Matter/Anti-Matter: Explaining Space Travel Applications

[Anti-Meson]

If you read the paragraph, you'll see that the open question is on what causes the positrons rather than that there are positrons. Anytime you have a 511 Kev spike, that's a positron annihilation line, there are no known physical processes that produce a 511 Kev spike other than anti-matter annihilation. You can go into http://adswww.harvard.edu/ for more details. (Search for pair production)

I think the majority of people here is misinterpreting my position, in that case I shall clarify, if I haven't done so already.

I do not deny the whether of antimatter is real or not, laboratories have shown that anti-matter is real and pair production is such an experiment. What I do deny is that antimatter exists in nature. By exists I mean it can it exist without be unaffected, similar to baryonic matter. However, this is not the case since it will simple annihilate with any baryonic matter and the end result is either pure energy, in form photons or more baryonic matter - not antimatter.

 

[S.Vasojevic]

As Phyisab pointed, it is about how much energy you can 'carry' on a space ship, not about mining the antimatter from nature. With antimatter you will get engines with highest specific impulse possible. Problem of puting that energy to use remains, because it comes as gamma rays, but nevertheless concept seems plausible.

 

[DaveC426913]

I think the majority of people here is misinterpreting my position, in that case I shall clarify, if I haven't done so already.

I do not deny the whether of antimatter is real or not, laboratories have shown that anti-matter is real and pair production is such an experiment. What I do deny is that antimatter exists in nature.

No, your position is very clear and unambiguous. You are arguing that antimatter does not exist in nature. That's not true.

By exists I mean...

Trying to change the meaning of the words you used after-the-fact does not make your original argument any less wrong.

Rather than try to backpedal, just concede that you made a claim you should not have made. Nor is there any need to redirect what you meant to say, we've got that covered: anti-matter does not exist in nature in any large enough quantity or for any length of time to be of use in the way we've been discussing it here. This we can agree on.

 

[DaveC426913]

Point of order: the OP asked about antimatter travellnig backward in time. I said 'no' but the OP provided a link to some article about it. That link seems to have gone missing. Was it deleted? I never had a chance to read it.

 

[Phyisab****]

yep seems to have been deleted

 

[Redbelly98]

What I do deny is that antimatter exists in nature. By exists I mean it can it exist without be unaffected, similar to baryonic matter.

Here is a link to an article in a peer-reviewed journal, Nature, that discusses large quantities of non-manmade positrons:

http://www.nature.com/nature/journal/v451/n7175/full/nature06490.html

... our result implies that up to a few times 10⁴¹ positrons escape per second from a typical hard LMXB.

 

[qraal]

Point of order: the OP asked about antimatter travellnig backward in time. I said 'no' but the OP provided a link to some article about it. That link seems to have gone missing. Was it deleted? I never had a chance to read it.

In a Feynman vacuum diagram the antiparticle-particle pair has the regular matter going forward in time and the antiparticle going backwards. You can represent antimatter as time-reversed matter according to Feynman, but there's no way of verifying such time-reversal with tiny amounts of antimatter. Most interactions are time-symmetric!

 

[Frame Dragger]

How can you argue that anti-matter doesn't exist in nature? Did you just mean to say that matter dominates antimatter in the observed universe, or are you on drugs?

@graal: Hawking Radiation would confirm that mechanism, if it were to be observed in an earthbound analogue. (sonic - phonons)

 

[qraal]

How can you argue that anti-matter doesn't exist in nature? Did you just mean to say that matter dominates antimatter in the observed universe, or are you on drugs?

@graal: Hawking Radiation would confirm that mechanism, if it were to be observed in an earthbound analogue. (sonic - phonons)

What would an 'antimatter analogue phonon' look like? Freaky. Amazing that such a neat analogue can be found in superfluidics to Black Holes. The cross correspondances between such disparate areas of physics is truly a wonder!

 

[Anti-Meson]

No, your position is very clear and unambiguous. You are arguing that antimatter does not exist in nature. That's not true.

That is not my argument.

Trying to change the meaning of the words you used after-the-fact does not make your original argument any less wrong.

I am trying to explain to you what I mean by doesn't exist. I am not "changing the meaning of the words".

Here is a link to an article in a peer-reviewed journal, Nature, that discusses large quantities of non-manmade positrons:

http://www.nature.com/nature/journal/v451/n7175/full/nature06490.html

Very interesting indeed. Further investigation into the 511 keV signature is needed. Currently, I am not convinced. Let me point you to this article from APS:

http://prl.aps.org/abstract/PRL/v92/i10/e101301

The source of positrons in the galaxy is the subject of much debate...we argue that light DM particles (
1–100 MeV) annihilating into e^-e pairs in the galactic bulge may be the source of the observed 511 keV emission line

How can you argue that anti-matter doesn't exist in nature? Did you just mean to say that matter dominates antimatter in the observed universe, or are you on drugs?

