[HN Gopher] A Roadmap to Interstellar Flight (2016)
___________________________________________________________________
A Roadmap to Interstellar Flight (2016)
Author : ra7
Score : 139 points
Date : 2021-07-08 16:25 UTC (6 hours ago)
(HTM) web link (arxiv.org)
(TXT) w3m dump (arxiv.org)
| cletus wrote:
| Wow, that's a really comprehensive, deep and dense collection of
| information.
|
| For anyone really interested in the science of this who doesn't
| necessarily want to digest the raw math, I highly suggest Isaac
| Arthur's Youtube channel eg [1][2].
|
| People tend to fall into a number of traps when dipping their
| toes into this topic.
|
| The first one is the trap of wishful thinking, which is the
| primary reason for pretty much any attempt to come up with a
| theory for FTL. Most of these people just don't understand what
| the domain of a function is. Just because you can plug a negative
| number into an equation that is otherwise over real numbers
| doesn't mean that makes sense or is valid.
|
| Second, people oversimplify. I see on this thread and others
| claims like "if we just accelerate at 1G we can get pretty much
| anywhere relatively quickly". So that's true superficially but
| the energy requirements for that are so vast even if you have
| perfect mass to energy conversion that a significant percentage
| of your ship's mass is fuel.
|
| To me, laser highways seem like the most likely form of far
| future interstellar travel. That's largely predicated on
| commercially viable fusion power however and that's not a given.
|
| Failing that, you're talking about variations of what are
| essentially generational ships.
|
| [1]: https://www.youtube.com/watch?v=wXiitWK_6Qg
|
| [2]: https://www.youtube.com/watch?v=s6BQSgidbmc&t=1526s
| [deleted]
| nerpderp82 wrote:
| I love the idea of the wafersats
|
| > Thus a 1 kg spacecraft going at 0.3 c will have an effective
| "yield" of 1 MT or roughly that of a large strategic
| thermonuclear weapon.
|
| Lets not accidentally wipe out a neighbors city and start an
| interstellar war.
| iso1210 wrote:
| A tungsten rod placed in an eliptical polar orbit can be
| pointed to any point on earth fired without anyone detecting
| it, and have total plausible deniability when wiping a city off
| a planet.
|
| We're far more likely to have destroyed ourselves long before
| we get a chance to destroy any other civilisation. If we can
| travel intersteller, we can destroy a planet.
|
| Your quote does remind me of a line from Independence Day I
| like
|
| "Los Angelinos are asked not to fire their guns at the visiting
| spacecraft, you may inadvertently start an intersteller war"
| htrp wrote:
| Any fractional-c attack will be either impossible to detect,
| or impossible to prevent....
| paparush wrote:
| obiligatory https://www.intelligentliving.co/amp/speed-light-
| slow/
| EricE wrote:
| The exoplanet mission from Civilization 6 in real life - what a
| fascinating read!
| JoeDaDude wrote:
| A lot of this sounds like the Breakthrough Starshot initiative
| ideas. I could not find out if the author affiliated with said
| initiative.
|
| https://breakthroughinitiatives.org/initiative/3
| JoeDaDude wrote:
| Let me correct myself. Phil Lubin (the author) is on the
| Starshot Advisory Committee. He is so listed in the Bidder
| Briefing slides for the Starshot Sail RFP.
| cecilpl wrote:
| To be honest this is one of the more real proposals I've seen for
| an Interstellar probe, and there are still many problems to be
| worked out as both the paper and the comments here point out.
|
| I admire the optimism in the paper though, even if its misplaced.
| Maybe pooling together resources in the scientific and
| engineering communities to develop an interstellar probe system
| could give a working result, but there are some significant
| hurdles to overcome first. It would be a big project, taking many
| years to see fruition, but at the same time it could also be a
| game-changing development and a hugely inspiring feat.
|
| Could we see probes in other star systems by 2075? I think its
| not an unreasonable suggestion.
| Robotbeat wrote:
| Interstellar flight is an insane challenge. It's one of the
| hardest things humankind can attempt yet still not beyond the
| laws of physics. That means you have to approach things from
| first principles and often have to invert the problem ("assume
| we manage interstellar flight by 2075. How did we do it?",
| etc). It's intellectually seductive in the best way.
|
| I think it's good to attempt such challenges, even if just
| conceptually, as it makes lots of other things seem a lot more
| achievable in contrast, sometimes almost laughably so.
