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is that better okay yes

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well this is uh more of a technical talk

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uh but partly inspired by

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the fact that ufo reports frequently

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discuss impressive maneuverability at

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with

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usually no indication of conventionally

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known drives

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and to cut to the chase just in case i

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should run out of time

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a a sufficiently advanced technology can

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use

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antimatter annihilation to power a

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reaction drive whose only exhaust is an

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this would not be visible it would be

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very hard to detect by any means

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but it is potentially a testable

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hypothesis from

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retrospective evidence that already

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exists

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just as a note by a sufficiently

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advanced technology

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i mean something that can

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accomplish anything that can be known

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that

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is known to be physically possible uh

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but that does not require any

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new physics simply uh on the grounds

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that uh

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i felt that a hypothesis is

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more credible if it sticks to things

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now there's been a fair amount of

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discussion

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about theoretical space propulsion

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at the moment the only physics we know

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of

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relevant to space propulsion involves a

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law of equal action and reaction

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the only way you can move in one

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direction

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is to throw something else reaction mass

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as i call it

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in the other direction there are some

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that basically involve getting your

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reaction mass from outside the vehicle

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but they still adhere to newton's third

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law

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and the most powerful known reaction

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i i was told after i submitted my

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abstract that it would be good to

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provide a brief primer on on what

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antimatter

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is to begin with so every type of

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particle

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making up normal matter has a

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corresponding anti-particle

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um the relation between antimatter and

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normal matter

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is that uh every measurable property

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is either identical or exactly the

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opposite

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between the two mass is one of the

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identical properties

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antimatter particles have the same mass

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as matter particles

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electrical charge is one of the reversed

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properties

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the anti-electron is also called the

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positron because it has a positive

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charge

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when matter and antimatter meet they

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annihilate releasing energy

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and just historically the first

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anti-particle discovered was the

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okay now electron positron

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annihilation is nice and simple they

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simply meet each other

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and convert into a pair of gamma rays

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carrying all of the energy

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now in accelerators we've been studying

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anti-protons for

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decades now their annihilation is more

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complicated

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partly because a proton is a composite

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object made of three quarks

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an antiproton of course is made of three

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antiquarks

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and partly because the energy release is

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so much bigger that completely new

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particles

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or rather particle antiparticle pairs

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can be created out of the energy

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this is a reversible process but there

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is no material particle lighter than the

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electron so there's no alternative but

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photons here

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the primary annihilation gives you a

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mess

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of unstable reaction products

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that ultimately are all going to decay

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or mutually annihilate

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um the now if a single antiproton

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annihilates inside a large

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nucleus uh most of the intermediate

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products are strongly

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interacting mesons which are very

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efficient at transferring energy to the

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rest of the nucleus

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so most aside from photons most of the

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energy appears as thermal

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excitation in a nucleus that's literally

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been blown apart

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by the excess energy however if an

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anti-proton

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annihilates an isolated proton the

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uh ultimate products all break down into

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photons and neutrinos and the neutrinos

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end up with the lion's share of the

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energy

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uh for technical reasons that i can get

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into

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later on if anybody is really interested

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now for a reaction drive

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the faster you throw away your reaction

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mass the more efficient your drive is

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the more thrust you get per unit of

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fuel you're using up the ultimate

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reaction drive

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would have an exhaust velocity equal to

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the speed of light

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now since uh which essentially amounts

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to turning your fuel mass into radiation

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and beaming it out the back um

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you might think that you can do that

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with antimatter since it annihilates

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matter completely into energy except

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that

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the aforementioned neutrino problem the

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neutrinos fly off in all directions

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equally

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you can't direct them you can't

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manipulate them

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so much of the energy is lost in terms

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of neutrinos

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that a a rich mix antimatter rocket

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but that assumes you're just burning the

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matter antimatter mix in a reaction

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chamber

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the trick is to pre-accelerate

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the particles you're going to annihilate

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uh

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as in a particle accelerator on earth

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you accelerate both the proton and the

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antiproton to high speed

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but in the same direction not ramming

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them into each other the way we do for

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experiments

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they annihilate in at high speed

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the reaction products inherit that

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center of mass motion and then

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you put in a retrieval stage the stuff

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that you can interact with

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you capture reprocess the energy

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use it to power the acceleration for the

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next particle pair

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meanwhile the neutrinos escape

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all of the momentum that has been put

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into them by the pre-acceleration is

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just

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carried out of the chamber and you get a

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net thrust

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uh i'm going to skip quickly over

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the math here it we can refer to it in

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question

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and answer if people really want um

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but this graphic illustrates

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the drive attributes

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in a perhaps somewhat more accessible

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way

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down here at the bottom i've

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plotted the fraction of retrievable

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energy the

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amount of annihilation energy that can

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be captured and used

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and that actually depends on how big

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your engine

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is and how much free path you have for

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intermediate reaction products to

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decay if something is still a pion of

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some sort

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you can intercept it and use it it will

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decay naturally into

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neutrinos and photons and

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that that's that's where those neutrinos

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come from it's a process that takes

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time um

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and requires a certain amount of free

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path to be completed

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um now fortunately the math on the

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previous page

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indicates that the higher the mass

202
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retention

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that is the fewer neutrino decays you

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allow

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the higher your effective exhaust

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velocity the amount of thrust

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you get per unit of fuel um

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that this is a good thing because that

209
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means that the smaller your engine the

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more powerful and efficient it can be

211
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um just for comparison a

212
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a lean mix antimatter rocket where

213
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you're

214
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doing simple uh a burning like effect

215
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and have perhaps five percent antimatter

216
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would have about this thrust to mass

217
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ratio

218
00:08:57,829 --> 00:08:56,720
an ideal fusion rocket would be down

219
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here

220
00:09:02,150 --> 00:09:00,080
an ideal fission rocket would be down

221
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here and the chemical rockets that we're

222
00:09:05,350 --> 00:09:03,120
actually building

223
00:09:07,030 --> 00:09:05,360
nowadays would be so far down into the

224
00:09:11,670 --> 00:09:07,040
corner that there's no room for the

225
00:09:17,110 --> 00:09:14,550
now what that means in terms of the

226
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performance of such a drive system

227
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if oh sorry i

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overshot this shaded area

229
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here shows the approximate

230
00:09:33,110 --> 00:09:31,440
regime for an engine of reasonable size

231
00:09:34,870 --> 00:09:33,120
a few meters across

232
00:09:37,590 --> 00:09:34,880
and you can see that our effective

233
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exhaust velocity is indeed very close

234
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to the ultimate possible limit uh

235
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a vehicle with a a drive of this type

236
00:09:50,470 --> 00:09:47,760
if it made a constant 1g thrust trip

237
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from the moon to the earth it would use

238
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up

239
00:09:55,430 --> 00:09:54,480
0.42 kilograms of fuel mass for each

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metric ton

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of vehicle mass that's about one pound