This is sort of my argument but not entirely. I am not arguing that normal matter dominates antimatter in the observable universe, I am arguing that it does not exist on an appreciable time scale - it is simply annihilates. Putting it another way it does not coexist with normal matter.

 

[DaveC426913]

I am trying to explain to you what I mean by doesn't exist. I am not "changing the meaning of the words".

The time for you to say what you "really meant to say" was back when your original claim was shot down as patently false. Instead of demanding evidence to the contrary you could have just said "OK. Point made. Here's what I meant to say".

The rest of this goalpost-moving is for your personal benefit.

I am arguing that it does not exist on an appreciable time scale

Sure, now you are. Except it was left to me to make that correction.

Putting it another way it does not coexist with normal matter.

The thing about the vacuum of space is that things can get pretty far without encountering matter. In terms of particles with short lifespans, antimatter particles are comparatively immortal.


None of this is accomplishing anything anymore. The facts have been stated, the falsehoods falsified. Let's move on.

 

[Anti-Meson]

The time for you to say what you "really meant to say" was back when your original claim was shot down as patently false. Instead of demanding evidence to the contrary you could have just said "OK. Point made. Here's what I meant to say".

The rest of this goalpost-moving is for your personal benefit.

Sure, now you are. Except it was left to me to make that correction.

I do believe I had implicitly stated this from the start.

...any contact with normal baryonic matter and it will simply annihilate itself.

The thing about the vacuum of space is that things can get pretty far without encountering matter. In terms of particles with short lifespans, antimatter particles are comparatively immortal.

Space is far from vacuous. A plasma from solar winds permeate space meaning antimatter particles are far from immortal.

Let's move on.

Agree.

 

[twofish-quant]

One thing about anti-matter is that it is routinely used in medicine see...

http://en.wikipedia.org/wiki/Positron_emission_tomography

 

[Anti-Meson]

PET is excellent at exploiting the natural decaying of radionuclide isotopes. Although all of the isotopes are artificially created by means of bombardment.

 

[Vanadium 50]

Although all of the isotopes are artificially created by means of bombardment.

True, but that is a statement about medical practicality, not existence. I-131 is artificially created for medical treatments, but one would hardly use this to argue against the existence of iodine.

There are natural positron sources. The most common of them is probably the beta+ decay of potassium-40.

 

[Frame Dragger]

True, but that is a statement about medical practicality, not existence. I-131 is artificially created for medical treatments, but one would hardly use this to argue against the existence of iodine.

Anti-Meson might...


Look, there is a lot of effort going into saving one man's ego. If he hasn't learned to say, "Whoops, I was so wrong it hurts a little" as we ALL HAVE, then let him keep his misconceptions. This is no longer about informing someone either... in essence, this has become an intellectual curb-stomping. I'm really enjoying it, but I think it would be kinder to cut this individual loose at this point.

Lets all just pretend that Anti-Meson comes from a universe that lacks the Weak nuclear force, and therefore beta decay NEVER OCCURS! Ok?! I'll do it if everyone else will...

 

[Anti-Meson]

True, but that is a statement about medical practicality, not existence. I-131 is artificially created for medical treatments, but one would hardly use this to argue against the existence of iodine.

There are natural positron sources. The most common of them is probably the beta+ decay of potassium-40.

You do not understand my argument, I am not arguing against the existence of iodine. What I am arguing however is that antimatter simply does not exist, naturally on earth. PET nuclides are artificially created to induce antimatter - positrons. Potassium-40 is natural (0.0117% of all Potassium) but the fact that we know it undergoes positron emission is from theoretical models not physical observation. From our model of the big-bang heavy atoms (of which potassium-40 would be classified as) form at about 10⁸ years after the big-bang. Considering that Potassium-40 has a half life of 1.265 x 10⁹ years that means we will only be able to provide evidence to our model by observing a natural existing positron 10¹⁶ years after the big-bang. Approximately, ten million years from now.

Anti-Meson might...


Look, there is a lot of effort going into saving one man's ego. If he hasn't learned to say, "Whoops, I was so wrong it hurts a little" as we ALL HAVE, then let him keep his misconceptions. This is no longer about informing someone either... in essence, this has become an intellectual curb-stomping. I'm really enjoying it, but I think it would be kinder to cut this individual loose at this point.

Lets all just pretend that Anti-Meson comes from a universe that lacks the Weak nuclear force, and therefore beta decay NEVER OCCURS! Ok?! I'll do it if everyone else will...

This is not about my ego, I am making an argument by not appealing to emotion. Additionally, I do not believe that the weak nuclear does not exist (check my PF username- what does it say?), if it didn't I wouldn't be sat here writing this, none of this universe would exist.

 

[Astronuc]

Please let's keep the thread on topic - which is about explaning the process of matter anti matter and how it could be used in space travel.

