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Light Sail Propulsion Could Reach Sirius Sooner Than Alpha Centauri (arxiv.org)
RockDoctor writes: A recent proposition to launch probes to other star systems driven by lasers which remain in the Solar system has garnered considerable attention. But recently published work suggests that there are unexpected complexities to the system. One would think that the closest star systems would be the easiest to reach. But unless you are content with a fly-by examination of the star system, with much reduced science returns, you will need to decelerate the probe at the far end, without any infrastructure to assist with the braking. By combining both light-pressure braking and gravitational slingshots, a team of German, French and Chilean astronomers discover that the brightness of the destination star can significantly increase deceleration, and thus travel time (because higher flight velocities can be used). Slingshotting around a companion star to lengthen deceleration times can help shed flight velocity to allow capture into a stable orbit. The 4.37 light year distant binary stars Alpha Centauri A and B could be reached in 75 years from Earth. Covering the 0.24 light year distance to Proxima Centauri depends on arriving at the correct relative orientations of Alpha Centauri A and B in their mutual 80 year orbit for the sling shot to work. Without a companion star, Proxima Centauri can only absorb a final leg velocity of about 1280km/s, so that leg of the trip would take an additional 46 years. Using the same performance characteristics for the light sail, the corresponding duration for an approach to the Sirius system, almost twice as far away (8.58 lightyears), is a mere 68.9 years, making it (and it's white dwarf companion) possibly a more attractive target. Of course, none of this addresses the question of how to get any data from there to here. Or, indeed, how to manage a project that will last longer than a working lifetime. There are also issues of aiming -- the motion of the Alpha Centauri system isn't well-enough known at the moment to achieve the precise maneuvering needed without course corrections (and so, data transmission from there to here) en route.
(and it's white dwarf companion)
its
This is a Thought Experiment, not a real plan to go anywhere... we aren't going to travel between the stars until we figure out something a whole lot better than chemical rockets and probably FTL drive...
Everything else is just fantasy...
spirit of creation provides more than enough of everything we need with no personal gain motive... give until it stops hurting.. sing along... https://www.youtube.com/watch?v=v0nmHymgM7Y.. will wonders never cease?
Thats how it begins. a "Thought Experiment" that is. 70 years is a great amount of knew tech... we will likely have something in 40 years that will sail right past our sail ships.,,, hmmm
[($)]
Just reverse the laser into a tractor beam. Why do i have to think all the solutions myself?
I know tech and knew tech will revolutionize everything right know!!
That's why we never bothered to sail to the new world until we had 747's. Why bother when our 747's will just get there first.
will you still be alive in forty years' time?
a team of German, French and Chilean astronomers discover that the brightness of the destination star can significantly increase deceleration, and thus travel time
Sounds like they've discovered a way to significantly increase travel time.
Sigger than your average
We are lucky enough to live at the right time where we can say yes Im 45 now and in 40 years I may not look a day older than I do now.... stem cell research :)
[($)]
Getting a person there with something better than chemical rockets is just fantasy since if you got the vehicle to move fast enough even the cosmic background radiation will be shifted enough to irradiate people to death.
Of course, a different fantasy of cryosleep plus slow travel or FTL removes that in SF at least, but not so much in reality.
This thing on the other hand looks like a way to get a machine to another star using something that needs nothing more than some years of development (https://en.wikipedia.org/wiki/Solar_sail#Projects_operating_or_completed) instead of wishing so I do not get why you are calling it fantasy.
We've already "worked out" quantum entanglement enough to know that we can't "siwtch" an entangled particle's spin.
It's impossible to transmit information using entanglement.
systemd is Roko's Basilisk.
Would be happy to learn more about this.
What have we worked out about quantum entanglement that allows us to know transmitting information is impossible?
Light Sails work similar to wind sails on the seas.
If you run some numbers, you can see that 0.1c is possible - probably faster. That converts these "thought experiments" into real engineering.
