18 ms·

Interstellar Flight: Perspectives and Patience

101 points by JPLeRouzic 1y ago

KineticLensman 1y ago
> those of us with an interstellar bent naturally start musing about ‘sundiver’ trajectories, using a solar slingshot to accelerate an outbound spacecraft, perhaps with a propulsive burn at perihelion. . The latter option makes this an ‘Oberth maneuver’ and gives you a maximum outbound kick. You can't do a solar slingshot like you can with (say) Jupiter because the sun is essentially at rest with respect to the rest of the solar system. You could still do an Oberth manoeuvre.
- ta1243 1y ago
  If you unfurl a solar sail after perihelion, presumably you get more energy while nearer the sun, giving more of a "kick", and lower in the gravity well (would oberth still apply for solar sail) Your speed once you get to 1AU would I assume be far higher than if you had simply started at Earth
  - KineticLensman 1y ago
    But getting to the sun in the first place (from Earth) is a massive hassle as you have to lose the Earth's significant orbital speed to 'fall' inward [0]. Perhaps better just to use that fuel to head out. Operating a solar sail really close to the sun would also be challenging because of the massive heat. [0] https://www.nasa.gov/solar-system/its-surprisingly-hard-to-go-to-the-sun/ https://www.nasa.gov/solar-system/its-surprisingly-hard-to-g...
- JumpCrisscross 1y ago
  > the sun is essentially at rest with respect to the rest of the solar system But not with respect to other star systems.
  - KineticLensman 1y ago
    If you start in our solar system this doesn't help. You could do a gravity assist from a planet to help with an interstellar trip (like the Voyagers) but not a gravity assist from the sun, starting from one of 'our' planets.
    - JumpCrisscross 1y ago
      > could do a gravity assist from a planet to help with an interstellar trip (like the Voyagers) but not a gravity assist from the sun, starting from one of 'our' planets Of course you can. Galileo, Cassini-Huygens and Giotto are Earth-launched spacecraft that used Earth for a gravity assist. If you need to accelerate with reference to the galaxy, you can use the Sun’s motion through it to slingshot.
      - sfink 1y ago
        Earth isn't going in a straight line. If it were, it would be useless as a gravity assist.
      - _moof 1y ago
        No, you can't. Gravity assists require the assisting body (Jupiter) to be moving, relative to the body that needs the assist (Voyager), in the direction the assisted body wants to go. They have an unfortunate name because it's not just the assisting body's gravity that provides the assist. It's the combination of gravity and velocity. As Voyager nears Jupiter, Jupiter's gravity grabs it. Then, Jupiter's velocity relative to Voyager drags Voyager - that is, transfers energy to it. Without that relative motion, all Voyager's gravity does is add energy on the way in and then remove exactly the same energy on the way out.
agentultra 1y ago
Won't dreams stay dreams? There's literally nothing there, why go all that way? The distances are so incredibly vast. It seems like we ought to be content with staying put.
- cryptoz 1y ago
  All life on Earth is going die. Humanity has never been content with staying put, why would we start now? And what do you mean "literally nothing there"? The universe has a loooooot of stuff in it.
  - bregma 1y ago
    > The universe has a loooooot of stuff in it. In fact, technically, there's nothing here. It's all out there.
    - jvm___ 1y ago
      The Sun: 99.86% of the solar system's total mass. Jupiter: ~0.095% of the total mass, and ~71% of the non-solar mass. Saturn: ~0.03% of the total mass, and ~19% of the non-solar mass. Uranus and Neptune: Contribute a small percentage to the remaining non-solar mass. All other objects: (inner planets, dwarf planets, moons, asteroids, comets, etc.) account for less than 0.002% of the solar system's total mass. Your brain mass is about 3 disposable water bottles in weight and we can debate what parts of that are thinking and actually "you". You are insignificant on the scale of the solar system let alone the universe.
      - pcrh 1y ago
        >Tragula's wife used to complain to him about the utterly inordinate amount of time he spent staring out into space, or mulling over the mechanics of safety pins, or doing spectrographic analyses of pieces of fairy cake. She would often tell her husband to have some sense of proportion, sometimes as often as thirty-eight times in one day. In response to her pleas for him to find some perspective, he built the Total Perspective Vortex. >Into one end he plugged the whole of reality as extrapolated from a piece of fairy cake, and into the other end he plugged his wife: so that when he turned it on she would see in one instant the whole infinity of creation and herself in relation to it. To Trin Tragula’s horror, the shock completely annihilated her brain... ~Douglas Adams, The Restaurant at the End of the Universe
os2warpman 1y ago
>To get around thousand-year generation ships, we are examining some beamed energy solutions that could drive a small sail to Proxima in 20 years. The odds of a spacecraft hitting a single particle of dust while in space are 100%. A spacecraft hitting a single particle of dust at 0.2c will impart tens of millions of joules into the body of the spacecraft, the equivalent of getting hit with hundreds of pulses from the most powerful laser ever created by humanity-- simultaneously. Or concentrating several kilogram's worth of TNT into the size of a particle of dust and detonating it.
- archermarks 1y ago
  Only true if the dust grain is stopped by the craft. For a thin lightsail the grain will probably pass right through without depositing much energy
  - dylan604 1y ago
    So it passes through the sail and then hits the spacecraft attached to the sail. Now what? kaboom? small holes in the hull would not be good for the occupants.
    - rbanffy 1y ago
      The sail is much, much larger than the craft. The odds of that happening are tiny. In any case, we should launch more than one.
      - dylan604 1y ago
        more than one basket for those eggs will be important.
    - pfdietz 1y ago
