Interstellar Travel

[GDJ]

The Technology exists...Orion

But:

1. No Money

2. No Interrest

3. Fear

4. Political structure is too immature and self centred for forward thinking beyond 5 years on average.

[PB666]

That 0.25 is Isp. And as such it is probably correct. Isp does not care about your mass, payload or whatever. So no, it is very realistic (and probably simply factual). Now it is another question if it allows us to reach 0.25c, but K^2 didn't say that; he only claimed 0.2c at 4:1 ratio (which by the way is again just a calculation and has nothing to do with future tech). Read up what he claimed and what Isp has to do with this; you said nothing that contradicts what he wrote.

If you would go for a 16:1 ratio, you could go for ~0.4c (ignoring relativistic effects for simplicity). Therefore more than 0.2c is not fantasy. But maybe not worth it.

Humans needing space/shielding/food is also no concern. There is enough space out there, and enclosing (or shielding) something scales slower than volume (until you reach some other problems, but we probably won't). Food and other goods (each being a miniscule part of the total mass) can either be recycled or be used for the M/AM reaction; so no waste there.

ISP does care about the nozzle, and if the nozzle is degrading because its a soft material in which the lead can undervaporization due to the demands of acceleration. In other words you are basically arguing that it is possible to reach 0.4c with M/AM device when you ignore the weight of lead (one of the most dense materials known to man) and the containment devices, and the AM/M injection devices.

Lets put it like this, the lead absorbs high energy gamma, that therefore results in heat and the occasional particle production. The higher the g-forces needed, the more heat 1-g worth of acceleration for a huge object is a tremendous amount of energy. That level of energy production will lead to degradation of the blast plate.

So 0.4C or 0.25c hardly matters if you are limited to 0.01g acceleration 50 to 80 years spend in acceleration cycles and 100 years spent in transit means payloads become very large.

Lets put a faux bet on this, in 20 years lets re-address the issue with updated science and see who is more correct. I would be willing to bet that in 20 years times future estimates for maximum acceleration and maximum velocity are closer to my estimates. And as time goes on future estimates of maximum velocity will fall.

Im going to go even one step further, in 100 years the highest speed humans will be able to obtain with an unmanned vessel will be under 300,000 m/s (0.001c) and in 1000 years 0.01c and that will just about be the maximum speed humans unmanned strategies ever obtain relative to the sun's velocity in space. Sending a human into space at either speed would be a suicide mission. I suspect these missions will be conducted on channeled solar EM conduits and some sort of EM/ion drive conversion. This prediction is based on the fact that an easier technology (fusion power) is well behind schedule and not likely to be implimented in space in the next 100 years, maybe 1000 years and is heavy technology. The anti-matter/matter devices will prove to have a size limitation (probably on the order of milligrams per containment unit) and require a magnitude more development time. At 0.01c going to a goldilocks planet would likely take 1000 to 10000 years, and therefore manned missions are not going to be possible.

Its amazing that people who are dead set against the cannae drive can be so convinced by the musings of anti-matter fantasizers.

[AngelLestat]

Simulated is the key word. If lead is the blast plate, what happens to the lead over time. 0.6c/g and 0.99c/g is fiction, pure and simple, its a hype train used to keep supercollider and space research funding going.

Isp is measure in seconds. So not sure your intention to add / gravity in the unit.

All points that you only know one method to get propulsion with antimatter, which is absorbing the energy then release it in a collimated way. Even doing that there is not problem with heat, because it depends on how good are you redirecting that heat or how much acceleration you want.

The engine of any car will also melt without a colling system.

But then you have the magnetic nozzle method, which you only absorb a fraction of the energy release.

Another method may be this mentioned by F. Winterberg

http://vixra.org/pdf/1201.0026v1.pdf

ISP does care about the nozzle, and if the nozzle is degrading because its a soft material in which the lead can undervaporization due to the demands of acceleration. In other words you are basically arguing that it is possible to reach 0.4c with M/AM device when you ignore the weight of lead (one of the most dense materials known to man) and the containment devices, and the AM/M injection devices.

The nozzle is only magnetic, there is not solid material there. You can create a huge plasma-magnetic nozzle if you want that will cover very well the field generator.

Its amazing that people who are dead set against the cannae drive can be so convinced by the musings of anti-matter fantasizers.

You based your conclusion in wrong methods and hypothesis. Edited May 20, 2015 by AngelLestat

[Tim_the_Plumber]

Will we be capable of interstellar travel within this century?

Starting off or getting there?

I fully expect us to get the mining of asteroids going which will lead to build industry in space then large habitats.

These habitats will become more and more wonderfully heaven like.

