Traveling to Alpha Centauri

How long would you guess it could take to reach Alpha Centauri?
I've read some about it on the net and in various papers and there it says- even with far future technology- that it would take somewhere between 40-150 years depending on what kind of propulsion engine you're utilizing.

Do you think it would be possible to go to Alpha Centauri as it is right now, even though it would take ages (included in calculation the problems with higher amounts of radiation, space debris etc as a serious threat to equipment, personell and the ship itself) to get there?

I wonder how big the craft would need to be if let's say that we should colonize the planet and perhaps terraform it so that the travel doesn't become a dead end.

Self-sustaining ecology and perhaps even different creatures or cattle would be needed (or maybe just their respective DNA code for future cloning).

What do we know about the planets there? Is anyone habitable or at least able to be terraform, as i.e: Mars.

I'm pretty excited about this whole idea, though it would probably not happen during my lifetime

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i think that a ;arge enough ship could be built to be sent to alpha centauri. except it would take ages to get there. if an asteroid were put in earth orbit and we hollowed it out a bit, we could make living quarters, space for hydroponic food growing, etc., and mine the materials on the asteroid. strap some engines on it, and send it off. thing is, it would take many years to get there.

 

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Yeah, I've heard of that idea. Pretty cool if it'd work. I wonder what it would take to get an asteroid in orbit though

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I thought I read somewhere that with solarsails it would take somewhat like 40 years to get there.
And if we somehow would find a way to propell our ship to 99.9% the speed of light it would take us almost 2 months. heh. Guess it couldn't go faster than that unless we find us a wormhole.

Do we know if wormholes exists anyway?

 

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Nope, the possibility of worm holes existing is only theory, and I say the "possibility" because I don't think its clear yet whether worm holes "could" exist rather than "we've not seen one yet"...

its quite different for black holes though (give a few very generic assumptions as to the structure of the universe it has been proven that singluarities can exist)

If you wanna read about stuff of the sort, <A href ="http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&q=kip+thorne&btnG=Google+Search">Kip Thorne</A> is very knowledgable on these subjects.

later

 

Hmm.... about the asteroid idea..... I don't know, I feel like it's a bit hard to even devise.... gravity may be the first problem, then any possible rotation, and finally, we need size as well...

 

Moving an asteroid with a complete ecology inside is one strategy, but the amount of energy required to move it would be phenomenal;

perhaps a limited number of such generation ships will be launched, but I am convinced that smaller, lighter, faster ships will be more common.
As Wellcooked fetus has pointed out in the past, antimatter will be very expensive and rare, even if production techniques are a billion times more efficient than today's.

The crew and colonists might be stored in Nanostasis as imagined by Eric Drexler, saving space and consumables;
I have described such a ship in this document...

 

Even with today's technology, a probe could be lauched toward Alpha Centauri, but, as you said, it would take ages to get there.

I believe that it was Arthur Clarke who pointed out that any interstellar ship or probe we launch will be overtaken by something we launch years later. Therefore there's no point in launching anything interstellar at this point in our technological development.

Possibilities at this time could inlcude Nuclear-reacter-powered ion engines, or vehicles that make use of nuclear explosions for propulsion. That last one may sound unreasonable, but it's been seriously proposed.

Non-explosive fusion power would help. A technology that could easily and safely produce and store antimatter would help more. If antimatter rockets will someday be possible, then maybe we shouldn't launch anything interstellar in the meantime, because, as I said, it will just be overtaken later. But that depends on how soon the antimatter rockets will be available.

Of course one wouldn't want to build the antimatter rocket anywhere near Earth, because an accidental explosion could be very destructive.

Of course, because it could take a long time to develop the necessary antimatter technology, it might be worthwhile to launch, to the nearest stars, advanced nuclear-powered interstellar probes, when they're available. Or sails pushed by a powerful stationary laser.

There are a few other futuristic propulsion schemes that could become available before antimatter rockets.

I haven't heard of any planets being discovered around the stars of the Alpha Centauri system. It's been suggested that multi-star systems won't have planets, because the stars' orbital motion holds the angular momentum of the original gas-cloud, so that it doesn't result in the formation of a planetary accretion disk.

