Debunking Interstellar Travel: Separating Fact from Fiction

[enorbet]

@newjerseyrunner - While I'm quite sure Chronos can, and likely will, respond for himself I felt compelled to interject. I am a champion of thinking outside the box but I do hope you realize just how far outside your example is. Since we know that for the most part things are pretty much like they are here the Laws that govern biology have to be stretched really far since in our experience the most complex lifeforms capable of such lifespans are on the level of yeast. Yet you imagine they are so complex they also have near light speed propulsion. The concept of a race that lives for even thousands of years asks a lot of serious questions not the least of which is reproduction and overcrowding just to name a few.

I think it is far more likely since at the turn of the century a vaguely mathematically possible spacetime-bending warp drive has at least been seriously conceived this will be the means for any civilization to achieve Interstellar "travel". Still it would seem the energy required to achieve such a broad and powerful effect is a very long way off, at best... for any manner of civilization.

 

[DrStupid]

biology have to be stretched really far

or to be abandoned

 

[newjerseyrunner]

@newjerseyrunner - While I'm quite sure Chronos can, and likely will, respond for himself I felt compelled to interject. I am a champion of thinking outside the box but I do hope you realize just how far outside your example is. Since we know that for the most part things are pretty much like they are here the Laws that govern biology have to be stretched really far since in our experience the most complex lifeforms capable of such lifespans are on the level of yeast. Yet you imagine they are so complex they also have near light speed propulsion. The concept of a race that lives for even thousands of years asks a lot of serious questions not the least of which is reproduction and overcrowding just to name a few.

I think it is far more likely since at the turn of the century a vaguely mathematically possible spacetime-bending warp drive has at least been seriously conceived this will be the means for any civilization to achieve Interstellar "travel". Still it would seem the energy required to achieve such a broad and powerful effect is a very long way off, at best... for any manner of civilization.

I would assume that a species would use it's knowledge of medicine to slowly increase it's own lifespan, slowly replace body parts with more durable machinery, and eventually abandon biology completely. I think our species will be able to do that in less than a thousand years, let alone a million.

 

[Cadar]

"Delusional fantasy" might be a bit strong, but yes, it looks as though interstellar travel by any means we can envisage based on current understanding of physics and the complexities involved tends to suggest that it belongs in the realm of science fiction. At least for now. KSR - one of the best writers in the field in my personal opinion - has this to say on the subject as a whole, not just because of the propulsion issue, but also because of the human, biological and other factors.

http://www.scientificamerican.com/article/what-will-it-take-for-humans-to-colonize-the-milky-way1/

Simply put, barring some new form of FTL propulsion we haven't discovered yet (gravity drive, anyone?), we're going to be stuck in this solar system for the foreseeable future. Which is probably for the best, considering the utter catastrophe we've made of planet Earth.

 

[anorlunda]

It's easy for me to imagine a species that has members that enjoys long bouts of solitude and lives for tens of thousands of years with the aid of medical technology.

Unless you assume FTL, then you better change "thousands" to "millions".

If we are want to presume FTL just on the principle that human achievement knows no limit, then we might as well imagine a "star trek" beam-me-up transporter that could beam remote planets, and even remote galaxies to our doorstep.

Dreams of space westerns depend on a very narrow range of visions of future technology; good enough for FTL ships, but not good enough to make such ships unnecessary.

 

[Drakkith]

I would assume that a species would use it's knowledge of medicine to slowly increase it's own lifespan, slowly replace body parts with more durable machinery, and eventually abandon biology completely. I think our species will be able to do that in less than a thousand years, let alone a million.

I imagine that we'll find ways to improve our own bodies without completely replacing them with machines.

 

[russ_watters]

Unless we figure out a workaround to the speed of light, space is simply too vast for interstallar travel. The demands are so enormous even antimatter would be a laughable excuse for an energy source.

Even worse, we're a long, long way from the speed of light being a limiting factor in our space travel. The fastest spaceships we can muster today can travel at around 0.01% of the speed of light. Even if we can somehow find the technology to increase spaceship speed by a factor of a thousand, Relativity will still be irrelevant. We're somewhere between hundreds of years and never away from being able to come even that close.

