In a recent GD thread there was a discussion about whether its possible to use todays technology to take a crew to the nearest star and have some of the folks (or their decendants) arrive still alive and kicking. The general concensus seemed to be that its totally impossible, that technology simply isn’t there regardless of the level of effort or resources put to the project.
Myself, I speculated that with a world wide effort and the resources of an entire world (and no time constraints) that its technically possible, though impossible from a practical perspective (since there is no way the entire world would would ever unit to put in such a maximum effort).
I won’t get into my idea’s on how it could be done…they were mostly shot down as impossible/impractical. Of course, I’m no aero-space engineer or rocket scientist, so my idea are essentially meaningless on this score. I write bad science fiction and my day job is building computer networks.
My hypothetical question though is this…given no time or monetary/resource constraints (other than those of the earth itself), and given todays technology (or technologies that may not be here today but WILL be here soon…i.e. no speculative technologies like fusion, but perhaps emerging technologies that just aren’t quite ready for prime time but will be soon), are there any folks on the board that COULD come up with a plausable scenerio to get folks to the nearest star alive and kicking?
Constraints are…you have to use either existing technologies or technologies acknowledged as practical emerging ones. You have a budget consisting of every country on earth. Ditto manpower and other resources…anything you need for the project, if it exists on earth, will be made available in whatever quantity you need. Any person or group of people needed will be made instantly available from any country on earth. Time is no constraint…you can take as long as you like to create the ship and as long as you like to send it to the nearest star. Crew size can vary, but lets fix a lower limit of 50 crew members…feel free to send as many more as you like. Risk…doesn’t matter. If the probability of the mission succeeding is 1 in a 1000 thats acceptable…1 in a 1000 is certainly better odds that ‘impossible’.
Can anyone do it given those parameters? I know there ARE some rocket scientists on the board…what say you?
the late Robert L. Forward proposed some innovative technologies, including using massive laser-generated photon proppulsion of what he called a “star-wisp” – a very lightweight non-manned lightsail-type craft with a sensor package that, aside from carrying people, meets your criteria. Since it’s propelled by photon pressure, the “engine” stays here, and we can keep it accelerating so that it reaches nearby stars in about a human lifetime. (It’s like the craft in “The Mote in God’s Eye”, only without the pilot and crew)
You have a solar sail so you could at least slow down by flying straight towards the star. If that wasn’t enough you could perhaps get into some kind of capture orbit. The nearest star system is Alpha Centauri which is a triple star so even if there are no planets, you might be able to do the capture using two or three of the stars themselves.
In some book I read – I think the Roche’s World set by Robert Forward – they jettisoned the outer portion of the solar sail and let it continue on. This reflected the laser light back at them and the innerportion of the solar sail.
Well, if there’s photon pressure going outward toward a star when we are still near Sol, then once we reach the point where the target star is closer, shouldn’t the photon pressure work in reverse order, thus slowing it down?
Oh, I don’t think there’s any “possibly” about it. I’m almost certain that, given nearly unlimited resources, we could send men to Mars. We’re not doing it because it’s too expensive and impractical. We can still learn a great deal with unmanned probes; there’s no reason to send men, yet.
Your (lack of) constraints effectively lower the cost of payload to orbit to a trivial amount, so hell yeah. Need a billion tons of iron shielding, a functioning arcology or ten, the ability to manufacture from raw materials even the most complex equipment - fill your boots! We’ve got all the time in the world, it just needs many flights using current tech. It’d be a huge mass and wouldn’t get anywhere particularly quickly, but it’d have a decent chance, likely better than 1 in a thousand.
1.) well, you could just not stop, and continue on through, or
2.) Forward suggested some methods of turning the craft around using magnetic fields and using light pressure to stop it.
The comparisons to his novel Rocheworld* (in its various incarnations ) is appropriate in some ways, but I want to emphasize that Forward – who worked a long time at Hughes Research Lab and later founded his own R&D firm, * Forward Enterprises* (he had the name for it, in more ways than one) – put this forward not as part of a science fictioon work, but as a doable piece of engineering. He presented and defended it at AIAA meetings.
Link to the referenced [thread=398234]thread[/thread]. Since I already expounded in great detail the technical concerns I have regarding the feasibility interstellar transit using existing technology, I won’t reiterate here except to say that it is well and beyond existing capability and experience.
I don’t doubt that at some point–assuming that we aren’t wiped out by natural disaster or apocalytic warfare–if will be feasible to travel, if slowly, to another system. Given unlimited time, as the OP posits, we will develop technologies that make the exisiting capabilities look as primitive as steam power. But current technology, even assuming an unlimited budget (of which there is no such animal), will not get you to another star system, and the schemes presented by the OP in the previous thread have crippling technical problems for which there is no plausible solution.
There are a number of options, each requiring extensive refinement of existing technology – but no brand-new technology.
The Universe Ship. Build a humongous artificial planetoid in orbit around Earth – something that will sustain human life indefinitely. Setting up a stable ecology is no small matter; just getting enough raw materials to orbit to build the thing is an enormous task. Decide what all is needed on this monstrosity. Equip it with Shuttle-like SSTO landers. Give it enormous engines capable of moving that enormous mass. Then get volunteers to man it – male and female. They’ll spend the rest of their lives on board it, have children who will do likewise – but sooner or later it will arrive at another stellar system, with a living crew aboard to explore it.
