lithium batteries per daily shot. (It's more than that, because you're power/discharge rate limited, and it's going to wear out that minimum amount of batteries quickly).
> He mentioned "capacitor banks."
No he didn't. I did.
> Launching 20 per day over a 10 minute span each is 200 minutes; you still need 12GW average over the day.
Where are you getting 20/day from? I didn't see it on this OP link or the Wikipedia page. I'd have guessed more like once a week, which is 100 MW. That's a reasonable size for a gas turbine power plant, which seems like an appropriate expenditure for a project like this.
As a point of reference, the entire globe launches something to space every couple days on average.
No he didn't. I did.
> Launching 20 per day over a 10 minute span each is 200 minutes; you still need 12GW average over the day.
Where are you getting 20/day from? I didn't see it on this OP link or the Wikipedia page. I'd have guessed more like once a week, which is 100 MW. That's a reasonable size for a gas turbine power plant, which seems like an appropriate expenditure for a project like this.
As a point of reference, the entire globe launches something to space every couple days on average.
> Breakthrough Starshot is a scam and I can't believe that NASA is falling for it.
I know some of the folks involved and they are working on 50 years to launch. It's a long term (multiprong) research project.
I wouldn't call it a scam, I would call it "blue sky" (if it weren't a space project!)
I know some of the folks involved and they are working on 50 years to launch. It's a long term (multiprong) research project.
I wouldn't call it a scam, I would call it "blue sky" (if it weren't a space project!)
> I wouldn't call it a scam, I would call it "blue sky" (if it weren't a space project!)
Uh, don't we already have "moonshot" for this kind of endeavor, which the name "starshot" already plays on / speaks to?
Uh, don't we already have "moonshot" for this kind of endeavor, which the name "starshot" already plays on / speaks to?
Seems likely some of the tiny probes will end up in the star so I suppose the name would be appropriate :-)
>I know some of the folks involved and they are working on 50 years to launch.
I.e. far enough in the future to safely assume all current employees will happily retire. Isn't that brilliant?
I.e. far enough in the future to safely assume all current employees will happily retire. Isn't that brilliant?
Is it any different from building a cathedral?
50 years to launch is a scam. I literally calculated rough trajectories using basic software (NASA EMTG) on how to get a probe out in the rough direction of proxima centuri now. A 50 year timeline on relatively simple things like this should be laughed out of the room. Even though Elon Musk is morally reprehensible now, his “unrealistic” schedules of 2 years may go over for moonshots but even twice the amount of time means the project is done in 4-5 years. Not some ridiculous 2 generation long schedule.
If it takes 2-4% of the world's current electricity production to propel the things alone, we're maybe not ready to do it quite yet.
But we're ready to start thinking about it. Just like we dreamt about rockets going to the moon decades before we attempted going to the moon.
But we're ready to start thinking about it. Just like we dreamt about rockets going to the moon decades before we attempted going to the moon.
let me understand: you played with a software vaguely related to the topic for 5 mn and it was enough to decide that 50 years to make happen a mission that was never done before is a scam ?
It's one of many competing research projects, the sum total of which add up to less than a single shuttle launch. I'm content with a dead end or two.
After writing my comment I looked it up and it’s the financial equivalent of a couple of post-docs for a year or two so I’m a lot less negative.
Post-docs need to write papers. Let them write some about an impossible thought experiment.
If they go past that though…
Post-docs need to write papers. Let them write some about an impossible thought experiment.
If they go past that though…
You announce this kind of project so Congress Critters can get all up in arms about wasteful spending and is something that can then later be sacrificed to make them feel like they've done their job. Meanwhile...you have other projects that have been protected from the axe because the sacrifices of this farcical project.
So you're saying it's like the Queen's duck? https://bwiggs.com/notebook/queens-duck/
This is a tactic as old as the review/inspection process itself. The reviewer always needs to feel like they've done their part, and no product can be perfect on the first pass, right? So put the obvious thing there for them to find, or they will find the thing you are trying to squeak through the process.
I had one building inspector tell me that when he found the obvious thing that was obviously obvious, he would then look for the thing trying to be hidden.
I had one building inspector tell me that when he found the obvious thing that was obviously obvious, he would then look for the thing trying to be hidden.
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Given 1.6 sq meter 500W solar panels, that's an area of 320 square kilometers. That can be constructed at $1/w at $100 billion.
Also it's not necessary (or technically, it's actually impossible) to have 100% duly cycle laser for propulsion.
It's definitely a megaproject, but it's not a "scam"
Also it's not necessary (or technically, it's actually impossible) to have 100% duly cycle laser for propulsion.
It's definitely a megaproject, but it's not a "scam"
For comparison 320km2 is about 2.5 San Franciscos
I asked chatgpt to make a quick demo to demonstrate the size of the 18x18 km2 square:
https://lxe.github.io/map/
https://lxe.github.io/map/
Neat. How did you ask it to make that? Do you mind sharing the transcript?
