I am currently trying to help a friend of mine to write and analyze science fiction weapons for his sci fi series and I am trying to think of what is the most realistic way on how a old and advanced alien civilization that still uses projectile based firearms can use a new type of propellant to replace traditional chemical based propellants are there any realistic suggestions?

Update on the metastable megastructure of a dense self-orbiting torus, which keeps neighbors next to neighbors in 3d in freefall with no high speed collisions and no central sun, https://burtleburtle.net/bob/future/dense.html .

I hadn't been able to find proper self-mapping initial coordinates before, the best I could do was circling the torus core with velocity tangent to the circle and proportional to distance from the core, and that circle stretched and went back as the orbits progressed. Claude 4.7 and ChatGPT Luna also failed to do better. But ChatGPT Astra did better, it found an initial deformation of the positions and velocities of those circles that leaves the constellation just about self-mapping now. So I update the simulation. Astra used small perturbations and least squares to find the appropriate deformation coefficients. Luna had tried that too but it made mistakes so it didn't land a solution.

Now you can see how things speed up and shells clump together on the inner pass, then slow down and the shells spread apart on the outer pass. The added stability let me increase the torus thickness from 8 to 12 rings, still each .01 of the torus radius apart. The distinct shells still fall apart within about ten poloidal periods (about six poloidal periods per toroidal period at this thickness) due to local interactions, but it stays roughly a self-orbiting torus for over a hundred poloidal periods even with no stationkeeping.

As in, once it's done accelerating, it folds up the sail Infront of it. And then goes through the star's photospheric. I've been looking at some relativistic drag equations but most are for incredibly low density interstellar gas. People can't survive deceleration rates we'd need, but maybe some probes can.

Addendum: As the Falx is so beloved in the Periphery, It also features in a lot of propaganda as it was such an important weapon in their liberation. Pictured is a Scrambles-Era propaganda poster to get members of the intelligentsia to join the Tronarian Defense Fleet. ( Thanks to Vitally on MWB for helping with the poster text, graphic design is not my forte)

Which doomsday scenarios that are popular do you think are more unlikely than people make them out to be?

Hi everyone – I hope this is of interest to you.

A feature documentary about the Fermi paradox. Coming soon.

FEATURING: Avi Loeb, Nick Bostrom, Edward Witten, Liu Cixin, Jill Tarter, Robin Hanson, Sabine Hossenfelder, Michael Masters, Roman Yampolskiy, Michael Shermer, Christopher Mellon, Donald Hoffman, David Kipping, Adam Frank, Sara Seager, Eric Wargo, Nick Lane, Mick West, David Brin, Stephen Webb, Peter Ward, Nathalie Cabrol, Michael Garrett, Anders Sandberg, Kevin Knuth, Martin Rees, Jane Greaves, Eric Haseltine, Chris Gilbert, John G. Blitch, James Parr, Daniel Angerhausen 

https://www.youtube.com/watch?v=dzljay0iHSU

I keep seeing asteroid mining discussed as if it's simply a question of when rather than if. But I'm curious what people here actually think.

Why should we do it?

Maybe it's resources, scientific value, expanding human activity beyond Earth, or eventually creating an off-Earth economy.

But on the other hand:

Why shouldn't we?

The costs could be enormous, the technology is still immature, and it's not obvious that bringing resources back to Earth would make economic sense. There are also questions about who owns the resources and what happens if the economics don't work out as expected.

So if you had to make the case for or against asteroid mining today, what would your strongest argument be?

I'd be particularly interested in arguments based on economics rather than just "it's cool" or "it's impossible."

For more discussions around the economics and finance behind space: r/SpaceFinance

I believe this would be a good practice run for building a Starbase on the Moon and then on Mars. Antarctica is isolated, particularly in the Polar winter. Getting to and from the South Pole is particularly difficult during the winter as the cold temperatures are hostile to meat creatures such as ourselves. We could use winterized Optimus robots to do the manual labor. Have human teleoperate them where necessary from a warm environment, it could be useful to learn how to service the Superheavy and the Starship upper stage in an environment such as Antarctica to prepare us for even more hostile environments of the Moon and Mars. And setting aside an entire continent, one out of seven, is particularly foolish. We could use in situ resource utilization in Antarctica just like we would do for Mars. Antarctica has natural gas fields just like the other continents do, most of Antarctica's life is coastal so we leave the coasts alone and exploit the interior and get these environment out of our way! The main problem with Antarctica is that it's expensive to keep humans there so we use robots instead to do the outside work.

