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Sorry, But Lasers Aren't Taking You To Mars Anytime Soon
An anonymous reader writes: It's long been a dream of humanity to travel interplanetary distances at great speeds, or to make it to another star system within a human lifetime. Until recently, technologies to get us there — antimatter propulsion, wormholes or warp drive — have all been composed of physically unrealistic solutions. But recent developments in laser technology make directed energy propulsion a feasible solution. By building a giant laser array in space and developing a new type of solar sail that reflects the laser light with incredible efficiency, a laser sail, this propulsion system is scalable to arbitrarily large powers. There are many technical obstacles to be overcome, and so it's unlikely we'll see the fruit of this anytime in the next few decades (despite the promises of some), but this may well be the technology that takes us to the stars in the coming centuries.
Lasers would get me to Mars faster than I would click on a Forbes link.
Seven puppies were harmed during the making of this post.
Another Ethan Siegel blogspam that will take you to Forbes which HAS BEEN KNOWN TO deliver malware via their adserver. Do not follow the Forbes link!
"Scalable to arbitrarily large powers" = "I haven't thought about this very hard"
Slowing down isn't the problem. Slowing down and staying in one piece is the tricky bit. Just ask the Mars Climate Orbiter team.
Nuclear is still the best way to get to Mars. If it weren't for the fact that the words "nuclear rocket" in the same sentence is somehow horrifying, we would have been there a while ago. I mean, it isn't even going to be on Earth people. If you really want we can even have it dock with the ISS so we just have to carry it up.
If interested in this potential star-reaching tech, read Robert L. Forward's book Rocheworld.
Non-Linux Penguins ?
"...how would you slow down when you get there? "
Radio ahead to make a deal with the locals to build a similar laser for when you arrive.
when doing something new, should we begin with an untested unknown technology, or with existing technology modified to meet the need ?
imo the second method. and in this case, choosing that way would probably get us to mars in decade or three, but choosing first will only delay it ever further (though it would allow us to paint and write cool impotent pictures to pass the time).
and we are not doing a new potential technology a service by saddling it with solving complex task start with.
XKCD covered this and came to the conclusion that laser propulsion just isn't practical, even by the lofty standards of theoretical intrastellar space travel.
I read the internet for the articles.
Light sails don't work just one-way. Wind-based sailors have known for millennia how to tack into the wind; the same basic idea works for light.
Tacking works because of the reaction of the keel on the sea water. Unfortunately, there is no sea water in space.
The biggest technical hurdle to human spaceflight is enabling them to survive the experience. Robots are far more likely, I think, for the next few centuries at least. Of course, some new disruptive technology could change that picture.
This posting is provided 'AS IS' without warranty of any kind, implied or otherwise.
Unfortunately you are traveling faster than escape velocity. Therefore you CANNOT "enter orbit". The planet will only deflect your path. The laser idea is just that an idea. Interesting but totally impractical and unworkable. Better to put a liquid salt thorium nuclear reactor and ion drives onboard the space craft. Or use an EM massless drive if it turns out to be real and not an experimental error. The light weight thorium reactor could use both ion drive for long haul low acceleration to conserve reaction mass and for a burst of high acceleration you could use the thermal output of the reactor to heat reaction mass and expel it directly. Interesting idea for a hybrid nuclear rocket system.
By building a giant laser array in space BLAH BLAH BLAH unlikely we'll see the fruit of this anytime in the next few decades
You had me at giant laser array 3
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do you even Kerbal?
you know how much of a pita gradual atmospheric breaking would be on mars too? you don't have to worry about your components melting... but you've also barely got an atmosphere to work with.
don't think a parachute would do much unless it were impractically large either.
Sailing into the wind relies on the keel to resist any sideways motion of the hull so that the only component of force remaining is one which points into the wind. You cannot do that in space. The only way I can think to do anything close to that in space is to use a gravitational field which will be very different to wind-based sailing.
For example no tacking is required: if you want to move closer to the sun use your solar sail to slow your orbital velocity and then just retract the sails and fall. However if you are powered by a laser bank then getting bank to Earth will be a lot trickier since there is no gravitational field to pull you in at inter-planetary distances. You will likely need good timing and rely heavily on complex orbital maneuvers in which case it is hard to see how it is better than a rocket.
If we are talking about sending very small micro satellite or slightly larger sized probes, then who cares about slowing down? You can get good data without slowing down.
I think that disposable probes is where you start. Sending small probes (anywhere) for a few million each to get you to a proof of concept.
Just play with them in Earth orbit to start.
"Lasers might take you to Mars some day."
Sure, they might take you there, but you'll only be passing by , because unless someone has built another laser array ON mars you won't be stopping until you hit something. Which could be the same day or a billion years later as the dried out dust that used to be your corpse slowly orbits the galaxy.
Or use an EM massless drive if it turns out to be real and not an experimental error.
It is absolutely not real.
SJW n. One who posts facts.
The faster your trajectory, the closer you need to get to the mass that you're slingshotting (not orbiting) around. If you want a solar sail to survive, then you want to make sure that this radius is outside of the radius of the outer atmosphere. If you want the spacecraft to survive, then you need to make sure that this radius is outside of the planet's crust. Otherwise, you'll just end up with a smallish deflection and go off in a totally useless direction.
I am TheRaven on Soylent News
You reverse the polarity of the neutron flow.
Shit. Are you sure it's not a tachyon pulse?