| ryandrake wrote:
| I've always thought interstellar probes were kind of
| pointless. Even if the probe could average 10% of the speed
| of light, the amount of time it would take for a probe to
| reach its destination (all but the closest stars) and then
| for data to return at the speed of light is greater than the
| lifetime of anyone who wants to study. You'd have to send out
| the probe, hoping that your grandchildren wait around for the
| response.
|
| Interstellar space exploration will likely be manned-only. As
| other threads point out, with sufficient acceleration, due to
| time dilation, humans can reach distant stars within their
| own lifetimes (at the expense of thousands of years passing
| on Earth).
| sdwr wrote:
| Doesn't look so bad once a program is established. It's
| like aging cheese - get one batch started while another is
| finishing up. The turnover time is just 50 years instead of
| 2.
| nickik wrote:
| I disagree. It the same principle as sending something to
| the outer solar system. Many of the scientist who propose
| those things and work on the instruments and so on have
| long left the field by the time the missions arrive and
| many will soon after. Before the mission ends, a whole new
| group of people are working on it.
|
| This is the same idea, you send a new an improved probe
| every 10-20 years and eventually you get data back and over
| time you have constant data stream from all kinds of
| different places.
| xyzzy123 wrote:
| Humans have planned and executed multi-generational
| projects before, even if that scale of project seems out of
| fashion right now.
|
| This article (Starships & Cathedrals) explains the ideas
| better than I can in a short comment: https://www.centauri-
| dreams.org/2020/07/17/the-cathedral-and...
| WJW wrote:
| > You'd have to send out the probe, hoping that your
| grandchildren wait around for the response.
|
| Why would our grandchildren be less interested in
| interstellar exploration than we are? We need ways to
| organize (parts of) society for the long term, that seems
| way easier than inventing magical "accelerate at 1g for a
| decade" tech.
| Robotbeat wrote:
| Disagree. At 0.1c, it takes 42 years to reach Proxima
| Centauri (and 4 more years to get data back). The Voyager 1
| and 2 probes are still operating and transmitting
| scientific data that people are interested in (the missions
| are still funded) and were launched 44 years ago and are
| likely to continue a few more years. So we have existence
| proof that people would still be interested in it over that
| kind of timeline.
|
| And I know you excluded the "closest stars," but I don't
| understand why, except that it undermines your point. There
| are at least 3 nearby stars that could be reached by probes
| in a researcher's (or at least their funding institution's)
| lifetime vs just our one star system.
|
| (Besides the 3 stars in the Proxima/Alpha Centauri system
| there are also at least 11 additional stars--including
| fusion-capable brown dwarfs--within 10 light years of the
| Sun.)
| jcurbo wrote:
| Related: https://hub.jhu.edu/magazine/2021/spring/apl-
| interstellar-pr...
|
| (Disclaimer, I work at APL, but not on this)
| davedx wrote:
| Little toy tool I made to sim out various known propulsion
| systems for a crewed interstellar mission:
| https://redskyforge.com/interstellar/
|
| Only nuclear is really interesting. Chemical rockets are useless
| at this scale.
| Robotbeat wrote:
| Beamed propulsion of some sort (not necessarily using lasers)
| relying primarily on solar energy is the best option. Nuclear
| is useful for ancillary propulsion. Chemical not useful except
| for launching all the stuff around the solar system to build
| such a system.
| pault wrote:
| But how do you stop?
| Robotbeat wrote:
| Braking against the interstellar medium (and possibly the
| stellar wind as you get closer) using magnetosail-like
| devices... between the stars isn't completely empty but has
| a diffuse plasma that can be pushed against magnetically or
| electrostatically. This is how you'd slow down in pretty
| much any scenario as it is "propellantless." It's a big
| challenge to get the superconducting coils light enough,
| but it is a critical piece to interstellar flight,
| particularly if crewed.
| davedx wrote:
| I actually ran numbers on electrosails to decelerate,
| they do not work, at all - many orders of magnitude.
| Email me for spreadsheet. Pulsed nuclear propulsion is
| the only tech we have that works
| Robotbeat wrote:
| Electrosails aren't as good for this as magnetosails; I
| just included electrosails for completeness.
| AnimalMuppet wrote:
| Well... I like the beamed energy idea. It works to get you
| out of the solar system. But how do you continue to
| accelerate from other stars? You fire ahead of you a
| construction kit for a solar-powered beam-generating
| station. That beam station can be used either for
| acceleration or for braking.
