Debunking Interstellar Travel: Separating Fact from Fiction

[mheslep]

... most PF contributors could be classified in the more favoured set of the population (easy access to a computer and a full education, for a start) so we have a possibly biassed view.

Certainly. Everyone is capable of bias.

...I guess my problem (?) is that, being an Atheist, I do not have the luxury of a belief ...

My point was you placed a strong belief system on display in this thread, that everything *will* go to hell, and that anyone who disagrees is in denial. I only draw your attention to some contrary evidence, and not to a certainty that the unknowable future will be fine.

...I am in the middle of Max Hastings' book on WW2 ("All hell let loose") and, whilst he is clearly biased against some major figures, he produces endless lists of documented examples of inhuman acts, carried out by all sides, en mass. ...

Yes, by some measures the most calamitous event in history. Somewhere in Hastings book there's undoubtedly also some description of millions of people who, despite being far removed from harm, got involved at great cost to put a stop to it all. They won, and though they too were flawed humans, they were not equivalent to the tyrants they defeated.

 

[mheslep]

...
I don't disagree, I think even the fanciful Mars missions being discussed would result in likely death and disaster. However, humans have a tendency to climb into a barrel and ride it off of Niagra falls,

There is the foolish, self-destructive risk, like Russian Roulette, and then there is exploration inspired by an evidenced based theory that entails a considered risk.

 

[nikkkom]

I really don't see the motivation for this project. A very few - either mature or foetal - 'colonists' would be involved.

How did you reach this conclusion about "very few"? Why interstellar ship can't have a crew of 50, 100, 200?

It could never be a rescue exercise for all of us.

It does not have to be.

Exploration in the past was always based on economic factors.

Wrong.

 

[nikkkom]

The attitude in Europe to refugees from the Middle East conflicts shows that most of us are quite happy with the existence of places like the Calais Jungle. and refugee camps elsewhere.

What irritates me about this refugee situation and ME conflicts is that while there are callous people who don't care one iota about horrors somewhere far away, there are also "good people" who nevertheless don't try to understand what's happening, why it is happening, and unwilling to discuss what can be a working solution for this problem. The only thing these "good people" care is to placate their sense of "goodness". "Lets feed and clothe starving and homeless", and let's not figure out how to stop more people from starving and becoming homeless. Good plan. Almost on par with the plan to let entire Africa and ME immigrate into Europe. Evidently, some people think that's the solution.

 

[sophiecentaur]

How did you reach this conclusion about "very few"? Why interstellar ship can't have a crew of 50, 100, 200?
It does not have to be.
Wrong.

I would depend entirely what the terms of the project were. I can't see any point in sending fewer than many (tens of?) thousands of people on such a trip. It would be necessary to have an established community which could regulate itself and be capable of coping with many social problems. Failure of the expedition simply because a squabble amongst a small crew would always be a risk. This, again, shows how the proponents of this sort of scheme are only concerned with nuts and bolts and speeds. The whole project would have to have a 'reason'. It would need to be justified and funded and SOLD to the governments of the World.
In many ways, the practicalities are the least of the problems.

 

[nikkkom]

I would depend entirely what the terms of the project were. I can't see any point in sending fewer than many (tens of?) thousands of people on such a trip. It would be necessary to have an established community which could regulate itself and be capable of coping with many social problems.

Why? Can you try justifying your views and numbers instead of just having an opinion.

Regarding a viable minimal size of a multi-generational community. Before I formulate an opinion, I look for facts. In this case, facts are as follows.

For thousands of years, a typical unit of human society was a tribe. A village. Some 100-1000 people. They existed for hundreds of years, and were usually disrupted by wars / attacks by other human groups (which is not very likely to happen on an interstellar flight), not by internal strife.

Failure of the expedition simply because a squabble amongst a small crew would always be a risk.

True. There are many risks, this one is present too. However, squabble amongst a big crew is also possible. Why do you think it's less likely?

 

[phinds]

For thousands of years, a typical unit of human society was a tribe. A village. Some 100-1000 people. They existed for hundreds of years, and were usually disrupted by wars / attacks by other human groups (which is not very likely to happen on an interstellar flight), not by internal strife.

