Interstellar travel; possible or not?

Great Debates
1

As a spinoff of this thread, wherein I expressed my doubt as to whether humans will ever leave the solar system, to which Dr Zoidberg replied:

Well, frankly, I *do think it’s a hard thing to do; I think it may actually be impossible.

0.1c is 67 million miles per hour; collisions with interstellar hydrogen atoms (1 per cubic metre?) would reduce our sleeper ship to a cloud of ionised gas in little or no time. We could hypothesise ‘deflector shields’, but these would be terribly energy-expensive to run, not to mention the side effect of slowing down the ship, necessitating more energy expediture to the drive system. These energy problems might seem trivial, but we’re talking about a trip that would take hundreds of years - where is the energy going to come from?

Then the whole ‘hibernation’ thing - it may actually be impossible, not tricky or difficult - impossible.

So… how would we overcome these problems?

2

Arthur C. Clarke wrote a book, I forget the name, where there are sleeper ships that use shields of ice as protection against collision. Every now and then when the shield is worn down and they’re close to a planet, some of the crew is woken up and they go down to the planet for a few months to manufacture a new shield.

3

Getting close to a planet is the end objective of the mission - not something you can do on the way.

4

I’m reading Is Anyone Out There? by Frank Drake at the moment. He makes what seems to be a good argument, based mostly on calculating the amount of energy required to cross interstellar distances in an acceptable amount of time, that human interstellar travel is unlikely to ever happen. Furthermore, he thinks (being a strong proponent of the notion that there are probably many extraterrestrial civilisations) that this nicely explains Fermi’s paradox - i.e. if there are so many other civilisations, why haven’t they visited us yet?

I do have a problem with this line of thinking, though. Just as Drake’s argument cites the inability of most people to really comprehend the distances and energy requirements involved in interstellar travel, I don’t think Drake is fully taking into account the enormous technologically advances that could occur in humanity’s future. It could take another 100,000 years of false starts and catastrophies for a human civilisation to spread to other stars, but I personally think it will happen. And I certainly think it’s very premature to rule it out entirely.

5

Technological advances may not help us if the nature of the universe (and particularly the speed of light being a finite limit) are stacked against us.

6

Interstellar travel within a single lifetime (by current actuarial tables) may not be impossible, but it’s not something I’ll bet much money on, either.

Really slow interstellar travel may be more feasible by a physical engineering standpoint–basically akin to sending a slow probe out thataways, but much larger and with added layers of complexity. Assuming Step Two* in the process to develop suspended animation/hibernation never occurs, the really big problems become human and social ones–how in the heck do you expect a necessarily small group of people (I figure they can carry along all sorts of extra frozen sperm and eggs to keep necessary genetic diversity up) to remain, well, sane over generations, in an environment that will kill them instantly if they ever really mess something up, with far fewer safety margins against simple human stupidity and error that we take for granted at the bottom of this big beautiful ocean of air. I sure don’t know–and I have this terrible hunch that the solution would be arrived at by some committee. Frankly, I’d rather wager my money on some mad scientist in a garage with a home-built interossiter inventing the warp drive fueled by a single potato.

  • from a favorite old cartoon that you might see tacked up on professors’ office doors anywhere in the world. Two professor types eyeing a chalkboard. Caption, “I think Step 2 might need to be expanded upon a little.” Chalkboard holds three steps of math: step one is various equations, step 3 a final simple solution arrived at, and step 2 between them merely says “and then a miracle happens…”
7

We have the technology to do it today if we really wanted to.

The Orion spacecraft concept is pretty simple.

You build an enormous ablation plate, and put your habitat and modules on top of it with a really good shock absorber.

Then you chuck nuclear bombs out the back and set them off. They explode, pushing against the plate, and accelerate you at stupendous rates.

Once you are up to speed, you turn the ship around so that the plate is leading, providing your debris shield even though collisions aren’t much of a problem in interstellar space.