> That can be constructed at $1/w at $100 billion.
Is this in space or on the ground?
Is this in space or on the ground?
Lasers are running at 30-40% efficiency so for a 100GW laser you need 400GW power plant. But the power plant and transmission has some losses so you probably would need 500GW
I think for the foreseeable future we'll have better uses for the electricity than powering a laser to accelerate some probes.
I'm curious about whether it's even feasible based on dispersion issues. My understanding is that it's hard to beat dispersion over long distances, regardless of your optics on the laser (and we're talking long distances here...)
Any optics experts able to chime in?
Any optics experts able to chime in?
Beam divergence has to do with your output aperture.
The smaller the hole the laser light comes out of, the more it spreads.
This is a big, several kilometer phased array, which has an effective hole size of a few kilometers. As a result, divergence is less.
The smaller the hole the laser light comes out of, the more it spreads.
This is a big, several kilometer phased array, which has an effective hole size of a few kilometers. As a result, divergence is less.
Not an optics expert but I consult for a company that makes lasers. Afaik not currently possible. The beam divergence is only one of many limiting factors
I am not a physicist. Does beam divergence decrease in a vacuum? Could we put the lasers in space at L5 to power the swarm? Or L5 for Venus for the increased solar flux?
It's almost entirely a function of wavelength and aperture diameter. It's basic wave mechanics, and is almost impossible to improve upon.
I just recently watched a great video explaining how lithography machines push the limits of what's possible: https://www.youtube.com/watch?v=rdlZ8KYVtPU&t=1151s
Note that the best ASML machines can eke out an improvement on the order of a factor of two at best, not two thousand, which is what would be likely needed to power space probes at light-year distances.
I just recently watched a great video explaining how lithography machines push the limits of what's possible: https://www.youtube.com/watch?v=rdlZ8KYVtPU&t=1151s
Note that the best ASML machines can eke out an improvement on the order of a factor of two at best, not two thousand, which is what would be likely needed to power space probes at light-year distances.
most laser systems get close to diffraction-limited divergence, which is governed by the size of your optics. vacuum vs. air affects it, but the effect is so small that you need sensitive instruments to detect the effect
https://en.wikipedia.org/wiki/Gaussian_beam#Beam_waist
the divergence angle is inversely proportional to your aperture diameter
https://en.wikipedia.org/wiki/Airy_disk
in theory by putting a bunch of laser emitters in solar orbit and operating them as a phased array you can make an aperture the size of the solar system. 1.22λ/d at, say, 400nm and 2 astronomical units of diameter is about 1.6 attoradians of divergence; at a radius of 4.3 light years (the distance to proxima centauri) this works out to an airy disk focal point of 66 microns. optical phased array lasers have been demonstrated https://en.wikipedia.org/wiki/Phased-array_optics but nobody knows how to make one out of satellites yet
i've only glanced at the proposal https://arxiv.org/pdf/2309.07061.pdf and they're proposing 4.1-meter-diameter 3.6-gram probes, which would allow you to use a phased array about a million times smaller, about 5 million km, 13 times the distance to the moon. i don't see where they're proposing how they propose to beam 100 gigawatts onto the probes so i don't know if this is their proposal
dispersion, by contrast, which means wavelength-dependent indices of refraction, doesn't affect lasers and doesn't happen in a vacuum; probably the person who mentioned it was using the wrong term by accident and meant divergence
https://en.wikipedia.org/wiki/Gaussian_beam#Beam_waist
the divergence angle is inversely proportional to your aperture diameter
https://en.wikipedia.org/wiki/Airy_disk
in theory by putting a bunch of laser emitters in solar orbit and operating them as a phased array you can make an aperture the size of the solar system. 1.22λ/d at, say, 400nm and 2 astronomical units of diameter is about 1.6 attoradians of divergence; at a radius of 4.3 light years (the distance to proxima centauri) this works out to an airy disk focal point of 66 microns. optical phased array lasers have been demonstrated https://en.wikipedia.org/wiki/Phased-array_optics but nobody knows how to make one out of satellites yet
i've only glanced at the proposal https://arxiv.org/pdf/2309.07061.pdf and they're proposing 4.1-meter-diameter 3.6-gram probes, which would allow you to use a phased array about a million times smaller, about 5 million km, 13 times the distance to the moon. i don't see where they're proposing how they propose to beam 100 gigawatts onto the probes so i don't know if this is their proposal
dispersion, by contrast, which means wavelength-dependent indices of refraction, doesn't affect lasers and doesn't happen in a vacuum; probably the person who mentioned it was using the wrong term by accident and meant divergence
> and they're proposing 4.1-meter-diameter 3.6-gram probes,
If you put 100 gigawatts on a 4.1 meter diameter very thin reflector, you're going to melt it. That's 10 gigawatts/square meter. Most of the light misses the targets.
