dystopic dystopic

bussard ramjets, cryonic stasis, and exoplanetary colonization

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bussard ramjets, cryonic stasis, and exoplanetary colonization

what will it take?

from GalCiv2 Forums
hello everyone,

i'm a bit of a writer, and i can't help but feel drawn to science fiction. that shouldn't be surprising.

lately i've been reading up a great deal on theoretical physics, exobiological speculation, and all that. i was dismayed at first to learn that the chances of faster-than-light travel being physically possible are slim. it was also pretty discouraging when i sat down and looked at the actual speeds that'd be required to traverse sizable parts of the galaxy in a single conscious lifetime. it was a kick when i was down to learn about how difficult terraforming probably would be. but the more i've been learning, the more i've been excited about telling a different kind of science fiction story.

to draw an analogue to our world, the thing that made both the european colonial age and the modern process of globalization have been technology. it's not that we couldn't go to various places around the world before, it just cost too damn much to make anything worth it. i got my BA in sociology, and these sorts of things interest me.

if FTL travel isn't possible, then more than likely it'll be too damn costly to ever colonize beyond our own solar system as the way it's been envisioned in most of the celebrated scifi universes. But there are examples such as Arthur C. Clarke's Songs of a Distant Earth or Sid Meier's Alpha Centauri where humans colonize to escape destruction on earth.

recently i had the chance to meet both Kim Stanley Robinson and Geoff Ryman. Robinson is a hard scifi writer after my own heart; the Mars Trilogy is a really interesting look at our first attempts to colonize within our own star system. Ryman was actually more interesting to talk to, though. maybe because few people have ever heard of him (i was only there because i work at UCSD where he was being hosted). but i actually got to talk to him. he said he thinks we probably won't ever leave our galactic neighborhood.

i'm interested in writing a hard scifi story (or series) myself. i'm interested from a sociological point of view: what would drive us to colonize space? from a writer's point of view, i want to keep the earth around, so i'm not interested in a flight from disaster. what would societies be like after colonies were established? trade would be difficult, but not impossible. same goes for war.

while i'm certainly interested in contributions along those lines, i'm also interested in learning more about the hard science and engineering behind interstellar travel. i've got a lot of questions i haven't been able to answer through wikipedia and google alone. but i'm not about to list them all here.

it seems like a discussion about real ("real") colonization and space travel could use a place on these boards.

i'll kick it off. i've been reading up on propultion especially, and bussard ramjets seem like the most economically feasible option since they gather their fuel as they go - perhaps especially if it could be hybridized with another form such as antimatter-catalyzed fusion. the wikipedia article on bussard ramjets describe that they'd probably need what is essentially a magnetic funnel or ramscoop to gather interstellar hydrogen as propellant.

The mass of the ion ram scoop must be minimized on an interstellar ramjet. The size of the scoop is large enough that the scoop cannot be solid. This is best accomplished by using an electromagnetic field, or alternatively using an electrostatic field to build the ion ram scoop. Such an ion scoop will use electromagnetic funnels, or electrostatic fields to collect ionized hydrogen gas from space for use as propellant by ramjet propulsion systems (since much of the hydrogen is not ionized, some versions of a scoop propose ionizing the hydrogen, perhaps with a laser, ahead of the ship.) An electric field can electrostatically attract the positive ions, and thus draw them inside a ramjet engine. The electromagnetic funnel would bend the ions into helical spirals around the magnetic field lines to scoop up the ions via the starship's motion through space. Ionized particles moving in spirals produce an energy loss, and hence drag; the scoop must be designed to both minimize the circular motion of the particles and simultaneously maximize the collection. Likewise, if the hydrogen is heated during collection, thermal radiation will represent an energy loss, and hence also drag; so an effective scoop must collect and compress the hydrogen without significant heating.


talk about kick-butt imagery! spirals of heated gas careening towards a ship only to be fused and expelled in a jet plume? sweet.

anyway, i've written enough, and i hope it hasn't put anyone off. some of the the community here has proven to be very well read with regard to these kinds of science, so i thought it'd make a great topic for discussion: all things related to space exploration and colonization with reasonable extrapolations of current technology.

