Sizing Up the Daedalus Interstellar Spacecraft

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."

Comments

Space and Sails

[h00manist]

Space seems like the ultimate research and application ground for something that uses the environment around it as a power source, inspired by sails.

Re:Space and Sails

[danhuby]

Such as?

Re:Space and Sails

[lxs]

Except that interstellar space isn't much of an exploitable environment, being mostly dark and empty.

Re:Space and Sails

[Lumpy]

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.

Re:Space and Sails

[FTWinston]

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!

Re:Space and Sails

[sznupi]

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...)

Sails (also of more active kind) 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 funds for research)

Re:Space and Sails

[sznupi]

...seems like a good place for basement-dwelling kind slasher movie.

Re:Space and Sails

[Seumas]

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:Space and Sails

[amorsen]

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.

Re:Space and Sails

[Chrisq]

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.

Re:Space and Sails

[mangu]

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.

Re:Space and Sails

[Vectormatic]

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 journey

Re:Space and Sails

[nospam007]

"So then what do you do when you pass the heilopause and you no longer have a solar "wind"?"

Lasers!

Re:Space and Sails

[sznupi]

Not really, no - first, the probe can initially put itself into a very elliptical orbit around target star and circularize it gradually (like we already do when arriving at other local planets, with probes having pitiful delta-v budgets); parameters of its orbit don't need to mirror at all those at the start of journey...

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 atmosphere could bleed off some km/s ... yes, expected to hard, but certainly "that would be some sight..." ;>
Some gas giant might be similarly handy. Or - having some "last ditch" means of active propulsion (a nuclear warhead or two?) - to be used also when extremely close to the target star, exploiting Oberth effect.

Re:Space and Sails

[Kell Bengal]

Not quite true - as your orbital radius increases, your velocity decreases or else you have a hyperbolic trajectory and aren't 'orbiting' per se.

Re:Space and Sails

[Anonymous Coward]

First habitable planet outside our Solar System located! in other news.... Kepler XV uninhabitable due to nuclear fallout from space probe.

Re:Space and Sails

[pixelpusher220]

You don't sail much do you?

You could, you know, trim your sails or deploy more sail depending on the current (solar) wind...

Re:Space and Sails

[Vectormatic]

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...

Re:Space and Sails

[pixelpusher220]

You wouldn't have a sail sized to your acceleration needs. You'd have one significantly bigger because generally you'll want to stop faster than you accelerate.

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 encounter. I.e. you don't set sail with a sail that is too small for your destination

Re:Space and Sails

[sznupi]

Is Earth uninhabitable after over 500 atmospheric nuclear weapons tests?

Re:Space and Sails

[stevelinton]

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 hydrogen (as opposed to deuterium or helium 3) to fuse in less than billions of years, and a ramjet would have to do it in a few microseconds and (b) the solat system is in the middle of a big bubble in which the interstellar gas is exceptionally thin.

Photon or magnetic sails powered by "ambient" power -- ie starlight, solar wind, etc. do not get nearly enough boost before they have escaped from the star and are too far away from it.

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. The probe needs some way of catching the momentum, probably a light-sail or magnetic trap of some kind (blast the missiles to plasma and bounce them off a magnetic field). Stopping is harder -- Forward proposed detaching part of sail and sending it on ahead as a mirror and then using the reflected laser beam to brake.

Re:Space and Sails

[wagnerrp]

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.

Re:Space and Sails

[HiThere]

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).

Re:Space and Sails

[stevelinton]

For a laser, or a particle beam, I agree. A beam of guided missiles might be slightly less insanely difficult.

Re:Space and Sails

[shutdown -p now]

That's not possible because escape velocity from the solar system is well below that.

You don't have to leave the orbit once you reach escape velocity - you can always steer, you know.

Re:Space and Sails

[gstoddart]

except when limited, by say, your breaking ability at the other end...

I'd rather have braking ability at the other end. ;-)

Re:Space and Sails

[gstoddart]

Except that interstellar space isn't much of an exploitable environment, being mostly dark and empty.

Sounds like North Eastern Maine.

Re:Space and Sails

[Rei]

There's a lot more types of engines than that. :P

Honestly, I don't see why there should *ever* be a just-plain "coast" phase of a trip. At least keep those engines as hot as you can and run them as a photonic rocket, which yields the maximum-possible Isp (with the downside of very low thrust per unit area). We've already done this -- accidentally! The New Horizons spacecraft was thrust slightly off course because of radiated heat (photons) from the RTG which reflected off of its antenna.

There are a number of proposals for the use of antimatter apart from just pure matter/antimatter annihilation. For example, antimatter-initiated microfission or microfusion is a proposed way to do ICF (what fueled Daedelus) with a far smaller reactor. While the Isp is lower than with puer matter/antimatter annihilation, of course,, it takes far less antimatter. We could potentially produce the required amount here on Earth if we wanted to. Of course, all antimatter designs, but especially direct matter/antimatter annihilation, need to work a lot on trap design.

There are even some pure fission concepts that yield surprisingly good Isp. My favorite is the "dusty fission fragment rocket". Most of the energy in a uranium fission reaction comes in the form of fission fragments. These are large chunks of the uranium nucleus, moving at relativistic velocities. In a traditional fission reactor, they're thermalized, and then the heat is used to heat a working fluid. In a fission fragment reactor, the design is such that the fragments are allowed to escape and can be collimated into a beam, which can then be decelerated to produce energy (or released as a rocket). A dusty fission fragment rocket is a novel approach to work around the heating problems of previous designs; the core is a fine dust of fuel coated in a graphite moderator. The particles readily self-ionize due to decay; with an electrostatic charge on the outside of the reactor, they distribute themselves throughout the core. Because of the fine size of the particles, there's no time for the fragments to be thermalized and they escape (and are then collimated).

Of course, one can always throw away trying to get absurd Isp levels and go for "good" Isp plus simplicity of design, and then focus heavily on staging. A notable design in this regard is that of the nuclear saltwater rocket. The fuel is enriched uranium saltwater, kept in small, neutron-absorbing tubes to prevent criticality. The water is injected into the core where -- a large amount of fuel being in a single place at a single time -- it goes critical, and is directly exhausted out the nozzle.