      When it passes through the sail, enough energy is deposited in the grain to explode it, so if there's sufficient distance to the hull the vapor deposits sufficiently low energy/area to be tolerable. https://en.wikipedia.org/wiki/Whipple_shield https://en.wikipedia.org/wiki/Whipple_shield
WalterBright 1y ago
The only way I can see hope for spreading terrestrial life through the galaxy is to send tiny spacecraft. The spacecraft can survey what it finds and send the information back to earth. Earth can send back instructions to the nanobots on the spacecraft to build what is necessary from local materials, and then build life to inhabit it.
krunck 1y ago
The comment by Benjamin Stockton on the article page is spot-on: >I just wonder if humanity’s adventurous nature is leading us away from a proper focus on the sustainability of our civilization, our specie, and our fragile planetary environment? But we still need spaceflight at least for planetary defense against asteroids, mining asteroids(so we don't have to mine Earth), etc.
- sorcerer-mar 1y ago
  What resources are on asteroids that justify the energy expenditure to get from space and back? Can't be many of them...
  - kibwen 1y ago
    The most compelling economic reason to pursue the technology of asteroid mining (at least as far as Earth's gravity well is concerned) is not to ever actually launch any serious asteroid mining operations, but rather to fool those who own gold into believing that you have the capability to devalue gold at your whim, and thereby accept a small ransom to not go asteroid mining.
    - dash2 1y ago
      Wouldn’t work because of the collective action problem among gold owners!
      - vkou 1y ago
        And because someone shorting gold would have a financial incentive to do it himself.
  - JumpCrisscross 1y ago
    > What resources are on asteroids that justify the energy expenditure to get from space and back? With chemical rockets, not much. With "a propellant-less propulsion propulsion system such as solar sails or electric sails," bringing water (propellant) to low-earth orbit starts making sense [1], as does mining platinum, but only if "the quantity of platinum from space would substitute an equal quantity of terrestrial platinum," i.e. moving heavy industry off the Earth's surface [1]. Given asteroid-mining profitability is dominated by "the throughput rate, which depends on the mining process," it's possibly to see a path to certain rare-earth minerals becoming profitable to mine in space if environmental controls on Earth are tightened while constant-thrust propulsion technologies advance. [1] https://arxiv.org/pdf/1810.03836 https://arxiv.org/pdf/1810.03836
econ 1y ago
You first have to build the perpetual motion engine and the reactionless drive. Current thinking is quite hostile to doing the work. You might not be able to build the things you think you can. You certainly won't build the things you think you can't.
- vjvjvjvjghv 1y ago
  I am not aware of any approaches that even remotely could deliver a perpetual motion engine or a reactionless drive. You need something to start from but there is nothing in sight.
  - econ 1y ago
    https://youtube.com/@madsciencelptech?si=3XO72NQMpecoUwOR https://youtube.com/@madsciencelptech?si=3XO72NQMpecoUwOR
  - econ 1y ago
    We have lots of things that didn't seem possible. The first barrier isn't finding the previous art. You are not even supposed to talk about it. How strange was nuclear before innital discovery? I'm not aware of [other] approaches that will allow us to travel to the stars.
d_silin 1y ago
Developing propulsion technology to reach 0.1c velocity will move the needle on interstellar propulsion from impossible to just barely feasible. Although that is at least 100-200 years away, we can absolutely start expanding into our Solar System, starting with nearby bodies, like Moon and Mars.
- JumpCrisscross 1y ago
  > Developing propulsion technology to reach 0.1c velocity will move the needle on interstellar propulsion from impossible to just barely feasible More than barely. "A 40-year one-way interstellar flyby mission to the nearest stars will require a relativistic spacecraft speed in excess of 6000 AU/yr (i.e., > 0.1c)" [1]. That means, practically speaking, nuclear-fusion, antimatter-annihilation and directed-energy propulsion. All of which are TRL ≤ 2. My bet would be on fusion propulsion. It's inherently easier than fusion power since you don't need to bother converting the energy to electricity. That said, solar sails [2] and directed-energy anti-drone weapons [3] are seeing quiet progress. [1] https://ntrs.nasa.gov/api/citations/20200000759/downloads/20200000759.pdf https://ntrs.nasa.gov/api/citations/20200000759/downloads/20... [2] https://www.nasa.gov/mission/acs3/ https://www.nasa.gov/mission/acs3/ [3] https://en.wikipedia.org/wiki/Silent_Hunter_(laser_weapon) https://en.wikipedia.org/wiki/Silent_Hunter_(laser_weapon)
  - carpdiem 1y ago
    1 AU is about 8.3 light minutes. So 6k AU is about 50k light minutes. with ~525k minutes in a year, that means that 6k AU/yr is almost exactly 0.1c.
    - JumpCrisscross 1y ago
      > that means that 6k AU/yr is almost exactly 0.1c Nobody debates this. The point is that 0.1c propulsion is not necessarily 100+ years away. And its 40-year transit time is not "barely feasible," it's comparable to present deep-space mission timelines [1]. [1] https://science.nasa.gov/mission/voyager/ https://science.nasa.gov/mission/voyager/
- 1y ago
jmyeet 1y ago
