Earth-sized planet found just outside solar system

Oct 16, 2012 by Seth Borenstein
This artist’s impression shows the planet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Alpha Centauri B is the most brilliant object in the sky and the other dazzling object is Alpha Centauri A. Our own Sun is visible to the upper right. The tiny signal of the planet was found with the HARPS spectrograph on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile. Credit: ESO/L. Calçada

(Phys.org)—European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system—the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile. The results will appear online in the journal Nature on 17 October 2012.

Alpha Centauri is one of the brightest in the southern skies and is the nearest stellar system to our Solar System—only 4.3 light-years away. It is actually a triple star—a system consisting of two stars similar to the Sun orbiting close to each other, designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri. Since the nineteenth century astronomers have speculated about orbiting these bodies, the closest possible abodes for life beyond the Solar System, but searches of increasing precision had revealed nothing. Until now.

"Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days," says Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper. "It's an extraordinary discovery and it has pushed our technique to the limit!"

This wide-field view of the sky around the bright star Alpha Centauri was created from photographic images forming part of the Digitized Sky Survey 2. The star appears so big just because of the scattering of light by the telescope's optics as well as in the photographic emulsion. Alpha Centauri is the closest star system to the Solar System. Credit: ESO/Digitized Sky Survey 2

The European team detected the planet by picking up the tiny wobbles in the motion of the star Alpha Centauri B created by the gravitational pull of the orbiting planet. The effect is minute—it causes the star to move back and forth by no more than 51 centimetres per second (1.8 km/hour), about the speed of a baby crawling. This is the highest precision ever achieved using this method.

Alpha Centauri B is very similar to the Sun but slightly smaller and less bright. The newly discovered planet, with a mass of a little more than that of the Earth, is orbiting about six million kilometres away from the star, much closer than Mercury is to the Sun in the . The orbit of the other bright component of the double star, Alpha Centauri A, keeps it hundreds of times further away, but it would still be a very brilliant object in the planet's skies.

This video is not supported by your browser at this time.
This video shows an imaginary journey from Earth to the Alpha Centauri system. As we leave the Solar System we see the familiar constellation figures including the Southern Cross (Crux) and the bright stars Alpha and Beta Centauri. As we approach Alpha Centauri we pass a faint red star, this is Proxima Centauri, the closest star to Earth and the faintest component of a triple star system. The final part shows the bright double star Alpha Centauri A and B with the Sun visible in the background. Alpha Centauri B is known to be orbited by an Earth-mass planet, the closest exoplanet to the Solar System. Credit: ESO./L. Calçada/Nick Risinger

The first exoplanet around a Sun-like star was found by the same team back in 1995 and since then there have been more than 800 confirmed discoveries, but most are much bigger than the Earth, and many are as big as Jupiter. The challenge astronomers now face is to detect and characterise a planet of mass comparable to the Earth that is orbiting in the habitable zone around another star. The first step has now been taken.

"This is the first planet with a mass similar to Earth ever found around a star like the Sun. Its orbit is very close to its star and it must be much too hot for life as we know it," adds Stéphane Udry (Geneva Observatory), a co-author of the paper and member of the team, "but it may well be just one planet in a system of several. Our other HARPS results, and new findings from Kepler, both show clearly that the majority of low-mass planets are found in such systems."

"This result represents a major step towards the detection of a twin in the immediate vicinity of the Sun. We live in exciting times!" concludes Xavier Dumusque.

Explore further: Planet-forming lifeline discovered in a binary star system

More information: DOI: 10.1038/nature11572

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StarGazer2011
3.4 / 5 (17) Oct 16, 2012
roadtrip!
Gunzo
3.9 / 5 (10) Oct 16, 2012
I'll bring the red licorice.

This is pretty cool news.
gopher65
4.2 / 5 (10) Oct 16, 2012
Hopefully this is a large multiplanet system, with planets orbiting all three stars:). That might eventually spur direct exploration of Alpha Centauri.

Even discounting any unlikely breakthroughs that allow realistic relativistic or FTL travel (both of which are unlikely at any reasonable level of technology), it's close enough that it's entirely conceivable that we could get there inside 40 years, using nothing more direct extensions of current technology.
hopefulbl
2.7 / 5 (6) Oct 16, 2012
now the funding will appear from all sources private and government to develop new never before imagined propulsion systems.
Cave_Man
1.3 / 5 (12) Oct 16, 2012
the aliens are already here, the proof is out there and obvious. never stop imagining new possibilities.
keep yourself you.
TheGhostofOtto1923
3.1 / 5 (31) Oct 16, 2012
the aliens are already here, the proof is out there and obvious. never stop imagining new possibilities.
keep yourself you.
Thank you David Icke.
LordKinyambiss
4.2 / 5 (5) Oct 16, 2012
The real significance of this discovery is that it refines the methods making it possible to find a viable destination that is close enough to contemplate exploring, even if it takes 100 years. If additional planets are discovered in the Centauri system then you can bet investment will be made in the technology to get us there>>
Jonseer
2.8 / 5 (6) Oct 16, 2012
Now this has to be the biggest news by far of all the news we've ever heard about extra-solar planets.

The fact that it orbits so close is irrelevant. As the article says it is likely only one of a multiplanet system.

No other interstellar news has ever been so big.

So why so quiet in the media at large???
Sherrin
4 / 5 (4) Oct 16, 2012
Jonseer - methinks the media is qette because they got their fingers burnt covering our last attempt to get to Alpha Centauri.

All that money, hardware, time and effort wasted thanks to that dastardly Dr. Smith.
astro_optics
2.7 / 5 (7) Oct 16, 2012
They should have been looking there in the first place :P
PhotonX
5 / 5 (3) Oct 16, 2012
I'm as excited as anyone to learn there are planets this 'close', but come on. We have a big handful of worlds within our own solar system that have barely been glanced at, by just a couple of world powers. I think it's wildly overenthusiastic to expect missions to Centauri within any of our lifetimes.
.
I'd be happy to be wrong about this, but I'm certain I will be dead by then, so I guess I don't have much skin in the game..
VendicarD
4.5 / 5 (4) Oct 16, 2012
Probability zero.

"Hopefully this is a large multiplanet system" - foofie

The minimum equivalent distance between the A and B components is the same as the distance from the sun to Saturn. The farthest distance is roughly equivalent to the distance to Pluto.

Anything within that region will be swept clear.

And if there are to be stable orbits they would have to be very close to their stars. Much closer than earth in order to prevent them from being thrown out of the system.
Jeddy_Mctedder
2.4 / 5 (8) Oct 17, 2012
ive spent plenty of time studying the knowledge we possess about alpha centauri and the nearest stars to our sun. there is still a scientific possibility that a y class brown dwarf ( a bigger version of jupiter ) may be out there floating somewhere between alpha centauri and earth.

while the wise mission has ruled out the possibility of there being a whole universe full of brown failed dwarfs, there is a good chance many of them out there are still invisible to us.

that said, such a star would not provide enough heat to a possible orbiting planetary system to be of much use in creating a biosphere as we would recognize it.

still, pretty amazing stuff. in 2 years we will have our first probe visiting pluto. between the time we sent the probe and when it gets there, the target was reclassified from being a planet to being a planetismal or tno or whatever have you, and a number of more companion objects orbiting it have been discovered. should be interesting when we get there.
gwrede
3 / 5 (6) Oct 17, 2012
The first step has now been taken.
I resent this kind of exaggeration. This is one small step in the long journey that started with the first serious attempt to find an exoplanet, finding some large ones, then some smaller ones, now on very near us -- and then continuing with finding many earth-size exoplanets, then a few of them around stars like our Sun and in the habitable zone, and ultimately some that show spectral hints of rock and water.

This belongs to the same category as "For the first time", and "World's (best/largest/sharpest/smallest/whatever)". Many of the "for the first time ever" things I have already read as a child in Scientific American, and some previously even right here, on PhysOrg.

All this erodes the credibility of science, and popular science writing in particular.
Birger
5 / 5 (1) Oct 17, 2012
Only stable orbits are at approx. 1 AU and less. Since this planet has migrated close to the star, this fate has probably befallen all other terrestrial planets born in this close zone.
DaveMart
4.2 / 5 (5) Oct 17, 2012
'Just outside' the solar system!
That sounds like 'let's pop over to borrow a cup of sugar' close!
The light years have shrunk since I was a boy!
EBENEZR
2.3 / 5 (3) Oct 17, 2012
I don't want to be a party pooper, and exoplanets are interesting don't get me wrong, but I think the celestial bodies in our own solar system are enough to go on for the time being. Personally I think the moons have much more potential for interesting study than the planets (bar Earth), but that aside there is so much yet to learn closer to home and much more potential for observation, whether that's getting humans to Mars or a lander to Europa and Titan. Better propulsion systems would be a good start, as hopefulbl suggested.
Blakut
1 / 5 (5) Oct 17, 2012
Scattering in the photographic emulsion?? What is this, the 60's? It says right there DIGITIZED sky survey.
visual
2.6 / 5 (5) Oct 17, 2012
That video is so fake and unrealistic. I much prefer the game version. In real time.
Unfortunately I hear some Julian Fleetwood guy stole the idea from Wobbler and tried to make a run with it.

Next thing you know, Sid Meier's version will also turn out to be realistic.

It is interesting how much planets crop up lately. Even in a triple-star system, and the closest one to us (so more or less the very first one that we are able to even look at with this level of detail), what are the odds....
yyz
4.6 / 5 (9) Oct 17, 2012
"Scattering in the photographic emulsion?? What is this, the 60's? It says right there DIGITIZED sky survey."

