Plan an Interstellar Mission!

[Nicholander]

I did, but I thought it might be Freudian, like you really believe reaching habitables around other stars is impossible.

I think it is possible, but in this 100 year time frame and Earth becoming uninhabitable, it's not really possible.

[dryer_lint]

1) Get rocket

2) Propel out of solar system

3) Bring along copy of KSP to entertain myself

4) Wait

This is a good plan. I like this plan.

[GreeningGalaxy]

As much as I don't like the idea of having to generate quantities of antimatter measured in thousands of tons, that's probably what you'd have to do. I hope you can work fast during that short century, because you'll need every minute. Maybe you can build some kind of particle accelerator station close to the sun?

Laser sails will cut down your required mass ratio substantially, but that leads to another problem: if disaster is going to befall our solar system (I'm assuming it's the whole solar system, or else moving somewhere like Mars looks more attractive than trying to go interstellar), how long do you expect the laser battery to remain operational? If it's not going to last centuries, you'll need to carry most of the energy for your trip with you, in the form of more antimatter. Interstellar spacecraft design is hard.

Of course, the better your cryogenic stasis technology is, the less antimatter you'll need - apart from staying alive, there's no particular rush once you've departed Earth.

[SargeRho]

Build magnetic traps in orbit around Saturn, Jupiter and Earth.

[cicatrix]

That's not the point of this thread - the premise is that the Earth and solar system as a whole are no longer viable and have to be abandoned. What do you do then?

Actually I read a Sci-Fi once where the sun was dying and humanity decided to pack and leave... they mounted huge engines on the poles, took Earth from its orbit and headed towards the nearest yellow dwarf they thought was good enough to replace the Sun.

As they flew farther they had to hide underground since the atmosphere froze. In some time they arrived to a new solar system, found an orbit and injected themselves into it. Actually the place was already inhabited but we resolved this misunderstanding

[Rakaydos]

Actually I read a Sci-Fi once where the sun was dying and humanity decided to pack and leave... they mounted huge engines on the poles, took Earth from its orbit and headed towards the nearest yellow dwarf they thought was good enough to replace the Sun.

As they flew farther they had to hide underground since the atmosphere froze. In some time they arrived to a new solar system, found an orbit and injected themselves into it. Actually the place was already inhabited but we resolved this misunderstanding

I read a varation where they put a fusion rocket engine on Uranus, fed by the hydrogen atmosphere, and gravity-tractored earth into a differnt orbit. Because you cant beat a gas giant for fuel fraction.

[Rath]

The 1% gets is about to go into space then three is a giant riot and the 1% and out ticket off the planet is destroyed (then massive amounts of turmoil when people notice they are all dead)

[YNM]

Actually I read a Sci-Fi once where the sun was dying and humanity decided to pack and leave... they mounted huge engines on the poles, took Earth from its orbit and headed towards the nearest yellow dwarf they thought was good enough to replace the Sun.

As they flew farther they had to hide underground since the atmosphere froze. In some time they arrived to a new solar system, found an orbit and injected themselves into it. Actually the place was already inhabited but we resolved this misunderstanding

That'd be a very inefficient way to change orbit through...

Me ? Let's go to Enceladus or Europa, I guess ? After all, why would Sun be unusable ? A ball of gas that massive should generate a damned amount of heat within... and if the Sun were to be converted into non-star object, it'd be not that fast. Needs a hell more amount of energy to compress it...

If that's the scenario, I'd want it happened 70000 years ago. Then hop off to this star....

[magnemoe]

- - - Updated - - -

Have you ever heard of a little thing called, an Orion Drive?

Potentially could go 10% of the speed of light.

I have read that calculations myself and it seems a bit off, as somebody said above an good fusion drive would be capable however you would not get 0.087c exhaust velocity as lots would be radiation in all direction. Now the orion is far worse, its not an good fusion drive, the bombs would need an high explosive trigger, the fission part then structural parts all who would be heavier than the fusion charge even on multi megaton bombs.

[Bill Phil]

I have read that calculations myself and it seems a bit off, as somebody said above an good fusion drive would be capable however you would not get 0.087c exhaust velocity as lots would be radiation in all direction. Now the orion is far worse, its not an good fusion drive, the bombs would need an high explosive trigger, the fission part then structural parts all who would be heavier than the fusion charge even on multi megaton bombs.

The bombs are only a few kilotons for the small versions.

Each bomb has a shaped charge to direct almost all of it to the pusher plate.

