Interstellar Flight: Adapting Humans for Space

by Paul Gilster on February 8, 2013

It’s surprising but gratifying that we can now talk about the ‘interstellar community.’ Just a few years back, there were many scientists and engineers studying the problems of starflight in their spare time, but when they met, it was at conferences dedicated to other subjects. The fact that the momentum has begun to grow is made clear by the explicitly interstellar conferences of recent memory, from the two 100 Year Starship symposia to the second Tennessee Valley Interstellar Workshop. Icarus Interstellar is mounting a conference this August in Dallas, and the Institute for Interstellar Studies plans its own gathering this fall in London.

HSV Rocket

Of course the Internet is a big part of the picture — Bob Forward and his colleagues could use the telephone and the postal service to keep in touch, but the energizing power of instant document exchange and online discussion was in the future. All this was apparent in Huntsville for the Tennessee Valley event, from which I have just returned. There was an active Twitter channel open and video streaming of the talks, and although I had little time to answer them, I was getting emails from many interested parties who couldn’t attend. Getting copies of papers and presentations after the conference closed can be managed in hours on the Net.

Starflight challenges not only everything we know about propulsion but also our understanding of human nature. If we are seriously considering human travel to such distant destinations, we are looking at decades of travel time at a bare minimum, or the possibility of a generation ship in which people live their lives entirely aboard the craft, which could take hundreds or even thousands of years to reach its destination. Astronaut Jan Davis, who gave the keynote in Huntsville, talked about the various problems of even short duration spaceflight based on her own experience of multiple Shuttle missions.

Image: Rockets dominate the Huntsville skyline in this shot I took from the Calhoun Community College on the final night of the workshop.

Some of these issues are well identified, including the lack of privacy and the loss of muscle and bone mass due to prolonged weightlessness. The privacy issue balances oddly with a sense of isolation, Davis said, as you are cut off from all aspects of your normal life. “You hear a lot of voices, but they’re not the voices you take for granted every day. I missed my dog. I missed sounds like wind, waves hitting the shore. You’re busy, but you’re also isolated.” As medical officer on her two flights, Davis trained on emergency procedures in case a crewmember became incapacitated. The main issue was to stabilize a patient long enough that he or she could be swiftly returned to Earth.

The conclusion from all this is that humans are adapted for Earth, not space, yet they have key advantages over robotic systems, including the ability to discern, judge and learn on a fine-grained basis. Swiftly changing conditions in an on-board experiment she was managing led Davis to alter the schedule on the fly, making changes that would have been difficult for the current generation of robotics. The astronaut sees a combination of the two paradigms as the most likely possibility for long-term missions, perhaps aided by medical breakthroughs in hibernation that would allow the crew to spend most of a long mission in stasis while automatic systems ran the ship.

Robert Hampson (Wake Forest University) extended thinking in this direction by talking about what we need to learn about the human brain before we can contemplate long-duration spaceflight with an interstellar reach. Hampson is an associate professor of physiology and pharmacology with a passion for neuroscience and biology. Given what we know today about risk factors like stroke, epilepsy and Alzheimer’s disease, he notes that if we launch 100 people on a 100 year journey, 25 of them will be incapacitated by the time they arrive even if we can extend their lifetimes significantly. Interstellar flight, then, demands that we learn to predict and prevent degenerative diseases, keeping the brain healthy through entertainment and intellectual stimulation.

One way to do that is with a direct human/machine interface, a kind of TiVo wired into the brain. Hampson told the audience that to fix the brain for long-duration spaceflight, we have to find a way to interface with it, and that means we have to understand its language and coding. It’s a challenge that demands the help not just of the medical community but of mathematicians, physicists and engineers. As to the hibernation that Jan Davis talked about, Hampson asks how much we know about brain activity during hibernation. Is an astronaut under hibernation for fifty years going to have a fifty-year long dream?

I’m jumping around in the schedule here to tie thematic ends together, so I’ll add that my own talk, called “Slow Boat to Centauri,” got into long-duration mode by discussing worldships and how they could sustain themselves along the way. The idea was to show how many resources are available between the stars, suggesting as many space researchers have that our expansion might not involve a direct mission to another star, but rather a step-by-step progression of colonies that gradually moves the human sphere outward. Gradual exploration like this might take thousands of years.

mann_worldship

We can all hope for fast propulsion, but suppose the engineering is intractable. Would we still go to the stars if limited to speeds much less than ten percent of c? One-tenth of one percent of lightspeed gets you to Alpha Centauri in about 4300 years, which is also (very roughly) the extent of human history in terms of recoverable documents and written language. A worldship moving at this speed, in other words, recapitulates the human historical experience aboard a craft that would have to be engineered to be a living world, a vast O’Neill cylinder with propulsion.

The right kind of worldship — and Gordon Woodcock (L5 Society) worked through the engineering problems of creating such a vessel in a first-day talk — would have to be one large enough to sustain a population of thousands in conditions that were eminently livable, the complete antithesis of the cramped quarters Jan Davis experienced aboard the Shuttle. We’re all on a worldship of our own, following our star in its 230 million year journey at 220 kilometers per second around the galaxy, so perhaps a livable worldship engineered by the future Kardashev type 1 civilization we hope to grow into would be an acceptable interstellar ark.

Image: A worldship designed to hold generations of humans, as imagined by space artist Adrian Mann.

Putting the speed issue in perspective, one tenth of one percent of the speed of light is 300 kilometers per second, compared to the 17 kilometers per second that our fastest deep space probe, Voyager 1, has attained. There are ways of moving that fast that we can calculate today, but the engineering needed to produce a worldship — and the vast issues raised by creating a closed-loop ecology aboard the craft — demand a multi-disciplinary approach that takes us into biology, philosophy, sociology and the humanities as well as physics. The long-term perspective needed for such thinking was frequently discussed in Huntsville, about which more on Monday.

tzf_img_post

Greg February 8, 2013 at 12:37

I would be curious, In the case of interstellar travel, which would be a more workable solution, rapid interstellar travel or vastly extended lifespans (thousands of years)? From an engineering stand point it would be rapid interstellar travel but my guess is for the average person, vastly extended lifespans would be.

James D. Stilwell February 8, 2013 at 13:27

I imagine mentioning Star Trek’s “Q” is totally unfair…..
But it might come about sooner than 10% light travel to Altair 4….
Your energy is evidently boundless….
More than astonishing….

jkittle February 8, 2013 at 14:34

First of all… great topic for this board.
I notice that the shortest mission duration is probably about 50 years if some exxxtreme engineering challenges including harnessing fusion energy, are overcome. given we will not likely send adolescents, we are thus committed to sending people who will grow old. I think the challenges of medicine are therefore just as important as the challenges of the engineering, Life extension ot 120 year seems possible by finding people with good genetic and providing advanced life extension treatment.
can we send people on a a one way mission and have them be able to perform significant tasks worthy of their sacrifice?
finally the life extension methods ( if they are practical) are certain to be attempted as part of the regular track that our medical science seems to be on. Priorities in pharmaceutical development are now preventing dementia and maintaining good circulatory and immune system health. These are studies in opposites as neurons are very long lived cells where circulatory systems are all about cells that are constantly replenished. the problems of the immune system feature both a population of short lived cells and a population of long lived cells ( immune memory cells) . finally the problem of cancer and cell repair and replacement are even more difficult in Space where the radiation environment and perhaps the life support system is not optimal.

Dan Ibekwe February 8, 2013 at 17:40

Surely we are talking about a worldship even for a ‘fast’ 50-100 year mission. It’s hardly feasible to ask anyone to stay sane and functional spending that length of time in a confined indoor environment. Perhaps there’s a twin-track approach, developing stable long-term space arcologies to research and exploit the Solar System, while using robot interstellar probes to perfect propulsion and navigation techniques, combining the two at some future date.

Astronist February 8, 2013 at 18:06

As I argued recently in JBIS, I don’t find the idea of a fast crossing with a small astronaut crew to be credible, absent a magical propulsion system. But then I’m not in such a great hurry to get there as some people seem to be. So I think you’re right to focus on the area where speeds are less than 1% of c.

And I look forward to your further report on the long-term thinking at Huntsville. My prediction would be that people were recognising that the problems of creating closed sustainable multi-generational life-support systems in space will have been solved by extensive space colonisation within our own Solar System long before the first manned interstellar vehicle is ready to depart.

Stephen

Stanley Clark February 8, 2013 at 19:23

Couple of questions:
Doesn’t ‘cold sleep’ produce the same effects as zero g, loss of muscle and bone mass?
and at what point does acceleration offset the effects of zero g, 0.1g, 0.2g, 0.3g?

Has anyone considered, sending DNA and cloning humans near the end of the voyage, with machines to train the clones.

Joy February 8, 2013 at 21:26

Many of the social problems of the worldahip will first have to be solved on our population seven billion plus world. What is an appropriate economic system for a static population with a static material and energy base? What is the appropriate fraction of a worker’s life to be spent in funded retirement? (Trick question, y’all know the answer to that one) Is it desirable for all social castes to have extended lifespans?

An argument could be made for caste speciation. The worker caste would be considered mature at aged 15, sterilized no later than aged 30, and euthanized at aged 45. Workers would be good for reactor servicing and work in vacuum. They would only receive rudimentary medical care and work until their scheduled termination date. Accidental deaths of workers would not be a problem. Breeding the workers from populations with poor impulse control, inability to delay gratification, and addictive personalities would make them easier to control.

The ruling caste could likely have life expectancy extended to 180 with near term advancements in biotechnology. Despite any social taboos, they would be likely to exploit the workers sexually. Therefore, there would have to be a genetic barrier to crossbreeding. Half caste workers would destabilize the whole system. The workers would be under complete electronic surveillance at all times. Troublemakers would end up on the compost heap. Upon arrival and colonization, the worker caste would do all of the heavy lifting and take the heavy casualties.

Repellent as the concept is, this is the social system already under construction today. Huxley was only writing about the sort of ideas he heard the movers and shakers talking about at his private clubs. Orwell was just telling us how the BBC actually worked. I wonder what horsemeat lasagna with toxic chemicals is called in ingsoc, maybe Tesco double plus good?

Josh Haigh February 8, 2013 at 22:01

The idea of generational ships to the stars is always given as the backup option – well, if none of the fast ideas work, I guess we’ll just have to go with the multigenerational ships. My question is, just how hard will it be to get one of these monsters up to speed? What will it take? I’m guessing that it wont be that much easier to send something massive at a relatively low speed than it would be to send something very light at high speed?

Wojciech J February 9, 2013 at 10:31

If the travel time between Sol System and destination would be within 50-60 years, the generation spaceships instead of several generations would just house two. With the first one still alive at the point of destination.
Interesting scenario, so far I remember only Alastair Reynolds covering it Revelation Space.
Of course have two-generation spaceship creates a different situation from a one where several ones are alive.
Still I believe that by the time our civilization will be able to build such ships(if we come to such point), virtual reality and extended lifespans will be solution(if the travelers will be biological at all).

Alex Tolley February 9, 2013 at 12:57

@Stanley – you raise an good question with regards the effects of extended cold sleep on physiological effects. However the low temperatures needed reduce metabolism so that these effects are extremely reduced too.

As regards cloning – yes that has been well argued. The problem is that we would need advanced AIs and robots as human substitutes to raise the children, even assuming we have the biology of cloning and artificial wombs solved by them. IMO, if we have such AI’s, why do we need to add humans to the exploration/colonization team?

Brett Bellmore February 9, 2013 at 13:20

“Doesn’t ‘cold sleep’ produce the same effects as zero g, loss of muscle and bone mass?”

That’s kind of hard to say, when the longest application of “cold sleep” to humans I’m aware of is surgical hypothermia, and only lasts a matter of hours.

Actual hibernation in other species only lasts months. I really don’t see much prospect of “cold sleep” as induced hibernation lasting long enough for an interstellar journey. “Cold sleep” would have to be something closer to cryonics to be sufficient for interstellar travel, and there’d be no reason to expect any kind of deconditioning during that, although a recovery period might be necessary after coming out of it.

Brasidas February 9, 2013 at 14:27

For the slow boat option (>1k years to extra-solar destination), the craft would necessarily be designed for an indefinite lifetime. I can’t imagine storing any resources, be it fuel, air, water, etc. that could last that length of time. Even if you planned to keep makeup quantities to account for slow consumption or losses, the likelihood of an accident, collision, undetected leak, or other catastrophic upset depleting the stores, over a timespan of thousands of years, would be very high. You can only flout Murphy’s law for so long. It would seem that the ship would need some capacity to live off the land. Perhaps a scoop similar to the Bussard ram jet concept? Exept the interstellar gas and dust sucked in would be used as makeup mass for fuel, water, oxygen, carbon, and whatever else was needed?

Given this sceario, the worldship would not necesarily need to land anywhere, and therefore, why would it? Would such a structure even need a destination? Or, once reaching its destination, would it’s inhabitants bother to stop?

One other question about the slow boat approach, wouldn’t the ship itself slowly degrade over time, from random collisions, cosmic rays, etc? Even at a slow pace, with melennial time frames, it seems even a thick hull would slowly ablate away, leading to leaks or structural failure. The ship would need some mechanism for renewing the hull and other parts, which might require a large amount of mass. Perhaps this would be the reason they might eventiually need to stop?

David J February 9, 2013 at 14:53

@ Joy “An argument could be made for caste speciation … Repellent as the concept is, this is the social system already under construction today”

Joy, you paint a bleak and dystopic picture, and it can be all too easy to become demotivated in the current sociopolitical environment. But I see the opportunities for space colonization in exactly the opposite light – similar to how the early colonies of the United States were able to cast off an oppressive yoke in settling new lands, the colonization of other planets (around our own and nearby stellar systems) may ultimately allow groups of individuals to freely associate in new lands and create new, more free political arrangements. Imagine the possibilities alone just from terraforming Mars .. within a few hundred years, we could well have regular flights of hundreds of people at a time to the “Ellis Island of Mars”. And if we can find even, say, a few dozen inhabitable planets within 100 light years of us, oppressed people could attain freedom in colonizing these someday. There’s no rational reason to impose artificial limitations on anyone.

“What is an appropriate economic system for a static population with a static material and energy base?”

We don’t really have a ‘static’ energy base – we have a practically unlimited energy base, e.g. in the form of a massive star that we orbit (and I don’t necessarily just mean conventional terrestrial solar power, although the potential there alone is quite vast … within 100 years, we’ll have the technology to automate the construction of gigantic solar farms – even possibly on other planets and moons!). Materials are also basically unlimited – the universe is big, with lots of ‘stuff’ everywhere, and all we need is a bit of human ingenuity to harness both energy and materials. I mean, we already, seemingly, stand at the verge of commercial asteroid mining – the technology is basically there for it today.

If you believe that energy and material resources are highly limited, then it will become a self-fulfilling prophecy. But it’s ultimately not a rational belief, it does not square with our observations of potential abundance around us.

J-C February 9, 2013 at 15:51

I think you are probably correct in writing we will likely progress outward at a gradually expanding sphere – taking small interstellar bites, interstellar baby steps rather than undertaking a direct mission to another star. When you look back in history, especially the colonization of the Western Hemisphere, that is certainly how we progressed and moved forward. From the Vikings to the Spaniards, French, and English, it took decades and centuries to fully open up and colonize this Hemisphere. It seems logical to me that we will first open up the inner solar system, use those resources to move outward to the outer solar system, eventually getting comfortable with distances out to 50,000 AU or more in the Oort Cloud and beyond. From there, things would start to look a bit closer. It will take much longer than a direct mission would but we will need that time to figure out how to protect ourselves from the interstellar medium, how to survive. These are such exciting times we are living in – to be at the cusp of humanities push into space – I wish I could live 1000 years to see it all.

Astronist February 9, 2013 at 15:56

Joy, here is the link to the upcoming BIS conference on the sort of questions you raise:
http://www.bis-space.com/2012/10/17/7183/extraterrestrial-liberty-what-is-freedom-beyond-the-earth

You talk about a static population with a static material and energy base, but I suggest that will not be achieved for some thousands of years yet. So long as Earth has two-way economic and cultural relationships with the rest of the Solar System, it will be an integral part of a growing economy well into the starship era, just as cities like London and Rotterdam have been for centuries part of a growing world economy.

Stephen

Rob Henry February 9, 2013 at 21:20

Wow Joy, you could have hardly put that last comment of yours less diplomatically, but I liked its lack of orthodoxy. It reminds me of Gregory Benford’s suggestion that the main cause of aging was antagonistic pleiotropy, and that that would likely synchronise the life expectancies of the progenitor species of ETI’s to similar and inconveniently low values wrt interstellar travel.

Of cause, this could only ever work to synchronise their natural values, not their eventual augmented values, but it also brings up the following problem. Each such gene that you suppress to increase longevity, slightly decreases vigour in earlier life. If you want your child to be an Olympic athlete or sporting representative, you want those gene turned on. Since society invariably worships sportsmen and women, not academics, many will take the sporting choice for their children, and many of those children will make no attempt to alleviate that choice through medication.

In short, I also think that there will be a cast difference, but for less gloomy reasons than you posit. I also think that it is a near certainty that the life expectancy of the academic class will almost certainly be over 150 and that it will probably be over 200, so a 100 year travel time for the most extreme enthusiasts will present no problems of itself. Longer journey times than this will face the prospect of being beaten to the destination by later faster starships, so are nonstarters anyway.

NS February 10, 2013 at 0:20

“Has anyone considered, sending DNA and cloning humans near the end of the voyage, with machines to train the clones.”

Are you a parent? Would you subject your child to an environment like that?

ljk February 10, 2013 at 0:23

Excellent and cognizant points as usual, Joy. By those parameters, we might as well just send mindless machines as our starship “crew”.

A mantra I have said before and will say again:

Robots are for exploration. Humans are for colonization.

The two will always work together to mutual benefit and goals, but that should be the underlying basis for why the two parties are in space in the first place.

Larry F February 10, 2013 at 4:46

Colonizing uninhabited ‘alternate’ Earth’s in other dimensional universes of the multiverse, might be easier than overcoming the many hurdles associated with interstellar travel. We need a Multiverse Exploration Agency to investigate it. Especially if NASA fails to produce a viable ‘warp drive’.

Michael Spencer February 10, 2013 at 9:42

Alastair Reynolds has written about a future where humanity has evolved itself into forms needed to cope with long interstellar voyages in a universe that includes the ‘Ultras’ who manage the ‘light huggers’ sleek, kilometer-long machines traveling at just below the speed of light and powered by mysterious engines contrived by the ‘Conjoiners’ who learned how to channel the inferno of a remote supernova into a starship engine.

The man has no limit to his imagination. And then there’s John Scalzi, imagining a human engineered to live in space and appearing to look like a piece of space rock, fully self-contained.

What a world.

Tarmen February 10, 2013 at 11:00

Ark ships, the subject of many sci fi books. Certainly the best laid plans will go awry. But the thing about ark ships, is that they themselves are a living colony. Even if they get “lost in space” and forget where they are going or where they started, they are still alive. Peoples of the 7 billion Earth would feel a great satisfaction if they would send even one ark fully loaded, 2 of each animal and an ecology to last as long as it takes. It would be like a father seeing his son move out and start his own career. “Stay in touch, son.”
Many arks would be a better insurance that at least one would reproduce at some faraway wet planet and provide “grandkids”.

David C February 10, 2013 at 14:13

Let’s consider a voyage that takes a couple of thousand years. The solutions will be a) multi-generational, b) vast extension of life-span, c) some kind of hibernation… or a combo of two or more of these.

Whatever the method, consider this:

If the destination is known to be a life-friendly planet (good air, good water, etc) then the occupants of the multi-thousand-year-voyage ship will almost certainly be greeted by… Earthlings! In all those thousands of years, we will have almost certainly far surpassed our own initial star-flight capabilities.

With that in mind, who would ever sign up for a multi-thousand year flight? It seems doomed to anti-climactic disappointment from the outset.

Alex Tolley February 10, 2013 at 14:16

“Worldships” are romantic devices, conjuring up Elysian conditions as depicted for the O’Neill’s. In reality, I would expect them to be compact, automated systems with the human crew living in cubicles “enjoying” VR simulation lives.

Given the likely earliest date of a star ship launch, either we will have advanced AIs that can out compete a human, or we will know that they cannot be built. I suspect the former case is more probable. In which case, star ships will be “crewed” with machines, not humans.

The AI scenario does not preclude humans from going to the stars, but it seems more likely machines will make the journey, and humans will be created at the destination.