The Digitized Sky Survey uses large(14"x14") photographic plates, as its source material. These plates, obtained with the Oschin Schmidt at Palomar Observatory or, in this case, the UK Schmidt Telescope at the Anglo-Australian Observatory, were subsequently digitally scanned to produce the DSS: http://en.wikiped...y_Survey
tkjtkj
1 / 5 (2) Oct 17, 2012
re: Jonseer : "
antialias_physorg
4 / 5 (4) Oct 17, 2012
I'll bring the red licorice.

Forget the licorice. Pack some sunscreen (factor 10 billion or thereabouts). This thing orbits so close to its star that you wouldn't see much sky - only star.

No other interstellar news has ever been so big.

Because this is 'just' one of the hundreds of other exoplanets discovered? The only thing that sets it slightly apart is that it's pretty small (owing to the relative closenes of (and to) Alpha Centauri...other such small bodies are still not within our ability to detect unless they happen to pass in front of their star in direct line of sight to us while we just happen to look that way)

about the speed of a baby crawling

Damn. Where do they get these analogies from? Is there an official list? And I'm betting one of the authors sat down and actually measured their baby's crawling speed.
tkjtkj
1 / 5 (2) Oct 17, 2012
re: Jonseer : "
loneislander
1 / 5 (2) Oct 17, 2012
Now this has to be the biggest news by far of all the news we've ever heard about extra-solar planets.

The fact that it orbits so close is irrelevant. As the article says it is likely only one of a multiplanet system.

No other interstellar news has ever been so big.

So why so quiet in the media at large???


Fox, CNN, ABC, CBS, CBC, ABC... what say more?
neurogalactus
1.6 / 5 (7) Oct 17, 2012
Effective FTL travel will be possible within 40-50 years. That's what I would guess if I was to bet. I say "effective", as opposite to "literal", because the spacecraft won't really exceed the speed of light. It's the knowledge of the underlying gravito-magnetic structure of the galaxy, with all its nodal points, that will enable us make large-distance jumps. Everything in the universe vibrates, everything has nodal points, everything is structural. A new physics will show this plainly, once all that classical reductionist renormalization mumbo jumbo is abandoned, and more fundamental things are studied instead. Now, what I'm saying is just an assumption, nothing more, but I'm quite confident it will rapidly unfold into a reality, in the coming decades. The nature of distance and displacement, the nature of motion and golden-mean patterns in space and time (eg Earth-Venus 5-fold resonance), all that is very fundamental, yet poorly understood. Once grasped, it will get us to the stars.
TheGhostofOtto1923
2.8 / 5 (26) Oct 17, 2012
Forget the licorice. Pack some sunscreen (factor 10 billion or thereabouts). This thing orbits so close to its star that you wouldn't see much sky - only star.
Stardate 2256 - A robotic antimatter production facility was successfully established on the dark side of Alpha Centauri Bb, nicknamed Foofie, and has begun storing fuel for generation ships scheduled to arrive in the coming years.

Another Wonderous Victory for our Glorious Empire in its Noble Efforts to Seed the Quadrant. Somebody has to.
Sonhouse
5 / 5 (2) Oct 18, 2012
So why do they have a problem just saying a planet was found close to Alpha Centauri B? Why do they say "Just outside the solar system"?

Do they think people are so stupid they never heard of Alpha Centauri, the closest star and a triple star system?
visual
3.4 / 5 (5) Oct 18, 2012
Damn, I must be really getting old if no one seems to get the references from my previous post... and some 'lite' guy even took it so literal as to click the "i'm braindead" button.
Pkunk_
3 / 5 (4) Oct 20, 2012
@antialias_physorg said -
Forget the licorice. Pack some sunscreen (factor 10 billion or thereabouts). This thing orbits so close to its star that you wouldn't see much sky - only star.

Since it is orbiting so close it could possibly be tidally locked with one side permanently facing its star. This would make for some interesting "weather" , also keep in mind Alpha B is only 40% as bright as the sun.
The far side of the planet would receive a reasonable amount of light from Alpha Cen A , but probably not enough to blot out the stars.
antialias_physorg
not rated yet Oct 20, 2012
This would make for some interesting "weather"

That close to the sun I wouldn't expect any atmosphere (and therefore no weather).

For comparison: Mercury is more than ten times further away from our sun than this rock is from its.

From mercury our sun looks 2.5 times bigger (and for the life of me I can't even find a semi-scientifically-accurate artist's impression of that on the web).

Whether it's tidally locked is really unknown. Like mercury it may just have some odd periodicity.
Pkunk_
1 / 5 (2) Oct 20, 2012
This would make for some interesting "weather"

That close to the sun I wouldn't expect any atmosphere (and therefore no weather).

I correct myself - I meant space weather of course. One side of the planet would be 1000C , and the other below 0 . Since any atmosphere would boil away there would be no way for the heat to conduct to the other side , unless it's a lava hell-hole like Io .

Since its so close to the star it could make for some interesting effects on the far side when there are solar flares.
CapitalismPrevails
1 / 5 (3) Oct 20, 2012
How long would it take VASIMR to get to Alpha Centauri?
antialias_physorg
not rated yet Oct 20, 2012
How long would it take VASIMR to get to Alpha Centauri?

Forget about that. Anything that uses reaction mass is pretty much a no-go for interstellar travel.
The amount of fuel you would have to carry would be enormous to get up any kind of decent speed (and the more fuel you carry the less acceleration per kg of fuel you get)
...and don't forget you need twice the fuel you use to accelerate - because you need to decelerate before you get there.

That...and the fact that even if you pack such a motherhuge amount of fuel then you're going to go so slow that it's going to take thousands of years to crawl there.
Fleetfoot
not rated yet Oct 20, 2012
How long would it take VASIMR to get to Alpha Centauri?


VASIMR is designed for solar power, it's intended for use within the Solar system. Stick the mass of a nuclear reactor on the front and the unproductive mass (shielding etc) will wreck the efficiency.
CapitalismPrevails
1 / 5 (3) Oct 20, 2012
antialias, maybe if a craft had someway to refuel while in flight ,like the theoretical Bussard ramjet, it wouldn't have to carry as much fuel.
NeutronicallyRepulsive
1 / 5 (1) Oct 20, 2012
When do I launch? :)
antialias_physorg
5 / 5 (2) Oct 20, 2012
maybe if a craft had someway to refuel while in flight

That's a bit of a problem in space. Space is really, really empty.
The bussard design is really, really heavy.
Meaning: even if you collect the occasional atom you encounter with 100% efficiency (and I think that no one can claim to even pretend to know how that's supposed to work)the acceleration you will get is very, very small.

Also a bussard ramjet is big and flimsy. Get up to speed of 0.1c (its theoretical maximum) and a simple 1mm grain of dust will shred it with the energy of about 7 tons of TNT on impact.

Also you can't steer such a huge contraption as the accelerations of it are well below 1g.
(E.g. if you could see such a 1mm dust speck at Earth-Moon distance coming your way you'd have, (at 0.1c) 10 seconds to get out of the way. With a multi (hundred) kilometer diamater dish? No way.
kevin_hingwanyu
2.3 / 5 (3) Oct 21, 2012
"Proxima Centauri, the closest star to Earth and the faintest component of a triple star system. The final part shows the bright double star Alpha Centauri A and B with the Sun visible in the background

Is the Alpha Centauri a triple star composed of A, B and Proxima ? I search wikipedia.com find that distance between AB and Proxima = 0.24 ly. Also, Alpha Centauri AB and Proxima are probably gravitationally bound.

Fleetfoot
not rated yet Oct 21, 2012
The amount of fuel you would have to carry would be enormous to get up any kind of decent speed (and the more fuel you carry the less acceleration per kg of fuel you get) ... and don't forget you need twice the fuel you use to accelerate - because you need to decelerate before you get there.


Good points but for very high speeds, there is a little detail correction. Take hydrogen fusion as an example. Suppose you have a payload of the fusion plant, fuel tank and payload with a total mass of 1 tonne (just scale to realistic figures). To change speed by a given delta V needs some ratio of fuel to mass. For example suppose that is 9:1 for an acceptable trip time, you need 9 tonnes of hydrogen to slow down. The cruising mass is then 10 tonnes so you need 90 tonnes to get up to speed. The total is much more than twice the deceleration value.

If the ratio is much less than one, the factor of twice is correct of course.
Jonseer
3.7 / 5 (3) Oct 21, 2012
Do they think people are so stupid they never heard of Alpha Centauri, the closest star and a triple star system?


Umm, unless you specifically meant readers of phys.org, generally speaking a good guess about the percent of Americans who would be clueless as to what you are talking about is 98%

The percentage of Americans who find any type of science interesting is vanishingly small relatively speaking to other interests that occupy the minds of the general public.

If you spent some time asking people who aren't sci fi nuts, you'd probably find more people who know about Centari, knew about it from Centari Prime of Babylon 5 rather than as the closest star system to our own.
Jonseer
4 / 5 (4) Oct 21, 2012
They should have been looking there in the first place :P


Actually they DID look there first, and looked there repeatedly and didn't find anything, and if you were to have asked an astronomer a few years ago you would have been told there were no planets to find at the Centari system.

Nothing says better that the "facts of Astronomy" are only as certain as the technology of the day" than this discovery.

All too many people take what they hear an astronomer say today as the final word, when the "facts" in astronomy are a moving target, moving along with the advancement in the technologies that we use to see the Universe.