So this is another reason why I see Dyson Swarms as being the inevitable evolution of human civilization. Let me explain why. First, to clarify, a Dyson Swarm is a cloud of orbitals around a star to use most or all of its energy via solar collectors. This was originally called a Dyson Sphere but was renamed because of confusion: people thought a Dyson Swarm was a rigid shell. It never was. Anyway, the classic orbital is an O'Neil Cylinder, which would be 3-4 miles in diameter and 10-20 miles long. You spin it to get earthlike gravity. With this diameter the rotation isn't likely disconcerting and the centrifugal forces aren't so large as to tear it apart. This kind of structure could be built with a material no stronger than stainless steel and using solar panels for power. It's relatively low tech. There aren't any exotic physics or exotic static states of matter required. It's basically an engineering problem and can be built incrementally. Why do I mention this? Because fo rthe distances involved, an interstellar starshhip is basically just an O'Neil Cylinder. You need to support people for centuries. Such a cylinder could get 10s of thousands of people, possibly 100k+ to another system in relative comfort. So how do you get to another star? The tyranny of the rocket equation means any form of propulsion where you need to carry to propellant just won't work with the possible exception of nuclear fusion. But what if you didn't have to carry propellant at all? To accelerate or decelerate. That makes it way easier. But how would yo udo that? Easy, at least in theory: solar sails. The solar wind carries pretty significant momentum. A sufficiently large solar sail (and it would have to be large for such a ship) would absolutely be capable of accelerating a ship to at least 0.01c. And you can decelerate with the same solar sail. You can do even better by collecting energy from the Sun and concentrating it on the sails, which is yet another reason to build a Dyson Swarm. The energy budget to travel to even our closest star is so vast that we would need to do things like collect most of the Sun's output energy. I personally don't believe FTL is possible. Time dilation only really kicks in meaningfully at >0.99c and I just don't think that's parctical and, if it were, the energy required is even more vast. In fact, at 0.99c you would suffer drag from the interstellar medium (gas and dust).. So any intersteallar ship is going to be a generation ship, a habitat.
- tenthirtyam 1y ago
  Like "Rendezvous with Rama" by Arthur C Clarke: A mysterious cylindrical spaceship arrives at planet Earth from outer space.
GMoromisato 1y ago
I worked this table out with ChatGPT (with all the caveats that implies): https://gridwhale.com/program.hexm?id=GCJ5TL7Z&file=GCJ5TL7Z_051053055KJJXUDK055X055YX052UWAH.dat#Page1 https://gridwhale.com/program.hexm?id=GCJ5TL7Z&file=GCJ5TL7Z... Basically, nothing short of antimatter rockets will get you a self-contained interstellar ship. Ion propulsion, even with nuclear reactors, can't get you enough speed. Fission-fragment reactors can get you up to 1% lightspeed, but that's still 400 years to Alpha Centauri--I'm not sure I would trust a generation ship to last that long. Advanced fusion might cut that down to 100 years. Antimatter can reach 20% lightspeed, which means 20 years to Alpha Centauri. ChatGPT kept asking to design a laser sail (external power source) to avoid the tyranny of the rocket equation, but I just don't think that can scale to crewed travel.
- rozal 1y ago
  [dead]
- imoreno 1y ago
  If we assume 100 colonists on the ship, with 10 tons of mass per person, accelerating to 0.2c over 2 ly and then back down, the energy required is quite substantial. Multiple centuries of the total output of the whole planet.
imoreno 1y ago
With Alpha Centauri being only 4 light years away, interstellar travel seems almost feasible. But then you consider all the inconvenient details, and realize such a journey would have to take hundreds, maybe thousands or even more years on top of some incredible advances in rocket tech. If you go to something like Trappist (40 ly) at 0.01c (very optimistic), it's not just that everyone you know will be dead when you arrive. Your entire nation will have disappeared to the sands of time. The landfall announcement you send back will be incomprehensible because of language shifts, and you won't live to see the reply. Meanwhile, such a trip would be an enormous investment, requiring multiple nations to bankrupt themselves, with no hope of even surviving to see the outcome. With that, it's very hard to imagine interstellar travel being feasible with our current understanding. There would have to be something like FTL travel or wormhole. The only "realistic" development, (much) better engines that can do 0.1c, would not actually change much.
- db48x 1y ago
  Yes, we have a long ways to go before we can be considered a starfaring species, one that can make and keep long–term agreements when they involve round–trip times in the tens of thousands of years. Still, it can be useful to altruistically start colonies before then. There’s a book called Count to a Trillion which explores these ideas, and others. At the end of it the main character’s wife sets out on a mission to M33 and isn’t expected to return for at least 70,000 years. He gets stuck on Earth, unable to catch up with her, and promises to be here when she returns. The sequel is all about what he has to go through to keep Earth a going concern while she’s away.
  - saulpw 1y ago
    Also the Queen song "'39", written by Brian May (who resumed and completed his Ph.D. in Astrophysics decades after his time with Queen).
- jillesvangurp 1y ago
  Worse, you have no idea what you will find on the other side and weather that includes somewhere that doesn't make the arctic poles on earth look like paradise. And you'll be traveling in a small confined space. For ages. The good news is, you'll probably be unconscious for the journey. The bad news is that a lot can happen in decades/centuries/milennia and there's no guarantee you'll actually wake up. And everything else you said. That raises the question who would want to travel and why. And what's wrong with them. Because the profile for people that want this would be hard to distinguish from somebody that is depressed and suicidal.
xpuente 1y ago
It won’t be us. It will be our descendants — the machines.
- adrian_b 1y ago