my biggest point of curiostiy was with respect to ramjets, so i'll take the kickoff: could the spiral motion of the inbound gas somehow be harnessed to artficially generate gravity by rotating the ship, instead of producing drag?

any volunteers?

final words: i hope no one minds my double-motive. i won't try to steer any dicussion, though if things quiet down i might pose more general questions to keep it going; i encourage anyone interested to pose your own!
off-topic
436,379 views 930 replies
Reply #401 from GalCiv2 Forums Top
does your car go slower because you have less petrol in the tank? Not untill it actually starts running out will there be a loss of power.


a car doesn't require pressure to operate except in the firing chamber.


another thing to consider is that the nuke could refuel in space if designed right. the chemical would require fuel brought to it.
Reply #402 from GalCiv2 Forums Top
another thing to consider is that the nuke could refuel in space if designed right. the chemical would require fuel brought to it.


Well a nuclear reactor is the most enduring mobile fuel source you can get, theres no doubt about that.
Star Control: Origins
Reply #403 from GalCiv2 Forums Top
a car doesn't require pressure to operate except in the firing chamber.


Thats not much different to a rocket. Remember a rocket is propelled by explosive forces, not pressurised fuel.
Reply #404 from GalCiv2 Forums Top
dude this week sucks. hopefully my roomie will take care of our internet today before i get home. all i want to do is nerd up with the computer screen.
Reply #405 from GalCiv2 Forums Top
I feel inclined to point out another potential, and controversial, engine type though.
It's Electromagnetic Drive, thought up by one scientist named Shawyer.
Wikipedia has a little on it: http://en.wikipedia.org/wiki/Emdrive
A paper by Shawyer is here: http://www.newscientist.com/data/images/ns/av/shawyertheory.pdf

The scepticism is based around the fact that it seemingly defies the iron laws of the conservation of momentum. The thing has no moving parts and uses no fuel (but does need power).
Shawyer has made prototypes too, and what's more they appear to work I believe it generated 16mN of thrust with 1kW of power- Tiny, but then that's the prototype.
It's expected to provide a slightly greater thrust then a SMART-1 ion engine, and at a tenth of the mass. Then there's the fact that, if your talking about the massive distances/times associated with space travel, you have a great deal of time for the craft with this drive to accelerate.
Shawyer also beleives it would be possible, with superconducting materials (to preventing heating/energy loss) it would be possible to lift a car.

I'm going to leave it a real scientist to demolish this prospect, I'm just an A-Level student, but I still quite like this idea.
Reply #406 from GalCiv2 Forums Top
Shawyer has made prototypes too


and no one else has been able to re-create them. sounds like the guy just wanted 15 minutes in the spotlight. if his prototype works, i doubt it'd work in space. it relies on the microwaves turning into thrust on one end of the contraption but essentially heat on the other. this works on earth, where there's a relatively high ambient temperature. in space, the heat would be dissipated as IR radiation much more quickly, producing drag potentially equal to any trust it can create.

moreover, just because things have a long time to accelerate doesn't mean engineers wouldn't prefer something that could accelerate much more quickly, even if it meant lower fuel efficiency (and in this sense, converting electricity to thrust means that electrical power is your fuel - just not your propellant)

more to follow with the rather lengthy discussion preceeding this.
Reply #407 from GalCiv2 Forums Top
Yes! They could make it work like a sparkler tho... the nuke fuel being mixed with other compounds to slow down the reaction.


Interesting. A chemical reaction is Much Much different than a nuclear type reaction. We do use mechanisms to control the reactions in modern reactors (I'm not very up on how the mechanism works), so I guess it could be possible to use the reactor as a heat source for the rocket. By controlling the rate of reaction, we could control the thrust fairly effectively. Additionally, I would assume that the thrust/weight ratio would be excellent considering the high temperatures that we could reach using a nuclear reactor.

Carrying fuel for the reactor wouldn't take up too much mass, hence the ramjet idea looks like it has a lot of potential. We could recoup some of our propellent via the intake(s) in the front of the ship. I mean you only really need huge amounts of fuel twice. Once to get moving and once to stop.
Reply #408 from GalCiv2 Forums Top
yay! i have internet at home again.

i'm surprised to an extend that we returned to propultion, but mostly because i thought we'd exhausted avenues of discussion. i've read the dicussion, but trying to reply on a post-by-post basis would be an insane undertaking.

the first time around i became pretty convinced that a directed nuclear reaction (either fission or more likely fusion) would have to form the basis of thrust. the energy released* in these reactions is surpassed only by matter-antimatter reactions, but the problem there is producing antimatter in large amounts is difficult.

*(pop scifi would have it that black holes can be immense sources of energy, but in truth they absorb energy; the only exception is gravity, which is technically a force and not energy, and we don't even have a hypothesis for how to convert gravity into another type of energy AFAIK).

given the relative abundance of hyrdogen in space, it made the most sense to me that fusion would be the optimal source of thrust. i say 'optimal' because, while there might be more efficient propultion methods in a lab, it seems to me the engineering logistics would favor fusion.

broadly speaking, there are two methods of propultion: those that use propellent, and those that convert electricity into some sort of drive mechanism. there's always something that has to be ejected to create movement, whether it's molecules, atoms, photons, or something else. when a drive is said to not need fuel, just a power source, what it really means (in the legitimate examples i've seen) is that electricity is the fuel and photons are the propellant. and when we say that a reaction creates energy, what we really mean is that a reaction releases energetic particles.

one thing to bear in mind when imagining propultion drives is this: the more times you convert energy between the reation that creates it and the energetic particles that actually creat thrust, the lower your overall effeciency ("specific impulse"). most of our current systems to harness energy into electricity operate at under 50% efficiency. whatever the type of propultion used, the real engineering challenge is going to be improving efficiency. this will be in two main areas: energy conversion and drag (a significant consideration for any proposal involving a ramscoop).

i imagine any large-scale ship is going to have dozens of energy reclaimation systems, and i think (technology permitting) a large ship would try to maximally exploit any potential energy source it could along the way. there would be two main sources in deep space: interstellar medium (mostly hydrogen) and EM radiation.

okay... that's enough for now. but there are a few other things i missed that i'll likley chime in on.
Reply #409 from GalCiv2 Forums Top
and no one else has been able to re-create them.


I don't believe any body has tried to recreate them. Shawyer holds the patent for the design, though both NASA and China are trying to buy rights to the EmDrive desgn. At this point nothing much is happening as the drive is being independantly reviewed.

Also of note is that temperature is a bad thing with this drive (which is why an idea has been made to use liquid hydrogen as a coolant for the superconductive chamber, and as a fuel for generating the magnetrons power).

The microwave photons used to provide thrust are trapped inside the chamber, which sounds dubious. Supposedly any attempt to resolve the forces must take into account Einsteins special theory of relativity which says that the microwaves move in their own frame of reference, as if they were independant of the cavity they are trapped in and thus able to exert a force on the cavity.

And engineers will work with whatever is available. If that means a ship with an EmDrive and chemical/nuclear rockets for the best of most worlds, then good.
Reply #410 from GalCiv2 Forums Top
I don't believe any body has tried to recreate them. Shawyer holds the patent for the design


i'm not sure if anyone else has tried either, but the wiki article states, with regard to the drive deisgn and principle, "These results have neither been reproduced by other scientists or engineers, nor have they been published in a peer-reviewed scientific journal."

the way patents work, other scientists are free to try to reproduce results (and in fact encouraged by the general mentality of the scientific community). what the patent means is that no one else can use the design or make money from it, at least not without paying Shawyer royalties.