> i don't see where they're proposing how they propose to beam 100 gigawatts onto the probes so i don't know if this is their proposal
A phased array on Earth, several kilometers in scale.
> but nobody knows how to make one out of satellites yet
Probably no one ever will make a huge (solar system scale) coherent power transmission system out of satellites, because of the thinned array curse-- https://en.wikipedia.org/wiki/Thinned-array_curse
It would be cool if we made a very large scale telescope, where a sparse array is less of a problem.
If you put 100 gigawatts on a 4.1 meter diameter very thin reflector, you're going to melt it. That's 10 gigawatts/square meter. Most of the light misses the targets.
> i don't see where they're proposing how they propose to beam 100 gigawatts onto the probes so i don't know if this is their proposal
A phased array on Earth, several kilometers in scale.
> but nobody knows how to make one out of satellites yet
Probably no one ever will make a huge (solar system scale) coherent power transmission system out of satellites, because of the thinned array curse-- https://en.wikipedia.org/wiki/Thinned-array_curse
It would be cool if we made a very large scale telescope, where a sparse array is less of a problem.
thank you, i didn't know about the thinned-array curse, and now that i understand it i agree that it would not be useful for this
Beam divergence, while happening at greater rate not in a vacuum, is a property of how photons propagate, so it's not something that can be eliminated
It would definitely depend on the area of the reflective surface. If it is few hundreds of km^2, which is definitely possible as we don't need any special mirror, it would be fine I guess. Even shining beam on patched up aluminium foil would work fine for sailing it.
Although we would need heavier support structure then. And the risk of micrometeoroids collision will be higher.
Although we would need heavier support structure then. And the risk of micrometeoroids collision will be higher.
100 GW isn't absurd, compared to global human energy consumption of around 20000 GW.
The problem is, until we figure out how to stop burning fossil fuels and fix climate change, the amount of spare power we have is actually a large negative number.
The problem is, until we figure out how to stop burning fossil fuels and fix climate change, the amount of spare power we have is actually a large negative number.
The power is so high so that the probes can be accelerated up to 20% of the speed of light while still in the solar system. The array does not run for long periods of time.
Your comment is a scam, and I despise shills.
This is the one time they are forcing the issue when the tech isn’t even close but instead throwing 100billion to make it happen. Maybe use half that to do research for better fuel, materials, miniaturization and the other 50 to launch with higher chance of success
This idea has shown up multiple times. I've never understood how they plan to communicate back, especially with a) gram-scale devices b) moving a significant fraction of the speed of light away from us while being c) multiple light-years away.
This article attempts to explain: https://www.nasa.gov/general/swarming-proxima-centauri/
"A swarm whose members are in known spatial positions relative to each other, having state-of-the-art microminiaturized clocks to keep synchrony, can utilize its entire population to communicate with Earth, periodically building up a single short but extremely bright contemporaneous laser pulse from all of them."
"A swarm whose members are in known spatial positions relative to each other, having state-of-the-art microminiaturized clocks to keep synchrony, can utilize its entire population to communicate with Earth, periodically building up a single short but extremely bright contemporaneous laser pulse from all of them."
So all these tiny satelites will also carry a laser and a power source for it? Yeah, good luck with it
A kind of bucket brigade. They aren’t planning to launch a cloud of these things and be done, they’ll be launching a long stream of them for years.
The probes can get power from the launch laser.
At least that’s the idea I got from talking to some of these folks last year.
The probes can get power from the launch laser.
At least that’s the idea I got from talking to some of these folks last year.
Probably the plan is to have some kind of small electronic that flies there and then sends signals back.
Probably also worth noting that the laser would have practical military uses.
LAZLO: "Looks at the facts: very high power. Portable. Limited firing time. Unlimited range. All you need is a tracking system and a large spinning mirror, and you could vaporize a human target from space."
KNIGHT: "This is not good."
KNIGHT: "This is not good."
I think we've stumbled onto the mission of the X-37b.
The distance is so ridiculously incomprehensibly far is hard to see this as anything except science fiction fantasy.
If you think this sort of thing is possible you really don’t understand how far it is.
To put it in relative perspective, if we represent the furthest distance humans have ever traveled as 1.3cm then the nearest star is 200 kilometers away.
If you think this sort of thing is possible you really don’t understand how far it is.
To put it in relative perspective, if we represent the furthest distance humans have ever traveled as 1.3cm then the nearest star is 200 kilometers away.
Yes, but...the analogy I like to use is to imagine that we are tiny creatures living in a hole in a vast sheet of ice. Our hole is ~1 au in diameter, Proxima Centauri is 270k au away. So if the hole is 1cm wide the next hole is ~2.7km away. That's a long way for a microbe to walk, but it's not outside the realm of possbility if the ice is very, very flat and it can make tiny ice skates such that you don't need to spend energy to maintain speed.
