Sizing Up the Daedalus Interstellar Spacecraft 191
astroengine writes "How big would an interstellar spaceship need to be? New artwork of the British Interplanetary Society's 1970's Project Daedalus by the non-profit organization Tau Zero Foundation gives the impression that the fuel economy for a nuclear pulse propelled vehicle might be a bit steep."
Space and Sails (Score:2)
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Except that interstellar space isn't much of an exploitable environment, being mostly dark and empty.
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Re:Space and Sails (Score:4, Insightful)
So then what do you do when you pass the heilopause and you no longer have a solar "wind"?
Honestly a redesign using ion engines of today would make a different craft. Plus it would allow the craft to not just speed on by in a ballistic trajectory, but even start breaking and enter a orbit that would allow the craft to stay and radio back info.
It can be electrically powered by Nuclear reactors, and as each one get's past it's 20 year lifespan you jettison it making the craft lighter. Ion engines already are producing impressive thrust for the age of the technology. An unmanned interstellar probe moving at 12% the speed of light, assuming it does not plow into something out there is a very feasible project and could gather scientific data the entire way. Although the Doppler effect on communications would be interesting. But research into really measuring time dilation could be done as well.
Sadly, we are far more interested in killing each other. It's more important to fund the war machine than the thinking machine.
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An unmanned interstellar probe moving at 12% the speed of light ... Although the Doppler effect on communications would be interesting.
"Interesting" is a gross overstatement here. Even if you didn't know how fast it was going, such a Dopper shift would be trivial to correct for with a suitable signal. Now, if we're talking 99.999% c, that's another matter!
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Sails (also of more active kind [wikipedia.org]) probably have one monumental advantage: they should be fairly easily mass-produced (without swallowing half of GDP of the planet like TFA projects would / that's some solution to constant (it was pretty much always like that, don't kid yourself it will ever change much) lack of fun
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You coast until getting into the heliosphere of another star (they move quite predictably) - you can even slow down like that! (with the help of stellar aerobraking? That would be some sight...)
the problem with stellar aerobreaking is that if you want to come to a full stop again, the target star needs pretty much the exact same heliosphere as your origin for it to work effectively. Traveling to a star which has only half the solar wind pressure would require you to close your solar screen at the start of the journey because else you will be going to fast to bleed off all the speed. This off course means you will be traveling much slower.
Your speed is basically limited by the weakest star in your
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Secondly, when I wrote "stellar aerobraking" - I didn't mean using only stellar wind, in the same way as during departure. Actual plunge into relatively dense portions of the stellar atm
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You could, you know, trim your sails or deploy more sail depending on the current (solar) wind...
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yes, but assuming you want to go somewhere in a cosmic space, you would always be on full sail, except when limited, by say, your breaking ability at the other end...
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Moreover, you'll want a bigger sail so that near the edges of solar wind, where by definition it is weaker, you still get the same acceleration ability.
My point is that wind varies so you need sails that can accommodate that. You would build a sail that would provide both acceleration and breaking ability under the conditions you expect to en
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So then what do you do when you pass the heilopause and you no longer have a solar "wind"?
Solar sails don't run on the solar wind, they run on photon pressure. Not that it helps much; it will be difficult to get much thrust from solar sails when you are at the heliopause, simply because the Sun will be awfully dim from that distance.
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IIRC, the thrust expected from a solar sail near earth's orbit is about half from solar wind and half from photons. Of course, the solar wind is quite changeable. Also, while one can tack against the photons, one cannot tack against the solar wind, because the particles embed themselves in the sail rather than being reflected.
I don't know what the conditions would be near the heliopause. It could well be that the sail would impact the solar wind slowing the vessel (whether on the way in or out).
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So then what do you do when you pass the heilopause and you no longer have a solar "wind"?
I half remember some proposal where a sail plane would spend decades in ever increasing elliptical orbits building up speed until it would change course and head off at some reasonable percentage of the speed of light.