Uh ... you think maybe things were simpler back then and they didn't need to know the thousands of things that a high tech group will need if they are going to have a viable human ecosystem both on the trip and after arrival?

 

[sophiecentaur]

For thousands of years, a typical unit of human society was a tribe. A village. Some 100-1000 people. They existed for hundreds of years, and were usually disrupted by wars / attacks by other human groups (which is not very likely to happen on an interstellar flight), not by internal strife.

There is very little about this subject that's more than 'opinion' - apart from the Engineering aspects.
The tribal scale of life worked fine when there were many tribes about and if one failed, there would be others beyond the next hill, to continue the race. If the 'colony' is to have good chance of survival (after the investment that's been put into it) then it needs to be able to expand into the new world; hitting the ground running. You can't do that sort of thing on a tribal scale. They will need all kinds of specialists and the capacity for giving a complete education to any children they may have. That is my justification for the big numbers I suggested.
I repeat, this is nothing like Cristopher Columbus or a few intrepid Vikings. Explorations in those days could afford to fail on a regular basis. There was nothing at stake for mankind. Another group would be along in a few decades. And there was always the possibility of going home with a load of goodies. Modern 'Explorers' are not comparable with this. Their purpose is not to do with spreading humans around the planet- they are only self-sufficient for a limited time. Climbing Everest is a pretty irrelevant exercise - except for personal enjoyment. The medical spin-offs from such activities are useful, no doubt. There is no parallel either with Migration or Interstellar exploration.

However, squabble amongst a big crew is also possible. Why do you think it's less likely?

Nothing is impossible but a basically urban sized group would have built in structures; government, infrastructure, a police force, even. For that, you need an appropriate population. The Starship Enterprise situation was well thought out, in that respect. (I would never normally quote Startrek Science on PF but they did get some things right.)
This thread has suffered from not discussing a particular project because we all have different models in mind. Personally, I think it's all too vague to be taken seriously.

 

[mfb]

If a colony ship fails, it is possible to send another colony ship. As long as humans are around and enough of them think it is worth the trip, a single failure does not matter much.

Compared to all the exploration of Earth, we have two advantages:
- we can study the destination in advance. We don't have to hope that there is some island - we know well in advance that there is a planet, its mass, its radiation conditions, its atmospheric composition, potentially its surface chemistry, volcanism and so on.
- we have communication. If a ship sank somewhere in the ocean 200 years ago, no one had any clue what happened - the mission just disappeared. If something happens with an interstellar spacecraft , chances are good they can send back some information about it.

Concerning a minimal viable population: A few hundred in terms of genetics (lower with frozen sperm and/or careful selection of colonists), more would certainly help with passing on knowledge. A lot more can be stored as digital information and learned from there.

 

[mheslep]

...
- we have communication. If a ship sank somewhere in the ocean 200 years ago, no one had any clue what happened - the mission just disappeared. If something happens with an interstellar spacecraft , chances are good they can send back some information about it.

I was thinking the opposite, that the chances of getiing some word from an interstellar colony are likely more difficult than in the age of sail. The age of sail at least had the odd shipwreck survivor, sister ships, and possibly people at the last remote port of call that might tell part the tale. In the interstellar case, first the message takes the time in light years to arrive. Second, the free space path loss (for, say, f=3GHz) for a light year is 365 dB, which requires transmitter power in the terrawatt range.

 

[nikkkom]

There is very little about this subject that's more than 'opinion' - apart from the Engineering aspects.
The tribal scale of life worked fine when there were many tribes about and if one failed, there would be others beyond the next hill, to continue the race. If the 'colony' is to have good chance of survival (after the investment that's been put into it) then it needs to be able to expand into the new world; hitting the ground running. You can't do that sort of thing on a tribal scale.

You are reiterating that it can't be done with less than about 1000 people, without actually giving justification. Repeating something you believe in does not make it true.

You don't need to have specialists in every imaginable profession. For many things, just having recorded knowledge how to do it, how to learn it, is sufficient. For example, you don't need architects or CPU designers on the ship. You don't need them even after it reached the destination. It's okay if only some of the future children grow up and decide to be architects.

