# Is interstellar flight possible in near future in a way that would keep our civilization alive?

Is interstellar flight possible in the near future in a way that would keep our civilization alive? I mean is it practically possible to obtain technology that would enable us to travel to nearby habitable earth-like planets to keep our civilization alive?

For example, consider this design for NASA’s Star Trek-style Space Ship, the IXS Enterprise. Do you know any good site which goes into detail on both latest practical and theoretical development of this interstellar flight?

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Would Space Exploration.SE be a better home for this question? – Emilio Pisanty Aug 11 '14 at 11:37
@Danu 's answer is great, presenting just a tiny fraction of the overall challenges in the process in a way that already makes it seem (unfortunately) implausible. Also consider that human beings have existed for about 40,000 years (unless you're a creationist I suppose), so after taking 10,000 years to get there we might not even technically be humans anymore! Our best chance at longevity is the (still very distant) possibility of colonizing another planet in our system. Or by some stroke of luck inventing FTL travel. – thanby Aug 11 '14 at 12:44
From what we can know about the other planets, the nearest habitable earth-like planet most likely is Mars - some planet a dozen light years away might turn out to be more habitable or less habitable as such, but due to distances involved it would be immensely harder to habitate them than Mars. And no humans have even gone there yet. – Peteris Aug 11 '14 at 15:28
– Bobson Aug 11 '14 at 15:34
@KyleKanos: the alcubierre warp drive is so ludicrously far from "near future" to be ridiculous. It is almost certainly impossible to build one, as it requires a Jupiter's worth of negative matter, and we haven't ever found an atom's worth of negative matter. – Jerry Schirmer Aug 11 '14 at 17:17

The link you posted refers to a design which would supposedly make use of faster than light travel. After reading this, I immediately stopped reading, since this is not possible. I don't care if it's a NASA-affiliated person who says this, it is simply misguided!

Before continuing, I should draw your attention to the fact that I will not be discussing the Alcubierre drive, a highly speculative method of achieving very fast space travel which I personally think is more based on wishful thinking than anything else. Instead, I will stick to methods of travel that to not depend on manipulating spacetime in an exotic way.

A different question is whether it might be possible without using faster than light travel, although the answer is almost certainly still no. From this wikipedia article we learn that the closest possibly habitable planet would be around 12 light years away. This means that, traveling at $c=299792.458\ \frac{\text{km}}{\text{s}}$ one would take about twelve years to get there.

Let's assume a best-case scenario, where this planet turns out to be absolutely perfect - with minimal issues pertaining to adjustment to a different atmosphere etc. - while we also ignore any logistical issues like building enough spacecrafts to transport a significant number of humans (note that these issues alone will probably already make moving to a different planet an infeasible plan in a realistic scenario!). Let us just focus on the travel time.

From some further wikipedia research (notably here and here) we can conclude that our fastest (unmanned!) spacecrafts currently have a speed around $20\ \frac{\text{km}}{\text{s}}$. Let us, for the sake of discussion, assume that we can significantly improve on this "in the near future". Say some great technological breakthroughs occur that allow us to improve the speed of our spacecrafts by over an order of magnitude(!) to about $v_\text{sc}=300 \frac{\text{km}}{\text{s}}$ - this number is chosen somewhat arbitrarily; it makes comparing to the speed of light easy. Then, our estimate time of arrival would be

$$\text{ETA}\sim 12\ \text{year}* \frac{c}{v_{\text{sc}}}\approx 12*10^3\ \text{years}$$

As you see, we might experience some trouble here, too ;) In short, I think it is safe to say that we will not be able to move to a different planet in the foreseeable future.

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I just did an expeiment with my daughter's classmates where we "built a rocket": said rocket comprised a little cart with high quality bearing wheels (so it ran very freely) with a pile of medicine balls on it and two pilots (my daughter's friends). On countdown, the pilots throw the medicine balls backwards and we see who can get the cart going the fastest. Then we watched the launch of Apollo 8 and talked about how much of the rocket has to be "thrown away" as fast exhaust simply to get into orbit and to the moon .... – WetSavannaAnimal aka Rod Vance Aug 11 '14 at 12:15
...By the end of all this, several of the children had reached your conclusion themselves! "All that to get 3 astronauts to the moon?! ..." – WetSavannaAnimal aka Rod Vance Aug 11 '14 at 12:16
One side note, Alcubierre warp drives do not employ FTL travel. They utilize general relativity to expand and contract space such that they shorten the distance one has to travel at sub-light speeds to the point where it takes less time to traverse the distance than it would take for light to travel the whole, unaltered distance. This is completely allowed in general relativity. However, it does require exotic matter with negative mass – Jim Aug 11 '14 at 15:40
Also, the biggest problem is not the time requirement, it is protection from dust. With a high-ISP drive, we could get up to 0.1c probably (still take you 120 years so maybe faster would be better). But at that velocity, even a 10g speck of space dirt (of which there is massive abundance everywhere) would impact the ship with the force of an atomic bomb. And no, sticking a dust buster on the front of the ship probably won't help – Jim Aug 11 '14 at 15:53
@ChrisWhite My comment isn't about physics. My comment is about people who see one statement and shut down based on general failures of imagination. Your reactionary response or assumption of what I understand or do not shows even more kneejerk-talk. – HostileFork Aug 11 '14 at 21:00

