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!
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Reply #426 from GalCiv2 Forums Top
A slingshot maneuver around a planet changes a spacecraft's velocity relative to the Sun, even though it preserves the spacecraft's speed relative to the planet (as it must do, according to the law of conservation of energy). To a first approximation, from a large distance, the spacecraft appears to have bounced off the planet (physicists call this an elastic collision even though no contact actually occurs).


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i don't think you have to worry about the conservation of energy if your not using energy
Reply #427 from GalCiv2 Forums Top
That's merely stating that the net effect of acceleration is valid as energy is conserved in the system. That means that the BCS isn't magically gaining velocity (relative to the sun) for no particular reason. Everything uses Energy. But, as your quote states, The law of conservation of energy implicitly states that Energy is not being created (or destroyed). The energy already exists in the BCS, as Potential Energy. The force of Gravity merely converted this Potential into Kinetc, as Millertime explained earlier.
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Reply #428 from GalCiv2 Forums Top
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.


There will still be energy lost via 'friction' of the movement of the water.

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.



I would think the spacecraft in a slingshot manouvre would be taking potential energy from the velocity of the planet relative to the spaceship.


Reply #429 from GalCiv2 Forums Top
There will still be energy lost via 'friction' of the movement of the water.


this isn't energy loss in a sense of the energy being destroyed or somehow disappearing, it's energy transfer. if you want to look at an engine or generator as a closed system, you can refer to it conventionally as energy loss - but that doesn't mean the energy disappears, only that it goes somewhere or does something that's not useful to you.
Reply #430 from GalCiv2 Forums Top
this isn't energy loss in a sense of the energy being destroyed or somehow disappearing, it's energy transfer. if you want to look at an engine or generator as a closed system, you can refer to it conventionally as energy loss - but that doesn't mean the energy disappears, only that it goes somewhere or does something that's not useful to you.


Well with regard to tides, the energy loss I refer to is the energy loss from planetary momentum via friction of moving water.

I do understand what is meant by the fact that energy cannot be destroyed. Although most energy ends it’s life as heat, and in a sense is destroyed through what I call ‘infinite dispersal’. Since the universe is infinite, it can never be totally filled with even the lowest levels of heat.
Reply #431 from GalCiv2 Forums Top
One thing that we haven't mentioned, and I'm not sure how relevant it would be to space only flight, but It may be significant to the slingshot, would be the Mass of the ship.

With our current shuttle tech, we jettison fueltanks, engines, etc as we break orbit. This reduces the ships mass, making it easier to propel and escape Earth's gravity (no dead weght to pull against gravity) With the slingshot, we'd still have to pull away from the sun's gravity (the sling shot orbit) while thrusting.

If we're talking about engines that produce large amounts of thrust for a short amount of time or use good amounts of fuel/propellent (like our nuclear rocket), would it make more sense to Have our colony ship use Engines/Boosters that the ship can drop (making it easier to escape the slingshot orbit) instead of (or in addition to)a central engine on the ship?
Reply #432 from GalCiv2 Forums Top
If we're talking about engines that produce large amounts of thrust for a short amount of time or use good amounts of fuel/propellent (like our nuclear rocket), would it make more sense to Have our colony ship use Engines/Boosters that the ship can drop (making it easier to escape the slingshot orbit) instead of (or in addition to)a central engine on the ship?


Once the engine has gained it's speed, it has momentum already and therefore no need to be dropped. Unless futher acceleration from other engines was going to take place Or the value of it's momentum was less than it's gravitational pull if heading away from a strong gravitational force like the sun, although you would still have to have other engines in reserve if that was the case.

Reply #433 from GalCiv2 Forums Top
maybe use that momentum as it heads into jupiter and at the mid point drop those engines reducing its mass. thus reduceing the amount of speed loss as it leaves jupiter.
Reply #434 from GalCiv2 Forums Top
maybe use that momentum as it heads into jupiter and at the mid point drop those engines reducing its mass. thus reduceing the amount of speed loss as it leaves jupiter.


There is no benefit at all to reduce the mass of a spaceship unless it plans to use engines for some reason
Reply #435 from GalCiv2 Forums Top
There is no benefit at all to reduce the mass of a spaceship unless it plans to use engines for some reason



i was thinking reduction of mass thus maintaining more speed.
Reply #436 from GalCiv2 Forums Top
or you could keep the engines and turn them into living quarters or hydroponics labs.
Reply #437 from GalCiv2 Forums Top
i was thinking reduction of mass thus maintaining more speed.



