AckSed

Presumably they would have a monstrous megastructure of a space telescope that could resolve planetary details. The JWST is already discovering atmospheric compositions of large exoplanets, so the construction of a lower-tech, mass-produced cluster of 10m telescopes, with free-flying coronagraphs to block out the light of whichever star these people are being sent towards (a technique to spot any planets orbiting it), would be a neat prologue: We have found Earthlike planets all over the sky. Let's go check them out! Concerning the spaceship, I have always been a fan of solar sails and propellantless propulsion. You have routine travel between Jupiter/Saturn and Earth, presumably ships fitted with a drive to do this in a reasonable amount of time and maybe you have a decent in-space construction industry. The "photonic railway" is a concept I love, because it frees you from the tyranny of the rocket equation and gives you decent performance, but also requires massive lasers constructed in space or on airless moons, and brave explorers to venture out to set it up. I outline it here: Presumably a beaming station set up in orbit around Jupiter would get these scout-ships up to speed, but they'd then have to slow down at their destination. If that's not enough, we could go for a sun-grazing solar sail. https://forum.nasaspaceflight.com/index.php?topic=58581.msg2485032#msg2485032 But maybe you don't want to fly around the Sun. Orion's Arm is a hard SF universe with its own encyclopaedia. Its list of ships should provide inspiration. Broadly, if you have cracked reliable fusion that does not emit neutrons, or have a way to get around the radiation they emit, then you can live damn near everywhere you can find fusion fuel (deuterium, helium-3, lithium-6 and so on). If you want to slow down from high percentages of lightspeed, deploy a magnetic sail. The Barnard Banger uses the concept of the "wilderness Orion": gathering fusion fuel and light metals from icy moons or Oort cloud comets, to make small nuclear bombs that explode behind it. The ice, formed into a block in front, also serves as particle and radiation protection, since the ship accelerates to a low percentage of lightspeed and any dust particle hits with the force of a grenade at those energies.

Haven Demo (testbed satellite for most of the Haven systems) approaching completion, ready for launch this month:

Lightning on Earth can produce antimatter (positrons), and then X-rays and gamma rays when they annihilate electrons, through the radioactive decay of isotopes of oxygen and nitrogen. The isotopes are themselves produced by gamma rays. The trouble is, we don't know where these come from. Gamma-ray glows and downward-pointing Terrestrial Gamma-Ray Flashes have been measured with energies in ranges of 1-40 MeV - up to about the energy of a linear accelerator in a hospital. But there shouldn't be enough energy density or length in a thundercloud to cause them in the first place. The gamma rays only happen in about 1 in 10 thunderstorms on Earth as it is. The best hypothesis so far is that the electric fields inside a thundercloud may accelerate electrons to relativistic energies, which strip off more electrons, which finally emit bremsstrahlung gamma rays as they interact with ambient atmospheric nuclei. However, not all the gamma-ray glows (ramp-ups in emission before a strike) happen with TGFs (flashes produced in a strike) and the opposite - TGFs without ramp-up - is also true. So there's still more to learn. Edit: More recent research points to special types of lightning strikes: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024GL113194

External link: https://arstechnica.com/space/2025/04/spinlaunch-yes-the-centrifuge-rocket-company-is-making-a-hard-pivot-to-satellites/ Yeah, this is definitely a case of following the money. With relatively cheap launch and small satellites becoming increasingly capable, it seems like the way to go.

No (unintentional) boom. Next stop, Karman Line!

This, this and thrice this. Airily saying that it doesn't matter gets to me. The whole point of the scientific method is to have rigor in your observations of reality such that your predictions can be reproduced; it's skinning the hide of science to cover your bamboo framework and leaving the soul. We don't want a stiff, dead, taxidermied pseudoscientific animal with glowy lights, we want a Frankenstein's monster that has some semblance of agreement with life and the world, one that can actually speak to us. I do write (fanfic, but still) and you can speak to human experiences and be successful, because we do like to hear about ourselves. The very best science-fiction authors allowed what they know about the world to drive their stories, to let the environment warp their characters because they were speculating via the scientific method. E.g. Robert Heinlein's The Menace From Earth frankly gets some important details wrong, and its appeal is in the very human characters, but it is still true that with Earth-normal strength and a bit more air-pressure humans on the Moon wearing wings and a tail can fly under their own power. It ignited my imagination and drove me to write my own short story set on the Moon, based upon what we know now. You say people don't care? I care. I'm people. Spacescifi, please post examples of your stories, so I can see where you have put the effort in and the advice we have given. I don't like feeling like we're being used more as an oracle by the lazy, or worse - market research.

Remember all those renderings and drawings of rovers with manipulator arms? They may be coming to life: https://gitai.tech/2025/03/31/gitai-awarded-jaxa-contract-for-concept-study-of-robotic-arm-for-crewed-pressurized-lunar-rover/

That they actually had to turn it on and off again while docking is definitely hair-raising.

More details of Hera's Mars flyby, including testing of new autonomous navigation software: https://www.esa.int/Space_Safety/Hera/Hera_asteroid_mission_tested_self-driving_technique_at_Mars

Booster touchdown. MVac shutdown. Zero-gravity polar bear toy deployed. Second stage separated.

3 minutes! Lightning in background makes this dramatic. Liftoff, MaxQ and MVac chill. Stage2 ignition and nominal trajectory

15 minutes.

Weather front is moving away to the East. Prop load started. Showing off a portable X-ray plus digital X-ray plate that'll be used in-flight.

Official stream is up, with Insprucker presenting: https://www.spacex.com/launches/mission/?missionId=fram2 Interesting that all of them have a connection to polar expeditions.

1 hour 30 minutes. More details: https://orbitaltoday.com/2025/03/30/next-private-spacex-mission-to-push-human-orbit-limits-like-never-before/ For the Fram2 polar spaceflight, astronaut & filmmaker Jannike Mikkelsen will use a reMarkable Paper Pro tablet, O2XR previs, RED V-Raptor 8K cameras, Canon R5C cameras, and a range of Canon RF lenses.

2 hours and the rain is coming down. Ah, Chun Wang just posted a clip of them closing the hatch. Looks like it's still go for now.

No official word, but the astronauts haven't gone to the pad yet and the weather's getting worse. The T-zero is still counting down, though.

NSF stream showing a large stormcloud with lightning, but not over the pad.

Interesting ideas. Dry ice as explosive, I don't see, but if you're making oxygen anyway, could be you'd use oxyliqut - carbon soaked in liquid oxygen. See also this previous thread for other hab designs: https://forum.kerbalspaceprogram.com/topic/226413-optimal-size-for-domes-and-other-structures/page/2/

Fram2 launch in 3 hours.

Broadly, I agree that a planetary-scale civilisation needs technology to survive. I'm not sure about the "calculated by Grok" part. The visceral fear of there not being air due to equipment failure feels different to the fear of being stranded in a deserted city without a car, and the grocery stores looted, even though practically, they're the same in terms of danger to yourself. It sounds appealing to live off the land, in our common biosphere, but when was the last time you had nothing but your hands and your clothes? No world-spanning communications device in your pocket, no plastic card that holds all your money, no access to the jank-filled worldbrain that is Wikipedia? I can't remember one, and I'm not sure I could survive without it. One thing that we do need is to have other people with us. The first people to settle Mars or a habitat with the attitude of building a community there will have more success than the ones who are only visiting. Even the mega-rich who, in the past, built elaborate nuclear bunkers, and now are building boltholes, are finding that the real post-apocalypse resilience is in having neighbours that farm and exchange food and knowledge. I also think he's touched on the real issue: space has an image problem. Mars settlement especially has an image problem. How do you make a dry, airless desert feel like a home? How do you domesticate it? You don't dress it up as better than Earth, but you do - you should - provide food, warmth, comfort, health, work and play. Which is a point. How was the American West promoted? What could we learn from its successes and failures?