For the ultimate propulsion (direct matter-antimatter), the big issue comes down to, "how can you produce that much antimatter?" I have a concept I've not had a chance to dig into more of space-based antimatter production which could potentially provide enough for direct matter/antimatter annihilation as well; the concept is to use a natural particle accelerator to accelerate the solar wind (such as near Jupiter, or even more, near Io specifically) up to dozens to hundreds of MeV, and then use an additional magnetic field to pinch it further up to the GeV energies needed for antimatter production, right where your targets/cooling/traps are. Basically, you get your ion stream nearly for free. Heck, there may be enough occasional protons naturally accelerated to the required energies in certain places that you may not need further acceleration; I've not had a chance to dig in detail into the data on Jupiter's radiation belts to say. This all comes with the caveat that I've not had the chance to look up the specific ion energy and density distributions to get a sense of how large and difficult to build such a collector would need to be.

Of course, you can always just accept a lower relativistic velocity and go with a generation ship (or if you want to get really exotic, since there's no way we'd be building an interstellar spacecraft in the near future, one with artificial wombs, frozen embryos, and an automated child-rearing system)

Re:Space and Sails

[Rei]

Huh. I've been talking about the concept of using planetary magnetic fields for antimatter production for a decade or so, but it now looks like I'm not the only one:

Extraction of Antiparticles Concentrated In Planetary Magnetic Fields

Bickford's approach is a bit different, though -- instead of including a collision target and trying to accelerate bulk solar wind up to GeV energies, they're looking to merely collect antiparticles already produced by natural collisions, via modified Bussard ram scoop. Not a good enough collection rate for a direct matter/antimatter interstellar mission (only 250 micrograms per year at Saturn, for example), but it'd certainly be a start.

Re:Space and Sails

[stevelinton]

I heard a lovely lecture almost 30 years ago in which someone took a really fundamental look at this starting with relativity and a model that covers all kinds of rockets, no matter how fueled and powered. Essentially there are just two numbers that matter:

1. The proportion of your fuel which you turn into energy. This ranges from 0.1% for a perfectly efficient U235 fission reactor up to about 0.5% for fusing protons to helium and up to 100% for matter-antimatter.

2. The ratio of reaction mass to that energy which you use for propulsion, which ranges from 0 for a photon rocket to something enormous if you're exhaust velocity is less than relativistic.

Given 1, you can optimise 2 for a given length of journey.

Anyway, the conclusion of this is pretty stark: with any mass ratio you can imagine building, even if your spaceship is a capsule strapped to an asteroid of pur hydrogen ice, fusion will, at best, get you up to 0.2c or so and then stop you again. Fission is much worse.

Re:Space and Sails

[B4light]

A 1 second signal broadcast at .99999c would take us 100000 seconds to read. It's kind of annoying, but you only have to deal with that while it's travelling for the 6 years between the stars. Hopefully it would slow down to normal planet orbiting speeds.

Re:Space and Sails

[B4light]

Why not just use all of the sail so you can get there faster, and if the other star has less stellar pressure, just use even more sail when you're there to slow down.

Re:Space and Sails

[B4light]

No, you can't steer at relativistic speeds. The LHC uses tremedously powerful magnets to steer protons around a 20km track at near the speed of light, you won't be steering your spaceship at 0.5c

Re:Space and Sails

[Jane Q. Public]

(1) As counterintuitive as it may seem, a rocket's velocity is not limited to its exhaust velocity.

(2) Specific impulse is not directly related to exhaust velocity. It is a measure of how much momentum is imparted to the craft per amount of mass of the propellent. Ion engines actually have a very favorable specific impulse. In fact that is their main advantage over conventional chemical engines.

(3) "Billions of years" have nothing at all to do with hydrogen fusing. They don't just get old and decide to fuse. If it is going to be accomplished at all, it is energy, not years, that will do it.

Re:Space and Sails

[stevelinton]

(1) As counterintuitive as it may seem, a rocket's velocity is not limited to its exhaust velocity.

(2) Specific impulse is not directly related to exhaust velocity. It is a measure of how much momentum is imparted to the craft per amount of mass of the propellent. Ion engines actually have a very favorable specific impulse. In fact that is their main advantage over conventional chemical engines.

(3) "Billions of years" have nothing at all to do with hydrogen fusing. They don't just get old and decide to fuse. If it is going to be accomplished at all, it is energy, not years, that will do it.

I'm afraid (2) is just wrong. Specific impule is exhaust velocity divided by g (hence the units of seconds). Ion engines have a very favourable specific impulse (compared to any kind of thermal rocket with a material nozzle) because they have a high exhaust velocity. I know about (1) but mass ratio grows as e^(delta-V/exhaust velocity) so exhaust velocity is extremely relevant.

Re (3) you're right I was being sloppy. In the conditions in the centre of the sun, the average proton takes about 15 billion years to fuse (ie about 1 in 3 have done so so far). If you could achieve greater temperatures and densities they'd fuse faster. Nevertheless, this does make a Bussard ramjet look a bit tricky to engineer.

Re:Space and Sails

[Jane Q. Public]

I should have stated that better, but even so it's not so simple. There are two ways that specific impulse is commonly represented: in seconds and as a velocity. Specific impulse in seconds requires the mass of the expended propellant in the calculation. And that is why, for example, an ion engine using mercury as a fuel can be, for long distances, much more efficient that a typical chemical-reaction engine of the same mass, even though the thrust might be much higher in the chemical rocket. The ion engine is also smaller.

Specific impulse in terms of seconds is given by this equation. Notice the "delta m". That is mass of propellant, which cannot be neglected. If you do, what you are talking about is not specific impulse.

Having said that, I will qualify my original statement and say that specific impulse (in seconds) is in fact proportional to effective exhaust velocity, but ONLY given a specific mass mass of propellant. You cannot neglect mass in the equation.

The other common way to state specific impulse is by the effective exhaust velocity, which in a vacuum is approximately the same as its relative velocity to the engine. But that is a velocity, it is not in seconds. And note that the formula given for it still makes use of the specific impulse in seconds, which in turn still requires propellant mass in order to calculate it.

As for the third point, now I see what you are getting at. In that context it makes sense.