Airplanes were a "thought experiment" too, BTW.
I don't think FTL travel is possible, but the science for light-sails **is** here already. Only the "will" to make it happen remains.
Lolwut?
My first program:
Hell Segmentation fault
https://en.wikipedia.org/wiki/...
Not faster than light, which is what this was about.
well are you?
Once we have the massive laser array for sending these things we can send one every week. It is not a one-off mission.
With current technology, that's all you'll be doing. Focus on Mars or Moon bases for now.
It's impossible to transmit information using entanglement.
Just to clear this up, parent meant it's not possible to communicate faster-than-light using entanglement.
A few years ago, I read an article about how in the timescales it would take Voyager type spacecraft to travel to Proxima Centauri, the stars will have moved relative to each other such that Sirius would actually be closer, so would make a better target. Now, with the technology able to at least theoretically reach a star within decades rather than 100s of millennia, it turns out Sirius is still the better target. It seems we are destined to choose Sirius as our first interstellar destination whatever the circumstances.
Difficult to take seriously (yeah I know it's interstellar travel but) when the first line has such a jarring spelling mistake: "assuming light-weight spacechips"
Why is light sail considered entirely possible, while EM-propulsion remains in the domain of evolution-denying (and even Trump-voting)? Aren't they both using light (of some frequency or another) as, uhm, tangible? Something, against which it is possible to push, however slightly?
In Soviet Washington the swamp drains you.
Just send one hopeful NEET to do some science.
Their reward?
Fame, glory, dying for science. But mostly being alone for the rest of their life to watch anime backlog and play every videogame of the generation.
I'd sign up for it if they gave me access to every form of media around, put a bunch of base resources for building shit and let me be. :^)
Although in saying that, I'll not even last half the mission.
Thanks, immune system. You had one job.
Talking about unrelated flaws of someone, who pointed out your mistake, reveals nothing other than your own acute need of Vaseline...
Correct the mistake if you can and, perhaps, even thank for pointing it out. Or just keep quiet and apply the ointment where it hurts (and you do know, where that is, don't you?)
In Soviet Washington the swamp drains you.
We're doing it all backwards. In order to avoid navigational errors we have to get the star to draw us towards it or vicey versy. In other words, use attractive forces instead of repulsive ones.
“He’s not deformed, he’s just drunk!”
..you can't be Sirius!
How about communicating over extremely long distances without using extra power or keeping a directional antenna perfectly aimed?
This is talking about Light Sails, not chemical rockets and FTL.
IIRC the one test we tried to do of a light sail didn't work very well. We seem to be pretty good about getting stuff into space at the moment, maybe we should try again. Kickstarter, anyone?
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
What if we were to send out a photon beam from a source half-way between Sirius and Earth. We can entangle photons of different frequencies such as X-rays and visible light. If the X-ray photon is absorbed somewhere, the visible light photon disappears. But if there is no intercept, the visible light photon remains. That would seem to suggest you could send two photons in opposite directions. If one is absorbed, then the other disappears. And since the source is halfway between the two destinations, information is transferred twice as fast as it normally would take.
https://phys.org/news/2014-08-...
Vintage computer adverts: http://www.vintageadbrowser.com/computers-and-software-ads
So when are we expecting Alpha Centauri to get there?
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
I find it hard to believe that something going that far is not going to collide with some other object. The idea is cool though, maybe we should use robots to see how well it goes?
The solution is a two sail solution. The sail will break into two sails on approaching the destination star. The big primary sail will act as a mirror and beam light backward unto the smaller secondary sail slowing down the probe.
The method from the article uses interference "Bringing together both paths of the red photons (from the first and the second crystal) creates bright and dark patterns, which form the exact image of the object". That doesn't happen in your setup.
That is exactly what I came to post. I thought that the idea was to send lots of them since the probes themselves are inexpensive.
And specially because otherwise having a high probe loss rate the project failure was assured.