Some will have very large populations. Billions of people. We are probably well out of this century here...

At some point one of these will have a fall out with the rest of us and choose to fly off to avoid the controls and laws of the rest of humanity. See the Mayflower.

The journey to the next stars taking 150 years is not a problem when you are a billion people doing all the things that any advanced economy does.

[billbobjebkirk]

Manned?... No, absolutely not.

Unmanned?.... Maybe.

Will we actually get that probe to another star within this century? Not a chance.

[Greenfire32]

We can do it right now. It's just that no-one wants to die for a journey they'll never see the end of.

Aside from concepts that are little more than science fiction at this point, generational ships are our only option. We have the resources to build them and we have the technology to support them. We just don't have the motivation.

But much like the energy crisis or the climate crisis, we'll probably wait until either the 11th hour or until it's too late before we do something.

/2cents

[TheSaint]

Will we be capable of interstellar travel within this century? Personally, my answer is: Insufficient data. We just don't know enough about what it will take at this point to say one way or the other. But here is what we do know:

- There are many possible ways to travel interstellar distances that don't violate the laws of physics that have been ruled impossible by the current limitations of technology.

- There are technologies today, many of which are in common use, that would have been considered impossible fifty years ago. (Handheld computers that can access data wirelessly from servers on the other side of the planet, graphene, genome mapping, cloning, etc.)

- Many of these technologies were predicted, but many of them were completely unforeseen, breakthrough technologies.

So, I don't know if we will send an expedition to another star during this century or not. But I do think that arguing that it won't happen based on the fact that our current or predicted technology doesn't permit it is pointless, because if we do send one the technologies that enable it will in all likelihood be breakthrough technologies that none of us saw coming.

I'll also say this: Keep an eye on quantum computing. Not that quantum computing will, in-and-of itself, enable interstellar travel, but it is going to have a remarkable effect on a great many fields, including theoretical physics, material science, nanotechnology, biology, medicine, and other fields that will be enabling to interstellar travel.

[Nibb31]

Aside from concepts that are little more than science fiction at this point, generational ships are our only option. We have the resources to build them and we have the technology to support them. We just don't have the motivation.

Generation ships are science fiction. It would require propulsion, orbital construction, massive access to orbit, and closed loop life support with regenerative food production and plenty of other technologies that are centuries away.

But much like the energy crisis or the climate crisis, we'll probably wait until either the 11th hour or until it's too late before we do something.

/2cents

Interstellar travel isn't something that would help us in our 11th hour.

[Greenfire32]

Generation ships are science fiction. It would require propulsion, orbital construction, massive access to orbit, and closed loop life support with regenerative food production and plenty of other technologies that are centuries away.

We have propulsion necessary for a generational ship...We have the ABILITY for orbital construction, we just haven't ever done it on a grandish scale. We wouldn't need "massive" access to orbit, we'd just need to redesign our current launches to accommodate people rather than robots. We have the resources required for regenerative food production.

Am I saying it's easy? No. Am I saying it's do-able? Yes. The only bit that stands in our way RIGHT NOW is the cost it would take to do something like that. And not "cost" as in purely monetary definitions, but the cost of life, the cost of materials, the cost of fuel.

We COULD do it right now. It would just be so unbelievably hard, that we'd be far better off waiting until we have better-suited tech for such a journey. And that's really where the lack of motivation comes from.

Yes, I COULD sail across the ocean to the United Kingdom. But it would benefit me far more if I just bought a plane ticket and let the experienced pilots fly me there. Doesn't mean the journey is IMPOSSIBLE, but rather UNFATHOMABLE. There's a difference there.

----EDIT----

Really all I'm trying to say is that it is possible with current tech. It may not be the most feasable, nor the most smart thing to do, but we could do it. It would take thousands of years to get anywhere, but we could theoretically do it.

What I'm not saying is that we SHOULD do it. And the reason for that is what you've already highlighted. We don't really have propulsion systems that can handle that kind of journey in a timely manner. We don't really have regenerative food sources that won't lose diversity over time. We don't really have the infrastructure set up to even construct such a ship in orbit yet.

So It's POSSIBLE, just not PRACTICAL in the least.

Interstellar travel isn't something that would help us in our 11th hour.

I never said it would?

What I said was that we, as a species, probably wont take interstellar travel very seriously until it's abundantly clear that we HAVE to leave Earth or until after it's already too late to save ourselves. At which point interstellar travel would become a statistical impossibility. However:

Does jumping out of a burning building really help you? Nope.

But you would probably do it anyway out of desperation.

("you" is general)

Edited May 20, 2015 by Greenfire32

[pendant]

Do you think we will be capable of interstellar travel within this century? If so how? And if not, why?

Not a chance. Humanity is on the verge of destroying its nest. By the end of this century there will be no fuels left for propulsion; we will need a technological breakthrough just to survive, let alone try to explore the universe. Anyone who thinks otherwise has their heads firmly in the sand, and needs to take heed of

(RIP) and stop listening to the nonsense thrown at us by mass media.

[Bill Phil]

For a decently sized starship(about 100,000 tonnes) to travel at 50% of the speed of light, it would take about as much power as a Type I civilization. If it's accelerated at 1g, that is. You could lower the power requirement if you had less acceleration.

Traveling between stars takes a LOT of power.

Btw, humanity as a whole is about a Type 0.7 civilization.

[AngelLestat]

Does jumping out of a burning building really help you? Nope.

But you would probably do it anyway out of desperation.

This might be true only if we discover than the sun will explote and we found with huge huge telescope that there is (with 100% of certain) an habitable planet in one of our closest stars.

To organize the construction of such ship, with all the caos it will be the earth knowing the news about the sun would not be easy.

This ship would have a lot of chances to fail.

So all this is highly unlikely to happen.

----------------------------------------------------------------------

My solution to interplanetary travel in this century:

The mass of the craft when we talk about huge deltaV is essential, antimatter is out of this century, and even fusion is not enoght, that will increase the total mass and complexity (cost) of the craft by a lot.

What if we can make our probes with few kg of material?

We just need to master technologies as graphene, CNT and 3d printing.

We can build these solar sails using 3d print spiders in space, with all instruments printed over the same sail.

You can make a solar sail with a density close to 0.01g/m2, this mean that you can make a fly-by very close to the sun (heat is not a problem) which it will provide huge accelerations, this allow speeds close to 6% light speed without using propellent or earth energy.

They can brake using the same technique in destination, and go everywhere you want in that solar system.

The sail can change is shape to act as a huge parabolic mirror to alow interplanetary comunications with low energy requirements.

You just detach the laser emissor/receptor to reach the focal point of the sail, then return the emissor to the craft after the comunication is done.

I dint enter in details to not make a huge post, but I am confident that I can answer each criticism that you might found about this.

As someone else mention, the speed in interstellar travel is an issue, because if you reach 0.05c in some moment, you will double that speed few decades later which it can surpass the older mission. In this case this is not a problem.

Because we can launch several crafts, they are so light and they require so few materials that once you can make one in space, you can make many more with low cost. So you keep launching these sails to all stars, this allow a continuity flow of data from everywhere.

Edited May 20, 2015 by AngelLestat

[PB666]

Isp is measure in seconds. So not sure your intention to add / gravity in the unit.

All points that you only know one method to get propulsion with antimatter, which is absorbing the energy then release it in a collimated way. Even doing that there is not problem with heat, because it depends on how good are you redirecting that heat or how much acceleration you want.

The engine of any car will also melt without a colling system.

But then you have the magnetic nozzle method, which you only absorb a fraction of the energy release.

Another method may be this mentioned by F. Winterberg

http://vixra.org/pdf/1201.0026v1.pdf

The nozzle is only magnetic, there is not solid material there. You can create a huge plasma-magnetic nozzle if you want that will cover very well the field generator.

You've based your conclusion in wrong methods and hypothesis.

Oh boy so plasma is generated and directed with majical dark energy from hyper-hyperspace (waving hands in the air madly)

1. You've based your conclusion on in-silico science (or as I call it - rejection fodder), with essentially no experimental basis.

2. Containing the effects of high energy gamma is not trivial, the energy once absorbed is one of the most destructive energy that exists, it literally can create matter.

I base my conclusions on the basic function of propulsion as applied to the problem, you have to accelerate a payload toward a target and decelerate.

The more you talk about magnetic nozzel (all but payload not fuel, what generates the plasma?, what directs the plasma?), lead shielding (all but payload not fuel), antimatter containment fields (all but payload) the more you convince me that you don't believe what you are saying given the unwillingness to consider payload or deceleration. Nothing of what you or K2 has said has made ANY attempt what-so-ever to factor in the payload or deceleration. All you are talking about is what if antimatter could be used to accelerate itself, how fast might it go. Pigs also might fly, but we don't talk about flying pig propulsion system.

What I am talking about is accelerating moving and decelerating a payload that includes humans. Lets get the stories strait, if you want to bounce anti-matter into matter and create momentum, you don't need to include space in the argument or interstellar travel.

This conversation, more or less, is the same conversation we had previously regarding warp fields and the basic problem with both conversations is that if you _believe_ warp fields are possible then you support them, irregardless of whether or not the basic underlying principles of field energetics or propogation are plausible under any realistic/practical scenario.