Re:Space and Sails

[stevelinton]

If you read further down the web page you cite you see that the specific impulse for a rocket (and an ion engine is a rocket for these purposes) really does only depend on the exhaust velocity. The mass of the propellant cancels out (the more massive it is, the more momentum it carries for given velocity, but the more mass you are throwing away to do it). For an aircraft (or a car for that matter) it's more complex because you are using outside air/road as reaction mass. Some calculation like that would also be appropriate for a Bussard ramjet.

Re:Space and Sails

[Anonymous Coward]

I say skip sails, space steamship is the way to go. My calculations prove that just two strong men with shovels should be enough to accelerate enough and reach Orion in no time.

Re:Space and Sails

[cheekyboy]

Dont tell that to the casini engineers . Who forgot such a thing exists.

Re:Space and Sails

[pixelpusher220]

Do you see the fallacy in your logic?

"Why not use 'all' the sail?" followed by "just use more to slow down"

If you used 'all' of it to speed up, there isn't any 'more' to deploy a bigger sail when slowing down.

This was my point, you don't size the sail based on your acceleration alone but on having to stop faster than you accelerated.

Re:Space and Sails

[Jane Q. Public]

True; in the specific case of a rocket in a vacuum, that is what they state.

Even so, it must be noted that the actual velocity of the rocket is not, as many assert, limited to the exhaust velocity itself. Also, in an ion engine, energy efficiency is not as much of a consideration because the designs are generally nuclear-powered, with plenty of energy to spare. Indeed, a major design consideration is preventing the release of too much energy. So while a higher exhaust velocity implies a higher vehicle velocity (in a given period of time; remember this is in relation to specific impulse in seconds), and thus a lower energy efficiency, an ion drive can generally afford that inefficiency where a chemical engine could not.

Spaceship?

[stjobe]

Wouldn't "space probe" be more accurate? I don't believe it was ever intended to be manned.

Re:Spaceship?

[Z00L00K]

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?

[geogob]

But... I was told that 2 was enough?!

Re:Spaceship?

[snap2grid]

In the aerospace industry, even satellites are referred to as a spacecraft.

Re:Spaceship?

[Anonymous Coward]

Or you could start with a small female crew, and thousands of "genetic samples". (Semen and eggs)

Re:Spaceship?

[bronney]

insta +1 :)

Re:Spaceship?

[Anonymous Coward]

yeah. me and yo momma.

Re:Spaceship?

[Anonymous Coward]

The male/female ratio don't need to be 1/1

Re:Spaceship?

[sznupi]

http://en.wikipedia.org/wiki/Embryo_space_colonization
...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 ... and at one point some groups will hitch a ride into the Oort cloud of some passing star. On geological timescales this will also assure very quick colonization of the galaxy.

Re:Spaceship?

[sznupi]

Would an automated container ship no longer be a ship? (there's hardly any crew on them as it now...)

Re:Spaceship?

[Anonymous Coward]

Doctor, you mentioned the ratio of ten women to each man. Now, wouldn't that necessitate the abandonment of the so-called monogamous sexual relationship, I mean, as far as men were concerned?

Regrettably, yes. But it is, you know, a sacrifice required for the future of the human race. I hasten to add that since each man will be required to do prodigious... service along these lines, the women will have to be selected for their sexual characteristics which will have to be of a highly stimulating nature.

Re:Spaceship?

[AGMW]

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?

Re:Spaceship?

[Manfred Maccx]

Could you please send me an application form.

Re:Spaceship?

[M8e]

What I have learned from animes is that you have to have small(weight) teenage girls with big breasts on these kind of ships, and yes they will save space and anything in it while at least one of them is pregnant after using one of those "genetic samples".

Re:Spaceship?

[Anonymous Coward]

Does that count take into account the "red shirts" who get killed in each episode?

Re:Spaceship?

[Z00L00K]

1 man
1599 females

And a set of frozen semen in case the man bites it too early.

Re:Spaceship?

[wagnerrp]

I must confess, you have an astonishingly good idea there doctor.

Re:Spaceship?

[anyGould]

At least one of them should have reasonable singing ability as well - important to sooth the alien armadas.

Re:Spaceship?

[Anonymous Coward]

The more more people on board the more economical it is to modify an engine to run on salty water and carbon rich fuel. Reaction mass will be at a premium when the inevitable 'stretch target' mad managers are in charge.

Re:Spaceship?

[careysub]

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 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.

Re:Spaceship?

[Anonymous Coward]

I'd worry more about the societal issues of a small population stuck on a multi-generational colony ship (namely, it's not a problem natural societies have ever had to figure out, since dissenters have always had a way to leave or be exiled. Can't do that on a ship. If the population is small enough, it's also impractical to imprison anyone long term.)

However, your genetic suggestions (though very good ones) might not be possible to implement yet. The screening is the tricky part, IMO. You'll need to do that for everyone on the ship, including new births, which means you'll need the equipment and training. Once you get a certain distance away from Earth, you'll also need the expertise to interpret the results. And that's not the hard part. The hard part is that inbreeding *creates* new recessive disorders, so ideally you'll actually need to be proactively reading and storing everyone's full DNA so that you can catch new disorders as they appear and add them to the screening process. And you'll need to retain this expertise for many generations, which is hard to do for something like a full medical doctor in a colony ship of only 50-400 people. Oh, and if it's an actual colonization effort, you'll need to keep this work up until the population is much, much larger (ideally, you'd keep it up damn-near-forever).

I suppose it depends on how many generations of isolation are required, and how diverse a gene bank you can start with. It might actually be best to completely detach relationships from genetic parentage: let the medical database decide how many children will be born, when, and with what DNA, and let the people decide who will carry the next child and who will raise it. With a big enough starting pool of stored DNA, this can guarantee a small group can go on for as long as you want it to with zero inbreeding problems.

Re:Spaceship?

[Ngarrang]

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.

Ah ha! That is why in the movie Pandorum, they had 1600 people on board. And here I thought they were just pulling a number out of thin air for a movie plot.

It's an issue of economics

[Anonymous Coward]

We require more vespene gas.

Re:It's an issue of economics

[ThePromenader]

Here's another plate of beans.

From the article: A major drawback

[Suki I]

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.

Re:From the article: A major drawback

[Onuma]

We could just harpoon & tow-cable the leg of Barnard's Star as we swoop by...

