Hasitha Dharmasiri

All technology seems like magic once it works. The question is how do we tell if some goals are too outlandish? Here is a simple template: > Does it fall within the bounds of physics? > Will a first principles check show feasibility? - even if the odds seem slim. > Do you have a team from all disciplines needed to solve this? It takes imagination and courage to attempt breaking the norm. SuperHeavy booster catch envisioned in this video (Credit : Space.com & SpaceX) checks all three boxes. Catching the Superheavy booster sounds crazy but, at one point, so did landing a F9 booster after an orbital launch. It will be exciting and rewarding to reach this goal. #Spacex #Spacetechnology #Starship #rockets https://lnkd.in/g7yq_yiV

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I have been saying some of this for years. SpaceX customers are subsidizing Starlink. With traditional launch, costs are simple. Fixed costs (infra, labor...) + Cost of rocket / $$$ from the launch. The fixed costs get divided by launch cadence, so they are huge for 1 launch per yr, but not bad for 10/yr. With reuse, your launch cost breakdown gets funkier. You still have the fixed costs, but now you divide those by 100+ instead of 1 or 10. Add in the less quantifiable increase in competence that comes from doing this 2/wk instead of 2/yr. Now, you get to amortize the rocket over its lifetime. With that though, you have to add some stuff back in. You add refurb costs, which include spare parts and labor. Do you get better at that over time? That seems to be the case, and spare parts on a 23X flown bird certainly beats a new bird! So, I can have 1/20 rocket cost + refurb? That's only something knowable after it has been retired. So, 23? 30? We don't know yet! Of course Falcon 9 isn't fully reusable. The upper stage is expended, and I've recently heard that 2/3 of their cost is due to the upper stage expenditures. So, what does a launch cost SpaceX? At this point, it costs something like this: (Fixed costs/100+) + ((booster + fairing/20+) + (Refurb )) + (Expended upper stage) + (Propellant, which is usually 1-2% of launch cost, so it ordinarily doesn't even factor) And here's the kicker. They have no reason to lower price until a second player enters the arena at a similar price point. It would be destructive to their own profits and the absolute razor edge Margin model they are playing with Starlink, but it would also be destructive to any current or future competitors. Of course Starship will be different. The rocket will be cheaper/kg of payload, it will be fully reused and the unit lifetime will be higher.

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Interesting Autonomous car behavior. You'd think that GNSS would at least inform the car of what lane they are in and direction of traffic, while the camera/lidar would determine that all the other cars are pointed the other direction...

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Howdy y'all! Almost 7 weeks since its launch, it's time for some updates on my little personal side project -- the low-speed, 3D-printable "Modular Wind Tunnel for STEM Education": 1) The wind tunnel has this past week been featured on the Printables homepage carousel, and is now the #1 trending Printables Store download over the last 30 days. Thanks to everyone who has purchased, shared, or joined my Club. I really appreciate all the support. 2) At least 5 universities are building the STEM wind tunnel for various purposes. One aims to use it as a career-day/outreach/recruiting aid. Another is having a team of high-school interns build one, characterize it, and make improvements as their summer project. A third is building complete assemblies to donate to several high schools local to their area, and they plan to include experiments supported by CFD simulations. 3) A few teams in the internationally-popular "F1 in Schools" program have expressed interest. I'm exploring how to scale up the design to be a low-cost alternative to the Denford Air Trace tunnel offered by that program. 4) Last week, I met with the Adventure Science Center in Nashville to demo the assembled wind tunnel and its accessories. They were very impressed and excited to look for ways to work together. Initially, we may build a kit for their "I^2 Makerspace", home to several 3D-printers and STEM workshops. If that is successful, we may work to build a much larger, more-robust version to join their "Physics in Action" exhibit as a permanent installation. 5) I have submitted an abstract to present a paper on the project at AIAA SCITECH in January as a part of the Aerospace Education & STEM Outreach session. I hope to have a few great success stories to share by Jan 2025 - please share! 6) I will be exhibiting at the TN Maker Fest in Nashville in September. See you there!? 7) Work on several big upgrades continues! Stay tuned for a settling chamber design compatible with 180mm build plates, an Arduino-based lift-drag force balance, and more LabPacks! Thanks again all!