That's a hard thing for people who like to believe "facts are a proven thing" to understand or accept, but it's the truth.

In science, the province of facts, facts are only as proven as the limits of technology used to unsuccessfully falsify them.

TheGhostofOtto1923
3.8 / 5 (16) Oct 21, 2012
@antialias
motherhuge amount of fuel then you're going to go so slow that it's going to take thousands of years to crawl there.
-So you take issue with any of these, the result of govt-funded studies by experts?

"Fusion rocket starships, powered by nuclear fusion reactions, should conceivably be able to reach speeds of the order of 10% of that of light, based on energy considerations alone."

"An antimatter rocket would have a far higher energy density and specific impulse than any other proposed class of rocket. If energy resources and efficient production methods are found to make antimatter in the quantities required and store it safely, it would be theoretically possible to reach speeds approaching that of light."

"Beamed propulsion seems to be the best interstellar travel technique presently available, since it uses known physics and known technology that is being developed for other purposes"
TheGhostofOtto1923
3.8 / 5 (16) Oct 21, 2012
(E.g. if you could see such a 1mm dust speck at Earth-Moon distance coming your way you'd have, (at 0.1c) 10 seconds to get out of the way. With a multi (hundred) kilometer diamater dish? No way.
Well perhaps instead of a full Alcubierre drive it might be easier to warp space-time in front of the ship only, in order to redirect and slow both H2 and dust. The mix could be brought into the range of a magnetic funnel which would capture the ions while the dust could flow safely past the ship.
Fleetfoot
5 / 5 (1) Oct 22, 2012
"Fusion rocket starships .. based on energy considerations alone."


Based on energy alone, that is true.

"An antimatter rocket .. If energy resources and efficient production methods are found to make antimatter in the quantities required and store it safely,"


The problem is not manufacture or storage, it is shielding the fuel from cosmic rays. A single particle getting through would cause a small explosion blasting a significant amount of fuel onto the container.

"Beamed propulsion seems to be the best interstellar travel technique presently available, since it uses known physics and known technology that is being developed for other purposes"


True, but Forward's analysis described a Fresnel lens to create the beam which requires a point source, not the Sun. It could be done with a microwave synthetic aperture antenna but what size must it be to get the Rayleigh distance to several light years? The sail is comparable but could carry a negligible payload.
antialias_physorg
5 / 5 (1) Oct 22, 2012
The cruising mass is then 10 tonnes so you need 90 tonnes to get up to speed. The total is much more than twice the deceleration value.

Good catch. I was trying to avoid all the 'exponential need of fuel' type of argument (because I was too lazy to do the math, to be honest).

-So you take issue with any of these, the result of govt-funded studies by experts?

I was responding to the 'VASIMIR type of drives'-question (and it's refueling option via bussard ramjet)

Fusion and antimatter drives are still science ficton.
TheGhostofOtto1923
3.8 / 5 (16) Oct 22, 2012
Fusion and antimatter drives are still science ficton.
-But much more feasible than a bussard ramjet. These have been used in scifi but have been conceived by scientists and engineers who have spent time and money researching them and writing papers and such. Pulsed nuclear propulsion for instance has been well-fleshed out.

And these experts say that these systems could produce relativistic velocities. Yes? Check the sources.
antialias_physorg
5 / 5 (1) Oct 22, 2012
-As opposed to a bussard ramjet?

A busard ramjet does not contain any parts that are currently unavailable.
And as I said: it was meant in reply to a question about VASIMIR engines that could be 'refueled along the way' - not as a comment on ('conventional') ramjet busrad fusion engine designs.

VASIMIR is better than ion drives. Though in interplanetary/interstellar space mostly only light atoms are available which drastically reduces its effectiveness.

Until and unless we come up with something better than this there's no point in dreaming about sending probes just yet.
TheGhostofOtto1923
4 / 5 (16) Oct 22, 2012

A busard ramjet does not contain any parts that are currently unavailable.
?? What currently-available parts can generate the kind of kilometers-wide magnetic fields needed to collect interstellar hydrogen?

Nuclear bombs and ablative pusher plate materials would be perhaps a little easier to come by, as would NIF-scale lasers and sail material.
VASIMIR is better than ion drives.
-You mean 'other' ion drives don't you?

"The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an electro-magnetic thruster for spacecraft propulsion. It uses radio waves to ionize and heat a propellant, and magnetic fields to accelerate the resulting plasma to generate thrust. It is one of several types of spacecraft electric propulsion systems."
TheGhostofOtto1923
3.7 / 5 (15) Oct 22, 2012
True, but Forward's analysis described a Fresnel lens to create the beam which requires a point source, not the Sun.
NIF-scale laser facilities could conceivably be created around the solar system to provide 'focus' by tracking the craft on it's journey.
The sail is comparable but could carry a negligible payload.
How much will AI weigh in a few generations?
TheGhostofOtto1923
3.8 / 5 (17) Oct 22, 2012
True, but Forward's analysis described a Fresnel lens to create the beam which requires a point source, not the Sun.
"The laser or the microwave sender would probably be a large phased array of small devices, which get their energy directly from solar radiation. The size of the array obsoletes any lens or mirror."
Fleetfoot
5 / 5 (2) Oct 22, 2012
-As opposed to a bussard ramjet?

A busard ramjet does not contain any parts that are currently unavailable.


The means to generate the magnetic scoop many km in radius is questionable, but it is only a refinement of a hydrogen-based reaction mass approach anyway. You are also right that antimatter is not a credible alternative.

Direct fusion is required either way but the best current theoretical approaches still use the hydrogen only as reaction mass, not fuel:

"'Discovery II' could deliver a manned 172 000-kilogram payload to Jupiter in 118 days (or 212 days to Saturn) using 861 metric tons of hydrogen propellant, plus 11 metric tons of Helium-3-Deuterium (D-He3) fusion fuel."

From

http://en.wikiped...n_rocket

If you aren't fusing the hydrogen collected by the scoop, you need to consider the drag it creates.
It would be interesting to see how the figures work out for a trip to the Centauri system.
Fleetfoot
not rated yet Oct 22, 2012
True, but Forward's analysis described a Fresnel lens to create the beam which requires a point source, not the Sun.
NIF-scale laser facilities could conceivably be created around the solar system to provide 'focus' by tracking the craft on it's journey.


No, each beam would spread beyond the Rayleigh Length reducing its intensity as an inverse square. To focus the whole power at the destination needs a Rayleigh Length greater than the distance to the target, and it is related to the wavelength of the light and the diameter of the aperture.

Note that you don't need it powered all the time, only for the initial acceleration and for the brief deceleration at the destination.

The sail is comparable but could carry a negligible payload.
How much will AI weigh in a few generations?


Exactly. The trick is to embed planar graphene processing elements into a lattice structure that provides the sail strength. You can't drag a life support capsule though.
Fleetfoot
not rated yet Oct 22, 2012
True, but Forward's analysis described a Fresnel lens to create the beam which requires a point source, not the Sun.
"The laser or the microwave sender would probably be a large phased array of small devices, which get their energy directly from solar radiation. The size of the array obsoletes any lens or mirror."


Ah, he's updated his views since the "Starwisp" concept you see all over the net.

Phase matching lasers to a fraction of a wavelength over many km is tricky but much easier at microwaves, and small radiators in the tens of cm range would match the solar power of ~1.4kw/m^2 at 1AU with conventional components quite well.
TheGhostofOtto1923
3.8 / 5 (16) Oct 22, 2012
No, each beam would spread beyond the Rayleigh Length reducing its intensity as an inverse square. To focus the whole power at the destination needs a Rayleigh Length greater than the distance to the target, and it is related to the wavelength of the light and the diameter of the aperture.
Perhaps the first ship could drop collector/retransmitters along the way, creating a highway of sorts.

"A radio repeater is a combination of a radio receiver and a radio transmitter that receives a weak or low-level signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation."

A long time ago I saw a paper by a princeton postdoc about the idea of sending a stream of fuel-filled pellets. They would be captured by the spacecraft, imparting momentum and providing fuel. If these pellets were antimatter they could perhaps impact a large sacrificial pusher plate and provide direct thrust.
TheGhostofOtto1923
3.8 / 5 (16) Oct 22, 2012
Lots of good ideas here
http://en.wikiped...opulsion

Jigga/Terriva should like this one

"In a black hole starship, a parabolic reflector would reflect Hawking radiation from an artificial black hole. In 2009, Louis Crane and Shawn Westmoreland of Kansas State University published a paper investigating the feasibility of this idea. Their conclusion was that it was on the edge of possibility, but that quantum gravity effects that are presently unknown may make it easier or make it impossible."

-as we could use the LHC to manufacture the black holes. Win-win.
gralp
2.5 / 5 (2) Oct 22, 2012
"There's no point in acting all surprised about it. All the planning charts and demolition orders have been on display at your local planning department in Alpha Centauri for fifty of your Earth years so you've had plenty of time to lodge any formal complaints and its far too late to start making a fuss about it now." - said Vogon's captain in the Hitchhiker's Guide to the Galaxy. By now we named the planet, maybe we'll stumble upon the charts someday.
Fleetfoot
4 / 5 (1) Oct 22, 2012
NIF-scale laser facilities could conceivably be created around the solar system to provide 'focus' by tracking the craft on it's journey.


p.s. Bear in mind that the NIF is designed as a very short pulse system to initiate ignition, what is needed for Forward's plan is lasers that can produce constant power for many hours.
Fleetfoot
not rated yet Oct 22, 2012
No, each beam would spread beyond the Rayleigh Length reducing its intensity as an inverse square. To focus the whole power at the destination needs a Rayleigh Length greater than the distance to the target, and it is related to the wavelength of the light and the diameter of the aperture.
Perhaps the first ship could drop collector/retransmitters along the way, creating a highway of sorts.