Re:From the article: A major drawback

[macson_g]

And by the time it gets there the sensor technology could be so beefed up that we will get better data w/o leaving our cosy solar system.

Re:From the article: A major drawback

[sznupi]

Or, in the time and budget much smaller than this thing would swallow, we might be able to build thousands solar or "artificial" (even if not to such extremes) sails. That could give semi-continuous observation even with just flybys ... plus some might be able to slow down.

Re:From the article: A major drawback

[clonan]

Solar sails can't get up to 12% C.

Therefore we could get near continuous observations in 10,000 years instead of 50....

Re:From the article: A major drawback

[dpilot]

The obvious trick would be to include a mass driver that shoots planetary probes. At the appropirate point of approach start shooting probes backwards, killing as much of the approach velocity as possible. With any luck and perigee/perihelion burns, perhaps the probes could achieve stellar orbit and send back more data.

Re:From the article: A major drawback

[Suki I]

The obvious trick would be to include a mass driver that shoots planetary probes. At the appropirate point of approach start shooting probes backwards, killing as much of the approach velocity as possible. With any luck and perigee/perihelion burns, perhaps the probes could achieve stellar orbit and send back more data.

That would be a good trick, maybe "nano-probes" that could be "shot" at 12.499999% of the speed of light in the opposite direction so they will be slow enough to be captured in orbit by the star?

Re:From the article: A major drawback

[dpilot]

It would be tough, but it's not necessary to stop the probes, just to kill enough velocity to let conventional tricks work. Since we're talking nasty stuff already first shoot the probe - one that includes/deploys a buffer/shield plate - then shoot a nuke. Once they're past the stress of the backward shot they'll still be going too fast, so explode the nuke. It exerts force against the buffer/shield plate, slowing the probe further. Maybe even repeat with multiple seeded nukes. At some point there'll be an appropriate velocity that can be handled by more conventional means.

Or give up on getting a probe into orbit. Simply getting it to pass through the target system at a slower speed is still a win, because it gives more observation time.

How many people?

[VincenzoRomano]

It looks like 99% of the room is used for tanks and engines.

Re:How many people?

[Phoshi]

If you RTFA, it says it's an unmanned probe - so zero people. No offworld colonies for us :(

Re:How many people?

[JasterBobaMereel]

...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 ?

Re:How many people?

[sznupi]

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)

Re:How many people?

[ultrasound]

It may be able to accelerate forever, however the rate of acceleration will tend to zero as your velocity tends to c.

Re:How many people?

[sznupi]

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)

Re:How many people?

[Dragonslicer]

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.

Re:How many people?

[mauriceh]

That is "Bussard" , after Prof. Robert W. Bussard, who postulated it first:

http://en.wikipedia.org/wiki/Robert_W._Bussard

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.

Re:How many people?

[Restil]

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 (probably slightly inaccurate) calculations figure that moving at 10% of the speed of light through interstellar space, it would take almost 10 minutes to accumulate 1 gram of matter, assuming a gathering area of one cubic kilometer. That means.. in 50 years, you will have gathered the combined weight of 26 humans (while travelling at 10% of the speed of light). That doesn't even figure how you got it to go that fast in the first place. Considering how massive such a craft would need to be, an extra 2000 pounds of weight isn't going to make the slightest bit of difference if you just included it when you left home, and not bother with the ramjets at all.

-Restil

Re:How many people?

[Nethemas the Great]

I'd rather fancy it collecting interstellar birds...

Re:How many people?

[Nethemas the Great]

To hell with the rocket equation. It's time to invest heavily in finding a propeller that can propel through the Dirac Sea.

Re:How many people?

[turgid]

I'll see your Buzzard and raise you a Bustard!

Re:How many people?

[turgid]

+1 Funny

Re:How many people?

[JasterBobaMereel]

The design of a Bussard Ramjet the craft itself would be as light as possible, most of it is a scoop which is mostly magnetic fields, so while it would be large it would not be a massive craft, a fusion ramjet has not yet been built but could be very small, and a certain very inefficient fusion bomb produced rather a lot of energy from an estimated 0.6 g of mass ...

Re:How many people?

[JasterBobaMereel]

Solar sails, can accelerate to a useful speed, well if you consider faster than Voyager 1/2 a useful speed, yes they get no acceleration in interstellar space, but a spiral outward course can build up a very large velocity before the heliopause

You seem to be assuming that useful velocity mean that humans could get somewhere in less than a lifetime?

Think Positron Engine Drive

[tyrione]

WSU Positron lab: http://www.cmr.wsu.edu/facilities/webster_547

W.M. Keck Lab

This article and video explains their research: http://wsutoday.wsu.edu/pages/publications.asp?Action=Detail&PublicationID=14531&TypeID=1

Re:Think Positron Engine Drive

[wagnerrp]

Antimatter reactions are ridiculously energetic, with an energy density of some 90PJ/kg. The problem is that there is no known naturally occurring source of antimatter, we have to produce all that we want to use. That makes it nothing more than a battery technology. Add in the inefficiencies of antimatter production, and you're talking about energy requirements equivalent to centuries at our current global consumption rate just to get into orbit. Finding a way to densely store the stuff is just one of many very difficult problems that need to be solved.

Re:Think Positron Engine Drive

[Anonymous Coward]

Now how does this fit into all that?

Re:Think Positron Engine Drive

[lollacopter]

Not to detract from your post, as I suspect it changes little, but there is a naturally occurring source of anti matter.

http://www.nasa.gov/mission_pages/GLAST/news/fermi-thunderstorms.html

Re:Think Positron Engine Drive

[ultrasound]

The problem is that there is no known naturally occurring source of antimatter

Apart from thunderstorms of course.

Re:Think Positron Engine Drive

[sznupi]

At least millennia, and probably millions of years - not centuries. One of CERN pages describes how our total production of antimatter up to this point could power a light bulb for a few minutes (and how an amount for a bomb of fairly normal yield, in the range of typical small thermonuclear one, would take billions of years to produce - since the energy involved would be not too far from the amounts in large orbital launch, I might leave more than enough space for improvement when saying "millennia, and probably millions of years")

Re:Think Positron Engine Drive

[OolimPhon]

Problem solved... just take a thunderstorm with you!

Re:Think Positron Engine Drive

[kiwix]

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.

Re:Think Positron Engine Drive

[Kell Bengal]

Mind you, we aren't really going out of our way to produce large quantities of antimatter at the moment. One wonders how the technology to do so would scale if we mass produced the equipment necessary to synthesize it. Ultimately, producing any product in volume is simply a matter of scaling up the fabrication process. Sure, it would be extremely expensive at the start, but so were computers once upon a time.

Re:Think Positron Engine Drive

[sznupi]

We aren't going out of our way to try doing very many things. That's not merely a matter of choice... (however amusing mass production of particle accelerators would be)

Re:Think Positron Engine Drive

[Nethemas the Great]

One might have argued similar things when we were first trying to concentrate uranium and plutonium... Unless there is a fundamental and prohibitively restrictive energy budget of which I am unaware (perhaps a physics person could chime in...) I wouldn't get too pessimistic just yet. To my knowledge we've only been poking at the margins of anti-matter production for the purpose of study not utility.

Re:Think Positron Engine Drive

[joe_frisch]

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 spectacularly small.

Re:Think Positron Engine Drive

[mikael]

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

Re:Think Positron Engine Drive

[rubycodez]

production is 500 particles per year, perfect. Assuming there would be a way to harvest them, a gram of ionized anti-hydrogen (anti-protons) has 6x10^23 anti-protons. I see a wee bit of a problem there, we need 1.2x10^20 years to get that much using the thunderstorm method, sun will last only 5x10^9 more years.

Re:Think Positron Engine Drive

[GCPSoft]

Well, we may be able to find a second hand warp core, ejected to save a nearly exploding starship, left by a foolish Federation captain, and still not found by the Ferengi somewhere along the way and adapt it...

Absurd

[burisch_research]

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.

Re:Absurd

[sznupi]

http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm

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)

Re:Absurd

[onepoint]

You are thinking like most people, but not like futurist. let's use 1 examples, the guy that keeps on designing those flying cars. Everything I have read about him has come at a cost of spending money to design a specific part, each step has produced an advantage to the general population ( I am also willing to bet that certain parts of the 'segway transport' gyroscope system is in the Wii or an evolution leading to the Wii ). Also we can look at the Dyson vacuum cleaners, expensive tools to get a decent job done. But again very expensive.

then let's look at the Manhattan project, lots of money spent, with a dramatic result, and over time, the research that came from it also lead to better things ( I think HEPA filters were first thought of and designed for the project )

so with that said, let's spend money on some wild goals, most wont work, but some might.

Re:Absurd

[kiwix]

I think the whole point of the study is to see exactly how absurd and/or impossible that task would be. In the end, I am really impressed that current technology could realistically allow us to reach a relativistic speed. I would have assumed that to be impossible and it turns out to be just absurdly expensive. I think that's a very important result.

Re:Absurd

[Anonymous Coward]

Right, slashdot seems to be disallowing my regular account from posting now, no idea why -- therefore I'm posting as AC (in a different browser, cos it seems logout is broken now too!). I am the OP, who posted the Absurd comment.

The Asimov article is great, and I agree with what he's got to say. However, we're all aware that there's an incompatibility between newtonian/einstinian physics and quantum physics. A unified theory may well reveal a whole bunch of stuff that simply never occurred to us previously. For this reason, the incrementalist attitude that Asimov endorses may prove to be invalid. That is the point I was trying to make.

There are all kinds of odd things going on in the universe. We have proven that alpha (the fine constant) is not a constant at all, and we have absolutely no idea why this might be. There are numerous other oddities that we simply cannot explain. (why are the voyager spacecraft slowing down?!)

It seems very clear to me that we are only seeing the tip of the iceberg, when it comes to physics. There's a lot of turtles down there, and we can't see any except the one we're sitting on. Asimov's viewpoint is very dangerous because his assumption is that there is only one turtle, and that science is only about mapping that turtle in ever greater detail. But in truth it's turtles all the way down, baby. Probably.

Moving on to the practicalities of interstellar probes -- it's occurred to me that if we could simply extend our lifespans to an arbitrary degree, this would effectively remove the light-speed barrier. If you could live for 1bn years, then a relativistic trip to Andromeda might actually become bearable. Uploading, anyone? But anyway, regardless of life extension, yes there are almost certainly better ways to explore the galaxy than city-sized probes. We could just send an 'evolved' cellphone-sized instrument package payload, and that would reduce the mass requirements for the delivery vehicle by orders of magnitude over daedalus, thus making the entire project feasible.

Hey and how about some mod points on my original post, please?!

Re:Absurd

[Jane Q. Public]

Ah... but the devil is in the incompleteness! After all, Newton was right... in most cases. It is only at certain extremes that we run into relativity and quantum mechanics, for example. Yet without an understanding of both of those, lasers would never have been designed. (I use that example because the first laser was intentionally designed, as opposed to discovered.)

It is just at these extremes that we find the exceptions, and so far those exceptions have opened doors beyond measure. So your "incompleteness" could still -- and probably does -- hold many wonders of the universe.

RTFA: none

[fantomas]

RTFA:none. Unmanned probe.

Followup

[Anonymous Coward]

If you want a look at what's happening in interstellar travel today, check this out:

http://www.icarusinterstellar.org/

It's basically this Daedalus project updated for the 21st century :-)

Renoir

You Can Take It With You

[Anonymous Coward]

Why bother with the ship? Why not just take our whole solar system with us?

http://www.sfwa.org/2009/12/you-can-take-it-with-you/

Nuclear fission propulsion

[AC-x]

What about using nuclear fission propulsion like Project Orion? We already have the material and technology to make one if a way to launch without causing fallout and EMP disruption could be found.

Re:Nuclear fission propulsion

[CrimsonAvenger]

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....

Re:Nuclear fission propulsion

[drinkypoo]

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

[stjobe]

I don't know where you get your figures from, but according to the Wikipedia page for Specific Impulse, the ISP for an Orion-style drive is 10.000 to 100.000.

Re:Nuclear fission propulsion

[stjobe]

Bah, preview fail. The ISP for an Orion-style drive is 10.000 to 1.000.000.

Re:Nuclear fission propulsion

[stjobe]

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, so yes, it could carry enough fuel for interstellar travel. Your other two points are correct though.

Re:Nuclear fission propulsion

[LWATCDR]

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.

Re:Nuclear fission propulsion

[LWATCDR]

Actually NASA did a study on boosting an Orion into Orbit on an uprated Saturn. It was a smallish Orion but still an Orion.

Re:Nuclear fission propulsion

[drinkypoo]

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.

Re:Nuclear fission propulsion

[LWATCDR]

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.

Re:Nuclear fission propulsion

[drinkypoo]

We have no experience making spacecraft which can last 44 years while supporting humans. That's a stupendously long period of time.

Re:Nuclear fission propulsion

[DerekLyons]

What about using nuclear fission propulsion like Project Orion? We already have the material and technology to make one

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 the key hardware components have been tested even at that level. There's a great deal of hype about Orion, but no substance.

Re:Nuclear fission propulsion

[joe_frisch]

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.

Re:Nuclear fission propulsion

[stjobe]

[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:

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.

Re:Nuclear fission propulsion

[LWATCDR]

Again with the humans. You send humans after the machines go if ever. Even if we had very fast starships that could travel at .5c it would be insane to send humans to what could turn out to be nothing but a life less rock or worse a star with no planets in orbit.
Machines.. You send machines first. Since we have not sent machines yet that is all that I am talking about.

Re:Nuclear fission propulsion

[drinkypoo]

We don't have machines which can meaningfully operate autonomously yet in that context, so we can't do THAT, either. You need humans and we can't send them so there is NO. POINT. TO. INTERSTELLAR. TRAVEL. AT. THIS. TIME.

Re:Nuclear fission propulsion

[LWATCDR]

But you will never send people first unless it is just so cheap, easy, and fast as to just not matter. Also Pioneer is working more or less autonomously and it is near the 40 year mark. It is still sending back data and is many light minutes or hours away so it is pretty much on it's own. We could make a probe that should function for 40 years today. It may do nothing but take pictures and and record radiation levels and try and map the stellar system as it goes through and a bad dash. Hopefully it will also avoid any planets as well. That isn't outside the todays technology.
Dude get over it. Yes Orion can take enough fuel for an interstellar probe just get over making an error and get on with your life and quite trying to make it look like your right. As to there being any point at this time. The cost to data ratio is very high so in that case you maybe correct. If we found earth like planets around AC then that math could change but not likely. I doubt that the world would pay the price which could run as much as all the movie, music, and video companies make in a year just to build a probe to go to another star. That says more about human nature than it does the available technology.

Re:HOW DO I VIEW ALL COMMENTS WITH NEW SLASHDOT?

[hellop2]

You scroll all the way to the bottom and click "Get X More Comments".

Buyer's remorse

[paiute]

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

[cowboy76Spain]

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).

Re:Buyer's remorse

[Targon]

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 projects, and will help mitigate the costs.

Now, you also have to consider that while 100 years may seem like nothing when you are looking at the complete flow of time, look at how far science and technology have come in the past 110 years, from the automobile becomming something common, to flight, to rockets and satellites, and then to landing on the moon. From that perspective, the past 100 years have been fairly eventful when it comes to science and technology. I fully expect that in the next 100 years, we WILL have bases on The Moon, and possibly Mars.

Re:Buyer's remorse

[captainpanic]

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.

Re:Buyer's remorse

[amorsen]

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.

Re:Buyer's remorse

[sznupi]

Are we overtaking anytime soon our existing interstellar probes launched over 30 years ago? (mind you, NOT launched in the fastest way possible - a Saturn V with NERVA upper stage and ion engine & reactor borrowed from the Soviets would give Pioneers and Voyagers a heck of a lot more kick - it was not for strictly technical reasons why we didn't do it ... but, funnily enough, we couldn't do it the "faster way" now!) Are current planes much faster / different than those from half a century ago? Do we build ships defying Archimedes' principle? (come on, that's over 2 thousands years old! Surely it should pass by now)

You really can't assume a technological scenarios depicted in works of fiction. Look at those airplanes (probably influenced by rapid advances in naval technology, plus an unhealthy doze of wishful thinking) from "our" times, as depicted over a century ago. Vs. what reality actually dictates

Re:Buyer's remorse

[onepoint]

Yes, that's true. look at container ships, they are huge ( 10,000 TEU + ) but I can recall when 3500 TEU's were huge. TEU = http://en.wikipedia.org/wiki/Teu

Re:Buyer's remorse

[guruevi]

You could just send them different ways much like the Pioneers and Voyagers.

Re:Buyer's remorse

[Anonymous Coward]

Brilliant, so you can 'bravely' volunteer to be the first to reach a new world, to do all the work, to build a society, etc. Of course, you'll know that by the time you get there, there will be McDonalds and Starbucks, and you'll be received as heroes - possibly near-mythical heroes - eventually turning up after thousands of years.

Re:Buyer's remorse

[natehoy]

Partly because it's expensive by nature, and partly because we haven't done another one. We aren't refining the technology, and instead would have to start pretty much from scratch with newer technology.

If we had been doing moon landings every 5 years, it would be a routine now, having undergone continuous refinement and improvement with practical experience under our belts. Ships wouldn't have to be built as single-purpose one-offs, we'd have a supply base established there, and we might even have a moonbase instead of the fragile and small ISS. We'd also have more practice landing craft on other planets and probably have more than a couple of long-past-shelf-life probes on Mars, and maybe even a few probes on other planets in the solar system.

Re:Buyer's remorse

[Anonymous Coward]

No, only our information technology has progressed so much. Our physical technology is very much constrained by the fact that we have to keep using more and more energy. You need energy to move mass. You don't need a lot of energy to flip a bit, and the energy we need to practically flip a bit is going *down* towards the fundamental limit. In one hundred years, we'll actually have *less* energy at our disposal. This ain't Star Trek, and we burn *OIL*.

Re:Buyer's remorse

[kryliss]

So that's where George Lucas got the idea for Jabba the Hutt's little flying sand barge...

http://devan1.tripod.com/Pics/Barge.jpg

Re:Buyer's remorse

[F.Ultra]

I dimly recall some science fiction works with this theme.

There is probably several other references but one that comes to mind is The Restaurant at the End of the Universe where this situation is discussed at the beginning if my memory don't fail me.

Re:Buyer's remorse

[BitZtream]

History proves that simply isn't true.