In fact the most realistic propulsion system using antimatter is an antimatter triggered fission/fusion reaction the claimed maximum speed is around 0.01c - 0.025c.

NASA does not mention antimatter at all as a potential propulsion source, it briefly mentions the unfeasibility of creating and storing antimatter for science.

Come back to the topic of manned interstellar travel when there is a speck of experimental science that suggests its technologically approachable. You would have better luck shrinking humans to the size of a pocket mouse than getting a matter/antimatter propulsion system to 0.8c.

Positron annihilation has also been proposed for rocketry. Annihilation of positrons produces only gamma rays. Early proposals for this type of rocket, such as those developed by Eugen Sänger, assumed the use of some material that could reflect gamma rays, used as a light sail or parabolic shield to derive thrust from the annihilation reaction, but no known form of matter (consisting of atoms or ions) interacts with gamma rays in a manner that would enable specular reflection.- wikipedia and just how do you store a positron only antimatter source?

nough said.

[AngelLestat]

Oh boy so plasma is generated and directed with majical dark energy from hyper-hyperspace (waving hands in the air madly)

what??? Are you high? if you are not able to follow a discussion, then dont.

1. You've based your conclusion on in-silico science (or as I call it - rejection fodder), with essentially no experimental basis.

We know all the physsics involve.

We have experiment knowledge about magnetic fields, antimatter, radiation, gamma rays, materials, heat, etc.

Science and theories allow us to make predictions, as under certain speed and trajectory what path follow a body under the effects of gravity.

In an antimatter nozzle complexity between different effects adds disparities against theory, but you can also measure how restricted will be your error.

2. Containing the effects of high energy gamma is not trivial, the energy once absorbed is one of the most destructive energy that exists, it literally can create matter.

Is call pair production and it can be used to increase the efficiency, gamma rays can not be focus with a magnetic nozzle, so if it creates matter again, can be redirected. And try to avoid the sensationalism words, they had not effect here.

I base my conclusions on the basic function of propulsion as applied to the problem, you have to accelerate a payload toward a target and decelerate.

The more you talk about magnetic nozzel (all but payload not fuel, what generates the plasma?, what directs the plasma?), lead shielding (all but payload not fuel), antimatter containment fields (all but payload) the more you convince me that you don't believe what you are saying given the unwillingness to consider payload or deceleration. Nothing of what you or K2 has said has made ANY attempt what-so-ever to factor in the payload or deceleration. All you are talking about is what if antimatter could be used to accelerate itself, how fast might it go. Pigs also might fly, but we don't talk about flying pig propulsion system.

Yeah, everyone here knows the difference between dry mass and wet, but not sure if you do...

You quote me, but still I dont find any word yours that is a direct answer of what I am saying..

But from what I can interpret, you still thinking that you need to absorb +50% of the energy.

You dont need to absorb the gamarays, you dont need lead. Meanwhile more lightweight is your craft, less gamma rays you will absorb (from those you cant not redirect with the magnetic nozzle, read about pions, neutral or charged, decaying, etc)

To protect the crew if is manned, you just use the inverse square law in distance with radiation. Place your crew at 1 km from the engines, place your engines in front in angle to the sides.

Also forget about the plasma, that is another method to inflate magnetic fields, it will just confuse you

And remember, it all depends on your acceleration and colling system.

What I am talking about is accelerating moving and decelerating a payload that includes humans. Lets get the stories strait, if you want to bounce anti-matter into matter and create momentum, you don't need to include space in the argument or interstellar travel.

bounce??? you mean annihilation? Also I am not talking of manned ships, but wherever.. space in the argument of interstellar travel?? what???

This conversation, more or less, is the same conversation we had previously regarding warp fields and the basic problem with both conversations is that if you _believe_ warp fields are possible then you support them, irregardless of whether or not the basic underlying principles of field energetics or propogation are plausible under any realistic/practical scenario.

Ok, confirm, you are high.

I never had that conversation with you, I dont defend warp drive, that is K2. I only focus in the current and upcomming technologies that might have real applications in the near term future.

NASA does not mention antimatter at all as a potential propulsion source, it briefly mentions the unfeasibility of creating and storing antimatter for science.

yes they mention it, the same as how hard is storing and creating antimatter, which if you remember, is what I said in my first answer to you..

I said: The difficult about antimatter is storing and production, that problem is out of this century, but not the engine.

The engine is feasible with our current technology and knowledge.