A Daedelus type craft is not buildable today, but seems pretty feasible.
In both cases we’re talking about several decades of trip time.

8

It seems more likely we will learn to create a new universe before we learn to warp through this old one. The only way I can see of travelling through space in any amount of useful time is by something like teleportation or wormholes. I honestly think it more likely we will be able to create a new universe, with more flexible laws, before we get the whole ‘teleportation’ thing down.

Of course, this is hundreds, maybe thousands of years off… (C’mon, that’s a statement of fact, prove me wrong! Show me it’s happening within the century!)

'Course it’s just an uninformed opinion. :dubious:

9

The Orion craft is much easier to describe than it is to actually build. And far easier to build than to actually pilot across distances of the type that we are proposing. Do you suppose that the rest of the world will sit happily by, as one nation builds and orbits a million nuclear weapons in a launch platform with armor designed to withstand nuclear war? Would you want your favorite enemy state doing it?

And then there are the straight engineering considerations that rosy eyed optimists never mention. Just what period of absolutely perfect engineering operation do you expect? Triple redundancy only works until the second failure. Name all the complex mechanical systems you can think of which have operated for longer than a century without a single failure.

When science was new, and engineering was an art, there were occasional instances in human history where great works were carried out over century long periods. Not many of them, but a few. Cathedrals, The Great Wall, a few other examples. Things like the Roman road system are not truly integrated single systems, since they had useful benefits prior to the completion of the system. (Actually, Cathedrals did too, but those were social, not religious.) (Also keep in mind that the Great Wall didn’t work.)

As science matured, and engineering became a science, the duration of engineering projects diminished rapidly. In the modern world the suggestion that a project be planned for a decade is considered visionary. Twenty year long projects are only even considered if there is an intermediary benefit, and a massive need, from which the project can be expected to provide substantial relief. What other single scientific project can you name that took a century to complete? Anyone? Anyone? Bueller?

What single problem could a successful interstellar voyage solve? What material benefit would the society making this effort expect to receive? Keep in mind, we are, as of this point in the argument supposing a very kami kazi like one way trip. No one comes home, even with success. Success and failure are identical, from the point of view of Earth, baring a very good radio sent along.

So, after we consider whether such a trip is theoretically possible, we can then multiply the unlikely level of that consideration by the more extreme consideration of whether human society would do such a thing. I doubt that they would. I am not convinced that that is a bad thing, either. Dreaming of the stars seems to me to be the most beneficial part of the whole thing, for most of mankind. Dreaming of the stars is fine with me. Actually trying to get to them is probably not better than the dream.

Tris.

10

Tris: I agree with you, but I must point out that, in a very real way, the technologies we are using today has taken a century or more to reach. It had intermediate effects such as lights and space travel, and we didn’t know exactly what the technologies were going to be like… but by what I’ve read, the cathedrals had their floorplans changed every generation, so that’s more or less the same thing.

Of course, we’re still building this cathedral.

11

Please. We barely have the technology to leave Earth’s orbit and travel to the next planet in our solar system.

There’s no reason to believe that in a thousand years we might find a way to reach another solar system in a reasonable amount of time. After all, a couple thousand years ago, it was scientificly impossible to travel further than sight of land.

12

First: If we perfect whole body transplants http://news.bbc.co.uk/1/hi/health/1263758.stm, I’m sure we will over time along with other advancements in neuroscience and prosthetics, which helps to supply the need identified by Triskadecamus. We could have new bodies or be connected to mechanical ones that would be much easier to repair.

Second: If we perfect manufacturing on the moon http://aerospacescholars.jsc.nasa.gov/HAS/Cirr/EM/l8/Mining.htm as a solution to the environmental problems which is also a need. Now couple that with our skills building space lavatories, we will in time be able to construct giant contraptions in space to house a large population units complete with tourism liquor stores and babes.

With these two technologies we can have space villages that roam the universe for thousands of years and travel at speeds less than the 0.1 the speed of light without all the associated problems of doing so.