Quite simply, anti-matter in useful quantities would have be produce by colliding accelerators (proton sychrotrons). However, the production rates are extremely inefficient, and currently the capacity is on the order of picograms per year, meaning it would take a trillion years to produce ~1g.

Anti-matter is theoretically ideal since it would reduce the propellant mass required for a long mission. Chemical propellant produce eVs per reaction, fission produces 200 MeV per fission, but less than 1 MeV/amu, and fusion produces a few MeVs per amu. Anti-matter anihilation produces 100's of MeV/amu.

Anti-matter would be released into a stream of hydrogen propellant where it would anihilate and heat the propellant - possibly to plasma temperatures which would require a magnetic confinement system. Otherwise, at lower temps, it is more or less a conventional hydrogen thermal rocket.

BUT - antimatter production is extremely inefficient, and it requires complex storage (one has to produce anti-protons and positrons with which to form anti-hydrogen. Adding anti-neutrons to the problem greatly enhances the complexity).

Conisder that controlled fusion has proven rather elusive over the past 6 decades.


Whether or not anti-matter exists in Nature is irrelevant. It certainly doesn't exist in useful quantities, and even if it did, it would be difficult to collect with something made of matter -even with a magnetic bottle or confinement/shielding field.

If the thread does not remain on topic, the thread will be locked.

 

[Redbelly98]

I'm no expert, but as I see it the problems with using antimatter for rocket propulsion are:

1. Our inability to produce antimatter in useful quantities.
2. Our inability to produce it efficiently.
3. Our inability to store it.

Is there anything else that's not really covered by these reasons?

 

[Frame Dragger]

Please let's keep the thread on topic - which is about explaning the process of matter anti matter and how it could be used in space travel.

Quite simply, anti-matter in useful quantities would have be produce by colliding accelerators (proton sychrotrons). However, the production rates are extremely inefficient, and currently the capacity is on the order of picograms per year, meaning it would take a trillion years to produce ~1g.

Anti-matter is theoretically ideal since it would reduce the propellant mass required for a long mission. Chemical propellant produce eVs per reaction, fission produces 200 MeV per fission, but less than 1 MeV/amu, and fusion produces a few MeVs per amu. Anti-matter anihilation produces 100's of MeV/amu.

Anti-matter would be released into a stream of hydrogen propellant where it would anihilate and heat the propellant - possibly to plasma temperatures which would require a magnetic confinement system. Otherwise, at lower temps, it is more or less a conventional hydrogen thermal rocket.

BUT - antimatter production is extremely inefficient, and it requires complex storage (one has to produce anti-protons and positrons with which to form anti-hydrogen. Adding anti-neutrons to the problem greatly enhances the complexity).

Conisder that controlled fusion has proven rather elusive over the past 6 decades.


Whether or not anti-matter exists in Nature is irrelevant. It certainly doesn't exist in useful quantities, and even if it did, it would be difficult to collect with something made of matter -even with a magnetic bottle or confinement/shielding field.

If the thread does not remain on topic, the thread will be locked.

Above all, every respectable study has shown that even with H->He Fusion (Edit for clarity: fusion as a power source for creating antimatter), the power required is prohibitive. The yield of antimatter is always in a pretty straight linear relationship with the power (electricity in this case) put into the process.

That said, while it's certainly unlikely that anti-matter exists in quantity in the observed universe, it's not a certainty. I personally don't believe it, but there have been arguments for 'patches' of antimatter isolated from matter, and while it annihilates immidiately there are reactions =/> energetic than any on Earth which presumabely create short-lived anti-matter.

As a drive-fuel, I can't think of anything worse. One thing Star Trek definitely appreciated was that the only 'fail safe' a matter-antimatter reactor can have on a spaceship, is to be violently ejected. ANY hint of containment failure for the antimatter, any leakage or loss of power, and BLAM, suddenly your whole ship is the other half of the fuel equation.

Finally, as a fuel, it doesn't produce 100% energy that is immediately useful, every time. Depending on the matter/antimatter, you could be losing up to 50% of the reaction to worthless (from our perspective) neutrinos! Of course, the most 'out there' reason would be that an antimatter drive would by definition be almost indistinguishable from a very powerful BOMB. For those victims of Differential Aging returning to a populate in their 'future' (I assume the antimatter rocket goes near c after all), or aliens encountering our intrepid vessel, might shoot first and ask questions later.

Oh... and landing and takeoff? WOW. Tensiooooooon!

 

[DaveC426913]

As a drive-fuel, I can't think of anything worse. One thing Star Trek definitely appreciated was that the only 'fail safe' a matter-antimatter reactor can have on a spaceship, is to be violently ejected. ANY hint of containment failure for the antimatter, any leakage or loss of power, and BLAM, suddenly your whole ship is the other half of the fuel equation.