|
| But how do you get the _kit_ to decelerate? (Remember, you
| fired it ahead of the ship.) And this problem gets worse as
| the velocity of the ship goes up. If, say, your
| construction kit enters a solar system at 0.1 c, it 's
| going to cross it in maybe twenty days. I don't think
| that's enough time for a solar sail to effectively
| decelerate it. It's probably going too fast for using
| planets' gravity to slow it down. And using atmospheric
| drag is an explosively bad idea.
|
| I don't have an answer...
| htrp wrote:
| Your braking laser kit is fired out 1000 years ago....
| and you hope it makes it there on time
| andyxor wrote:
| Unless we embrace nuclear energy for space flight this would
| never happen.
|
| Looks like NASA is developing thermal nuclear rocket
| https://www.nasa.gov/directorates/spacetech/nuclear-propulsi...
| ncmncm wrote:
| Thermal fusion rockets, meanwhile, languish. The Princeton
| group got some money, but under current plans cannot hope to
| fly a test vehicle before 2035. Yet another victim of the
| Tokamak mirage.
|
| Field-reversed configuration, D-H3, aneutronic.
| m34 wrote:
| Propulsion aside, I really wonder what the human species turns
| out to be like in say a couple of hundred years.
|
| Hopefully our solar system isn't the only place where human DNA
| is found; that said, I'm curious what'll be left of humans as we
| know today.
|
| With tools like CRISPR accelerating adoption to new environments
| and increased resilience towards hostile situations (zero-g,
| radiation etc)
| hughw wrote:
| Getting there is "easy". But if the wafer is speeding at _c_ /4
| past the exoplanet, it will not be able to take any measurements.
|
| _4.2 Braking to Enter Orbit on Arrival - A very difficult
| challenge is to slow the spacecraft to typical planetary orbital
| speeds to enable orbital capture once arriving. This task is
| difficult as the initial entry speeds are so high (~ c) and the
| orbital speeds are so low (~ 10-4 c). Dissipating this much
| energy is challenging. We have considered using the stars photon
| pressure, the stellar wind (assuming it is like our own solar
| system), using the magnetic coupling to the exo solar system
| plasma. None of these techniques appears to be obviously able to
| accomplish this task and much more work and simulation is needed.
| A simple fly-by mission is clearly the first type of mission to
| explore in any case to assess the environment in a given system
| to design (if possible) an optimized braking strategy._
| lmilcin wrote:
| I think the best chance for large projects is a fleet of drone
| factories that can replicate themselves and extract resources
| from asteroids. Millions of tonnes of fuel and other resources
| may not be a huge problem if you factor geometric growth of
| population of drones.
| ziotom78 wrote:
| The big problem with near-light speed travel like the one
| suggested by Lubin is the potentially fatal interaction of the
| spacecraft with interstellar dust. Even considering their faint
| density, the long journey would make the spacecraft interact with
| far too many high-speed dust particles, which would likely cause
| significant damage.
|
| I do not know if somebody devised a solution to this fundamental
| problem; if not, I am extremely skeptical about highly-
| accelerated spacecrafts.
| MR4D wrote:
| People really don't get this, unfortunately.
|
| I always think that if f=ma, then as velocity approaches light
| speed, the deceleration of the grain of sand as it hits the
| hull approaches infinity. So even with a small mass, the force
| is huge.
| Johnny555 wrote:
| If we could solve the energy problem, humans could go pretty much
| anywhere in the galaxy on a 1G ship. (ok there are other issues
| like actually building the ship, supplies (or a biosphere that
| can support life for decades), shielding, but that's all easier
| with unlimited energy).
|
| For example, a ship could travel 1,000 light years to the Orion
| Nebula in only 15 years (as perceived by those on the ship). And
| since they are living in 1G, a lot of the detrimental effects of
| long-term space travel are eliminated.
|
| Of course, to an observer on earth the trip would take over 1000
| years, so don't expect to hear how the trip went.
| jonplackett wrote:
| How much energy would that be for that trip, for a reasonably
| sized space ship to take care of a crew for that long?
|
| Are we talking miniature fusion drive or antimatter type energy
| density required?
| Johnny555 wrote:
| I haven't done the calculations (which would be hard to do
| without knowing how big/heavy the ship needs to be), but I'd
| assume it's going to need something well beyond our current
| technology.
|
| An aircraft carrier is powered through the water
| (horizontally, of course) for 25 years on nuclear power.
|
| Now imagine the power it would take to make it hover for 25
| years, and that's your 1G ship.
