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A Roadmap to Interstellar Flight (2016)
- cousin_it 5y agoOne 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 5y ago> 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 5y agoOh. Of course you're right.
- deleted 5y ago[deleted]
- andyxor 5y agosounds a bit like Starshot project funded by Yuri Milner https://en.wikipedia.org/wiki/Breakthrough_Starshot 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 5y agohow does it slow itself down for entry into the alpha centauri system? seems like it would just blow past it
- dvirsky 5y agoIt doesn't. It snaps some pics, sends them back and moves on.
- codethief 5y agoActually, the Wikipedia page for the project notes in one of the subsections: > The travel times are for the spacecraft to travel to the star and then enter orbit around the star (using photon pressure in maneuvers similar to aerobraking). Not sure how trustworthy that information is but this kind of "aerobraking" at least seems possible in principle.
- Johnny555 5y agoIf 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.
- nerpderp82 5y agoIf 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 5y agoCivilization is a believed concept. Physically taking all of your people with you does not equate to maintaining civilization.
- ryandrake 5y agoThis 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 https://en.wikipedia.org/wiki/The_Songs_of_Distant_Earth
- rbanffy 5y agoIt’s an excellent book. Mike Oldfield made an excellent soundtrack for it, and Clarke wrote the insert for the disk.
- nerpderp82 5y agoHumanity will diverge as soon as we have off Earth reproduction.
- ziotom78 5y agoThe 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 5y agoPeople 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.
- ziotom78 5y agoYes, being a high-speed particle particle you should use relativistic momentum to describe the hit, but the idea is the same.
- jtsiskin 5y agoSend a few thousand ships to clear the way and find the safest path first?
- ziotom78 5y agoUnfortunately there is no safest path. In free space, like in my home, dust is everywhere.
- nradov 5y agoThe usual sci-fi novel approach is to construct a thick ice shield on the bow of the ship. Not sure if that would really work.
- nerpderp82 5y agoI 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 5y agoA 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 5y agoAny fractional-c attack will be either impossible to detect, or impossible to prevent....
- JoeDaDude 5y agoA 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 https://breakthroughinitiatives.org/initiative/3
- JoeDaDude 5y agoLet 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.
- davedx 5y agoLittle toy tool I made to sim out various known propulsion systems for a crewed interstellar mission: https://redskyforge.com/interstellar/ https://redskyforge.com/interstellar/ Only nuclear is really interesting. Chemical rockets are useless at this scale.
- Robotbeat 5y agoBeamed 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 5y agoBut how do you stop?
- Robotbeat 5y agoBraking 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 5y agoI 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 5y agoElectrosails aren’t as good for this as magnetosails; I just included electrosails for completeness.
- cecilpl 5y agoTo 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 5y agoInterstellar 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 5y agoI'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).
- Robotbeat 5y agoDisagree. 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.)
- lmilcin 5y agoI 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.
- narrator 5y agoThe benefits on earth would be pretty significant too. Any drone swarm sophisticated enough to do this, given inputs it could custom order, could set up productive farming on any reasonable plot of land on earth with a few exceptions (e.g glaciers).
- cletus 5y agoWow, 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 https://www.youtube.com/watch?v=wXiitWK_6Qg [2]: https://www.youtube.com/watch?v=s6BQSgidbmc&t=1526s https://www.youtube.com/watch?v=s6BQSgidbmc&t=1526s
- deleted 5y ago[deleted]
- EricE 5y agoThe exoplanet mission from Civilization 6 in real life - what a fascinating read!
- paparush 5y agoobiligatory https://www.intelligentliving.co/amp/speed-light-slow/ https://www.intelligentliving.co/amp/speed-light-slow/
- jcurbo 5y agoRelated: https://hub.jhu.edu/magazine/2021/spring/apl-interstellar-probe/ https://hub.jhu.edu/magazine/2021/spring/apl-interstellar-pr... (Disclaimer, I work at APL, but not on this)
- m34 5y agoPropulsion 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 5y agoGetting 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.
- andyxor 5y agoUnless 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-propulsion-could-help-get-humans-to-mars-faster https://www.nasa.gov/directorates/spacetech/nuclear-propulsi...
- ncmncm 5y agoThermal 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.