Also if each probe whizzed the star system in ~1 week launching at the max attainable speed there is no need for extra braking at the destination as the next probe is just arriving to replace the previous one.
How about communicating over extremely long distances without using extra power or keeping a directional antenna perfectly aimed?
You need a classical signal to correlate the entangled pairs, meaning you'd have to send a beam of light/radio/neutrons/whatever to the other side so they can "decode" the entangled signal.
So you actually still need the same power and directional antenna. Plus some extra equipment to handle the entangled stuff.
Nope. You need a classical communication channel just the same. The quantum channel is only capable of communicating uncontrollable random garbage.
Quantum-encrypted communication is no more useful in space than on earth, in fact it gets more resource-intensive the longer the link distance. Because the entanglement state travels faster than light (somewhere between 10,000c and "instantaneously"), and the classical channel that actually carries information is at light speed, if you wanted a quantum-encrypted radio link in space, you'd have a store a loooong history of the stream of random noise from the entangled electron, so that when a bit arrives after travelling 40 light-years you can look up what your electron's spin state was 40 years ago to decrypt it.
"When information is power, privacy is freedom" - Jah-Wren Ryel
By not needing to bring the bulk of the fuel needed for interstellar transportation, and by efficiently utilizing em from nearby stars, it will be very hard to beat its speed for the foreseeable future. Even things like the em drive, if it's real (tldr extremely unlikely is being nice) require onboard fuel and would take far longer to make the same trip.
Ultimately the best setup possible to move through space in a normal fashion would be to create or mine a miniature black hole of roughly a billion metric tons, and utilize the Hawking radiation to convert mass to energy. The output would be a steady 350 Mw or so and the radius of the horizon would be roughly proton sized. One would need a confinement system similar to, but far more advanced than, particle accelerator beams used in research today. On paper you could even harvest mass along the way. Given the laws of physics, it is unlikely one could design a higher power thrust to weight of the drive system/craft over the long hauls of traditional interstellar travel.
Thought experiments are how you come up with an idea that nobody has thought of before.
Back in the late 1980sI was on an email discussion group for Traveller (a sci-fi RPG). Someone asked why hydrogen fuel (for fusion) was stored as water aboard ships. Someone answered that water stores hydrogen atoms more densely than hydrogen gas, and the energy needed to chemically break off the hydrogen atoms off of water was trivial compared to the energy you could get from fusing them into helium. That spawned a discussion about whether there were other molecules which stored hydrogen even more compactly. Methane (CH4) was an obvious choice - 4 hydrogen atoms per non-hydrogen base, compared to just 2 for water (H2O). But eventually we settled on ammonia (NH4) because it's liquid at room temperature and wouldn't require pressurization or cryogenic storage in a vehicle sharing space with a life support environment for humans.
It's totally useless info right now (and probably the next few decades). But it's something that will be important in the future.
The cover article in the March 2017 issue of Scientific American was about using multiple light sails and miniature sensors to visit Alpha Centauri, with a large array of lasers -- either earth-based or space-based -- as the primary accelerant. The use of light sails, however, can be problematical.
First of all, consider solar wind, the stream of gases and particles emitted by the sun. If solar wind is faster than the sails, it will accelerate them beyond the force of the proposed laser array. If the solar wind is slower than the sails, however, the sails will decelerate. In either case, the solar wind and the sun's gravity can alter the trajectory of the sails.
The Oort cloud also requires consideration. If the sails are not punctured by the particles in the Oort cloud, impacts of those particles on the sails will decelerate them. If the sails are punctured, they will become useless in decelerating the sensors when the target star is approached.
Then there is the fact that space is not a perfect vacuum. Without dark matter, space still contains gas and dust, which can decelerate the sails. If dark matter does indeed pervade space, the deceleration might be sufficient to prevent the sails and their sensors from ever reaching their target stars.