| NortySpock wrote:
| You could do the "spinning drum" kind of 1G gravity, and
| save fuel that way.
| rootusrootus wrote:
| You still need something like the 1G acceleration,
| though, for the travel part. If you want it to happen
| within a single human lifespan.
| Johnny555 wrote:
| Without the 1G of acceleration, you're limiting how far
| you can go in a single generation. At 0.1g, that 1000
| light year trip would take 90 years (to those on the
| ship). The beauty of 1G is that it provides normal
| gravity _and_ you can go great distances in a human
| lifespan. Of course a 2G trip will get you there in half
| the time, but it 's harder for humans to live at 2G.
|
| Though maybe the time to the destination is not a problem
| if you don't mind a generational ship where generations
| of humans live (and die) on the journey. It doesn't
| matter to those on earth, since the trip will still take
| over 1000 years in their timeframe, so whether it's 1015
| years, 1100 years or 2000 years probably doesn't really
| matter to them.
| ClumsyPilot wrote:
| "The beauty of 1G is that it provides normal gravity and
| you can go great distances in a human lifespan."
|
| It like unicorns - beatifull and entirely fancifull.
| Fusion or fission cant do it, even a ship with pure
| antimatter drive cannot accelerate like that for decades
|
| We will have hibernation before we have practical
| antimatter, and lets you travel intersteller without
| wasting enegy
| AnimalMuppet wrote:
| > even a ship with pure antimatter drive cannot
| accelerate like that for decades
|
| Sure it can. You just need a decently-sized asteroid and
| an equally-sized antimatter asteroid for fuel, and you
| can do it for decades, even with the price you pay early
| to accelerate the fuel you will use later.
| iso1210 wrote:
| If you could somehow accelerate at 1G indefinitely you
| can get anywhere in the universe in a human lifespan.
|
| Of course to accelerate a 1000 ton spaceship you'd need
| about 4 quadrillion tons of fuel.
| gorgoiler wrote:
| The 1G in this case is the acceleration towards your
| target star system at 10m/s^2 until you are half way,
| then decelerating at the same rate until you arrive.
|
| The fact that this _also_ produces liveable conditions is
| just a nice side effect of a 1G ship.
| AnimalMuppet wrote:
| But does that get you to the Orion Nebula in 15 years? Or
| do you have to accelerate all the way to do that? (And
| then you get to wave briefly at the Nebula as it goes
| cruising by at a significant fraction of the speed of
| light?)
| numpad0 wrote:
| Subjectively in decades due to relativity by constantly
| accelerating, objectively in a millennia or worse. Wonder
| how to get around interstellar obstacles though, changing
| courses would be plain impossible
| Johnny555 wrote:
| Large interstellar objects are, well, large, so you can
| see them well in advance and just steer around them.
|
| _changing courses would be plain impossible_
|
| You can steer by vectoring your acceleration. It would
| take about 3 days for a 1G ship to travel from the Earth
| to the Sun, so it wouldn't add much time to the journey
| to steer around an object the size of the sun. Ideally
| you'd identify those objects so far in advance that it
| would take little course correction to go around them.
|
| Smaller objects like asteroids that are too small to see
| in time to avoid would need to be absorbed by the
| shielding or destroyed or pushed away by some other
| method. At near relativistic speeds, this would obviously
| be a non-trivial problem to solve, but hey, you have
| unlimited energy to solve it.
| AnimalMuppet wrote:
| But the faster you go, the more the galaxy is Lorentz
| contracted from your frame of reference, and therefore
| the denser the stars are, so dodging gets harder. Also,
| they're coming at you faster, so you have less time to
| dodge.
| WJW wrote:
| > and therefore the denser the stars are, so dodging gets
| harder.
|
| Not sure this is true, since the stars also get "smaller"
| and therefore harder to hit. Also, while you have less
| time to dodge you also don't have to dodge "as much"
| since your vast speed means you move through any zone
| quite quickly and therefore don't have much time to heat
| up/get irradiated. You can probably pass by a star
| relatively closely as long as you are moving fast enough.
| (From a heat/radiation perspective, solar wind particles
| might still mess you up good)
| AnimalMuppet wrote:
| The stars only get smaller in the direction you're
| traveling. Perpendicular to that (that is, in the
| direction you have to dodge), they don't change no matter
| what your velocity is.
| mike_hock wrote:
| But is hitting a star (or a planet) head on a realistic
| risk?