Of course, the real problem with the analogy is that the fastest you can go 1 cm in this universe is about 8 minutes. So the absolute shortest time it takes you to travel that 2.7km is 4.2 years. That's a few hundred cm per year. But in reality the best we could possibly do is a few tens of cm per year (e.g. c/10), and even that's in the realm of science fiction.
On the bright side, humanity has the Solar system all to itself with wonderful natural barriers to invasion and conquest. So we have time to figure out how to not blow ourselves up and/or stop dismantling our life support system to make Ikea furniture.
Of course, the real problem with the analogy is that the fastest you can go 1 cm in this universe is about 8 minutes. So the absolute shortest time it takes you to travel that 2.7km is 4.2 years. That's a few hundred cm per year. But in reality the best we could possibly do is a few tens of cm per year (e.g. c/10), and even that's in the realm of science fiction.
On the bright side, humanity has the Solar system all to itself with wonderful natural barriers to invasion and conquest. So we have time to figure out how to not blow ourselves up and/or stop dismantling our life support system to make Ikea furniture.
What about the voyager probes? How far has the farthest one travelled in your analogy?
Using the moon for the farthest distance humans have traveled… Voyager has traveled 60,000 times further (14 billion miles).
1 cm x 60,000 = 600 meters
Which is less than 0.5% of the distance to Alpha Centauri (“200 km” in the analogy, 25 trillion miles in real units)
Edit: a neighboring comment pointed out that on this scale of distance to moon ~= 1 cm, the Alpha Centauri system is more like 1000 km away. So voyager is less than 0.1% of the way.
1 cm x 60,000 = 600 meters
Which is less than 0.5% of the distance to Alpha Centauri (“200 km” in the analogy, 25 trillion miles in real units)
Edit: a neighboring comment pointed out that on this scale of distance to moon ~= 1 cm, the Alpha Centauri system is more like 1000 km away. So voyager is less than 0.1% of the way.
And voyager is going so fast because it used a clever gravitational slingshot technique, for which such a good opportunity hasn't yet arisen again.
Without that natural assistance, humans don't have the ability to leave the solar system - we just can't build a rocket powerful enough.
Without that natural assistance, humans don't have the ability to leave the solar system - we just can't build a rocket powerful enough.
Those gravitational slingshots are easy. It all comes from Jupiter, that's all you need. Saturn has 30% of the mass and two-thirds the orbital velocity, so that's a marginal gain on top of Jupiter, and the ice giants are smaller and slower yet.
The Jupiter launch window opportunity comes every 13 months so we can do that whenever we want. And we can launch rockets directly out of the solar system if we want; New Horizons had a backup plan of launching direct to Pluto if it had been delayed and missed the Jupiter-Pluto alignment.
That all said, the planetary slingshots aren't nearly enough to cross interstellar distances in a timespan measurable in human generations. We want something like 5% of the speed of light for that, where Voyager is going 0.005%.
The Jupiter launch window opportunity comes every 13 months so we can do that whenever we want. And we can launch rockets directly out of the solar system if we want; New Horizons had a backup plan of launching direct to Pluto if it had been delayed and missed the Jupiter-Pluto alignment.
That all said, the planetary slingshots aren't nearly enough to cross interstellar distances in a timespan measurable in human generations. We want something like 5% of the speed of light for that, where Voyager is going 0.005%.
Thanks for mentioning this. I did a bit of reading about the special alignment - very interesting stuff!
It seems like the alignment you refer to inspired the launch of Voyager 1 and 2 because they could visit so many planets at one time, and indeed it did slingshot them at quite some speed. However newer launches have reached similar speeds, and will escape the solar system due to improvements in launch technology.
It seems like the alignment you refer to inspired the launch of Voyager 1 and 2 because they could visit so many planets at one time, and indeed it did slingshot them at quite some speed. However newer launches have reached similar speeds, and will escape the solar system due to improvements in launch technology.
Pioneer 10, Pioneer 11, Voyager I and II, and New Horizons are all on solar escape trajectories. If you just want to get out of the solar system, existing tech plus a Jupiter gravity assist gets you there easily.
We probably could assemble some giant space hulk and put so much fuel into it that the rocket equation starts blushing. It would be insanely expensive and not at all too constructive, but we should be able to beat the speed record at least.
We could if we really wanted to: https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
Of course we can, we just choose not to. We've had designs for nuclear rockets for many decades now.
Well, to make his analogy more rigourous, because his 200 km is laughably too small.
Moon: 238,900 miles --> 1.3 cm or 0.00 km
(This defines the scale as 0.0000054416073670992 cm / mile.)
Voyager 2: 12,000,000,000 miles --> 65,299.0 cm or 0.65 km
Proxima: 25,000,000,000,000 miles --> 136,040,184.2 cm or 1,360.40 km
Moon: 238,900 miles --> 1.3 cm or 0.00 km
(This defines the scale as 0.0000054416073670992 cm / mile.)