Also of note is that temperature is a bad thing with this drive


yes, that was my point. heat will build up greatest on the rear wall, where it would diffuse and create drag. here are parts of the "analysis" section on the wikipedia article:

"Any claim of a reactionless drive is treated with skepticism by the physics community, since it violates well-established principles such as the conservation of momentum and conservation of energy, both of which have enormous experimental support.
"Since there are no known phenomena that do not conserve energy, any calculation based on standard physical theory that predicts a violation of energy conservation almost certainly is in error. This is a non-controversial and fundamental fact regarding the mathematical structure of the theories, regardless of whether the theories themselves are or are not correct descriptions of the physical world. Accordingly, the results reported regarding the EmDrive, if true, would demonstrate that existing physical theory (or its application in engineering) is incorrect or incomplete...
"Conservation of momentum is also required and maintained in Maxwell's equations, Newtonian mechanics, Special relativity and quantum mechanics (and their combination, quantum electrodynamics), so this claim cannot be valid unless these well-established physical theories are false or can be otherwise explained in terms within these existing theories...
"Any dispute will be settled when independent observations are able to conclude whether or not the machine works in the way it is claimed" (emphasis added).

so basically, unless this guy has unknowingly discovered a fundamentally knew phenomenon in the physical universe, something about both his calculations and his prototype is wonkey.
if his prototype does in fact create thrust as he describes, my guess would be that it's drawing energy from the immeidatele environment in a way he hasn't accounted for, for example from the Earth's magnetic field, and in a way that wouldn't work in outter space.

And engineers will work with whatever is available. If that means a ship with an EmDrive and chemical/nuclear rockets for the best of most worlds, then good.


this much we certainly agree on, and if there is something behind Shawyer's EM drive (whether he accurately knows what it is or not), i'm sure it could be used here or there. however, i still think for interstellar travel, we're going to want something that can create absolutely massive amounts of thrust. energy efficiency will take a hair-splitting second place in importance, i think. no matter how efficient a drive is, if it's going to take hundreds of years to accelerate to cruising speed, it's not going to be favored over a drive that can less-efficiently harness interstellar hydrogen to create comparatively monumentous levels of thrust. however, within a star system i think efficiency will be most important, and there would be lots of room for competing models and variations on a theme since the time scales involved are so much smaller by comparison.
Reply #411 from GalCiv2 Forums Top
another thing that's occured to me is inviting this group to participate in the critiquing process. specifically i've thought about setting up a website where people can read and respond to my work in progress - after acquiescing to a digital non-disclosure agreement
That would be sweet!


i'm glad you think so, millertime. i was thinking as soon as i had a bit of extra cash (catching up on student loan payments for the next couple months   ) i wanted to secure a URL, probably www.nikonoclasm.org or www.niktionary.org - or both (my first name is nik... i might also try to grab renikulous.org LOL). unfortunately i don't know much in the way of advanced website programming, anything past basic HTML. a coworker of mine said what i was basically describing was a blog by invitation. any advice?
Reply #412 from GalCiv2 Forums Top
Unfortunately I know nothing of The internet other than I plug in my computer and turn it on

I do enjoy how our discussion have formed. It seems we have a few fairly strong models of how a colony would get started.

I was wondering about pre-developement, hypothetically, of course. What would our Solar system be like when we have the ability to send a Big Colony Ship out beyond our solar system? Would we do it ala the Apollo program, with smaller instalations throughout Sol progressing to full fledged civillian colonies on planets and moons(Then taking what we've learned and applied it to our BCS)? I would figure the scientific (or what ever) outposts would be an important first step as we can feild test a lot of proposals and ideas and apply them to a colony. Ie, First a moon base, then a moon colony.

Anyone have any alternative strategies?
Reply #413 from GalCiv2 Forums Top
What would our Solar system be like when we have the ability to send a Big Colony Ship out beyond our solar system?


i just picked that sentence as a jumping-off point, but i'm responding to your post in its entirety.

personally, i think by the time we start colonizing other systems our own solar system will be pretty 'maxed out' - i don't see any economic or sociological reasons to do it otherwise. of course i think probes to other star systems will happen long before we even have a stable colony anywhere else here.

when i say maxed out, i don't just mean that we're exploiting every natural satellite, but i'm also including huge networks of habitation stations. i think the biggest incentive for colonization will be to relieve population restrictions in our home system.