| gorgoiler wrote:
| Relativity means that by the time your space kids are on
| to the second generation of space labrador, you'll be
| there.
|
| To a static observer, 1000 generations of labrador will
| have been bred back on Earth.
| Johnny555 wrote:
| _Or do you have to accelerate all the way to do that_
|
| That's what "1G" means in this concept, you're always
| accelerating at 1G (9.8 m/sec^2)
|
| On the first half of the trip you're accelerating toward
| the destination, on the second half, you're decelerating
| at 1G.
|
| https://en.wikipedia.org/wiki/Space_travel_using_constant
| _ac...
| AnimalMuppet wrote:
| The graphic in that article is what I wanted.
|
| My point was that, due to the highly non-linear time
| cost, it takes much less time to travel from Earth to X
| if you accelerate the whole way, rather than accelerate
| half the way and decelerate the other half. I wanted to
| know which way gorgoiler used to compute the subjective
| time.
|
| And, thanks to your link, now I know.
| jandrese wrote:
| If the rocket equation still applies (if a practical
| reactionless drive has not been invented), then you're
| talking about mass-of-the-galaxy size spaceships to
| accelerate at 1G for years on end.
| whatshisface wrote:
| The linked paper describes a laser propulsion system by
| means of which no reaction mass need be stored on the
| spacecraft whatsoever.
| jandrese wrote:
| Which is impractical because you don't have a way to slow
| down at the end. Their big plan was to accelerate a
| camera up to 1/4c and have it snap pictures as it whizzes
| past the solar system.
|
| It's also far less than 1G acceleration. You don't get
| big acceleration figures like 1G from laser pumped solar
| sails.
| nerpderp82 wrote:
| If you take your whole civilization with you, it doesn't matter
| how fast or slow you go, you are already where you need to be.
| coderintherye wrote:
| Civilization is a believed concept. Physically taking all of
| your people with you does not equate to maintaining
| civilization.
| ryandrake wrote:
| This thread is reminding me of one of my favorite Clarke
| books, which partially explores this theme: The Songs of
| Distant Earth [1]. Is there such thing as a singular human
| civilization, once it become split by great distances and
| millennia?
|
| 1: https://en.wikipedia.org/wiki/The_Songs_of_Distant_Earth
| rbanffy wrote:
| It's an excellent book. Mike Oldfield made an excellent
| soundtrack for it, and Clarke wrote the insert for the
| disk.
| nerpderp82 wrote:
| Humanity will diverge as soon as we have off Earth
| reproduction.
| robotresearcher wrote:
| We are there right now, zipping through space together.
|
| We have some social problems and some HVAC problems. But the
| vehicle is already underway.
| nerpderp82 wrote:
| You might enjoy this video on terraforming Venus,
| https://www.youtube.com/watch?v=G-WO-z-QuWI
|
| I think we should consider the whole solar system our
| galactic ship while making sure to keep the current
| habitation quarters in top notch shape.
| ben_w wrote:
| Energy is the biggest problem, but it's far from the only one.
|
| Consider the ISM: at 0.086 c, ionised helium is the same thing
| as 14 MeV alpha radiation. Low density regions within the
| galaxy are 0.2-0.5 particles/cm^3; 0.2/cm^3 * 0.086 c is ~5e12
| particles/m^2/second, or about 9.9 watts/m^2 if it was all He4
| and therefore 14MeV/particle or about 2.5 W/m^2 for Hydrogen at
| the same speeds, which is bad enough given what keeping that up
| for years will do to any solid hull, but molecular clouds can
| be 10^2-10^6 particles/cm^3 and the upper bounds of that is ~10
| MW/m^2.
|
| Even without Relativity (which makes it worse), if you double
| the speed the kinetic energy per particle quadruples _and_ you
| also double the number of particles per unit time.
| trhway wrote:
| ionized particle moving in your frame can be recovered as
| energy while the particle itself can be used as reaction mass
| (He) or even as fusion fuel (H).
| ncmncm wrote:
| First, you have to ionize it all.
| trhway wrote:
| required ionization energy is dwarfed by the particle
| kinetic energy to be collected which is in MeV.
| generalizations wrote:
| Which, to me, is why we should be focusing on new ways to
| produce energy. Solar and wind is nice, but we could
| revolutionize humanity and save the earth if we found a way to
| build cheap energy sources with a density of gigawatts per
| cubic yard.
|
| What better way to save the earth and solve the population
| problem than to have the energy production capabilities to
| simply build e.g. ringworlds? Even that's not out of the realm
| of possibility with that kind of energy available.