Voyager 2: 12,000,000,000 miles --> 65,299.0 cm or 0.65 km
Proxima: 25,000,000,000,000 miles --> 136,040,184.2 cm or 1,360.40 km
Not far if I recall a few documentaries properly.
The kuiper belt is outside the solar system and then there is the shell of the Oort Cloud that Voyager won't pass through for ages. So it's been decades and we haven't even truly sent anything outside the solar system.
This is all assuming I remembered the terms correctly. Maybe someone who knows this field can comment. Point being getting to another star would take a lot of time :)
The kuiper belt is outside the solar system and then there is the shell of the Oort Cloud that Voyager won't pass through for ages. So it's been decades and we haven't even truly sent anything outside the solar system.
This is all assuming I remembered the terms correctly. Maybe someone who knows this field can comment. Point being getting to another star would take a lot of time :)
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About 120 meters.
Interstellar space is big.
Interstellar space is big.
Voyager 1 (1977) travels at 38,210 mph.
The ISS (1998) travels at 17,400 mph.
There's abundant precedent of accelerating to high speeds in space, where there's no friction with an atmosphere that slows you down and where you can use gravitational fields as sling shots.
0.3c might seem high but if you keep accelerating you will eventually reach that speed.
The ISS (1998) travels at 17,400 mph.
There's abundant precedent of accelerating to high speeds in space, where there's no friction with an atmosphere that slows you down and where you can use gravitational fields as sling shots.
0.3c might seem high but if you keep accelerating you will eventually reach that speed.
> There's abundant precedent of accelerating to high speeds in space
But there's zero precedent for slowing down once you get somewhere (in 10,000 years)
But there's zero precedent for slowing down once you get somewhere (in 10,000 years)
Why would they slow down? Fly by and beam back the results.
At 0.25c the probes would blast through the centauri system in minutes. Hardly enough time to collect data more useful than what we already can sitting here practically stationary, even if absurdly far away.
How much power is needed to beam back the results from that distance? I ask because I suppose the probes are going to be very small.
About 75,000 years away at voyager speed.
The difference is that these spacecraft will be smaller, and use light sailing as propulsion mechanism.
Which means that a ground station can keep beaming light at them causing them to accelerate.
Which means that a ground station can keep beaming light at them causing them to accelerate.
And maybe enough deceleration at the other end to drop into a large eccentric orbit ?
Since you want to take such a condescending tone about it, here we have an entire fucking article about how NASA thinks it's possible and is working on potential solutions.
Sorry if my comment came across as condescending.
However the point remains that it’s simply impossible.
My original analogy of 1.3cm versus 200km was wrong according to another commenter in fact it’s more like 1.3cm versus 1,300km - so vastly impossibly far out of the range of anything that could be conceivably be done under any plausible scenario.
However the point remains that it’s simply impossible.
My original analogy of 1.3cm versus 200km was wrong according to another commenter in fact it’s more like 1.3cm versus 1,300km - so vastly impossibly far out of the range of anything that could be conceivably be done under any plausible scenario.
True but we haven’t been further than the moon, our nearest neighbor. Unmanned missions have gone much further with success (and even returned).
Remember people said exactly the same thing about flying, and about stepping foot on the moon.
Everything is impossible until it's done.
Everything is impossible until it's done.
The comparisons don’t hold up.
It’s not simply a country we haven’t found yet with a six month sailing journey.
It’s not simply a country we haven’t found yet with a six month sailing journey.
True - we know exactly where it is, how far, what technology will be required and we have light speed communication.
The six month sailing journey sounds waaaaay more ominous.
The six month sailing journey sounds waaaaay more ominous.
yeah people died on those, entire ships lost.
I don't see a way to slow down. So they would be travelling thru that solar system at .2c. At that speed, they wouldn't be in that solar system for long.
Imagine this was Proxima Centauri doing the same mission on our solar system. Assuming that some of the swarm was on target enough to go thru the inner solar system:
Mars is ~13 light minutes from the sun. So double that for the whole diameter of the orbit, 26 light minutes. At .2c that's 130 minutes total transit time (less really unless it passes really close to the sun). So probably less than 2 hours total in the inner solar system. And that's assuming you can hit that small of a target from 4.25 light years away.
Light distance Sun-Saturn is 1.3 hours. 2.6 diameter. 13 hour transit time for most of the solar system.
You don't know where the planets actually are going to be, or were to point a camera or any other instrument, except the sun. And you have probes that weigh grams.
That's a tough problem, without considering the laser.
But I like thinking about it.
Imagine this was Proxima Centauri doing the same mission on our solar system. Assuming that some of the swarm was on target enough to go thru the inner solar system:
Mars is ~13 light minutes from the sun. So double that for the whole diameter of the orbit, 26 light minutes. At .2c that's 130 minutes total transit time (less really unless it passes really close to the sun). So probably less than 2 hours total in the inner solar system. And that's assuming you can hit that small of a target from 4.25 light years away.