[rkman]

NASA has thought about it.

http://www.nasa.gov/centers/glenn/technology/warp/scales.html

- destination: Proxima Centauri (closest neighbor)

- payload mass: one Space Shuttle

- travel time: 900 years

- amount of fuel needed:

conventional technology: not enough mass in the known universe

nuclear fission: one Billion oil tankers

nuclear fusion: one thousand oil tankers

[magnemoe]

The bombs are only a few kilotons for the small versions.

Each bomb has a shaped charge to direct almost all of it to the pusher plate.

Yes, larger orions will use larger bombs this makes them more effective, even if you manages to absorb all of the energy (shaped charges is 50% but this might be different for nuclear)

However the exhaust velocity will hardly be an high faction of c and the orion drive itself is heavy.

[Rakaydos]

Yes, larger orions will use larger bombs this makes them more effective, even if you manages to absorb all of the energy (shaped charges is 50% but this might be different for nuclear)

However the exhaust velocity will hardly be an high faction of c and the orion drive itself is heavy.

Orion is basically a solar sail that brings it's own sun. Of the energy directed at the pusher plate, 100% of it pushes the craft foreward, plus call it 50%+ of the rebound energy. Having the shape charge direct 50% of the bomb's power at the pusher plate lets you get almost 100% of the bombs power.

[Robotengineer]

Doing some moderate research on this, is Project Icarus a good research organization?

[AC656]

So it looks like you guys could use this:

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/20238/1/98-1132.pdf

guy at nasa has thought about this. I think my favorite is the Bussard Ramjet although haven't really thought about it a lot or search about it so don't know if it is the best one. Solar sails might be useful. The problem is that realistic interstellar ships get insanely huge very quickly.

Also if we find out we have 100 years we might want to trow a bunch of money at AI research and see if it can help us.

Edited February 24, 2015 by AC656

[magnemoe]

So it looks like you guys could use this:

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/20238/1/98-1132.pdf

guy at nasa has thought about this. I think my favorite is the Bussard Ramjet although haven't really thought about it a lot or search about it so don't know if it is the best one. Solar sails might be useful. The problem is that realistic interstellar ships get insanely huge very quickly.

Also if we find out we have 100 years we might want to trow a bunch of money at AI research and see if it can help us.

Bussard ramjet is extremely hard to build, h2+h2 fusion itself in very hard.

Wonder if you could simply accelerate the ions, or if you will lose more momentum gathering them than you gain from this. You could beam lots of the power.

However the magnetic scope should work well for braking reactionless. This is nice if you already have an large structure.

[megatiger78]

the IXSclass.

[Newt]

The problem is that realistic interstellar ships get insanely huge very quickly.

Well, yeah. But I am not entierly sure that some of the insanely huge components of solar sails (for instance) would be impossible. On Earth, big structures are heavy, hard to build, complex. If they are thin and light, they are frail, usually short lived. In space it does not have to work like that, it would not be definitely simple to build and fly a 500m radius sail for a spaceship, but it might be simpler than at fist seems probable. Then again it may have challenges and risks that we do not really yet anticipate.

[Rune]

Interstellar ship? Well, the first thing is to decide if we go for crewed interstellar ship. Since the travel time means that pretty much you have to have the ability to rebuild the ship before the braking burn (show me the complex piece of harware that you can be sure will work after 100 years), I'd say, right now and until we built AI's and way more advanced robots, crew is kind of a requirement to operate in the target system. The OP also forces the issue by invoking a doomsday scenario, but as you can probably see if you think about the problem a bit, a crew is a nice thing anyway. What are we going to tell the robots to do when they get to the target system, if we don't know what's there? What is something new has to be built there, or something repaired along the way?

So considering the lenght of travel and the requirement to carry crew, I'd say payload is pretty simple: a few tens of millions of metric tons of O'Neill-style rotating habitat, with all the resources and the closed loop biosphere contained inside. That way you don't care about the lenght of the travel, or the habitability of the target system, just that it has resources to remass and refit your mobile home, probably even replicate it. Likewise, you don't have to invoke fictional technologies like suspended animation or an exotic manteinance system.

Of course simple does not mean easy. Moving all that mass to a decent speed (say, 1-10% of c) and the braking at the other side is a tall problem. The way I see it, either we invent a magical fusion reactor with near-perfect efficiency (and I doubt that very much), or radiator requirements will pretty much kill our design. Those fancy torchships (or antimatter ships) with a relativistic exhaust velocity are fine and dandy, even may even be buildable some day, but no matter which one you pick, they need absurd jet powers to speed up to cruise speed in a reasonable time (say, more than a few years under acceleration with the engines going at 100% power is probably not viable), and if even a fraction of that humongous amount of energy gets into the payload as waste heat, it'll cook the crew in no time, and melt the hull soon thereafter.