 

[|Glitch|]

The only reason I can think of as to why we would send a manned-mission to another star is for the purpose of colonization. In order for that to happen we would first need to find an exoplanet that is a reasonably close match to Earth. With a similar atmospheric composition, an atmospheric pressure that is very close to Earth, and a temperature range that supports liquid water on the surface.

That is asking a great deal. While we do not yet know the atmospheric conditions of the exoplanets we have found thus far, the overwhelming majority of the exoplanets in the 0.75 to 1.50 Earth mass range do not fall within the habitable zone of their star. Finding one that has 78% nitrogen and 21% oxygen with 14.696 psi atmospheric pressure at "sea level" has to be exceedingly rare indeed. We shouldn't forget that Earth would be completely without oxygen if not for the life that developed on early Earth ~3.8 billion years ago. Therefore, for an exoplanet to also have oxygen in its atmosphere it would most likely indicate the existence of life. Since oxygen is highly reactive and will combine with just about anything, in order for molecular oxygen to exist in the atmosphere there would have to be some form of life continuously producing it. If life once existed on an exoplanet and then died out completely, any oxygen that life had produced would have combined with other elements (hydrogen, metals, etc.) and no longer be present in the atmosphere.

There are so many different variations of solar system formations, types of "rocky" exoplanets, atmospheric compositions and pressures, etc., that finding one that could come close to supporting any form of human life would be miraculous indeed. We could search for thousands of years, examining millions of exoplanets, and still never find one that is a reasonably close match to Earth. Yet until such a match is found, it does not seem probably that we would even attempt to send a manned-mission to another star. Assuming we had the technology.

 

[sophiecentaur]

You are reiterating that it can't be done with less than about 1000 people, without actually giving justification. Repeating something you believe in does not make it true.

You don't need to have specialists in every imaginable profession. For many things, just having recorded knowledge how to do it, how to learn it, is sufficient. For example, you don't need architects or CPU designers on the ship. You don't need them even after it reached the destination. It's okay if only some of the future children grow up and decide to be architects.

You forget that the expedition needs to be autonomous and ready to deal with the unexpected, at short notice. You can't claim that a massive information bank can solve all problems as they arrive. Remember, early colonists took experts with them. Too late to learn carpentry when you spring a leak.
Not possible to ring home (as in Apollo) for the solution to a problem.
10LY away and you wait 20y for advice from home. Everyone dies.
In any case, I can't see large scale as an objection.

 

[litup]

There are schemes involving the freezing of ova and sperm and such, basically a robot ship that may take a thousand years to get even to Alpha Centauri and then robots grow new humans after arrival or a few years before and teach those children the history of the human race and they go on to found a colony there.

In the meantime, science catches up and actually does make a faster than light drive and has already gotten a colony started 800 years before the robot ship arrives, hilarity ensues...

 

[Borg]

In the meantime, science catches up and actually does make a faster than light drive and has already gotten a colony started 800 years before the robot ship arrives, hilarity ensues...

Or not.

 

[Rubidium_71]

There is the foolish, self-destructive risk, like Russian Roulette, and then there is exploration inspired by an evidenced based theory that entails a considered risk.

Humans often admire "foolish, self destructive risk" even if it fails. The men who crewed the Hunley submarine in 1864 could certainly have been considered foolish. The vessel had already killed many people, but they accepted the mission anyway. They were successful in destroying the USS Housatonic, but died when the ship was lost during the mission. I've been to the Hunley museum in South Carolina - these men are regarded are heroes, not fools. Even though the Hunley ultimately failed the ship is revered and the technology was improved into the present day.
In my opinion this is one of humanity's strengths - we dare. For good or ill, I can see humans taking on the "crazy" risk of an interstellar journey. Personally, I wouldn't see an interstellar space mission as being comparable to Russian Roulette, with the space mission there's a greater mission and potential reward that might be possible.

 

[mfb]

In the interstellar case, first the message takes the time in light years to arrive. Second, the free space path loss (for, say, f=3GHz) for a light year is 365 dB, which requires transmitter power in the terrawatt range.