This does not make the concept of light sails impossible. Before such a project is launched, however, more knowledge is needed about the solar wind, the Oort cloud, and what exists in space between here and any target star.
Yeah. If we spent billions a year on serious research for life expansion.....
If the X-ray photon is absorbed somewhere, the visible light photon disappears.
That's not what happens. It would violate conservation of momentum, for a start.
systemd is Roko's Basilisk.
Well, not quite. You're constrained by the efficiency of your reflector, the maximum temperature your (electronics, mirror coatings, sail, shrouds, whatever is the most temperature-sensitive component of your actual vehicle design) can stand, and your launch laser. So you fire the laser until the probe has the velocity you can dispose of at the destination (which is what this paper is about), then leave it to fly. Re-point laser and launch again. You might not get one launched a week, but several a year is probably feasible. By the time they're flying past Eris, they're probably at cruising speed already.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
While I didn't work on this one, the Galileo mission was started at JPL in 1977 (there were lots of study work done before that) and was ended in 2003 with the planned plunge into the Jovian atmosphere. That's 26 years, which was at least for many of the engineers, scientists, technicians and managers on the project a good portion of their careers. 74 years or more (added 5 years for planning and implementation) isn't bad for an interstellar robot mission. The challenge is always the stability of the funding environment.
Thats how it begins. a "Thought Experiment" that is. 70 years is a great amount of knew tech... we will likely have something in 40 years that will sail right past our sail ships.,,, hmmm
So build that in the design.. and you shorten the time to get to the destination.. Start off with a light sail and build it with a tractor beam hook so your Constitution class starship can tractor it up into it's cargo bay and there you have.. a 70 year minus 10 year = 60 year trip to Proxima Centauri. Still will not work while we still have Republicans, because Republicans are why we cannot have nice things!
YHBT. HAND!
how to manage a project that will last longer than a working lifetime
This is not a problem we cannot solve: Most engineers that witnessed Voyager 1 launch in 1977 are likely to be retired now. We still collect information from the probe, thank to younger engineers that joined after launch.
And with a fleet in flight, if you are lucky the later-launched craft can serve as relay stations to correct and retransmit the signals for a power increase. Successor craft can also benefit from improved comm technology.
stage is that we are still on the part of the technology curve where it's still better to wait because the craft we can send tomorrow will get there before the one we can send today. At some point, the improvement becomes moot, and we can then discuss the costs and reasons to pay them now instead of later.
Because transmitting information faster than light breaks a fundamental law of physics.
You don't need to keep it "perfectly aimed." In fact, the farther you go the easier it is to aim because the beam gets wider with distance.
Assuming you could include on the spacecraft the necessary detection equipment to figure out where the relevant stars are, you could have it compute its own course corrections, right?
Is the point to just get to another solar system?
Or, get to a close one with the highest probability of life?
In any case, it seems that even unmanned probes are a waste of time until faster communication (Quantum Communication?) is developed.
A manned mission seems the best option if we must be going soonest.
Then, while that mission is in route, we will have (likely) developed faster technology and can pick them up on a subsequent mission.
(Yeah yeah yeah. I know. Greater challenges with generations in space travel, etc, etc, etc... Just sayin'...)
Self-importance and self-indulgence is the root of ALL evil.
How can you communicate information using entanglement at all? Entanglement is something like putting a red and a black card into separate envelopes. If you open your envelope and find a red card, you know the other guy has a black one, but that's not communication. It's a lot more complicated, actually, but what it will tell you is probabilities that the other guy will get certain results given certain experimental setups. The only way to make it communicate would be to be able to alter a property without breaking entanglement, and that doesn't work.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
https://en.wikipedia.org/wiki/...
That isn't communication by entanglement. That's making existing communication tamper-evident using entanglement. Information flows in the normal way, but uses quantum properties to ensure that nobody can resend a photon accurately once read. If Eve is trying to listen in on the key transmission from Alice to Bob, Bob will get a garbled key.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes