Update on Positron Dynamics -working towards Antimatter propelled cubesat in 2018

Antimatter is the most energy dense material in the universe. Positron dynamics core innovations is the ability to generate intense beams of cold positrons using an array of moderators. They use a radioisotope as a source of positrons. They react the gamma particles to get a charged ion which they direct with magnetic fields for propulsion.

Rocket engines based on this would have exhaust at 10% of the speed of light.

They are initially targeting hyperefficient propulsion for cubesats and other orbital satellites.

The moderator device — which measures a tiny 3×3 millimeters — uses several layers of silicon carbide film to extract individual positrons and an electric field to cause the particles to drift to the surface of each layer, where they can cool.

* fusion reactions will be used to transfer the kinetic energy of the gamma-ray producing positron beam into charged particles.

* Positron Dynamics should be reporting on laboratory demonstration of “scalable” thrust using positrons in tests that already were tried this year.

* Positron-powered launch of small “cubesat” satellite into low-Earth orbit, demonstrating orbital change from positron propulsion. mid-2018 to mid-2019.

* Use propulsion system could be used in satellite constellations, for example — as part of a global network of broad-band internet, enabling virtually anyone on the planet access to the internet during the 2020s

* Launch of another rocket to further demonstrate the feasibility of positrons to power a spacecraft in about early 2020 and follow by a succession of other unmanned spacecraft over a period of years

* Launch of a positron-propelled spacecraft to Mars. In the 2030s.

Correction – had indicated that $1.5 million had been raised for Positron Dynamics on Propelx –

Propelx is still raising the $1.5 million bridge round for Positron Dynamics. It is over 80% raised. Accredited investors can still contribute to Positron Dynamics.

In Jan 2017, Propel(x), the online angel investment platform that helps investors source, evaluate, and fund pioneering science and technology startups, has been raising $1.5 million for Positron Dynamics.


In March 2017, Gabrielle, with new ExB plates, ready to do battle with energetic positrons!

In February they were working a billion positrons per second.

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1
TheRadicalModerate

It should probably be noted that Positron Dynamics isn't a space propulsion company; it's an antimatter company. To be sure, antimatter thrusters sound like a pretty good business if they can figure them out, but the core business model here is to provide cold positrons for any number of applications.

2

Electrons & positrons with low mass and high speed means very low thrust and very high Isp for acceleration towards some appreciable fraction of speed of light, over a long period of time. So the only voyages this thing might be useful for are interstellar ones. Why bother using this for orbital station-keeping, when ion-propulsion can already do something similar, with somewhat higher thrust and lower Isp, and no radioactivity? Actually, maybe it could be useful for exploring the outer part of the solar system, around the Oort Cloud.

3

Well, if its any use whatsoever, here are a couple of interesting things to remember. You get:

325 N-s/MOLE's worth of electrons, accelerated to 1 MeV. 1 mole's worth is 1 faraday's (different from farad!). Which is about 96,400 ampere-seconds of 'em. At 1 MeV, they're definitely relativistic, at about 96% c.

Another is:

27,800 N-s/mol for alpha particles. Same 1 MeV. They go slower, have lower ISP and thus are "more to push against". More newton-seconds.

13,900 N-s/mol for accelerated naked protons. 1 MeV.

So, if (say) one were ionizing hydrogen at the gap between a couple of large, well-separated, charged plates (carrying 1,000,000 volts of potential), the electrons would fly out of the positive grid and impart –325 N-s of force on the thing (relative to the other end). The proton end (flying out the negative grid) would produce over 13,900 N-s of force. You'd end up with 13,575 N-s of force away from the proton end. Per mole of hydrogen. Per 96,400 amp-seconds of 1,000,000 V acceleration. 96.4 billion watt-seconds or joules of acceleration. ISP is huge. 1.3 million.

Kind of cool, ain't it?
I think so.

GoatGuy

4

Don't you have to throw the electrons out the back with the protons or else build up a wicked charge? Hall effect thruster has a neutralizer e-beam.

5

wrote paper years ago, pos. / elec. have almost NO mass, therefor, F=MA. To make your device work I would suggest adding an ablation plate to increase mass of propellant.

6

So… critically thinking, and taking the load of spaghetti presented, and the tangled (unclear) ideas… and the chick with the 3 little copper PCBoards … and the claim that they're accelerating a strong beam having billions of positrons per second particle rate …

What I get is that they're using radioisotopes to create anti-electrons. But why? Seemingly to annihilate themselves (perhaps with static-plate electrostatic acceleration?) against some ordinary electrons, creating gammas over 511 keV. Why? With higher energy gammas, to produce some charged particle pairs, which in turn can be accelerated out the bunghole of the spacecraft in order to accelerate it in turn.

Hmmm… that doesn't quite work out, but OK. Maybe.