Light distance Sun-Saturn is 1.3 hours. 2.6 diameter. 13 hour transit time for most of the solar system.
You don't know where the planets actually are going to be, or were to point a camera or any other instrument, except the sun. And you have probes that weigh grams.
That's a tough problem, without considering the laser.
But I like thinking about it.
lets say we did this, and we got the tiny probes up to even ~speed of light... then what are they going to do when they get there? what sensors can they carry and report back. And we wouldn't be able to slow them down, so they're going to transit through the target solar system relatively quickly (days even).
I'm a little surprised there's been no mention of Project Daedalus[1] in either the thread or the discussion.
1. https://en.wikipedia.org/wiki/Project_Daedalus
1. https://en.wikipedia.org/wiki/Project_Daedalus
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Thinking whether they could use one of the projects aiming to launch small payloads into space, sort of space trebuchets:
SpinLaunch - Developing a system that spins a payload at ultra-high speeds inside a vacuum chamber, then launches it into the sky using stored rotational energy. They claim it could launch small satellites for a fraction of the cost of traditional rockets.
Launchloop - Proposed concept of using a powerful electromagnetic accelerator called a Launchloop to fling payloads into space. It would use low-cost electricity rather than expensive rocket fuel. Still in early feasibility stage.
TAES - Developing a space trebuchet mechanism that uses centrifugal force similar to how a trebuchet launches projectiles. They're aiming to launch 6U CubeSats (10x10x30cm) to Low Earth Orbit for a relatively low cost per launch.
Rocket Lab - Makes small Electron rockets for launching 150kg payloads to LEO. Over 20 successful launches to date and helping enable more frequent smallsat launches.
Virgin Orbit - Uses a modified Boeing 747 to carry a 2-stage LauncherOne rocket to altitude, then releases and ignites to place payloads in orbit. Aims for frequent, affordable smallsat launches.
SpinLaunch - Developing a system that spins a payload at ultra-high speeds inside a vacuum chamber, then launches it into the sky using stored rotational energy. They claim it could launch small satellites for a fraction of the cost of traditional rockets.
Launchloop - Proposed concept of using a powerful electromagnetic accelerator called a Launchloop to fling payloads into space. It would use low-cost electricity rather than expensive rocket fuel. Still in early feasibility stage.
TAES - Developing a space trebuchet mechanism that uses centrifugal force similar to how a trebuchet launches projectiles. They're aiming to launch 6U CubeSats (10x10x30cm) to Low Earth Orbit for a relatively low cost per launch.
Rocket Lab - Makes small Electron rockets for launching 150kg payloads to LEO. Over 20 successful launches to date and helping enable more frequent smallsat launches.
Virgin Orbit - Uses a modified Boeing 747 to carry a 2-stage LauncherOne rocket to altitude, then releases and ignites to place payloads in orbit. Aims for frequent, affordable smallsat launches.
None of those solutions are suitable for this mission. These satellites need to be traveling a hundreds of thousand of kilometres an hour or more. Think about voyager 1 traveling at 65,000km/hr. It is still over 18,000 years before it will reach a light years distance and this mission is talking about 4 light years. So the launch really has zero importance as does getting these satellites up to massive massive speeds. Anything less then like 1million kilometres per hour is probably just too slow.
Edit: even at 1 million kilometres per hour it would still take over 4000 years to reach the full distance so really we need to be going unimaginably fast to get there.
Launching from altitude gives you very little, so does spinlaunching.
It is because it’s about speed, not altitude. Witch Spinlaunch, they plan to laumch around 5000kmph, and you need a speed of around 25000kmph to reach orbit.
In other words, they would need to use their setup to launch a rocket of a size of 1/2-3/4 of size of a falcon1 to get into orbit, and even then, unless they land the second stage, they will come out far more expensive than what SpaceX is doing.
The tech may work on moon, but even on Moon a different solution - similar to maglev - may be better, bacause there would be no issues with crazy centrifugal forces.
Anything launching from earth will require some sort of a rocket fuel (or some new laws of physics), because even if you managed to launch at the speed of 25000km/h from the ground, the payload would slow down before it left the atmosphere.
It is because it’s about speed, not altitude. Witch Spinlaunch, they plan to laumch around 5000kmph, and you need a speed of around 25000kmph to reach orbit.
In other words, they would need to use their setup to launch a rocket of a size of 1/2-3/4 of size of a falcon1 to get into orbit, and even then, unless they land the second stage, they will come out far more expensive than what SpaceX is doing.
The tech may work on moon, but even on Moon a different solution - similar to maglev - may be better, bacause there would be no issues with crazy centrifugal forces.
Anything launching from earth will require some sort of a rocket fuel (or some new laws of physics), because even if you managed to launch at the speed of 25000km/h from the ground, the payload would slow down before it left the atmosphere.
>even if you managed to launch at the speed of 25000km/h from the ground, the payload would slow down before it left the atmosphere.