But all our concerns about terra-forming, biological contamination (prime directive) and biological competition rather disappear if machines colonize the stars, rather than humans. But I can also imagine million year terra-forming efforts by machines on dead worlds that are aimed to become new human worlds.

If we do try star traveling world ships – I assume after they are abundant in the solar system – just how big and robust must they be to survive thousands of years of human habitation? I suspect that they would have to consist of isolated systems so that if one part biologically or socially failed, it could be recolonized from another part. And at this point, we haven’t even discussed the energy requirements to accelerate and decelerate the ship.

David Joffe February 10, 2013 at 14:56

I just came across your blog (as someone interested in
interplanetary and interstellar travel) – looks interesting, have
‘bookmarked’ it.

From your ‘about’: “Nursing the kind of long-term thinking that
might build an interstellar probe — and the cultural imperative of
passing along things of value to the future — is a key theme in all
my work”

I fully endorse this, but just a small comment, though I’m 100% sure
you’ve already thought about this – if we do cure aging someday (and
I am relatively optimistic that we will, before 2100), then a lot of
these ‘huge, long-term’ projects take on a whole different hue …
they become not necessarily just ‘inter-generational’, but
potentially more accessible on an individual level. A manned space
trip of 100 or 200 years seems less long somehow if your lifespan
is, say, 500 or 100 years. Even mega-projects like e.g. terraforming
Mars take on a different hue.

I think evolution ultimately must select for space-faring species
(e.g. if the dinosaurs had terraformed and colonized Mars, they’d
probably still be alive today), and we should keep in mind we’ve had
hundreds of thousands of years as a species to get where we are
today, we have hundreds of thousands of years ahead of us, so it’s a
matter of being patient, taking a long-term view, keeping up the
‘message’, and showing that there is a way forward.

Brett Bellmore February 10, 2013 at 16:56

“In all those thousands of years, we will have almost certainly far surpassed our own initial star-flight capabilities.”

The issue has already been addressed in SF, though I forget the title, a classic novel had the first interstellar mission heading out using suspended animation, only to arrive at their destination a thousand years later to be greeted by cheering crowds. Nobody is going to leave on an interstellar trip, likely a probe won’t even be sent, until you’ve got the speed up high enough you’re reasonably confident nobody is going to build a faster ship after you leave, and beat you to the destination.

IOW, forget thousand year trips, except as last-ditch efforts to save the species from extinction. I’m betting the longest trip will be no more than 100 years, until technology has stalled for an extended period. THEN, you might get people behind the first wave of colonization willing to embark on long trips to get out ahead of the wave of expansion.

David J February 10, 2013 at 18:15

“With that in mind, who would ever sign up for a multi-thousand year flight? It seems doomed to anti-climactic disappointment from the outset”

Honestly? I think you would have NO shortage of sign-ups. I would consider signing up, for one. If there are humans there when I arrive, great, if not, also great.

There is also no guarantee that there would be future journeys that overtake yours – what you have is a class “bird in the hand worth two in the bush” scenario. I mean, for all you know, the day after the first ship leaves, the humans on Earth might wipe themselves out in an accidental all-out nuclear war or something stupid. So you have something definite, vs something possibly-maybe in future.

Also, such journeys are likely to be expensive even once the technology is there. There are lots of stars around us. Thus a future subsequent launch, with the faster spaceship technology, might simply decide to go to a different star.

Wojciech J February 10, 2013 at 18:25

The problem with worldships taking thousands of years to reach the target will be psychological(well one of the problems). We will likely not only be able to detect planets in other solar systems, but also take images of them, including images with visible vegetation cover(if one exists) and bio-markers in the atmosphere. With such knowledge it will be extremely difficult to propose a trip that lasts several generations before arriving at a place with a completely alien biosphere(which will be be a treasure trove of knowledge and possibilities for our civilization).
This of course is based on assumption that a living world is within a reachable range of our home planet. If it is 1000 light years away, it will raise different problems.

David J February 10, 2013 at 18:40

“If we do try star traveling world ships … just how big and robust must they be to survive thousands of years of human habitation? I suspect that they would have to consist of isolated systems so that if one part biologically or socially failed, it could be recolonized from another part.”

Way I see it, these are mostly ‘just’ engineering problems. Big, difficult ones, and it would be a massive and complex engineering project to design such a ship – but I’m not aware that any of the above would be ‘unsolvable’. You’d need e.g. mechanisms for things like radiation shielding, and mechanisms for e.g. hull repair from collisions (as well as systems for avoiding collisions in the first place). Peppering the ship with a network of sensors (similar principle to the sensory environment of a self-driving car) could be useful in collision-avoidance – i.e. a variety of sensors that ‘look around’, detect incoming objects, which could either be avoided by going around if possible, or attempted to be neutralized if possible (e.g. think something like the mosquito laser system). Failing that, for inevitable collisions, the system could even apply some “damage minizimation” algorithm to guess at the “least bad” way of handling a collision object. Some types of hull repair and ‘resurfacing’ could conceivably be carried out by specialized robots that could attach and crawl along the exterior. I’m not sure how one would cope with the wearing from e.g. internal material stress though, but I’m not an engineer.