I can't judge if laser propulsion will become workable but external propulsion (as opposed to onboard) certainly makes sense. That is, between two of 'our own' locations, with a 'cannon' on both ends.
So you would need a stage of slow ships taking ages to reach the target and brake. Then they build the 'braking laser' and then you can get much faster traffic.
So we have multiple experiments showing it is, but you're not linking to what debunks it.
No we don't, we have several experiments which show that there is no effect larger than the current experimental errors.
Why?
Seriously? Would you expect me to provide a link if I claimed timecube is bunk? Anyway, start here:
Noether's Theorem.
SJW n. One who posts facts.
... Better to put a liquid salt thorium nuclear reactor ... The light weight thorium reactor...
There seems to have developed a nerd cult of the "liquid salt thorium nuclear reactor" which is apparently endowed now with quasi-magical powers, the answer to all possible questions about power sources. The proposed "liquid salt thorium nuclear reactor concept, none of which has every been built, is an idea for large scale fixed power plant designs, and is a very complex system as conceived (involving circulating molten salt fuel, on-line fission product removal systems from the fuel, etc.) that only makes sense - if it is practical at all - as part of a world-wide nuclear power industry. It has absolutely no features of value for a space travel power source.
The notion that such a system could ever be "light weight" is ridiculous - tacking those words on to "thorium reactor" does not make it any sense.
Any real space-flight ready reactor use ceramic highly enriched uranium fuel (negligible hazard until the reactor core turns on for the first time in space), fast neutron operation (moderator is heavy), and as few moving parts as possible. Something more like this.
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj
Seriously? Would you expect me to provide a link if I claimed timecube is bunk?
Actually, yes.
Disclaimer: I'm not the OP or GP or OG or anything like that.
I would expect it because Slashdot is a mixed crowd and some people (GASP!) actually read comments to get a better understanding of what's at hand. You, as a random Slashdotter, have no real standing with me. Not that I dislike you but I don't know you from Adam. You could be making up whatever you talking about or, worse, repeating something from someone else who also is just as clueless but now you've got an idea in your head that you're passing on as facts to others.
Telling someone their wrong in what could be a forward thinking forum would also carry the obligation of explaining why they would be wrong. Any jerk can make flippant remarks and be smug about it but it takes real knowledge to put something out there that will point the way to a better understanding for all involved.
I don't know why people around here think it's such a burden to discuss ideas with one another but is somehow acceptable to bad mouth others on matters that have very defined truths about them.
Time dilation is insignificant at 5% of light speed. It's about 1/10 of 1%.
It is unlikely to be real but your claim that the error level is higher than the measured effect is AFAIK wrong. We also have replication in 3 separate places with separate groups of people using different hardware which reduces some error sources.
No, sorry, but I will challenge that last statement. There are three separate groups which have produced different results which are inconsistent with each other.
Most recently, the NASA Johnson "Eagleworks" group has tried to replicate both the EM drive proposed by Shawer and a result on a similar concept in China claimed by Yang-- and falsified both of these results. The EM drive proposal stated that the purported drive worked because of a specific asymmetry, but the Eagleworks test showed that the result was the same whether or not the asymmetry is present: the Shawer driver does not work as proposed. They also tested the Yang result, and got a result... but the result was orders of magnitude different than the claimed Yang result. The net answer is that neither result was replicated.
Also, the test that was reported at a conference was not done in vacuum (although they only mentioned this detail in the "further work" section of their paper.) There has been a post to an internet forum saying that they have now tested it in vacuum, and gotten yet different results-- but internet forums are not scientific publications.
I'm in favor of good experimental work testing these ideas... but so far, it's way premature to suggest that the results have been replicated. They're not. The results are very, very small, and no two experiments seem to show the same thing.
Here's a Wired article from last year (which was the last anybody heard anything new) with some more discussion. (Sorry it's in Wired, which apparently everybody hates now, but that's where it is.) http://www.wired.com/2015/05/n...
http://www.geoffreylandis.com
The truth of mathematics is NOT the truth of reality, so don't try proving the contrary. Mathematics is extremely useful in modeling reality, and, significantly in this case, providing a handy way to come up with consequences of a theory. If we can't get consequences out of a theory, we can't do science, because we can't perform experiments and/or observations to distinguish one theory from another.
2+2 == 4 not because of some fundamental principle of the Universe, but because that's how we've defined integers. You can find lots of physical cases where you take two X, add another two X, and don't get four X. Suppose you have two droplets of water on a rubber sheet. Drop another two droplets onto the sheet. You can get quite a few different numbers of droplets on the sheet that way, depending on where you drop the water and what happens next. Perhaps they combine with the previous two and form one large droplet. Perhaps they splash on impact and we've got dozens. We don't have a law of conservation of droplets. We do have a law of conservation of mass that works in Newtonian physics, since we've observed that.
Noether's theorem is correct. The Law of Conservation of Momentum does depend on physical laws being invariant throughout space. (Actually, the laws get more complicated when we need to consider relativity, but the basic principles are the same.) It doesn't claim that physical laws don't vary between points in space, and it doesn't claim momentum is conserved, but it does show that the two are related. If momentum is not conserved, then we have to have changes in physical laws from place to place, and that would have consequences that we would almost certainly have observed.
I'm not saying the drive doesn't work. I'm saying that it's going to take a whole lot of evidence to convince people, and I haven't seen a whole lot of evidence.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes