Lasers may be able to propel spacecraft to Mars at a significant fraction of the speed of light

captaincranky

TechSpot Addict
One other point: the sail would have to be designed to work across a broad spectrum because as the ship's velocity increases, the light from the laser will be dopplered into longer wavelengths. At relativistic velocities, the energy from the laser would be greatly attenuated and would probably cease to be a very effective propulsive force. Just one more limit on the system's effectiveness, but I don't have numbers at hand, so can't put a value on those limits, especially when there are so many variables.
Well, I don't think we have the energy available to provide constant laser light to begin with. Since you suggest, "the acceleration would be slow", the laser would have to be constant, or at the very least have rapid recycle times. This physicist would have to do some really fast talking to get enough power diverted to pull this off.
As for Doppler effect, photography 101 tells us the light comes off a speculum in all directions, and can't be polarized. I believe our largest telescopes can be fitted with infrared sensors, so the wavelength of silvered mirrors must be fairly broad band. In the case of digital imaging sensors, most of those are filtered to get rid of infrared. So, long wave red isn't really that hard to trap or reflect. .

.AFAIK. lasers are bandwidth challenged to begin width. So, if we're thinking of a laser shooting imitation sunlight out into space, I think somebody's going to be deeply disappointed anyway.

However, I believe the power required to achieve "C", escalates to formidable levels the closer to moving at "C" a craft would become. So, there's that to consider. The farther away the craft gets, the more power would be required from the light source. Considering the greater the losses would be as the craft receded, supplying the motive force becomes quite an issue.

Then there's the mass required to be moved to Mars to establish a permanent base. We either can't afford or refuse to pay to continue our exploration of the moon. So, how extravagant would the price be for such an endeavor to Mars? Realistically, I think the best propulsive force would be the hot air coming out of Elon Musk's mouth.
 
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wiyosaya

TS Evangelist
I believe acceleration and deceleration are only an issue when considered against a force of gravity.
An object in motion tends to stay in motion; an object at rest tends to stay at rest - it is the "law" of inertia and applies whether or not the "object" is in a gravitational field. https://en.wikipedia.org/wiki/Inertia Therefore, any object would experience the effects of acceleration and deceleration regardless of whether it was in a gravitational field or not. With schemes like this, an acceleration of 1G would produce a gravity like effect for anyone inside the craft, and applied over sufficient periods of time, could allow a craft like this to reach the speeds they cite in the article. I'm not versed on the specific instance, so I do not know what their planned acceleration is.
 

Squid Surprise

TS Evangelist
An object in motion tends to stay in motion; an object at rest tends to stay at rest - it is the "law" of inertia and applies whether or not the "object" is in a gravitational field. https://en.wikipedia.org/wiki/Inertia Therefore, any object would experience the effects of acceleration and deceleration regardless of whether it was in a gravitational field or not. With schemes like this, an acceleration of 1G would produce a gravity like effect for anyone inside the craft, and applied over sufficient periods of time, could allow a craft like this to reach the speeds they cite in the article. I'm not versed on the specific instance, so I do not know what their planned acceleration is.
Speed is not the issue... it's speed/distance/time.... given enough time and space, and assuming the object we "hurl" won't break down (or disintegrate), we could get anything to a "significant fraction of the speed of light". But it might take 50 years (or more) and not happen until the object has traveled past Pluto....

The voyage to Mars is a fixed distance (although it varies depending on orbits), and if we can't get acceleration to get us there faster than a conventional propulsion system would...
 

captaincranky

TechSpot Addict
An object in motion tends to stay in motion; an object at rest tends to stay at rest - it is the "law" of inertia and applies whether or not the "object" is in a gravitational field. https://en.wikipedia.org/wiki/Inertia Therefore, any object would experience the effects of acceleration and deceleration regardless of whether it was in a gravitational field or not. With schemes like this, an acceleration of 1G would produce a gravity like effect for anyone inside the craft, and applied over sufficient periods of time, could allow a craft like this to reach the speeds they cite in the article. I'm not versed on the specific instance, so I do not know what their planned acceleration is.
Jeez, I made that misstatement quite awhile ago, :D just catching up with it now? Clifford called me on it right away! I do recall seeing how a space station could be made to have "gravity", through centrifugal force.

However, such artificially produced gravity, would cease as soon the the craft stopped accelerating, and the ship along with its occupants would return to a weightless state. (Not that it would matter).

Since, "a significant fraction of light speed", is a completely unusable constant in any equation, let alone one centered on determining the g-force derived from an unknown coefficient of acceleration, neither one of us needs to take calculus 6 to try and figure it out...

What is impressive, is someone trying give Musk's grandiose rhetoric a run for its money, so to speak.:cool:
 

captaincranky

TechSpot Addict
Speed is not the issue... it's speed/distance/time.... given enough time and space, and assuming the object we "hurl" won't break down (or disintegrate), we could get anything to a "significant fraction of the speed of light". But it might take 50 years (or more) and not happen until the object has traveled past Pluto....

The voyage to Mars is a fixed distance (although it varies depending on orbits), and if we can't get acceleration to get us there faster than a conventional propulsion system would...
Weren't you just telling someone, "don't say it can't be done"? Que paso?

Although, the premise of the article was, "a three day taxpayer paid expenses trip to Mars". Now we're going to Pluto?

(And yes, if you were wondering, I am trolling you, but in a good natured way).
 

Technician

TS Addict
Ohh and I do agree with the laser loosing strength, regardless of how concentrated the beam is. That is only part of my skepticism.
A laser is a coherent beam of light. So much for that part of your skepticism.
As for gee forces, that isn't a factor of speed, it is a factor of rates of acceleration and deceleration as well as centripetal force.
 

captaincranky

TechSpot Addict

luvantique

TS Rookie
Are you trying to tell me that since you know physics, this simply isn't possible?
Let's not be too arrogant here... Scientists have been coming up with stuff that VERY intelligent people have considered impossible all the time... There's always a chance that something like that could happen here...
Remember, Einstein stated that nothing could go faster than light, and we all thought, "yep, he's right"... Now scientists have particles going FTL...

Just goes to show - anything can happen... Start using your imagination instead of just assuming stuff can't be done... Maybe it can!
I assume nothing. Don't confuse Science with Science Fiction. What I'm saying is that there are fundamentals that cannot be violated. You can't change the basic significance of velocity, momentum, and gravity. Since Einstein we have a better idea of how gravity works, but the effects have been calculable since Newton, and none of that has changed. There's an awful lot of pseudo-science being tossed around on the imagined premise that "something could happen", but before you can make arguments like that, you must understand the basics, and what I see in many of the speculations here is a very thorough lack of understanding. New Theory must either completely displace the old, or be inclusive of it. Newton's view of the Universe worked for a very long time and his calculations are still valid for most applications. Einstein did not displace Newton; his new perspective was fully inclusive of Newton's insights, and gave us a better and deeper understanding of the principles involved and the reasons for them. But Einstein's view is also incomplete. The next Einstein will give us a more complete picture and an even deeper understanding.

As for faster-than-light particles: there's nothing new there. The tachyon has been a matter of speculation for decades, but to my knowledge there has never been any experimental evidence that it exists. The limits of Special Relativity are absolute: No object with mass can be accelerated to more than some fraction of the velocity of light because for every increases in velocity, there is an incremental increase in mass and consequent increase in the amount of energy required to achieve additional acceleration. At light speed its mass becomes infinite, which is to say it would require infinite energy to bring it to that velocity. Can't be done.

In the matter of speculation: I collect books written by "crackpots". Their writings are informative in that they seem all to fit into a surprisingly consistent pattern. One of my favorites is a book called "Atlantis and the Seven Stars". The author repeats over and over again (with consistent absurdity) that a thing surely must be because (in his view) it might be. Of such is pseudo-science. Be careful that you don't slip into that kind of thinking trap, because is leads nowhere.

Bottom line: imaginative speculation if fine, so long as you do it from the shoulders of those giants who have gone before (to paraphrase Newton).
 

Squid Surprise

TS Evangelist
In an article talking about lasers taking us to Mars, I believe pseudo-science rules the day.... And while Einstein built on Newton, who built on Galileo, etc, there are still phenomena that are unexplainable yet do happen... Like light behaving as a particle and wave for instance..

The people researching this in the first place are almost certainly a lot smarter than all of us - who are we to tell them that what they are trying is impossible?
 

captaincranky

TechSpot Addict
In an article talking about lasers taking us to Mars, I believe pseudo-science rules the day.... And while Einstein built on Newton, who built on Galileo, etc, there are still phenomena that are unexplainable yet do happen... Like light behaving as a particle and wave for instance..
Keppler never gets the credit he should.

The people researching this in the first place are almost certainly a lot smarter than all of us - who are we to tell them that what they are trying is impossible?
Perhaps they're simply too smart for our own good, or their own good, whoever's own good.

There was a TV special about the guys who perpetrated the Enron scandal. It was titled, "The Smartest Guys in the Room".
 
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captaincranky

TechSpot Addict
Hehehe... well, when they start asking me for money to fund this laser... that's when I start to get suspicious :)
Hm, lasers are electric powered, the government is out of the space business, stir in a corrupt utility company, and this is starting to stink decades in advance.....:eek:
 

luvantique

TS Rookie
A laser is a coherent beam of light. So much for that part of your skepticism.
As for gee forces, that isn't a factor of speed, it is a factor of rates of acceleration and deceleration as well as centripetal force.
This is true, but not quite true. No laser beam is perfectly coherent. All will spread with distance, so as the distance from laser to ship grows, there will be some attenuation of the thrust it generates specifically because of the spread. At very high velocities, there is also an attenuation of energy due to dopplering of the laser beam. If you start at home with a high energy laser in x-ray wavelengths, say, as the ship moves into higher velocities, the wavelength of the beam striking the sail gradually lengthens due to the Doppler effect, and the motive power of the beam decreases with the corresponding decrease in energy.
 

luvantique

TS Rookie
Remember, Einstein stated that nothing could go faster than light, and we all thought, "yep, he's right"... Now scientists have particles going FTL... QUOTE]

Ah, are you referring to the Cern Neutrino experiments? That result was eventually found to be an error in measurement. Einstein is back on his throne and all is well with the world.
 

captaincranky

TechSpot Addict
This is true, but not quite true. No laser beam is perfectly coherent. All will spread with distance, so as the distance from laser to ship grows, there will be some attenuation of the thrust it generates specifically because of the spread. At very high velocities, there is also an attenuation of energy due to dopplering of the laser beam. If you start at home with a high energy laser in x-ray wavelengths, say, as the ship moves into higher velocities, the wavelength of the beam striking the sail gradually lengthens due to the Doppler effect, and the motive power of the beam decreases with the corresponding decrease in energy.
And Roy G. Biv told me to tell you, "you won't be using a blue laser to push the damned thing".
 

luvantique

TS Rookie
In an article talking about lasers taking us to Mars, I believe pseudo-science rules the day.... And while Einstein built on Newton, who built on Galileo, etc, there are still phenomena that are unexplainable yet do happen... Like light behaving as a particle and wave for instance..

The people researching this in the first place are almost certainly a lot smarter than all of us - who are we to tell them that what they are trying is impossible?
Part of my point in that post was that there is a distinct difference between speculative science, which derives from extensions of the known and well understood science, and pseudo science, which derives from "wouldn't it be nice" without benefit of any real scientific foundation. Errors notwithstanding, this discussion is speculative, but not pseudo.
 

