The Most Scientific Plausible Method of Interstellar Movemen

[Werrf]

And he's right. Crews require a variety of thing extraneous that take up more space that can be used for other things.

Yes, I agree. For most purposes - scientific, exploratory, mining - a crew would be useless.

And his statement had nothing to do with colonisation. That was an assertion you made, along with your secondary assertion of world/solar catastrophe. So you attacked him on his statement when his statement had nothing to do with what you were saying.

The statement - as I read it - was that for any possible mission profile crews make things more difficult. For most possible profiles, yes, that's true, crews are unnecessary, but if your mission profile is colonisation, it's not. I was just disagreeing with the any possible mission part. If that wasn't what he meant, then I apologise for the misunderstanding.

[Sarevok]

Bear in mind even for colonisation crews are questionable. Think about the following

- You are traveling light years to another star system. You bring with you lifeforms evolved on another world orbiting a distant sun. And you expect it to thrive when it gets there. What would really be more logical to ensure survival of human species ? Bring our evolved in African continent selves to Alpha Centauri or remake ourselves to better suit the journey and the local conditions of life under an alien sun ?

[Wyrm]

(I'm probably mixing up my fictional 'verse with the real 'verse too much, but I still believe this stuff is possible - you just have to look in the right places.)

Um, yeah. You'd probably do well to keep your fictional universe well-separated from the real universe, especially discussing things here.

See, while reactionless drives and Alcubierre drives are nice, they have very serious problems with physics as we know it. Reactionless drives requires there to be some process which violates conservation of momentum, and the skinny on that is that it requires there to be a change in some physical law as you move from place to place, and as far as we can tell by looking through telescopes, the universe seems to follow the same laws as they do here. The conservation of momentum is well confirmed by experiment, and there are very good theoretical reasons for believing that it is an ironclad law. While there might be a glimmer of a chance that there is some hole in it, we'll find that hole time a long time before we can exploit it.

As for the Alcubierre drive, its problems are myriad: you need obscenely large amount of energy to construct them, to the tune upwards of many solar masses for any reasonably fast drive of practical size; lacking already exant FTL motion, they are not "first drives", in that the drives require you to set up some sort of infrastructure along your proposed route; they are impossible to control — once started, you cannot stop or steer the ship.

"Go beyond the impossible and kick reason to the curb" is, indeed, a catchy motto. Sadly, it's reason and evidence that allowed us mastery over our environment: "Examine everything with a reasoned eye and make nature your bitch" is the motto that actually has served us well.

[Serafina]

You don't actually need a physical crew to settle human life on another world.

We can already freeze inseminated eggs or embryos for a long time without any damage. An artificial womb is not scientifically impossible or even improbable - but it's not certain whether we will ever be able to freeze and unfreeze adult humans.
Either way - send the colony ship, install the necessary facilities with robots, and then raise the new generation of humans.
That requires:
-a way to breed embryos without a human mother
-already existing freezing technology
-robots that are intelligent enough to build up a small colony
-robots that can take care of children

It doesn't require true AI, brain uploads of futuristic cryogenics. It's certainly not doable today, but not scientifically impossible.

[CSJM]

(I'm probably mixing up my fictional 'verse with the real 'verse too much, but I still believe this stuff is possible - you just have to look in the right places.)

Um, yeah. You'd probably do well to keep your fictional universe well-separated from the real universe, especially discussing things here.

I might explain here, a lot of "advanced science" in my fictional 'verse comes from finding faults in established systems. Like how you can bypass conservation of energy by forming a very complex energy pattern, which suddenly explodes into a spray of all manner of radiation like a cellular automata seed. And then imprint the pattern into metal to continuously reuse the effect. Essentially, I believe this principle has a right to exist in our universe as well. We just haven't enountered the required patterns yet, because they are too complex to have a significant chance of occuring by accident.

I guess I'll stop now, this really isn't for the topic at hand.

[Sarevok]

You don't actually need a physical crew to settle human life on another world.

We can already freeze inseminated eggs or embryos for a long time without any damage. An artificial womb is not scientifically impossible or even improbable - but it's not certain whether we will ever be able to freeze and unfreeze adult humans.
Either way - send the colony ship, install the necessary facilities with robots, and then raise the new generation of humans.
That requires:
-a way to breed embryos without a human mother
-already existing freezing technology
-robots that are intelligent enough to build up a small colony
-robots that can take care of children

It doesn't require true AI, brain uploads of futuristic cryogenics. It's certainly not doable today, but not scientifically impossible.

