I’ll believe it’s “technically feasible” when it’s more than words. Words don’t prove the physical.
“The technology isn’t just theoretical. In 2010, the Japanese Aerospace Exploration Agency (JAXA) launched a craft called IKAROS—the first successful interplanetary probe to use light sailing as a means of propulsion.”
“The Planetary Society also launched a light sail back in June 2015, and the institution is working on a new sail, the LightSail 2, slated for launch later this year.”
Solar sails are not a relativistic-speed drive; and trying to boost them to such with lasers at a range of totally unprecedented magnitude of range (just how coherent is that laser beam a few light days away?) is, as I said, just words. And FTL is nothing more than the most rudimentary of theory, if that.
The sails are apart of the architecture for Project Starshot; same to the NASA proposal.
They already demonstrate relativistic speed from this kind of propulsion in laboratory environments; next step is to prove it can be done in space itself. The man leading the NASA effort thinks we can basically pull tech off the shelf to propel 100 kg cargo to Mars in a few days, using the same amount of (chemical) energy a rocket today uses to get the same payload into LEO.
Why would it still need to be in contact with the laser by that point? It would have been “boosted” long before leaving the solar system.
“Demonstrated,” but not in space? How do you “demonstrate” in the atmosphere where aerodynamic and thermal issues would destroy the thing before you got out of single-digit mach numbers, let alone relativistic speeds? Computer simulation isn’t “demonstrating.”
And just how massive would the sail have to be to handle that rate of thrust (to achieve relativistic speeds in only a few hundred million miles (assuming the laser coherence is good for that range)), and what would that do to the thrust-to-weight ratio and the ability to achieve that acceleration? And how is that sail not going to be ripped to shreds at hundreds of thousands of miles per hour when encountering the odd space debris (pebbles, rocks), let alone at the hundreds of millions of miles per hour of relativistic velocities? For that matter, how is any craft going to withstand impact at those speeds, since we don’t even have the beginnings of the magnitude of technology to prevent said impacts?
Vacuum chambers. Putting an EM drive in one is how they found out it doesn’t work. Didn’t need to go to space.
Turns out the best way to handle this issue, and to make sure the probe isn’t damaged by the laser itself, is to put the sails in the shape of a sphere.
The sail would be folded up into a “cruise” configuration while on the way to alpha centauri to minimize the damage.
On the starchip itself, a protective coating of beryllium copper would be added. The microsdebris they’re most likely to encounter will be 0.1mm in width or less. Travelling at 20% light speed, they would penetrate the StarChip only 0.4mm.
I seriously question how realistic lab testing for this can be. We’re talking about several orders of magnitude more mass that has to be moved. Blowing a microscopic toy (and it couldn’t be more; otherwise, the kinetic energy would be highly destructive) around in a lab chamber is no representation of the real problems.
And that somehow reduces the mass from ridiculously too much? Not buying. And maintaining coherence of the laser beam is still an issue, to say nothing of the unprecedented magnitude of size of the laser (and the size of the problems that go with it).
First of all, 0.2 c is hardly relativistic velocity, and who the crap decided (and on what basis) what size of debris they’re likely to encounter in interstellar space? We haven’t tested even a tenth of a percent of the distance, and nowhere near that much of the volume (since a starship would require a LOT of volume for everything necessary to sustain and maintain the physical and emotional health of the crew, and would thus sweep a lot of volume on any interstellar flight).
Oh, and by the way: How do you STOP this allegedly viable concept at the END of the journey? Last I heard, we hadn’t contacted any life at Proxima Centauri, so I don’t think we could count on them to build an equally colossal laser to decelerate the thing…
“Proposals using large light sails like the Starshot Breakthrough, require mirrors with lateral sizes of 4 × 4 m2
, thicknesses of 0.05λ, reflectivities of 90 %, ppmlevel optical absorption and a total mass of only 1 g .
Our PhC are designed with a lattice of holes which remove about 30 % of the mass of the membrane. Additionally, they are made of LPCVD SiN which has an imaginary refractive index of about 10−6 at 1064 nm and has been shown to withstand high laser powers of around 2.5 · 1011 W/m2  – nearly 2 orders of magnitude more than what is required for the initiative.”