A highly directional transmitter doesn't need that much power, especially if you don't need a huge bandwidth.

the overwhelming majority of the exoplanets in the 0.75 to 1.50 Earth mass range do not fall within the habitable zone of their star.

Don't forget observation bias, Kepler is more likely to find planets closer to the stars. Something like 1% to 3% of all stars have "earth analogs" (source), the number gets significantly larger if you include colder planets where fission, fusion, or large-scale solar power can deliver the necessary power, and with exomoons orbiting larger planets. There are 50 stars within ~15 light years, so we expect to have several planets that can support human life (with some artificial heating), and on average one "Earth analog". That does not mean 21% oxygen and 101.3 kPa atmospheric pressure, but that is not necessary.

Since oxygen is highly reactive and will combine with just about anything, in order for molecular oxygen to exist in the atmosphere there would have to be some form of life continuously producing it.

Maybe. Maybe not. Be careful with "impossible" statements.

 

[mheslep]

Humans often admire "foolish, self destructive risk" even if it fails. The men who crewed the Hunley submarine in 1864 could certainly have been considered foolish.

Im not talking about what people ignorant of science and engineering available at the time might think. All the basic science was in place for a crude submarine: Archimedes, Newton, Boyle, the crude materials, pumps, metallergy. One could place on paper a logical, evidence based argument for how the Hunley could work, and from that model roughly predict it's capabilities. Success was one the possible outcomes.

Building a much larger Hunley with the same model and materials, and musing 'hey we sunk the Husatonic, now let's take this rig under the Arctic Ocean ice to the North Pole because we dare', that would be the work of fools, and there would be no museum commemorating the attempt. And I contend taking a hand propelled, hand pumped, blind steerage 19th century vessel to the North Pole had a better chance than an interstellar manned mission with current technology.

It occurs to me I'm spilling a lot of ink trying to illustrate the difference between the bold and the foolish, when the point was classically illustrated long ago.
https://en.m.wikipedia.org/wiki/Icarus#The_legend

 

[mheslep]

... several planets that can support human life (with some artificial heating), ...

How is 'support' defined in this context? Life can be supported on the Moon with sufficient artificial means.

 

[mfb]

'hey we sunk the Husatonic, now let's take this rig under the Arctic Ocean ice to the North Pole because we dare'

Human spaceflight missions so far had a success rate of 98-99%. Comparing that to a submarine that sank is not really fair.

Spoiler

315 launch attempts
- one crew got saved by the launch abort system seconds before the rocket exploded on the pad (Soyuz T-10-1)
- one crew died during launch (Challenger)
313 missions reached orbit and went back to attempt a landing
- one crew died from decompression shortly before entering the atmosphere (Soyuz 11)
- one crew died from disintegration of the vehicle in the atmosphere (Columbia)
- one crew (well, a single person) died on hard impact with the ground (Soyuz 1)
310 missions landed all passengers safely on Earth

4 missions with fatalities, one mission that did not fly, but without fatalities, and if you want to include Apollo 13 then we have one mission which did not reach its intended destination. 4-6 failures in 315 missions.

How is 'support' defined in this context? Life can be supported on the Moon with sufficient artificial means.

The planets mentioned are probably much better than the Moon. More like Mars.

 

[newjerseyrunner]

I disagree, Sir. People already care about their children and grandchildren because they like the idea of their lineage carrying on into the future. If you tell folks their progeny will be part of starting an off world colony, I think there would be interested parties.

I disagree, if something doesn't affect me personally, why would I care? Our children will love on a hot, dry planet, most people don't seem to care. I only care because it affects me: I want to scuba dive the Great Barrier Reef, I don't want terrible wars over water...

 

[Rubidium_71]

I disagree, if something doesn't affect me personally, why would I care? Our children will love on a hot, dry planet, most people don't seem to care.

About their children and grandchildren, yes, people do care. That's why we send children on to college, for example, we want to make sure they have a bright future. If folks truly didn't care about anything except themselves, they wouldn't invest in their kids at all. About distant descendants, people can be indifferent. Perhaps people aren't concerned with climate change ruining the world because they anticipate that there will be some useful solutions developed in the future - like off world colonies (in our own system if not in others).