"A radio repeater is a combination of a radio receiver and a radio transmitter ..."


That isn't needed, we aren't talking about a meaningful signal, just raw power to push a light sail.

Lasers near the Sun can easily accelerate the sail to cruising speed before it leaves the Solar System, the problem is slowing the sail down at the far end. Forward's idea was to detach a small part from the main sail which would then become a sacrificial mirror. The power beamed from the Solar System would reflect back from the larger part onto the small section slowing it down. [to be continued]
Fleetfoot
not rated yet Oct 22, 2012
[contd.]

Perhaps the first ship could drop collector/retransmitters along the way, creating a highway of sorts.


Those would need to carry fuel to generate energy to beam to the sail. First, if they were carried by the sail, they would need to use fuel to decelerate or be "dropped along the way". Second, they would loose efficiency beaming the power they generate, so why not just leave them on the craft and use the power locally with no "drop" or beaming lose.

What you have now is no longer a "beamed power" solution, it is a conventional rocket used only for slowing down with a mass driver for the launch phase. The problem with rockets is that they have to carry both their energy generation fuel and reaction mass (though those are usually the same material). The beamed power and mass driver strategies seek to remove those masses from the craft.

My biggest concern is actually political, would other countries allow the building of such powerful lasers in space?
antialias_physorg
not rated yet Oct 22, 2012
I'm not sure that will work with lasers. The way I calculate it - even if you could get constant 0.1g acceleration with a laser (which seems ludicrously large) you'd need to accelerate out to 100 times Neptune orbit to reach 0.1c

And I'm not convinced one can get a laser to project power that far out.
antialias_physorg
not rated yet Oct 22, 2012
Another thing to consider: With a laser you aren't mobile. There is no way to react to anything in your path. (you'd need to 'phone back' - which can take months/years for them to adjust the beam so you can go somewhere else). But at those speeds you only have seconds (if that) to react to smallish dangers. Even one grain of sand will rip you apart. And if you think of using something heavy for shielding (like ice or somesuch) then forget about those 0.1g.
TheGhostofOtto1923
3.7 / 5 (16) Oct 22, 2012
That isn't needed, we aren't talking about a meaningful signal, just raw power to push a light sail.
Correct. I was giving an example as a present-day analog to the kind of station which could be deployed en route to capture beam energy and reissue it.
With a laser you aren't mobile.
Beam energy can be captured and stored with solar panels or the equivalent, as well as accelerating the craft directly.
you'd need to 'phone back' - which can take months/years for them to adjust the beam
Another advantage of intermediate re-emitters - they could be re-aimed much more quickly. I am sure these things have already been thought of by somebody, somewhere.
TheGhostofOtto1923
3.8 / 5 (16) Oct 22, 2012
Those would need to carry fuel to generate energy to beam to the sail.
They would be capturing the dissipated beam and taking what little energy they need to re-form and re-emit it.
First, if they were carried by the sail, they would need to use fuel to decelerate
They could use some of the beam energy for attitude adjustment and operation. I think these would still be multiple beams from multiple points in the solar system for redundancy, with lots of excess energy. Emitting the beam itself would provide counterthrust.
I am sure these things have already been thought of by somebody, somewhere.
-And maybe already thoroughly discounted it! Find it and prove me wrong.
antialias_physorg
not rated yet Oct 22, 2012
Beam energy can be captured and stored with solar panels or the equivalent, as well as accelerating the craft directly.

Makes the craft heavy.

Another advantage of intermediate re-emitters - they could be re-aimed much more quickly

At 0.1c you have 10 seconds to evade something that is the equivalent of Earth-Moon distance ahead of you (as noted elsewhere: a grain of sand of 1mm size will hit you at that speed with the energy equivalent of 7 tons of TNT. And you'll be hard pressed to detect such a small object at that distance).

You'd need reemitters every Earth-Moon distance along the way to get a 9 seconds window. Even if you'd seed the entire line with these gazillion reemitters your craft won't move much out of the way.

The math just doesn't work out on those types of craft at all.

Sonhouse
3 / 5 (2) Oct 22, 2012
I read antimatter rocket design is actually ahead of fusion rockets due to the simpler combustion principle, if we had a supply of anti matter.

The energy of 1/10th of a picogram is one watt second, give or take.

That is a lot of concentrated energy in antimatter!
Pkunk_
2.3 / 5 (3) Oct 23, 2012
@antialias_physorg said -
You'd need reemitters every Earth-Moon distance along the way to get a 9 seconds window. Even if you'd seed the entire line with these gazillion reemitters your craft won't move much out of the way.

That's sounds like something insane , a network of lenses spread out from the Earth towards the asteroid belt/Jupiter. But it's something already talked about in detail in the book - http://www.amazon...39133328
The lens program talked about in the book is possible using current-tech , but it is requires lots of tricky rocketry to pull off. And something like that can use solar energy to power an interstellar probe.
antialias_physorg
5 / 5 (1) Oct 23, 2012
I read antimatter rocket design is actually ahead of fusion rockets due to the simpler combustion principle, if we had a supply of anti matter.

Yes. And unicorn dust would be even better. We just need a supply of unicorn dust. (And something to contain it in)

That's really the problem with all technical 'ideas' on this forum. People just say "Oh, here's the grand design - let someone else figure out the details"...but as soon as you go into the details you figure out that the design idea is just a brainfart.

I've had managers like that who wanted impossible inventions and thought that just dropping the name of some buzzwords was good enough. They thought that by simply stating the issue and these buzzwords that they had then made some sort of 'valuable contribution' to solving the problem.

The reason why their engineers didn't come up with the same solution was that THEY knew beforehand that it was idiotic because THEY had thought it through before opening their mouths.
Fleetfoot
not rated yet Oct 23, 2012
I'm not sure that will work with lasers. The way I calculate it - even if you could get constant 0.1g acceleration with a laser (which seems ludicrously large) you'd need to accelerate out to 100 times Neptune orbit to reach 0.1c


That's right, to 3162AU over 1 year.

And I'm not convinced one can get a laser to project power that far out.


The limiting factor is at the other end though, Alpha Centauri is at 272,000AU.

Assume the sail is 10km in diameter and it drops the central 100m diameter 1 year before arrival. To slow that part at 0.1g needs (1/100)^2 of the illumination, which means the laser beam can be 1000km in diameter at Alpha Centauri, which is the same as 10km at 2720AU.

The main sail has to change shape to a parabolic reflector and then mirror all the beam power back onto the 100m target at up to 2720A AU as well, but it isn't a laser, it is diffraction limited.

I'll leave you to try other numbers, but I don't see it working.
Fleetfoot
5 / 5 (1) Oct 23, 2012
Those would need to carry fuel to generate energy to beam to the sail.
They would be capturing the dissipated beam and taking what little energy they need to re-form and re-emit it.


Photovoltaic cells are only about 10% efficient and the beam would be hundreds of km in diameter.

First, if they were carried by the sail, they would need to use fuel to decelerate
They could use some of the beam energy for attitude adjustment and operation.


No, absorbing the beam would accelerate them away from the Solar System unless they had on-board reaction mass.

Emitting the beam itself would provide counterthrust.


But always less than absorbing the power in the first place.
Fleetfoot
5 / 5 (1) Oct 23, 2012
Another advantage of intermediate re-emitters - they could be re-aimed much more quickly

At 0.1c you have 10 seconds to evade something that is the equivalent of Earth-Moon distance ahead of you ..


The sail would be far beyond the relay station so all it can do is target the sail. For avoidance, you need to rotate the sail so that the reflected light gives transverse thrust. For a sail 100km in diameter, that will take hours just to change the orientation never mind the time to move aside far enough.

Detecting a grain of sand at many light hours range is nonsensical, we have a hard enough time detecting Earth-orbit crossing asteroids!
Fleetfoot
not rated yet Oct 23, 2012
I read antimatter rocket design is actually ahead of fusion rockets due to the simpler combustion principle, if we had a supply of anti matter.


Place your order here:

https://livefromc...y00.html

All you have to do then is work out a method of storing it that uses less power than you get from it, oh and shielding it from cosmic rays or slowing down relativistic anti-neutrons. Good luck with that one.
antialias_physorg
5 / 5 (1) Oct 23, 2012
For a sail 100km in diameter, that will take hours just to change the orientation never mind the time to move aside far enough. Detecting a grain of sand at many light hours range is nonsensical,

Exactly. I'm just pointing out some ofthe more obvious flaws.
Some of the less obvious ones are:
- keep a sail that size light and yet rigid enough to steer (especially with an attached payload)
- building planet size laser batteries (never mind powering them. The lasers we have generate VERY short pulses VERY far apart. To get a constant acceleration you'd need to synchronize a VAST amount of them with HUGE energy requirements - Way in excess of the entire Earth's energy production )
- shielding from cosmic rays (and especially blue shifted rays once you get up to really good speeds)
- ...
Fleetfoot
5 / 5 (1) Oct 23, 2012
I'm just pointing out some of the more obvious flaws.


You had already mentioned that but others seemed to think retargetting the repeater would help and that makes it worse than you stated.