  Any autonomous machines in a distant enough future will look neither as the present humans or animals nor like the present robots, because they will have to use a mixture of the technologies developed by living beings and by humans. Humans have developed various things that are better for certain purposes than anything used by a living being, e.g. metals and semiconductor devices (most of the human-only technologies are a consequence of the control of fire, i.e. of the ability to perform manufacturing processes at high temperatures, unlike the living beings, which are limited to temperatures close to that of the ambient). On the other hand, for other purposes the use of organic substances and of the methods of chemical synthesis used by living beings are unbeatable. So any future descendants will have to use hybrid technologies, like the "cyborgs" of many SF novels/movies, except that I have never seen any SF "cyborg" that combined the right parts from "machines" and from living organisms. As an example, for the problem of energy storage for powering a machine, for providing short-time high power bursts capacitors and batteries are better than the chemical reactions used by living beings, e.g. ATP & phospho-creatine hydrolysis and anaerobic glycolysis. On the other hand for storing high-amounts of energy for long-time autonomy at a moderate power level, none of the fuel cell or battery technologies that have ever been attempted appears to have the potential to ever match the performances of the enzymatic oxidation of hydrocarbons that converts their chemical energy into ionic gradients in living beings, e.g. in our mitochondria. So an ideal autonomous machine would combine high-power capacitors/batteries with high-energy biologically-derived fuel cells.
  - xpuente 1y ago
    Consciousness, once engineered, will make any biology redundant.
- thrance 1y ago
  Yes, 100%. That's the blind spot to all these sci-fi speculations. Hauling cities between stars along with the environment needed to sustain them might very well be impossible. But who needs that when you can send a tiny chip with simulated human (or post-human) personalities on it? Mandatory advertising for Greg Egan: read his novel, Diaspora. Truly mind-expanding on the subject.
kfuse 1y ago
Why is everyone so fixed on interstellar travel? What if the galaxy is chock full of rogue planets? There may be hundreds if not thousands of worlds between us and the surrounding stars. Hopefully, Roman Telescope set to launch in 2027 is going to find lots of them.
- baxtr 1y ago
  Because we’re a species of explorers. At least some of us are.
- verzali 1y ago
  Those rogue worlds are frozen though, the only source they have is from radioactive decay in their cores. And eternally dark, since they have no Sun to light them. It would make more sense to use fusion reactors to power colonies in the outer reaches of the solar system than to go to a rogue planet.
  - kfuse 1y ago
    Jupiter is 5 times farther from the Sun than us, there is basically no lighting and heat from the Sun there. I think for a civilization capable of sending reasonable amount of people people at reasonable speeds to colonize such planets, creating suitable atmosphere, lighting and heating is very much possible. Gravity is the only hard requirement.
southernplaces7 1y ago
I love to dream of interstellar space travel, but it's only a fun dream, with no practical road to it outside the fantasy landscape of essentially magical technology. That doesn't have to stop us from much more practical and realistic striving though. We have an entire universe in mini right here around us in the form of our own solar system, filled with so many resources that we probably couldn't over-consume them in millennia, and possible extra-planetary homes for billions of us using technologies that are just this side of realistic. We're still talking about at least decades of fantastically costly investment, but at least it would begin as investment for a shining future within a human lifetime. Colonizing the solar system doesn't sound as impressive on text as stories of strange and wonderful alien landscapes in distant star systems, but I don't think anyone being able to gaze with their own eyes from the peaks of Verona Rupes 90 years from now would care.
Oleksa_dr 1y ago
Even if we get there, will there be any benefit to civilization, maybe there are no habitable worlds there and it is not possible to profitably extract valuable resources for future travel. In my opinion, the most realistic thing is to come to an understanding of how our body/brain works. Then learn how to transfer consciousness from a living shell to a machine (with an emulsified environment for nerve endings, and so on). To learn how to print bodies, even if it takes as many years as it takes to grow in natural conditions. Between solar systems or even galaxies, our digital consciousnesses will travel, maybe even copies and once in n years, synchronized in some exact or not. That is, to achieve immortality in a “digital” way, then time will not play a role. Another problem is spacecraft, so that they can travel with sufficient autonomy for hundreds of thousands or even millions of years (this is probably the main problem).
lofaszvanitt 1y ago
Everyone suffers from the sci-fi delusion. We can't solve the problem of large-scale wildfires (sending helicopters and planes to drop water on forest fires is not a viable solution) and we can't even do large-scale terraforming on our own Earth. We have to use containers to transport liquids and solids from one place to another. We cannot control the weather, yet people fantasize about travelling into space. It's delusional, isn't it? It's borderline ridiculous. And we have these human-centric systems that are unusable and inefficient, not to mention a terrible economic system that rewards the virus-like entities in society. We aren't going anywhere.
- silverquiet 1y ago
  I would say worse than that, we are doing the opposite of large-scale terraforming to create a planet that will be rather inhospitable towards the end of this century and even less so in the centuries that follow. I think the sci-fi delusion is a hold over from a better time; the heyday was probably the 50's-60's when scientific progress seems like it was much greater and was actually able to translate into benefits for people that were noticeable.
  - lofaszvanitt 1y ago
    Yeah, and nobody cares, nobody seems to notice, seemingly people who have the power to steer things the right way are totally lobotomized. It's just like in Cyberpunk, where the power couple's brain is getting rewired by "entities", because they go against the flow.