Im not talking about what people ignorant of science and engineering available at the time might think. All the basic science was in place for a crude submarine: Archimedes, Newton, Boyle, the crude materials, pumps, metallergy. One could place on paper a logical, evidence based argument for how the Hunley could work, and from that model roughly predict it's capabilities. Success was one the possible outcomes.

So, then, it is your position that an interstellar journey is an absolute impossibility? No chance of humanity achieving this goal? One can also show on paper how a generation ship based on current technology could work. There would be a remote chance of success there as well. I guess, given what humanity has achieved in the past, I will give future humans the benefit of the doubt. My mention of the Hunley was not intended to draw a statistical comparison between the success of submarines and the success of space missions (although @mfb's point is certainly valid). I mentioned it to illustrate the human spirit. We dare to attempt feats that are declared impossible all the time, it's a trait that's served humanity well over time. We can split hairs between what is considered foolish or brave all day long, in the end it's up to each individual (or hindsight) to draw that distinction. In that respect I don't find the mention of Icarus particularly useful, since it's fairy tale about flying people with wings made of wax. I do find it amusing that many science fiction stories use Icarus as the name for various interstellar spacecraft (like the Icarus shown in Babylon 5), pointing out the theoretical irony if such a project would ever succeed.

 

[mheslep]

Human spaceflight missions so far had a success rate of 98-99%. Comparing that to a submarine that sank is not really fair.

I didn't. Rather: Attempting an interstellar manned mission with current technology is similar to attempting a North Pole journey in the Hunley.

The planets mentioned are probably much better than the Moon. More like Mars.

So I understand, but in what sense is a lifeless Mars-like planet "better" for interstellar colonists, again, in the context of how such a planet can "support human life". All aspects of life support on Mars still require artificial support - atmosphere, temperature, food, water. Mars-like surface gravity is better for human physiology, though there's a delta-V energy cost to be paid for landing and take off. Also carbon in the Mars-like atmosphere enables production of hydrocarbons (which Musk for instance intends to use to make methane); not sure if the Moon has carbon mineral resources.

 

[mheslep]

..

So, then, it is your position that an interstellar journey is an absolute impossibility?

Several people in the history of aviation, perhaps a dozen, have survived a free fall to the ground from aircraft, some from as high as jet cruise altitude, some 30K feet. I'd place the chances somewhere in there.

And no, I contend neither you nor anyone else can put a plausible model on paper for a generational journey with current technology. To start, a generational ship has to be point and shoot with current propulsion, and nobody knows yet where to point. There is no option to Trek around.

 

[sophiecentaur]

That's why we send children on to college

"We" send our children or those of close family. Do "we" pay for all kids? What would your average member of the public say to a request for College or University fees from a stranger? Same goes for medical fees. I don't think soThe UK used to pay for University Education for anyone who qualified with high enough A Levels grades but the great British public no longer accept that idea. The UK NHS is on the way out and Obamacare was not greeted well by the US either.
Thatcher said there's no such thing as Society and she set in motion the demise of Society. Why would anyone be interested in the fortunes of some faceless individuals who they will never see or hold a conversation with and whose genes are not near enough to be called 'family'?
It's a great bar-room topic, I agree, but can anyone really believe the majority would be prepared to pay?

 

[enorbet]

Regarding the comparison of Space Travel to Early Human Migration, IMHO this is entirely an apples to oranges (flawed) attempt. Ground travel can be viewed in small steps in which each step still has the means for survival close at hand. Water travel is a bit more comparable but at least explorers didn't have to carry their own air, light and heat, etc. Commonly for many generations explorers kept land in sight so that a return to a presumably rich resource environment was all but trivial. In each of these cases, including early ocean travel, it was a given that most expeditions would likely pay for themselves and many would provide vast wealth returns. The risk/benefit ratio was manageable.

It's interesting and fun to speculate on leaving our Solar System but it is way more than not only speculation but exponentially more premature than contemplating transoceanic expeditions with mere rafts. It seems to me that if we start with Moon colonization and develop the means to harvest resources with immediate value (water and titanium come to mind as high market value resources that will only increase in value over time) it is likely that other resources will be discovered, developed, and become marketable, the "fuel" of exploration. Medical value could also become big in a fairly short time. However all this is precluded by technology, specifically lower cost energy to make escape velocity more affordable.