If you dropped a part from a spaceship traveling in space, that part would then follow aling side the spaceship exactly the same as the ship (not withstanding seperation forces) no matter what planets it was heading towards or away from. There is no benefit to changing mass at all. Not unless you plan to use engines on the spaceship to change its speed or trajectory.
Reply #438 from GalCiv2 Forums Top
or you could keep the engines and turn them into living quarters or hydroponics labs.


yep and then dump them when you want to start decelerating to land on a planet,,, or put them in orbit to act as a permanent space station.
Reply #439 from GalCiv2 Forums Top
Once the engine has gained it's speed, it has momentum already and therefore no need to be dropped. Unless futher acceleration from other engines was going to take place Or the value of it's momentum was less than it's gravitational pull if heading away from a strong gravitational force like the sun, although you would still have to have other engines in reserve if that was the case.


not quite. gravity is an accelerating force, which means that its momentum would diminish. if you reach a critical amount of thurst, the momentum would carry it out of the solar system, yes.

but along the lines of the general discussion, it'd make the most sense to construct a large ship on the fringes of the solar system and shuttle people to and from the big ship with smaller ships, i think.
Reply #440 from GalCiv2 Forums Top
folks your forgetting the speed of voyager 1. mans fastest space craft. it wasnt the fastest to leave earth that was new horizen.
Reply #441 from GalCiv2 Forums Top
but along the lines of the general discussion, it'd make the most sense to construct a large ship on the fringes of the solar system and shuttle people to and from the big ship with smaller ships, i think.


as i said earlier. three ships for a trip to mars, or anywhere. a space plane it doesn't pull anymore Gs than a jet. ship two a cruise liner designed to get you where your going. ship three one that can land on its tail and then be used to make a run way. and then you go back to ship 1.
Reply #442 from GalCiv2 Forums Top
When I was thinking of jettisoning tanks/engines I was thinking in terms of continual thrust while jetisoning (pretty much just like the space shuttle). Why thrust dead weight as we start a sling shot? In addition, this would make the ship easier to slowdown when it reaches its destination in terms of momentum not to mention periodic pre-programed busts of thurst to maintain/adjust course or heading.


but along the lines of the general discussion, it'd make the most sense to construct a large ship on the fringes of the solar system and shuttle people to and from the big ship with smaller ships, i think.


That makes a lot of sense in terms of the ship being able to escape the solar system, But that is an awfully large distance from (what would presumably be) the manufacturing and population centers of the Solar system - Earth, Mars, etc. Not to mention that the farther a construction project is from is resources, the more complicated it gets in terms of Logistics and Supply. One small screw up (wrong sized beams) could literally halt the project for years as new parts have to be made and shipped from scratch, not to mention restarting derricking and hoping everything is still in proper order.
Reply #443 from GalCiv2 Forums Top
not quite.


huh? what's 'not quite'?
Reply #444 from GalCiv2 Forums Top
folks your forgetting the speed of voyager 1


how is that relevant to the discussion?

as i said earlier. three ships for a trip to mars, or anywhere. a space plane it doesn't pull anymore Gs than a jet. ship two a cruise liner designed to get you where your going. ship three one that can land on its tail and then be used to make a run way. and then you go back to ship 1.


i think you'll need to explain that a little more if you're inviting us to discuss your idea. your language is a bit unclear, at least to me. i'm not interested in trying to convince everyone else that my ideas are right; i'm interested in discussing everyone's ideas. i just can't understand yours very well because you use a lot terms idiosyncratically without explaining what you mean by them in simpler terms.
Reply #445 from GalCiv2 Forums Top
space flight will not become truly available until grandma can go. most grandmas cannot take a shuttle flight because the Gs are to high.


however a space plane doesn't pull anymore Gs than a jet plane and most grandmas can fly.

a space plane can reach 90% orbit thus making the need for rocket fuel 90% less ie a lot cheaper.

a cruise liner because you don't want to sit in a chair for 6 months. flight time to and from mars.

a tail lander for the first trip because there are no runways for the space plane which could be refueled with rocket fuel.

the tail lander would need to carry a bulldozer and cement maker to make a run way for the space plane to land.
Reply #446 from GalCiv2 Forums Top
folks your forgetting the speed of voyager 1


how is that relevant to the discussion?




voyager 1 used sling shots to get it where it is. you cannot speed up without an energy source this would be gravity. you also cannot change direction without an energy exchange.
Reply #447 from GalCiv2 Forums Top
i got an interesting idea....

a swinging arm space station! A space station with a long swinging arm that rotates at high speed with which ships can dock without having to decellerate after arriving from another world. The arm would have to be long enough so that gravitational forces would not be too high for the passangers (if that is at all possible?) yet maintain high speed to slingshot the spaceship back the way it came.

Or i guess you could simply put a space station on a fast orbit around the planet which could achieve the same thing!
Reply #448 from GalCiv2 Forums Top
when you rotate a space station the force goes outward. meaning that the middle of the station the part not rotating fast would be where the lack of gravity would be. and the faster you rotate the higher the force is.
Reply #449 from GalCiv2 Forums Top
when you rotate a space station the force goes outward. meaning that the middle of the station the part not rotating fast would be where the lack of gravity would be. and the faster you rotate the higher the force is.


That is correct. However what i am thinking is that the longer the rotating arm is, then the faster it would be traveling at the outward edge which would accomodate a fast moving spaceship without causing too much gravity. Of course if you wanted to preserve extremely fast spaceship speeds then the arm may have to be hundreds of kilometres long!... or have people use that liquid oxygen technology so they can withstand the gravitational forces.
Reply #450 from GalCiv2 Forums Top
However what i am thinking is that the longer the rotating arm is


the only thing this would achieve is to change the liner motion into circuler. which i believe will through all of that forward motion into the outward side of the ship. like when you go around a curve in a car at 60 miles an hour.