“isolated systems” => This would be a given yes, I think. Potential costs could be reduced by keeping systems both ‘isolated’ and modular too, as one could apply a kind of ‘prefab’ principle … many interlocking submodules that have similar almost self-contained design. E.g. something akin to the principle used in the construction of the new skyscraper that a Chinese company is attempting to supposedly build in 90 days – i.e. making very heavy use of interlocking pre-fabricated modules.

As far as life on the ship would go, it would seem like an exercise in recycling as much as possible, e.g. converting waste back to food/water etc.

“And at this point, we haven’t even discussed the energy requirements to accelerate and decelerate the ship”

I am not an expert, but if I understand correctly, this would be one of the most difficult challenges to solve?

David C February 10, 2013 at 19:35

Alex, I agree that AI will either exist or we’ll know that it can’t exist by the time we try anything as ambitious as an actual trip to the stars (as opposed to a fly-by probe).
Like you, I believe that in time AI will exist, or something so AI-like that humans on a star-flight will be reduced to the status of passengers — hopefully VIP passengers, but passengers nonetheless.
AI or expert systems will be more than qualified to run the ship, fly the ship, decelerate the ship and launch planet-landers at the destination.
And whether or not human life extension is in the cards or not, it’s safe to say that we can build machines today that will easily outlive any currently living person. I realize that today we don’t build machines for longevity (primarily because we know they are going to be replaced by newer models anyway) there is nothing difficult in terms of theory or engineering in building a computer today that (with proper servicing) could stay on line for thousands of years.

GaryChurch February 10, 2013 at 21:54

We are learning to make fusion devices of very high efficiency; even if they are high efficiency bombs, thousands of them can slow a starship down from ten percent of light speed. Making the starship go fast out of our solar system will probably be done with a form of beam propulsion using tremendous energies.

Cryopreservation is different than cryonics because it includes resurrecting the tissue that is frozen. Those frozen now will have a long wait before the god-like technology required to repair their cells is developed. But freezing without damage is quite possible and this makes freezing star travelers the most likely way humans will seek to colonize nearby star systems. There is the argument that sending colonists on “slow boats” to other stars is a waste because much faster ships will eventually overtake them and arrive first. I disagree- I believe we should go as soon as possible as insurance against an extinction level event.
http://www.sciencedaily.com/releases/2013/01/130131095316.htm

jkittle February 10, 2013 at 22:59

As propulsion, AI and Life support technology improves, we will begin exploring deeper and deeper into the outer solar system, For manned spacecraft, we may stay with missions that last about 5 10 10% of our lifetimes ( currently 3 to 8 years) . For unmanned missions we will probably not exceed mission lengths of 20 % of out lifetimes…( 15 years) except for extended mission of probes and instruments that have exceeded their primary mission but are still producing useful data.,
As we move outward our interest in the objects in the outer solar system will increase and we will keep finding new interesting worlds to visit. Colonies may follow, with establishing a Mars or asteroid colony as a critical step (like going off to college) still close enough to home to realistically get some resupply but also sending a team that is largely responsible for their own fate. As our improving technology creeps up to 1% light speed you are looking at mission that extend out to one light week. this is roughly 1,000 AU. Interestingly, astronomical surveys have only ruled out large bodies like Neptune at that distance, there may be Mars to lunar sized planets lurking in the outer solar system ( 500 to 2000 AU), – but maybe not. Likely there will be at least a few dwarf planets scattered all the way out to the OORT Cloud. IMHO, Genetic modifications, if it ever overcomes the ethical challenges, will likely be used to extend human life out to a couple of hundred years. This would likely allow manned mission of twenty years or more.. and unmanned probes for 100 years or more. This puts the inner Oort cloud in play.
Moving beyond that either requires new physics, ( which is unpredictable by definition) or by launching mission from colonies beyond earth.. Exploring the outer solar system from an extraterrestrial city n , say, Iapetus, would be much easier than trying to travel from earth ( I also suggest that the majority of inhabitants of Earth may always be more interested the newest fashions than they are exploration) . So stepping-stones it is! Eventually the distinction between settling a dwarf planet and building a worldship will be lost, and our descendents will either 1)set out across the vastness of space to reach another Oort cloud around a different star, 2)every few million years life originating from earth intelligent and its passive commensal forms, will bridge the gap as stars pass close by, co- mingling their outer Oort clouds. Finally I do predict we could engineer a “biological incubator”, and organism that COULD be placed in stasis, and used to incubate and give birth to a shorter lived human descendent thus a 500 year mission with frozen eggs could be envisioned..with actually humans being grown on the other end to colonize a world with the support of there AI Machines..

David C February 11, 2013 at 7:19

Brasidas:” Given this sceario [the ability to survive indefinitely in open space], the worldship would not necesarily need to land anywhere, and therefore, why would it? Would such a structure even need a destination? Or, once reaching its destination, would it’s inhabitants bother to stop?”

Oh, I think they would “bother to stop”; it would be the Prime Directive of their mission. Even more than Prime Directive status, the idea of colonizing a new planet would be on the level of religious belief, something along the lines of the Jewish “next year in Jerusalem”, that kept the idea of Israel alive over thousands of years of Jewish diaspora.

