Debunking Interstellar Travel: Separating Fact from Fiction

[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.

 

[nikkkom]

What are you talking about?

 

[mfb]

The conclusion about the fuel needed is independent of the acceleration, it only depends on the final speed (and engineering details).

1g is convenient because you don't need other methods to produce artificial gravity then.

 

[phinds]

What are you talking about?

He is talking about the fact that in free fall or microgravity for many many many years, human muscles will atrophy to uselessness and bones will have serious problems as well. Kelly's recent year in space will provide more hard data on that but I believe it is inescapable that the human body cannot sustain year and years of free fall or micro-gravity.

 

[mfb]

Valeri Polyakov spend 437 days in space, Sergei Avdeyev 380 days, Vladimir Titov and Musa Manarov both 365 days in a joint mission.
Mikhail Korniyenko and Scott Kelly with 340 days are just rank 5/6.
Valeri Polyakov appears again in this list on rank 9, 240 days a few years before his record-length spaceflight.
All numbers are for a single continuous mission, of course.
Full list

Artificial gravity on a spacecraft is not magic. We simply don't have it because it is not necessary for current mission profiles.

 

[DrStupid]

He is talking about the fact that in free fall or microgravity for many many many years, human muscles will atrophy to uselessness and bones will have serious problems as well.

For the very unlikely case that we will be able to build interstellar ships but not to adapt humans to microgravity we can simulate gravity with rotating habitats.

 

[phinds]

For the very unlikely case that we will be able to build interstellar ships but not to adapt humans to microgravity we can simulate gravity with rotating habitats.

Of course but that severely complicates the design. It IS "just" an engineering challange but could be done. I was simply responding to a specific question.

 

[DrStupid]

but that severely complicates the design

Simulated gravity is not even a minor challenge compared to other problems to be solved for an interstellar spaceship. We could easily do that with current technology.

 

[1oldman2]

For the very unlikely case that we will be able to build interstellar ships but not to adapt humans to microgravity we can simulate gravity with rotating habitats.

Like in 2001 a space odyssey ?

 

[DrStupid]

Like in 2001 a space odyssey ?

No, with a cable and a counterweight.

 

[1oldman2]

No, with a cable and a counterweight.

That would also work, I kind of liked the doughnut approach VS. the nunchuck effect but there are many different ways to approach the artificial gravity question. That is a very minor issue compared to the other problems mentioned.

 

[ebos]

I remember reading the Foundation and Empire series by Isaac Asimov (still my favorite sci-fi book just ahead of Heinlein's A Time For Love) and one of the main quests throughout the plot was to discover who the "Master Race" was. They were the ones who controlled basically everything and everyone in the galaxy while still keeping it a peaceful place . Spoiler alert, but when they were finally discovered they were a civilization of peasant who lived in small humble homes, grew their own vegetables and never fought. Kind of like a planet full of Mahatmas.
In other words, we just got down from the trees not too long ago. We have a long time to go. Even the Sun has at least 4 billion years left. Why don't we forget about outer space for now. Our technology has a lot to learn before we go way out there and/or try to colonize. We still haven't learned from any of the mistakes from our past yet. Look at the US this year and last. And we want to send that out to space? Let's slow down. Most of the new inventions we celebrate these days is usually just ego-driven anyways. Or it tries to fill a bottom-less hole in our hearts. Nothing wrong with keeping a hand in. Good telescopes and other powerful sensory devices are OK for now. But most of our energy needs to be spent right here learning about universal love, about not jumping to hatred or war at the least provocation, learning how to feed everyone, making sure everyone has enough instead of just 1%.. My goodness, I would turn down any ship that was fully guaranteed to go to a proven inhabited star if I was asked today because I would be too embarrassed when I got there. Or worse, when they got here.

 

[1oldman2]

And we want to send that out to space? Let's slow down.

Wow, great taste in authors and common sense. I wish they would allow more than one like per post, you would get your fair share from me.

 

[nikkkom]

Our technology has a lot to learn before we go way out there and/or try to colonize. We still haven't learned from any of the mistakes from our past yet. Look at the US this year and last. And we want to send that out to space? Let's slow down. Most of the new inventions we celebrate these days is usually just ego-driven anyways.

We still haven't learned from any of the mistakes? Really?

We (humanity) invented, after several iterations, more efficient systems of government. Namely, we removed from power people who would keep population superstitious and uneducated, suppress science just in order to cling to power. We removed from power people who pass their ruling position to their children, with no regard to their ability to rule well. We made it illegal to seize power for life (term limits). We made it illegal to suppress dissenting opinions (freedom of press). Etc etc etc.

We understood that environment should be protected, and all our activities (industrial and domestic) need to limit its damage to environment. No more uncontrolled discharge of nasty stuff into the rivers.

Scientific and engineering advances we made... I can't list even most important of those here, that would require several pages. And we are not showing any sign of slowing down.

 

[rootone]

We still haven't learned from any of the mistakes? Really?

We (humanity) invented, after several iterations, more efficient systems of government. Namely, we removed from power people who would keep population superstitious and uneducated, suppress science just in order to cling to power. We removed from power people who pass their ruling position to their children, with no regard to their ability to rule well. We made it illegal to seize power for life (term limits). We made it illegal to suppress dissenting opinions (freedom of press). Etc etc etc.

We understood that environment should be protected, and all our activities (industrial and domestic) need to limit its damage to environment. No more uncontrolled discharge of nasty stuff into the rivers.

Scientific and engineering advances we made... I can't list even most important of those here, that would require several pages. And we are not showing any sign of slowing down.

I admire your optimism.

 

[Drakkith]

I admire your optimism.

Yes, it's a nice change from the pessimism so many people have.

Why don't we forget about outer space for now.

I can think of at least one reason. Having the ability to save our species from extinction in the event of a global catastrophe, whether man-made or natural. I'm sure there are plenty of others.

We still haven't learned from any of the mistakes from our past yet. Look at the US this year and last. And we want to send that out to space? Let's slow down. Most of the new inventions we celebrate these days is usually just ego-driven anyways. Or it tries to fill a bottom-less hole in our hearts. Nothing wrong with keeping a hand in. Good telescopes and other powerful sensory devices are OK for now. But most of our energy needs to be spent right here learning about universal love, about not jumping to hatred or war at the least provocation, learning how to feed everyone, making sure everyone has enough instead of just 1%.

In my opinion you're operating under the assumption that if we just spend more time and effort we'll overcome all of those difficulties. That may not be true. We could very well never solve them. In addition, I doubt you could ever get everyone to agree on what "universal love" even means, or which system of government and/or economics is best for everyone.

 

[DrStupid]

Look at the US this year and last. And we want to send that out to space?

Look at the US and the Russians in cold war. Did they sent that into space? Manned spaceflight originally was a side product of intercontinental nuclear weapons and only intended to demonstrate technological superiority. But once in space the super powers started to cooperate there (e.g. with the Apollo-Soyuz Test Project). Things on Earth and in Space will always be different.

But most of our energy needs to be spent right here learning about universal love, about not jumping to hatred or war at the least provocation, learning how to feed everyone, making sure everyone has enough instead of just 1%.

Changing the nature of humans is problematic from an ethical point of view - even when done for the best. Preventing humans from "jumping to hatred or war at the least provocation" would require general mental modifications. There is no doubt that humans will be modified both physically and mentally in the future - especially if we colonise space. But that will happen for a minority only and it will result in additional problems (e.g. conflicts between different post-human species).

Solving our problems on Earth first is a popular idea but out of touch with reality. There will always be problems.

 

[anorlunda]

There's another assumption beneath all this fantasy-full discussion of future advancements. Namely that evolution stops with homo sapiens.

If we are projecting thousands or millions of years into the future, then any inhabitants of Earth will presumably be a post-human species.

Listening to some, machines or AI will be the successor, and darn soon.

Think of Kurzweil's "The Singularity is Near" (He says the year is 2043).

Think of Arthur Clarke's classic story, Childhood's End, where he portrays biological evolution (rather than Kurzweil's AI evolution), but leading the the same end result as Kurzweil's.

Think also of the recent doomsaying by Bill Gates, Elton Musk, and Stephen Hawking on the same subject saying that we should fear AI.

I like to think of software advancements as just the next step in evolution, and to think of the Gates/Musk/Hawking types as just a new flavor of Creationists, who believe that homo sapiens should be immune to being overtaken, that the status quo is sacred, and that evolution is constrained to DNA driven biological processes.

So, if we want to discuss Interstellar travel by humans, shouldn't we confine the discussion to the next 2043-2016 = 27 years.

 

[1oldman2]

So, if we want to discuss Interstellar travel by humans, shouldn't we confine the discussion to the next 2043-2016 = 27 years.

A point well taken, your post is likely the most relevant "interstellar travel" concept mentioned thus far.

 

[nikkkom]

But most of our energy needs to be spent right here learning about universal love, about not jumping to hatred or war at the least provocation, learning how to feed everyone, making sure everyone has enough instead of just 1%.

I find it questionable to have "universal love", whatever that is. People sometimes behave aggressive and even go to war not because they are inherently evil. They do it because it is an *evolutionary necessity*. "Fight or flight". Both reactions make sense. If you see a rockfall upon you, it makes sense to flee. But someone who always runs from any danger, loses. If you run away, you lose everything you left behind - stockpiled food, shelter, territory, children.

We don't need to stop fighting. We need to stop fighting *when it can be avoided with diplomacy, economic pressure, etc*. When we do fight, we need to do it cleverly, not letting our natural animalistic emotions turn the conflict into slaughter.

As to "learning how to feed everyone", I don't see starving people in Western countries. If anything, *obesity* is a problem here, not starvation. "Making sure everyone has enough instead of just 1%"? What is "enough"? Having food, shelter, and health care is enough? I am not in richest 1%, and I have all of that, and much more. Looks like these two problems are solved.

 

[1oldman2]

We seem to be wandering away from the main thread topic and more towards current events.