Some of the less obvious ones are:
- keep a sail that size light and yet rigid enough to steer


It can't be rigid, just use the beam to thrust different parts at different accelerations to maintain the profile.

building planet size laser batteries (never mind powering them. The lasers we have generate VERY short pulses VERY far apart.


http://en.wikiped...opulsion

The power is in the tens of terawatts continuously for a year so forget storage, continuous power is the only feasible solution. Pulsing gives no advantages, it's easier to use a continuous laser so direct solar pumping would be best or perhaps solar cells connected directly to CO2 laser tubes. Whatever the power approach, the tubes need to be km in diameter.
antialias_physorg
not rated yet Oct 23, 2012
it's easier to use a continuous laser

It would be absolutely requird to have a continuous laser. Just pointing out that the high power lasers we have are anything BUT continuous.
Then:
Lasers do heat up.
The conversion efficiency from power 'in' to laser 'out' is low. For CO2 lasers it's 'comparatively high' compared to other lasers - i.e. about 20%. The rest is heat.
This means for each terrawatt of laserpower you want to get out you have to get rid of 4 terrawatts of heat.

Space is notorious for being a very bad medium for cooling purposes.

Taking the link as a basis we'd need (for an unmanned rendezvous probe) 8-9TW of continuous laser power for 0.1g. Meaning 40-45TW of total power (for comparison: the largest powerplant in the world, the three gorges dam in china, produces 22.5GW. We'd need 2000 of those).

But the table notes that the max speed is 0.5% of light speed - so pretty much useless, anyhow, because that means more than 800 years flight time.
Fleetfoot
not rated yet Oct 23, 2012
Lasers do heat up.
The conversion efficiency from power 'in' to laser 'out' is low. For CO2 lasers it's 'comparatively high' compared to other lasers - i.e. about 20%. The rest is heat.
This means for each terrawatt of laserpower you want to get out you have to get rid of 4 terrawatts of heat.

Space is notorious for being a very bad medium for cooling purposes.

Taking the link as a basis we'd need (for an unmanned rendezvous probe) 8-9TW of continuous laser power for 0.1g. Meaning 40-45TW of total power


The system would have to be in space. Take a flat sheet of metal, cover one side with solar cells and make the other side matt black with the occasional laser tube sticking out. With no output power drawn, the plate reaches thermal equilibrium. Switch on the lasers which draws some power and the temperature will drop a bit. The bigger the plate, the more power you absorb, but the more you radiate too.

Adjust the distance from the Sun to taste ;-)
TheGhostofOtto1923
3.6 / 5 (17) Oct 23, 2012
Yes. And unicorn dust would be even better. We just need a supply of unicorn dust. (And something to contain it in)
AA discounts research papers and feasibility studies done by scientists and engineers as scifi and storytelling. Curious.

Say AA, when fusion projects are funded with the knowledge that materials to make future reactors work are not available yet, is this also storytelling, or is it researching and studying?

Scientists are doing these same things at this very moment with antimatter production, manipulation, and storage, with the idea that it will one day be used as a fuel. Did you not know this?
antialias_physorg
5 / 5 (1) Oct 23, 2012
I'm aware of the research on antimatter traps.

With full atoms they're talking about capturing individual antihydrogen atoms.

From here:
http://news.disco...523.html

- Let all the colliders in the world run for 1000 years and you could produce roughly a microgram of antimatter (providing you could also catch 100% of that and store it safely for all that time).
- A full size mission with 100 ton payload to the nearset star would require 80 supertankers worth of this stuff (lower if you are prepared to go at lower speeds. But you can still see that we're WAY deep in lala-land with this)

Yes: antimatter is great. But as with the 'laser idea' it's so far from being feasible that we need to think about a few hundred steps in between before dreaming of an 'antimatter spaceship'.

Maybe for interplanetary stuff one day...maybe.
antialias_physorg
5 / 5 (2) Oct 23, 2012
From my POV there are sensible and less senible ways of thinking about future technologies. This view is based on some observations:

1) The building of largish infrastructure (powerplants, spaceships, accelerators, etc.) takes on the order of a decade (minimum).
2) Every half century to century or so we have revolutionary new technology coming along (steam engine, lasers, fission, possibly soon fusion, ... )

So to dream up stuff that will use current tech (laser spaceprobes, antimatter ships), but will take centuries to build is not a sensible way to plan a project. Because by the time you have all this megastuff built it will already be superceded by the next 3 revolutions in technology.

(Much like it's pointless to pour a lot of resources into slow probes when the expected advance in propulsion tech will just lead to probes sent 50 years later to overtake those probes within the first 10% of their journey)
TheGhostofOtto1923
3.7 / 5 (18) Oct 23, 2012
Let all the colliders in the world run for 1000 years and you could produce roughly a microgram of antimatter (providing you could also catch 100% of that and store it safely for all that time).
But in 1000 yrs 'we' will be routinely creating megatons of the stuff.

It's funny, you do seem to have confidence in some tech progress
when the expected advance in propulsion tech will just lead to probes sent 50 years later to overtake those probes...Because by the time you have all this megastuff built it will already be superceded by the next 3 revolutions in technology.
-But you seem to want to apply this optimism selectively. Why?
So to dream up stuff that will use current tech (laser spaceprobes, antimatter ships), but will take centuries to build is not a sensible way to plan a project.
It is the ONLY way to chart a course of research. One must imagine what things might be possible given what is currently known, and then look for ways to make it so.
antialias_physorg
5 / 5 (4) Oct 23, 2012
But in 1000 yrs 'we' will be routinely creating megatons of the stuff.

No doubt. But in 1000 years time we'll have had a few other, very fundamental breakthroughs.
One must imagine what things might be possible given what is currently known, and then look for ways to make it so.

Given the timeframes involved we could argue about getting to alpha centauri using steam power and then 'make it so'. It's just not sensible.

That's why I said. one has to keep things in perspective (and you may have noticed that Fleetfoot and I have tried to throw a bit of math at these problems to get first approximations). There is a spectrum from science fact, to science maybe, to science fantasy and science fiction. And the stuff discussed so far is just science fiction (or at best science fantasy) - but not something where serious science can be applied.

Ignoring physics gets you nowhere in science.
TheGhostofOtto1923
3.6 / 5 (17) Oct 23, 2012
- A full size mission with 100 ton payload to the nearset star would require 80 supertankers worth of this stuff (lower if you are prepared to go at lower speeds
-or if you can pelletize it and stream it to the craft, an idea which has been around for decades as I pointed out earlier. But it seems that you continue to ignore the studies I posted which have been done by competent people with grant money and supercomputers, who are guessing with a little more credibility than yourself.
The reason why their engineers didn't come up with the same solution was that THEY knew beforehand that it was idiotic because THEY had thought it through before opening their mouths.
You seem bitter. Perhaps this can explain in part your selective insight -?
22.5GW. We'd need 2000 of those).
And how much energy could be produced with a dozen 1000sqm solar farms inside the orbit of mercury? And no, it's NOT scifi.
antialias_physorg
5 / 5 (3) Oct 23, 2012
And how much energy could be produced with a dozen 1000sqm

That's just one of these unrealistic things you keep putting up.

Yeah: Dyson speheres could get a alot of power. Yeah, planet size death stars would be neat. But you have to keep this stuff at least somewhat grounded in reality.

We're nowhere near doing something as constructing a 1 square mile powerplant in space. Much less a 1000 square mile one, much less a dozen of them. Much less around Mars.
That's just unicorn dust.

Look at the stuff we're putting into orbit currently. Maybe We'll double our orbit delivery facility every decade (maybe). But your 'idea' is so many orders of magnitude beyond anything we're capable of that it's just lala land.

We should focus on stuff we CAN do and (and stuff we BARELY cannot). That's how science works. Slow and steady. It may not be exciting enough for those who know nothing of science - but its the way stuff actually produces results.

mdunka
not rated yet Oct 23, 2012
I'm glad Europeans discovered this on the southern skies.
I'm waiting for southerners' discoveries on the nourthen skies!
:D
TheGhostofOtto1923
3.8 / 5 (16) Oct 23, 2012
Dyson speheres could get a alot of power
But dyson swarms are more feasible.
planet size death stars would be neat.
Aw that's just silly.
But you have to keep this stuff at least somewhat grounded in reality.
But you're the one who wants to invoke 'fundamental discoveries' of I suppose unknown physics. Right NOW we know that antimatter will give us the most bang for the buck. And we see that science is studying how to make it, AND how to contain it in tokamak bottles.
We're nowhere near doing something as constructing a 1 square mile powerplant in space.
Technology is developing geometrically. When spaceborne robotic mining, manufacturing, and construction mature, we will see how easy and fast megastructures can be built.

Picture one of today's megafarms, tended by fully autonomous machines. And then picture this same sort of activity occurring in space, with machines assembling structures instead of planting sorghum. Sewing square miles of solar energy reapers.
TheGhostofOtto1923
3.8 / 5 (17) Oct 23, 2012
We're nowhere near doing something as constructing a 1 square mile powerplant in space.
YES WE ARE.

"2007: In May 2007 a workshop is held at the US Massachusetts Institute of Technology (MIT) to review the current state of the SBSP market and technology
2009: Several companies announce future SBSP partnerships and commitments, including Pacific Gas and Electric (PG&E) & Solaren, Mitsubishi Electric Corp. & IHI Corporation, Space Energy, Inc., and Japan Aerospace Exploration Agency.
2010: Europe's EADS Astrium announces SBSP plans.
We should focus on stuff we CAN do and (and stuff we BARELY cannot). That's how science works. Slow and steady.
Depends. Tech for instance can progress with breathtaking speed. Consider air travel from 1900 to 1965. Consider the auto and related highway systems from 1900 to 1965.

The science of antimatter, solar power, space travel, and robotics is well-understood. It is only a matter of developing the tech to apply it.
Fleetfoot
5 / 5 (2) Oct 23, 2012
Technology is developing geometrically.


Moore's Law held for many years but scaling gains have come to an end, every technology has a physical limit.

The problem for antimatter is not manufacture but storage and shielding. The only method we have for containment at the moment is laser traps that can hold a tiny number of atoms and that won't scale up. A much bigger problem though is isolating the antimatter. Even a single atom emitted from the wall of a containment vessel (there's always some outgassing) will cause a cascade of explosions.

The question isn't whether these problems can be overcome eventually but whether such schemes can reach the nearest stars before more conventional techniques. If a passive solar sail can get to Alpha Centauri in 300 years, that sets the limit on more exotic approaches.

Bear in mind also that political and security concerns will almost certainly outweigh the scientific challenges in this case.
TheGhostofOtto1923
3.8 / 5 (17) Oct 23, 2012
The problem for antimatter is not manufacture but storage and shielding. The only method we have for containment at the moment is laser traps that can hold a tiny number of atoms and that won't scale up.
BUT we are spending billions on donut-shaped plasma bottles for energy production which JUST HAPPEN to be directly applicable to confinement of all sorts if plasma, including antimatter. How providential.
Bear in mind also that political and security concerns will almost certainly outweigh the scientific challenges in this case.
These issues plus shielding and safety are best managed in space. Large amounts of antimatter, produced in automated factories using energy beamed from asteroid energy farms in tight solar orbits, will pose little danger to planetary inhabitants.

AA doesn't like scifi but let me reference '2312' by Kim Stanley Robinson. As scifi it is harder than most; more reasonable extrapolation than unicorn farts.
TheGhostofOtto1923
3.8 / 5 (16) Oct 23, 2012
Moore's Law held for many years but scaling gains have come to an end, every technology has a physical limit.
-Perhaps for individual strains, but technology as a whole is carrying us unerringly toward the Singularity.
http://en.wikiped...gularity

I suppose there will be a big party or something.

And u see I misspoke:

"Futurist Ray Kurzweil postulates a law of accelerating returns in which the speed of technological change (and more generally, all evolutionary processes[17]) increases exponentially, generalizing Moore's Law in the same manner as Moravec's proposal, and also including material technology (especially as applied to nanotechnology), medical technology and others."
TheGhostofOtto1923
3.8 / 5 (16) Oct 23, 2012
Here's something

"MagBeam propulsion...instead of the fuel and propulsion system being part of the payload craft, they are instead located on a platform held in orbit...uses a helicon plasma source to produce a plasma beam...The ionized gas is accelerated by a magnetic field to produce thrust. The helicon drive produces a tight beam of ions as the magnetic field that accelerates them continuously expands with the plasma beam keeping them focused. This ion beam is used to push a payload which is equipped with a small amount of gas for propellant such as argon or xenon, a power source and a set of electromagnets to produce a mini-magnetosphere magnetic sail. The gas propellant is ejected into the plasma beam being directed at the craft which heats and ionizes it."

-Imagine if this ion beam was antimatter, and reacted with the propellant behind a suitable pusher plate or within a reaction chamber.
TheGhostofOtto1923
3.8 / 5 (16) Oct 23, 2012
And before AA hiccups, this is also not scifi

"MagBeam is the name given to an ion propulsion system for space travel initially proposed by Professor Robert Winglee of the Earth and Space Sciences Department at the University of Washington for the October 2004 meeting of the NIAC."
Fleetfoot
5 / 5 (1) Oct 24, 2012
The problem for antimatter is not manufacture but storage and shielding. The only method we have for containment at the moment is laser traps that can hold a tiny number of atoms and that won't scale up.
BUT we are spending billions on donut-shaped plasma bottles for energy production which JUST HAPPEN to be directly applicable to confinement of all sorts if plasma, including antimatter. How providential.


No, they are only useful for normal matter, there will be a small leakage from the plasma to the containment walls which is fatal with antimatter.

However, that's only an engineering problem. Calculate the energy that could be stored as antimatter in such a torus and apply that to the mass of the containment system and its power supply to find out the best speed it could attain. I'll give you a clue, it's not as fast as a passive solar sail ;-)
Fleetfoot
5 / 5 (1) Oct 24, 2012
Moore's Law held for many years but scaling gains have come to an end, every technology has a physical limit.
-Perhaps for individual strains, but technology as a whole is carrying us unerringly toward the Singularity.


Perhaps, but that's another topic. For interstellar travel, each "strain" will have a best possible speed and hence an optimum launch time. When one technology reaches that point, unless another is already capable of going faster, we should launch. If another technology becomes available some years later, it can always be applied to the next generation of ships launched from the first set of stars we reach using the initial technology. After all, we won't stop at Alpha Centauri.
antialias_physorg
5 / 5 (1) Oct 24, 2012
ech for instance can progress with breathtaking speed.

Yes. because I the past century or so we've had an explosion of people that have worked in those fields (and of investment into those fields). That has levelled off (and in some cases already decreased).

Then there are things that just don't scale - e.g. the build time of a large powerplant. For a technology to permeate/change society it must be deployed. The deployment time of powerplants is still about a decade - and the needed amortisation time is still several decades. So no amount of speedup in tech will bring about faster changeovers in energy technology.

And we see that science is studying how to make it, AND how to contain it in tokamak bottles.

Yes. But the original question was: "How long to get to there with a VASIMIR rocket" - and the point being made here is: That's not the tech that's going to get us there.
antialias_physorg
5 / 5 (1) Oct 24, 2012
or if you can pelletize it and stream it to the craft

And you accelerate the pellets (in their - not overly simple - containers) to 0.1c or more to catch up with your ever accelerating craft exactly ... how?

BUT we are spending billions on donut-shaped plasma bottles for energy production which JUST HAPPEN to be directly applicable to confinement of all sorts if plasma, including antimatter

The containment is rather energy intensive. The amount of material in a tokamak is rather small at any one time. If you continually leach some small amount of antimatter out to keep the containment up this won't last you the hundreds of years this thing needs to fly. (I'm not even talking about using part of the antimatter to power any sort of drive)
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
However, that's only an engineering problem.
Correct.
Calculate the energy that could be stored as antimatter in such a torus
You mean now or in the future?
and apply that to the mass of the containment system and its power supply to find out the best speed it could attain. I'll give you a clue, it's not as fast as a passive solar sail ;-)
The tokamak configuration is the best way currently known for storing plasma in bulk. They are learning how to increase density, confinement time, and plasma integrity. They are learning how to minimize contaminents and contact with the walls. How good will they get at doing this?
That has levelled off (and in some cases already decreased).
Again AA does not bother to follow links and read what experts have to say, opting for selective pessimism.
Fleetfoot
not rated yet Oct 24, 2012
However, that's only an engineering problem.
Correct.
Calculate the energy that could be stored as antimatter in such a torus
You mean now or in the future?


I mean the theoretical maximum, as we have been doing for other possibilities.

The tokamak configuration is the best way currently known for storing plasma in bulk.


Sure, but has anyone ever tried to store pure antimatter that way?

They are learning how to increase density, confinement time, and plasma integrity. They are learning how to minimize contaminents and contact with the walls. How good will they get at doing this?


Can they achieve a rate less than one ion per century? A single anti-proton hitting the wall will eject neutrons back into the plasma. Neutrons aren't afected by EM fields so are unstoppable and a single neutron hitting the antimatter plasma will eject a shower of extra particles, you get a cascade failure. Find a way to control neutrons and you might succeed.
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
And you accelerate the pellets (in their - not overly simple - containers) to 0.1c or more to catch up with your ever accelerating craft exactly ... how?
Again this is not my idea. It was proposed by a physicist who could answer these questions for you. But I would assume nanoscale pellets of antimatter could be initially accelerated to relativistic velocities, perhaps as a frozen or glassy or metallic substance (charged? magnetized?) Perhaps they would impact an ablative plate of normal matter, providing thrust, until the craft reaches comparable velocities and can capture them. Somehow.
small amount of antimatter out to keep the containment up this won't last you the hundreds of years this thing needs to fly.
But again, the toroid bottle is currently the best known way of storing and transporting plasma in bulk, and I think that this is the primary reason many countries around the world are pouring billions into the tech. How powerful can containment fields get?
TheGhostofOtto1923
3.6 / 5 (17) Oct 24, 2012
Sure, but has anyone ever tried to store pure antimatter that way?
Not yet. I think it's curious that ITER (and successive machines?) is being built within a few hundred miles of, and directly south of, the LHC. Probably just a coincidence. Daunting to build an evacuated tunnel connecting the 2 (currently.)
Neutrons aren't afected by EM fields so are unstoppable and a single neutron hitting the antimatter plasma will eject a shower of extra particles, you get a cascade failure.
No other way of learning how to solve these problems than by trying is there? Perhaps aneutronic reactions will be discovered.
antialias_physorg
not rated yet Oct 24, 2012
of antimatter could be initially accelerated to relativistic velocities, perhaps as a frozen or glassy or metallic substance

Again: How? What force is used to instantly push a pellet to 0.1c or beyond? (Including a shielding container - because otherwise any stray proton will just explode your pellet along the way. space is not THAT empty)
If you have that licked then you don't need antimatter at all. becaue then you can just scale that launching mechanism up and put a ship in it.