You have robots that can build a colony and raise human babies ? By what measure is this not "true AI" ?

With that level of wank tech computer science you wont need flesh and blood human beings anymore. Human crews for interstellar expeditions would be totally unnecessary when your starship itself is a sentient living being with an intellect far greater than any human.

[Serafina]

Just build a big spaceship and stuff premade buildings on it. Build less-vital buildings from simple materials.
I don't see how that requires true AI - even if you would have to find and use some metals. They are not supposed to build a fully functional colony, only to provide a starting condition for the future generation.

[Sarevok]

Just build a big spaceship and stuff premade buildings on it. Build less-vital buildings from simple materials.
I don't see how that requires true AI - even if you would have to find and use some metals. They are not supposed to build a fully functional colony, only to provide a starting condition for the future generation.

You don't understand how difficult it is to make even a sand castle using automated robots. If someone comes up with a simple robotic sand castle building program that makes a structure given a CAD file he would be swimming in cash.

As for pre-made buildings need I mention the mass penalty ? The very reason for cutting a living crew is to save mass. Packing a ship full of a pre made colony seems to be counter productive ! You save 500 tons.... then fill it up with 50000 tons so you have -4500 tons of mass savings ? Does not compute !

[Serafina]

I'm not saying it would be easy, but we are talking about possible according with current scientific knowledge.
Unlike adult cryogenics (which might never be possible), this one is. 'Of course, i might be wrong

[Werrf]

Just build a big spaceship and stuff premade buildings on it. Build less-vital buildings from simple materials.
I don't see how that requires true AI - even if you would have to find and use some metals. They are not supposed to build a fully functional colony, only to provide a starting condition for the future generation.

I think the "raising human babies" part might be considered a little tricky for robots that do not possess true AI. Hell, humans find it difficult enough as it is, without trying to pre-program robots to handle it. And even with AI, it's hard to imagine how that first generation would develop without any interaction with a culture, since they'd be essentially creating one of their own.

Though thinking about it, (and going a little off-topic, if that's okay), that sounds like a fascinating subject for a sci-fi novel - the first generation growing up and coming to understand what their place in the grand scheme of things is. Anyone know of any, have any suggestions? I enjoyed Clarke's "The Songs of Distant Earth", which covers something of the future of such a colony, but not its founding.

[Ariphaos]

The only way to feasibly and reliably move a significant mass past ~1% of c is to use a solar sail. Setting up a sail exchange program you can shuffle people back and forth at a rather healthy fraction of c, though the first time is going to waste some mass unless you're willing to take longer and/or get creative. Every other method is so vastly inefficient as to be absurd, at least with current understanding.

[Junghalli]

Running to another star system to escape a world-ending catastrophe is like flying to Hong Kong to escape a house fire in New York.

As for solar-system ending catastrophes, other than a collision between the sun and another star (exceedingly unlikely), we won't have to worry about one of those for five billion years. Even when the Sun goes into its red giant phase, there will be plenty of time for an orderly retreat into the outer solar system, assuming by that point we haven't figured out how to perform large-scale stellar engineering. I think it's fairly safe to assume that by the time we actually have to worry about the death of the sun, we'll have better technology available for interstellar travel than fission rockets.

A hostile AI takeover is one relatively plausible catastrophe where I could getting out of the solar system looking like a good idea.

Then again, a hostile AI could plausibly follow you; simply being in another solar system really isn't that much of a defense against a determined immortal entity with the resources of our solar system at its disposal. It'd probably be easier just to hide out in the Oort Cloud.

[eion]

Nuclear Salt-Water Rocket is buildable with current tech and could theoretically get you up to 3.6% of C if you use the 90% enrichment design.

A chemical rocket could theoretically get you up to 3.6% of C if your fuel tanks are big enough.

Yes, so would throwing tin cans out the back, if you had enough time. But in this case, the exhaust velocity and fuel requirements of the NSWR are sufficient to allow you to accelerate up to 3.6%C before the universe experiences heat death.