Was there already a faster space craft to get to the moon when we landed on the moon?

By the time you get the first one built, the second one may be under construction, but it will be built using knowledge gained from building the first. And as the first sets out on its mission, and things go right or wrong, that knowledge will be integrated into build #2 (or #3 or whatever).

If you keep saying 'wait 50 years and we'll have something so much better that it'll be quicker than waiting 50 years' ... you'll always be waiting 50 years and you'll never actually go anywhere.

What about the knowledge we'll learn about long term space flight on the first ship trying to get to some far off place? If we keep waiting to get there quicker, we'll never know what the situation is.

We can now fly all the way around the world in a matter of days. Do you really think the original human sailors and travelers should have waited till the last 100 years to start moving around the world because it would be so much faster now?

Re:Buyer's remorse

[Patch86]

For one, that assumes that you'd want to send every interstellar probe you build to the same destination. The galaxy has several billion prime destinations to choose from (with at least hundreds of locals on scientific wish lists for a fly-in visit). The probe you build 20 years later can always be sent elsewhere, and you can still enjoy double the science without the first probe being made redundant.

More importantly though, it has now been 42 years since Neil and Buzz set foot on the moon. Could we today do any better? Would Apollo 11 in the 21st century be quicker, or carry more cargo? Voyager 1 is just now becoming our first ever spacecraft to study the heliopause first hand, 34 years after launch, and will hopefully go on to be the first ever scientific equipment to directly study interstellar space and the interstellar medium. At what point are our new, mega high-tech probes going to overtake it and make it redundant? Not within the craft's lifetime, that's for sure. Predicting that our space tech is going to go out of fashion every couple of decades is nothing but a quaint throw-back to the idealistic 60's. Things will always improve, but I'm not sure we've got any earth-shattering breakthroughs in store for us in the near future.

Re:Buyer's remorse

[rubycodez]

this is why we still burn oil and coal

Re:Buyer's remorse

[Anonymous Coward]

Why would you send SpaceShip 2.0, 3.0, 4.0, etc. all to the same place?

If each one is bigger and faster, wouldn't that naturally make it a better contender for a location further away than the last? In this scenario, instead of several ships already present in one location, you have several ships arriving at several locations at close to the same time.

Or hell, send the humans, then send the "faster" ship unmanned with additional supplies and/or robots.

Automation has a long long way to go

[tm2b]

I have to say, it's depressing that at this point we can't even get a solar sail to come out of a can in orbit reliably.

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

[Sockatume]

I think you'll find that we can do that, if by "we" you mean the human race. IKAROS has passed Venus, and is still going strong.

Re:Automation has a long long way to go

[Anonymous Coward]

Yes, IKAROS deployed, but Akatsuki (PLANET-C), the other spacecraft they sent to Venus missed its orbit.

So I reckon the reliability argument still stands.

We should build an interstellar probe

[Baron_Yam]

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.

Re:We should build an interstellar probe

[Anonymous Coward]

We're nowhere near this capability. Sorry, but Space Nuttery is going to have to wait for life extension to work first.

Intergalactic Behemoth

[Anonymous Coward]

SUCH a poor understanding of the subject...

And a flash viewer, WHY? What have they gained from using flash for this? Un-scrollable text, that's what!

Re:Intergalactic Behemoth

[Java Pimp]

Nah, the text is scrollable. You just have to go back to 1995 and actually use the scroll bar...

Daedalus class

[rossdee]

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

Re:Daedalus class

[mibus]

Pssht. You humans and your TV shows.

It's this one: http://memory-alpha.org/wiki/Daedalus_class :)

I strongly disagree

[captainpanic]

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.

Re:I strongly disagree

[Kell Bengal]

Interestingly, the 'small scale' project that is the ISS happens to be the single most expensive object. That's a hopelessly small craft compared to an interstellar vehicle.

Re:I strongly disagree

[the gnat]

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 this point, it would take centuries for Daedalus to become economically feasible, let alone practical.

Re:I strongly disagree

[Nethemas the Great]

In singular perhaps, but not in aggregate. US DoD funding for one year dwarfs the ISS. I personally would rather invest in something that can pay dividends even if the payout is some distance off. The slaughter of man and the destruction of infrastructure doesn't fit that bill. Stop making swords, start making pens, and go put the savings to productive use.

Re:I strongly disagree

[MozeeToby]

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 to get to orbit, you're probably going to want to mine for materials and construct as much of the ship outside Earth's gravity well as possible. That means NEO's being landed on, mined, maybe even colonized. Of course, if you have mining colonies spread around the solar system you're going to need the engines and technology to transport people and material between them.

Done this way, you could move towards an interstellar probe step by step, with each step providing a tangible and immediate benefit to the population of the planet. Keep your eyes on the long term prize, but always keep your hands working on something that people can appreciate today.

Miniaturization

[captainpanic]

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, because they might pay themselves back easily if the whole project becomes smaller).

Re:Miniaturization

[Geoffrey.landis]

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.

Re:Miniaturization

[Anonymous Coward]

I don't know what the mass of the intended payload was, but I doubt it was more than a few kilograms. The major problem with trying to get accelerated to a significant portion of the speed of light is that the fuel required to get you there is far more massive than the payload you are trying to accelerate. FTA, it sounds like they wanted to hit .12c, so there's not much you could do to cut down on the size.

Re:Absurd, let's wait

[NEDHead]

This line of thinking would have killed the PC market on Day 1.

Pointing a sign

[mattr]

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..

Re:Pointing a sign

[AGMW]

... can we currently afford to build it ...

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.

Re:Pointing a sign

[MrKaos]

Great! It will be a big sun-hot arrow pointing right back at us saying, "Here are some young pushovers!"

Indeed. At the very least we would have to be engaged in building our own planetary system, this would be the minimum level of space faring we are engaged with before a project like this is even feasible. I doubt it would happen any other way than being constructed in orbit. So we should most certainly be at some stage of space faring maturity ourselves, I sure the project designers only have their project goals as a consideration though.

I think though that just planning the project has value itself and demonstrates how far away from actual interstellar flight we are with existing state of the art, though I wonder what the next generation interstellar probe will be called, Icarus II?

Simple...

[Anonymous Coward]

All we need to do is build bigger telescopes to increase the mass of the observable universe !

Re:1600?