But again, the toroid bottle is currently the best known way of storing and transporting plasma in bulk

Yes. But 'bulk' is really very relative here. Something the size of ITER stores 0.5 grams of plasma. A site linked earlier in this thread calculated for an 100 ton craft you need several supertankers worth of antimatter.

You do the math.
antialias_physorg
not rated yet Oct 24, 2012
How powerful can containment fields get?

Good question. The thing is
a) you want large storage volume
b) you want strong containment

How much you can contain is dependent on the amount of current you pump through your superconducting coils. And that current is limited
(I don't know, but I'd just assume that the stuff put into CERN or ITER is designed to be just barely above what is needed there. I.e. that the sizes/masses deployed there are not vastly overdesigned or could be made to store vastly more)

Larger currents require larger superconductor cable diameters. (which means that the field producing element is further away from the chamber as cable diameters increase). So there will be some maximum size-to-storage-capacity ratio which cannot be undercut (except by some technology we currently know nothing of)
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
Again: How? What force is used to instantly push a pellet to 0.1c or beyond?
I dont know. How long would a railgun or helicon drive have to be? Assuming future tech capable of generating containment fields capable of storing pounds of antimatter indefinitely?

"In railgun physics, the magnitude of the force vector can be determined from a form of the Biot–Savart law and a result of the Lorentz force. It can be derived mathematically in terms of the permeability constant (), the radius of the rails (which are assumed to be circular in cross section) (), the distance between the centrepoints of the rails () and the current in amps through the system ()..."

-You will have to do the math as I am mathematically ignorant.
(except by some technology we currently know nothing of)
I thought you preferred these?
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
(I don't know, but I'd just assume that the stuff put into CERN or ITER is designed to be just barely above what is needed there
They are both trying to maximize density to optimize collisions and reactions. But also to learn how to minimize disruptions and instabilities, and to increase plasma integrity.
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
A site linked earlier in this thread calculated for an 100 ton craft you need several supertankers worth of antimatter.
I thought that was a guesstimate? At any rate, technology marches on, exponentially:

"To accelerate to a speed equal to that of the engine's exhaust velocity (0.33 c) and then decelerate to a stop at your destination, 86 percent of the initial mass of the spacecraft would have to be fuel - half of that antimatter...Most encouraging is that the effective exhaust velocity of the new nozzle design is about 69 percent of the speed of light. This means that a beamed core antimatter spacecraft with the new nozzle could make a one-way trip at a speed of about two-thirds of the speed of light carrying seven times the payload that could be hauled using the old nozzle."
TheGhostofOtto1923
3.7 / 5 (16) Oct 24, 2012
any stray proton will just explode your pellet along the way. space is not THAT empty)
So? A certain percentage could be lost without affecting the whole system.
If you have that licked then you don't need antimatter at all. becaue then you can just scale that launching mechanism up and put a ship in it.
Pellets could withstand extreme acceleration that a ship could not. Obviously.
antialias_physorg
not rated yet Oct 24, 2012
How long would a railgun or helicon drive have to be?

Depends on what type of g forces one would deem possible.
A ring containment structure certainly isn't up for much acceleration before the stuff inside leaks out.
As calculated earlier: at 0.1g you'd need a structure in length 100 times the distance Sun-Neptune.

You will have to do the math as I am mathematically ignorant.

You don't say.

Adjust the distance from the Sun to taste

Ah. You mean: adjust the cost to taste.
I like megastructures in science fiction. But I'm not certain it's sensible to discuss them as 'to do' projects for humanity just quite yet.

In the timeframe it would take to put up one of those (thechnologicaly AND economically) we'll have so many technologial revolutions that considering them right now is pointless.
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
Depends on what type of g forces one would deem possible.
Assuming current tech.
A ring containment structure certainly isn't up for much acceleration before the stuff inside leaks out.
Assuming current tech. Such a ring around Ceres would be more efficient. Such a ring could be constructed robotically and powered by energy beamed from solar stations on asteroids within the orbit of mercury.

Scale progression of such capability is comparable to the Hunley vs the current fleets of nuclear-powered subs; or the pony express vs the current UPS and Fedex networks.
As calculated earlier: at 0.1g you'd need a structure in length 100 times the distance Sun-Neptune.
Assuming current tech.
You don't say.
Duh. But even better, I know how to look for info generated by experts instead of assuming I know how to generate it myself. Lurker does that all the time with consistsntly embarrassing results, doesn't he?
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
I like megastructures in science fiction. But I'm not certain it's sensible to discuss them as 'to do' projects for humanity just quite yet.
But they ARE being discussed as 'to do' projects. Alliances are being formed and funding is being secured at this moment. What is the difference between the 1000s of megastructure oil platforms or powerplants around the world, and those we might construct in space? Robotics and AI will make this happen, and we already have these. The revolutions have already happened.
In the timeframe it would take to put up one of those (thechnologicaly AND economically) we'll have so many technologial revolutions that considering them right now is pointless.
I suppose that, if the captain of the hunley could have even envisioned a nuclear-powered and armed sub, he would have said the same thing. But we CAN envision them, and we must certainly try, as we need to chart our future and channel our efforts to get there as safely and as quickly as possible.
Fleetfoot
5 / 5 (1) Oct 24, 2012
I would assume nanoscale pellets of antimatter could be initially accelerated to relativistic velocities, perhaps as a frozen or glassy or metallic substance (charged? magnetized?)


There is no way to slow anti-neutrons (because they are neutral) so the only antimatter that can be created is pure anti-hydrogen. You have to keep it below 14K to keep it solid.

The solar wind has several protons per cc and even the ISM is around that density so you also have to have a powered, cryogenic container to protect your pellets or they won't travel more than a few metres before exploding. You would also need very low acceleration since you cannot grasp the pellet.

Beamed propulsion and a solar sail perhaps ;-)

But again, the toroid bottle is currently the best known way of storiillions into the tech. How powerful can containment fields get?


Not much more than current technology, superconducting behaviour is stopped by magnetic fields, they already run at that limit.
Fleetfoot
not rated yet Oct 24, 2012
any stray proton will just explode your pellet along the way. space is not THAT empty)
So? A certain percentage could be lost without affecting the whole system.


Using unprotected pellets 1mm in diameter, 90% would explode before travelling 1m in free space. Don't stand too close to the launcher!

Pellets could withstand extreme acceleration that a ship could not. Obviously.


Really? How do you propose to accelerate a pellet of solid hydrogen inside a shielding system without touching it or warming it up?

How much do you think would sublime even at say 1K, what is its vapour pressure?

You need to do some serious thinking to turn this idea into credible solution, even using hand-waving future technology.
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
Using unprotected pellets 1mm in diameter, 90% would explode before travelling 1m in free space.
Heres an alternative for pelletization which could withstand extreme acceleration:

"Another, more hypothetical method is the storage of antiprotons inside fullerenes. The negatively charged antiprotons would repel the electron cloud around the sphere of carbon, so they could not get near enough to the normal protons to annihilate with them."

-And more cause for optimism:

"Even if it were possible to convert energy directly into particle/antiparticle pairs without any loss, a large-scale power plant generating 2000 MWe would take 25 hours to produce just one gram of antimatter. Given the average price of electric power around $50 per megawatt hour, this puts a lower limit on the cost of antimatter at $2.5 million per gram... They suggest that this would make antimatter very cost-effective as a rocket fuel"
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
But there are even better uses for antimatter in propulsion:

"Antimatter catalyzed nuclear pulse propulsion is a variation of nuclear pulse propulsion based upon the injection of antimatter into a mass of nuclear fuel which normally would not be useful in propulsion."

"...the concept appears to be feasible using technology and infrastructure likely to be made available during the second half of the 21st century"

"Work has been performed at Lawrence Livermore National Laboratory on antiproton-initiated fusion as early as 2004. In contrast to the large mass, complexity and recirculating power of conventional drivers for inertial confinement fusion (ICF), antiproton annihilation offers a specific energy of 90 MJ per µg and thus a unique form of energy packaging and delivery."
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
Antimatter production in space:

"Robert Forward...proposed that one day we would build antimatter factories in space. Build a large enough solar-powered array and you could, he thought, come up with something on the order of a gram of antimatter per day."

Or harvest it:

"Bickford went on to suggest that we could collect some 25 nanograms per day using his magnetic scoop, a process that if successful would prove orders of magnitude more cost effective than creating antimatter here on Earth...Theoretical studies suggest that the magnetosphere of much larger planets like Jupiter would be even better for this purpose."

-And convert it for different purposes:

"If you were to start with anti-deuterium and anti-tritium, you might imagine a Tokamak style reactor with an anti-plasma to create anti-helium."

-Tokamaks do not have to contain 'hot' plasma, although maximizing temperature is a good way of producing data. Cold plasmas may be easier to contain, densify, and manipulate.
TheGhostofOtto1923
3.8 / 5 (16) Oct 24, 2012
You need to do some serious thinking to turn this idea into credible solution, even using hand-waving future technology.
Oh not me. I just have to look around for experts who are doing just that at this very moment, as the stuff I posted above indicate.