It seems to me that I read that single stars have less angular momentum than multi-star systems have (in the orbital motions of their component stars), suggesting that when the single stars formed, the contracting gas cloud they formed from gave its angular momentum to a disk of material ejected from the contracting cloud, something that may well not happen in multi-star systems.

Mike Ossipoff

 

If we were to skip all science fiction and start building on what we have now (assume cost is not a problem), then, yes we could mount an interstellar expedition, but it would be VERY risky. With the speeds we could attain, the trip would take several generations.

Btw, Alpha Centaury would not be a likely target, since we have no knowledge of any planet sustems there (to my knowledge, that is, they find new planet systems all the time), but within 5-10YL, there are a number of stars that do have planets.

There would be a long list of uncertainties, though. Just to mention a few:

1) We have no experience of maintaining mental and physical health for anywhere near the needed duration in space.

2) We have never built craft of the needed size and complexity (this might be one of the minor problems).

3) Rearing children in space is (obviously) totally untried.

4) We have little knowledge of conditions in interstellar space.

5) We have little knowledge of the structure of target systems, that is, we cannot be sure that there are inhabitable planets there.

6) We have absolutely no knowledge of what conditions to expect on an inhabitable planet, should we find one; will there be life? How different will it be from Earth life? etc.

7) And finally one thing that often seems to be overlooked: We have no good way of re-entry. That is, we do not know how to land heavy cargoes in a safe way, should we find a planet to land on. Problem is confounded by the fact that we don't know the exact gravity, atmospheric conditions and surface topology of the target.

We could do it now, but it would be a totally desparate undertaking. One might imagine it done as a last-ditch attempt tos ave our species from a doomed Earth (which puts us back into sci-fi).

Hans

 

thank you guys. Really interesting read.

I wonder if let's say that we would propel the ship by nuclear blasts, how would that not damage the ship and how far away from earth is safe to detonate a nuclear device without having our planet suffer the consequences of radioactive materia?

 

Radioactive fallout from nuclear bombs is mainly secondary material, that is, material from the target area that has been made radioactive by the blast. Detonating a nuclear device in space is really pretty safe, but if course, you would want to get well clear of all sattelites.

How to make a ship that could withstand being propelled that way is quite another matter

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, but some sci fi writers have suggested using shields of ice for that sort of thing. The advantage is that you might be able to replenish your supply of ice in deep space (Oort cloud).

Hans

 

The nuclear explosion rocket probably shouldn't explode its charges in low Earth orbit, but instead should begin firing when farther out in space.

The nuclear explosive charge would be ejected from the back, and would be some distance away when it goes off. The rear of the ship would consist of a big plate that would receive the blast. The plate would be connected to the ship with some shock-absorbtion.

This has been discussed as Project Orion, and, later, as the Daedalus spacecraft. It seems to me that Daedalus would use small fusion charges, set off by laser or by electron beams.

At least one author said that Daedalus is the most promising near term starship proposal.

It's been estimated that some sort of nuclear rocket could get to Alpha Centauri with a travel-time of some decades.

Better than Daedalus would be the fusion rocket that could be built if we had controlled fusion power. But Daedalus could be built before that's available.

I don't think anyone would want to spend years in space, and so surely the first starships will be automated probes, and maybe ships equipped for automatically initiating the long terraforming process, with the idea that people could come later when faster transortation is available.

Someone has proposed an interstellar ramjet that uses interstellar hydrogen as fusion fuel. If the fuel must be stationary in the reactor, the ship's speed is limited to the exhaust speed. An exhaust speed of maybe 3% of the speed of light has been esstimated for fusion rockets.

The hydrogen "scoop" would be an immense magnetic field. Presumably the hydrogen would be ionized so it could be moved by the moving magnetic field. It's been shown that any material scoop would be too heavy per square meter to get any decent acceleration.

But some authors have suggested that an interstellar ramjet coiuld go much faster than that, and so they must feel that it could become possible to induce the fusion reaction in the hydrogen without making it stationary with respect to the reactor.
Such a super-fast interstellar ramjet doesn't sound any more attainable than the antimatter rocket, especially if it would be necessary to get fusion energy from the common forms of hydrogen.

There've been suggestions to use the galactic magnetic field for propulsion. I'm not claiming feasibility for those suggestions, but merely mentioning what I read somewhere.