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It took me a little bit to go over the paper from anthropic but it completely blew my mind. We need more research in the interpretability/explainability space I encourage you to take a deep dive if you haven't! There are so many good things in here that summarizing doesnt make it justice, but as a summary: Sparse Autoencoders: Trained SAEs to decompose model activations, revealing interpretable features that explain the model's behavior. Feature Analysis: Discovered fascinating features like the Golden Gate Bridge, brain sciences, and even safety-relevant features like bias, sycophancy, and deception. Scalability: Demonstrated that these methods can scale effectively, providing insights into larger models' internal workings. But just read it!

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Stupid idea. I am an electrical engineer, I was with Nasa as a EE for three decades. In 2010 I helped a team design and build a moon and Mars vehicle prototype, it was the most advanced vehicle on earth, and electrical vehicle. I was also involved in high powered systems, robotics and simulation. First there is not enough infrastructure to support or sustain Massive use of electrical vehicles at this time. Second the technology and motors and batteries that are efficient, cost-effective, and safe is not here yet. The best possible alternative is to gradually over the next generation existing vehicles to use natural gas, and new vehicles, the option to run off of natural gas or gasoline, and for natural gas to be provided at gas stations. Then during this time, the development of motors and batteries as well as infrastructure can commence until the next generation. Then a gradual implementation of electricity at gas stations as infrastructure is built. The ideal car now is to have one that runs off of both natural gas and, gasoline as a electrical hybrid. It will get better, gas, mileage, and utilizing natural gas as it is installed in gas stations will help clean up the environment. This is political. echttps://lnkd.in/gz2QCjv9

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My new book is still a #1 New Release on Amazon. I think the chapters on "make your robot a digital assistant" and "Give your robot an artificial personality" are pretty interesting. (and then there are knock-knock jokes). There is only one equation in the book -- see if you can find it!

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For those interested in space, this is the thing to do: Someone who consults with SpaceX/NASA/etc. was asking me how to use "AI" to remove debris from space. I told him to use the big vacuum cleaner in the sky. That was at the Post-Industrial Institute 2024 conference. This one will be more useful for cleaning up items in geosynchronous orbit:

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Here’s something that caught my attention. Now, I’m used to graphical inages not quite getting the engineering correct. The image is of a potential spacewalk on a future SpaceX (non-NASA) mission. It looks like this dude is egressing the spacecraft in their launch-entry pressure suit, which would be a bad idea. Evidently, SpaceX has taken their launch-entry suit and modified them for EVA, with the intention of improving mobility compared with historical EVA suits. I think that endeavor is fine and applaud SpaceX for pushing the envelope. It should be noted, however, that spacewalking suits are rigid for a reason. Take the old “pumpkin suit” that Shuttle astronauts used to wear for launch. Sure, they were designed to hold pressure in the event the crew cabin lost pressure, but they were not designed for EVA. Space walking requires protection from swings of temperature from 250 deg F to -250 def F. They also protect the occupant from radiation. But most importantly, they offer astronauts protection from the myriad of hyper velocity particles zipping around in space. Think about immersing oneself into a barrage of bullets and you get the idea. Mobility is important. Useful work needs to be performed on spacewalks. But survival is important too. Spacesuit are compromises between the two.

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An interesting but, common problem came up recently. I received a call from an operations engineer who was dealing with an assembly problem. The problem was: the coordination holes between four parts wouldn't line up. I pulled up the assembly model and listened to the engineer explain the problem. After the explanation we reviewed the parts and the assembly's GD&T. Looking for anything that would cause the misalignment condition, within the design. Since nothing in the design or GD&T seemed to be at fault. We moved on to the assembly tooling. The tool design and tooling GD&T were also working as designed. So next was the assembly process. The assembly process was very straight forward in approach and seemed to make sense. So, why didn't the coordination holes line up? It turns out that there was a disconnect between part designer's assembly approach and the tool designer's assembly approach. The designer planned for the coordination holes to align the parts and the tool designer planned for the part edges to be the locating features. They both had different views on how the assembly requirements would be achieved. The two different assembly approaches were actually fighting against one another. It turns out that the coordination holes misalignment was caused by the tool's part locating surfaces. This often happens when tool designers are given expected or preliminary designs. The tool designers can work months ahead of part designers because of the long lead times for tooling. The tool designers selection of datums and locating features often are different from the final assembly design. It can be the case that the design engineer doesn't look at the tool design or some other reason for the disconnect. In this case the tool designer had designed the tool so that the finished assembly would not exceed the mating opening. The tool designer had designed the tool to represent the next assembly. The tool design was configured to push all the variation to the inside where the slips planes could absorb the #manufacturing variation. The assembly designer's configuration was pushing all the variability from the inside out. The assembly designer's configuration would have caused fit problems at the assembly's mating surfaces. Taking as individual units: parts, assembly and tooling you could be forgiven for struggling to understand the problem. When dealing with assembly problems it's always a good idea to determine in which direction the manufacturing variation will be absorbed. Tooling should represent the next assembly's locating features or critical requirements. Assembly designs should determine, during #tolerance #analysis, the best locations for slip planes in order to meet requirements. It works best when all parties are in agreement on placement of slips planes and locating features.

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Tesla is one tech topic that has unconditional support. No matter how hard you point out some defects in it, people just love red cars. When I first began sharing my Tesla observations, people have been telling me that the info must be coming from Elon Musk haters. They might be right, as Tesla has been experiencing resentment after the hostile and rough takeover of Twitter. But, there are some simple truths that are hard to miss. Like pointing out the fact that Tesla experiences routine problems that have been solved by carmakers for decades now. Like the front wheel falling off, this and that common part not working as intended, etc. A dear friend shared with me that the Tesla he drove had water leaking from the roof when driving in the rain which left his documents wet. I mean, this is a solved problem. I am not encouraged to buy the bleeding edge of cars for my patience to be massacred by routine, casual, ordinary, dumb issues. Even people who encountered some Tesla issues are quick to defend Musk's cow. Maybe this issue that one other person reported was not exactly like that. Maybe this did not happen or it happened this other way. How did we get to this point? Maybe because they popularised novel features the right way? Maybe a lot of engineering went into it? Maybe the feeling is great when driving? Maybe. There are lots of reasons to love Tesla, but, when it's flawed, it's flawed. Love is blind. Red love blinds.

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My friend Erik Herzog introduced me today to the idea of Brownfield vs. Greenfield. No, that’s not a lawsuit. I’m not sure where I’ve been hiding, but the terminology was new to me. In essence, a brownfield is an existing capability which is built upon. Think of it as an upgrade. Alternatively, a greenfield is a brand new development, started from scratch. The idea makes perfect sense to me. The requisite skills—technical, management, and leadership—are different between the two. What’s more, transitioning from a brownfield mentality to a greenfield one can be quite the paradigm change, which is what Erik asked me to think about in terms of systems engineering and technical leadership. I think I have a few examples to offer from my NASA experience. What’s your experience???

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BAD BUBBLES: AI, AM, Tulips, and Real Estate. As discussed in the interview below, AI could be the next big bubble to burst, taking down hyperinflated stock market valuations. It’s not the first, nor will it be the last, of the big bubbles bursting. Why? Greed. From “Tulip Mania” in the 1600s, the “dot com bubble” of 2000, and the real estate bubble of 2007, all bubbles are fueled by massive greed. When Gordon Gecko famously stated “Greed, for lack of a better word, is good,” he was wrong. Today, we have three bubbles, the AI bubble, the residential real estate bubble, and the additive manufacturing (AM) bubble. All three are overdue for a massive correction. All three are artificially inflated. In materials technology, the Additive Manufacturing bubble, also known as 3D printing, has been sucking up massive amounts of capital, to the detriment of other worthy technologies. There’s nothing wrong with 3D printing, other than the hype. It’s a tool and nothing more. It’s actually a very good tool for some types of materials, challenging for others, and impossible for certain classes of materials. I’ve been approached many times regarding ceramic matrix composites (CMCs) and 3D printing. Ironically, 3D printing isn’t amenable to composites with 3D continuous fiber architectures (like most of my technologies). The problem is that investment is usually a zero-sum game.  In short, great materials aren’t getting investment dollars because they can’t be made by 3D printing approaches. This is a missed opportunity. All bubbles are bad. They suck up massive capital while they are being inflated. They wipe out massive amounts of capital when they burst. Many people and businesses are hurt by bubbles, even when they have nothing directly to do with the bubble itself. Collateral damage. Bubbles bad!

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I love ❤️ #space, and I worry that talk and headlines like this do the #spaceindustry a disservice. The idea of SpaceX "building 1 Starship Megarocket each and every day and launching 10 times a day" anytime soon is certainly only aspirational 🙄. This is not in any way discounting the improvements in Starship over its recent tests or the achievements of the engineers and other workers behind it. Instead, let's talk about #economics or, more specifically, in this case, about supply and demand. Currently, SpaceX has a situation where they meet demand for launch. This demand comes from #NASA, #SpaceForce, other DoD entities, and commercial. After using the Falcon 9 for paying customers, they can use the room onboard left, or on the next trip when it's reused, to deliver their LEO-based internet service Starlink cheaply. The supply and demand for Starlink is separate from launch, and the business model (I believe it's real estate) is a topic for another time, but it's a line of business and essential to point out. Thus far, SpaceX has been a company since 2002 and has turned its first profit only recently in one quarter. The profit was $55M in 1Q2023—some report it's currently worth $200B. The private company valuation is, according to a secondary sale late last year, $180B 💰. The previous funding round also last year, but earlier, led by Andreessen Horowitz, had a valuation of $137B. These are not public stock values decided by large numbers of participants on an exchange, so keep that in mind. Also, remember that at $200B, that's what bankers call a megacap alongside the valuations of Coke, Costco, Toyota, and Pfizer. SpaceX, however, does not have paying customers with demand for Mars 🔴 today. Megacap companies might go #zombiecompany status with no profits for several quarters, sometimes adding to debts, but historically this isn't sustainable for long. SpaceX, only recently finding a profitable quarter, would be unlikely to turn from solid demand for LEO to provide supply for Mars logistics. Which firms in The Space Economy today are sending out strong demand signals for these types of trips? And to the best of my knowledge, what demand may exist is not anywhere near the amount needed to warrant the supply Elon is talking about. It's not that I don't want astronauts to go to Mars. Believe me, I do! We just have a lot of other work to do first with the space economy in Cislunar first before the demand is great enough and the profits available for a private company to go. What do you think? -GSP- #5ir #spaceeconomy

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Thanks to Ron F. from General Atomics' Electromagnetics Division for inviting me to opine on the challenges and opportunities of space nuclear power and propulsion. As it turns out, we have quite a bit of both. Opportunities first. I've said it before but it's worth repeating: Elon and his superb team at SpaceX have dismantled the LEO bottleneck. And that has opened the door to innovations of every kind - at least in LEO. But what it's really done is enable us to envision how we will go to (and play in) higher orbits, offering us a chance to define what sort of infrastructure we will build the future space economy *on*. The future is not LEO - it's the entire solar system. So: It won't be chemistry or solar power that get us moving, not if we're serious about creating a gold rush to orbit. Both are too constrained and deficient (i.e., insufficiently energy- and power-dense) to rapidly and efficiently connect the dots in cislunar space, and provide the megawatts on demand we know we'll need, whether the use case is civil, commercial, or defense. That leaves us with nuclear - and it's going to be fission for awhile, despite noteworthy quantities of money flowing into fusion. We can make this work - but we have to get to orbit and prove ourselves now. If we don't? Well, sunk cost is very real (see SLS). If you have it, you use it - even if it doesn't make sense. Let's make sure that what we put on orbit makes sense - commercial sense, defense sense, civil sense. Challenges? Well, we're all capital-intensive plays with some uncertainty in our regulatory story and that combo tends to scare the 💩 out of most private investors. I'd love to be introduced to any visionary folks out there with some discretionary dollars who share my passion for the space gold rush and want to find a way to get involved that gets us out and moving during our lifetimes - while we can have some fun. We can do this. 🚀 https://lnkd.in/ezq6yv_G

