[HN Gopher] Interstellar Flight: Perspectives and Patience
___________________________________________________________________
Interstellar Flight: Perspectives and Patience
Author : JPLeRouzic
Score : 43 points
Date : 2025-06-25 16:35 UTC (6 hours ago)
(HTM) web link (www.centauri-dreams.org)
(TXT) w3m dump (www.centauri-dreams.org)
| KineticLensman wrote:
| > 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 wrote:
| 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 wrote:
| 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-g...
| JumpCrisscross wrote:
| > _the sun is essentially at rest with respect to the rest of
| the solar system_
|
| But not with respect to other star systems.
| KineticLensman wrote:
| 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 wrote:
| > _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.
| agentultra wrote:
| 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 wrote:
| 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 wrote:
| > The universe has a loooooot of stuff in it.
|
| In fact, technically, there's nothing _here_. It 's all out
| _there_.
| jvm___ wrote:
| 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 wrote:
| >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
| NoMoreNicksLeft wrote:
| >Humanity has never been content with staying put, why would
| we start now?
|
| For whatever reason, humanity's attitude in this regard has
| changed drastically in the last century. We can't even bother
| to make the next generations, and a shrinking population
| eventually (quite quickly, really) shrinks to zero. Not only
| do they want to "stay put", they want to lay down and die.
| kibwen wrote:
| The steelman counterargument is that focusing resources on
| extraplanetary colonies at the expense of the one habitable
| planet within reach will _hasten_ humanity 's destruction.
| How are you going to make an Eden on Mars if we can't even
| make an Eden on Earth? The only large-scale planetary
| engineering in humanity's history is Veniforming its home
| world.
| NoMoreNicksLeft wrote:
| >The steelman counterargument is that focusing resources
| on extraplanetary colonies at the expense of the one
| habitable planet within reach will hasten humanity's
| destruction.
|
| That doesn't seem like a strong argument to me. It seems
| like a distraction from the crowd that would save the
| planet by extinguishing humanity if that's what it took.
| Though what value the planet might have with all of us
| gone I leave as an exercise for the reader.
|
| The first priority of any society that wants to continue
| to exist into the future must always be to make the next
| generation. If you do not do this, or if you just leave
| the task to others hoping that someone else will do it,
| then you are behaving in a way that will in all
| probability lead towards there being no next generation
| sooner or later. The "global warming is the apocalypse"
| movement constantly talks about how the best way to
| reduce your carbon footprint is to have no children.
|
| >The only large-scale planetary engineering in humanity's
| history is Veniforming its home world.
|
| So it is claimed, but from my point of view it looks very
| much as if it's intent on making itself extinct through
| fertility decline. But at least carbon dioxide levels
| will return to normal, eh?
| agentultra wrote:
| It's mostly empty, isn't it?
|
| By "literally nothing there," I mean there's literally
| nothing for us. Three stars and a few Earth-sized planets in
| the habitable zone that are, more than likely, uninhabitable
| by humans. There's nothing there worth going all that way
| for.
|
| I like sci-fi as much as the next person but the reality of
| the situation, it seems to me, is that the universe is mostly
| empty, vast, and inhospitable to human life.
| JumpCrisscross wrote:
| > _It 's mostly empty, isn't it?_
|
| So is the Pacific Ocean for practical definitions of
| emptiness. You don't got to the empty places.
| rbanffy wrote:
| The difference between a multi-generational interstellar
| ship and a self-sustaining space colony is the engine. They
| wouldn't need inhabitable planets - they would need raw
| materials to build more ships and habitats.
|
| I'm not sure that after spending a lifetime in an ample
| space colony its inhabitants would feel nostalgic of the
| time we spent sitting on round rocks cooking around a star.
| ta1243 wrote:
| To quote Babylon 5
|
| Ask ten different scientists about the environment,
| population control, genetics, and you'll get ten different
| answers, but there's one thing every scientist on the planet
| agrees on. Whether it happens in a hundred years or a
| thousand years or a million years, eventually our Sun will
| grow cold and go out. When that happens, it won't just take
| us. It'll take Marilyn Monroe, and Lao-Tzu, and Einstein, and
| Morobuto, and Buddy Holly, and Aristophanes, and - all of
| this - all of this - was for nothing. Unless we go to the
| stars
| ninetyninenine wrote:
| The odds are against us. We will never go to the stars. But
| it doesn't matter for us as we will likely die before any
| of this happpens.
| zppln wrote:
| And those stars will go out as well.
| bilbo0s wrote:
| Well true.
|
| That's the fallacy in the given argument.
| rbanffy wrote:
| By then we'd better understand how to implement a "Let
| there be light" procedure.
|
| Might very well be the last question we need to ask
| ourselves.
| mr_toad wrote:
| > There's literally nothing there
|
| "Literally everything is in space."
| AnimalMuppet wrote:
| There was a time when there was nothing (European) in the
| entire New World. There was a time when there was nothing known
| (to the US) about what was in most of the Louisiana Purchase.
| There was a time when there was nothing (European) in, say,
| Ohio. And then Nebraska. And so on.
|
| There was literally nothing there? Why go all that way? To see
| what was there. And then _to make something there._
|
| [Edit, because I'm rate limited: No, interstellar space is
| something to cross, to get to _stellar_ space. You think the
| New World was rich? How about a whole _solar system_ of
| untapped resources?
|
| That's why people will try to go.]
| ta1243 wrote:
| > There was literally nothing there
|
| No there wasn't. There was a whole continent of untapped
| resources.
|
| You can argue that the solar system is a lot of untapped
| resources too. Harder to extract than sailing a piece of wood
| across an ocean growing some food, and killing the people who
| are already there. Harder than colonising Antarctica or the
| surface of the sea too, but there are resources - not just
| minerals but solar energy too.
|
| But interstellar space? Beyond the Oort Cloud? There's no
| evidence of anything other than perhaps some very sparse
| dust. That is nothing, and (jokes aside) completely
| incomparable to Ohio.
| sorcerer-mar wrote:
| They didn't believe there was literally nothing there. They
| went all that way to find unclaimed riches.
|
| The hypothetical riches were quite obvious: same stuff we
| have over here, but not owned by someone yet.
|
| What are they hypothetical riches of outer space?
|
| This is a question we should think about clearly and
| logically without resorting to stuff like "oh tally-ho the
| adventure!" type nonsense.
| rbanffy wrote:
| There is many times more water in gas giant moons than on
| Earth. If we develop the technology needed to make a multi-
| generation ship we also have the technology to make deep
| space habitats - enough for trillions or quadrillions of
| people.
|
| Just imagine the economic output of a civilisation a
| million times the size of ours.
| sorcerer-mar wrote:
| It's a lot easier to imagine the economic output of
| simply raising all of the current Homo sapiens out of
| poverty and into economic productivity, no?
|
| Then we can use all of that new productivity to start
| working toward the next rung?
|
| Our economy is not currently throughput limited on water
| or space so I don't find this compelling.
| os2warpman wrote:
| >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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| more than one basket for those eggs will be important.
| os2warpman wrote:
| I wasn't even considering the sail.
|
| Most of the designs for a system like this are "chip" designs
| where a single 1cm x 1cm silicon wafer is towed by the sail.
|
| This design prevents the need for lasers so large that they
| create enough ozone to kill the entire human race.
|
| The contents of the chip vary, based on who is speculating,
| but tend to contain exotic, uninvented, circuitry capable of
| both harvesting energy from the laser and doing "something"
| of use besides zipping by the target at 0.2c deaf, dumb, and
| blind. Sometimes it's even an AI-enhanced swarm! (Shoulda
| figured out how to work blockchain in there, post-doc guy)
|
| Regardless, during the 40 trillion kilometer voyage to
| Proxima Centauri, that 1x1cm silicon wafer (and the sail)
| will hit space dust, and numerous other atoms and molecules
| (including carbon rings) because empty space... isn't.
| mr_toad wrote:
| Ten megajoules sounds like a lot, but a single kilo of TNT
| produces about 4 megajoules of energy. And the size of
| particles of dust and how often you're likely to hit one in the
| interstellar medium is quite speculative.