No, sadly the only realistic drive system is an Orion-like contraption. Even better, a Medusa type arrangement if we can make the thether system work, since it saves the humongous shock absorbers. That way the propulsion chamber is external, and the exhaust takes away all its energy but a tiny fraction, which is invested in ablating from the pusher plate/sail to contribute to thrust. According to the few sources availabe, 5-20% of c is achievable as effective exhaust speed dependign on a bunch of assumptions (including pulse unit yield but basically "bigger is more efficient"), so cruise speeds of 2.5-10% of c with boost phases under a year or so (high TWR!) seem achievable. That means travel times on the order of centuries, not millenia, and on the same order of magnitude as pretty much all the other options, once you go over a single human lifetime.

With that, you basically pack your civilization in the smallest possible replicable package, and just take your home with you like a snail, plus the resources to support you as you go (you need something like 20mT/square meters of shielding to properly protect from cosmic rays, might as well make that big resource stores). And what do you do while you are travelling between stars? Well, you build the thousands of thermonuclear pulse units you need to brake at the other end and service the nuclear reactors providing power for the biosphere, of course. I hear uranium ore makes for an excelent cosmic radiation shield... at least as good as dirt .

And how to build this monstrosity? Well, not anytime soon and not in a gravity well, that's for sure. Probably close by to the group of asteroids we harvest to provide the construction materials... and make the robots to provide the actual labour. Has anyone detected a big heavy metal asteroid with loads of uranium yet? xD

Of course by the time we get around to this we might have already solved the aforementioned problems of complex automated replicating systems A.K.A. AIs and robots, and perhaps upload ourselves into them or some other sci-fish stuff. But if we ever want to move Earth's biosphere to other stars, this will still be the best way probably... all it takes is a few asteroids, a labour force, and time.

Rune. It may be 60's technology, but 21st century industrial automation is what makes it actually doable.

[Robotengineer]

Interesting thoughts Rune. Some of the doubts I have about Nuclear Pulse Propulsion are precision and landing. How do you mange to be accurate within even a few thousand kilometers of the target star at interstellar distances? How does one land the equipment on the target planet with NPP? I think a better option would be a series of smaller ships, like the Endurance from Interstellar, fitted with Q-Thrusters or nuclear fusion engines (like project Daedalus) instead of Magnetoplasmadynamic thrusters (MPDT's?). I think giant O'Neillian style colony ships would take too long to build, on the timespan of centuries, whereas a couple of smaller ships could be built by the end of this century.

[YNM]

Precision at interstellar distance is actually a bit easier. Most problems don't came unless your travel takes million of years (well, enough to take you around the galaxy halfway by galaxy's own rotation)... A small fraction of that should be easier. Just that proper motion, radial motion, and distance measurement have to be very precise first at all (Gaia mission comes to mind. Probably that's what the mission for haha). Those should be enough for planning trajectory and correction maneuver.

But if the scenario were real, I wish there's this star (or other galactic object, be it brown dwarf or stellar remnant) that pass us less than a light year... So we only need to "hop". Then hop off at another site... Wonder if any sci-fi story ever uses that kind of thing ? Could we use that to escape Sun's demise as it evolves off, as some statistic shows it happens probably as much as one in a hundred thousand years ?

[Rune]

Interesting thoughts Rune. Some of the doubts I have about Nuclear Pulse Propulsion are precision and landing. How do you mange to be accurate within even a few thousand kilometers of the target star at interstellar distances? How does one land the equipment on the target planet with NPP? I think a better option would be a series of smaller ships, like the Endurance from Interstellar, fitted with Q-Thrusters or nuclear fusion engines (like project Daedalus) instead of Magnetoplasmadynamic thrusters (MPDT's?). I think giant O'Neillian style colony ships would take too long to build, on the timespan of centuries, whereas a couple of smaller ships could be built by the end of this century.

Well, I am talking about something a few kilometers in diameter, under rotation to give the crew a comfortable 1G environment. So obviously landing this anywhere is a no-go, if only because the structure likely won't be designed to support it's own weight in that axis. Shuttling should be done with auxiliary vehicles, of which you can probably fit a small fleet inside, or just build them at the target system to gather resources. This kind of thing should have the technological capabilities to build copies of itself by eating rocks in the destination, ideally. Remember, we are tackling big scales here, so let's think big in every way.