Helion Energy's fusion reactor is supposed to use the pulses of electromagnetic energy released by expanding fusion plasma to generate electricity directly, but that's not what you're asking. So I'm going to be a terrible swot and ask, "What is usable energy?" This has a scientific term: exergy. To really trim it down, the exergy of an antimatter reactor is low if all you want is to generate power. This doesn't quite matter because the energy release is so great even compared to nuclear fission or fusion, but the form of the energy is difficult to utilise, as the charged particles decay, and the positrons react with the electrons produced, leaving you with nothing but ghostly neutrinos and hard gamma rays. To put it in percentages, of the energy from an initial proton/antiproton annihilation event: 37.77% is expressed in decay of the neutral pions into gamma rays, and this happens almost immediately; 67.33% is left in the energy of the positive and negative charged pions, and if we can't use that, that loses 14.68% just in neutrinos as they decay into charged muons; 52.65% left, which, if left unused, slightly less soon decays into equal amounts of positrons, electrons, and a whopping 31.59% in more neutrinos; 21.06% left, which if we don't separate or harvest the electrons or positrons, annihilates with itself into more gamma rays. And the best use we have so far of using that gamma ray energy... is to let it slam into a block or pool of mass to heat it up so we can utilise the heat, or let it escape into space. Ain't fair, is it? For reaction exhaust, the charged muons are capable of being diverted with a magnetic nozzle to provide thrust, as they're moving at 0.94c, but capturing that charge is... well, I know of no way to accomplish it right now. However... How does one feel about using absurdly powerful lasers to create antimatter out of nothing, then compress it with magnetic fields so you can use an unbelievably powerful gamma ray laser as a rocket sound? Good? https://www.centauri-dreams.org/2016/08/02/the-evolution-of-antimatter-propulsion/

Lots of theoretical work has been done in rocketry in confining unstable, high-energy matter. Whether it be antimatter, metastable helium, metallic hydrogen or single-atom hydrogen, people have seen the performance and wanted it. Fortunately, the creator of the High Frontier boardgame (which you may have heard me go on about in the past) is just this kind of rocket scientist, and included an appendix explaining the technology behind the game's thruster and reactor cards - with citations. Concepts for the design of an antimatter annihilation rocket (D. L. Morgan, British Interplanetary Society, 1982): https://ntrs.nasa.gov/api/citations/19820013176/ This gives a good rundown on what antimatter is, how a reactor utilising it could be made and so on. The important thing is that antimatter is the opposite charge of its matter, so a positron (antimatter electron) has a positive charge, and an antiproton has a negative charge. This means that both can form 'atoms' with its matter counterpart: protonium is a proton electrically-bound to an antiproton, and positronium is a positron bound to an electron. Which brings us to the next design. Positronium can be stored. Not easily, but easier than straight antimatter. tl;dr if pinned with magnetic fields & stretched apart with electric fields, and stored in supercooled quantum dot chips (approximately 10 to the power of 11 Ps atoms may be stored per 1cm x 1cm chip), they have a lifetime of over a year instead of nanoseconds. Further, "the binding energy of this state is quite large, resulting in a ground state that is both stable against direct annihilation and against ionization by low frequency background radiation." Downsides? It's unlikely to have any big annihilation booms, but rather must be laser-excited in a steady stream into an attenuating matrix with hydrogen flowing through it. The stated performance on the "Positronium Bottle Reactor" is 300MW of thermal energy with 2.7 kiloNewtons thrust at 8,000 seconds of delta-V. Propulsion and Power With Positrons (K. Edwards, Air Force Research Laboratory, 2004): https://bravenewclimate.com/files/files/library/meetings/fellows/mar04/edwards_kenneth.pdf Positronium in crossed electric and magnetic fields: the existence of a long-lived ground state (J. Shertzer, J. Ackermann, P. Schmelcher, 1997): https://arxiv.org/abs/physics/9712028

Absolute shame. Let's hope they can try again.

Too much pitch, too much pitch!