Anti-matter starships.

[AcesHigh]

To produce the antimatter requires much more energy than it releases upon annihilation with normal matter. This is because of inneficiencies that occurs in the accelerators.

yes. What about POSITRONS? Can they be used? They are much easier to produce, using only lasers.

And to produce antimatter in molar quantities (grams) would require billions upon billions fold increases in current Accelerator capacity.

specialists say that anti-matter production could be increased by some orders of magnitude if anti-matter production WAS THE OBJECTIVE (and not a byproduct) of a facility.

Antimater as a trigger for fusion and/ or fusion may be less imtimidating but I suspect World accelerator capacity would still need to be increased many million fold.

those links I posted, like from Penn State, say the current production would be enough.

Consider an ITER like Tokamak. It might contain 10^20 particles per cubic meter for 1000 seconds.

but then, it´s a plasma at billions of degrees, meaning the particles are very energetic and much more difficult to hold.

can´t you hold lots of particles somewhere WITHOUT heating them and thus making them more difficult to hold? I mean, with mechanical means, we can hold large pressures inside canisters and the gas won´t heat to billions of degrees because of it.

I mean... is a Polywell or an ITER the model of Penning Trap we want to consider?? Those Penning Traps are DESIGNED to make the particles get as hot as the sun nucleus!

Obviously, when very hot, they are difficult to contain, which was the first difficulty to trap anti-matter. Since it´s created in very energetic collisions, you could not hold it for more than a microsecond before they would leak.

Therefore first thing needed to trap anti-matter for more time was to COOL it down to much lower energy levels... after that, 1000 seconds was "easy" and probably more would be possible.

Now you are telling me that any attempt to magnetically trap particles in larger quantities will make them HOT?


Can´t a Penning Trap be designed to trap particles almost like if it was a mechanical trap, in which there is great particle density contained without it getting hotter and hotter?

[hanelyp]

Even positrons have very poor production efficiency, and the question of how you store enough to be useful. Once you account for the mass of the bottle containing your antimatter store realistic fusion fuels may have much greater available energy content.

[GIThruster]

You can trap anti-matter with a good enough magnetic trap just like you can do with normal matter.

The trouble is not just the low volumetric density of Penning traps, which are limited by the particles bumping into one another, but also realize the trap only holds the fuel. Fission, fusion and anti-matter rockets and any combination of these, all still need to carry a rocket engine, and propellant. All you're doing is moving energy from a source other than the propellant itself as with chemical, to a higher energy density physical reaction. So you can get higher Isp's but these are still limited by materials science to about 5,000. When you read that Bussard said a poly-rocket could generate higher Isp's like 11,000, you need to realize he didn't wrestle with the limits of Inconel, etc.

Chemical rockets Isp's are limited primarily by the energy from the reaction to a few hundred. Fission, fusion and anti-matter rockets are limited by the materials used in the thrust chamber and bell to a few thousand. If you see Isp numbers like 11,000, you're looking at hand waving. And again remember, you're still looking at carrying your propellant so you're still looking at the rocket equation, which is not conducive to economical transport. This is stuff for sending small, select teams of astronauts out so the rest of us can live vicariously, not creating a golden age of human spaceflight.

[Skipjack]

You can trap anti-matter with a good enough magnetic trap just like you can do with normal matter.

The trouble is not just the low volumetric density of Penning traps, which are limited by the particles bumping into one another, but also realize the trap only holds the fuel. Fission, fusion and anti-matter rockets and any combination of these, all still need to carry a rocket engine, and propellant. All you're doing is moving energy from a source other than the propellant itself as with chemical, to a higher energy density physical reaction. So you can get higher Isp's but these are still limited by materials science to about 5,000. When you read that Bussard said a poly-rocket could generate higher Isp's like 11,000, you need to realize he didn't wrestle with the limits of Inconel, etc.

Chemical rockets Isp's are limited primarily by the energy from the reaction to a few hundred. Fission, fusion and anti-matter rockets are limited by the materials used in the thrust chamber and bell to a few thousand. If you see Isp numbers like 11,000, you're looking at hand waving. And again remember, you're still looking at carrying your propellant so you're still looking at the rocket equation, which is not conducive to economical transport. This is stuff for sending small, select teams of astronauts out so the rest of us can live vicariously, not creating a golden age of human spaceflight.

You can mitigate some of the material science issues of some of these engine types with magnetic nozzles or regenerative cooling.