If it’s gradual enough, the change in momentum can be overcome. While the laser will have contact with the probe for only about 10 minutes, to my understanding, it would take the better part of a month before the probe reached its intended speed.
The craft is very small, the payload is a few grams, and the sail just a few meters across. We’re not talking about a manned mission (yet).
Over a journey of 20 years, you’d lose several months worth of time.
Because we’re talking about a space between two (relatively) close solar systems; photonic activity would have pushed much of the interstellar dust aside, and even scooped up in their gravity wells.
As to how we tested the interstellar medium for its density, you can find the methods for different sample areas of space listed here:
They won’t; the probe will be between 1-2 AU away from the planet as it takes its images.
Theoretically you could, through Momentum Breaking, or through deploying the sails to absorb momentum coming from photons off the suns of Alpha/Proxima centauri, but that doesn’t seem to be part of the plan. The former would require magnetic sails, and the latter would considerably slow the timeframe of the mission, not to mention present some risk of pushing the craft off course.
None of which addresses the mass of the ship itself, which must be HUGE for colonization.
If it’s gradual enough, you run into that problem of how much range you have in the coherence of the laser beam.
Actually, you were, which is what I was arguing against the likelihood of:
Okay, allow me to clarify: When I say relativistic speeds, I mean speeds with significant time dialation; as in, subjective ship time of less than half of Earth time. Good grief; if you want to get technical, any speed above absolute zero (say, a snail’s pace) is relativistic. But I’d like to stick with a more practical definition for the purpose of this debate.
They don’t know what clearing has allegedly taken place in interstellar space (they don’t even know much about the Oort cloud), and gravitational clearing is primarily going to be in proximity to the stars themselves- except when it isn’t cleared (they’re still mapping lots of just the BIG objects that would smash any spaceship; or battleship). And photonic clearance wouldn’t work worth a hoot on pebble-sized objects. And small probes traveling less than a tenth of a percent of the distance are not going to give us a realistic idea of the frequency of those pebble-sized (or larger) objects in the other 99.9% of the distance.
Which doesn’t help colonization and terraforming.
This topic doesn’t make any sense. I don’t see how you can have an economic discussion on something like the profitability of services or resources when the subject country is operationally socialist. Reason no longer applies when the gov’t is involved, however history proves socialism will eventually fail.
Dude, that should go on mugs and tee shits and such
? We moved to discussing the merits of Project Starshot, as Project Starshot, was my answer to whether we had a proven concept for a relativistic-speed space drive.
No where did I claim Project Starshot was a manned mission. Any article you read about it would tell you that it’s a probe.
I don’t even get what you’re fighting over here; perceivable time is lost, and we’re moving at a speed comparable to the speed of light.
If you want to cite an actual definition:
“Relativistic speed refers to speed at which relativistic effects become significant to the desired accuracy of measurement of the phenomenon being observed.”
So no, not just any speed counts under this definition, but 0.2c would.
People on the project call this relativistic speed. They even call the sails Relativistic Light Sails.
I don’t get why you or I should underplay this; having craft move at that speed would be a serious game changer for us.
It would mean we could get to Mars in just 3 days. Even if all you’re doing is sending the cargo, and not the humans, who go there on a slower rocket, it’d make colonization explode.
We have ways of detecting how dense the collection of matter is in a given region of space.
You can’t detect a single particle, but you can detect a cloud of such particles, and particles, tend to travel together.
We’ve used photonic momentum to stabilize the orbit of Kepler. Which is alot bigger than a pebble. Micro amounts of momentum is still momentum, when there’s no friction or collisions to tell the object to move in a different direction.
That’s not how we tested this:
? This seems intentionally short-sighted.
Clearly, having a probe demonstrate it can reach another star system, puts human travel on the table, just as we know probes traveling to Mars means we can move humans there. The difference is engineering, not science saying we can’t do it. And it’s the latter you were purporting here.