Come back to the topic of manned interstellar travel when there is a speck of experimental science that suggests its technologically approachable. You would have better luck shrinking humans to the size of a pocket mouse than getting a matter/antimatter propulsion system to 0.8c.

You are answering me? because not sure about what are you talking any more, I was discussing with you just the feasibility of antimatter engines.

Edited May 21, 2015 by AngelLestat

[magnemoe]

For a decently sized starship(about 100,000 tonnes) to travel at 50% of the speed of light, it would take about as much power as a Type I civilization. If it's accelerated at 1g, that is. You could lower the power requirement if you had less acceleration.

Traveling between stars takes a LOT of power.

Btw, humanity as a whole is about a Type 0.7 civilization.

This, an major fail in Avatar, made more fun with the short traveling time, had energy had any cost at all they would used some more time traveling.

If you have unlimited electricity the setting don't make much sense.

---

how is 0.7 civilization calculated, human energy production is just an tiny faction of the sunlight earth receive. 0.01% I belive.

[cicatrix]

how is 0.7 civilization calculated, human energy production is just an tiny faction of the sunlight earth receive. 0.01% I belive.

Type I utilizes the power of its own planet. You're talking about Type II - utilizing the power of the host star. I don't have the reliable figures right now, but 0.7 seems more or less accurate. Though, I don't know whether we should take the energy of the molten planet core into account.

[ChrisSpace]

All the particle accelerators in the world would take decades to produce even a single gram of antimatter, and our storage techniques cant handle containing antimater for that kind of delay. Not this century.

I agree that antimatter in any commercial non-purely-scientific use is centuries away. The stuff takes a small country's worth of energy to create a visible amount, and said amount can't currently be contained for more than a few minutes. Also remember that antimatter is extremely dangerous. Just 1 gram of it combining with one gram of normal matter creates a 43 kiloton explosion. For comparison, the nuclear bombs dropped on Hiroshima and Nagasaki only had yields of 15 and 20 kilotons. And this is just from one gram of antimatter, an interstellar spaceship will need several tons of it, enough to wipe off a large continent.

At 1% ligth-speed, it take 500 years to go to proxima centaury.

At 10%, 50 years. More reseonable. We need 30 000 000 m/s DeltaV So, the launch will be for 2050, you have 35 years for finding that.

Your calculations are slightly off. At 0.1c the trip to the centauris will only take 43 years. But that still means that to get there in this century we will need to launch it in 2057. Good luck getting any kind of 0.1c propulsion system by then.

Wouldn't in-space resource mining make it viable to construct a sort of interstellar highway, consisting of giant lasers or particle cannons, built and maintained by automated spacecraft, which in turn are also built in Space in part or in whole, as well as ships to make use of those beams? Of course, there would need to be some kind of justification to travel between Stars. Habitable worlds maybe?

Habitable worlds to would certainly be a large motivator for interstellar travel, like in Civilisation: Beyond Earth. The only problem with the giant laser-sail network you propose is the energy requirements. If you look here (https://en.wikipedia.org/wiki/Interstellar_travel) and look at the beamed propulsion section, a manned expedition to epsilon eridani requires 75 million gigawatts of power. Good luck finding a way to power the laser, or even design one that could cope with such energy.

Even if we have technology which we don't it's still hardly possible. There must be economic reasons behind it. We haven't even explored the Solar system. There are centuries of work ahead just to explore the neighboring space. Then, perhaps, we might be in position to start thinking about interstellar travel.

Agreed. Once we have colonized the moon, Mars, Venus, Ceres and the moons of Jupiter and Saturn, and have built huge solar collectors on mercury, and have a few space elevators on earth, the moon and mars, then we can begin interstellar expansion. But only then.

I don't expect any breakthrough in propulsion methods in the near future so, velocities of about 100-150 km/s will probably be our limit for quite some time (very optimistic estimation).

This is actually pessimistic if you ask me. With modern technology, Nuclear-electric ion or magnetoplasma drives can probably bring the limit up around 600km/s, or 0.002c. Even with this, though, the centauris are still 2150 years away. Good luck keeping any sort of spaceship operating from now all the way to the year ~4200.

If humanity would focus efforts on Fusion power (more than some side-show called ITER that is more often used for political purposes to show Fusion is not viable and we should continue to encourage oil and coal extraction), we could manage probes that could travel at significant portions of the speed of light...

This, fusion propulsion, will probably be our answer. Icarus interstellar has already designed 4 fusion probes for alpha centauri, and they all seem doable for the 23rd-century space community.

http://www.icarusinterstellar.org/a-ship-called-resolution-project-icarus-workshop-update-14/

http://www.icarusinterstellar.org/meet-firefly-project-icarus-workshop-update-24/

http://www.icarusinterstellar.org/project-icarus-workshop-update-34-the-ghost-ship/

http://www.icarusinterstellar.org/ultra-dense-deuterium-fueled-starship-project-icarus-workshop-update-44/

Nuclear Salt Water Rocket.