The disingenuous part tho' is plugging a wish-probe graphic with week-long trips to Mars, month long to Io and season long to Pluto (or whatever). A few years to our nearest neighbor stars. This is deeply misinforming, in that it suggests that "see we got the antimatter, now lets get to the stars!". Kind of like citing the invention of the radio tube and then putting up a graphic of an NVidea GPU sporting 10 billion active transistors.

The problem is that Joe and Janet Enthusiast don't have a clue that theres a similarly impossible stretch involved.

Oh well.

As BRETT sez, "fission fragment propulsion is promising". Paraphrased. He's right. The "problem" with normal radioisotopes is that, well, there's no ON-OFF switch. They're like having bags of TNT pellets, where every once in awhile a pellet decides to go BOOM spontaneously. As long as we're employing those BOOMs to a propulsive end, continuously, well … no issue. FISSION tho is like having an ON-OFF switch. Radioactive and hopefully charged particles "on demand".

Then if you have an electable source of charged particles, and you put it in the middle of a large pair of charged open grids, out one side will fly the positive particles (the neg plate) and out the other side will rush the negative particles (electrons, toward the positive plate). Interestingly, if you had one of the simplest systems ( the alpha particle, +2 charge, 4 AMU mass, a naked helium nucleus), The propulsive effect is always weighing (bad pun) toward the alpha.

You can choose either to kick the exiting alphas with an electric field to move faster (which tho' is kind of futile) or you can choose to REFLECT the wrong-direction alphas in the opposite (good) direction. This can generate a lot of thrust per particle.

This can also be done with much heavier particles. We physics people tho' tend to like alphas: many nuclear processes produce 'em, and apart from their energy they're otherwise pretty innocuous. Helium. Not exactly a death ray.

So after all that, I remain kind of unconvinced.

Also, I'm disappointed by the endearing but fallacious top graphic. You really need to do the calculations as to how many particles must be deflected, and at what energy, before you project getting even to Mars let alone the Stars. And in turn, they need to produce an "energy / fission / rate" budget that has fairly uncomplicated physics to confirm that its "right".

Just grumping…
GoatGuy

7

Ok, looking up a prior article on Positron Dynamics, here of all places: https://www.nextbigfuture.com/2016/10/positron-dynamics-vision-of-antimatter.html

The plan is that the positrons cause a decay step in ordinary matter that leads to the production of muons.

The muons then catalyze fusion in a target, Ideally several fusions per muon.

The charged fusion products are then used for the exhaust.

They aren't anticipating energy gain from the muon produced fusion, they know that's been proven a loser. But they do expect that the whole process will give them some energy gain over just the positrons, because they expect some gain in the muon production step. Then what the muon induced fusion gives them is heavy charged particles that make a good exhaust.

It could work. My concern would be that the additional steps, while they multiply the thrust, also multiply the mass of the system. They seem to think the entire process can be packed into a cubesat. I'd like to see it.

8

IF (iffff) muon-induced fusion is indeed a thing, then seems to me that the quest for fusion becomes a quest for strong positron (muon) sources. Doesn't have that mainstream kinda feel to it, but hey, if it works, then great.

9

No, muon catalyzed fusion is an old, old concept, already known to be a dead end. You don’t get enough fusion reactions per muon to generate enough energy to make more muons. The problem is that the muons aren’t stable, so they don’t last long enough.

But if you have a source of muons that doesn’t require electricity, like say cold positron induced radioactive decay, you might use it in some form of nuclear battery.

10

So as always we need to ask the question of how heavy their power supply will be because kinetic energy out will be less than the power produced (electrical and thermal) of the power plant.

True story:

Years ago I got a coffee from a local coffee shop and somehow found out that the barrista was an engineering student. He was interested in VASIMR and shortening transit times to Mars and wanted to work on plasma propulsion. My advice to him was to ignore making thrust and to focus on making a powerplant to power engines. "We have all these interesting propulsion systems and nothing that can power them" was about what I said.

Same with this device. Ultra high ISP engine that basically converts some % of input energy to thrust. What generates the energy in the first place?

11

Fission fragment rockets are a promising technology, and if they really have a good way to get better performance out of them in small enough packages for cubesats, good.

12

This is BS.

13

Ummmm. There is not a ton of energy in positron annihilation. 511KeV gammas emitted with angle of PI beteen them. Sniff, sniff, sniff? I smell BullSh1t! Looks like this guy got $1.5E6 to hang out with his pretty little Asian intern for a couple years. Maybe something good will come out of it, like marriage.

14

Speaking of BullSh1t!, can you maybe leave the demeaning 'pretty little Asian intern' and 'she's only there as a potential mate for someone' BS out in the future?