[GIThruster]

really, it surprises me that americans are better able to hide their airplanes, which are also less prone to crash, than these alien flying saucers who travelled several light years just to crash on Earth, or be hit by puny chemical propellant missiles...

What makes you think whomever is flying this stuff is not good at hiding it? With no idea of just how much stuff is up there, there's no way to say what percent has been hidden. And the possible reasons for any crash are many. I for one think the argument that these things are susceptible to lightning is a fair possibility. It doesn't matter how far away you're from if you're not accustomed to lightning and vulnerable to it.

Bear in mind, that the current "story" or understanding of how to explain visitors from the heavens is that these are anthropomorphic projections, and that this explanation is in the vast minority when looking at 6,000 years of human history. Every world religion has stories of heavenly visitors, and dismissing all these stories out of hand just because that is what is now in fashion, is not really rational. Reason wants real explanations for these claims, and blanket generalizations are the very worst kinds of reasons, since thay can never cope with the specifics of a single event, nor do they even try.

Whether we're being visited and have been throughout our history, is at base, a religious concern, that needs to be approached through empirical observation, as well as other methods for ascertaining the truth. We rely upon people's testimony enough to put people in prison for the rest of their lives, as well as to execute them, so obviously under the right conditions testimony generates high warrant for belief. When you have officers serving in the armed forces, swearing out affidavits saying they were there in Roswell and were threatened to shut up, and stayed quiet for decades until Clinton declassified the events and made them able to make a statement, it's irrational to not look at the statement and judge anyway. Those statements are very important, and available to anyone who feels the need to investigate the issues.

[GIThruster]

You can mitigate some of the material science issues of some of these engine types with magnetic nozzles or regenerative cooling.

Yes, but that's what's necessary to get to 5,000 Isp. BTW, if all you want is ultra-high performance rockets, John Cole's Metalic Hydrogen is a really good solution, but it's again a solution that can never bee safe, quick, convenient nor economical. If you search the work was done at Harvard about 7-8 years ago.

[Skipjack]

You can mitigate some of the material science issues of some of these engine types with magnetic nozzles or regenerative cooling.

Yes, but that's what's necessary to get to 5,000 Isp. BTW, if all you want is ultra-high performance rockets, John Cole's Metalic Hydrogen is a really good solution, but it's again a solution that can never bee safe, quick, convenient nor economical. If you search the work was done at Harvard about 7-8 years ago.

I am not disagreeing with the sentiment that antimatter propulsion is still ways off (if ever feasible at all). Metallic hydrogen is too uneconomic, as you say. I do see a potential for fusion and fission based propulsion though.

[AcesHigh]

You can trap anti-matter with a good enough magnetic trap just like you can do with normal matter.

The trouble is not just the low volumetric density of Penning traps, which are limited by the particles bumping into one another

ok GI, but that´s what I asked before, because I admit I am ignorant about this and I did not find the info I wanted.

why can we hold so many grams (or kilograms) of a gas or whatever, mechanically, and even though the particles are bumping into each other inside the mechanical container, still they are not HEATING, and in fact, they are losing energy with time...

and however, you guys are saying (I am absolutely NOT saying you guys are wrong, I am just trying to understand) that in a magnetic trap, even very small quantities of trapped particles would be bumping into one another and gaining energy and getting faster and therefore more difficult to hold (as it happens in fusion reactors, although I recon that in fusion reactors they are DESIGNED from the principle to make the plasma get hotter and hotter)

As I asked before, isn´t it possible to store cold (low level energy, previously cooled) anti-matter in a penning trap, with the penning trap funcioning as a mechanical recipient, that is, holding the matter or anti-matter WITHOUT heating it?

There is probably some catch in all of this that I am still not seeing.

, but also realize the trap only holds the fuel. Fission, fusion and anti-matter rockets and any combination of these, all still need to carry a rocket engine, and propellant. All you're doing is moving energy from a source other than the propellant itself as with chemical, to a higher energy density physical reaction. So you can get higher Isp's but these are still limited by materials science to about 5,000. When you read that Bussard said a poly-rocket could generate higher Isp's like 11,000, you need to realize he didn't wrestle with the limits of Inconel, etc.