101 points by JPLeRouzic 1y ago

> those of us with an interstellar bent naturally start musing about ‘sundiver’ trajectories, using a solar slingshot to accelerate an outbound spacecraft, perhaps with a propulsive burn at perihelion. . The latter option makes this an ‘Oberth maneuver’ and gives you a maximum outbound kick. You can't do a solar slingshot like you can with (say) Jupiter because the sun is essentially at rest with respect to the rest of the solar system. You could still do an Oberth manoeuvre.

ta1243 1y ago
If you unfurl a solar sail after perihelion, presumably you get more energy while nearer the sun, giving more of a "kick", and lower in the gravity well (would oberth still apply for solar sail) Your speed once you get to 1AU would I assume be far higher than if you had simply started at Earth
- KineticLensman 1y ago
  But getting to the sun in the first place (from Earth) is a massive hassle as you have to lose the Earth's significant orbital speed to 'fall' inward [0]. Perhaps better just to use that fuel to head out. Operating a solar sail really close to the sun would also be challenging because of the massive heat. [0] https://www.nasa.gov/solar-system/its-surprisingly-hard-to-go-to-the-sun/ https://www.nasa.gov/solar-system/its-surprisingly-hard-to-g...
JumpCrisscross 1y ago
> the sun is essentially at rest with respect to the rest of the solar system But not with respect to other star systems.
- KineticLensman 1y ago
  If you start in our solar system this doesn't help. You could do a gravity assist from a planet to help with an interstellar trip (like the Voyagers) but not a gravity assist from the sun, starting from one of 'our' planets.
  - JumpCrisscross 1y ago
    > could do a gravity assist from a planet to help with an interstellar trip (like the Voyagers) but not a gravity assist from the sun, starting from one of 'our' planets Of course you can. Galileo, Cassini-Huygens and Giotto are Earth-launched spacecraft that used Earth for a gravity assist. If you need to accelerate with reference to the galaxy, you can use the Sun’s motion through it to slingshot.
    - sfink 1y ago
      Earth isn't going in a straight line. If it were, it would be useless as a gravity assist.
    - _moof 1y ago
      No, you can't. Gravity assists require the assisting body (Jupiter) to be moving, relative to the body that needs the assist (Voyager), in the direction the assisted body wants to go. They have an unfortunate name because it's not just the assisting body's gravity that provides the assist. It's the combination of gravity and velocity. As Voyager nears Jupiter, Jupiter's gravity grabs it. Then, Jupiter's velocity relative to Voyager drags Voyager - that is, transfers energy to it. Without that relative motion, all Voyager's gravity does is add energy on the way in and then remove exactly the same energy on the way out.

agentultra 1y ago

Won't dreams stay dreams? There's literally nothing there, why go all that way? The distances are so incredibly vast. It seems like we ought to be content with staying put.

cryptoz 1y ago
All life on Earth is going die. Humanity has never been content with staying put, why would we start now? And what do you mean "literally nothing there"? The universe has a loooooot of stuff in it.
- bregma 1y ago
  > The universe has a loooooot of stuff in it. In fact, technically, there's nothing here. It's all out there.
  - jvm___ 1y ago
    The Sun: 99.86% of the solar system's total mass. Jupiter: ~0.095% of the total mass, and ~71% of the non-solar mass. Saturn: ~0.03% of the total mass, and ~19% of the non-solar mass. Uranus and Neptune: Contribute a small percentage to the remaining non-solar mass. All other objects: (inner planets, dwarf planets, moons, asteroids, comets, etc.) account for less than 0.002% of the solar system's total mass. Your brain mass is about 3 disposable water bottles in weight and we can debate what parts of that are thinking and actually "you". You are insignificant on the scale of the solar system let alone the universe.
    - pcrh 1y ago
      >Tragula's wife used to complain to him about the utterly inordinate amount of time he spent staring out into space, or mulling over the mechanics of safety pins, or doing spectrographic analyses of pieces of fairy cake. She would often tell her husband to have some sense of proportion, sometimes as often as thirty-eight times in one day. In response to her pleas for him to find some perspective, he built the Total Perspective Vortex. >Into one end he plugged the whole of reality as extrapolated from a piece of fairy cake, and into the other end he plugged his wife: so that when he turned it on she would see in one instant the whole infinity of creation and herself in relation to it. To Trin Tragula’s horror, the shock completely annihilated her brain... ~Douglas Adams, The Restaurant at the End of the Universe

os2warpman 1y ago

>To get around thousand-year generation ships, we are examining some beamed energy solutions that could drive a small sail to Proxima in 20 years. The odds of a spacecraft hitting a single particle of dust while in space are 100%. A spacecraft hitting a single particle of dust at 0.2c will impart tens of millions of joules into the body of the spacecraft, the equivalent of getting hit with hundreds of pulses from the most powerful laser ever created by humanity-- simultaneously. Or concentrating several kilogram's worth of TNT into the size of a particle of dust and detonating it.