Squid Surprise

TS Evangelist
Part of my point in that post was that there is a distinct difference between speculative science, which derives from extensions of the known and well understood science, and pseudo science, which derives from "wouldn't it be nice" without benefit of any real scientific foundation. Errors notwithstanding, this discussion is speculative, but not pseudo.
Well, to be fair, the actual paper that this article is talking about was more involved with propelling small probes via laser.... it didn't really address slowing down nor was it really interested in Mars... It's real "thesis" was to say that it was technologically possible to start exploring the stars... the article here really kind of misses the point of the paper :)
 

hrowder

TS Enthusiast
While this whole subject is interesting from both a speculative and scientific point of view, I have some problems with the value of traveling to Mars other than the "cool factor". Mars, as others have pointed out, has no magnetic core, and therefore no surface protection from solar wind which is why surface water is gone. This lack of protection would result in a very problematic existence for any organic creatures who might want to be on the surface of the planet. I grant you that life beneath the surface might be more viable, but bringing large enough excavation equipment to Mars in order to make that possible is, again, a big problem. The same lack of a central core renders Mars unsuitable for "terraforming". Any attempts to bring plant life to the planet will fail not only because of the constant drying of any surface water resource, but also because of the distance from the sun which makes for a very frigid existence there. Creating "smog" in the thin atmosphere in order to thicken it and thus make it retain heat fails for the same reason, as the solar wind would blow it away faster than you could thicken it. The only way to make Mars a viable planet that could sustain life would be to bombard it with asteroids containing heavy metals for a few thousand years until it was completely molten to the core and of sufficient size so it had a gravity similar to Earth, and then bombard it some more with comets with high water content so as to bring enough water so it could flow at the surface now that the molten core could produce a magnetic field. All this activity might well result in a livable planet after is cooled again in a few hundred thousand to several million years, but at the same time render Earth a wasteland because of all the debris that would then go on to bombard Earth, to say nothing of the different gravitational effects a larger Mars might create in the inner solar system. So, yeah, finding interesting and possible solutions to near light speed travel is nice and all that, but I think we have to look farther afield for more suitable places to colonize... specifically in other solar systems which might have planets already possessing the prerequisites to sustain life. This makes near light speed travel or even pseudo faster than light travel via "warping" more necessary in the long run. So using this laser method to propel small probes to new solar systems might be a good idea (though still taking too much time resulting in multi-generational communication), but colonizing Mars seems like a loser at anything but a small scale for scientific or exploratory purposes. But hey... what do I know. I don't claim to be the smartest guy in the room. I'm just some guy.
 

captaincranky

TechSpot Addict
Well, to be fair, the actual paper that this article is talking about was more involved with propelling small probes via laser.... it didn't really address slowing down nor was it really interested in Mars... It's real "thesis" was to say that it was technologically possible to start exploring the stars... the article here really kind of misses the point of the paper :)
Here's a page on theoretical interstellar propulsion:
https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration

And here's where I think the sail and laser "solution" must fail: Einstein's Theory of General Relativity (explained). This article should have been titled, "Einstein for Dummies", as even I got it. http://www.phys.vt.edu/~jhs/faq/sr.html
 

captaincranky

TechSpot Addict
The only way to make Mars a viable planet that could sustain life would be to bombard it with asteroids containing heavy metals for a few thousand years until it was completely molten to the core and of sufficient size so it had a gravity similar to Earth, and then bombard it some more with comets with high water content so as to bring enough water so it could flow at the surface now that the molten core could produce a magnetic field. All this activity might well result in a livable planet after is cooled again in a few hundred thousand to several million years, but at the same time render .
Well, you could hurl all the buckshot and ball bearings you want at Mars, but that wouldn't make it a viable planet. Tack on another billion years to allow the of evolution of carbohydrate synthesizing organisms, then maybe it might sustain an apex predator like Homo Sapiens.

But then again, the sun represents a "point source" of illumination As such, the inverse cube law determines the intensity of light reaching any point in the solar system. The further away from the sun you go, rthe lower the foot candle reading will be. Our noon daylight, (IIRC), is 16,000 foot candles. @ 5600 degrees Kelvin. The sun's color temperature is affected least by atmospheric spectral absorption, when its light is at a 90 degree angle to the surface. So, the greatly reduced available light at Mars' surface, would make growing weed there pretty much out of the question. (Along with a whole host of annual summer food staple crops).
 
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