however, getting from where we are not to that point is a real question. if we invested ourselves in it, i think it could happen in less than 500 years, even as low as 100 to be on the cusp. but personally i have a pretty dystopian view of the near future (thus my online handle). if you've ever read Snow Crash by Neil Stephenson (some of the events in the book are campy and fun, and the characterization is basically pantomime, but i think he paints a startlingly accurate view of the near future, and personally i think that was the point of the book).

so the 500 year timeframe doesn't account for the current trajectory of the world. i do think we're heading towards both socio-economic and environmental setbacks, if not full-on catastrophes. i'm definately not about to soapbox on that point, so it'll suffice to say that i think it's a near-future history i could write very well. plus, i don't think we'll seriously invest in life in outter space and on other worlds until we're backed into a corner on earth, so to speak. adapting through technology to our own planet's inevitably environmental changes will, i believe, provide the basis (in both theoretical and applied sciences) for future colonization and terraforming - though i don't particularly think "forging" a "new earth" will ever be realistically possible, or at least economically optimal.

if anything i think it's also likely that we won't want to change alien environments too much - just enough such that we can implant engineered life forms to see what happens, and to turn around and harvest the genetic, enzymatic and other biological resources diverse enviornments can offer (recalling our earlier conversations about the subject - and on that note, if we do find indigenous life on another planet i think it'd be a scientific heyday for centuries). of course, this presumes a change in cultural outlook that hasn't happened yet and indeed might not (i myself avoid making overly ambitious claims about 'human nature', so in that respect i do believe such a change could happen).

as far as the future of human life is concerned, i think it'll be a rare luxury that a human in the future will be able to enjoy open air breathing and the feeling of feet on naturally occuring soil. though on the other hand, given enough time i think it's a statistical certainty that we'll find a planet that'd support the relationship to the natural environment we enjoy (and abuse) now. that's not to say we won't have "earth-like" public places in our various habitation compelxes, but they'll be artificial re-creations, and expensive at that, making them crowded public places (and/or luxuries of upper classes), and far from the open country we can enjoy fairly easily now.
Reply #414 from GalCiv2 Forums Top
I'm glad ,at least somewhat, that we are on similar pages. I too would assume that a good portion of our solar system would be used. I hesitate to say maxed out, as history has shown with the Colonization of the Americas, the home resources don't necesarily need to be totally maxed out, just scarce or unfavorable for certian groups.

While I don't really have a uptopian/dystopian view on Humanity itself, I do recognize and agree, that expansion into space is not recogized by the world as a current pressing need. I think part of that would be technological, (We don't really have very good or efficient space travel technology to do it en mass) and another part is social economics (why would a common man/woman go into space except for tourism?). There's no real incentive for space exploration beyond our current level of sending out probes. Especially when you do compare it to other modern national and international concerns.

I think for a BCS, you'd need significant space infastructure and experience. Not only something like a shipyard/construction site, but just the experience of space travel (what works, what doesn't) beyond our current scope (Ie just how effective would a hydroponic farm be, or water recylcing in the long term?). If we've been sending frieghters between Earth, Moon colony, and Mars colony for 50 years, yea we'd have a pretty good idea on how to build space faring craft and Land-orbit facilites.

just my 2 cents
Reply #415 from GalCiv2 Forums Top
I have been away for awhile, had a long weekend, got a gastro bug which ruined the last day of my long weekend,,,, but got me a day off work as well tho!

and we don't even have a hypothesis for how to convert gravity into another type of energy AFAIK).


hehehe i am going to be a pain here and point out tidal energy!

Oh i am not certain but what about 'sling shot' energy as well?
Reply #416 from GalCiv2 Forums Top
hehehe i am going to be a pain here and point out tidal energy!

Oh i am not certain but what about 'sling shot' energy as well?


hmm, good points. for slingshot momentum, we still have to generate thrust to make it work, otherwise the object just falls. tidal energy is a trickier beast, and you may indeed have a completely valid point. i'll think more about that one, too tired right now.
Reply #417 from GalCiv2 Forums Top
hehehe i am going to be a pain here and point out tidal energy!

Oh i am not certain but what about 'sling shot' energy as well?


