Debunking Interstellar Travel: Separating Fact from Fiction

[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.

 

[Astronuc]

assuming we have the technology

That too is a fantasy. There are only so many ways to achieve propulsion. Somewhere mass must be ejected from an object in order to achieve high velocity. The mass must be carried, and the power (energy production) system my produce considerable power to provide some substantial thrust. Putting such mass in orbit would be rather expensive, and constructing a system from resources on the moon or asteroids would be similarly expensive.

I think there have been scenarios proposed to use the gas planets as jumping off points for interstellar travel, but those are rather fanciful. Infrastructure would need to be in place, and that means colonizing the outer planets in some fashion, i.e., orbiting space stations.

Besides interstellar dust, there is the matter of galactic cosmic radiation.

 

[enorbet]

I truly wish I wasn't forced by logic to be such a wet blanket on this subject but currently there are so many seemingly insurmountable difficulties so far beyond us for which only vast amounts of time (combined with effort) can solve, I can't help but conclude that odds are greatly against ever achieving the most primitive of Interstellar travel, let alone some Star Trek vision.

It seems to me this wiki came from another thread here but I think it useful here since a number of responses depend on human civilization having vast amounts of time to discover new, affordable technologies. If you look at

https://en.wikipedia.org/wiki/Timeline_of_the_far_future#Future_of_humanity

you will see that using The Drake Equation the odds are 95% against human civilization surviving beyond 10K years. We likely don't have even 10s of thousands of years let alone millions or billions. Since mere velocity as we think of it now has very bad odds of making Interstellar travel practical or even possible, the only remaining possibility is some manner of Warp Drive that probably folds spacetime and the likely energy costs of that surely make Interstellar Travel a subject fit for dreamers only. We need dreamers but we are presently so far behind in this area that this is likely the subject of "pipe dreamers" as sad as I am to say it.

 

[mfb]

I truly wish I wasn't forced by logic to be such a wet blanket on this subject but currently there are so many seemingly insurmountable difficulties so far beyond us for which only vast amounts of time (combined with effort) can solve, I can't help but conclude that odds are greatly against ever achieving the most primitive of Interstellar travel

How would you have evaluated the chances to go to Moon in 1900, or heavier-than-air flight in 1800? Both got realized, due to "dreamers".

you will see that using The Drake Equation the odds are 95% against human civilization surviving beyond 10K years

If you apply statistics in a completely wrong way (it is also not the Drake equation). By exactly the same argument, you would have a 5% chance to get 20 times as old as you are today. How realistic is that?

 

[enorbet]

ping mfb - I recognize that it is true that amazing things get accomplished exactly because the people responsible "didn't know it was (nearly) impossible" so I am somewhat at emotional odds within myself posting in this thread because I have no desire to dampen anyone's dreams. That said I will try to answer your questions and not assume they are merely rhetorical.

Allow me to take "heavier-than-air flight in 1800" first. It seems to me that the desire to fly had a serious "leg up" long before 1800 because any fool could see it was theoretically possible since birds, insects and a few mammals did it. All of the basics were in place long before Orville and Wilbur came along. It just took someone with the desire, money and time and an experimental mind to make each small step required to put it all together and achieve flight.

The Moon by 1900 is an order of magnitude more difficult since AFAIK Jules Verne was the most known person to imagine how that could be accomplished yet anyone familiar with Newton could easily prove Man could not withstand the Gs of a cannon. Granted there were fanciful stories of moon travel back as far as ~80 AD and something somewhat resembling a rocket was imagined by Cyrano de Bergerac but by and large they weren't considered serious because most depended on what amounts to magic ie anti-gravity paint, etc. This is not anywhere near as convincing as seeing heavier-than-air things fly every day. So it is likely that I would have bet against flight to the moon in 1900. Thankfully I would have been wrong and I sincerely hope I am wrong about Interstellar Travel as well.

However, it seems to me the progression follows, that Interstellar Travel is currently many orders of magnitude beyond Moon Travel with no examples to follow yet. Also the financial requirements are similarly aligned with the progression of difficulty. Two men could afford a plane. Millions were required for Moon flight. Just how much power must one (or how many men) have at one's disposal (and at what cost?) to generate and control sufficient power to achieve it when we can't even calculate if it is really possible to get to a fraction of c? let alone fold spacetime?