Chemical MAX exhaust velocity is 4,500 m/s, NSWR with a 20% enriched Uranium-Bromide salt is 66,000 m/s. Your Laser sail (which from your description I'm guessing is a laser powered Solar Moth) is around 40,000 m/s. Not a big difference you think? If you use the 90% enriched model (granted that one is a more advanced design), you get 4,700,000 m/s. Now Orion can be even faster, but others have already mentioned some of the problems with carrying several thousand nuclear bombs along with you on a five light year tour.

It's simple, powerful, fairly easy to refuel, and quite reliable, just remember it is essentially a continually detonating Orion Drive, so no take-offs on planets you care about.

It is also fiction. When something is considered "far-fetched by many scientists" and "other scientists are skeptical" of the key concept behind it, you can't say that it is buildable with current tech nor that it is the most scientifically plausible anything.

As fictional as an Orion drive, in the sense that no one has built or tested one, but they've certainly designed plenty. The key concept behind it is nuclear fission, are we still on the fence about that? You bring several sub-critical masses of Uranium together to form a critical mass, they explode, heating the 98% water mixture, which is your propellant.

As for skeptical, Atomic Rocket just throws that in, without any reference to whom these guys are and what their concerns are. I'm skeptical of their skepticism. If you have some reference to specific concerns raised by specific authorities regarding the feasibility of the NSWR, please post them. I just linked to Atomic Rocket because it has a fairly concise description of how the NSWR works and what you can get out of it. You'll notice the listing for the Laser-Moth really doesn't mention any of its drawbacks there.

My preferred concept for a starship is to use a giant laser from home to power the ship. That way, it doesn't need to take all that mass with it. The giant laser pushes it out and then stops it once it gets there thanks to mirrors. The hard part will be building the giant laser. Might work earlier on for a small probe though.

Yes, we both seem to have our favorites. Yours is just as fictional as an NSWR, at least until someone sends a probe to Mars or the moon using a laser sail.

One question, how exactly do you stop your probe if there isn't a laser or a mirror already there? If you're designing a laser-powered solar moth, then yes I can see you flipping the ship and just adding a second mirror to redirect the beam and slow you down, but your "USE A LASER" idea is rather vague. The laser is going to be the easy part (if we're going by current tech); the hard part is going to be getting the kilometers wide sail up there to begin with. There's also the issues with power outages, the impossibility of emergency course corrections, beam diffusion, planets and moons getting in your way, etc.

Every system has problems, that's why you should go with the simplest, most effective method you can find. Nuclear is the most likely way to go. It's simple, reliable, powerful, and doesn't require a 5, 10, or 20 light year extension cord.

[Junghalli]

One question, how exactly do you stop your probe if there isn't a laser or a mirror already there?

Theoretically, you could reflect the laser beam off a jettisonned section of the sail onto a smaller sail (link). Another possibility is to use magsail braking from the interstellar medium. This is at a level well beyond anything we could do today though.

Also, even if you needed a rocket to slow down laser propulsion could still be useful. You cut the delta V your ship's rocket needs by half, since you only need to carry fuel to slow down.

[eion]

One question, how exactly do you stop your probe if there isn't a laser or a mirror already there?

Theoretically, you could reflect the laser beam off a jettisonned section of the sail onto a smaller sail (link).

The Starwisp is a very interesting concept, but numbers like 43,000 terrawatts and a 1,000km diameter sail just stagger me. 50% of C is very nice. This one is a long ways off from current-tech, but very cool.

Another possibility is to use magsail braking from the interstellar medium. This is at a level well beyond anything we could do today though.

I do adore a mag-sail; every ship should have one, cuts your fuel bill in half They're not so far out there, what we're lacking is high-temperature superconducting wire. If it exists, the sail can be made, if not, it can't. It's certainly worth working towards. Even with a mag-sail, you better hope your laser power source doesn't suddenly fizz out the moment you need to charge your mag-sail to slow you down, or should they carry a back-up nuclear reactor just in case.

Also, even if you needed a rocket to slow down laser propulsion could still be useful. You cut the delta V your ship's rocket needs by half, since you only need to carry fuel to slow down.

See, you answered the natural concerns a laser-sail raises quite nicely. Destructionator's concept didn't go much beyond "IT'S BETTER WITH LASERS!"

[Junghalli]

I do adore a mag-sail; every ship should have one, cuts your fuel bill in half They're not so far out there, what we're lacking is high-temperature superconducting wire. If it exists, the sail can be made, if not, it can't.

I don't see why in principle you couldn't chill the wire. It'd be a lot easier if you didn't have to, but I don't see why needing a cooling system is necessarily a showstopper. Especially since it'd be mostly or entirely operating in a pretty cold environment (interstellar space) anyway.

[Samuel]

Planets and moons in the way isn't a problem too. Odds are it will never happen, and even if it does, just wait for them to pass. Problem solved.

Most planets and objects in the solar system are on the same plane around the sun. Putting your laser "above" (or below- there isn't really a top and bottom) allows you to avoid them.

[Wyrm]

I might explain here, a lot of "advanced science" in my fictional 'verse comes from finding faults in established systems. Like how you can bypass conservation of energy by forming a very complex energy pattern, which suddenly explodes into a spray of all manner of radiation like a cellular automata seed. And then imprint the pattern into metal to continuously reuse the effect. Essentially, I believe this principle has a right to exist in our universe as well. We just haven't enountered the required patterns yet, because they are too complex to have a significant chance of occuring by accident.

Um... okay. That's basically your right as an author to inflict this on your own fictional universe, but understand that your notions don't necessarily carry any real scientific plausibility. Our best theories on how the universe works says that energy is indeed strictly conserved in all physical processes, and its a principle embedded deep into the very structure of existence and is the very farthest thing from scientific plausibility.

And welcome to this wretched hive of scum and villainy. Just keep your fiction well-divorced from your discussions concerning reality and you'll do fine here.

[RedImperator]

And I hate writing things off as "impossible". If it's believed to be impossible, isn't that a reason to try and do it anyway?

It's impossible for a human being to fly under his own power. By your logic, we should all be standing out in our front yards flapping our arms really hard.

When scientists say FTL is impossible, they mean it--FTL travel literally breaks the universe as we understand it (an understanding that's been tested to many significant digits). Conservation of mass-energy, if anything, is even more ironclad. It's fine to say, "Well, for dramatic reasons, in my story, scientists found a loophole" (though honestly, I'd ditch the idea of a loophole in conservation of mass-energy; perpetual motion machines cause most possible plots to collapse in a heap), but that doesn't apply to the real world.

The main reason I started writing hard science fiction instead of soft was because I discovered that the universe is just as interesting without a bunch of pulp-era tropes as it is with them. In most cases, more interesting.

A hostile AI takeover is one relatively plausible catastrophe where I could getting out of the solar system looking like a good idea.

Then again, a hostile AI could plausibly follow you; simply being in another solar system really isn't that much of a defense against a determined immortal entity with the resources of our solar system at its disposal. It'd probably be easier just to hide out in the Oort Cloud.

I'm pretty sure in the case of a hostile AI with solar-system wide reach, we're totally boned unless there's a friendly AI in a nearby solar system willing to offer asylum.

Yes, so would throwing tin cans out the back, if you had enough time. But in this case, the exhaust velocity and fuel requirements of the NSWR are sufficient to allow you to accelerate up to 3.6%C before the universe experiences heat death.

I wrote a book about people flying around in 90% enriched NSWRs. I picked them for two reasons: first, they had the right combination of thrust and specific impulse for the plot I had in mind to work. Second, they're incredibly complicated and explode if you look at them funny, which made them much more dramatically interesting than a rocket which just stops working if it breaks. Honestly, they're stupidly hard and almost certainly will never work, let alone work within the safety tolerances necessary for any human being in his right mind to ride on one.

[Shinova]

For FTL the alcubierre drive is the only thing that's taken relatively seriously.

[Questor]

For FTL the alcubierre drive is the only thing that's taken relatively seriously.

I ran into that, in Star Carrier. Do you know if the presentation in that novel is accurate, or just pulling a name?

[Guardsman Bass]

For FTL the alcubierre drive is the only thing that's taken relatively seriously.

I don't know if you can really say it's taken "seriously". There's a model for how one might work*, but you get all kinds of weird requirements like a shit-ton of "negative mass-energy" for it to work. Same goes for Wormholes, if I remember right.

*In the sense of how the basic principle of it might go, not in the sense of a model of a drive that we could actually build anytime soon, obviously.