FYI: http://gabriellelaguisma.com/

15

Dude, after following your link, it appears that I am spot-on. Here we got a 2016 grad with a CV that looks like, well an intern's CV (like mine looked in 2000). Her research project appears to be changing the arrangement of an independent spent fuel storage installation from a compact square pad to a spacious circular arrangement. How quaint; I'll suggest it to my management. Maybe you got the hots for this Filipina Tom Craver?

16

It wasn't the "intern" part of your remark that was offensive, as I'm sure you well know.

17

Again, did you mean $1,500,000? Do try to keep away from 'e' (computer data) formatted numbers, buddy. You have plenty of space to type in the common western (US) form. Or if you're British or a European, go ahead: $1.500.000 is fine too. We'll understand.

It does look like the team hooked a pretty energetic Asian intern. Schweet.

The 511 keV is too low to initiate gamma → particle creation. Even if you get a pair of the suckers. Most of my read of this is "bullcrackers", too. But they're having fun. And getting money for it, to boot. Bravo.

GoatGuy

18

You do realize that some people are wired in such a way that if they find another's complaint trivial, it becomes a delight for them to continue to irritate the complainer. You are almost forcing me to continue using this notation. I'll do my best to fight the urge.

19

I'll give you 1E0 points for this.

20

LOL. Perhaps you might consider 1.5×10⁶ notation instead? That'd be much closer,. But I know… dâhmned hard to type in. Remember, I too am a scientific programmer (ground my wisdom teeth down on FORTRAN, wrote a FORTRAN → C converter (in C) to ease the pain. I definitely like 'e' notation, and I wish way more people understood it. But except for those math-y souls that dive into big and small numbers in Excel, or who science-or-technology-or-medicine program, most regular folk just don't get it. Somewhat annoyingly worse are the articles that say such things as 1014 electrons (say) when they mean 10¹⁴ of 'em. Or 1e14.

Anyway, I'll plus-one you too. "What manna goes around, comes around"

GoatGuy

21

wrote a FORTRAN → C converter (in C) to ease the pain

Said nobody ever. Ok that's not fair FORTRAN is simple enough that you could translate it in to C.

22

TBF this article is very poorly written "They react the gamma particles to get a charged ion which they direct with magnetic fields for propulsion" yikes, LOL.

From what I've been able to gather about this company they're trying to use positron annihilation from an isotope of sodium as a source of muons to catalyze a fusion reaction which they use as a source of thrust. Pretty much just a jacked up over engineered radioisotope rocket (if it ends up working).

23

Here is a much better writeup:
https://www.nextbigfuture.com/2016/10/positron-dynamics-vision-of-antimatter.html

Perhaps we should read that site instead?? Err....

Anyway, this writeup completely ignores all the useful information in the previous article and just adds photos of the attractive Gabrielle. I think Brian might have gotten a bit distracted here.

To sum up, as DelfonicSonic put it:
The real plan is

positron emission: ²²Na → ²²Ne + 1 e⁺ + 0.94 MeV of kinetic energy
positron annihilation: e⁺ + matter → pion (5%) or kaon (95%)
kaon decay: kaon → muon (80%) in 20 nsec
muon capture: muon + D or T → mD or mT
fusion (1): mD + T → ⁴He + ¹n + muon (non-consumed) (0.01 – 0.1 nsec)
fusion (2): mT + D → ⁴He + ¹n + muon (non-consumed) (0.01 – 0.1 nsec)
fusion (3): mD + D → ³He + ¹n + muon (non-consumed) (0.07 – 1.5 nsec)
muon decay: muon + time → electron + neutrinos (2,200 nsec)

²²Na (sodium missing one neutron) is almost perfect. Halflife of 2.6 years.

24

So am I understanding correctly that they essentially throw away the kinetic energy of the positrons - 'cooling' them so they will go slow enough to quickly annihilate over a short distance?

If so, it seems like the whole 'anti-matter yields a lot of energy' discussion is off the mark, if so - they're 'merely' doing muon catalyzed fusion, and that provides the real energy in the reaction mass?

25
TheRadicalModerate

It's the e+ + matter part that's weird. There is apparently an e+ + e- --> μ+ + μ- annihilation pathway, but it's at GeV of center-of-mass collision energy, which doesn't sound like something you'd use with cold positrons. I went rummaging around for an e+ + n reaction and couldn't find it. It's usually proton cosmic rays that make K/π particles in the upper atmosphere, which decay to μ.

Muon-catalyzed fusion is a real thing. Basically, the muon takes the place of a D or T electron, which forms a D2 molecule where the nuclei as close enough to tunnel and fuse. But the muons either decay too fast, or are carried off in some percentage of the reactions by "alpha-sticking", where the fusion energy doesn't ionize away the muon.

26

if it ends up working

I think it already worked; it got funding. Ryan Weed and Gabrielle are flying first class to Palawan for a "conference".