Interstellar travel and the crew

[Sarevok]

Do we really need exotic drives like antimatter propulsion or laser lightsails for interstellar travel ? It seems to me the weakest link is the crew. If they lived for a few thousand years trips to nearby star systems would be no problem. Now achieving biological or digital immortality is a colossal challenge. But would not it be easier and cheaper to develop than enormous cost of traveling at high fractions of c ?

[GrandMasterTerwynn]

Do we really need exotic drives like antimatter propulsion or laser lightsails for interstellar travel ? It seems to me the weakest link is the crew. If they lived for a few thousand years trips to nearby star systems would be no problem. Now achieving biological or digital immortality is a colossal challenge. But would not it be easier and cheaper to develop than enormous cost of traveling at high fractions of c ?

If you lived for 2000 years, would you want to spend a few centuries cooped up in a tin can? You could probably alleviate that somewhat by rotating crewpersons in and out of some sort of biological stasis or a hyper-realistic virtual reality, but both options aren't without risk. Furthermore, are you willing to carry a few centuries worth of life-support supplies (to make up for whatever inefficiencies exist in your life support systems), engine/internal power generation fuel, spare parts, and patching kits? Remember, that mass eats into the useful payload your ship can carry.

Getting between stars faster seems to be the smarter option.

[PeZook]

If they lived for a few thousand years trips to nearby star systems would be no problem.

We live for an average of seventy years or so ; Does this mean taking two years to cross the ocean is not a problem?

[Sarevok]

I was asking which would be easier to develop not more convenient.

[PeZook]

I was asking which would be easier to develop not more convenient.

No, you actually said if humans lived two thousand years then the trip wouldn't be a problem

Thing is, the engineering challenges to building a CHEMICAL POWERED interstellar starship are so absurdly immense that you pretty much have to invent something better. Trying to get to Alpha centauri with chemical rockets would be like attempting to use a rowboat to cross the Pacific.

[Simon_Jester]

Remember, also, that equipment has a mean service life expectancy too. Any piece of hardware on the ship will be far, far more likely to fail on a 1000-year voyage than on a 100-year voyage- or 100 and 10, or any other such combination of numbers.

And at some point, if you send an extremely slow ship out, there's a good chance that a century's R&D would enable you to build a better ship that would arrive at its destination much, much earlier, thus making the slow ship pointless.

[Sarevok]

I was asking which would be easier to develop not more convenient.

No, you actually said if humans lived two thousand years then the trip wouldn't be a problem

Thing is, the engineering challenges to building a CHEMICAL POWERED interstellar starship are so absurdly immense that you pretty much have to invent something better. Trying to get to Alpha centauri with chemical rockets would be like attempting to use a rowboat to cross the Pacific.

So the question becomes what would be an acceptable amount of time spent flying between stars. A 5 year trip to Alpha Centauri taking advantage of time dilation is too much... but so is the few hundred thousand years current rocket propulsion will take.

[someone_else]

It seems to me the weakest link is the crew.

I highly doubt you can make anything mildly technological able to survive more than 50 years of continuous operation without major overhauls.

But would not it be easier and cheaper to develop than enormous cost of traveling at high fractions of c ?

The issue is that even lightspeed is not enough to reach anywhere more than a few close stars in a decent timescale (Earth time), and time-dilation at moderately high fractions of c make pointless coming back, since Earth will be centuries if not millenia in the future.

So the question becomes what would be an acceptable amount of time spent flying between stars.

Depends from the goal. Colonization just needs to get to destination before the original passengers die of old age so you can avoid culture degeneration aboard the vessel (so time dilation becomes something you'd want), economic exploitation needs something worth the cost of interstellar travel and travel times in the realm of decades (Earth time, the time dilation on the freighters is not really relevant).

[Traveller]

I was asking which would be easier to develop not more convenient

Well, If it were possible, somehow to extend a human lifespan to the 1000+ range, that technology itself, would in all likelyhood be very expensive, complex, resource intensive and require trained specialists to maintain. I cant see how we could manage a form of hands-off, maintence-free 1000+ life spans. If that were the case, you would have to haul all that extra support structure along with you on the trip. So unless your crew could literally walk on in a t-shirt and shorts and have a 1000 year expiry date(which I really doubt), all that extra baggage to keep em ticking all that time would probably be better spent on an advanced drive, of some sort.

[Gandalf]

Even if people live for the better part of forever, won't they need food and other supplies for these multi year trips?

[Broomstick]

We live for an average of seventy years or so ; Does this mean taking two years to cross the ocean is not a problem?