There will still be the problem of social interactions most of all tribal wars in these little villages that would threaten their survivability, but we have that here on earth and we have not destroyed ourselves yet.

This we must do and we have a few million years to achieve it.
http://www.valdosta.edu/phy/astro/pl_shows/bh_2001/bh/page10.html

13

I don’t care about your opinions :slight_smile: I don’t care this is a great deabets. I don’t have any arguments but I know that interstellar travel is possible. I also refuse to provide a cite. I will repeat it once more… INTERESTELLAR TRAVELL IS POSSIBLE

The alternative scares me.

14

We don’t know everything about the laws of physics yet, so we can’t say that some surprise might not pop up that would make interstellar travel much more feasible.

The biggest obstacle to traveling at high percentages of the speed of light is the energy required- 87% of lightspeed being equivalent to the ship’s rest mass, IIRC. But what if you could somehow manipulate an object’s inertial mass? If you could tinker around with Higgs particles in such a way as to “decouple” most of a ship’s mass so it only required a hundreth or thousanth as much energy to accellerate? Speculative bordering on fantasy I’ll admit, but there’s no telling what possibilities might turn up in the next few centuries.

15

is it possible? of course it is, you don’t need fancy smancy faster than light crap, just make a generation ship, set up a biosphere and go 8 miles an hour for the next million years!

what do you think the earth is? (kidding…sort of)

16

We aren’t going to travel to other star systems for a long, long time. If ever.

However, we’ll be bringing other star systems to us. There are already plans in NASA for telescopes large enough to image earth-like planets around other stars. Later plans include telescopes so large that they will be able to spot large artificial structures on planets around other stars.

Space interferometry is what allows this to happen. A single telescope like the Hubble has a mirror about 2.4 meters in size. The NGST, due to fly in about 8 years, will be slightly more than triple that size. But with interferometry, you can fly arrays of telescopes and make them look like one big telescope. One plan is to have an interferometry telescope with a theoretical aperture of about 6000 kilometers!

Within 15 years, we should be flying the Terrestrial Planet Finder, which will be able to analyze atmospheres of earth-like planets around other stars, including biological signatures indicating life.

The most advanced mission that NASA is already planning for is the Planet Imager, which would use a large array of NGST-like telescope and interferometry to actually image continents and oceans and other features on earth-like planets orbiting other stars. We’re not really close to this thing yet - it might be 30-50 years away unless NASA gets significantly more funding.

This program could be extended almost infinitely - imagine a telescope with an effective aperture the size of the Earth’s orbit…

Clearly, there is an awful lot of exploration of other star systems we can do right here in Earth orbit. The really interesting question is, what would we do if we looked at a star system with a huge telescope, and saw evidence of an advanced civilization? What kind of pressure would arise to go there?

Realistically, we can imagine the next steps - we’d probably start planning bigger telescopes to see more and more of that civilization. We’d aim huge radio telescopes at it to attempt to pick up signals. We might even try to communicate with them by firing large lasers at it or something.

But it’s all going to depend on what we find out there, and we’ll probably have a good idea in our lifetimes. We’ll have mapped the planetary systems of maybe the nearest 100 stars in our lifetimes, knowing which ones have atmospheres, what those atmospheres consist of, etc.

There are theories suggesting that the Earth is extremely rare. Current studies of other star systems have shown two types of system - ones with Jupiter-like planets that are extremely close to the star, and ones with huge Jupiter-like planets much farther out, but in highly elliptical orbits. Neither type of solar system is conducive to having an earth-like planet in orbit in the ‘habitable zone’ of the star, because the orbits would not be stable.

Other theories have suggested that life won’t develop at all in solar systems that don’t have a large Jupiter-like planet in the outer system, because these planets act like cosmic vacuum cleaners preventing a high rate of bombardment of meteors in the inner system.

We should have answers to these important questions in the next two decades, and those answers are going to give us a much greater understanding of what else and who else may be out there.