| nickik wrote:
| WE already did that. Its called nuclear power. Fission energy
| can do almost everything fusion can do. The difference in
| energy density between fission and fusion is not that large
| compared to the energy sources we have.
|
| With all the investment in solar and wind we could easily
| have built a fission based economy. The French proved that in
| the 70/80s and had a green grid ever since.
|
| Had we done that collectively global warming would be a far
| lesser issue.
|
| It would also help us understand neutronics and material
| science so we can eventually switch to fusion.
|
| The same basic technology could also be used for space travel
| in the solar system and would have advanced space travel by a
| lot.
|
| But of course for idiotic reasons society went away from
| that.
| ncmncm wrote:
| Idiotic reasons such as that nuke always turned out, on
| examination, to cost much more than alternatives.
|
| Much of that high cost is often wholly-legal corruption
| that attaches to almost any large, centralized, hard-to-
| account public-money expenditure. Knowing this does not
| help. Thus far, solar and wind projects have mostly avoided
| the corruption tax by their simple accounting framework: N
| generating units x $C per unit = $CxN; and by their clear
| value proposition: $CxN is lately, and still increasingly,
| _much less_ than alternatives whether those are figured
| with corruption tax included or not.
|
| At this time it is cheaper to build out a new solar-and-
| wind farm and operate it than to continue just to operate a
| comparable nuke, wholly neglecting construction and
| decommissioning cost. We finally got the ramshackle Diablo
| Canyon and Indian Point contraptions shut down, but it will
| still cost a $billion to take them apart; or, likely, more,
| according to the degree of corruption tolerated.
| Nitramp wrote:
| FWIW, fissible material that's used with current technology
| is actually running out, with a similar timeline to oil.
| Fission is not an infinite energy source, despite
| appearances to the contrary. It's also not an cheap as one
| might hope.
| bbojan wrote:
| But the current technology can be improved at least 100x
| (fast fission) to 10000x (breeders).
| arcanon wrote:
| I think there is one more step change theoretically
| possible in terms of energy output which is based on anti-
| quark collisions. We need to understand QCD better. Its
| hard to know when breakthroughs will happen. Maybe its
| already happened and we just havent heard about it yet!
|
| We also dont know how to model quantum gravity still. That
| seems pretty fundamental.
|
| Im optimistic there will be physicists who find something
| new and whacky that no one could predict.
| rmu09 wrote:
| All this cheap energy eventually turns into heat. The only
| way to get rid of excess heat is to radiate it into space,
| and the only way to radiate _more_ heat into space is with an
| increased temperature.
| bliteben wrote:
| I love this somewhat tangentially related article:
| https://dothemath.ucsd.edu/2012/04/economist-meets-
| physicist...
| RustyConsul wrote:
| That might be a blessing on mars.
| ant6n wrote:
| I'm a little confused. Are you proposing to Save this world,
| or build/settle others?
| Robotbeat wrote:
| Yes? If the latter is accomplished, the former becomes
| trivial.
| TomSwirly wrote:
| What?! Why?
|
| How will settling Mars or any planet save the biosphere?
|
| We have a few decades to not kill the planet. Settling
| another planet would take centuries.
| DoreenMichele wrote:
| I think the idea they are suggesting is that if we can
| figure out how to terraform Mars and create a livable
| atmosphere from scratch, the tech and domain knowledge
| created along the way means cleaning up our atmosphere
| should be easy in comparison.
|
| Kind of like Olympic gymnasts lift weights and work on
| flexibility and they want to exceed what their
| performances require such that the performance is easy
| and not pushing them to the limits of their ability.
|
| Ie "You have to crawl before you can walk. If you learn
| to run, walking becomes trivial in comparison."
|
| If that makes sense.
| runarberg wrote:
| This analogy only makes sense if the world's problems
| were that of technology. We have ample evidence that it
| is not.
|
| There exists technology that can transport people over
| short to medium distances really efficiently and without
| much greenhouse gas emissions. All it would take would be
| for policy makers to allocate some funding to build out
| the infrastructure required, yet they don't.
|
| There exists technology to transport and distribute food
| wherever there is hunger. Even technology to grow food
| more efficiently and without additional greenhouse gas
| emissions. Yet we don't apply that.
|
| Most countries continue to pour money into their most
| devastating government institutions (the military and the
| police) that not only cause a world of societal problems
| on their own, but also pollute a bunch in the meantime
| for everybody else. At the same time they could be using
| that money to build infrastructure that would allow us to
| live a more sustainable lives. But they don't.