| inetknght wrote:
| > _the size of particles of dust ... in the interstellar
| medium is quite speculative_
|
| Technically yes. I think there's a significant variety of
| sizes of dust or larger-than-dust particles in interstaller
| medium but I don't really have much to back that up.
|
| > _how often you're likely to hit one in the interstellar
| medium is quite speculative._
|
| Also technically yes. But unless you can map every single
| particle of dust, and their trajectories, I think the risk is
| absolutely real.
| trhway wrote:
| alternatively you ionize that particle, may be make in into
| plasma by laser for ease of "digestion" down in the engine,
| direct in into the engine where it is used as working mass for
| your ion thruster, kind of similar to scramjet.
|
| As far as i see with today's tech - like Starlink's ion
| thruster + classic nuclear reactor - we can get to 300km/s in
| about 4 stages. Straightforward improvement of ion thrusters -
| mainly voltage increase and associated engineering (which will
| immediately happen once we start flying to Mars and beyond as
| ion thruster currently our best/fastest option inside the Solar
| system) - can get us to 1000-2000km/s, i.e. under 1000 years to
| Alpha Centauri (that for a large populated spacecraft, and for
| just tiny probe to announce our existence (and to send back
| photos which we'd receive using Sun's gravitational lensing) we
| can do even better). And using interstellar gas and dust
| scramjet-style will improve on those numbers (as such ship is
| mostly limited by the working mass it starts with while the
| reactors would be able to continue produce the energy much
| longer).
| JumpCrisscross wrote:
| > _alternatively you ionize that particle, may be make in
| into plasma by laser for ease of "digestion" down in the
| engine, direct in into the engine where it is used as working
| mass for your ion thruster, kind of similar to scramjet_
|
| This is a Bussard ramjet [1]. The interstellar medium is too
| thin to make it work. (Maybe we'll find the husk of an
| ancient ramjet from an earlier era of the universe floating
| around one day...)
|
| [1] https://en.wikipedia.org/wiki/Bussard_ramjet
| trhway wrote:
| Bussard would collect gas to be used as fuel. For ion
| thruster it is only a working mass.
| awongh wrote:
| Are there any real proposals that deal with this issue for a
| vehicle that would carry humans and go fast? Something that's
| not "energy shields".
|
| Edit to add: we basically understand the physics of
| accelerating something to a high speed, what it would need to
| be made from, etc., afaik all within the realm of possibility-
| if we could gather and direct that much energy and then wait
| long enough to decelerate at the other end.
|
| It seems like the questions that are completely unaswered are:
| keeping people alive and healthy for that long, and how the
| ship could survive if it hit something.
| JumpCrisscross wrote:
| > _Are there any real proposals that deal with this issue for
| a vehicle that would carry humans and go fast?_
|
| Whipple shields [1].
|
| > _Something that 's not "energy shields"_
|
| The interstellar medium contains lots of charged particles
| [2]. Electromagnetic deflection is perfectly realistic.
|
| [1] https://en.wikipedia.org/wiki/Whipple_shield
|
| [2] https://www.space.com/interstellar-space-definition-
| explanat...
| umpalumpaaa wrote:
| "A 0.1 um interstellar dust grain ([?]10-14 kg) striking a
| spacecraft at 0.2 c carries [?]20 J of kinetic energy--millions
| of times below "tens of millions of joules." Reaching 10-50 MJ
| would require a [?]0.14 mm grain ([?]10 ug), vastly rarer than
| ordinary dust, and even that impact equals only a few shots
| from the world's highest-energy laser (~2 MJ per pulse), not
| "hundreds.""
| os2warpman wrote:
| I used something something 10^-10 for my dust. To reach
| ~50MJ.
|
| As far as the laser goes, ~2MJ is the total output. Energy
| that reaches the fuel pellet due to inefficiencies throughout
| the path of the laser, the actual "hitting power", is
| hundreds-ish kJ.