17

If we can create an artificial womb we may be able to send out frozen embrios in a spacecraft, Have it travel to another star system (even at 0.001c or less) and have the embrios thawed out and develop into humans - perhaps with some age acceleration.

The biggest problem I see with this plan is having the ability to build such devices that will last for 100’s or even 1000’s of years.

18

Forgive me, but I’m a little amazed at the extreme conservatism of the responses so far.

  1. Let us say that human civilization has been around for 10,000 years; a nice round number. We have been what might be termed a species-wide scientific/technological civilization for less than a century (IMHO–there will be arguments). I have read–the figure was not meant to be precise–that NEARLY ALL the major scientific discoveries of human history have been made within the last thirty years, especially since the advent of the low-cost, high-power computer. If one wanted to graph this sort of human advancement, you’d have to use log paper. In essence you’d have almost nothing until the extreme end–then a line moving almost straight up! And it appears that not only the amount of scientific discovery in increasing, but the underlying rate as well.

When good folks talk about discoveries a millenium away, or a million years hence–what are they thinking?? The “sufficiently advanced technology” that Arthur C. Clarke says is “indistinguishable from magic” will be available–for a price–by the end of this century!

  1. And it is wildly unlikely that homo sapiens would just happen to be the most technologically advanced species in (just to limit it) this galaxy. Given that there’s no a priori reason to assume an upper bound to the longevity of a technological civilization (in general); given that there are surely planets out there that possessed intelligent life millions or billions of years earlier than ours did; given that a sufficiently advanced civilization would surely have mega-speedy means of observing and cataloguing the rest of the galaxy; and given that they would almost immediately encounter other species who had gone before-- If we have not already met Them, it is surely because They do not choose to meet us–yet!

  2. Which is to say: wild-eyed stuff like super-C travel and space-warping, or more likely something we’ve never even considered, WILL BE AVAILABLE very soon indeed.

  3. But, to brass tacks. We’re already talking about sending a nuclear rocket to Mars (at least we were…before yesterday). So. We launch various components separately, and assemble our Interstellar Mission Craft in high earth orbit–maybe 500,000 miles out. The IMC is nuclear powered. Propulsion: laser thrust! The tech goal: accelerate a comfortable habitat at a rate of 1-G or so, continuously, to speed C. (I think I recall that it takes four years.)

  4. Surely we all know that as we approach C, onboard time slows down. I’m not stopping to work it out, but I think (remembering the need to decelerate at 1-G for half the trip each way)…the total roundtrip to ANYWHERE IN THE UNIVERSE would be about eight years of ship-time. People spend longer than that getting university degrees!

  5. Troubled by hydrogen atoms, bunky? Give the ship as narrow a cross-section as possible–think in terms of a flat hoop nine feet thick, four stories high, maybe a mile in diameter. I’ll bet some sort of electromagnetic field device could be used to sweep atoms and particles out of the path of the IMC (not an original proposal on my part).

  6. OR–make use of the hydrogen atoms–the interstellar ramjet!

  7. OR–think bigger. Hollow out an asteroid, set up a bank of laser thrusters powered by a fusion reactor, and set off with a city of people at some smaller percent G (if necessary).

  8. But my guess is that none of this will happen, because some reader of the SDMB, a Tom Swift type, will build a spacetime jumper in his garage!

19

What alternative?

That the human race will end on the same chunk of rock where it started?

Or that the bulbous-headed grey-skinned beings who abducted you are actually demons?

I need answers.

20

Skip, the book you refer to is The Songs of Distant Earth, perhaps the most beautiful thing Clarke ever wrote.

But your having mentioned it makes me feel that the most relevant statement that can be made in this thread is to point out Clarke’s Three Laws, the fact that the curve of rate of progress is tilting up towards an asymptotic future, and suggest that everything that everybody has proposed so far is not how the actual first interstellar flight will be achieved. How it will be, I have no more idea than anyone else – but I’m confident that the speculations to date are as wildly far from the truth as the various 1900 and 1950 essays on “what life will be like in 2000” are.