 

[marcus]

...I agree that there are monumental challenges that we may never overcome. It also seems more likely that our machines (rather than humans themselves) will be the first visitors to other star systems. Especially given the current direction of exploration in our own Solar System - we've sent our machines to the outer reaches, rather than going ourselves.
...

If our machines ever reach a comparatively nearby exoplanet, and it turns out to be a nice place, then it might be possible to send frozen zygotes there accompanied by robotics able to provide the necessary environment: do the nursing, parenting, and socialization.

A zygote is a single cell, a fertilized ovum, the first stage of an embryo. I wonder how long a zygote can last, frozen, and still develop properly when retrieved from storage. 100 years? A thousand years?

If exploratory machines can get somewhere and still function reliably once they arrive, I see nothing in principle that would prevent their establishing a colony of humans---perhaps colonies including other species of plants and animals as well.

Sending an "Ark" of live humans seems like the wrong idea: expensive, bulky, complicated, prone to failure.
One has to count on AI and robotics having reached a level where it can transmit our culture and foster recognizable fully human individuals, bridging the long gap when things are in storage during transit.

I imagine this could be tried as an experiment at shorter distances, namely in the solar system. Let the robots build the habitat and prepare for a colony somewhere---then hatch some stored "eggs" and raise the humans to populate it.

Shielding from cosmic rays seems more feasible in this picture, the biology one is sending is very compact.

 

[Drakkith]

I imagine this could be tried as an experiment at shorter distances, namely in the solar system. Let the robots build the habitat and prepare for a colony somewhere---then hatch some stored "eggs" and raise the humans to populate it.

That presents one hell of a moral dilemma...

 

[nikkkom]

Fair comment, but well established physics will still be the same.
At present it's incomprehensible what kind of engine could accelerate a fairly massive ship to a substantial fraction of light speed,
but it's not impossible in principle.

Why do you need a substantial fraction of C? If that can't be done, traveling at "only", say, 15000km/s, gets you to another star in some 100 years - not really too long a time. Well established physics has nothing against accelerating macroscopic objects to 15000km/s.

 

[nikkkom]

It's easy for me to imagine a species that has members that enjoys long bouts of solitude

You don't need to be alone on the trip. Ship can be big enough and the crew can be large enough. There are millions, if not billions of people who lived their entire life within some few square kilometers of land and interacted with less than a thousand different people.

 

[rootone]

... 15000km/s, gets you to another star in some 100 years - not really too long a time...

100 (or a few hundred) years would get us to the very nearest stars using present technology, but there are not very many of those close neighbours.
The chances of star in our immediate neighbourhood harbouring a habitable planet are extremely remote.

 

[nikkkom]

100 (or a few hundred) years would get us to the very nearest stars using present technology, but there are not very many of those close neighbours.

We don't have to go to 47 Tucanae in one giant jump. After we reach nearby stars, we can launch further expeditions from *them*.

The chances of star in our immediate neighbourhood harbouring a habitable planet are extremely remote.

Why would you want to live on a planet, that deep potential well? Asteroids are so much better. More accessible, more abundant, and more varied wrt resources. Presumably, asteroids exist around almost every star.

 

[rootone]

Yes there probably are asteroids with useful resources around most stars.
I imagine though, that establishing a variety of heavy industries entirely in space would take a very long time.
I guess your idea is workable in principle though, but in practice what would be the motivation for a project that could take well over 1000 years in total to get humans to a star system that actually might be habitable.
(or have other some other high value of interest)

 

[nikkkom]

Yes there probably are asteroids with useful resources around most stars.
I imagine though, that establishing a variety of heavy industries entirely in space would take a very long time.

Yes.
However, I think having heavy industry in space is a prerequisite for our civilization to efficiently colonize Solar System.

 

[Drakkith]

Here's a question. Are there any kinds of "launching" devices that could provide an initial burst of acceleration instead of having to rely solely on the ship's engines? Something like a very, very large electromagnetic "catapult" similar to the ones proposed for facilitating launches from Earth.

 

[rootone]

Probably doable from an engineering point of view, but to be useful (in terms of noticeably reducing overall journey time) that initial acceleration would need to be huge,
Could a human passenger survive that?, experiencing something like 50G?