|
| If the technology existed that would take people to
| Proxima Centauri in 10 years, and we invented a bunch of
| good technology that would help us make our current world
| better. I bet this new technology would be used equally
| sparingly as our current technology.
| DoreenMichele wrote:
| I don't actually disagree with you. But I also know that
| a lot of tech in use today was born of our efforts to
| solve problems in space exploration, so I also don't
| entirely disagree with the line of reasoning that space
| exploration requires us to meet such a high bar that
| inventions that grow out of it end up being essentially
| _trivial_ to implement here on earth.
|
| I'm personally heavily invested in the pieces of the
| puzzle that tech, per se, cannot solve. My work in that
| regard gets little in the way of attention and people
| have long attacked me as a nutter, etc.
|
| I run a citizen planners forum on Reddit. I try to write
| about local community development at eclogiselle.com.
| Sometimes something I wrote gets a few thousand page
| views, but most of what I write gets very little traffic
| and that seems to be generally trending down, not up.
|
| And I have mixed feelings about that because I have
| actively sought to ditch traffic rooted in lurid interest
| in me, so that's sort of "huzzah. I win? I guess."
|
| I would like to see more focus on passive solar design. I
| would like to see more development of missing middle
| housing. I would like to see more walkable, bikable
| communities where Americans can actually live without a
| car.
|
| I would like to see social change of the sort that's
| needed to actually solve these problems with the
| currently available tech. The problem I see is that tends
| to require a charismatic leader of the sort that
| historically founded various religions and I see problems
| with that approach.
|
| I think it's inherently problematic to just take
| someone's word for it and do as you are told because they
| said so and you basically worship them. People need to
| think for themselves, not dutifully do as they were told.
|
| And I don't know how you put out good info to foster the
| right kind of change in the amount needed etc and do so
| in a way that sidesteps the tendency for leaders of any
| sort to dictate what others should do.
|
| So I have kept my footprint intentionally small in some
| sense while I figure out best practices. "If you don't
| have time to do it right the first time, when are you
| going to find time to do it over?"
|
| Best.
| soheil wrote:
| Can someone do the math to calculate the energy needed for a
| ship like this to accelerate near the speed of light? I suspect
| the amount of energy may exceed what's available even if we
| were to capture all energy generated from the sun.
| jandrese wrote:
| It's not even the energy that is a problem, it is the mass.
| The rocket equation is a harsh mistress.
| soheil wrote:
| But more energy is the only thing that is needed when mass
| is increased, so not sure why it wouldn't all boil down to
| energy?
|
| Unless you're talking about escaping Earth specific
| gravitation.
| jandrese wrote:
| Are you talking about kicking your reactant so hard that
| it picks up significant amounts of relativistic mass?
| soheil wrote:
| Haha no but I'm not assuming the rocket equation is
| applied in Earth's gravitation, but maybe the spacecraft
| could be built far enough from any plants to be impacted
| by an initial gravitational field.
|
| If nuclear energy is used, it can be increased in less
| than linear change in mass.
| jandrese wrote:
| Regardless of what you use for power a rocket has to
| eject mass from the rear to propel you forward. Newton's
| second law.
|
| The problem is that as you increase burn times (like
| years at 1G), you need to increase the amount of mass you
| are pushing out the back. But to do this you increase the
| mass of your rocket which means you need to push even
| more mass out and it becomes a vicious circle of
| exponentially increasing rocket mass.
|
| The idea of accelerating at 1G for the entire trip only
| works if you have a source of propulsion that doesn't
| obey Newton's second law. Otherwise there literally isn't
| enough mass in the galaxy to make it work. The caveat
| being that if you can somehow exploit relativistic mass
| to effectively multiply your fuel it might be possible,
| but my math isn't good enough to work it out. My gut
| feeling is that it would require an unreasonable amount
| of power however, even for an extremely powerful nuclear
| power plant.
| davedx wrote:
| Not true. Generating energy is only part - propulsion is hard
| too. Even if you had a bunch of anti-matter, how do you build a
| spacecraft that can safely transport humans for years with a
| propulsion and storage system that uses it? How do you use M-AM
| annihilation usefully? It's not like Star Trek.
| BelenusMordred wrote:
| With antimatter propulsion you'd want to use it as its
| generated rather than the messy business of trying to store
| it.