[cdpage]

where did you get that number from?

Bad name?

[GodfatherofSoul]

You'd figure that'd be a bad omen if you're considering flying to another sun.

Re:Bad name?

[wagnerrp]

Daedalus is the one who survived. Icarus would be the spacecraft that actually tried to enter orbit, and got burned up in the star.

A 100 years may be too late!

[AGMW]

... 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 unlikely to me (too be clear, it seems like a logical extension of what's happening now!). How long have we got? well interestingly, the figure of 100 years had been bandied about. That may well just be the _nice round number syndrome_, but at some point it may be too late. That would be very sad because then the human species is doomed.

We really need to be thinking about getting off this rock sooner rather than later ...

(Sorry about the underscores, but italics don't seem to be working!)

Re:A 100 years may be too late!

[Anonymous Coward]

Right, slashdot seems to be disallowing my regular account from posting now, no idea why -- therefore I'm posting as AC (in a different browser, cos it seems logout is broken now too!). I am the OP, who posted the Absurd comment.

I totally agree with you. Getting off the rock is the absolute priority, not some fanciful interstellar probe. Let's build that damned space elevator asap! This is surely a first step in building an interstellar probe, in any case. But far more important than squandering our efforts on going to another star, is ensuring the continuity of our species.

Tau Zero

[Geoffrey.landis]

For those interested, the Tau Zero Foundation (referenced in the text) does have a website, www.tauzero.aero/

That's the nutty thing about this

[sean.peters]

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.

Re:That's the nutty thing about this

[rubycodez]

why do you think no useful science could be done at 10% C. optical telescopes and spectroscopy would still work, but with blue and redshifting which can be corrected. No problem

Re:That's the nutty thing about this

[sean.peters]

I was exaggerating - sure, you could do the kind of thing you're talking about, and that really would be useful. But you'd only get results for a few days, and then your probe would blow right past the system. The probe would cost an unimaginable sum of money anyway - why not spend the extra dollars to make it able to decelerate? You'd be able to get a lot more out of it. I just don't think it's worth it to spend so much on a probe that sails right through the target system so quickly.

The obvious difference here

[sean.peters]

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.

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 the buck is laughably small. The expense of building this thing would be beyond staggering, and what you'd end up with is some closeup pictures of Barnard's star. Nice, but...

Why the hell couldn't they build in the capability to slow the damn thing down? If you could go into orbit around the star you might have something worth doing.

Not in our lifetime...

[Anonymous Coward]

Researching alternative forms of propulsion is a must (disappointed that the BPP didn't receive more funding), but I don't think we'll be building any sort of interstellar probe in the foreseeable future. It would be a massive waste of resources considering we've hardly begun to explore our own solar system, and what new data can we really hope to get out of a flyby? The composition or actual mass of our neighboring stars? The evolutionary stage at which those particular systems are in? I don't see the value.

If we're going to travel to another star system for extensive research then I'd imagine that it would be a manned (likely a no return) mission involving families that are willing to devote their lives to such an exploration, not just for the sake of doing a flyby. I can certainly see us doing just that if we happen to find an Earth-like planet within 50 or so light years, which is something I'm almost positive we'll discover in our lifetime as we get more precise views of exoplanets.

An unmanned flyby? No one in their right mind is going to sign off on such a project, at least not with taxpayer funding.

Laser propulsion

[Anonymous Coward]

There is a design for a laser powered one with a pretty good speed,
which I forget of course. We build a super massive laser near the sun.
It pushes the sail of the probe toward a nearby star. To decelerate the
probe detaches the large outer sail ring and rotates 180. The reflected
light from the outer ring is focused on the remaining sail to slow it down.

Biggest difficulty is the political will to build, and perhaps more importantly
maintain the super laser for the years of the trip.

Nils K. Hammer

Re:HOW DO I VIEW ALL COMMENTS WITH NEW SLASHDOT?

[Fnkmaster]

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
{
position: absolute !important;
}

li.comment
{
border:solid 1px grey;
-moz-border-radius-topleft:10px !important;
left:20px;
width:95%;
}

}

The merry-go-round broke down.

[westlake]

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.

In 1900 there was a faith in "Progress" we no longer have.

We know that things can disastrously wrong. In tech. In politics. In business and finance.

Maybe better tech will be available in 100 years. But you can't be certain of that.

spaceball -1

[demonbug]

I wouldn't trust that probe near my planet. Looks like it was built by the kind of people that would steal your atmosphere.

On the plus side, I'm pretty sure I know the combo to their luggage.

Daedalus is a woefully inefficient design.

[Jane Q. Public]

If we can assume that there exists an engine that is capable of interstellar travel, e.g., matter/antimatter, then the design of Daedalus is hopelessly out of date.

The problem with designs like this is that the more fuel you need, the more structure it entails, to hold and contain all that fuel and the rocket it pushes and especially the payload. It all has to be braced against acceleration. The more structure, the more fuel needed in turn, needing even more fuel, and so on. It's not an infinite loop by any means but the numbers go up very quickly.

Long ago, Powell and Pellegrino, with their "Valkyrie" project at Brookhaven Labs, showed that if you are not launching from a deep gravity well (i.e., the surface of a planet) it is vastly more efficient to PULL your payload. The engines go up front, and pull the payload along on cables. He later used this design in one of his novels, which isn't relevant here, but the cover has an artist's rendition of the Valkyrie type of vehicle. James Cameron, in an attempt to be scientifically accurate, also used a somewhat stylized variant of the Valkyrie design for his spaceship in the movie Avatar. (Again not directly relevant, but it shows that the science behind Valkyrie has become accepted by the mainstream.)

The pull design drastically reduces the mass of infrastructure needed to build the rocket, which in turn reduces the amount of fuel needed, or alternatively allows more fuel to be carried and used on the trip.

Re:Daedalus is a woefully inefficient design.

[Jane Q. Public]

That sentence should have read: "The more structure, the more fuel needed in turn, requiring even more structure, and so on."

fusion-powered starship

[Anonymous Coward]

An fusion-powered starship need to be sized about five floor.
http://tinyurl.com/nuclear-fusion-starship

fusion-powered starship

[rbrtwjohnson]

An fusion-powered starship need to be sized about five floor. http://tinyurl.com/nuclear-fusion-starship