Bussard ramjet. This is a vessel able to “refuel” itself en route from the vacuum. Essentially you construct a ship capable of getting up to a certain fraction of the speed of light, at which point the concentration of dust, ions, etc., in space becomes “thick” enough to be collected (by an electromagnetic field trap) and used as fuel or propulsion mass. (To get an idea how this works, consider how much harder it appears to be raining/snowing when you’re driving at freeway speeds than when you’re standing still.) Again this is not a simple matter: you need to devise reliable equipment suitable for the initial acceleration and for generating the “net” to collect the particles. But the technology exists in its infancy today; it merely requires refinement.
Ultra-Efficient Fusion Drive: We can achieve controlled fusion today, but at barely a theoretical breakeven level (as much energy produced as goes in to generate the conditions for fusion) – nowhere near an “economic breakeven” level needed to build the things for power generation. And at that, only a few percent of the theoretical E=mc[sup]2[/sup] energy content of the deuterium-tritium-tralphium fuel is available. But if we can somehow improve the efficiency of a fusion generator to a very high percentage of theoretical energy, use anything for reaction mass and accelerate a ship of any arbitrary configuration to a high percentage of light speed. Advantage: relativistic time dilation – the time it would takefor such a trip as measured on board the ship shrinks. At 0.7 c you are travelling one light year per ship’s year; at higher speeds yet, the apparent speed for a given distance measured in light-years drops to a fraction of the years light takes. (From a rest perspective, of course, it’s significantly longer – but that doesn’t matter to the people on the ship, except for permanently distancing them from the people back home.)
Light sail vessel. Already described by others. Uses the pressure of solar (and stellar) radiation, and/or monumental lasers, for propulsion. Supposedly there are also “leave your motor at home” type devices using MHD as well, but I don’t even pretend to understand how they might work.
All these require extensive refining of technology but no new breakthroughs. Obviously an FTL vessel, if possible, will require entirely new theory, something that turns Einsteinian physics into a special case as Einstein’s insights did to Newtonian physics.
With existing technology, allowing only minimal refinements, the only plausible way to reach the stars is with an unmanned StarWisp type probe.
[thread=324185]JHere[/thread]'s an old thread where we discussed how solar sails work. Solar sails by themselves are good for maneuvering the inner system, but aren’t terribly efficient once you get further out and beyond the orbit of Saturn you might as well just get out an push for all the good it will do. The limiting case is the ratio between the photon flux and the mass of the sails; once the ratio gets too small, the performance is less than the influence of other factors.
Dr. Forward’s idea about the starwisp is interesting but his assumptions about the performance were flawed, and in any case it is both way beyond our current capabilities (a 10GW maser, 50000km focusing lens) and not scalable to the size necessary to transport a useful habitat-sized payload. Forward proposed other solutions involving the use of a powerful laser or laser array (deceleration was performed, as previously indicated, by separating the reflector into a forward free floating section and a section remaining mounted to the spacecraft) but the feasibility of this, even given the requisite technology and throughput, is highly questionable.
The conditions of “using today’s technology” and “given unlimited time” are fundamentally at odds with each other. For instance, it would be very useful, in constructing our starship, to have ready access to space. We could take a few millenia to build a space elevator cable, 10 cm at a time (we have the technology to do that much, right now). Or, we could spend a few decades or a century refining nanofiber technology, and then spend a year or two building the cable with the new, refined technology (which has the added benefit that if we want to use nanocable anywhere on our ship itself, we can make that quickly, too, rather than waiting another millenium). Which of these options is more realistic?
As discussed briefly in the previous thread, the Bussard ramjet has some serious technical drawbacks that may make it unusuable for interstellar flight and almost certainly unsuitable for living cargo. Aside from the fact that moving at large fractions of c would be immediately hazardous even when intersecting a dense cloud of hydrogen (much less the smallest speck of solid matter) you are going to have to operate an enormously powerful magnetic field. Variation in the constituants of the interstellar medium from which you are drawing fuel/propellent will play havoc with your confinement system. Drag on the field will limit top speed, which despite what certain science fiction authors have written, is probably no more than a few percent of c at best. It also has problems with regard to deceleration; you still have to carry enough fuel do decelerate from low range ramjet speeds to orbital speeds, and the trick of diving down into the sun only works if you assume very high thrust and efficiencies (and a lifesystem that can withstand a heavy dose of radiation); otherwise, you shoot out of the system in a hyperbolic orbit and keep going.
I wouldn’t classify the Bussard ramjet as being completely impossible, but it’s far more than an existing technology that requires refinement, and it’s possible that it would be completely unworkable, especially for an organic payload.
>and given todays technology (or technologies that may not be here today but WILL be here soon…i.e. no speculative technologies like fusion, but perhaps emerging technologies that just aren’t quite ready for prime time but will be soon)
My vote - this restriction pretty well shoots it. And the restriction is weirdly misplaced, too, as others point out. The biggest help with advancing time will be technologies that aren’t even speculative yet.
Less that 0.2 millenia ago, Sadi Carnot revolutionized the understanding of thermodynamics in a publication that escaped major notice until after his death - and even so, in his publication stated that heat engines create mechanical power without actually consuming any of the heat. At this time the fact that magnets can generate electrical current was unknown. In just a few more millenia, how different - how magical - will technology have gotten? Would you challenge Burt Rutan to build an around-the-world airplane without using any electricity or thermodynamics, or CFD or CAD or polymers or aluminum or gasolinte or…???
