So where do you get yours?

> The challenges involved in sending gram-class probes to Proxima Centauri could not be more stark. They’re implicit in Kevin Parkin’s analysis of the Breakthrough Starshot system model, which ran in Acta Astronautica in 2018 (citation below). The project settled on twenty percent of the speed of light as a goal, one that would reach Proxima Centauri b well within the lifetime of researchers working on the project. The probe mass is 3.6 grams, with a 200 nanometer-thick sail some 4.1 meters in diameter. > > The paper we’ve been looking at from Marshall Eubanks (along with a number of familiar names from the Initiative for Interstellar Studies including Andreas Hein, his colleague Adam Hibberd, and Robert Kennedy) accepts the notion that these probes should be sent in great numbers, and not only to exploit the benefits of redundancy to manage losses along the way. A “swarm” approach in this case means a string of probes launched one after the other, using the proposed laser array in the Atacama desert. The exciting concept here is that these probes can reform themselves from a string into a flat, lens-shaped mesh network some 100,000 kilometers across. > > The Proxima swarm presents one challenge I hadn’t thought of. We have to be able to predict the position of Proxima b to within 10,000 kilometers at least 8.6 years before flyby – this is the time for complete information cycle between Earth, Proxima and back to Earth. Effectively, we need to figure out the planet’s velocity to a value of 1 meter per second, with a correspondingly tight angular position (0.1 microradians). > > > Although we already have Proxima b’s period (11.68 days), we need to determine its line of nodes, eccentricity, inclination and epoch, and also its perturbations by the other planets in the system. At the time of flyby, the most recent Earth update will be at least 8.5 years old. The Proxima b orbit state will need to be propagated over at least that interval to predict its position, and that prediction needs to be accuracy to the order of the swarm diameter. > > The authors suggest that a small spacecraft in Earth orbit can refine Proxima b’s position and the star’s ephemeris, but note that a later paper will dig into this further. > > In the previous post I looked at the “Time on Target” and “Velocity on Target” techniques that would make swarm coherence possible, with variations in acceleration and velocity allowing later-launched probes to reach higher speeds, but with higher drag so that as they reach the craft sent before them, they slow to match their speed. From the paper again: > > > A string of probes relying on the ToT technique only could indeed form a swarm coincident with the Proxima Centauri system, or any other arbitrary point, albeit briefly. But then absent any other forces it would quickly disperse afterwards. Post-encounter dispersion of the swarm is highly undesirable, but can be eliminated with the VoT technique by changing the attitude of the spacecraft such that the leading edge points at an angle to the flight direction, increasing the drag induced by the ISM, and slowing the faster swarm members as they approach the slower ones. Furthermore, this approach does not require substantial additional changes to the baseline BTS \[Breakthrough Starshot\] architecture. > > In other words, probes launched at different times with a difference in velocity target a point on their trajectory where the swarm can cohere, as the paper puts it. The resulting formation is then retained for the rest of the mission. The plan is to adjust the attitude of the leading probes continually as they move through the interstellar medium, which means variations in their aspect ratio and sectional density. A probe can move edge-on, for instance, or fully face-on, with variations in between. The goal is that the probes lost later in the process catch up with but do not move past the early probes. > > All this is going to take a lot of ‘smarts’ on the part of the individual probes, meaning we have to have ways for them to communicate not just with Earth but with each other. The structure of the probes discussed here is an innovation. The authors propose that key components like laser communications and computation should be concentrated, so that whereas the central disk is flat, the ‘heart of the device,’ as they put it, is concentrated in a 2-cm thickened rim around the outside of the sail disk. > > The center of the disk is optical, or as the paper puts it, ‘a thin but large-aperture phase-coherent meta-material disk of flat optics similar to a fresnel lens…’ which will be used for imaging as well as communications. > > So we have a sail moving at twenty percent of lightspeed through an incoming hydrogen flux, an interesting challenge for materials science. The authors consider both aerographene and aerographite. I had assumed these were the same material, but digging into the matter reveals that aerographene consists of a three-dimensional network of graphene sheets mixed with porous aerogel, while aerographite is a sponge-like formation of interconnected carbon nanotubes. Both offer extremely low density, so much so that the paper notes the performance of aerographene for deceleration is 104 times better than conventional mylar. Usefully, both of these materials have been synthesized in the laboratory and mass production seems feasible. > > Back to the probe’s shape, which is dictated by the needs not only of acceleration but survival of its electronics – remember that these craft must endure a laser launch that will involve at least 10,000 g’s. The raised rim layout reminds the authors of a red corpuscle as opposed to what has been envisioned up to now as a simple flat disk. The four-meter central disk contains 247 25-cm structures arranged, as the illustration shows, like a honeycomb. We’ll use this optical array for both imaging Proxima b but also returning data to Earth, and each of the arrays offers redundancy given that impacts with interstellar hydrogen will invariably create damage to some elements. > > Remember that the plan is to build an intelligent swarm, which demands laser links between the probes themselves. Making sure each probe is aware of its neighbors is crucial here, for which purpose it will use the optical transceivers around its rim. The paper calculates that this would make each probe detectable by its closest neighbor out to something close to 6,000 kilometers. The probes transmit a pulsed beacon as they scan for neighboring probes, and align to create the needed mesh network. The alignment phase is under study and will presumably factor into the NIAC work. > > The paper backs out to explain the overall strategy: > > > …our innovation is to use advances in optical clocks, mode-locked optical lasers, and network protocols to enable a swarm of widely separated small spacecraft or small flotillas of such to behave as a single distributed entity. Optical frequency and reliable picosecond timing, synchronized between Earth and Proxima b, is what underpins the capability for useful data return despite the seemingly low source power, very large space loss and low signal-to-noise ratio. > > For what is going to happen is that the optical pulses between the probes will be synchronized, meaning that despite the sharp constraints on available energy, the same signal photons are ‘squeezed’ into a smaller transmission slot, which increases the brightness of the signal. We get data rates through this brightening that could not otherwise be achieved, and we also get data from various angles and distances. On Earth, a square kilometer array of 796 ‘light buckets’ can receive the pulses. > > If we can achieve a swarm that is in communication with its members using micro-miniaturized clocks to keep operations synchronous, we can thus use all of the probes to build up a single detectable laser pulse bright enough to overcome the background light of Proxima Centauri and reach the array on Earth. The concept is ingenious and the paper so rich in analysis and conjecture that I keep going back to it, but don’t have time today to do more than cover these highlights. The analysis of enroute and approach science goals and methods alone would make for another article. But it’s probably best that I simply send you to the paper itself, one which anyone interested in interstellar mission design should download and study. > > The paper is Eubanks et al., “Swarming Proxima Centauri: Optical Communication Over Interstellar Distances,” submitted to the Breakthrough Starshot Challenge Communications Group Final Report and available online. Kevin Parkin’s invaluable analysis of Starshot is Parkin, K.L.G., “The Breakthrough Starshot system model,” Acta Astronautica 152 (2018), 370–384 (abstract / preprint).

Wondering what other hexbears are gifting their loved ones.

• For mother, a set of gardening tools and hat.
• For father, a leatherman multitool.
• For sister, an appointment with her favorite hairdresser.
• For sister, a tee shirt and tote bag from The Cure tour.

I will get nothing and deserve it.

What about you?

Excerpt > What will happen to AI is boring old capitalism. Its staying power will come in the form of replacing competent, expensive humans with crappy, cheap robots. LLMs are a pretty good advance over Markov chains, and stable diffusion can generate images which are only somewhat uncanny with sufficient manipulation of the prompt. Mediocre programmers will use GitHub Copilot to write trivial code and boilerplate for them (trivial code is tautologically uninteresting), and ML will probably remain useful for writing cover letters for you. Self-driving cars might show up Any Day Now™, which is going to be great for sci-fi enthusiasts and technocrats, but much worse in every respect than, say, building more trains. > > The biggest lasting changes from machine learning will be more like the following: > >- A reduction in the labor force for skilled creative work >- The complete elimination of humans in customer-support roles >- More convincing spam and phishing content, more scalable scams >- SEO hacking content farms dominating search results >- Book farms (both eBooks and paper) flooding the market >- AI-generated content overwhelming social media >- Widespread propaganda and astroturfing, both in politics and advertising

Excerpt from the most interesting bit: > Architecturally this is interesting. Because if we are going to have AIs living inside our apps in the future, apps will need to offer a realtime NPC API for AIs to join and collaborate – and that will look very unlike today’s app APIs. And how will we get the visual training data for AI models to connect together what the user is seeing and the machine API? Questions for the future. > > Anyway: I want to show you where I ended up. > > Here’s my dolphin NPC PartyKit sketchbook. > I posted this just today. > > You’ll see three GIFs: > > - You create a “pool” or a cursor park ("a space on a Google Docs page designated for placing your mouse cursor when you’re not actively editing the document") or (as I call it) an embassy on the whiteboard. The NPCs need somewhere to hang out when they’re idle. Then you summon your NPCs from the comms walkie-talkie on the page. > > - NPCs can accept commands! From your walkie-talkie, you can tell the poet NPC to venture out of its embassy to write a poem. So it does that, as you can see, leaving a haiku on the whiteboard, then returns home. > > - NPCs can be proactive! The painter dolphin likes to colour in stars. When you draw a star, the painter cursor ventures out of the embassy and comes and hovers nearby… “oh I can help” it says. It’s ignorable (unlike a notification), so you can ignore it or you can accept its assistance. At which point it colours the star pink for you, then goes back to base till next time. > > Check out the movies on that page. It’s all working code! I can interact with these dolphin-cursor-NPCs. Let me tell you, it is uncanny to see a machine-driven cursor. It doesn’t move right. > > Look yes it’s ridiculous, and these are woefully simple, toy interactions. > > But, but, and, I learnt a ton.

> Sometimes I talk to friends who need to use the command line, but are intimidated by it. I never really feel like I have good advice (I’ve been using the command line for too long), and so I asked some people on Mastodon: > > > if you just stopped being scared of the command line in the last year or three — what helped you? > > This list is still a bit shorter than I would like, but I’m posting it in the hopes that I can collect some more answers. There obviously isn’t one single thing that works for everyone – different people take different paths. > > I think there are three parts to getting comfortable: reducing risks, motivation and resources. I’ll start with risks, then a couple of motivations and then list some resources.

I'd add ImageMagick for image manipulation and conversion to the list. I use it to optimize jpg's which led me to learn more about bash scripting.

I've always liked having greenery around my living space but felt out of my depth. This helped.