archermarks 1y ago
Only true if the dust grain is stopped by the craft. For a thin lightsail the grain will probably pass right through without depositing much energy
- dylan604 1y ago
  So it passes through the sail and then hits the spacecraft attached to the sail. Now what? kaboom? small holes in the hull would not be good for the occupants.
  - rbanffy 1y ago
    The sail is much, much larger than the craft. The odds of that happening are tiny. In any case, we should launch more than one.
    - dylan604 1y ago
      more than one basket for those eggs will be important.
  - pfdietz 1y ago
    When it passes through the sail, enough energy is deposited in the grain to explode it, so if there's sufficient distance to the hull the vapor deposits sufficiently low energy/area to be tolerable. https://en.wikipedia.org/wiki/Whipple_shield https://en.wikipedia.org/wiki/Whipple_shield

WalterBright 1y ago

The only way I can see hope for spreading terrestrial life through the galaxy is to send tiny spacecraft. The spacecraft can survey what it finds and send the information back to earth. Earth can send back instructions to the nanobots on the spacecraft to build what is necessary from local materials, and then build life to inhabit it.

krunck 1y ago

The comment by Benjamin Stockton on the article page is spot-on: >I just wonder if humanity’s adventurous nature is leading us away from a proper focus on the sustainability of our civilization, our specie, and our fragile planetary environment? But we still need spaceflight at least for planetary defense against asteroids, mining asteroids(so we don't have to mine Earth), etc.

sorcerer-mar 1y ago
What resources are on asteroids that justify the energy expenditure to get from space and back? Can't be many of them...
- kibwen 1y ago
  The most compelling economic reason to pursue the technology of asteroid mining (at least as far as Earth's gravity well is concerned) is not to ever actually launch any serious asteroid mining operations, but rather to fool those who own gold into believing that you have the capability to devalue gold at your whim, and thereby accept a small ransom to not go asteroid mining.
  - dash2 1y ago
    Wouldn’t work because of the collective action problem among gold owners!
    - vkou 1y ago
      And because someone shorting gold would have a financial incentive to do it himself.
- JumpCrisscross 1y ago
  > What resources are on asteroids that justify the energy expenditure to get from space and back? With chemical rockets, not much. With "a propellant-less propulsion propulsion system such as solar sails or electric sails," bringing water (propellant) to low-earth orbit starts making sense [1], as does mining platinum, but only if "the quantity of platinum from space would substitute an equal quantity of terrestrial platinum," i.e. moving heavy industry off the Earth's surface [1]. Given asteroid-mining profitability is dominated by "the throughput rate, which depends on the mining process," it's possibly to see a path to certain rare-earth minerals becoming profitable to mine in space if environmental controls on Earth are tightened while constant-thrust propulsion technologies advance. [1] https://arxiv.org/pdf/1810.03836 https://arxiv.org/pdf/1810.03836

econ 1y ago

You first have to build the perpetual motion engine and the reactionless drive. Current thinking is quite hostile to doing the work. You might not be able to build the things you think you can. You certainly won't build the things you think you can't.

vjvjvjvjghv 1y ago
I am not aware of any approaches that even remotely could deliver a perpetual motion engine or a reactionless drive. You need something to start from but there is nothing in sight.
- econ 1y ago
  https://youtube.com/@madsciencelptech?si=3XO72NQMpecoUwOR https://youtube.com/@madsciencelptech?si=3XO72NQMpecoUwOR
- econ 1y ago
  We have lots of things that didn't seem possible. The first barrier isn't finding the previous art. You are not even supposed to talk about it. How strange was nuclear before innital discovery? I'm not aware of [other] approaches that will allow us to travel to the stars.

d_silin 1y ago

Developing propulsion technology to reach 0.1c velocity will move the needle on interstellar propulsion from impossible to just barely feasible. Although that is at least 100-200 years away, we can absolutely start expanding into our Solar System, starting with nearby bodies, like Moon and Mars.

JumpCrisscross 1y ago
> Developing propulsion technology to reach 0.1c velocity will move the needle on interstellar propulsion from impossible to just barely feasible More than barely. "A 40-year one-way interstellar flyby mission to the nearest stars will require a relativistic spacecraft speed in excess of 6000 AU/yr (i.e., > 0.1c)" [1]. That means, practically speaking, nuclear-fusion, antimatter-annihilation and directed-energy propulsion. All of which are TRL ≤ 2. My bet would be on fusion propulsion. It's inherently easier than fusion power since you don't need to bother converting the energy to electricity. That said, solar sails [2] and directed-energy anti-drone weapons [3] are seeing quiet progress. [1] https://ntrs.nasa.gov/api/citations/20200000759/downloads/20200000759.pdf https://ntrs.nasa.gov/api/citations/20200000759/downloads/20... [2] https://www.nasa.gov/mission/acs3/ https://www.nasa.gov/mission/acs3/ [3] https://en.wikipedia.org/wiki/Silent_Hunter_(laser_weapon) https://en.wikipedia.org/wiki/Silent_Hunter_(laser_weapon)
- carpdiem 1y ago
  1 AU is about 8.3 light minutes. So 6k AU is about 50k light minutes. with ~525k minutes in a year, that means that 6k AU/yr is almost exactly 0.1c.
  - JumpCrisscross 1y ago
    > that means that 6k AU/yr is almost exactly 0.1c Nobody debates this. The point is that 0.1c propulsion is not necessarily 100+ years away. And its 40-year transit time is not "barely feasible," it's comparable to present deep-space mission timelines [1]. [1] https://science.nasa.gov/mission/voyager/ https://science.nasa.gov/mission/voyager/
1y ago