It's easy after we rebuild ourselves first. We need to replace biological brains by digital brains. The problem we now have is that if we travel, we carry a biological machine that is much more advanced than the most powerful supercomputer we can build today, physically to the point of destination. This biological machine must always be kept at the right temperature, it needs to be at the right atmospheric pressure etc. etc.. Obviously, it would be far more practical to have a digital version of these biological machines and then simply upload the data to a machine at the point of destination.

The question is then how to bring machines with the necessary infrastructure to the next inhabitable planet? This may be done using nanotechnological means, you can imagine that only need to send a microscopically small device which only needs a small rocket to a distant planet and then the device will grow all by itself and we'll have the machines ready to receive us via radio transmissions (or perhaps laser transmissions which have a far lager bandwidth).

Another possibility is to send messages to distant civilizations. While two way communications take a long time, to upload ourselves to another civilization only requires one way communications. All we need to do is to repeatedly transmit our messsages that catch the attention of some distant civilization followed by the data containing all the information needed to be able to run our brains. It may be that our civilization will be long destroyed when the messages are still on their way. If millions of years later we are received by a civilization in the Andromeda galaxy and they manage to run our programs, we'll not perceive this time lag. To us it would feel like we've arrived there at an instant.

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Agreed that the problem gets simpler with digitization (check out Accelerando, if you have not)--but it brings in that semantic issue of what counts as preserving "our civilization". Some would be happy with robots wandering archives, others would not be. The unpredictable technological curve that would exist around the era of being able to digitize humans might mean rapid discoveries to the point that "biological machine transport" in space is a walk in the park, in the scheme of problems. – HostileFork Aug 11 '14 at 21:58
We just have to hope the aliens are using the same operating system as us. – zibadawa timmy Aug 11 '14 at 22:02
@zibadawa Hopefully that's not Windows, we do enough bad Stuff without Bugs ;) – Sebb Aug 12 '14 at 17:33
@Count Iblis: Ok. I would like to know if you know any good site for discussing about technology required to colonize Mars? – alvoutila Aug 13 '14 at 9:54
@laovultai - Try space.SE – Bobson Aug 13 '14 at 17:26

As @Danu said, the transit time is a massive problem. One of the comments to his answers mentioned that keeping the passengers alive might be difficult too. You need

• protection from meteorites, or the ability to take some losses and repair damage (as stated by @laovultai)
• protection from radiation i.e. solar wind when you're close(ish) to the sun
• an energy source when you're far from the sun (solar won't work, and I'm not sure if nuclear is compatible with passengers)
• a completely sustainable ecosystem/oxygen supply
• gravity, or some way of preventing muscle atrophy
• social factors might be nice to consider, to stop your passengers going insane
• etc.

These factors are important if you're going to be in space for more than about a year, so manned visits to neighbouring solar systems might be impossible even if your spaceship is a couple of orders of magnitude(!) faster than @Danu's.

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All your issues basically boil down to "it will have to be one huge ship", but that is not a science problem. It's not really an engineering problem, even, but a financial one. Gravity is fixable by spinning the living compartments, solar radiation versus meteorites just requires a big shield which is moved to the front somewhere near Mars, etc. – MSalters Aug 11 '14 at 22:19
@MSalters good point. I'm going to have to call in the "near future" clause then. Depending on your definition of "near future", the financial means won't be available any time soon. – craq Aug 12 '14 at 11:00
@craq as mentioned above, if we get the ability to use asteroid ressources it shouldn't be that difficult any more (but still be a huge project). The shield is more difficult I'd guess, since we don't have any technology which is able to absorb big impacts over years. – Sebb Aug 12 '14 at 17:39
@craq: Do we have technology to colonize Mars? I think yes, but do you know any site that discuss on that? – alvoutila Aug 13 '14 at 9:53
@laovultai I wouldn't necessarily recommend any specific site, but there are plenty. It's probably best not to trust just one source anyway. My impression is that we're not far off (i.e. I expect people to be on Mars this century, maybe next century you could call that a colony). But we should demonstrate a completely sustainable ecosystem on earth first. Search for biosphere2 to find out about the first attempts. – craq Aug 13 '14 at 11:33

## protected by Qmechanic♦Aug 12 '14 at 12:55

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