Once we have the drive, and a way to deflect or absorb stellar debris (we’ve been developing Force Fields for Iraq & Afghanistan for some time now), what exactly is stopping us, other than a need to scale things up?
No; you moved the discussion to this after I responded to your comment about inhabiting/terraforming a planet in orbit around Proxima Centauri, which an unmanned ballistic probe cannot begin to do, and whose largely theoretical concept doesn’t lend itself to that. You moved the goalposts from colonization/terraforming to sending a probe by that can’t help but fly on past and keep going (assuming they make the concept work at all; there’s a world of difference between theory and sterile lab experiments on one hand, and practical application on the other).
I explained clearly what I was on about. The time dialation at 0.2_c_ is of almost no pratical benefit.
And since you brought up the subject of getting to Mars in three days at 0.2_c_ (average), perhaps you can explain how a human being could sustain the constant (if it weren’t, the peak G-force would have to be higher) nearly 100G acceleration and deceleration that would be required…
Uncertain at best, particularly with larger objects.
At what range to the sun? Certainly not in interstellar space, where the effect would be less than that of a penlight.
Clearly, having a hypothetical design for an unmanned probe that cannot stop at its destination is a far cry from actually being in the development stage of a MUCH LARGER and workable crew-carrying starship that can. Which it cannot do with the technology (however well it works in reality) you described.
You tried to invalidate the topic by saying we didn’t even have a practical plan for an interstellar drive. You lowered the bar to that.
I offered Project Starshot as evidence of yes, we do in fact have one on the table. Science says this is possible. And then I went into detail for how it worked.
The creation of a practical drive became the topic, as a subtopic to interstellar travel.
I wasn’t leveraging time dilation as the benefit; only the speed.
I already qualified that:
“Even if all you’re doing is sending the cargo, and not the humans, who go there on a slower rocket,”
An evolved version of Robert Zubrin’s Mars Direct plan, where we send the cargo first? And can respond with supplies in a matter of days if something happens to the colonists? Hell yeah, I’ll take that.
It means we know the rate of how often particles will be encountered. We don’t need to know where the particles are, only how often they’d most likely be encountered.
In empty space, with nothing else acting on them, & Billions of years to push on them? Billions more than what we had for Kepler?
It’s going to be less dense, that’s pretty self-evident.
It’s far more than what you claimed we had, and it’s a incremental step.
It means once again, science isn’t the obstacle here, engineering & scale is. Which means we can predict, just like with Nuclear Fusion, when not if, this technology will be coming about.
What has ANY of this to do with Tesla’s batteries???
Batteries=Tesla=Musk=space program=FTL travel.
Come on, keep up…
One of my very favorite novels is Encounter with Tiber by Buzz Aldrin. It’s a novel with space aliens, but it’s hard science fiction in that it covers a wide range of proposed practical technologies for interstellar space travel with enough detail to explain it without becoming too technical. It also covers a range of political problems that might ensue. Yet it has a non-obvious plot. Fascinating.
But there were no Tesla batteries mentioned in it.
Our electric co-op is “pushing” electric cars. Hmm, that might be just the right word.
When the greenies succeed in phasing out the internal combustion engine, I suspect LOTS of people will be “pushing their cars.”
We don’t. When nothing of the sort has been tested in any meaningful way (actual operational conditions), it isn’t a practical plan. Science does NOT say this is possible, as science requires OBSERVATION, and not under such lamely undemanding conditions.
My impression was that you were trying to lawyer-talk the speed with the use of “relativistic.” And I clarified my use of the word “relativistic”, even if it wasn’t textbook. My point is that manned interstellar travel is, at best, uncertain.
I’ll concede that I missed that.
It means nothing of the sort, since we don’t know not only how frequently the particles are encounter, nor the size. That can only be speculation, not observation.
Again, assuming space is empty.
No it isn’t, because we don’t have it; just some lab studies and no actual space hardware to test.
And they’ve been predicting controllable nuclear fusion for decades. It might happen, but to say catagorically that it will is not scientifically sound. One can’t know that anything will happen unless God says so; man has been disappointed on far less speculative predictions.