Hi!

You call that abundant?

I played with some numbers: let's say such a ship could collect 100% of a hydrogen in it's target area, and is moving at 10% C. The collection area would be a circle with a diameter of 100 kilometers. With it's given speed the cylinder the scoop would sweep would have a volume of ~1.0E13. The amount of scooped hydrogen would be 0.00001 g per second. To get to 1 g of the hydrogen a ship would need a sweep area of a whole 10 million kilometers diameter. Now someone please explain how to convince the hydrogen ion to travel 5 million kilometers from the edge od the scoop area to the nozzle of the scoop in less than one second? We can count on max diameter of only 600,000 kilometers, so the amount of collected He would at best be only ~0.005 g.

With such a propulsion I also see three other caveats. I lack hard numbers to prove them, but they can be obtained and put in calcualtions to prove me right or wrong.

1) The radio waves that would be radiated in front of the ship to ionize the hydrogen would also create its own thrust, but in reverse direction. The "thrust" from one radio wave (photon) is negligible, but here we're talking about irradiating 1E18 cubic meters of space, so we'd need one heck of a lot of those photons. Likely we're talking in terawatt ranges here.

2) Speaking of that "heck of a lot of those photons": where we'd get the energy needed to produce them? The yield of a fusion reaction is only a few percent, so I doubt we'd be scooping enough He to maintain it.

3) The last, but probably the most important issue: what we'd do with wasted energy? No machine works with 100% yield, and with "one heck of a lot of those photons" we'd also get one heck of a lot of wasted heat. How will we get rid of that heat in space, where the only mean of coolong is by radiation? What amount of surface would be needed to get rid of it? What meterials to conduct it and sustain those insane temperatures those gigawatts of wasted heat will be generating?

It's nice to speculate about future. I also enjoy reading SF. But when meet with the hard facts, not much survives the contact.

BR, Iztok

Hi!

1) the strenght of the magnetic field falls with the square root of the distance. A magnetic field that will be able to drag ions from 300.000 km distance in one second will very likely crush the ship first.
2) What's the max speed matter can move? That's why I wrote 600.000 km diameter.
3) IMO ions will need to travel really fast, because our imaginary ship is moving with 10% of C. What the scoop will not collect will simply stay behind wasted.


IMO that's BS. The MHD will slow down the expelled ions and this will decrease the thrust of the ship.


Technically speaking yes. But if the interstellar space is really so empty (1 gram of matter in 1e18 cubic meters), then I think it is not even close to be remotely usefull.

Sorry if I'm sounding a bit arogant. I'm not arguing with you. I'm just criticizing the scoop idea you've only quoted, not developed.

BR, Iztok

no no, i actually really appriciate it. i mean, science fiction is always mostly fiction, so while i want to have as best a hard-science setting for this story, i don't expect it to be anywhere near flawless. otherwise i'd just have gone through with my original major (aerospace engineering).

ultimately i agree that i think it's unlikely we'll ever leave the solar system, but i think the reasons are more sociological than technological. so to me, this whole idea is total fiction.



that's a very good point i hasn't thought about. however, option number two is to use an electrostatic field so that ionized particles will head to the ship by mutual attraction. i don't believe such a field would cause the same problems, but i'm no physicist.



well, that's only really getting at half my point. for one thing, any incomming velocity the particles have (vectored opposed to the thrust of the ship) is going to work as drag. so if anything, you want the ions to be on average travelling in the same direction as the ship. the scoop's going to catch them no matter what. it's not designed to act like a magnet, but a wall or force field.

it's the electrostatic field option that sounds more like what you're describing. radio waves are used to postively ionize the gas ahead of the ship, and a negative electromagnetic field is generated, attracted the gas to the drive mechanism.

with the scoop option, from what i understand, it's more like using your own forward momentum to compress the gas into the thrust reactor. you don't need to make the gas head toward you at any speed at all (in fact, if you could somehow speed the gas up in the direction you're going, without generating drag, it'd be more effecient).

bringing in more gas increases your overall thrust, but it reduces specific impulse (fuel effeciency). a ship like this would build up speed very slowly, probably taking years to reach optimal cruising speed. during that time, it'd be running the scoop/static field generators at max, to bring in the most gas and generate the highest safe possible thurst. but after it got there, all it'd need to do is bring in enough gas to counteract drag against ISM.

personally, i don't believe a pure bussard ramjet could accelerate very well, if at all. that's why i proposed hybridyzing it with something like a nuclear pulse rocket (in my particular case, an "antiproton-induced fusion pulse rocket"). during high thrust, interstellar gas is more akin to air than fuel, serving as the mediaum through which the ship "flies." you don't need a lot of gas, just a lot of energy, and you can get that from fusion or even fission. it'd just be a monster of a space craft. it'd probably have a network of field generators of either type, probably both. so while there probably would be one or two central field generators, they might be augmented by a powerful ring extended around the ship. as it stands, i'm imagining something at least a couple kilometers in diameter. it'd have to be if it was going to include a particle accelerator cappable of producing antimatter in appriciable amounts.

running that thing itself would take tremendous amounts of money. i mean energy. heh. the ship wouldn't be fuel-less in a true sense. the electricity would come from fusion reactors, also made possible by antimatter-induction. the same basic nuclear reaction would be the ultimate basis of both thrust and electricity on the ship. the fuel would the the subcritical mass pellets used as fission fuses, so to speak.

maybe the scoop actually functions like a net, letting the pressure build at the bottle neck for a few seconds to accumulate mass, releasing only a tiny amount as plasma; after a couple grams are released, the engine fires a fission fuse pellet and an antiproton burst into the reaction chamber and releases the bottleneck in exquisite timing, creating a fusion explosion directed into useful thrust by the magnetic constrictors. since you're inducing a fusion reaction there's be a net energy gain, right?

i just wish i knew enough about physics to figure out what kind of effeciency would be needed to make such an engine/power deisgn feasible.

...but in either regard, are you at least a little more convinced?   

and also, thanks for joining the discussion.

To answer the problem of space travel how about this: no engines.

It is easy to conceive of a space station that could accelerate some sort of vessel and launch it towards a target. This station would be very large, and probably rotate around an axis to generate the acceleration, slinging the vessel across the cosmos. This is more like what we already do than ramjets anyways, shuttles only burn their engines for a few minutes on a precisely tuned mathematical trajectory and then just ride along. This sort of system would probably have some restrictions, like vessels could only depart during certain intervals where the station and the colony were aligned or something. The vessel would only need to have retro-rockets or parachutes if the destination had an atmosphere, in order to make a safe landing. Colonies would probably receive some supplies from basically no more than containers that were flung in this same way; I can imagine colonists having to go out in jeeps to locate and retrieve crashed supply pods.

   now that's a funny image. i dunno, though. seems risky on interstellar scales. i mean, keep in mind that the sky we see X years old, where X is how many light years away it is. many things could happen between X and now, especially as we go farther and farther away.

i think the chances we'll find a "New Earth" -ever- are slim to none; the chances we'll find it nearby enough that we can just hurl stuff back and forth is also low.

finally, interstellar medium is much denser, which would create eventual drag. it's not really a factor at the low densities and distances inside a star system, but you probably couldn't maintain significant fractions of light speed in deep space from momentum alone. you'd go a long way, for sure. but the statistical chances of something bad happening go up the longer you're out, and if you're going on momentum alone, there won't be much you can do if something does go wrong.

i agree more or less. i'm just trying to figure out what incentive we'd have to sending such ships to other planets from the Sol system, if we're not going to be getting anything in return. so i'm trying to imagine a way that shipping or trade would be feasible, which would thus open economic incentives to colonize.

as for stellar and interstellar empires each would add a lvl of government that we have not known.

Hi!

I see only one return: better chances of mankind's survival.

For all practical purpose there's no econ incentive of colonizing other solar systems: I can't imagine a single corporation that would invest zillions of dollars, and wait several decades to get the first installment back. IMO the colonization will need to be done by government(s).

BR, Iztok

Better motivation: escape from persecution/poverty. A self financed group that wanted to get away from it all COULD. It might be a political group, people fleeing what they see as a doomed earth, or even a corporation that has political asperations (and what would be better than a whole new WORLD to take over?)

Building on the surplus population idea, a government might simply send off undesirables (prisoners, people they are persecuting, terrorists, whatever). Its a way to get rid of all these people in an (arguably) humane way that doesn't NECESSARILY involve killing them, and gets lots of prestige and good PR while you're at it.

now that's an idea. killer robots? tax collectors? english teachers? heh.