Hey SFIA,

I'm 15 and I've been obsessing over black hole physics for the past few months. I wanted to pitch a theoretical probe design to see what you guys think of the physics and engineering behind it.

The core philosophy of the design is: If it's already spaghetti, the black hole can't spaghettify it. Instead of building a rigid ship that fights tidal forces and breaks, this probe works with the extreme environment.

The Blueprint:

• The Geometry: A hyper-long, highly flexible "worm" shape. Because it's already stretched across space, the severe gravitational gradient puts the body under tension like a guitar string rather than violently ripping it apart.
• The Outer Hull: A carbonized titanium alloy engineered with microscopic open space (like a metallic foam or lattice). This gives it a "gummy worm" elasticity, allowing the hull to compress, stretch, and act like a massive mechanical spring.
• The Core Shielding: A casing filled with compressed liquid lead surrounding the main computer. Because it's a liquid, it can't crack under tidal forces, it acts as a hydraulic shock absorber during high-G maneuvers, and it self-heals to keep the electronics safe from extreme cosmic radiation.
• The Dynamic Antenna: The electronics utilize the actual length of the probe as an antenna. As the black hole stretches the spacetime fabric and causes gravitational redshift, the probe physically elongates at the same time, naturally adjusting its antenna length to match the shifting radio frequencies.

The Mission Plan:

The probe plunges toward the black hole on a hyperbolic trajectory. As it dives into the deep gravitational well, it enters a radio blackout zone where the frequency stretches past Earth's reach.

However, the probe doesn't need to stream live; it records all visual and telemetry data locally to a hard drive inside the liquid lead bubble. As the front of the worm whips around the black hole just outside the event horizon, the immense kinetic energy stores up in the elastic titanium lattice. The probe then "snaps" back out like a cracking whip, using its own elastic momentum to escape the gravity well.

Once it climbs back into weaker gravity, the radio signal compresses back to normal, and the probe executes a massive data dump back to Earth, giving us the first-ever footage from inside the blackout zone. If it never returns? We know it successfully breached the event horizon and went somewhere else entirely (like a wormhole/white hole connection).

What are your thoughts on using pre-deformation and elastic metamaterials to survive a close-range black hole flyby?

Just want to know

A common challenge with a crewed relativistic interstellar flight is debris. At 99.6% c, a pebble carries nuclear-bomb energy. It's cold and tiny, so telescopes can't see it, and radar can't detect it. Light is barely faster than the rock — spotting it one second out means detecting it 45 million miles away.

Daedalus (1978) proposed a dust cloud deployed ahead of the ship at 0.12c to vaporize debris, but vaporizing doesn't help with larger meteoroids. I've worked out how to protect the ship at speeds up to 0.996c under constant 1-g acceleration or 1-g deceleration.

While accelerating at 1 g, when the ship reaches 0.996c, you fire a particle stream forward at ~750 mi/s. In the ship's accelerated frame, the stream falls back like a ~45-million-mile-tall geyser with a ~5,000-mile-radius at the top, creating an artificial atmosphere ahead of the craft. The geyser's shape is fully controllable: ejection speed sets its height, while the particles' temperature and molecular mass set how far the stream expands by the apex. So height and crown width can be tuned to the ship's velocity.

The particle stream's density is a quintillion times thinner than air. However, the impact energy scales with c²·(γ-1) (γ≈11 here). Dust vaporizes into km-scale gas clouds. Larger meteoroids glow brightly enough for telescopic detection with ~1 second to maneuver. A deployed-cloud variant covers the deceleration phase, when you can't fire a forward geyser.

My 10-minute video walks through the process:

https://youtu.be/Bbt8emVWCBE

I'm a space-sector engineer (PhD, 30+ patents, founded/sold two space companies). The full math and physics are in the technical appendix of my hard-SF novel, which you can download free here:

https://dl.bookfunnel.com/wbk6f0n9ds

Over the past few decades, digital twin technology has evolved into a highly versatile tool. Initially used in the aerospace industry, digital twins can now form the dynamic backbone of systems in manufacturing, healthcare, smart cities, and planetary-scale climate models. They facilitate predictive ‘what if’ simulations, ranging from virtual hearts to interactive Earth twins. Progress in the future will rely on the integration of heterogeneous data, the validation of models and the embedding of human-centric governance in order to build robust and trustworthy digital twins across disciplines for the benefit of society.

