The idea of a ramjet has been around for a long time.
Taking 1 atom/m^3 as giving 10^-9 J by total annihilation (E=mc^2), ten million atoms/m^3 still only gives a thousandth of a joule/m^3.
Each m^2 area on the ship’s surface would pass through 3x10^8 such volumes per second at the speed of light (10^7 at 0.1c), still giving only 10 kJ/s heating each square metre of the craft’s surface - a mere electric bar fire even in our worst case scenario of 10 million atoms/m^3 at c.
Well my ship was 75m^2 so you numbers come out to ~750kJ/s. Seems hot to me, but if you’re able to fund, build and operate an interstellar ship this cannot’ be the biggest problem.
Answer to riddle. The laser beam contains x amount of momentum. The total amount of that momentum must be transferred to the ships there for there is a finite speed achievable.
You may want to, but you won’t make it. The best you could hope for is to have your descendants make it. And as for scientific knowledge, yes there is a lot of knowledge. But there are much better ways to spend our money than spending a huge amount of money for something that will bear fruition several thousand years from now, and won’t be all that much more useful than an unmanned mission. What exactly do you expect to find in another solar system? If we took just one million dollars, and put in an account that yielded just one percent a year, in a thousand years (an extremely optimistic flight time) we would have over $20 billion. Can an interstellar mission do better than that? Could you build a $1 million spacecraft that can get to another solar system in less than a thousand years, and provide a return of more than $20 billion? (More realistic numbers, such as 5% for ten thousand years, would turn just one dollar into a google squared dollars.)
Urban Ranger
Is there some similarity of a ramjet to my proposal that I am overlooking?
Grey
I’m not sure what you’re saying. There’s no need for the beam to transfer all of its momentum to the ships; the beam carries momentum from one ship to another, and the ships can transfer an unlimited amount of momentum to each other without violating conservation of momentum.
Not Because it is easy, but because it is Hawd
I think the technological gains of such a project would be immesurable. Look at all we got from the Apollo missions: Tang, Velcro, Microwave Ovens, Pens that write upside down, Instant Thermometers, TONS of other things I can’t remember right now.
If the mission is ran as a commercial venture, I think just building the ship would make immense amounts of money, from the tech developed.
Also the benefits to science and the world would be immesurable. This would have to be a world wide project, which would foster peace. A huge chunk of the money would be paid to workers, who would then go spend it, improving the economy of the world. Science would benefit, the healing arts would benefit, about the only industry that wouldn’t benefit is religion.
Thats another thing, what do you think the religious fanatics would think of the mission?
Finallly, what if the Sun was going to nova in only a couple centuries, do you think the world would begin the project ASAP?
Quoting The Ryan
And how is this a problem?
[i/]Transfers an unlimited amount of momentum to each ship?* Unlimited momentum, means unlimited energy and it starts to smell like the 2nd law gets chucked. I must be missing something. Care to expand?
I think we should wait for the Aliens to find us and use their uber-technology.
I remember reading about hibernation ships when I was a kid. It talked about taking a trip to a neighboring star that lasted hundreds of years. When the crew finally awoke and got to the destination, they discovered that humanity had already been there for years as technology progressed faster than they did. They “new” settlers had far overtaken the old ship and they were already there to welcome them. Boy, would I be pissed.
So, what am I saying…? IMHO, in our forseeable lifetimes (say, until 2050 or so) do our best to look for planets that may even have life already or can possibly be settled. If we can’t find any within say, 5-8 ly, what the hell are we even talking about building ships for? If we find some that are say within 100 ly, maybe technology in 200-300 years will allow for “reasonable” travel to them. I just can’t see our technolgy progressing enough in the foreseeable future to even make the travel worthwhile, IMHO.
As mentioned earler, why the big rush? Cripes, its hasn’t even been 200 years since sails where the only way around the oceans. Who knows what will be possible in 2250.
Alpha Centauri is only IIRC 8 light years away. At .5c thats only 16 years P-time. at .25c thats still only 32 years P-Time for .1 it would be 80 years P-time.
For all of those, the S-Time would be significantly shorter. Even at .1 c I think a single generation could get there and still be alive.
Anyone know the time dilation formulas and want to work out the S-Time for those speeds?
Also, Sleeper ships could get them there with no problem.
And what about a Spawn ship? A ship that carries genetic material and the fascilities to make clones and “program” memories and knowlege into the clones. The ship is unmanned , but at the proper time it makes a bunch of clones (from many different donars so there can still be a viable Gene Pool). If the programming of brains is not possible, the ship could make the clones say 20 years before it arrives, raise them teach them and train them. If the cloning of humans is not possible, the ship could do it the old fashioned way and instead bring sperm and eggs.