And of course, it'll need course corrections along the way, but we already measure stellar velocities from light years away with an astounding precision. An Orion drive can be "gimbaled" for control, BTW, or at least an equivalent effect be achieved, plus you will have auxiliary reaction control systems, of the proper titanic proportions. The ship has literally decades to refine their trajectory and make adjustments at the appropriate times, too. The don't just "launch and be done with it", this is a very long travel during which they will be very busy taking care of and improving their habitat, doing interstellar science, having and raising children, and in general doing their usual human things, only in the void between the stars. I imagine the interest in the destination system would mean that the crew of one of this ships should produce a few generations of very fine exoplanet astronomers. Of course, they would also be in near-constant contact with Earth (if it's still there talking), keeping up to date in the general flow of things, albeit with a considerable lag (short of like writing letters across the Atlantic in the age of sail).

The propulsion comments, though, are plain wrong. There is no such thing as a Q-Thruster right now, only some funky experimental results and a quasi-scientific description. No theory, no repeated results, just the barest hint of something being a bit weird with a certain test setup. Let's stick to realistic stuff, and leave sci-fi aside. MPD thrusters do exist, at least at the prototype stage, but leaving aside the fact that 50% of their input power ends up as waste heat and not jet power... because if you need a jet power on the order of Petawatts, how are you going to a)generate twice the amount, and get rid of half of them without frying yourself? Ok, so as I was saying, leaving that aside, you still have an specific impulse at least an order of magnitude smaller than an Orion Drive, which means a cruise speed an order of magnitude lower. Consider that an effective isp of around 300.000s (Vex~1%c, about what Orion gives) gives you a travel time of around one light year per century. MPD's get around 10,000s in comparison (3 millennia per light year), and their TWR is lower than ion engines. Yeah, nope.

And let's not get into the TWR of the whole system with the impossible humongous radiators and powersource, because that would imply this is something sane enough to consider. Those are the reasons antimatter and fusion engines are also out for this excercise IMO, their up-to-now-impossible engineering challenges like efficiency and cooling (and in the case of fusion, just making the thing light up for starters). But the other propulsion methods don't even get that far in the analysis with the theory alone.

As to size, and why so big, the minimum size is the one where you have the facilities and crew to rebuild the ship along the way. Because, again, after the first century, pretty much no original equipment will remain operational. I don't think the vague "Endurance-style" comment really fits the bill for a true interstellar mission...

Build time? Well, that's a guess. But I'm going to guess if you worked out how many tons of metal we turn into cars in a single year, you would get a number that would build one of these babies in the required time. Your typical O'Neill cylinder masses a few megatonnes depending on size, so let's say 10 megatonnes for a rough order-of-magnitude approach, and mass ratio 5 to account for the "fuel"... 50 megatonnes of steel, uranium and (mostly, really) assorted dirt and light gases and hydrocarbons. (Actually, I searched for it. In 2013, the world produced a bit under 90 million cars. If we approximate the mass of a car to around one metric ton, we get a bit less than 2 interstellar colony ships worth of processed material every year, spent on driving around the surface of our planet) How long to process that into an interstellar ship, then? Depends entirely on what is your production capacity.

So, to get rid of the last vestiges of your planetary chauvinism (don't worry, we all start that way), I would further point you to this helpful article on space colonization and interstellar travel: http://www.thespacereview.com/article/1792/1.

Rune. Enjoy!

Edited February 24, 2015 by Rune
My writing was abysmal, now it should be a bit clearer :)

[Robotengineer]

I can now see why you are opposed to interstellar travel only for the purpose of colonizing planets. I can see the pros of the O'Neil type solar system colonization, but it (seems) nearly impossible with currently technology, not to mention the current state of government run space programs. How could it be done?

[benjee10]

I can now see why you are opposed to interstellar travel only for the purpose of colonizing planets. I can see the pros of the O'Neil type solar system colonization, but it (seems) nearly impossible with currently technology, not to mention the current state of government run space programs. How could it be done?

I think it could only done with a motivator like an end-of-the-world scenario, and even then with difficulty. You'd need some sort of incentive to get people invested in it even though most of them will never actually fly interstellar. Perhaps the craft would carry millions of frozen embryos donated by the public, so everyone would be involved because it would literally be their childrens' futures.

Thanks for all the great replies in this guys. Been great reading them all!

[Robotengineer]

If humanity waits for an end-of-the-world type thing, we won't have enough time to build something that has a high chance of succeeding. It would be in the best interests of humanity as a whole to have a space infrastructure already in place before a catastrophe. Our terrestrial infrastructure is in poor condition in parts of the world and we haven't figured out how to fix/fund it, how then do we manage create the public interest/political will/financial incentive to build a space infrastructure without a crisis?