jmyeet 1y ago

So this is another reason why I see Dyson Swarms as being the inevitable evolution of human civilization. Let me explain why. First, to clarify, a Dyson Swarm is a cloud of orbitals around a star to use most or all of its energy via solar collectors. This was originally called a Dyson Sphere but was renamed because of confusion: people thought a Dyson Swarm was a rigid shell. It never was. Anyway, the classic orbital is an O'Neil Cylinder, which would be 3-4 miles in diameter and 10-20 miles long. You spin it to get earthlike gravity. With this diameter the rotation isn't likely disconcerting and the centrifugal forces aren't so large as to tear it apart. This kind of structure could be built with a material no stronger than stainless steel and using solar panels for power. It's relatively low tech. There aren't any exotic physics or exotic static states of matter required. It's basically an engineering problem and can be built incrementally. Why do I mention this? Because fo rthe distances involved, an interstellar starshhip is basically just an O'Neil Cylinder. You need to support people for centuries. Such a cylinder could get 10s of thousands of people, possibly 100k+ to another system in relative comfort. So how do you get to another star? The tyranny of the rocket equation means any form of propulsion where you need to carry to propellant just won't work with the possible exception of nuclear fusion. But what if you didn't have to carry propellant at all? To accelerate or decelerate. That makes it way easier. But how would yo udo that? Easy, at least in theory: solar sails. The solar wind carries pretty significant momentum. A sufficiently large solar sail (and it would have to be large for such a ship) would absolutely be capable of accelerating a ship to at least 0.01c. And you can decelerate with the same solar sail. You can do even better by collecting energy from the Sun and concentrating it on the sails, which is yet another reason to build a Dyson Swarm. The energy budget to travel to even our closest star is so vast that we would need to do things like collect most of the Sun's output energy. I personally don't believe FTL is possible. Time dilation only really kicks in meaningfully at >0.99c and I just don't think that's parctical and, if it were, the energy required is even more vast. In fact, at 0.99c you would suffer drag from the interstellar medium (gas and dust).. So any intersteallar ship is going to be a generation ship, a habitat.

tenthirtyam 1y ago
Like "Rendezvous with Rama" by Arthur C Clarke: A mysterious cylindrical spaceship arrives at planet Earth from outer space.

GMoromisato 1y ago

I worked this table out with ChatGPT (with all the caveats that implies): https://gridwhale.com/program.hexm?id=GCJ5TL7Z&file=GCJ5TL7Z_051053055KJJXUDK055X055YX052UWAH.dat#Page1 https://gridwhale.com/program.hexm?id=GCJ5TL7Z&file=GCJ5TL7Z... Basically, nothing short of antimatter rockets will get you a self-contained interstellar ship. Ion propulsion, even with nuclear reactors, can't get you enough speed. Fission-fragment reactors can get you up to 1% lightspeed, but that's still 400 years to Alpha Centauri--I'm not sure I would trust a generation ship to last that long. Advanced fusion might cut that down to 100 years. Antimatter can reach 20% lightspeed, which means 20 years to Alpha Centauri. ChatGPT kept asking to design a laser sail (external power source) to avoid the tyranny of the rocket equation, but I just don't think that can scale to crewed travel.

rozal 1y ago
[dead]
imoreno 1y ago
If we assume 100 colonists on the ship, with 10 tons of mass per person, accelerating to 0.2c over 2 ly and then back down, the energy required is quite substantial. Multiple centuries of the total output of the whole planet.

imoreno 1y ago

With Alpha Centauri being only 4 light years away, interstellar travel seems almost feasible. But then you consider all the inconvenient details, and realize such a journey would have to take hundreds, maybe thousands or even more years on top of some incredible advances in rocket tech. If you go to something like Trappist (40 ly) at 0.01c (very optimistic), it's not just that everyone you know will be dead when you arrive. Your entire nation will have disappeared to the sands of time. The landfall announcement you send back will be incomprehensible because of language shifts, and you won't live to see the reply. Meanwhile, such a trip would be an enormous investment, requiring multiple nations to bankrupt themselves, with no hope of even surviving to see the outcome. With that, it's very hard to imagine interstellar travel being feasible with our current understanding. There would have to be something like FTL travel or wormhole. The only "realistic" development, (much) better engines that can do 0.1c, would not actually change much.

db48x 1y ago
Yes, we have a long ways to go before we can be considered a starfaring species, one that can make and keep long–term agreements when they involve round–trip times in the tens of thousands of years. Still, it can be useful to altruistically start colonies before then. There’s a book called Count to a Trillion which explores these ideas, and others. At the end of it the main character’s wife sets out on a mission to M33 and isn’t expected to return for at least 70,000 years. He gets stuck on Earth, unable to catch up with her, and promises to be here when she returns. The sequel is all about what he has to go through to keep Earth a going concern while she’s away.
- saulpw 1y ago
  Also the Queen song "'39", written by Brian May (who resumed and completed his Ph.D. in Astrophysics decades after his time with Queen).
jillesvangurp 1y ago
Worse, you have no idea what you will find on the other side and weather that includes somewhere that doesn't make the arctic poles on earth look like paradise. And you'll be traveling in a small confined space. For ages. The good news is, you'll probably be unconscious for the journey. The bad news is that a lot can happen in decades/centuries/milennia and there's no guarantee you'll actually wake up. And everything else you said. That raises the question who would want to travel and why. And what's wrong with them. Because the profile for people that want this would be hard to distinguish from somebody that is depressed and suicidal.

xpuente 1y ago

It won’t be us. It will be our descendants — the machines.