| ge96 wrote:
| scifi answer (the particle warps with space around the vehicle)
|
| the other thought is a space ram jet sucking in particles heard
| of some idea like this
| WalterBright wrote:
| 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 wrote:
| 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 wrote:
| What resources are on asteroids that justify the energy
| expenditure to get from space and back? Can't be many of
| them...
| kibwen wrote:
| 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 wrote:
| Wouldn't work because of the collective action problem
| among gold owners!
| JumpCrisscross wrote:
| > _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
| sorcerer-mar wrote:
| Just skimmed but does this answer the question of getting
| to and from the surface of earth? Or are we just
| stockpiling platinum in LEO for some reason?
| JumpCrisscross wrote:
| > _does this answer the question of getting to and from
| the surface of earth?_
|
| Yes. (Deobiting from LEO is cheap, like 90 m/s for the
| Space Shuttle, because you can use the atmosphere.)
| sorcerer-mar wrote:
| ... Presumably the problem is mostly getting _up_ ...? Is
| the plan to just drop hunks of platinum or do we need to
| put reentry vehicles up there?
| pfdietz wrote:
| > With chemical rockets, not much.
|
| The energy involved in chemical rocketry is actually not
| that much. Getting a kilogram to LEO is roughly as
| expensive (in energy) as flying it to the other side of the
| world in an airliner. Getting stuff _back_ from an earth-
| crossing asteroid can also be very cheap energetically,
| with very small delta-V (if one is willing to wait long
| enough).
| tejtm wrote:
| "What resources are on asteroids that justify the energy
| expenditure to get from space and back? Can't be many of
| them..."
|
| I suggest re-framing the the question as the cost of
| preserving the objectively limited and to the best of our
| knowledge singularly unique in the Universe resource, which
| is the surface of Earth.
|
| Acquiring resources that do not deplete or spoil the future
| of life on this planet should be in everyone's best interest.
| sorcerer-mar wrote:
| Yeah no. Unless someone can answer basic questions like
| "what even comes close to net positive in energy
| expenditure to mine elsewhere," then this is just a cover
| story.
|
| The reality is that saving our environment will be a whole
| set of difficult and _profoundly boring_ solutions to real,
| known problems.
|
| Would be cool if we could solve it with badass rockets,
| explosions, big noises, and _adventure,_ but the complete
| lack of even remotely convincing answers to first order
| questions on _how this actually works_ belies the fact that
| it doesn't. It makes no sense.
|
| We need to develop better plastics, proteins, and
| pesticides. Not send protein blobs to other planets because
| it looks cool in sci fi movies.
| JumpCrisscross wrote:
| > _We need to develop better plastics, proteins, and
| pesticides. Not send protein blobs to other planets
| because it looks cool in sci fi movies_
|
| The reality is more people get passsionate about working
| on things that look cool in sci fi movies than developing
| plastics, proteins and pesticides for a mediocre
| paycheque. This lesson--that the path to groundbreaking
| technologies is through inspirational moonshots, not
| committees prescribing what is and isn't necessary--is so
| thoroughly repeated throughout history that it's a wonder
| we keep missing it.
| sorcerer-mar wrote:
| Nobody referenced any sort of committee.
|
| Groundbreaking technologies are not created via
| moonshots. They're created by decades of slog. Moonshots
| can launch from an unremarkable _platform_ of slog, but
| the slog had to happen. You just cannot speedrun the vast
| majority of questions that need to be answered to power a
| breakthrough.
|
| That's why I'll question glory-chasers who want to sit on
| the rocket but can't take a few thousands of pay cut to
| stare for a few years at a true problem that needs
| solving.
|
| Our species' _actual_ heroes are those who powered
| through the slog.
| JumpCrisscross wrote:
| > _They're created by decades of slog. Moonshots can
| launch from an unremarkable platform of slog, but the
| slog had to happen_
|
| The slog is almost always in pursuit of a moonshot. The
| moon justifies the slog. We don't slog for the sake of
| it.