 

[Drakkith]

Probably doable from an engineering point of view, but to be useful (in terms of noticeably reducing overall journey time) that initial acceleration would need to be huge,
Could a human passenger survive that?, experiencing something like 50G?

Why would the acceleration need to be so large? If we're talking about building spaceships large enough with enough fuel to accelerate to and from a significant fraction of c, I imagine that building a very long accelerator wouldn't be beyond our capability. But I haven't ran the numbers on any of that.

 

[newjerseyrunner]

Here's a question. Are there any kinds of "launching" devices that could provide an initial burst of acceleration instead of having to rely solely on the ship's engines? Something like a very, very large electromagnetic "catapult" similar to the ones proposed for facilitating launches from Earth.

Like a light sail? It'd have minimal G forces, but be able to reach relativistic speeds. Remember though, that launching isn't the only place where acceleration is needed (unless you just plan on doing a flyby.)

 

[nikkkom]

Why would the acceleration need to be so large?

Let's see.
With assisted 1g acceleration for 3600 seconds, you'd get 36 km/s and the accelerating track structure needs to be 64800 kilometers long (somewhat smaller than Jupiter radius).
At 2g, you get 72 km/s and track length is also x2 - 129600 km.
At 2g and 1800 seconds, you get 36 km/s and track length is smaller: 32400 km.
At 10g and 1200 seconds, you get 120 km/s and track length is 72000 km.

Higher G's are useful, but require your ship to be sturdier (--> heavier).
In any case, attained velocities are too low, you still would need to accelerate much more than that using your ship's propulsion.

[edit] For reference: accelerating for longer time quickly makes the track unwieldy long: 1g for one day requires a track 37 million kilometers long while giving you "only" 864 km/s.

 

[anorlunda]

Here's a question. Are there any kinds of "launching" devices that could provide an initial burst of acceleration instead of having to rely solely on the ship's engines? Something like a very, very large electromagnetic "catapult" similar to the ones proposed for facilitating launches from Earth.

Since we're talking about fanciful future technology, how about an elastic tether that we could attach to a passing asteroid? The name of the ship could be the USS Bungee.

 

[Drakkith]

Let's see.
With assisted 1g acceleration for 3600 seconds, you'd get 36 km/s and the accelerating track structure needs to be 64800 kilometers long (somewhat smaller than Jupiter radius).
At 2g, you get 72 km/s and track length is also x2 - 129600 km.
At 2g and 1800 seconds, you get 36 km/s and track length is smaller: 32400 km.
At 10g and 1200 seconds, you get 120 km/s and track length is 72000 km.

Oh my. Those are some big accelerators...

 

[nikkkom]

Another datapoint:
If 0.1% of mass is converted to kinetic energy with no losses (0.1% conversion is the ballpark of fission) the attainable velocity is ~13000 km/s.
If 1% of mass is converted (fusion ballpark), the velocity is ~42000km/s.

 

[Rubidium_71]

marcus "send frozen zygotes"

One question would be how do the zygotes become fully functioning adult humans? Having holograms and robots raise children didn't work out so well in Lexx... ;) How are they educated to survive in their new environment? Has the environment changed significantly during the long journey?

I wonder if the ultimate feat will be to send just our intelligence to another world via machine. Rather than take extreme measures to preserve such a delicate biological form for an interstellar voyage and then further try to protect or modify our biology for an alien world, a machine intelligence is the most likely winner here. AI is widely believed to be achievable, indeed inevitable. It is a project that can be worked on right here at home and when it's ready we can boot it out into the interstellar medium to make trouble/explore space. If it is self aware and contains a large quotient of human knowledge, in a sense "we" will have a presence beyond the Solar system in time. In a way, the crude prototypes are already being sent out. The further a probe goes, the more it has to look after itself. Remote control only stretches so far,increasing the probability of a sentient interstellar machine. It's probably just a question of when.

 

[rootone]

The best AI's we have so far produced are very good at performing a specific task which they have been programmed for.
They can also 'learn' new strategies within the context of their defined task
We are however nowhere remotely near self-aware machines yet, which could assess any arbitrary situation and determine an appropriate response.
That kind of AI if it's ever achieved would I guess have a personality and emotions as humans do, which would play a part in decisions.
So one such AI would probably respond differently to another, and who knows, maybe they could even fall in love with each other or do stupid things because another AI had made them angry.

 

[mfb]

Since we're talking about fanciful future technology, how about an elastic tether that we could attach to a passing asteroid? The name of the ship could be the USS Bungee.

Current materials limit the tip speed of untapered tethers to ~1 km/s. A reasonable tapering of 1:50 gives 4km/s. And that is just a tether without any load. Carbon nanotubes can achieve higher speeds, but attaching a spacecraft to it? You would not get any relevant speed from it.

That kind of AI if it's ever achieved would I guess have a personality and emotions as humans do, which would play a part in decisions.
So one such AI would probably respond differently to another, and who knows, maybe they could even fall in love with each other or do stupid things because another AI had made them angry.

Same problem with humans. In the future it could also be possible to scan a human brain and simulate it in a computer. Then you can run your spacecraft by a human-like thing without biological life support.

Could a human passenger survive that?, experiencing something like 50G?

10g in the direction "eyeballs in" are sort of tolerable, if they are not too long. Submerged in water and with some liquid breathing technique, more should be possible.

 

[Rubidium_71]

rootone - "We are however nowhere remotely near self-aware machines yet, which could assess any arbitrary situation and determine an appropriate response."

Well, we are talking about the future here (some of the posts on this thread contemplate events that are very far in the future.) Given that progress in space probes is ongoing (we've gone from Sputnik to New Horizons at this point) and that real AI projects are active and funded world wide (as opposed to other suggestions like generation ships or warp drives that have zero active support or funding at this time) I still think an AI extra-solar presence is the most likely scenario. It just might be as close as a human-constructed (or human-like) intelligence may get to leaving the Solar System. The knowledge and experience does the traveling while the weak biological vehicle is left behind.

Our machines are simply tougher than we are, with fewer requirements for ongoing survival and comfort. Pioneer and Voyager are already heading out of the system and can serve as relics to our ingenuity long after people are extinct. They have been followed by other, smarter, longer functioning machines like New Horizons. Even smarter machines with greater longevity will very likely follow New Horizons. If this trend continues and we move into areas like quantum computing to achieve further breakthroughs in computing, an AI arriving in another star system some time in the future is not out of reach.
Not really sure about the necessity of "emotions and personality" aspects you mention. In theory an alien entity could play back the Brandenburg Concerto from one of the Voyager golden records and have an emotional response to it, so even a non-functioning non-AI machine could (theoretically), in a sense, transmit something on an emotional level to another life form.
But we're not really postulating an encounter with aliens here, just some sort of human presence outside the Solar System. I think an AI (in this case) would really only need to be a scientist, not a diplomat. Personality and emotions are usually considered for an AI to make the interface more warm and friendly to humans. I wouldn't see a need for it where the AI is traveling alone to another star system. In that scenario it won't interact with a human or anything else for probably hundreds of thousands of years. Emotions would be detrimental in that situation, I think, consider how bored the poor thing would get. It's primary task would be gathering and relaying information, it doesn't need to be happy or sad to accomplish that.

 

[anorlunda]

Ships filled with zygotes or artificial intelligence don't sound very appealing. I would rather put my money on interstellar communication to transmit the genome or the AI program at light speed to an alien host.

But interstellar light communications are impractical or impossible you say? Ditto for interstellar ships. It would be a simple race in technologies.

 

[ebos]

I'm just thinking about the fuel requirements to keep an acceleration of about 10m/sec^2 (which is 'G' approximately) in order to get even close to relativistic speeds. And you'd have to double that for the deceleration at the other end. The dust problem could be resolved by welding the bumpers from a '56 Cadillac to the front of the ship.

 

[mfb]

Our machines are simply tougher than we are, with fewer requirements for ongoing survival and comfort. Pioneer and Voyager are already heading out of the system and can serve as relics to our ingenuity long after people are extinct. They have been followed by other, smarter, longer functioning machines like New Horizons.

New Horizons is slower than the Voyager probes, and will (probably) not last as long as those. We might even lose contact to New Horizons earlier than contact to the Voyager probes, launched decades earlier.

And you'd have to double that for the deceleration at the other end.

You have to square it. The rocket equation can be cruel.