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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
by snakeyjake 3y ago
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.
- chuckadams 3y agoIt'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.
- snakeyjake 3y agoAfter 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…
- hex4def6 3y agoI'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?
- 6d6b73 3y agoNot 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
- wombatpm 3y agoI 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?
- selecsosi 3y agoBeam 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
- jiggawatts 3y agoIt'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 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.
- kragen 3y agomost 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 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 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 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 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
- lxe 3y agoGiven 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"
- numtel 3y agoFor comparison 320km2 is about 2.5 San Franciscos
- lxe 3y agoI 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/
- bumbledraven 3y agoNeat. How did you ask it to make that? Do you mind sharing the transcript?
- lxe 3y agoHere you go! https://chat.openai.com/share/024a7117-f3d0-4a23-8186-86eeeaeab9a2 https://chat.openai.com/share/024a7117-f3d0-4a23-8186-86eeea...
- dylan604 3y agoyeah, when you look at that over the default location over London, it looks big. Moving it closer to the Western US, it looks tiny
- jchanimal 3y agoSize of a Texas ranch. Call it “reverse solar” and you might have a winner.
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- dylan604 3y agoYou 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.
- PeterisP 3y agoSo you're saying it's like the Queen's duck? https://bwiggs.com/notebook/queens-duck/ https://bwiggs.com/notebook/queens-duck/
- dylan604 3y agoThis 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.
- deleted 3y ago[deleted]
- gumby 3y ago> 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!)
- pengaru 3y ago> 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?
- gumby 3y agoSeems likely some of the tiny probes will end up in the star so I suppose the name would be appropriate :-)
- huytersd 3y ago50 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.
- mlyle 3y agoIf 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.
- poulpy123 3y agolet 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 ?
- jessriedel 3y ago> 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.
- 6d6b73 3y agoNIF'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-conditioning https://lasers.llnl.gov/about/how-nif-works/power-conditioni...
- jessriedel 3y agoPeak 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.
- andrewflnr 3y agoDo 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.
- jessriedel 3y agoNo, 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.
- ofslidingfeet 3y agoYour comment is a scam, and I despise shills.
- p1mrx 3y ago100 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.
- nynx 3y agoThe 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.