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Star Shot
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Ricardo
Posts: 15140
Joined: Dec. 14 2004
From: Washington DC
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 RE: Star Shot (in reply to RobF)
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quote:
ORIGINAL: RobF
Just when I was beginning to believe the guy he starts going on about swapping the orbits of Venus and Mars and how spiral galaxies might have been artificially formed, etc…Giant lasers beaming from the far side of the moon? Swarms of origami probes? At least he mentioned the problem of latency, but no mention of AI? WTF?? 
AI is mentioned later, called properly “machine learning algorithms” which the probes need to have in order to make a remote determination of how to aim the cameras, etc., upon arrival to the destination. About the other stuff, they were putting engineering of advanced humans into more realistic or practically achievable territory. Galaxy evolution, as referenced, has models and due to many exceptions to the models whatever he referenced was likely a serious theory. The probes we have working on other worlds are not fantasy, nor are high powered lasers. So the idea of putting the required pusher lasers on the moon there is not a joke. A swarm array of small plate sails is kids stuff to put up into orbit compared to what we have done already. That is why he was saying you do one campaign and then next year another one that follows up. The speeds are achievable, but the only thing he did not address was tiny physical debris that can’t be seen that these things will hit and be destroyed by at those speeds (since they can’t steer). Dust and rocks will be killer. But in case you didn’t realize it, this project is literally moving forward.
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CD's and transcriptions available here:
www.ricardomarlow.com
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Date Oct. 7 2023 16:53:07
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RobF
Posts: 1624
Joined: Aug. 24 2017
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RE: Star Shot (in reply to Ricardo)
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quote:
But in case you didn’t realize it, this project is literally moving forward.
I have to admit that as the talk progressed I started to lose interest but, honestly, how do they intend to move forward? Who on earth is going to allow a bunch of independents, or countries for that matter, to start shipping the materials to build giant lasers to the moon? This won’t happen until we have one world order, IMO. We can’t even sail around the world without risking WWIII over territorial rights and somehow countries are going to allow competing world powers to place powerful lasers on the moon without a fight?
I realize we’re all worried about the future of the planet and humanity and science, ingenuity, and vision are critical to our survival but guys like that remind me too much of the types satirized in “Don’t Look Up”. Smug know it alls who couldn’t hold a candle to some of the science fiction writers of the last century when it comes to being visionaries. Maybe his speaking style turned me off, but maybe it was because my BS meter started to redline when he went on about altering planetary orbits.
But, no harm, no aggro, it’s all fun. I also like the big dreams.
*edit* to be fair, it was the interviewer who brought up changing planetary orbits and he took the bait and proposed swapping Venus and Mars. Yeah…I’m watching it again…  
Here’s the link to his start-up: https://www.space-initiatives.com/
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Date Oct. 7 2023 17:56:29
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RobF
Posts: 1624
Joined: Aug. 24 2017
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RE: Star Shot (in reply to Ricardo)
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quote:
But What he said makes a lot of sense if we want this thing sending photos in our life times.
I don’t want to come across as a luddite or a contrarian, I know this is a passion for you and I’m not trying to dump on that but, after trying to watch the talk three times, then reading through the paper once, and then scanning it again, and also coming from a hardware design background, I don’t think you’re going to see this happening in your lifetime.
I removed my criticism of his start-up and searched out his paper because I want to be fair-minded. I admit there’s a lot of things he talks about that are out of my depth. I’m not a physicist. But you don’t have to be one to appreciate the operational achievements that’ll be required to make this happen. It’s not like he doesn’t realize it too, it’s just there’s a little too much sugar-coating going on for it to come across as a serious paper. The concepts are sound, but how it lines up with the reality of what is actually “do-able” is where I start to stumble. Most of what I’m about to say is based on gut reaction, and should be taken as such, but here’s my thoughts on it.
My understanding, if correct, is that upon arrival a subset of the individual modules will gather data then communicate with the rest of the swarm to coherently package it and then send it back to earth employing quasi-synchronous bursts of light sent from the swarm, which can be an array of probes 100,000’s of km in diameter. He admits phase coherency is unlikely and refers to what would likely be achievable as being “operationally” coherent. He proposes a slow bit rate to lower the noise floor and hopes that with the development of highly accurate micro clocks true phase coherence could be possible. I suspect what he’s proposing for encoding won’t make it to the final cut, but something else likely will. He is aware of the benefit of phase coherence, just admits it may not be achievable, and I think he’s on point with this.*
Similarly, the modules will have to have the intelligence to form and maintain the swarm array, process the data to determine which module(s) are master, which are slaves, manage the received data, and then to process it for transmission. That’s all cool, I’m on board with all that, these are fairly basic problems and are pretty well already solved. The limited power budget available for processing is a concern, however.