Of course, the most 'out there' reason would be that an antimatter drive would by definition be almost indistinguishable from a very powerful BOMB. For those victims of Differential Aging returning to a populate in their 'future' (I assume the antimatter rocket goes near c after all), or aliens encountering our intrepid vessel, might shoot first and ask questions later.

Well, it's all a matter of technology comfort-level. A century ago, the idea of harnessing nuclear power safe enough to power a vehicle was ridiculous too.

 

[Frame Dragger]

Well, it's all a matter of technology comfort-level. A century ago, the idea of harnessing nuclear power safe enough to power a vehicle was ridiculous too.

Define 'ridiculous'. Some people would find the notion of floating nuclear cores with 16 verticle launch tubes filled with nuclear WEAPONS to be 'less than safe'.

The difference is this: antimatter is always going to annihilate with matter upon 'contact', and that is a unique danger of any fuel. Sure, some things are pyrophoric, or hydrophoric, etc... but 'matter' phoric? Something that will explode VIOLENTLY if a normal particle even looks at it the wrong way?

Eh. Safe perhaps, but a 'bottle' of antimatter is still going to be indistinguishable from a devestating bomb, and I suspect that would be a bad first impression. After all, you can't just take the reactor from a submarine and turn it into a WMD just by crashing it. You can create environmental havoc, but a 'starship' could turn a city into a smoking crater, and blowing it out of the sky at low altitude isn't an option... that's an airburst. (EDIT: That would be the final point... upon launch an antimatter vessel (containing or fueled by) would be impossible to fail safe.

 

[DaveC426913]

Define 'ridiculous'. Some people would find the notion of floating nuclear cores with 16 verticle launch tubes filled with nuclear WEAPONS to be 'less than safe'.

Yet we do it routinely.

The difference is this: antimatter is always going to annihilate with matter upon 'contact', and that is a unique danger of any fuel. Sure, some things are pyrophoric, or hydrophoric, etc... but 'matter' phoric? Something that will explode VIOLENTLY if a normal particle even looks at it the wrong way?

Agreed. If left to its own devices, antimatter will annihilate.

Then again, hydrogen is almost spontaneously combustive when in the presence of oxygen. And it'd be pretty hard to have a failure in containment without an associated presence of heat, spark or any other ignition source.

 

[Frame Dragger]

Yet we do it routinely.

We're a ridiculous species.

 

[MotoH]

Define 'ridiculous'. Some people would find the notion of floating nuclear cores with 16 verticle launch tubes filled with nuclear WEAPONS to be 'less than safe'.

It is a lot safer than keeping them in concrete bunkers on land!

 

[DaveC426913]

It is a lot safer than keeping them in concrete bunkers on land!

Not sure of zero is any safer than zero. Has there ever been a accidental detonation or contamination either in land silos or sub-silos?


Anyway, the point is that we routinely play with extrremely dangerous substances. Granted, antimatter is an order of magnitude worse (OK, it is probably as bad as bad can theoretically get) but still, failure is failure. We built the Hindenburg. We built the Challenger. etc.

 

[Frame Dragger]

Not sure of zero is any safer than zero. Has there ever been a accidental detonation or contamination either in land silos or sub-silos?


Anyway, the point is that we routinely play with extrremely dangerous substances. Granted, antimatter is an order of magnitude worse (OK, it is probably as bad as bad can theoretically get) but still, failure is failure. We built the Hindenburg. We built the Challenger. etc.

My personal favourite, and I will find an article for more detail later; the Russians (of which I am half) are slapping 3 RMBK-1000 Reactors on a BOAT to supply ready nuclear power for expeditions to Siberia and other locales needing a boost to their grid for a while. These ships will have backup diesel generators (sound familiar yet?), but to run the reactors will require some standard current from the mainland to run the reactors and systems.

Although it IS possible to shield a boat's hull from a molten core, for cost and timing reasons this project is going ahead without such shielding. Radioactive steam boiling from a nuclear reactor that has melted through a ship's hull would be a catastrophe. Ahhh the RMBK-1000... it was good enough to Chernobyl, it'll be good enough for this.

@DaveC: Failure is failure, but an antimatter failure is the highest yield failure per mass possible by orders of magnitude. The fact that either the integrity of an exotic material, or a constant supply of power to some kind of trap would be required to maintain antimatter's segregation from EVERYTHING else means that it is a double whammy. As you've pointed out, the road to progress is littered with failures. The question then, is given that immutable fact, can a planet-bound civilation afford the dangers of a learning curve with anti-matter?

 

[Astronuc]

I'm no expert, but as I see it the problems with using antimatter for rocket propulsion are:

1. Our inability to produce antimatter in useful quantities.
2. Our inability to produce it efficiently.
3. Our inability to store it.

Is there anything else that's not really covered by these reasons?

Answer to question - No.