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Do you ever wonder why the US launches rockets from Florida? There's a result from orbital mechanics that tells you that launching from a given latitude gives you the best access to orbits of inclinations above that latitude. Basically, the closer your launch site is to the equator, the better access to different orbits you have, so you want to be as far south (in the northern hemisphere) as possible. It's also more efficient to launch to the east. Getting to orbit is all about building up speed relative to the center of the earth, and it turns out the ground is moving relative to the center of the earth. When you launch to the west you have to spend energy going against the rotation of the earth. Launching to the east gives you an extra boost. That puts your desired launch location in a place that's both in the south, and that lets you easily launch toward the east. In the US, safety of civilian populations is a major concern. Parts fall off of rockets both accidentally and by design. In an emergency, the entire rocket may come down. In general, it's safer for these parts to fall in the ocean than on land. That's why in the US, our premier launch facilities are located in Florida, which is both to the south and has a vast range of ocean to its east. In China, the calculus doesn't always include civilian safety. We've seen this a number of times in the past, but rarely as dramatically as the recent video of a Long March booster segment falling on a village, trailing orange smoke behind. Not only is there a risk of death, damage, fires, etc. from this debris, but some of the propellants used in these systems are toxic. In today's world where everyone has a camera on them at all times and events like this can go viral, I wonder how long it will be until some policy changes reduce the risk of this happening in the future. #rocket #launch #China #debris #safety https://lnkd.in/edN_6w-u

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https://lnkd.in/gBRYMz8x One of my favorite radio shows, Marketplace, did a great special yesterday on amorphous metals for use in transformers. The story starts at 11:30 on the April 22nd episode, called "A new spin on the yard sale." To paraphrase the story, to meet climate goals, energy savings is needed, including in transformers. Last year, the Department of Energy proposed using amorphous steel as replacements for transformers. For some 75 years, transformers have been made with grain-oriented-electric steel. The efficiency of amorphous steel is much better, however, according to Ames National Laboratory. The electric steel in a transformer is rolled into very thin sheets that allow it to conduct electricity more efficiently. The amorphous steel is naturally thin (30% thinner than electrical steel because it is melt spun), which makes it more efficient. That means less energy lost when electricity moves through the transformer. Unfortunately, amorphous steel is only produced at one supplier, Metglas of South Carolina. Sourcing a new transformer can take a few years and could be longer if all transformers were required to switch. Conventional steel workers are angry about potential job loss due to the proposed rules. The efficiency requirements were walked back so that only 25% of new transformers will be required to be made from amorphous metals. This will reduce CO2 emission by 85 million metric tons over 30 years. It was a very interesting story about economics, green technology, sourcing, and materials science and I think Marketplace did a great job with a very nuanced subject matter. Clearly, the amorphous metal transformers are better, but the technology to mass produce the melt-spun ribbon is difficult to replicate and manufactured by only a few suppliers, who protect their trade secrets vigorously. Requiring new technologies that are measurably better in terms of CO2 reduction is good for the climate but comes with issues such as supply chain and loss of business for heritage technologies. This is the typical tradeoff between economics and regulations when it comes to adoption of new technologies. It would be preferable to see demand drive the shift to green technologies, like solar, for example, and not regulations but sometimes regulations are needed to move the needle on adoption, as long as it’s done with care for possible job losses.

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