This is even more environmentally scary than an orion drive. It is basically a continuously detonating orion drive with several times as much radioactive death coming out. Good luck getting permission to use one within a million kilometers of an inhabited area.

I think we have a decent chance... if another Cold War happens and we have to race Russia (or whoever) to the next star.

Firstly, are you referring to the Cold War II that we are witnessing right now? Even if there is a Cold War III, it will never see a space race to another star. The timescales and resources involved are simply unsuited to a political rivalry. By the time the probes get there, the competing nations that launched them will have completely changed to the point where the rivalry that launched the probes will be a distant memory.

United world government might speed things up...

That will never happen. Never. It is impossible for a species like us to all merge as one nation. If other planetary colonies become their own nations, that might make it slightly more likely.

1. No Money

2. No Interrest

The money is there, it is just being spent on killing people in the middle east and elsewhere, and technology that will make killing those people faster and more efficient.

Political structure is too immature and self centred for forward thinking beyond 5 years on average.

For the most forward-thinking countries, like China and India, the maximum 'government visibility' is about 5-10 years. For America it is more like 1 year, and for Australia it is about 2 weeks.

Starting off or getting there?

I fully expect us to get the mining of asteroids going which will lead to build industry in space then large habitats.

These habitats will become more and more wonderfully heaven like.

Some will have very large populations. Billions of people. We are probably well out of this century here...

At some point one of these will have a fall out with the rest of us and choose to fly off to avoid the controls and laws of the rest of humanity. See the Mayflower.

The journey to the next stars taking 150 years is not a problem when you are a billion people doing all the things that any advanced economy does.

Space colonies with billions of people? Habitats being self-sustaining for hundreds of years? Interstellar colonisation is easier than that.

We have propulsion necessary for a generational ship...We have the ABILITY for orbital construction, we just haven't ever done it on a grandish scale. We wouldn't need "massive" access to orbit, we'd just need to redesign our current launches to accommodate people rather than robots. We have the resources required for regenerative food production.

Am I saying it's easy? No. Am I saying it's do-able? Yes. The only bit that stands in our way RIGHT NOW is the cost it would take to do something like that. And not "cost" as in purely monetary definitions, but the cost of life, the cost of materials, the cost of fuel.

The materials do build an interstellar generation ship do exist on earth. If we can't find enough resources on our national soil we can clear out and mine Greenland or Antarctica. The technologies mostly exist, although there are still unresolved problems. However, generation ships are a concept doomed from the start. You can not have a society in a pressurized, confined area that will remain peaceful for more than a century or so. It is statistically certain that at some point, somebody onboard will sabotage the mission, and it only takes a tiny event to kick off a civil unrest that will inevitably escalate. And it only takes one carefully-placed bomb to blow a hole in the ship and kill everyone onboard. Any manned mission taking more than 100 years should not be attempted at all.

Humanity is on the verge of destroying its nest. By the end of this century there will be no fuels left for propulsion; we will need a technological breakthrough just to survive, let alone try to explore the universe. Anyone who thinks otherwise has their heads firmly in the sand, and needs to take heed of

(RIP) and stop listening to the nonsense thrown at us by mass media.

Even better, read the book The collapse of Western civilization: a view from the future. It provides a very detailed look at how climate change alone can and will kill billions of people very rapidly in the second half of the 21st century. It also shows why there will be no real motive to prevent the collapse until it is far too late. Leaving earth is not a matter of 'In the unlikely event bad things happen we will survive', it is a matter of 'Bad things are going to happen and we need to survive'.

What if we can make our probes with few kg of material?

We just need to master technologies as graphene, CNT and 3d printing.

We can build these solar sails using 3d print spiders in space, with all instruments printed over the same sail.

You can make a solar sail with a density close to 0.01g/m2, this mean that you can make a fly-by very close to the sun (heat is not a problem) which it will provide huge accelerations, this allow speeds close to 6% light speed without using propellent or earth energy.

They can brake using the same technique in destination, and go everywhere you want in that solar system.

The sail can change is shape to act as a huge parabolic mirror to alow interplanetary comunications with low energy requirements.

You just detach the laser emissor/receptor to reach the focal point of the sail, then return the emissor to the craft after the comunication is done.

I dint enter in details to not make a huge post, but I am confident that I can answer each criticism that you might found about this.