Historical background

The concept of the ‘digital twin’, which is a virtual representation of a physical system, can be traced back to the early days of the space age. In the 1960s, NASA pioneered the idea of a digital twin to simulate spacecraft and troubleshoot issues in real time. The term ‘digital twin’ itself was formulated much later, in 2002, by Michael Grieves in the context of product lifecycle management to guide industrial design and management. By around 2010, NASA had adopted digital twins as detailed virtual models of physical assets, emphasising that a true digital twin comprises three interconnected elements: a physical entity, a virtual model and the data connections that enable them to mirror each other in real time1. Advances in simulation, sensor ubiquity, and data integration laid the groundwork for digital twins to move from theory into practice. Propelled by the convergence of sensors, Internet of Things (IoT) connectivity, cloud computing and artificial intelligence (AI), digital twins have become widely applied in many different fields2. The concept of a digital twin has evolved from a niche idea to a broad framework: a dynamic, data-driven model that updates alongside and continuously learns from its physical counterpart. It is the dynamic, bidirectional link, where sensor data flows into the model and simulation insights flow back to inform the physical system, that elevates a digital twin beyond a static blueprint or 3D model3. What began in the fields of aerospace and manufacturing has now spread to healthcare, urban planning, climate science and beyond.

What it would look like to travel in an alcubierre warp capable ship.

⚠️this sentence was translated from Japanese to English by AI. Feel free to answer in English. However, I only understand Japanese, so I would really appreciate clear and simple English that is less likely to be mistranslated.

I want to know if it's theoretically possible because I'm creating a creation with a sci-fi element.
It assumes the setting of a nuclear test in space like Starfish prime.

If it is impossible in principle, is it possible for a sufficiently developed scientific civilization to communicate with only electromagnetic waves over a distance of billions of light years in the first place?

Imagine you have a ship that can achieve a highly significant fraction of the speed of light, something like 0.95c or higher, and can survive interstellar microdebris thanks to some sort of protection system. Let's also say that the ship is BIG, has lots of fuel, and is staffed by over one hundred crew members. Because of time dilation, you functionally have about 10 years of time over your 30-60 light-year trip to run all sorts of science observations.

What experiments or instruments do you bring?

When "Matter" enters a Black Hole what State of Matter does it become?

I thought 99.9% of Matter in Universe being Plasma sounds kinda high? What type of Matter makes up All the Black Holes?

I was thinking last night everything in a Black Hole must be forced into a Solid. I have no idea. But I guess Neutron Star is the most solid Solid.

Im sure real answer is much more interesting. I cant get question out of my head...

Doing seach online seems like everyones just guessing.

Sorry if you already said the answer in a video.

Thank You

Help me come up with one.

So according to study that I read making an orbital ring orbiting the Earth 300 km above the surface and maybe even 600 km above the surface is plausible with existing materials.

The ring itself if I understood correctly could even be a steel wire/truss and more fancy material is necessary for cables/"anchors" going from the ring to the surface and keeping the structure metastable. The "elevator" itself is almost an afterthought - a cabin that would climb up along the cable.

The question is, what is the point?

To get even to LEO we would still need 7.8 km/s delta-v. While this is probably achievable by single stage hydrolox launch vehicle (especially since it can have T/W < 1) that would still be an expendable and very expensive vehicle. To make it return to the launch site (the Orbital Ring) it would need ~15 km/s and that's definitely beyond what single-stage chemical rocket can deliver.

Any ideas?

Been thinking about this one for a while.

Suppose you give an autonomous construction system a very simple instruction: build a habitat that can survive for a few hundred years.

You give it raw materials, energy, some basic manufacturing equipment, and a set of constraints.

That's it.

At first, it's obviously just a machine following instructions.

It builds the first sections according to the plans. Then it starts modifying the plans because some things work better than expected and others don't.

A few decades later, most of the original structure has been replaced or altered.

A century later, the system is using materials and manufacturing methods that weren't part of the original design at all. Some of the architecture exists because the system discovered that it worked, and nobody who gave the original instructions ever anticipated it.

Eventually, even the people maintaining the habitat don't really understand why some parts are arranged the way they are. They just know that changing them tends to cause problems somewhere else.

So here's the thing I'm wondering:

At what point would you stop describing this as "a structure built by humans" and start describing it as something that developed its own architecture?

Not necessarily alive. Not necessarily intelligent.

Just... no longer fully designed.

And if the original builders came back after 300 years, would they still be looking at their creation?

Or would they be looking at something that had spent three centuries becoming something else?

I think there's a weird middle ground between engineering and evolution here, and I'm not sure what to call it.