Finally, once a civilisation becomes an intersteller one, with enough colonies, I think that eventually even other galaxies will not be out of reach.
The answer to both questions is if we haven’t killed ourselves and our planet by then
Humanity is never stagnant. Look at our history. When we stagnate, our civilizations collapse. When we explore… well… the sky is the limit when we explore…
Now that we’ve firmly established that interstellar travel will most likely be possible eventually, what do you do about interstellar communication? Obviously, we are going to need to be able to communicate with those of us on different planets or in route. Typical radio waves aren’t going to be fast enough forever… What are we going to do then?
We’re going to be very lonely.
Unless we find ways around information transfer and the speed of light. If you can do that then you potentially have a propellent for your rocketship, and things change.
Seriously, what would be the point? What does it matter if the human genome (specifically the genome, because mass migration of individuals is most unlikely) never leaves the solar system?
Irrelevent. If a species is doomed to kill itself on its home planet, why won’t it eventually do the same on another?
Personally, I am a little more optomistic than that. There might be some scary shit in the future, but I don’t believe that it is going to be the death of us all.
I still think we should wait until we have a large enough grasp on the usable technologies (possibly hundreds of years) before we consider sending ourselves. There is nothing saying we can’t do remote sensing and surveying from here though. I think that would be money well spent.
Presently our space probes use gravity assist, swinging past planets to accelerate the spacecraft, could use the same principal to decelerate an interstellar ship?
Fringe perspective working through reverse logic. The means to interstellar travel is, cheat through moral growth. Here goes.
I once observed several ufo’s in flight: instant changes of direction; no, I’ve never done drugs; no, this wasn’t no stinkin’ planet Venus. From this I deduced the phenomenon was real and made the leap, tenable though not absolute, based on consistency with like accounts, that this behavior (think laws of momentum) was not of our devising and not spontaneous, therefore most likely extraterrestrial. I proceeded to investigate so-called fringe lit and some fluff notwithstanding, found much of it plausible and reasonable, some of it also included explanations of how the traditional obstacles discussed above gets circumvented, and like another above, won’t detail here. I also concluded we are being collectively psychologically prepped and have several times very nearly had full-scale announcement of the contacts we’ve had.
The PROBLEM, of course, is that the answer to Fermi’s paradox is that we’re idiots. The Calvin and Hobbes quote was, “Sometimes I think the surest sign that intelligent life exists in the universe is that none of it has tried to contact us.” Many “average” people are unstable, puerile, shamelessly irrational, or dishonest as all hell, and then there’re the rest of us. The ironic solution, I conclude, is indeed in not technology but work toward collective mental and moral evolution. Indisputably a weird and very lateral approach, but the rest I suspect, however backhandedly, follows in its turn.
Yes I have considered the alternative explanations; no, I didn’t make up the UFO’s bit either. Craft that can turn instantly like that seem quite likely capable of, however phenomenal the distance, distorting the continuum for travel. I just would agree with not letting 90% of our population near the things or their pilots till we’re ready.
The problem is that gravity assist is not very effective for fast spacecraft. An interstellar spacecraft would fly by the planet so fast that there is very little time for gravity to change the course of the spacecraft.
You might think we can do a gravity assist using a star, but that deosn’t work. Gravity assist works by trading the orbital energy of a planet with the kinetic energy of the spacecraft. Think of it as a collision that sends the planet into a lower orbit around the sun, and the spacecraft to a higher orbit. It might work for a binary star system but not a single star.
We would need interstellar travel PLUS terraforming technology
If I were certain the world was going to end I’d just live it up, and not leave descendants.
Indeed, but I still think that a supernova would be but a gentle zephyr to a craft capable of withstanding the forces and energies inherent in practical interstellar travel (even though interstellar hydrogen doesn’t seem too problematic).
The Ryan’s riddle is the essence of how a laser works in the first place. Each reflection involves a loss of energy due to the surface atoms being heated up and subsequently radiating that energy in all directions. Two mirrors 1m apart would experience 3x10^8 such reflections per second - no wonder the light dims to a few photons within a tiny fraction of a second after the initial laser is turned off.
That’s definitely a practical concern, but a more fundamental reason is that you are bouncing light between two mirrors which are moving away from each other. Therefore on each reflection the photons lose energy (redshift).
Another practical concern is diffraction. You can’t have perfect focusing, so you will lose some light.