Chemical rockets Isp's are limited primarily by the energy from the reaction to a few hundred. Fission, fusion and anti-matter rockets are limited by the materials used in the thrust chamber and bell to a few thousand. If you see Isp numbers like 11,000, you're looking at hand waving. And again remember, you're still looking at carrying your propellant so you're still looking at the rocket equation, which is not conducive to economical transport. This is stuff for sending small, select teams of astronauts out so the rest of us can live vicariously, not creating a golden age of human spaceflight.

yes GI. Propellantless is the way to go. Again let´s either keep aliens out of it and suppose it is possible ME Thrusters won´t work, or let´s suppose the aliens won´t ALLOW us to use propellantless thrusters.

[GIThruster]

why can we hold so many grams (or kilograms) of a gas or whatever, mechanically, and even though the particles are bumping into each other inside the mechanical container, still they are not HEATING, and in fact, they are losing energy with time.

Gas is not charged. Plasma is charged particles each of which repels all the others. They don't like each other and hate being squeezed in together.

[AcesHigh]

Even positrons have very poor production efficiency

http://www.cosmosmagazine.com/news/lase ... ntimatter/
well, the laser method has the potential to create 100 billion positrons per shot. Of course, what is really important therefore is how long each shot takes. Fastest lasers are like a quadrillionth of a second, therefore, the question is how long each laser shot needs to be to create those 100 billion particles?

the question of how you store enough to be useful. Once you account for the mass of the bottle containing your antimatter store realistic fusion fuels may have much greater available energy content.

which returns me to the question of why you can´t store more mass in a small magnetic trap.

why can we hold so many grams (or kilograms) of a gas or whatever, mechanically, and even though the particles are bumping into each other inside the mechanical container, still they are not HEATING, and in fact, they are losing energy with time.

Gas is not charged. Plasma is charged particles each of which repels all the others. They don't like each other and hate being squeezed in together.

ah, so that´s the catch. And what about using non charged anti-matter? (which would however bring the challenge of creating it in large quantities, since positrons are easier)

and holding neutral charged anti matter with stuff like this
https://en.wikipedia.org/wiki/Magnetic_trap_(atoms)

or this
https://en.wikipedia.org/wiki/Magneto-optical_trap

[D Tibbets]

In response to the last few posts-

I'm not sure what ISP thrust VASMIR has actually achieved, but up to 12,000 ISP is advertised. Certainly any material in contact with the hot plasma will be eroded relatively fast. In Hall thrusters and other ion thrusters that have been deployed, the ISP up to a few thousand is the limit due to the material grids that are used for acceleration. The obvious answer is to confine the hot plasma away from the material walls with magnetic and / or electrostatic fields. In some ways it is the same idea as the virtual cathode in the Polywell.

Bussard, who was no novice at rocket science, certainly thought very high ISP efficiencies were doable.Several of his papers are listed below and there are several others on Askmar.

http://www.askmar.com/Fusion_files/Fusi ... ulsion.pdf

http://www.askmar.com/Fusion_files/From ... 0Moons.pdf

Concerning antimatter production and storage, my previous post (edited) tried to give some sense to the scales involved. An effort at increasing antimatter production by several orders of magnitude is trivial and nearly useless. Many orders of magnitude in effort is needed. Not a thousand fold increase, or even a billion fold increase, but millions of billions for a tiny ship, and a thousand times more for a larger ship. The tankage (magnetic bottle) weight and volume is tremendous also.
Storing antimatter charged particles at cryogenic temperatures would certainly greatly decrease the gyroradius at any given B field strength. But it is not a free ride. The Coulomb collision cross section goes up at ~ the second power of the inverse of the temperature. Each ExB producing collision would result in much smaller random walk gyroradius guided jumps, but these collisions would increase tremendously. Just how the balance would work out is uncertain, but I suspect it may be a minor gain or even a loss in regards to magnetic containment. So again, tremendously strong magnetic fields would be required and tremendous confinement volumes would be required for any reasonable confinement times of any reasonable antimatter amounts.
The volume has to be tremendous so that you can reach useful quantities of antimatter because the density has to be keep as low as possible. It is a trade off. As the density increases the Coulomb collisions that drive ExB drift increases squared. That is why I suggested a magnetic bottle the size of the Moon. This may be excessive though. A magnetic bottle the size of England might do provided you can generate steady state B fields of millions of Tesla, giving you modest confinement times of perhaps millions of seconds (weeks) .
There may be tricks that can be used such as using lasers or some radio waves or something to kick ExB drifting particles back towards the center. These would probable require a fair amount of energy input, but hay, you have a very big tank of antimatter as a fuel tank. Note that I have stipulated the need for the antimatter to be in the form of an ionized plasma, and this plasma would need to be nearly charge neutral, which means you would need anti protons and postrons in the mix. This begs the question, why not just make antimatter iron. It would be a solid ball and you could suspend it with magnetic fields. Problem solved. Of course anti hydrogen has been produced, but only a few atoms, to fuse this to form some solid that is magnetic is very many orders of magnitude more challenging also.