As someone else mention, the speed in interstellar travel is an issue, because if you reach 0.05c in some moment, you will double that speed few decades later which it can surpass the older mission. In this case this is not a problem.

Because we can launch several crafts, they are so light and they require so few materials that once you can make one in space, you can make many more with low cost. So you keep launching these sails to all stars, this allow a continuity flow of data from everywhere.

We still need to master the materials technology to make such a sail ship. Once we have, we will need to just hope we aren't struck by a single micrometeoroid, as it would go through the sail like a 20 kilogram bowling ball goes through a glass window.

[magnemoe]

Type I utilizes the power of its own planet. You're talking about Type II - utilizing the power of the host star. I don't have the reliable figures right now, but 0.7 seems more or less accurate. Though, I don't know whether we should take the energy of the molten planet core into account.

Think we can say that type I is energy production equal to energy from sun hitting the planet, all does not have to be solar light, you can only use an faction of this energy on the planet of obvious reasons. Class II is dyson swarm style. For an large starship like venture star you will have to be as close to Class II as we are Class I, you would hardly use all your energy powering the starship.

Most plausible way is probably to mine Mercury and build giant solar arrays around mercury orbit. Both for lasers and antimatter production.

[AngelLestat]

Your calculations are slightly off. At 0.1c the trip to the centauris will only take 43 years. But that still means that to get there in this century we will need to launch it in 2057. Good luck getting any kind of 0.1c propulsion system by then.

The topic said interstellar travel in this century, it does not said that you need to reach a star before this century, just start the travel in a practical way.

This, fusion propulsion, will probably be our answer. Icarus interstellar has already designed 4 fusion probes for alpha centauri, and they all seem doable for the 23rd-century space community.

http://www.icarusinterstellar.org/a-ship-called-resolution-project-icarus-workshop-update-14/

http://www.icarusinterstellar.org/meet-firefly-project-icarus-workshop-update-24/

http://www.icarusinterstellar.org/project-icarus-workshop-update-34-the-ghost-ship/

http://www.icarusinterstellar.org/ultra-dense-deuterium-fueled-starship-project-icarus-workshop-update-44/

No, fusion has a lot of flaws, the ship even if you try to carry the most lightest instrument and things needed to complete the mission, due to the rocket equation, the ship ends being massive, bigger the ship its, more shielding do you need --> more mass. That ship would perform much worst than the solar sail approach, and it will be thousands of times more expensive.

The money is there, it is just being spent on killing people in the middle east and elsewhere, and technology that will make killing those people faster and more efficient.

true

We still need to master the materials technology to make such a sail ship. Once we have, we will need to just hope we aren't struck by a single micrometeoroid, as it would go through the sail like a 20 kilogram bowling ball goes through a glass window.

Yeah, but we are very close. All the things that I ask, can be made in laboratory at low scale, CNT can achieve that density without the need of graphene, and we already begin with big scale production in CNT. To make it reflective we can make holes (which reduce the density) at the wavelenght scales, the perfect mirror was do it with this method. But not sure how good will be CNT in this matter, because you not add different wavelenghts.

About being struck by a single micrometeroid.. there is nothing more safe and resistent than a solar sail of this characteristics, is so thin, that if a particle or any size body hit the sail, it will just made a tiny hole in the sail (this is not a glass mirror), the whole energy of the impact does not remain in the sail, because you dont decelerate the particle or micrometeoroid. All the fragments of the collision does not hit new particles of the sail, you can think in the sail as a 2d structure.

There are papers explaining this in more detail. Solar Sail is the most cheap and effective method you can find.

[SargeRho]

12% is twice as fast as the solar sail's 6%, which is what the Daedalus spacecraft potentially could reach - with I think a 5 year acceleration phase.

[AngelLestat]

12% is twice as fast as the solar sail's 6%, which is what the Daedalus spacecraft potentially could reach - with I think a 5 year acceleration phase.

But is a fly-by... 40 years traveling to stay only 1 day in that star system, that is just enoght to take 3 pictures of a single planet at a certain distance (which it will not be very close)

Solar sails can decelerate and use infinite deltav to explore that solar system. They will cost many orders of magnitud less, they can act as huge parabolic dish to improve communication, what you will need to do the same with a fusion ship?

Just gathering all the deuterium needed to the craft would be super hard to do. What if the interstellar dust just damage the craft enoght that you lose contact? All that huge investment for nothing?

Once you have all to build a solar sail in space, you can launch them very often, so if someone fails for X reasons, you just have 10 more in travel to the same or different destinations.

Also the solar sail reach 6% light speed in few days.

[SpaceChipmunk]

Not this century. Maybe one day.