| trhway wrote:
| Our civilization has been driven by expansion. Without it we'd
| probably collapse into a neurally-connected well-organized ant
| colony without need for further technological/social/economic
| progress (which would naturally select/cull out corresponding
| features in our brain). And, i'd guess that is possible one of
| the forms of the Great Filter stopping many civilizations.
|
| At 53 and good health, i'm contemplating that my end in 30-40
| years would be me buying a one way to Mars and just exiting the
| habitat out without suit after enjoying a dinner with a Martian
| sunset view, breaking, even in such a small way, the chains of
| "We come from the earth, we return to the earth" :)
| sorcerer-mar wrote:
| That's a truly awful way to die (all your fluids and gases
| suddenly surging through your tissue).
|
| Seems much easier to reframe the "chains" of earth into
| acceptance of a remarkable cycle that we're privileged to get
| a glimpse of from the inside and just die happily here with
| your loved ones.
| JumpCrisscross wrote:
| > _Seems much easier to reframe the "chains" of earth into
| acceptance of a remarkable cycle that we're privileged to
| get a glimpse of from the inside and just die happily here
| with your loved ones_
|
| This works for most people. Most humans didn't leave Africa
| or Mesopotamia or the Old World, either originally or in
| the Age of Exploration, and most Americans today don't have
| a passpport.
| trhway wrote:
| The technicalities would be worked out. The awfulness isn't
| a goal here.
|
| The acceptance would have me still in Russia :)
| sorcerer-mar wrote:
| Presumably you left Russia to get to something _better_ ,
| not worse on pretty much every dimension except novelty
| trhway wrote:
| Yep, and dying on Mars feels to me better than on Earth.
| sorcerer-mar wrote:
| On what dimensions would that be preferable?
| JumpCrisscross wrote:
| > _On what dimensions would that be preferable?_
|
| Novelty, for one.
| sorcerer-mar wrote:
| Yeah, makes sense. Novelty like what toys provide!
|
| Obviously one is free to want that. When I think of the
| opportunity costs involved, it seems repugnant to be
| honest. The opposite of glorious.
| trhway wrote:
| That is about my point - i want to get as far as possible
| from such a philosophy as it is taking over the
| civilization. I lived under similar philosophy in USSR
| and, as long as it is up to me, i'll be trying to put a
| distance in all senses.
| JumpCrisscross wrote:
| > _Yeah, makes sense. Novelty like what toys provide!_
|
| And art and scientific endeavour and exploration and
| possibly all the things that make us human, but sure.
| madaxe_again wrote:
| I don't know, GPS is quite useful, Landsat is too, along with
| the various other Earth imaging satellites and systems like
| modis and sentinel-2. Sure is good having food. Weather
| forecasts are nice. It's also quite convenient to be able to
| use space based data services. It's also useful for power grids
| to know when they're about to be whacked by a CME. I'm sure
| sailors on sinking ships appreciate being rescued.
|
| But sure, we should solve all the problems on earth with one
| hand tied behind our backs until we can launch any more
| rockets.
| usuallyalurker wrote:
| Not only is that comment a false dichotomy (we can both explore
| space _and_ make humanity more sustainable at the same time),
| it also presumes that space exploration and sustainability are
| at odds with one another and not synergistic.
|
| Humans, simply by existing on Earth, have a huge and often
| negative impact on the environment. If we could somehow shift
| the human population off Earth, either by terraforming planets
| (like Mars) or creating artificial space habitats, it would
| have a huge positive impact on Earth's environment. We don't
| currently have the technology to do so - we would need space
| elevators to feasibly move humanity off Earth - but that
| doesn't mean we should move our attention away from space in
| the meantime.
| econ wrote:
| 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.
| d_silin wrote:
| 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 wrote:
| > _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/20...
|
| [2] https://www.nasa.gov/mission/acs3/
|
| [3] https://en.wikipedia.org/wiki/Silent_Hunter_(laser_weapon)
| carpdiem wrote:
| 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 wrote:
| > _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/
| pfdietz wrote:
| However, travel at 0.1c is not needed for the Fermi Argument to
| bite. Much slower speeds would allow a colonization wave to
| sweep a galaxy in time << the age of the universe.
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