Just producing positrons would be much cheaper energetically than producing antiprotons. But you get a correspondingly smaller energy out when you annihilate it with an electron. And as I said above, if you want useful quantities of antimatter, you have to produce both. As is often pointed out with the Polywell, deviations from a neutral plasma (or solid for that matter) can only be a tiny amount. In the Polywell there is ~ 1,000,001 electrons for every 1,000,000 positively charged ions (singly charged). Much more charge imbalance drives the electrostatic potential of the plasma to stupendous levels. It might take many billions of volts of potential to contain even a milligram of anti protons in a small volume. Without that potential the particles would blast through any obtainable magnetic field ,without even needing to consider ExB drift. Look up Coulomb explosions.

There are many many orders of magnitude improvement/effort needed, not in just one system, but in possibly many systems to utilize antimatter for thrust, even for antimatter "catalyzed" fusion. Even the Entrprise doesn't use antimatter for thrust. They use "Impulse Engines" for that. The antimatter drives the Warp engines and they never (that I know) suggest how much is used, just that if they lose containement of the stored antimatter a big mess occurs.

Dan Tibbets

[GIThruster]

And what about using non charged anti-matter?

The charge is what enables one to use magnetic confinement. Without the charge you can't use a Penning Trap and I don't know of another way to handle the stuff.

Try to keep in mind the impracticalities of manipulating quantities of anti-matter sufficient to drive a starship--this is a fantastical amount of energy. The fact it can be had in a small mass is almost insignificant compared to all the other consequences. When a rocket launch goes as badly as it can go and the fuel ignites on the pad you have a bad situation. Were that to happen with the same amount of energy in an anti-matter fueled rocket, the result would be far worse since all the fuel would ignite in the tiniest fraction of a second. Just the shock wave from such a thing would be a record breaker and nothing would survive it. Now remember that this anti-matter wants desperately to get out and join the rest of the universe, and if your trap fails, that's just what it will do. And remember that there is no efficient means to use matter-antimatter annihilation directly for propulsion except to haul along propellant in addition.

[D Tibbets]

As I mentioned in my last post. I see no conceptual reason why antimatter could not be stored as a chunk of solid material. Can you obtain magnatism in a pellet of frozen hydrogen? Transmuting to heavier elements might not be nessisary. For that matter has anyone ever made anti neutrons? The engineering considerations are astoundingly difficult, even with conceptual viability. If you can freeze hydrogen at some temperature close enough to absolute zero, will the vapor pressure be low enough that it has any usefull lifetime. Any vaporized hydrogen atoms would heat the container vigorously. Isolating a magnetic plug of solid antimatter (with very low vapor pressure properties) in a very good vacuum with external magnets is obvously straight forward. Any table top superconducting magnet suspending a magnetic object demonstrates this. Of course, as repeatedly mentioned, actually producing the antimatter pellet is an entirely different story.

As for an antimatter - matter explosion with the same total energy of say a chemical mixture or a hydrogen bomb producing a brilliant extremely short burn that produces a correspondingly greater blast wave intensity,I am uncertain. Just as with matter interactions like burning chemically or nuclearly, the particles have to come in contact. This involves issues of momentum, density, Mean Free Path, etc. It is a complex interaction. Also, for a blast wave to form an interacting medium is required. The explosive material itself can provide this material internally- like the blast wave- burning speed in a high explosive cord. But externally, without a medium like atmosphere, ground, etc. there is no significant pressure/ blast wave except for that provided by the explosive products expanding outward, and this would quickly disperse at inverse square law rates. The fireball of a nuclear explosion is mostly made up of super heated air.Nuclear explosions in space has no air to heat so only the expanding fusion products and radiation are manifest.
Certainly, the amount of energy per particle pair interaction is much greater, but this may produce a expansion of surviving particles at such high speeds (greater MFP) that subsequent interactions are delayed. A atomic bomb fizzle illustrates this. The bomb blows itself apart befor much of the fuel can burn. With antimatter the 'blowing itself apart' is somewhat different as the antimatter only has to touch a matter counterpart, but this would be delayed, much of the burning would slower. In space, a significant portion of the antimatter may escape without touching matter, and disperse in space.