But I do agree with you that if the ship is “warm” (not a bunch of suspended-animation crypts), that living off the interstellar medium, and massive recycling, would be absolutely necessary. To travel such distances the ship will need to travel indefinitely.

Just one thought along those lines: 3-d printing. The state of 3-d printing will be such that no spare parts will be needed at all… just the material to print them from. Who knows, given the design technology of a hundred years from now (which is when I envision the first launch taking place) the whole concept of spare-parts might be obsolete. The ship will probably be some kind of self-healing pseudo-organic whole with a sophisticated nano-technology at its base.

ljk February 11, 2013 at 10:21

Tarmen said on February 10, 2013 at 11:00:

“Ark ships, the subject of many sci fi books. Certainly the best laid plans will go awry. But the thing about ark ships, is that they themselves are a living colony. Even if they get “lost in space” and forget where they are going or where they started, they are still alive.”

I am going to assume you have never read Robert Heinlein’s SF novel Orphans of the Sky.

“Peoples of the 7 billion Earth would feel a great satisfaction if they would send even one ark fully loaded, 2 of each animal and an ecology to last as long as it takes. It would be like a father seeing his son move out and start his own career. “Stay in touch, son.”

Some would, but others would demand to know why THEY aren’t the ones going to be saved. Religious fanatics and those who just want to see the human race go extinct so as not to “pollute” the rest of the Universe will attempt to actively stop the mission.

The Worldship planners and builders should expect multiple terrorist attacks and other setbacks. Even if every human being could be lifted off Earth and launched towards the stars, there would still be those issues. Many will not want to go irregardless of the reasons.

As for saying goodbye to one’s children, would you want to let your kids go if you were never going to see them in person again?

“Many arks would be a better insurance that at least one would reproduce at some faraway wet planet and provide “grandkids”.”

Yes – assuming we can survive my conditions stated above. Small groups of the same mindset working off world are likely the best chances for an interstellar ark becoming a reality, if this really is still the way to go to the stars by the time such a thing can become possible.

ljk February 11, 2013 at 10:32

Larry F said on February 10, 2013 at 4:46:

“Colonizing uninhabited ‘alternate’ Earth’s in other dimensional universes of the multiverse, might be easier than overcoming the many hurdles associated with interstellar travel. We need a Multiverse Exploration Agency to investigate it. Especially if NASA fails to produce a viable ‘warp drive’.”

This needs to be repeated as many times as possible: NASA is NOT working on any kind of warp or hyperdrive! Unless they have got some secret kind of program going on, they aren’t going anywhere near such plans. NASA doesn’t even have a solid plan for sending humans to any other body in our Sol system, let alone Alpha Centauri, so why would you expect them to be making a warp drive?

No matter how much or which way you slice it, the key to warp drive still requires a form of “negative” matter, which no one can seem to clearly explain what that is exactly. So until someone comes up with some actual negative matter and gets it to work with a starship engine, warp and hyperdrives remain fantasy.

If you want to really get to the stars in the next few centuries, we need to focus on technologies and physics we can actually do now or in the very near future. Otherwise we will just have to keep journeying across the galaxy in our pretend starships and wishing ourselves into a corner.

A. A. Jackson February 11, 2013 at 10:45

I have been entranced with interstellar flight by way of modern science fiction since I first started reading it in 1953. Modern SF lead me to a Ph.D in physics, tho I have spent most of working life in engineering physics.
This lead to three papers in the JBIS on interstellar propulsion methods.
Yet , after, 60 years of thinking of methods of fast flight and the surprising development of ‘metric engineering’ (invented by Kip Thorne) … in the last 15 years my visceral inclination is to think that ‘slow’ flight , by way of near mortality or maybe even immortality will be the solution.
I say this because I think we are on edge of when molecular biology (spawned by and incorporating the physical sciences) will extent human lifetimes to 1000′s , if not 10′s of thousands of years.
Strategies of life extension are very numerous now I think will beat out propulsion physics in less than 100 years.
I can’t even imagine what philosophy and social structure and lord knows what such would bring. My thinking is that this is answer to the ‘Fermi Question’. Great advanced civilizations engage in ‘slow’ interstellar flight and follow the modification to Clarke’s law, that is they are not just indistinguishable from magic they are just flat indistinguishable!

(Note not having keep up with SF very well for the last 20 years I don’t have a list of immortal civilization stories. It’s odd, two of the best authors James Blish and Cordwainer Smith had both FTL and immortality. See CITIES IN FLIGHT (Blish) and The Rediscovery of Man (Smith). Cordwainer Smith still stands as the most unique science fiction writer ever! I know of no SF author’s stories like these before or after Smith.)

Thomas Hackney February 11, 2013 at 20:10

We need to focus on what is doable right now. We could start by building something on or in the moon. Since the U.S. is broke and getting broker by the day, we’re clearly talking about an international effort. The International Space Station seems mostly focused on research rather than on practical development of space habitats, though some of the research has practical applications for space habitation. The next step should be to build something lasting on Luna Firma. Something robust and expandable over time. Now that would be exciting! Space stations have such limited useful lives, after all.