THEN, with that experience and technology "off the shelf", we can rightly contemplate Mars, surely a few generations away from now. Without some major breakthrough in propulsion (to name just one crucial technology) even mining the Asteroid Belt is likely many generations away. The leap from there to even the moons of Jupiter is another huge gulf and, absent advanced robot technology or propulsion breakthroughs, one involving human travel is likely many hundreds of years distant.

Interstellar travel is, IMHO, another exponential quantum leap in both abilities and human need. Perhaps the greatest benefit to such bold exploration has yet to be mentioned - the effect on human organization and thinking due to the need for widespread cooperation.

 

[Rubidium_71]

and nobody knows yet where to point.

You're absolutely right, we do not have a target and without one there certainly is no mission.
Since the thread was asking about an interstellar journey I thought that a theoretical viable destination was part of the basis for the question.

Do "we" pay for all kids?

I don't think I suggested this is or should be the case. All I'm saying is that parents tend to care about the destinies of their children and grandchildren. The question was would people sign up for a generation ship journey if there was no immediate benefit to themselves. Some folks didn't think so, fair enough. I think that having descendants that would eventually have a chance to found an historic offworld colony would be a motivating factor for some people. Maybe a poll would shed some light on the question: we could post a poll question that asked if there was a generation ship being launched to a nearby star, would you sign up even though you knew for sure you would never personally reach the destination? I don't think the YES column would be completely empty.
As far as who would pay for such a mission, if we ever did discover a habitable target world, I think there might be a mobilization of world resources to make such a journey happen at some point. If that was the case I think you would have volunteers, especially if the over population and environmental changes on Earth had gotten worse. There are already wealthy individuals willing to pour money into space based ventures as it is, so I doubt a tax hike would be necessary in those theoretical circumstances. It would depend a lot on the state of the global economy when and if such a discovery was ever made.

 

[Jonathan Scott]

I think it seems possible that technology for "long sleep" (some form of hibernation or suspended animation) would make interstellar journeys more practical, requiring less resources and avoiding the need for a multi-generation ship.

I'd also expect that long before we attempt interstellar travel, mankind would have started setting up colony ships in space, which would then allow a more gradual evolution towards independence from the sun.

 

[sophiecentaur]

this is entirely an apples to oranges (flawed) attempt

Absolutely. Any differences in the technology available cannot make up for the timescale involved. People set of on long voyages of Earth exploration for economic reasons (Everest and Science trips are another matter altogether). Trade, e.g. the 'other way round' to the East were the main spur. Before that, the steps were incremental but still economy - based migration.
A planet would only be worth colonising if it was 'nearly' Earthlike. The less Earth like, the more trouble would be involved and the more time energy would need to be expended - and the time needed. Set that against the massively extra time involved in finding somewhere that's already what is needed. Either way, you are talking in terms of many many generations. As mentioned earlier, who would be at all interested in the success or failure of an expedition that left hundreds of years ago?
The romance of Voyager is built on very shaky ground. People go all woozy about Voyager leaving the Heliopause - taking the message about our culture with it, for the appreciation of little green men. Voyager is really just a bit of deep-space junk and totally irrelevant to anything, despite how important the success of the project was. The recorded human culture was of no use - except for vanity and for stimulating interest in funding the venture.
Basically, I have always had a problem accepting that humans could actually terraform a new planet successfully when they have spent centuries de-terraforming Earth. Homo Spiens is basically a selfish and irresponsible species. (As are the rest of living things)

 

[mfb]

Do "we" pay for all kids?

Via taxes: in many countries "we" do. Same goes for medical fees. The US is one of the rare exceptions of first-world countries where this is not standard.No one suggests to start construction in 2017. "Current technology" in this context means we have an idea how to build things and we had working prototypes already, which means something like TRL 5-6 - a fission reactor is fine, a fusion reactor is not. Of course such a spacecraft would need 20+ years of dedicated development, then a lot of construction work, and you probably want such a spacecraft to fly around in the solar system for at least 10 years to see if that works before it leaves the solar system.