Project HARP was shooting 16 inch artillery shells at 2100m/s, and they reached 180km altitude, i.e. the atmosphere was slowing it down only for 15%. While higher speeds cause higher losses, the larger payloads would benefit from decreasing surface-to-volume ratio, plus if one launches from say a plateau in Andes where atmosphere is aleady thinner, I think the losses will be similar for large payloads at speeds close to orbital.
Project HARP was shooting 16 inch artillery shells at 2100m/s, and they reached 180km altitude, i.e. the atmosphere was slowing it down only for 15%. While higher speeds cause higher losses, the larger payloads would benefit from decreasing surface-to-volume ratio, plus if one launches from say a plateau in Andes where atmosphere is aleady thinner, I think the losses will be similar for large payloads at speeds close to orbital.
Oh, nice, TIL. Good point about surface to volume ratio.
Yeah, but isn't it also a lot about the tyranny of the rocket equation? The more speed you want the more mass of fuel you need to accelerate so the more fuel you need, etc. That means if you can start your ascent at even a relatively small fraction of the final speed you need the size of your rocket can shrink substantially.
Sure, but with a system like this you still need to build for reusability of a rocket - if not then even a smaller rocket will be more expensive than what SpaceX is planning to do with Starship.
And if you're building a fully reusable rocket system, then neither size nor fuel matter as much as the simplicity and reliability of launch and landing. And here traditional rocket systems will win on Earth.
On Mars or Moon, with less gravity and atmosphere these systems will be more feasible though since they can possibly launch into orbit without rocket boosters.
And if you're building a fully reusable rocket system, then neither size nor fuel matter as much as the simplicity and reliability of launch and landing. And here traditional rocket systems will win on Earth.
On Mars or Moon, with less gravity and atmosphere these systems will be more feasible though since they can possibly launch into orbit without rocket boosters.
Do these launchers actually make sense? Maybe from the moon (obviously not for earth orbit-destined satellites, but deeper space)
What would happen if a 1g probe traveling at 10% of the speed of light hits an inhabited planet with an atmosphere? The kinetic energy is insane, but will it just burn out in the atmosphere or will it manage to hit the surface and go boom, assuming earth like atmosphere?
According to the calculator at https://www.calculatorsoup.com/calculators/physics/kinetic.p... , 1 gram traveling at 29,979,245.8 m/s has 449,377,589,368.41 J, or about 449 gigajoules.
According to a quick search, the asteroid that killed the dinosaurs had about 300 zettajoules of energy. 1 zettajoule is 1,000,000,000,000 gigajoules.
So it would be on the order of a trillionth as much energy as the Chicxulub impact.
According to a quick search, the asteroid that killed the dinosaurs had about 300 zettajoules of energy. 1 zettajoule is 1,000,000,000,000 gigajoules.
So it would be on the order of a trillionth as much energy as the Chicxulub impact.
The energy is something like 100 tonnes of TNT so a big bang but not catastrophic to the planet.
Sure but such a thing could easily be taken as an aggressive action or attack and traced back to us. I mean, if there is a technological civilization there, that is.
I love Breakthrough Starshot but this is an interesting risk to think about.
I love Breakthrough Starshot but this is an interesting risk to think about.
Would they even notice it though? Normal bolides of similar energy happen fairly frequently (see https://catalog.data.gov/dataset/fireball-and-bolide-reports for an example). And even if they did, would they interpret it as a hostile act when similar events happen naturally without ill effect? It would mean the "attacker" posses the technology to accelerate materials to appreciable fractions of c while simultaneously not knowing that the impacts wouldn't do any damage to the target.
Should we similarly be afraid of making radio broadcasts lest our intended recipients interpret our beaming of energy as a hostile act? A somewhat similar concept is actually mentioned in the novel Blindsight. You could even go full Dark Forest and say that we're a threat simply by existing all the while brazenly advertising our presence through the oxygen in the atmosphere.
Should we similarly be afraid of making radio broadcasts lest our intended recipients interpret our beaming of energy as a hostile act? A somewhat similar concept is actually mentioned in the novel Blindsight. You could even go full Dark Forest and say that we're a threat simply by existing all the while brazenly advertising our presence through the oxygen in the atmosphere.
I would like to think that a sophisticated civilization would understand what was happening.
I also giggle at the idea of a highly advanced civilization arriving at earth to tell us humans exactly what they think of someone firing a relativistic shotgun at their planet. Even if it was only loaded with bird shot.
I also giggle at the idea of a highly advanced civilization arriving at earth to tell us humans exactly what they think of someone firing a relativistic shotgun at their planet. Even if it was only loaded with bird shot.
If there were a technological civilization there we'd have heard their radio broadcasts. [sad-face] - because I wish we had. It'd be nice to have neighbours.
Interesting to think about but my gut is telling me it's not even worth planning for. It should be an infinitesimal chance of impacting a planet.