The battery technology does not exist yet in the scale required. He feels with proper funding they could develop a commercially viable solution within a decade. He estimates the development at a cost of $10^7. The timeline might be reasonable due to the enormous amount of R&D currently underway for battery technology, but unless they can piggyback on someone else’s development work, his cost estimate is out to lunch, IMO.
Now, onto the manufacturing of the modules themselves. This is to my mind the biggest stumbling block, and why I don’t think we’ll be seeing this in our lifetimes. The modules are to be four meters in diameter with a rim thickness of 20mm and an internal ‘sail’ thickness of 10mm. The entire assembly must weigh less than a gram, I believe, and to achieve that it is to be a layered structure with individual layers being extremely thin and delicate. It’s also not based upon an assembly of components but is to be a monolithic circuit manufactured using what he calls an additive process (Section 3). He also indicates the process(es) he discusses for manufacture do not exist as of yet for this scale (section 3.3 in the paper). To me, sure, it may be conceivable but, at best, it’s going to cost big bucks to get it off the ground. At present, I just don’t think this is achievable. Also, even with enormous circuit redundancy, the concern is it simply is going to be too delicate an assembly. One mishap, one bad flex and a few shorts or opens and you may or may not have a dead (or insane) probe.
Looking at the scale of the probes and their delicacy, I doubt they would survive a launch from earth, they would have to be launched from space, I would expect. But they’d also have to survive getting into space, if manufactured here, and also survive the entire pre-launch preparation process. Again, not impossible, but not easy. Probably it would be best to move the entire manufacturing process to the moon, for that matter, an enormous portion of the project would likely have to take place on the moon, that’s my gut feeling. That means scientists, engineers, etc, all living on the moon with the associated infrastructure to allow this to happen. I don’t know, in our lifetimes?
Same with the launch laser, he indicates the power required would be the equivalent of that of a small atomic bomb (~100GigaWatt). I take it that that’s per launch? Again, could happen, but the powers that be (the ones who hold the purse strings) might consider that to be a tad wasteful and perhaps political suicide to consume considering the needs of the planet. I mean, this is a research project, after all, people are going to want to know what the ROI is. So we’ll probably have to solve the energy crisis first.
I also question the power budget for transmission. Infrared or not, the light will have to be sent from another star system and he’s talking about miliiwatts of power available per module. Even with a swarm of 1,000 probes, with a transmission power budget of 4mW per probe, that’s only four Watts available per pulse for sending back the aggregate signal. I’m sure he’s crunched the numbers, but it seems a little fantastical to me.** (see postscript)
But, I’m not a physicist, and I’ve been out of the circuit design game for some time now. His dream, as is yours, is for this to happen within his lifetime. I’m pretty sure it won’t happen in mine, even in an ideal world I’m not sure it would. What he’s presented is a paper consisting of an amalgamation of possibilities, with any one component being capable of derailing the entire project. It’s not even a feasibility study, it’s outlining a cool concept and arguing that it *could* be feasible (OK, I suppose that is what a feasibility study is). I think the swarm idea has a lot of merit, it’s the scope of the project that seems to be perhaps overly ambitious.
But what do I know. I probably shouldn’t stick my neck out like this. There’s probably a hoard of physicists waiting in the wings to bash me over the head with my own ignorance and beat me into submission. Why do I do this to myself? Oh man…
P.S. I think he addressed your concerns about damage and wear by indicating the probe will fly edgewise like a Frisbee, and contain large levels of redundancy. Also, the extreme delicacy of the materials might alleviate impact damage. But it’s a real concern, not just the danger of losing electrical coherency, but also to achieve the weight requirements any circuitry will likely have to be of the smallest technology available. Then things like error correction and the like become very important, as even now memory can be corrupted by particles like muons flipping bits and the like. But, again, a lot of that is already solved. Also, part of the justification of a swarm is it has robustness just due to strength in numbers. Just send a bigger swarm if the first is too depleted during the journey.
P.P.S. Are you sure it’s this project that’s been green-lighted by NASA and not something else they do, like the lunar communications network they describe on their web page?
*this paragraph was edited later for clarity after rereading his section on clocking. The next paragraph was also edited but mainly just to make it read better. I then went through and cleaned up a couple other spots for accuracy.
** sorry, I missed this. He covers it in Section 2.1.3.6 where he says “ Electricity can be stored in a rapid-discharge ultracapacitor. By concentrating power into 1-ns pulses, the average power of each laser pulse is 4x10^4W, containing 40 micro-joules per pulse.” So, not as big a concern. I probably missed a bunch of other stuff, too, but I don’t feel like reading it again
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Date Oct. 11 2023 18:36:43
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