Colonization would be inegalitarian, since only a few people could go, with currently forseeable technology. And, in any case, it would probably have to wait till much faster transporation is available.

There are serious ethical objections to colonizing planets that already have life, which is why I speak of terraforming in connection with colonization.

If the goal is to find a place to terraform and colonize, then it's been suggested that Barnard's star is a better bet than Alpha Centauri. They used to say that Barnard's star appears to have a planetary system. I don't know if that's still said, but according to some theories of planet formation, any single star is likely to have at least some kind of material orbiting it, to absorb the angular momentum of the contracting gas cloud.

It seems to me that colonization must be limited to planets that have no life before our arrival. Interstellar colonization might make more sense when our own solar system is about to become unliveable. But that's so far off that much easier travel technologies might be available by then. Also, by then, we might have the technology to move the Earth farther from the sun when it's about to flare up and expland, and them move it closer in when the sun settles down to a lower luminosity star that will burn for trillions of years. If moving the Earth around sounds preposterous, remember that I'm talking about a technolgy billions of years older than ours is now.

Mike Ossipoff

 

How far away from now do you think fusion technology is? I saw a show on TV that discussed the topic of fusion. As far as I remember, they actually got it to work for like 1 second, or perhaps even a shorter time, which won't do us any good. But at least it's a start.

Heh, it kinda sucks that we live now. It would be cool to experience planet colonizations and terrafroming and advanced space-technology

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Fusion is, and always has been 'twenty years away'.
That means that no-one working in the field is really expecting to see break-even in their career;

hopefully this will not always be the case.

There is He3 and Deuterium galore in the Solar system; we could live in the coldest reaches of the Oort cloud for millions of yeas if fusion was available.

Mike- the problem with Bussard ramjets is that the magnetic scoop acts more efficiently as a brake than as a fuel collector;
this effect is useful, however, and saves fuel in the deceleration phase.

A number of modifications to the ramscoop have been proposed to make it viable; the RAIR and the seeded ramscoop are particularly promising.

But a He3/Deuterium Daedalus drive might well work, if you don't expect to take too much payload.

_________________
SF worldbuilding at
http://www.orionsarm.com/main.html

 

Yes, controlled fusion that gives more power than it takes might still be a long way off. So right now it's either fission rockets or explosion rockets, or one of the laser proposals, such as the sail, or this:

It seems to me that one of the possibilities that E45 referred to involves using powerful stationary lasers to provide power to the ship, with which it would operate a rocket, with interstellar gas as its exhaust-mass.

It's been proposed that maybe a fission rocket could eject the spent fuel as its exhaust-mass. I believe they called it a gaseous-core reactor. It sounds like something that won't be attained soon.

I agree that this isn't the best time in history to live. Myself, I'd prefer the late Paleolithic, when life was simpler, and probably better in many ways.

Of course there _might_ be a future in which today's problems have been solved and things are better. Technology has improved the quality of life in some ways, but in important ways it hasn't brought any progress.

Mike Ossipoff

 

Apology if this has been covered, but it seems that the most obvious point has been overlooked. If we were to accelerate long enough and at a reasonable rate, then something that is an arbitrary number of light years away, say 4, can quite easily be reached in a number of days, in the time frame of the traveler. This does not contravene the speed limit of light, it just demonstrates that space is contracted, as observed by the high speed traveler. The problem is, that we are not well equipped to cope with sustained high accelerations.

 

Quoting:

If we were to accelerate long enough and at a reasonable rate, then
something that is an arbitrary number of light years away, say 4, can
quite
easily be reached in a number of days, in the time frame of the
traveler.
This does not contravene the speed limit of light, it just
demonstrates
that space is contracted, as observed by the high speed traveler. The
problem is, that we are not well equipped to cope with sustained high
accelerations. [/B]

I reply:

One g would be comfortable as a sustained acceleration. But the real
problem
is the problem of achieving enough acceleration for a long enough time
to
get a reasonably short travel time. With current or soon forseeable
technologies, they say it looks like decades to get to one of the
nearest
stars.

One thing I meant to add to my previous posting: One suggestion has
been
that a ship get its power from an array of powerful stationary lasers,
and
that the ship carry its exhaust-mass, firing it backwards by means of
the
power that it gets from the lasers. That may be the fastest of the
stationary laser proposals.