Heres one guy who has put a little more thought into the same concept:
http://jamesmessi...ce-craf/

-Or a variation of antimatter-catalyzed fission using pellet streams of fission fuel:
http://ffden-2.ph...ion.html
Fleetfoot
not rated yet Oct 24, 2012
Using unprotected pellets 1mm in diameter, 90% would explode before travelling 1m in free space.
Heres an alternative for pelletization which could withstand extreme acceleration:

"Another, more hypothetical method is the storage of antiprotons inside fullerenes. The negatively charged antiprotons would repel the electron cloud around the sphere of carbon, so they could not get near enough to the normal protons to annihilate with them."


The idea sounds flawed as the sphere could act as a Faraday cage with no net effct but even if it worked classically, the uncertainty principle means the anti-proton would anihilate eventually by tunneling. That sounds like more amateur handwaving.
Fleetfoot
not rated yet Oct 24, 2012
But there are even better uses for antimatter in propulsion:

..

"Work has been performed at Lawrence Livermore National Laboratory on antiproton-initiated fusion as early as 2004."


Using antimatter instead of a spark plug is a nice idea and the antimatter would be manufactured on the ship and used immediately, but that isn't antimatter propulsion. The calculations would be those for a fusion drive.
Fleetfoot
not rated yet Oct 24, 2012
Antimatter production in space:

"Robert Forward...proposed that one day we would build antimatter factories in space. Build a large enough solar-powered array and you could, he thought, come up with something on the order of a gram of antimatter per day."


"He thought .." being the key phrase. Just a pipedream again.

Anyway, as we have said before, the biggest problems are not concerned with production but storage and shielding.

"If you were to start with anti-deuterium and anti-tritium, you might imagine a Tokamak style reactor with an anti-plasma to create anti-helium."


Again, that falls foul of the fact that you cannot moderate anti-neutrons.
Fleetfoot
not rated yet Oct 24, 2012
I just have to look around for experts who are doing just that at this very moment, as the stuff I posted above indicate.

Heres one guy who has put a little more thought into the same concept:
http://jamesmessi...ce-craf/


You have to be kidding me:

"Quarkonium matter-antimatter explosive based pellets might also be incorporated into fuel pellet runway streams."

You don't imagine that is serious do you?

http://ffden-2.ph...ion.html

That page is at least a little closer to reality:

"[The design] may be adopted by NASA for a manned mission to Mars (since, by then, the antimatter storage problems may have been overcome)."

At least he is aware of the problem but again it is nothing more than handwaving.
TheGhostofOtto1923
3.5 / 5 (17) Oct 25, 2012
"If you were to start with anti-deuterium and anti-tritium, you might imagine a Tokamak style reactor with an anti-plasma to create anti-helium."


Again, that falls foul of the fact that you cannot moderate anti-neutrons.
Well, it us an example of someone considering that tokamaks could be used for purposes besides producing energy ie manufacturing and storage, which is mainly why I posted it.

The toroid bottle is currently the most effective way we know of containing plasma. And as materials in plasma form, including antimatter, are going to be very important to future tech, I believe this is the reason we are building machines all over.
You don't imagine that is serious do you?
The gentleman may be a little errant on that particular suggestion. Pelletized fuel streams are feasible according to many, and varying launch velocity to accomodate accelerating craft speed is an interesting idea.
TheGhostofOtto1923
3.6 / 5 (17) Oct 25, 2012
At least he is aware of the problem but again it is nothing more than handwaving.


"hand waving
n.
Usually insubstantial words or actions intended to convince or impress: resorted to hand waving instead of arguing rationally."

-Perhaps you meant solid research by experts at major facilities instead?

"Work has been performed at Lawrence Livermore National Laboratory on antiproton-initiated fusion as early as 2004"

"The ACMF concept is being developed at Penn State University and is based on their findings that antimatter can induce a more efficient fission reaction than normal fission methods."

"The AIM engine requires just 5x108 antiprotons per reaction; this amount can be readily obtained from Fermilab and CERN."
http://www.engr.p...on2.html
Fleetfoot
not rated yet Oct 25, 2012
Well, it us an example of someone considering that tokamaks could be used for purposes besides producing energy ie manufacturing and storage, which is mainly why I posted it.

People consider lots of ideas but making them work is another matter. Vague ideas which don't even acknowledge the key problems do not indicate an "expert" opinion.

The toroid bottle is currently the most effective way we know of containing plasma. And as materials in plasma form, including antimatter, are going to be very important to future tech ..


Both true but unrelated. Magnetic bottles can store anti-protons or positrons but they don't work well for neutral anti-hydrogen atoms and are usless for anti-neutrons.

Pelletized fuel streams are feasible according to many,


Not if it is antimatter as my simple calculation showed. As I type this the solar wind is 3.4 proton/cc, do the sum yourself:

http://www.spaceweather.com/

How do you propose to accelerate pellets of solid anti-hydrogen?
Fleetfoot
5 / 5 (1) Oct 25, 2012
At least he is aware of the problem but again it is nothing more than handwaving.


"hand waving
n.
Usually insubstantial words or actions intended to convince or impress: resorted to hand waving instead of arguing rationally."


His exact words were "by then, the antimatter storage problems may have been overcome.". I see only an insubstantial expression of hope, there is no rational argument or even a hint regarding how the problems could be overcome at all so my use of the term seems entirely appropriate.

-Perhaps you meant solid research by experts at major facilities instead?

"Work has been performed at Lawrence Livermore National Laboratory on antiproton-initiated fusion as early as 2004"


No, none of the rest of your post relates to storage of antimatter or use as a direct fuel, only as an ignitor for a fusion process. You haven't posted any research by anyone regarding the topic at hand, expert or otherwise!
TheGhostofOtto1923
3.6 / 5 (17) Oct 25, 2012
Magnetic bottles can store anti-protons or positrons but they don't work well for neutral anti-hydrogen atoms and are usless for anti-neutrons.
Neutral beams are currently used to heat plasma in tokamaks. Such a system may function to mass-produce antimatter atoms.

You don't seem to WANT to speculate FF. Why is that? Jules Verne and Asimov were great speculators and their ideas generated real science.

Further, you seem to have a tendency to regard ideas you're not familiar with, like ACMF, as frivolity, rather than investigating. Why is that?

Further, when you do investigate, you tend to dismiss an entire mass of info on the first questionable idea you encounter. Why is THAT?
How do you propose to accelerate pellets of solid anti-hydrogen?
Mechanically? Again, neutral beams and neutron generators produce accelerated beams.
regarding the topic at hand
There are many topics at hand. Hybrid engines are a reasonable way of using antimatter for propulsion. Yes?
TheGhostofOtto1923
3.6 / 5 (17) Oct 25, 2012
His exact words were "by then, the antimatter storage problems may have been overcome.". I see only an insubstantial expression of hope, there is no rational argument or even a hint regarding how the problems could be overcome
He doesn't have to. Tokamaks and stellerators were being built long before anyone had any idea how to capture fast neutrons. But they were built on the confidence that conditions such as this could be met. This is uniformly how big science and defense projects spanning many decades and generations, are addressed.

ITER faces a substantial problem - electron discharge. It will prevent the machine from reliably operating. But the people who are building it are CONFIDENT that they can solve it by the time it is finished.

Many people with similar qualifications have similar confidence that antimatter can be used for propulsion. A direct outcome of that optimism is ACMF.
Fleetfoot
not rated yet Oct 26, 2012
Magnetic bottles can store anti-protons or positrons but they don't work well for neutral anti-hydrogen atoms and are usless for anti-neutrons.
Neutral beams are currently used to heat plasma in tokamaks.


The neutral beam is immediately ionised. You cannot confine neutral particles, they would not be affected by the magnetic field.

http://en.wikiped...njection

Such a system may function to mass-produce antimatter atoms.


We already have factories producing antimatter as has been said several times, that is not the problem.

How do you propose to accelerate pellets of solid anti-hydrogen?
Mechanically?


No, you cannot grasp antimatter with normal matter.

Again, neutral beams and neutron generators produce accelerated beams.


Anti-neutrons are produced in fast beams and retain that momentum, the problem is slowing them down. E.g. you cannot use a graphite moderator such as is used in fission reactors.
Fleetfoot
not rated yet Oct 26, 2012
You don't seem to WANT to speculate FF. Why is that? Jules Verne and Asimov were great speculators and their ideas generated real science.

Further, you seem to have a tendency to regard ideas you're not familiar with, like ACMF, as frivolity, rather than investigating. Why is that?

Further, when you do investigate, you tend to dismiss an entire mass of info on the first questionable idea you encounter. Why is THAT.


I am not dismissing the ideas, my questions are not rhetorical.

The quickest way to find the best overall solution is find how fast each is and then compare them but it's too much work for one person.

I have investigated the solar sail approach, written web pages and written simulations to back up the figures I quote.

I am challenging you to champion your preferred approach(es) the same way, with real science instead of hand-waving, and also giving you a head start on the most significant problems you need to address if you choose anti-matter propulsion.
Fleetfoot
not rated yet Oct 26, 2012
His exact words were "by then, the antimatter storage problems may have been overcome.". I see only an insubstantial expression of hope, there is no rational argument or even a hint regarding how the problems could be overcome
He doesn't have to. Tokamaks and stellerators were being built long before anyone had any idea how to capture fast neutrons. But they were built on the confidence that conditions such as this could be met.


Slowing normal neutrons is easily done, use a block of graphite for example:

http://en.wikiped...oderator

You cannot do that to anti-neutrons without first making anti-carbon. Many years ago I discussed this with one of the researchers at ATHENA:

http://public.web...-en.html

Did you know it produced equal numbers of anti-neutrons and anti-protons? The anti-neutrons could not be handled and just had to be created in a beam aimed at a block where they were anihiliated.

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