Back when crossing the oceans took months, even years, yes, it was enough of a problem that people pushed to developed the means to do it faster. Very, very few people bother with 2 year long journeys.

[PeZook]

Back when crossing the oceans took months, even years, yes, it was enough of a problem that people pushed to developed the means to do it faster. Very, very few people bother with 2 year long journeys.

Thank you for answering my rhethorical question

[Broomstick]

Darn... that's why I keep asking for that rhetorical smiley! More caffeine prior to posting probably wouldn't hurt, either...

[PeZook]

Then again, one might point out that yes, some people DID spend two years or more at sea. This created its own massive set of logistical problems, and that was for ships that could live off the land in a lot of cases.

But an interstellar ship you just plain cannot resupply ; Breakdowns, spare parts, consumable stores, crew fatigue etc. would all quickly mount and could become fatal when in the great void.

See my rowboat across the Pacific analogy. The investment in developing sails is miniscule compared to the technology's immense and immediate benefits.

[bz249]

Remember, also, that equipment has a mean service life expectancy too. Any piece of hardware on the ship will be far, far more likely to fail on a 1000-year voyage than on a 100-year voyage- or 100 and 10, or any other such combination of numbers.

And at some point, if you send an extremely slow ship out, there's a good chance that a century's R&D would enable you to build a better ship that would arrive at its destination much, much earlier, thus making the slow ship pointless.

Yes even it is possible to build the super-duper reliable stuff (BTW: the known way to increase reliability is by making it bigger, reduce the efficiency or add redundant paths... all of them is sub-optimal, since they mean extra weight) the ultraslow design most probably mean that by a reasonable amount of time and research effort something better would appear.

[Sarevok]

I don't think the ocean analogy holds much water (pun intended). This is space, there is no wind, air or water here. Anything shielded from micrometeors and radiation should last surprisingly long periods of time in the sterile vacuum of outer space.

Most of the time spacecraft eventually die is because they are in continuous operation. Their solar panels degrade, batteries weaken, data tape motors fail and so on. Yet even then they last amazing amounts of time. Voyager and Pioneer spacecraft held out surprisingly longer than they were designed. And they were in continuous operation for decades. I am not sure if an interstellar spacecraft is going to face much wear and tear. For most of it's journey it will be dormant. Until it arrives at it's destination star system most of the ship is going to be practically brand new.

[PeZook]

I am not sure if an interstellar spacecraft is going to face much wear and tear. For most of it's journey it will be dormant. Until it arrives at it's destination star system most of the ship is going to be practically brand new.

No, actually it will need, at the very minimum, to operate its life support, sensors and computer systems for navigation. Those will break down, and while you can carry spares, the longer your voyage lasts, the more spares you have to carry. Furthermore, Voyager only lasted for thirty or so years, while interstellar travel with chemical rockets would easily take centuries.

Since, you know, it's useless to have a pristine power plant when all your crewmembers are dead.

[Simon_Jester]

Also, there's wear and tear from other sources. Certain systems may have to be periodically powered up and checked lest they freeze up entirely, chemical processes inside the ship may still attack some of the parts, and so on.

I mean, you could take a brand new car, throw it into deep space for a thousand years... that doesn't mean it'd run as soon as you filled up the gas tank and fired up the engine.

[bz249]

I don't think the ocean analogy holds much water (pun intended). This is space, there is no wind, air or water here. Anything shielded from micrometeors and radiation should last surprisingly long periods of time in the sterile vacuum of outer space.

Most of the time spacecraft eventually die is because they are in continuous operation. Their solar panels degrade, batteries weaken, data tape motors fail and so on. Yet even then they last amazing amounts of time. Voyager and Pioneer spacecraft held out surprisingly longer than they were designed. And they were in continuous operation for decades. I am not sure if an interstellar spacecraft is going to face much wear and tear. For most of it's journey it will be dormant. Until it arrives at it's destination star system most of the ship is going to be practically brand new.

Why should be vacuum inside the spaceship? There are at least some parts which have to endure normal atmosphere, the bare minimum is the life support system. Also there is the power source which have to withstand 1000 years in a rather unpleasant enviroment (running nuclear reaction) and these are just examples of critical systems which are nor really dormant neither spend any second in the sterile vacuum of space.

[Sarevok]

Why should be vacuum inside the spaceship? There are at least some parts which have to endure normal atmospherep

Only the parts containing the crew.

Also there is the power source which have to withstand 1000 years in a rather unpleasant enviroment (running nuclear reaction) and these are just examples of critical systems which are nor really dormant neither spend any second in the sterile vacuum of space.

The only power required is to keep the crew alive. The main engine itself could be shut off.