I'm not assuming it is impossible ever... just that presently, given what we know or even can "see", it is far, far beyond our reach even in imagination of anything remotely realistic. I do understand that Drake was lacking in evidence sufficiently to cast doubt on how likely his conclusions can be, making them "best guesstimate" at best. Game changers do occur but until they do we are stuck with what we have, where we are.

If I am overly pessimistic please do enlighten me. I'd welcome the hope.

 

[B Levenson]

The history of the Alcubierre drive is that in 1994, M.A. published his article showing that, with the right metric, you could propel a ship locally slower than light but globally faster, by compressing the space ahead and expanding it behind. In 1997, another article (I forget the authors) said you would need more energy than was available in the universe for this to work. In 1998 or '99, a third article said it could be done with a lot less energy, but you'd need some matter with negative mass, and nobody knows how to produce that or even just what it is. So warp drives are in limbo for the moment.

 

[mfb]

I recognize that it is true that amazing things get accomplished exactly because the people responsible "didn't know it was (nearly) impossible"

Most of the things get done by people knowing exactly that it is "impossible".

1800 didn't have internal combustion engines, 1900 didn't have de Laval nozzles used in rocketry, which are crucial for high exhaust speeds.

A (relatively) slow colony ship doesn't require unknown physics. It requires a lot of engineering, more research in independent habitats and tons of other fields, but all those things are not completely new. They are mainly things we have already, on a much larger scale. Sure, cost is a huge issue, but if that is the only issue, things tend to get done over time.

 

[newjerseyrunner]

I think the analogy about heavier than air travel in the 1800s vs FTL travel now is invalid because in the 1800s, they didn't know how to do it mechanically, but they understood how to do it mathematically since the publication of the Principia: f = ma, if you push against the air harder than the Earth pulls you back, you'll fly, any science-literate person would have known that, it was only considered impossible then by the ignorant masses. FTL travel violates causality, and it's the scientists who believe that it's impossible.

I also agree that FTL travel is not required to colonize. Species that travel through space will continue to find more efficient ways of doing it, and for a colonizing species. Colonists tend to be a one way trip anyway so time is of little consequence, especially if you can be put in stasis during the flight. If you're leaving your planet behind for some reason, would you care if you were put to sleep for 4 years, 40 years, 4 thousand, 4 million? It'd be instantaneous to you.

 

[GeorgeDishman]

It seems to me that nobody would set out on a voyage to another star system without first being sure that there was a habitable planet there. That means sending unmanned probes first (and the problems in doing that are quite different from those in the article). If you have succeeded in getting an autonomous probe gravitationally captured by the target system, then soft-landed on the planet, then received its analysis saying that the flora and fauna are suitable, all you need is to have some form of 3D biological reconstruction system on the probe, a "teleport" receiver in a sense, and you can be scanned here and rebuilt there with the only delay being highly robust data communication at the speed of light. That sort of technology is currently in its infancy but there is huge financial potential in the medical industry so it will certainly develop. The idea of sending manned ships will be laughably obsolete long before it becomes feasible, but that doesn't mean interstellar travel won't happen.

https://en.wikipedia.org/wiki/3D_bioprinting

 

[nikkkom]

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.

Please do not be fixated at 1g acceleration (or any other fixed number). It is unimportant.

In fact, gentler acceleration in many cases is better. Say, if you have a fusion-powered engine, you probably need to carry a lot of deuterium. Deuterium is bulky. With gentler acceleration, your engine is smaller and lighter, and your tanks are less sturdy and therefore lighter, therefore mass fraction is better.

If you plan on a 100 year journey at 0.05c, you can accelerate at just 0.01g and it still takes only 5 years, a small fraction out of total flight time, to attain your cruise speed.

 

[ebos]

Please do not be fixated at 1g acceleration (or any other fixed number). It is unimportant.

In fact, gentler acceleration in many cases is better. Say, if you have a fusion-powered engine, you probably need to carry a lot of deuterium. Deuterium is bulky. With gentler acceleration, your engine is smaller and lighter, and your tanks are less sturdy and therefore lighter, therefore mass fraction is better.

If you plan on a 100 year journey at 0.05c, you can accelerate at just 0.01g and it still takes only 5 years, a small fraction out of total flight time, to attain your cruise speed.

True, but the humans on board will have turned to Jello.