It may actually difficult to produce a good antimatter- matter bomb that has good fuel burnup within desired time frames. The result is that at similar energy content ( a 1 pound antimatter- matter bomb verses a 1,000 pound fusion bomb) the blast effects within an atmosphere may be similar. Of course I know of no one that is eager to stand by a 1,000 pound fussion bomb that is about to detinate .
With points about the massive structure necessary to contain any plasma state antimatter, the antimatter bomb total wight might be 10,000 pounds or more, while the fusion bomb may only be 1500 pounds. The antimater bomb system weight is actually inferior to the fusion bomb. This could also be said for a rcket fuel tank utilizing these processes.

As pointed out though, even if you could build such antimatter devices and fusion bombs (fuel tanks and reactors), With the fusion bomb, it is relatively extremely easy to build in multiple layers of safty, while someone tripping over the power cord could trigger the antimater containment failure. An analogy can be can be made between fusion and fission power plants. Even in an ignition tokamak, a complete run away of the reactor would only consume a few grams of hydrogen. A fission reactor though could consume many kilograms of uranium or plutonium quickly. The fuel is contained within the reaction space. Then there is the contribution of the radioactive breakdown products scattered about. I'm uncertain but a liquid thorium fission reactor may mitigate this 'fuel stored in the reactor' vulnerability as only a small portion of the stored reaction fuel is inside the reaction space at any given time. By its very nature, such cannot be applied to antimatter. In a Polywell the possible amount of unintentional fusion would be even extremely less than a tokamak, because less hydrogen is in the machine at any given time and the power could be turned off in a tiny fraction of a second (no ignition - no burn up of any fuel already inside the reaction space). A runaway reaction, if possible at all, would be extremely trivial. An antimatter reactor is essentially a question of keeping the reactants separated, There is no other control. It might be compared to a fission reactor where the reaction rate is controlled by the control rods only. The fuel rods are fixed in place. If the active system controlling the control rods fail, the control rods naturally extract (reverse of what a well designed fission reactor would do). The fission becomes supercritical and rapid melting or explosion occurs. There are no available emergency measures like dumping in boron, or having fuel rod designs that limit heating like I think has been experimentally demonstrated in some advanced fission reactor designs. With antimatter the only possibility is to dump the antimatter container over the side and get the heck away quickly, aka Star Trek. This requires some forewarning of the failure and is unfriendly to your neighbors if you happen to be on a planet.

Dan Tibbets

[D Tibbets]

A comment about the magnitude of effort needed to create much antimatter from light. Actually matter- antimatter pairs.


http://discovermagazine.com/1997/dec/le ... matter1297

McDonald estimates that in another five or ten years this may be an efficient way to make small amounts of antimatter. But the technique will never generate a cheeseburger. For example, even if all the sun’s power could be focused on one spot, there still wouldn’t be enough energy, says McDonald, to make even an ounce of matter.

Of course antimatter can also be collected from several natural radioactive decays, etc.

Dan Tibbets

[Tom Ligon]

Sheesh, what makes any of you think you're qualified to talk about antimatter starships without getting a REAL science fiction author into the argument?

There are so many downsides to antimatter you just don't want to go there. We have no known way to make it economically, and storage is obviously problematic. Yeah, I'm an Analog subscriber and I've seen the arguments for it. Clearly the energy density is superb, but for the time being it is just plain SF.

What you REALLY want is a direct way to exploit E=mc^2. Picture that you could do some magic transformation and "swap signs" on the particles, making antimatter from matter on the spot and annihilating it without the bother of storage. But if you can imagine that, what about just pulling loose the pins that create mass and letting the energy fly? So getting to the bottom of this Higgs Particle thing could have some payoff.

Mind you, a physicist I know who thinks superluminal reactionless drives are possible also thinks Peter Higgs was full of baloney.

Dark matter may be self-annihilating (these particles may be their own anti-particle). There's supposedly more of it than there is conventional matter. You don't have to make it, you "just" need to learn to manipulate a particle that supposedly only responds to gravity. I introduced the idea of the dark matter interstellar ramjet back around 2008. Thus, figuring out what dark matter is could solve interstellar transportation. At the very least, it is essential to understanding the next 500% or so of physics.

And what happens when dark matter annihilates? Is that where Dark Energy comes from? We may be trying to answer these questions understanding only about 4% of physics.