Yeah once again it appears the crew are the problem here. The spacecraft itself could power down, hibernate and wake up when it reaches the destination. With manned spacecraft there is the great challenge of keeping life support functional for decades or centuries.

[PeZook]

Not just that ; Over centuries, bombardment by high energy particles will degrade the very materials you use for hull plating. Nuclear power sources (at this moment, nuclear power is the only power source which could conceivably generate electricity for the voyage) will degrade by themselves thanks to neutrons from the fuel ; Computer systems have their own requirements and shelf-lives that happen merely with current flowing through some components.

Even if the big stuff like the engines won't be hurt by its stay in space, there's a whole lot of little things that could go wrong. Better to wait the extra century or two and invent a propulsion system that cuts the travel time, it greatly simplifies pretty much everything. It's not like a civilization that can build massive chemical powered ships will run out of resources in the near future, since this capability means their solar system is wide open for them.

[Darth Wong]

Not just that ; Over centuries, bombardment by high energy particles will degrade the very materials you use for hull plating. Nuclear power sources (at this moment, nuclear power is the only power source which could conceivably generate electricity for the voyage) will degrade by themselves thanks to neutrons from the fuel ; Computer systems have their own requirements and shelf-lives that happen merely with current flowing through some components.

Even if the big stuff like the engines won't be hurt by its stay in space, there's a whole lot of little things that could go wrong. Better to wait the extra century or two and invent a propulsion system that cuts the travel time, it greatly simplifies pretty much everything. It's not like a civilization that can build massive chemical powered ships will run out of resources in the near future, since this capability means their solar system is wide open for them.

Even seemingly inert components can be degraded by that much time. Atomic diffusion can cause tight-tolerance moving parts to literally weld together and become permanently seized, so that nothing works when you try to power it up again.

[StarSword]

Even seemingly inert components can be degraded by that much time. Atomic diffusion can cause tight-tolerance moving parts to literally weld together and become permanently seized, so that nothing works when you try to power it up again.

I can vouch. I had that happen to some bolts on a motorcycle exhaust pipe once. I read about another such incident in Popular Science, at the dark matter detector they're building in the Homestake Mine in Colorado.

[Sea Skimmer]

The only viable way of going between the stars with a human crew and real technology to me appears to be sending out a large fleet of multiple vessels, each with some specialization but no one vessel being ‘key’ and each vessel having a margin for crewmen from the other ships, as well as new births exceeding deaths. That way even if one is totally destroyed by say, an unexpected asteroid moving too fast to be detected in time, you aren’t screwed. If you had ships along with foundries and a bunch of computer controlled machine tools, plus highly advanced 3D printers you’d be able to repair or replace nearly anything. Larger more important items like reactors, might be carried as partly finished blanks, and trimmed down when needed.

The ships would be designed completely with replaceable components in mind, which would mean very bulky ships and generally smaller then larger machinery with a huge overcapacity. Likely you don't build a 50ft diameter nuclear reactor, you build a large number of 8ft diameter ones, and only turn on a quarter of them when the voyage begins ect...

The design would not be highly integrated, and features like bulkhead perforations and structural material within machinery spaces would be limited as much as possible. The ship frame and hull would just have to be massively overbuilt, and might even include stuff like a second skin, with the first skin being removed partway through the voyage when radiation bombardment has worn down its resistance.

Plus, think about it. If you are going to another world, you’re going to more or less need to bring along a complete industrial economy anyway, or at least the basics of one, if you are going to accomplish anything when you arrive at the other end. Especially if you are not traveling to a completely earth like planet on which you can just hope enough colonists dying can hack out a sustainable settlement. The only question is having enough contained volume to setup the vital tools as you need them, as opposed to everything being packed away all the time.

In any case, I don't think you strictly need anti matter or lasersails to reach .05 C or even .1 C, a super Orion drive (forth generation nukes would be handy for this, they are far more realistic for ultra long term storage to slow down at the other end) or ion engines, or a combo of both should be capable of it given a lot of time to accelerate and keep the total travel time to well under a thousand years to a nearby system. That seems possible for a human made ship to endure. Even with super exotic propulsion I suspect you would still need a massive onboard repair capacity anyway. Even ~100 years is kind of absurdly long. We expect nuclear reactors on the newest USN warships to last 50 years, but that does include two major rip the ship apart and rebuild overhauls.

[The Romulan Republic]

Well, Sea Skimmer, Project Dedallus projected a hypothetical ship using nuclear fusion to reach 12% light speed:

http://en.wikipedia.org/wiki/Project_Daedalus.

I have no idea how realistic that is though.