adrian_b 1y ago
Any autonomous machines in a distant enough future will look neither as the present humans or animals nor like the present robots, because they will have to use a mixture of the technologies developed by living beings and by humans. Humans have developed various things that are better for certain purposes than anything used by a living being, e.g. metals and semiconductor devices (most of the human-only technologies are a consequence of the control of fire, i.e. of the ability to perform manufacturing processes at high temperatures, unlike the living beings, which are limited to temperatures close to that of the ambient). On the other hand, for other purposes the use of organic substances and of the methods of chemical synthesis used by living beings are unbeatable. So any future descendants will have to use hybrid technologies, like the "cyborgs" of many SF novels/movies, except that I have never seen any SF "cyborg" that combined the right parts from "machines" and from living organisms. As an example, for the problem of energy storage for powering a machine, for providing short-time high power bursts capacitors and batteries are better than the chemical reactions used by living beings, e.g. ATP & phospho-creatine hydrolysis and anaerobic glycolysis. On the other hand for storing high-amounts of energy for long-time autonomy at a moderate power level, none of the fuel cell or battery technologies that have ever been attempted appears to have the potential to ever match the performances of the enzymatic oxidation of hydrocarbons that converts their chemical energy into ionic gradients in living beings, e.g. in our mitochondria. So an ideal autonomous machine would combine high-power capacitors/batteries with high-energy biologically-derived fuel cells.
- xpuente 1y ago
  Consciousness, once engineered, will make any biology redundant.
thrance 1y ago
Yes, 100%. That's the blind spot to all these sci-fi speculations. Hauling cities between stars along with the environment needed to sustain them might very well be impossible. But who needs that when you can send a tiny chip with simulated human (or post-human) personalities on it? Mandatory advertising for Greg Egan: read his novel, Diaspora. Truly mind-expanding on the subject.

kfuse 1y ago

Why is everyone so fixed on interstellar travel? What if the galaxy is chock full of rogue planets? There may be hundreds if not thousands of worlds between us and the surrounding stars. Hopefully, Roman Telescope set to launch in 2027 is going to find lots of them.

baxtr 1y ago
Because we’re a species of explorers. At least some of us are.
verzali 1y ago
Those rogue worlds are frozen though, the only source they have is from radioactive decay in their cores. And eternally dark, since they have no Sun to light them. It would make more sense to use fusion reactors to power colonies in the outer reaches of the solar system than to go to a rogue planet.
- kfuse 1y ago
  Jupiter is 5 times farther from the Sun than us, there is basically no lighting and heat from the Sun there. I think for a civilization capable of sending reasonable amount of people people at reasonable speeds to colonize such planets, creating suitable atmosphere, lighting and heating is very much possible. Gravity is the only hard requirement.

southernplaces7 1y ago

I love to dream of interstellar space travel, but it's only a fun dream, with no practical road to it outside the fantasy landscape of essentially magical technology. That doesn't have to stop us from much more practical and realistic striving though. We have an entire universe in mini right here around us in the form of our own solar system, filled with so many resources that we probably couldn't over-consume them in millennia, and possible extra-planetary homes for billions of us using technologies that are just this side of realistic. We're still talking about at least decades of fantastically costly investment, but at least it would begin as investment for a shining future within a human lifetime. Colonizing the solar system doesn't sound as impressive on text as stories of strange and wonderful alien landscapes in distant star systems, but I don't think anyone being able to gaze with their own eyes from the peaks of Verona Rupes 90 years from now would care.

Oleksa_dr 1y ago

Even if we get there, will there be any benefit to civilization, maybe there are no habitable worlds there and it is not possible to profitably extract valuable resources for future travel. In my opinion, the most realistic thing is to come to an understanding of how our body/brain works. Then learn how to transfer consciousness from a living shell to a machine (with an emulsified environment for nerve endings, and so on). To learn how to print bodies, even if it takes as many years as it takes to grow in natural conditions. Between solar systems or even galaxies, our digital consciousnesses will travel, maybe even copies and once in n years, synchronized in some exact or not. That is, to achieve immortality in a “digital” way, then time will not play a role. Another problem is spacecraft, so that they can travel with sufficient autonomy for hundreds of thousands or even millions of years (this is probably the main problem).

lofaszvanitt 1y ago

Everyone suffers from the sci-fi delusion. We can't solve the problem of large-scale wildfires (sending helicopters and planes to drop water on forest fires is not a viable solution) and we can't even do large-scale terraforming on our own Earth. We have to use containers to transport liquids and solids from one place to another. We cannot control the weather, yet people fantasize about travelling into space. It's delusional, isn't it? It's borderline ridiculous. And we have these human-centric systems that are unusable and inefficient, not to mention a terrible economic system that rewards the virus-like entities in society. We aren't going anywhere.

silverquiet 1y ago
I would say worse than that, we are doing the opposite of large-scale terraforming to create a planet that will be rather inhospitable towards the end of this century and even less so in the centuries that follow. I think the sci-fi delusion is a hold over from a better time; the heyday was probably the 50's-60's when scientific progress seems like it was much greater and was actually able to translate into benefits for people that were noticeable.
- lofaszvanitt 1y ago
  Yeah, and nobody cares, nobody seems to notice, seemingly people who have the power to steer things the right way are totally lobotomized. It's just like in Cyberpunk, where the power couple's brain is getting rewired by "entities", because they go against the flow.