IIRC there's an international treaty, similar to the one concerning antarctica, that states no government can own celestial bodies. there's also some random dude out there who said, well, since i'm not the government, i'm going to claim EVERYTHING. he's selling plots of land on the moon cheap. i'm not kidding (though i might not be remembering correctly).



LOL... last night i was modding the minor races because i'm tired of them being generic (and bad). i was using Formis's race portraits and movies (in the library), but there weren't enough to make 8 minor races without one of them being/looking human (or altarian). so i called them the Free Quebecois, and in their description i wrote something like "In 2017, the population of Earth unanimously voted to send the population of Quebec into deep space, and to give the land to the Palestinians. Now they're back, and this time they're annoying the whole galaxy."

so, i don't think overpopulation is a reasonable issue. it'll always remain cheaper to build orbital space stations or a dyson bubble to house the masses.

profit seems like a tenuous reason. we'd have to run out of something pretty damn valuable to start looking for it in other star systems.

exploration and curiousity would require some major social evolution. true, people are curious. but i don't think any sane person would ever see what'd happen if he lit a million bucks on fire, just out of curiousity. of course, whether our leaders actually are sane is another question.

better insurance for the survival of humanity would also be the same. while i don't think anyone (outside of comics and James Bond movies) want to eradiate the human species, few people think on that kind of species level as a matter of practical reason. plus, IMO the process of aquiring power and wealth requires a personality that's a bit callous and short sighted.

i think in either regard it'd require a HUGE propoganda campaign. the powers that (will) be would have to justify the expense and danger to at least some of the public. they'd also have to attract colonists (though, that could be done with force if needed).

...this is getting me thinking. what if colonization had some dark, alterior motive? what if 10,000 people boarded a colony ship on the assumption they were going to spread humanity, but there in fact were dark alternatives the government/big business had in mind?

what if researchers discover seemingly intelligent radio wave patterns from a nearby star. the government or whoever covers this up, and announces a colony mission to the same star. their goal is really to eliminate a potential threat preemptively.

hmmm.... but even war boils down to resources and economic incentive. sorry if anyone feels otherwise; i'm pretty cynical about things like that. still, that's be an interesting idea to play with.

space stations only have to be big enough to hold 1 family.

make them moduler so that you can stick them together to share resources.

as for iron. mars seems to have a lot of it. at least enough for it to rust on the surface.

You are correct. But one must remember that the intent of that treaty was primarily scientific in nature. Antartica has no known resources that we need - Same with other celestrial bodies (for the time being anyway). If there were an attempt to colonize Antartica (aside from the current scientific bases there), the setting up of the colony itself would imply that there must be a government controling the colony, whether truely autonomous (meaning the colony is acutally its own nation) or a subset of another nation (Us, china, Russia, etc).

I think the treaty stating that a gonverment cannot lay claim to a celestrial body goes out the window when a civillian colony (not just an outpost) is founded, as some form of governence is implict in the foundation of the colony.



I also agree but for a simpler reason. Its even cheaper to war over resources and elimiate good chunks of population that way, with out need for space stations. Besides overpopulation is not "where do you stick the people?" but more of "where do we get the resources to ensure their survival?" It'd probably be more likely that instead of moving people to space (where they are still consuming resources from earth building large spacestations and feeding the people and such), we'd move resource generators to space (ala huge hydroponic farms, power plants, etc). With automation, etc you would have relatively few people in space.

I thnk any natural progression into space on teh part of humanity, will be very self centered. We go to space for the benifit of our planet/species. Overpopulation? grow food elsewhere and ship it to earth. Harvest water, minerals, fuel from other sources once we run low on earth. Again - Earth needs/wants it - Profit. Propaganda wouldn't have to be huge - Look at the 1848-9 Gold Rush in the US. People thought they could get rich and so they went. Same thing with the .com Boom several years ago.

All you really need is possible hope along with some "proof" of success. Life suck? Strike it rich with a Hydroponic farm on the moon! Look at these pioneering millionares who started the first Farms! As long as starting your own farm (or boarding the colony ship) is economically feasible for the masses, you'd have people lining up! Adventure, a new life, Good cahnce of huge success!