The ship could deploy a gigantic mylar plastic sail, like a parachute,
to
receive force from the laster beam, and reflect some of its energy back
on
collectors on the front of the ship. The rocket powered by the
collectors on
the front and back of the ship would be the main propulsion, but the
force
on the sail would help some.

Maybe that proposal is one of the best contenders for now, along with
the
explosion rocket and the high-exhaust-speed rocket powered by a
conventional
fission reactor.

Of those 3 proposals, maybe the stationary laser proposal would be the
most
expensive, with its large array of big lasers. But I wonder if it would
also
be the fastest of those three rocket types.

Geoffry Landis discussed the laser-powered rocket, and suggested its use in combination with a laser-pushed sail, with the sail becoming the more efficient propulsion if speeds greater than .5 c are desired.

His article can be found by searching for "laser powered interstellar rocket". It seems to me that a link from there led to an at-length discussion of laser-powered sails, which concluded that they seem feasible. Maybe that could also be found by searching for "Laser-pushed sail, interstellar". Other interesting articles can be found by searching for "Barnard's star", "Daedalus starship", etc.

Of course if the mission's goal is to find and examine planets, then
the
mission should wait till planet detecting technology has improved some,
as
it's expected to.

But, for now, Barnard's star, the nearest single star, seems a likely
first
destination.

Barnard's star was the initial destination for Daedalus.

There's a thread in the General Science & Technology forum that discusses colonization. It's the Lifeboat Project thread.

Mike Ossipoff

 

Probably the best, simplest and cost effective thing to do is too try and lure some alien spacecraft into landing here on Earth.....Maybe you can convince them to take you to Alpha Centauri in trade for some good KFC or McDonalds Burgers....

Give it a try. You've got nothing to lose.......

Norm

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what do you know about ideas and proposals for
a thorough exploration phase using automated probes?

I recall that Freeman Dyson, among others, has advocated thinking in terms of sending out dozens of small comparatively inexpensive ion-drive craft to obtain information about known exoplanets---the small minority which appear to be possibly habitable.

I don't remember what power-source he mentioned, for the ion drive. Maybe it was some type of nuclear (thermionic?) with few moving parts.
The point was miniaturization and cheapness----he called the probes "space chickens" which I suppose suggests that they are relatively small and inexpensive with only modest information-gathering powers, not terribly speedy, and to be sent out in flocks. Do the exploration with large numbers.

Personally I would see proposals for un-manned exploration as more interesting for now. So many exoplanets have already been spotted-including at least some with not-too-eccentric orbits at a habitable distance from the star. We can expect many more to be found and some information on atmospheres of earth-size planets to eventually be provided from space telescopes here at home.

So what are the current ideas for sending unmanned probes to some likely prospects? Is having to wait centuries for the thing to report back a serious deterrent or can human organizations cope with such lengthy delay? Some puzzling questions here, for me at least.

 

If you look at the reality of space travel and the distances involved, then you can imagine that during this century we'll probably not get beyond our solar system, if we get that far.....So what type of propulsion system do you have in mind to propel us out of the solar system where we can enjoy the opportunity of visiting a nearby star???......Of course there is nothing like a few hundred or thousand good ole Atomic blasts to push you to the furthest reaches of space.....

Just out of curiosity, how many atomic fission blasts does one need to get them to Barnard's Star??? It's just mere 6 plus light years away and thought to have at least one Jupiter sized planet orbiting around it. 100??, 1,000???, 2,000??? Let's see if we can speed things up a little and use some 15 megaton fusion blasts instead.....I'm not sure if we'll get there in one piece and if there will be any metal left on the space ship, let alone anyone left alive after a few nuclear megaton bumps............But it's worth a try don't you think???

Hey we're there!!! How long did it take??? Only a few hundred earth years....Or was it one hundred earth years???.....Now we have a real problem!!! How do we stop this thing??? Opps!!! I forgot to mention that it takes the same amount of energy to slow us down and stop us as it did to speed us up and get us here......I don't think we brought along enough nuclear blasts to stop us!!!!....So long Banard's Star........

Only time will tell.....

Norm

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