| Johnny555 wrote:
| Just having a chunk of anti-matter isn't really "solving the
| energy problem", obviously you need to harvest the energy,
| but I think that given nearly unlimited energy, propulsion is
| a much easier problem to solve.
|
| One possibility is:
|
| https://en.wikipedia.org/wiki/Robert_W._Bussard#Bussard_ramj.
| ..
| BelenusMordred wrote:
| > a lot of the detrimental effects of long-term space travel
| are eliminated
|
| Apart from the fact that everyone you know is now dead and if
| you returned home you'd basically be a living caveman museum
| piece.
| shpx wrote:
| Time traveling and seeing what Earth looks like 1000 years
| from now by spending 30 years in a metal can (and expending
| an astronomical amount of energy) is a trade I would
| consider.
| Johnny555 wrote:
| It's obviously a one way trip, no one would expect to return
| home (at least, not to the same home that they left, in 2000
| years, human civilization may not even exist when they
| return, they could return to a planet colonized by Apes...
| hey, they would make a great movie!).
|
| But one-way trips have been proposed for planetary
| colonization as well, and there are a lot of people that
| would be willing to make that trip.
| numpad0 wrote:
| I think we'll probably be having subspecies of humanity like
| Homo Sapiens Destinationshipnamehullnumberius
| nynx wrote:
| Just solve the aging problem first. That seems to be pretty
| close at hand anyhow.
| AnIdiotOnTheNet wrote:
| It seems to me the most likely scenario is that we perfect
| the ability to copy minds into an electronic computer
| system. Such a digital mind would no longer need most of
| the resources a human body would and could potentially last
| nigh-indefinitely. It would also be able to take advantage
| of both >1G (no flabby meat body) and <1G (no aging)
| constant accelerations. Further, a colonization effort by
| digital beings would only require raw resources to build
| more electronics and starlight for power, which expands the
| number of habitable places from "planets with human
| survivable conditions" to "basically anywhere near a star".
| kybernetikos wrote:
| Are there any software, hardware or cloud providers
| currently existing that you would trust to run your
| consciousness?
| arcanon wrote:
| It seems trivializing and like an existential crisis to
| have all of a humans being encoded in a computer. Once
| you have that, why even keep it running for all time as
| it is? Its just a version of software you could make
| changes to. We are probably not as glorious as we could
| be to become immortal as we are.
| mcculley wrote:
| I am not convinced there is any solution to aging. When I
| was a child, I read headlines that claimed a solution was
| close at hand. We seem only marginally closer to
| eliminating aging.
|
| Importantly, how many memories do you think can fit into a
| human brain? If a 1,000 year old man cannot remember all of
| his life, has aging been solved?
| cousin_it wrote:
| One of my favorite ideas is having a pair of mirrors, one on the
| spaceship and another on Earth. Then shine a laser on the ship,
| it will bounce back and forth, and eventually all the laser's
| energy will go to speeding up the ship. (Well, the beam will get
| wider, but you could probably get thousands of bounces.)
|
| A funny twist on that idea just came to my mind: if you're flying
| past a black hole, having just one mirror on the spaceship is
| enough. Shine a laser from the ship toward the edge of the black
| hole just right, it will curve around and come back to your
| mirror, then reflect and come back again, and so on. Needs some
| tricky positioning of the mirror, but in principle it lets you
| "push" off the black hole without using rocketry.
| robotresearcher wrote:
| > and eventually all the laser's energy will go to speeding up
| the ship.
|
| Half to the ship, and half to the Earth in the other direction,
| right?
| cousin_it wrote:
| Oh. Of course you're right.
| [deleted]
| andyxor wrote:
| sounds a bit like Starshot project funded by Yuri Milner
| https://en.wikipedia.org/wiki/Breakthrough_Starshot
|
| "The Starshot concept capable of making the journey to the
| Alpha Centauri star system 4.37 light-years away. It envisions
| launching a "mothership" carrying about a thousand tiny
| spacecraft (on the scale of centimeters) to a high-altitude
| Earth orbit for deployment. A phased array of ground-based
| lasers would then focus a light beam on the crafts' sails to
| accelerate them one by one to the target speed. At a speed
| between 15% and 20% of the speed of light, it would take
| between twenty and thirty years to complete the journey, and
| approximately four years for a return message from the starship
| to Earth."
| cmrdporcupine wrote:
| how does it slow itself down for entry into the alpha
| centauri system? seems like it would just blow past it
| dvirsky wrote:
| It doesn't. It snaps some pics, sends them back and moves
| on.
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