[RedImperator]

"Relatively seriously" means "yeah, this almost certainly doesn't work, but there's a tiny sliver of a chance all your assumptions are right--good luck actually engineering it, if they are" as opposed to "LOL get out of my office".

[Simon_Jester]

Even Alcubierre drive requires very large supplies of matter that weighs less than nothing. So... not actually seriously, except in relative terms.

[eion]

Yes, so would throwing tin cans out the back, if you had enough time. But in this case, the exhaust velocity and fuel requirements of the NSWR are sufficient to allow you to accelerate up to 3.6%C before the universe experiences heat death.

Based on incredibly optimistic, arbitrary assumptions, nothing more. Even so, that number assumes a mass ratio of 10. For every ton of payload, you need 2 tons of highly enriched uranium and 8 tons of bromine and water, given the assumptions on Atomic Rockets (and assuming when he said "by number", he meant moles rather than mass). Sounds cheap!

Who ever said any of this would be cheap? Your mission (which lacks any estimates for power requirements) could require 43-Thousand times more power than is generated by the whole planet, and you'll more than likely have to base you laser in space, so now you have to generate 43-thousand times more power than a whole planet in a vacuum with far more issues of heat dissipation and such. That 43,000 number comes from the Star-Wisp 83,000 ton manned model.

Now fuel availability is BIG problem. You'd probably only use the NSWR in early excursions, and would very likely also use laser sails, fusion drives, and perhaps eventually antimatter drives. It was NEVER my point that NSWR are the ONLY way to get to the stars, though you seem to think so. I merely mentioned them because they are a novel concept that no one else had mentioned.

Now Orion can be even faster, but others have already mentioned some of the problems with carrying several thousand nuclear bombs along with you on a five light year tour.

Several of which probably apply to the NSWR too, such as the natural decay of the highly enriched uranium your assumptions require.

Undoubtedly, but it does sidestep the Nuclear Test Ban Treaty and prevents a rogue captain from selling off his propellant as ready-made bombs.

The key concept behind it is nuclear fission, are we still on the fence about that?

That's not the key concept. It is being able to put it in a salt water solution and maintain the reaction in a stable manner as it flows out. Fission isn't hard, a nuclear salt water reaction is.

So hard in fact that reactors have to be designed to prevent the very reaction required (a prompt-critical reaction) to make them work, SHOCKING! If you can build a bomb, which rely on prompt-critical reactions, you should be able to design a NSWR. It's just that such a drive could never be tested on Earth, unlike your laboratory concept.

As for skeptical, Atomic Rocket just throws that in, without any reference to whom these guys are and what their concerns are.

Atomic Rockets doesn't give any sources whatsoever beyond Zubrin's name. So it isn't a problem when results you like are unsourced, but if they question your love, it is suddenly unbelievable?

Having a copy of his book next to me, I know that the figures are the same in both sources, and knowing that Dr. Zubrin is a noted rocket scientist with multiple degrees in NUCLEAR ENGINEERING(rather than a Fox-Newsesque "Some people") gives me a certain confidence in his expertise and his numbers. I'll be the first to claim no capability in nuclear engineering beyond the "billiards analogy".

You'll notice the listing for the Laser-Moth really doesn't mention any of its drawbacks there.

I'm talking about a photon drive, the laser at home bounces photons off your ship, pushing it forward.

Okay, so: How big's the laser? What's its power output? Exactly how will you generate that power? Where will the laser be? How will that location affect your lasing of the ship? How will you construct the laser station if it is in orbit? How will you get rid of the waste heat if it is in orbit? How big is the sail? How much does it weigh? How will you construct and launch that? What's your mass ratio for sail vs. payload? Do you include an on-board reactor in case of catastrophic power outage or do you rely on generating power off the laser? How do you deal with abrasion of the sail material?

Yes, we both seem to have our favorites. Yours is just as fictional as an NSWR, at least until someone sends a probe to Mars or the moon using a laser sail.

Momentum transfer by laser has been proven in the lab, including reflecting it several times to amplify the effect without cranking up the power. The NSWR has... what?