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I half remember some proposal where a sail plane would spend decades in ever increasing elliptical orbits building up speed until it would change course and head off at some reasonable percentage of the speed of light.
That's not possible because escape velocity from the solar system is well below that. If you move at a reasonable percentage of the speed of light, your trajectory is straight, not elliptical. Or rather, it's an ellipse that's so elongated it goes beyond the heliopause.
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"So then what do you do when you pass the heilopause and you no longer have a solar "wind"?"
Lasers!
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Ion engines don't have a high enough specific impulse (equivalently exhaust velocity). They would need far too much fuel.
Even a perfectly efficient fusion rocket (which we have no idea how to build) would need a pretty huge mass ratio to achieve a total delta-V of .25c (ie speed up to Daedalus' proposed top speed and then stop again).
Antimatter rockets could work, if we could find a way to (a) build them (b) make enough antimatter and (c) store it.
Ramjets woudl be lovely but (a) we have no idea how to get h
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The remaining option is beam riders. We send a beam of momentum, carried by photons (laser beam) or matter in some form (a stream of small very rugged missiles launched by a magnetic cannon at say 0.5c might work). This lets you leave your engine at home, which means it can be very nig and solar powered.
Focusing a high powered, coherent beam, and aiming it accurately at those kinds of distances is amazingly difficult, and several orders of magnitude beyond our current targeting capability. Beam riders are no more feasible in the near term than any of the other proposed solutions.
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We can't even coax ourselves into going back to the moon. At this point, we might as well be contemplating inter-dimensional travel, for all it matters.
Re:HOW DO I VIEW ALL COMMENTS WITH NEW SLASHDOT? (Score:4, Informative)
You switch to D1 instead of the stupid D2 discussion system by clicking on Account while on the main page. D1 actually lets you view more-or-less all the comments for most stories.
Then fix up the D1 system by creating/editing userContent.css (assuming you are using Firefox) in your profile/chrome directory:
@-moz-document domain("slashdot.org")
{
div.col_1
{
position: absolute !important;
}
header.h
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position: absolute !important;
}
li.comment
{
border:solid 1px grey;
-moz-border-radius-topleft:10px !important;
left:20px;
width:95%;
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}
Spaceship? (Score:4, Insightful)
Wouldn't "space probe" be more accurate? I don't believe it was ever intended to be manned.
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And if it were to be manned it wouldn't be a return trip so to allow for a sufficient genetic variation the crew needs to be at least 1600 individuals.
Otherwise the risk of genetic degradation would be too great.
Re:Spaceship? (Score:5, Funny)
But... I was told that 2 was enough?!
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insta +1 :)
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Or you could start with a small female crew, and thousands of "genetic samples". (Semen and eggs)
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Or you could start with a small female crew, and thousands of "genetic samples". (Semen and eggs)
Why only chose the small females? Is that to save space or just weight?
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1 man
1599 females
And a set of frozen semen in case the man bites it too early.
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...if we'll ever do direct flights, that seems like the most likely way (yes, we can already put humans into deep hibernation!)
Though I suspect it might be just gradual spreading across Oort cloud (estimated trillion comets!) over several thousands of years
Re:Spaceship? (Score:5, Interesting)
And if it were to be manned it wouldn't be a return trip so to allow for a sufficient genetic variation the crew needs to be at least 1600 individuals.
Otherwise the risk of genetic degradation would be too great.
Depends on what "too great" means. The Hutterite community in North America, a closed religious community, was founded around 1700 with a founding population of about 400 that was already highly inter-related (compared to world-wide human genetic diversity) and has now increased to 50,000. Genetic studies do show a measurable penalty in fertility and fitness with this high level of inbreeding, but the community is doing quite well nevertheless.
What is more there is evidence of major human populations developing from even smaller founder groups PLoS Biology, June 2005, On the Number of New World Founders: A Population Genetic Portrait of the Peopling of the Americas [plosbiology.org] asserts that "Taken together, the analyses in this study suggest a recent founding of the New World Amerind-speaking peoples by a small population of effective size near 70"
Now the lack of diversity in the immune system of the American Indians later led to an epidemiological calamity when diseases from the Old World were imported 10 or 15 millenia later, but this is an avoidable hazard for interstellar colonists.