Gravity is a force, not a type of energy. In both these cases, gravity is inducing motion, kinetic energy, which we exploit; case a/ it is converted to electricity, b/ it doesn't change form. Really, most of our energy systems have a kinetic energy phase involved. Engines capture the KE of exploding gas with pistons, dams capture waterfalls, windmills capture air, etc.
Reply #418 from GalCiv2 Forums Top
and we use gravity for sling shots. or did everyone forget that.
Reply #419 from GalCiv2 Forums Top
is new horizens supposed to go by any other planets before pluto.
Reply #420 from GalCiv2 Forums Top
Gravity is a force, not a type of energy.


Why is gravity not energy?

Anyhow, Hydro energy relies on gravity to work but indirectly relies on solar energy to replenish the water stored in the dam.

Also tidal energy relies on gravity to work but directly relies on the movement of Earth and the moon to be replenished. I guess that means that our oceans have slowly been drawing energy out of the Earth's and the moon's momentum slowing them down??
Reply #421 from GalCiv2 Forums Top
I guess that means that our oceans have slowly been drawing energy out of the Earth's and the moon's momentum slowing them down??


yes and because of the earths gravity the moon is leaving.
Reply #422 from GalCiv2 Forums Top
and we use gravity for sling shots. or did everyone forget that.


No, we mentioned that one. In that scenario, we are using gravity, but we aren't actually converting it to electricity or anything, so it doesn't apply to what Mystikmind (or whoever he quoted) was talking about.

Why is gravity not energy?


Let me put it this way. Gravity is a force, there is such thing as gravitational energy, but this is really just a way of saying "potential energy caused by gravity". All means we use to capture this energy go through the kinetic energy phase. Dams for instance, hold up water at a relatively high height. This water has gravitational energy, but in order to collect it, we let the water fall through the dam mechanisms, which capture the kinetic energy of the moving water.

So in a nutshell, we can't change gravity straight into electricity, we have to use some sort of mass to fall and then use its kinetic energy.

I guess that means that our oceans have slowly been drawing energy out of the Earth's and the moon's momentum slowing them down??


Technically yes and no; yes the oceans draw energy, but the effects are negligible compared to the kinetic energy of the Earth. On the other hand the net energy of the system isn't lost, so Earth as a whole isn't losing energy, it is just transferred between oceans and other parts of Earth and back.
Reply #423 from GalCiv2 Forums Top
guess that means that our oceans have slowly been drawing energy out of the Earth's and the moon's momentum slowing them down??
Technically yes and no; yes the oceans draw energy, but the effects are negligible compared to the kinetic energy of the Earth. On the other hand the net energy of the system isn't lost, so Earth as a whole isn't losing energy, it is just transferred between oceans and other parts of Earth and back.


good reply. just remember the saying, 'energy can neither be created nor destroyed (newton), only converted to or from matter (einstein).' also, the earth/moon orbits actually aren't stable. the moon will slowly get farther away until it's in a point of... shoot, there's a more proper technical term, but i'll just say equilibrium (to avoid the redundancy of re-using stability). newton's explanations of force make it more difficult to understand the difference between force and energy. in quantum physics, it's easier to understand (sorta, quantum phsyics itself isn't easy to understand).

basically, a force is when two bigger particles are exchanging smaller particles, such as photons, baryons or gravitons; whereas energy is a property of the bigger particles themselves distating their velocity, spin and charge.
Reply #424 from GalCiv2 Forums Top
No, we mentioned that one. In that scenario, we are using gravity, but we aren't actually converting it to electricity or anything,



wrong we are converting it to energy. not electric but it is still energy
Reply #425 from GalCiv2 Forums Top
No, we mentioned that one. In that scenario, we are using gravity, but we aren't actually converting it to electricity or anything,
wrong we are converting it to energy. not electric but it is still energy


sorry danielost, but i believe you're wrong. we're not harnessing gravity to create energy. we're using gravity as a centripidal tether, allowing us to accelerate perpendicular to the gravity well rather than against it, building up thrust during the rotations. we're not creating energy out of gravity, but rather using gravity to make more efficient use of our fuel.