I think it's unlikely it will impact the surface because it's so small. It also depends on the material. Temperature on entry can be thousands of degrees and most materials would just vaporize
It is big but not that insane. Think about it: these probes are accelerated with a 100GW laser, they are not getting more energy. So cut the middleman and shoot that 100GW laser at the planet directly.
On Earth, we get about 1kW/m2 from the sun. So 100GW is what we get from a 100km2 patch of land. So, all the energy from the system is enough to turn night into day for an area the size of a medium sized city.
Of course, it is not a continuous beam, so it would be more like an explosion. It would be nuke-sized if it wasn't for losses, but obviously, there would be losses. But the thing is, we are not destroying planets with the energies we get from a 100GW laser.
Edit: Also, at these speeds, the probe is a bunch of high energy particles causing nuclear reactions along their way, things like chemical bonds don't make much sense. There is an XKCD What-If about relativistic object hitting earth. Not the same scale, but it may give some idea of the physics involved. https://what-if.xkcd.com/20/
On Earth, we get about 1kW/m2 from the sun. So 100GW is what we get from a 100km2 patch of land. So, all the energy from the system is enough to turn night into day for an area the size of a medium sized city.
Of course, it is not a continuous beam, so it would be more like an explosion. It would be nuke-sized if it wasn't for losses, but obviously, there would be losses. But the thing is, we are not destroying planets with the energies we get from a 100GW laser.
Edit: Also, at these speeds, the probe is a bunch of high energy particles causing nuclear reactions along their way, things like chemical bonds don't make much sense. There is an XKCD What-If about relativistic object hitting earth. Not the same scale, but it may give some idea of the physics involved. https://what-if.xkcd.com/20/
Let’s see, total surface area of 1 square km, 1,000 probes in the swarm, that’s 1,000 square meters per probe… but it can only weigh a few grams? Also it can’t be sparse because the point is to capture light energy instead of letting it pass through.
The 1km^2 figure in the article was for the receiving “antenna” on earth. It doesn’t give a figure for the size of the sails, but Breakthrough Starshot’s equivalent swarm members were going for 4m^2: https://en.wikipedia.org/wiki/Breakthrough_Starshot#Light_sa...
Could the tiny robots, at the other end, self assemble into something bigger?
They'll be far away from each other then, probably lightseconds or even lightminutes, so I'm guessing no.
How about step 1, you let us know when you have gram-scale computers, we can make some money on-planet and use that to fund the rest of your program.
The cool thing is that swarm can form a half sphere mirror halfway, slowing one probe at the center down.
Is there any plan to slow the probes or would they inspect Proxima Centauri very quickly?
I wish I could be alive when humanity’s first Dyson sphere powers up.
This is ridiculous. Set aside the (incredibly optimistic, to be charitable) thinking that is going into the acceleration of these probes. The astronavigation itself is hugely questionable, especially with probes that aren't big enough to hold the kinds of equipment necessary to detect bodies that would perturb the trajectory, let alone make adjustments after encountering these.
I don't think people realize how mind-bogglingly, incomprehensibly HUGE space is. It's BIG. Like think of the biggest thing you can comprehend, and it's not even the size of an atom in comparison to even "short" distances in space.
I don't think people realize how mind-bogglingly, incomprehensibly HUGE space is. It's BIG. Like think of the biggest thing you can comprehend, and it's not even the size of an atom in comparison to even "short" distances in space.
Something I would point out is that this is more of a conceptual proposal than something real NASA is planning on doing. This mission as described here will never happen. With that said it’s still a useful exercise because we will do space probes to Alpha Centauri at some point and doing a pretend proposal for one and solving all the problems that come up when you try to do so will help make it feasible to actually do that type of mission in the future eg. The Europa Clipper or a lot of the other space probes we’ve done.
How do they slow down?
With a big enough laser and a big enough collecting device for a reflected signal, I can imagine that communication even at such distances is possible. On the other hand I can't understand the propulsion mechanism. The acceleration is such that any device will simply be ripped apart by the immense forces. The "sail" must be both impossibly thin to even allow such high acceleration but also impossibly strong to transfer all that force to the craft itself, and if that's not enough it needs to be impossibly reflective so that the laser doesn't vaporise it instead of accelerating it. I can't see how anyone could think the concept could ever possibly work.
We can use the Sun as a focusing lense - need to place the antenna at 500+ AU behind the Sun on the line of the desired communication.
>On the other hand I can't understand the propulsion mechanism.
Yes, i also think the laser propulsion isn't the one to go, at least with the current tech. With current tech my bet would be on ion drive https://news.ycombinator.com/item?id=38445404
>On the other hand I can't understand the propulsion mechanism.
Yes, i also think the laser propulsion isn't the one to go, at least with the current tech. With current tech my bet would be on ion drive https://news.ycombinator.com/item?id=38445404
The article's title is 'NASA Selects a Wild Plan to "Swarm" Proxima Centauri With Thousands of Tiny Probes'