But the key difference with a space mission is that there is much we can do to avoid genetic disorders and promote genetic diversity:
* Select colonists (or colonist couples) for genetic diversity,
* Use sperm/ova banks to import gentic diversity,
* Use genomic screening to screen out lethal genes (which can be applied in a number of ways).
These techniques can make inbreeding problems go away entirely.
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From the article: A major drawback (Score:4, Insightful)
Or maybe not so major of a drawback.
Says it would zoom past Barnard's Star in 50 years at 12.5% the speed of light because it is not designed to go into orbit. So, it is just getting a quick look there and everyplace else it travels. By the time this thing could be built, sensor technology might be up to the task.
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That's the nutty thing about this (Score:2)
Per TFA - we'd have to mine the atmosphere of Jupiter for 20 years to accumulate sufficient He3, then send this very, very expensive ship on a one-way trip, which will take 50 more years... and it's going to fly through the system at 10% of the speed of light? Why the hell would anyone bother? I mean, holy crap - the whole thing is pretty far-fetched anyway, so why not ask for the pony: the ability to freaking slow down before you get to Barnard's Star? Then maybe you could do some useful science.
Think Positron Engine Drive (Score:4, Informative)
W.M. Keck Lab [wsu.edu]
This article and video explains their research: http://wsutoday.wsu.edu/pages/publications.asp?Action=Detail&PublicationID=14531&TypeID=1 [wsu.edu]
Re:Think Positron Engine Drive (Score:5, Insightful)
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The problem is that there is no known naturally occurring source of antimatter
Apart from thunderstorms [space.com] of course.
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Unfortunately it is inefficient to produce anti-protons for very fundamental reasons. Protons are composites of quarks and there is a low probability of creating one in a collision. I seem to remember the best theoretical efficiency is less than 1e-4, and practical sources are FAR worse.
If you only make positrons, there is no practical way to store large mases. You would really need to make anti-hydrogen, then (somehow - no idea) levitate it magnetically. The efficiency for anti-hydrogen production is spect
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That makes it nothing more than a battery technology.
Given that the huge majority of the weight of any spacecraft is taken up by the fuel, an efficient "battery technology" would be a major breakthrough. If your fuel has a high energy density, it means your spacecraft will be lighter, and therefore require less energy.
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Problem solved... just take a thunderstorm with you!
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That would be fairly simple - just take a giant Tesla coil with you - that provides lightning. But you would still need to capture and contain the anti-matter particles, so that requires a fairly strong magnetic field. As a bonus you would be able to play Ghostbusters Ghostbusters on a tesla coil [youtube.com]
Absurd (Score:2)
Oddly enough, I was reading up on possible interstellar probes just a few days ago.
Anyway, getting to another star system is just simply such a huge task. Take for example Daedalus' design -- the economics of building such a vehicle today are such that even if we had the political willpower to do so, it would just cost so much that it would soak up our global economic output for a very long time, possibly centuries.
If we were to just wait 100 years or so, I'd put money on new physics being discovered which
I strongly disagree (Score:5, Insightful)
Oddly enough, I was reading up on possible interstellar probes just a few days ago.
Anyway, getting to another star system is just simply such a huge task. Take for example Daedalus' design -- the economics of building such a vehicle today are such that even if we had the political willpower to do so, it would just cost so much that it would soak up our global economic output for a very long time, possibly centuries.
If we were to just wait 100 years or so, I'd put money on new physics being discovered which would allow an interstellar mission to be constructed for a tiny fraction of the cost of Daedalus (or Icarus), be completed in a fraction of the time, and have enormously increased capabilities (e.g. stopping at the target star, making a return journey, or even carrying Astronauts).
It's an interesting study, but totally impractical today. We need a better understanding of the universe before we should even give serious thought to attempting this -- it doesn't pass the back-of-the-envelope test.
It's not completely absurd. The projects that mankind undertakes today are enormous (in fact, there are multiple things that are way more expensive or complicated than this Daedalus spaceship). Take for example the entire road system of the world, including all rural roads, cities, traffic lights, cars, trucks, and whatnot. It's been an enormous undertaking - yet we don't mind rebuilding it entirely every decade because we don't like bumpy old asphalt or old cars.
The ISS, with a weight of nearly 400 tons, and measuring 50x100 meters shows how much is possible for a relatively small-scale human project. All our civil achievements show how much is possible for the large-scale human projects. We don't mind changing the entire surface of our planet.
We humans look at cost/benefit estimates. If the costs are high, we don't mind, as long as the benefits are there.
The problem therefore with the Daedalus is not that it's not possible. It is that it just does not have enough benefits for mankind to invest the time, effort and resources in it.
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Re:I strongly disagree (Score:4, Insightful)
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The ISS, with a weight of nearly 400 tons, and measuring 50x100 meters shows how much is possible for a relatively small-scale human project.
The ISS cost $157 billion, according to Wikipedia. The scientists who came up with Daedalus estimated the total cost at $100 trillion (not sure if that's in 1970s dollars, I read it on Tau Zero's website). The total GNP of the entire planet is currently only about $65 trillion (US alone is $15 trillion). Aside from much of the technology being purely theoretical at
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The thing is, every step along the way has potentially huge benefits, enough so that most of them will probably happen over the next century or so even Daedalus but a large scale, long term target would speed things up considerably.
You're not going to build Daedalus without a much cheaper way to get things into orbit, traditional rockets are never going to cut it. You need something more economical; whether that be a space elevator, a launch loop, laser powered rockets or whatever.
Even with a cheaper way t
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Don't bet on new physics; there's really nothing particularly suggestive of the practical limits we stumbled upon not being there. Of our physics being very wrong (it would pretty much have to be, if you wish for practical FTL / time travel), vs. just incomplete.
(that said, yeah, there are almost certainly more practical approaches than Daedalus or Icarus)
A 100 years may be too late! (Score:3)
... If we were to just wait 100 years or so ...
There are (clever) people who think that there is a window of opportunity for such a large project and that at some point the ever-growing population of the Earth will be so large that _just feeding_ everyone will take ALL the economic output of the planet. At that point, assuming we still have democracies, no Government is going to get elected if their manifesto includes such items as restricting the budget for feeding people and increasing the budget for some off-world boondoggle.
This doesn't seem unli
Nuclear fission propulsion (Score:3)
What about using nuclear fission propulsion like Project Orion [wikipedia.org]? We already have the material and technology to make one if a way to launch without causing fallout and EMP disruption could be found.
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nuclear fission propulsion, like Project Orion, is incapable of the deltaV required for anything like a quick interstellar trip.
Orion, as originally conceived, produced an Isp of less than 2000. Which implies that a 10000T spacecraft would have to carry an additional 5.4E785 tons of fuel/reaction mass.
Note that 5E785 tons is rather more than the mass of the observable universe....
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I don't know where you get your figures from, but according to the Wikipedia page for Specific Impulse [wikipedia.org], the ISP for an Orion-style drive is 10.000 to 100.000.
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Bah, preview fail. The ISP for an Orion-style drive is 10.000 to 1.000.000.
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Orion can't carry enough fuel for interstellar travel. Orion can probably never be launched cleanly from planetside, either. It has to be built in orbit or not at all.
Re:Nuclear fission propulsion (Score:4, Interesting)
Freeman Dyson published a paper called "Interstellar Transport" (Physics Today, October 1968, p. 41–45) on how to build an Orion spaceship to get to Alpha Centauri [wikipedia.org], so yes, it could carry enough fuel for interstellar travel. Your other two points are correct though.
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Actually NASA did a study on boosting an Orion into Orbit on an uprated Saturn. It was a smallish Orion but still an Orion.
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Funny but Voyager is on an interstellar trajectory. I think your math is probably wrong on that. The Orion would have issues with a fast transit but yes it could travel interstellar distances.
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The Orion would have issues with a fast transit but yes it could travel interstellar distances.
Sorry, I meant "interstellar travel of humans who will arrive at their destination with years left on the clock". It's not big enough for a generation ship. Let's deal with practicalities here.
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Well at this point I do not consider interstellar manned missions practical at all so I would say that I was dealing practicalities. Dyson did a study of a momentum limited Orion and he got a travel time of only 44 years. Possibly in life time to see some results and well within a 20 somethings life time to get data back.
So again I would say yes it is possible and practical to use an Orion for an interstellar probe if you could get around the political and ecological issues and or get one into orbit.
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We have no experience making spacecraft which can last 44 years while supporting humans. That's a stupendously long period of time.
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[The Orion is] not big enough for a generation ship. Let's deal with practicalities here.
General Atomic studied several sizes of Orion in 1959, the biggest of which was the "Super-Orion", weighing in at a stupendous 8.000.000 tons. According to the Wikipedia page [wikipedia.org]:
it could easily be a city. In interviews, the designers contemplated the large ship as a possible interstellar ark. This extreme design could be built with materials and techniques that could be obtained in 1958 or were anticipated to be available shortly after. The practical upper limit is likely to be higher with modern materials.
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Well, we might have the materials, but whether or not we have the 'technology' depends on the reflectivity of your mirrors and the density of your smoke.
Seriously, many people like to treat Orion as if it were more-or-less ready off the shelf - when it's anything but. Pretty much none of the concept has been tested above the laboratory bench prototype level, and pretty much none of
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You can do nuclear without an orion drive. A more conventional nuclear reactor could then power some high ISP engine (like an ION drive). The specific impulse is still no where near antimatter, but could probably get you to ~5% C.
Buyer's remorse (Score:3)
The problem is that if one undertakes a huge project to build a big ass ship and it launches, one hundred years later the technology will have advanced so much that we will be able to build another one which is bigger and faster. A hundred years later, the same thing. So the original ship gets to where it was going only to find that several ships are already there.
I dimly recall some science fiction works with this theme.
Re:Buyer's remorse (Score:5, Insightful)
Yeah... but building it will be one of the ways of improving such technology (and every other way of improving the technology costs money, too).
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The effort to construct each new ship is in itself a learning experience. As a result, even though each new ship would be that much better, it would take far longer to try to skip generations. Taken another way, if Intel waited until they could make a 16MHz chip, they would have gone bankrupt, so making the 4.77MHz 8088 was well worth the investment. While these ships may not be commercial vehicles, the technology that emerges as a function of building each ship(due to R&D) can help other proj
The obvious difference here (Score:2)
The obvious difference being that Intel could actually sell the 8088 and recoup some investment. This project is so huge that it would be like leaping straight from the transistor to a huge supercomputer. And you can't sell the supercomputer.
I have to say that while this kind of thing is interesting to think about, the amount of scientific bang for t
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So, you're saying that you should never start any projects with a steep learning curve, but instead just wait (and wait, and wait) until someone else starts, and then be the 2nd to step in.
Bah. I disagree. There's always a chance that the 1st project is actually the good one... and that it's considered good enough.
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The problem is that if one undertakes a huge project to build a big ass ship and it launches, one hundred years later the technology will have advanced so much that we will be able to build another one which is bigger and faster.
Yet here we are, 40 years after the moon landings, and repeating them seems about as expensive as the original effort. We certainly are not going to travel significantly FASTER to the moon this time. Perhaps the next 60 years will bring progress and you will be right.
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You could just send them different ways much like the Pioneers and Voyagers.
Automation has a long long way to go (Score:2)
I have to think that our ability to engineer unmanned system has to grow by many orders of magnitude more than our propulsions technology has to, for us to really think about this kind of project.
Re:Automation has a long long way to go (Score:4, Interesting)
I think you'll find that we can do that [wikipedia.org], if by "we" you mean the human race. IKAROS has passed Venus, and is still going strong.
We should build an interstellar probe (Score:2)
I'd love to see an interstellar probe, the best humanity can build with today's technology, sent to round the nearest star and return.
The goal should be to have to make it back to earth within a human lifetime, which should be either just barely possible (~80yrs) or easily possible (~40yrs) depending on the current state of a few of the more advanced propulsion technologies that have actually had some practical testing done in the lab.
Daedalus class (Score:5, Funny)
I thought the Daedalus incorporated a lot of Asgard technology, including Hyperdrive and site to site beaming ability. It would be very useful to have since it can go to other nearby galaxies (Like Pegasus)
Heres some info: http://stargate.wikia.com/wiki/Daedalus
Miniaturization (Score:2)
I would recommend to see how all components scale down. If you make everything smaller by the same factor, does performance suffer?
Or, in other words, for which components is a certain size essential? And how big is that?
Reduce the mass by half, reduce the fuel by half... and find which components cannot be made any smaller, or which do not scale linearly with the fuel needs or performance... Push the limits of some components to make them smaller (and invest heavily in those miniturization bottlenecks, bec
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I would recommend to see how all components scale down. If you make everything smaller by the same factor, does performance suffer?
Yes: this particular system (Daedalus) fails to work.
The BIS design was a design attempt at the smallest probe possible.
The new study (Icarus) revises that considerably.
Pointing a sign (Score:2)
Great! It will be a big sun-hot arrow pointing right back at us saying, "Here are some young pushovers!"
It's very cool but I'd like to see the engineering plan.. can we currently afford to build it nor fix it unless we have industrial nanotech that can eat up huge mountains and turn it into high tensile steel..?
Meanwhile that tiny joint above the engine looks like the weak point. Aside from all the other parts that get hit by pebbles in orbit around Barnard's Star at 12% of c..
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I'd ask can we afford not to?
The clock is ticking and at some point the Earth will be so full that undertaking such an enterprise (!) will require not feeding vast numbers of people to scrape the money together.
Bad name? (Score:2)
You'd figure that'd be a bad omen if you're considering flying to another sun.
Tau Zero (Score:2)
For those interested, the Tau Zero Foundation (referenced in the text) does have a website, www.tauzero.aero/ [tauzero.aero]
RTFA: none (Score:2)
RTFA:none. Unmanned probe.
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...the failure in this is taking fuel with you
A Solar sail works with no fuel ... and with some clever steering could tour many stars (although not visit very near any of them?)
A Buzzard Ramjet (if they can build it) does not need any fuel, it gathers it as it goes...and could accelerate forever ?
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It may be able to accelerate forever, however the rate of acceleration will tend to zero as your velocity tends to c.
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A Buzzard Ramjet (if they can build it)
(...and if it can create more thrust than drag, which might very well be not the case)
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A Buzzard Ramjet (if they can build it) does not need any fuel, it gathers it as it goes...
I don't think you'll find many dead animals on the side of the road going through space.
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That is "Bussard" , after Prof. Robert W. Bussard, who postulated it first:
http://en.wikipedia.org/wiki/Robert_W._Bussard [wikipedia.org]
Problem is that it does not gather enough fuel at lower velocities, so is not much good "in system".
Collecting dust also has a price in terms of drag.
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Well, in all fairness, this IS a Sci-FI article (at least according to Slashdot), so your points have merit in that respect.
However, being realistic, solar sails would only work until you reach the heliopause, after which the solar wind would have less force on the sails than whatever floating around out there would. There's no way you could accelerate to any useful speed that way.
As for Ramjets, the theory is sound, assuming there is actually enough fuel to utilize. However, space is VERY empty. My (prob
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It looks like 99% of the room is used for tanks and engines.
Rocket equation and physics in general is a bitch, isn't it? (that 99% is not much worse than with all our current launch vehicles)
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Here's another plate of beans.
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Nah, the text is scrollable. You just have to go back to 1995 and actually use the scroll bar...