Alex Tolley February 11, 2013 at 22:06

@ jkittle “Genetic modifications, if it ever overcomes the ethical challenges, will likely be used to extend human life out to a couple of hundred years. “

I wouldn’t bet on it. But let’s say for argument it was true. Then you have the problem of brain development. It is already becoming apparent that brains become “full”. Thus either an extended lifespan will result in a person unable to easily learn anything new, or, an engineered/rejuvenated brain that results in a very different person. The latter is probably preferable, but how well this is accepted will depend on how easily the personality changes can be adapted to by the individual and his social circle.

No doubt Homo stellar will be a different species/variety from us. Possibly unrecognizable as human.

James Jason Wentworth February 12, 2013 at 7:00

Thomas Hackney wrote:

“We need to focus on what is doable right now. We could start by building something on or in the moon. Since the U.S. is broke and getting broker by the day, we’re clearly talking about an international effort. The International Space Station seems mostly focused on research rather than on practical development of space habitats, though some of the research has practical applications for space habitation. The next step should be to build something lasting on Luna Firma. Something robust and expandable over time. Now that would be exciting! Space stations have such limited useful lives, after all.”

LUNA FIRMA…*that* is a term that we should use, and encourage Moon base advocates (organizations as well as individuals) to use. In marketing (of projects and causes, as well as products), a name or descriptor that captures the imagination can be quite effective in attracting supporters, and “Luna Firma” is such a name, conjuring an image of a human-inhabited Moon.

Steve Bowers February 12, 2013 at 9:44

Very slow ships have the advantage that a slow cruising speed requires much less power to achieve. Double the speed and you square the energy requirement of a mission. But the generation ship with a breeding population of hundreds, or thousands of humans seems a very inefficient way of making this saving. If the crew could be reduced to a much smaller number the power savings could be considerable. It seems very likely to me that by the time we are ready to build interstellar ships, advances in biotech will allow us to send much smaller populations and expect them to be viable at the other end.

Possible enabling technologies include life extension, stored zygotes or eggs/sperm cells, digitised genetic material, cold sleep, ‘hot sleep’ (this is the suspension of activity in a human body without freezing, in a form of living biostasis), and/or digitised human personalities.

Any or all of these technologies could reduce the active crew of a slowboat to an arbitrarily low figure, allowing relatively low-cost interstellar colonisation.

David J February 12, 2013 at 14:35

“Especially if NASA fails to produce a viable ‘warp drive’.””

I suspect that we are never going to find a way to beat the speed of light. The reason for my suspicion, I’ll admit is tenuous reasoning, but is based on recent extrapolations that estimate that in the observable universe alone, there are in the order of hundreds of billions of galaxies. Each galaxy typically has in the order of hundreds of millions of stars, and recent observations from the Kepler mission suggest that planets around stars are extremely common.

So given these staggering numbers, I suspect the observable universe must simply be teeming with life – probably almost every galaxy has complex/intelligent life.

But if that’s true, then we can apply some Fermi’s paradox thinking: If it was possible to travel faster than light (e.g. wormholes), then by now, “they” surely really would be everywhere, as it’s billions of galaxies with life multiplied by billions of galaxies to travel to.

Alternatively, perhaps it is possible, but just inherently extremely expensive, and so simply done very rarely.

Which actually, I suspect, might also be why interstellar travel within a galaxy is probably done relatively rarely by intelligent species — I mean, it is virtually a given that interstellar travel, at least, is theoretically possible. But it’s probably likely to remain an expensive endeavour whenever done.

I think we need to keep in mind a longer-term perspective. Our species is hundreds of thousands of years old. Even spending 1000 years in space to colonize a new world elsewhere would be but a tiny blip on ‘species’ timescales, and thus more than worthwhile.

David J February 12, 2013 at 14:40

“Has anyone considered, sending DNA and cloning humans near the end of the voyage, with machines to train the clones.”

I actually like this suggestion, but I have an idea. These first humans will surely need some kind guidebook, explaining they should go forth and multiply and so on. So we should leave the first cloned pair of breeding humans with a confusing, muddled ‘Guide Book’. It could perhaps explain things like which fruit are poisonous and not to eat them. This will end well, I am sure.

GaryChurch February 12, 2013 at 14:51

“We could start by building something on or in the moon.”

Absolutely agree. Luna Firma First!

Eniac February 17, 2013 at 13:08

I don’t think enough thought is given here to the fact that long before any humans go anywhere in deep space, unmanned probes will have gone there. With any luck, automated manufacturing technology will have advanced by then to the point where such probes can utilize available resources (in the asteroids, Oort cloud or other star systems) to build infrastructure without the presence of humans. Humans will then not go out into the unknown as pioneers, but simply travel well-known paths between well-supplied bases. By whatever fastest means available at the time, to whatever distances feasible. Most likely in suspended animation, because decades or centuries of sitting around and playing chess, watching TV or playing VR games is not such an enticing prospect.

On the other hand, as has often been said, those choosing to live in space may simply attach a motor to their home and RV through the Oort clouds, eventually all the way to a neighboring stellar system (which, of course, has already been fully industrialized by unmanned probes). Their ships/homes would pick up supplies regularly from unmanned bases along the way. Complete self-sufficiency will never be an issue, this way.

David J February 17, 2013 at 21:56

“Most likely in suspended animation, because decades or centuries of sitting around and playing chess, watching TV or playing VR games is not such an enticing prospect.”

Don’t forget the advanced robot girlfriend companions to help pass the time.

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