You really have to realise the distances involved here. This century ends in 85 years, it will take 15 years just to get a basic mission to Mars on the ground. Then they will take several years conducting experiments. So you are already looking at about 2040 before they have any solid conclusions over that mission, resulting in only 60 years left. Then they would have to plan for the next step, maybe to the Galilean moons, most likely Europa for water. Building the required infrastructure to send the mission there would take a couple of decades at the least! That isn't even half the distance required to go interstellar! By the end of the century I would say you are more looking at landing on Europa than even contemplating Interstellar travel.

[SargeRho]

But is a fly-by... 40 years traveling to stay only 1 day in that star system, that is just enoght to take 3 pictures of a single planet at a certain distance (which it will not be very close)

Solar sails can decelerate and use infinite deltav to explore that solar system. They will cost many orders of magnitud less, they can act as huge parabolic dish to improve communication, what you will need to do the same with a fusion ship?

Just gathering all the deuterium needed to the craft would be super hard to do. What if the interstellar dust just damage the craft enoght that you lose contact? All that huge investment for nothing?

Once you have all to build a solar sail in space, you can launch them very often, so if someone fails for X reasons, you just have 10 more in travel to the same or different destinations.

Also the solar sail reach 6% light speed in few days.

Unless you give it a magnetic sail. It would cut into the payload, but you could slow down considerably at the target location. And unlike a solar sail, the Daedalus has adequate protection for relativistic space travel: A beryllium shield in front that is gradually eroded, producing a protective dust cloud traveling ahead of the ship.

The magnetic sail could also be used during the acceleration phase, using the solar wind or particle beams for some extra speed.

Edited May 21, 2015 by SargeRho

[AngelLestat]

Unless you give it a magnetic sail. It would cut into the payload, but you could slow down considerably at the target location. And unlike a solar sail, the Daedalus has adequate protection for relativistic space travel: A beryllium shield in front that is gradually eroded, producing a protective dust cloud traveling ahead of the ship.

The magnetic sail could also be used during the acceleration phase, using the solar wind or particle beams for some extra speed.

You can not use the magnetic sail as acceleration, the solar wind is 1000 times less stronger than photons bouncing on a solar sail. Besides your craft is in wet mode with several tons.

Magnetic sails are good to brake as you said, but they are good to slow down from very fast speeds to lower speeds, is like a car and the air friction, at 500 km/h it will lose speed super fast, at 200km less, and at 10km/h (if we ignore wheel friction) it will keep moving a long time.

Mag sails to brake from 95% light speed to 10% are very good, to brake those last 10% not so much, more taking into account that you need to save some fuel to brake the last km/s of deltav, so your craft still count as wet mass.

Here you have an study taking into account with and without mag sails for Icarus:

http://www.academia.edu/4133057/Braking_via_Magnetic_Sails_vs_Two_Stage_Fusion_Rockets

They lower by a lot the intial wet mass of the ship with magnetic sails, but the travel time increase to 100 years to alpha centauri, that is how much takes to brake at that speed.

About the solar sail erosion against the interstellar dust..

You have 0.1 atoms /cm3, the distance to alpha centauri is 9x10¹⁶cm, the graphene density is 3,8x10¹⁵ atoms/cm2, not all atoms will hit another atom in the sail, but we can said that it will need some kind of shielding for sure.

So to avoid that, once the acceleration ends (leaving the solar system) the solar sail rotates to be parallel to the direction of motion. Then we use the external mag sail to shield against the interstellar dust without lose much speed.

Like this graphic:

The sail at launch will have an external layer to provide extra mass to achieve a good sun diving and extra thrust due evaporation when reach the sun periapsis.

It will have magnetic rails, with superconductor tiny masses that will move as any maglev train. That would help to control the sail, you can change the speed of the sail spin which provide the centrifuged force, also it can shape and balance loads over the sail. It helps to rotate, shape or different movements that the sail may need. To allow extra control when we dont have solar pressure, we can have tiny lasers and mirrors, the light bounce 1000 times so ir provides a descent net force.

So this sail would need just more advances in nanotechnology and 3d printing. I guess in 2055 it may be possible to start with the first launch test, and in 2970/80 start with the first mission.

Edited May 22, 2015 by AngelLestat

[Bill Phil]

This, an major fail in Avatar, made more fun with the short traveling time, had energy had any cost at all they would used some more time traveling.

If you have unlimited electricity the setting don't make much sense.

---

how is 0.7 civilization calculated, human energy production is just an tiny faction of the sunlight earth receive. 0.01% I belive.

Carl Sagan formulated it.

Log base 10 of the civilazation's power output in Watts(I think...) minus 6, all over 10.