It's a prompt critical reaction which has been demonstrated (sometimes accidently) numerous times, including:

Los Alamos Scientific Laboratory, 11 February 1945
Los Alamos Scientific Laboratory, December 1949
Los Alamos Scientific Laboratory, 1 February 1951
Los Alamos Scientific Laboratory, 18 April 1952
Argonne National Laboratory, 2 June 1952
Oak Ridge National Laboratory, 26 May 1954
Oak Ridge National Laboratory, 1 February 1956
Los Alamos Scientific Laboratory, 3 July 1956
Los Alamos Scientific Laboratory, 12 February 1957
Mayak Production Association, 2 January 1958
Los Alamos Scientific Laboratory, 30 December 1958
SL-1, 3 January 1961
Idaho Chemical Processing Plant, 25 January 1961
Los Alamos Scientific Laboratory, 11 December 1962
Sarov (Arzamas-16), 11 March 1963
White Sands Missile Range, 28 May 1965
Oak Ridge National Laboratory, 30 January 1968
Chelyabinsk-70, 5 April 1968
Aberdeen Proving Ground, 6 September 1968
Mayak Production Association, 10 December 1968
Kurchatov Institute, 15 February 1971
Idaho Chemical Processing Plant, 17 October 1978
Sarov (Arzamas-16), 17 June 1997
JCO Fuel Fabrication Plant, 30 September 1999

One question, how exactly do you stop your probe if there isn't a laser or a mirror already there?

You bring a mirror with you.

Which I mentioned in the next line that you snipped.

The laser is going to be the easy part (if we're going by current tech); the hard part is going to be getting the kilometers wide sail up there to begin with.

If you haven't solved launching to orbit, you sure as fuck aren't going to other stars any time soon.

Granted.

Power outages aren't a big deal, since you can just fix it and get back to business. Christ, power outages are a much bigger problem when you're on your own. This should be obvious.)

No no, not "whoops the plug fell out" power outages, more like "whoops all civilization just annihilated itself 5 times over in a massive global thermo-nuclear war" power outages. What's worse than being fucked because of a problem 100 feet away? Being fucked because of problem 2.5 light years away, right when you need that power from home to start braking.

What if your NSWR screws up and the salt water goes critical in the tank?

This would only happen if the tank was ruptured somehow. If it happens, you're fucked.

Or what if the nozzle degrades from the passing heat and radioactive materials?

One idea is to run a sheen of pure water over the surface of the nozzle (much as the Orion has a lubricant continuously sprayed on its bumper). The great majority of the radiation will be carried away from the ship VERY VERY quickly along with the massive head of water plasma. Also, you can run a magnetic field around the nozzle and reaction chamber to keep the plasma from contacting the walls, this will keep most of it and its radioactive hanger-on safely away from the nozzle.

The point is, those problems are potentially solvable. No matter how much you try, your idea will always have a 5 light year extension cord. If something happens to home base, your mission is over, and your crew gets to enjoy floating powerlessly in space. Something goes wrong on my water rocket, the crew won't even be around to know it.

Planets and moons in the way isn't a problem too. Odds are it will never happen, and even if it does, just wait for them to pass. Problem solved.

Well if the laser is on Earth or in orbit of Earth it will happen for at least a few days or weeks of the year (the time it takes for the Earth to pass behind the Sun. If you locate your station around say Pluto's orbit to prevent anything big getting in the way, you now have all the fun of building the station out there, plus if you mission is very long you might lose power more often if your station is allowed to get to far away in its orbit. I suppose you could design it as a statite, but then we haven't even built one of those in the inner solar system yet. And how much safety margin will you build into your system to allow for objects interrupting the beam? Too many interruptions of the laser and the ship won't be able to slow down enough.

Course corrections can be done by angling the mirror. All that's left is the beam spreading out, but that's why the sail is so big.

Which will create great forces on your presumably atoms thick sail, how will you prevent it ripping itself apart in the process?

See, you answered the natural concerns a laser-sail raises quite nicely. Destructionator's concept didn't go much beyond "IT'S BETTER WITH LASERS!"

This coming from the guy who didn't go much beyond "IT'S BETTER WITH NUKES".

Yes, but mine has always been "IT'S BETTER WITH NUKES, and here's why." I've given at least some info in every post. For one thing, I linked to a concise description of the overall idea in my first posting. Until this post, your idea was vague, now we're starting to see a few details.

EDIT: Minor correction in Dr. Zubrin's credentials.