The Spaceship Propulsion Compendium

Today’s episode, the Spaceship Propulsion
Compendium, is going to be a long one, sinceI am going to try to touch at least briefly
on every system including some of the moreunlikely ones. I will leave out any that are just not grounded
in science at all, though if I skip one donot assume that means I am including it in
that category. Also some we have covered in more detail in
other episodes so for those I will keep itbrief and mostly just refer you to those episodes. For those of you new to the channel, if my
speech impediment is giving you problems Iencourage you to turn on the closed captions,
it takes most folks a little bit of time toadjust to it, though by the end of this video
you probably will be as again this will bea long one. With that in mind you also might want to grab
a snack and a drink. I also want to add that this topic was selected
from those submitted by the channels patronsover at Patreon and is the first of at least
three we will do this way. I only committed to doing three this way but
it was a lot of fun working with the firstwinner, Drew McTygue, who selected the topic
for this episode, so I am considering makingthis a regular thing. The goal today is not to discuss basic rocket
science or review the history of spacecraft,and our interest in existing propulsion methods
already in regular use is minimal, but rocketsmade spaceships possible for one key reason
that separates them from two other methods,they provide fast thrust to the ship, but
at the cost of devoting virtually all theship’s takeoff mass to fuel. This is because rockets do not have a very
high specific impulse. Specific Impulse, often called effective exhaust
velocity, is the total change to momentum,or speed, delivered to a ship per unit of
propellant mass used. A rocket can deliver virtually all of that
in mere seconds or minutes, making it greatfor clawing your way up through an atmosphere
and gravity well. Unfortunately it means that around 90% of
a ship’s take off mass is rocket fuel, justto get it a couple hundred miles up into space. Alternatively your car can take you a couple
hundred miles off just part of a tank of gas,and a one ton vehicle usually only has 10-20
gallons of gas, or about 60 to 120 poundsor 30 to 60 kilograms more or less. Cars take you hundreds of miles while using
less than 10% of their mass for fuel, rocketsoften do not get to use even 10% of their
mass for payload. If they had a higher specific impulse, or
power to mass ratio, we could carry up waymore. Double your effective exhaust velocity and
a rocket that originally weighed, say 1000tons, 90% fuel and 10% for the rest, suddenly
becomes one that is only 70% fuel and 30%for the rest. If you quadrupled that exhaust velocity your
ship that weighed a thousand tons at launchwould now not be 90% fuel but less than half
fuel and more than half for the ship and itscargo. That is important for spaceships because you
always want your highest specific impulse,or effective exhaust velocity, but most alternatives
we have now that can go higher have to provideit at so slow a pace your ship could never
take off, which does not mean you could notuse it once you got up into space to go further. But our ideal space ship drive would have
a very high exhaust velocity and also be ableto deliver all that thrust quite quickly. We tend to use rocket science as synonymous
with very hard things, like brain surgery,“This isn’t rocket science or brain surgery”
or as one of my sergeants used to say “Thisisn’t rocket surgery” but of course today
we are doing rocket science, and I want toemphasize it isn’t as bad as all that. The basic equation is simple and the really
hard part is calculating all the transferorbits and performance changes of specific
fuel and rockets, we will not be looking atthose today and indeed there are lots of nice
online calculators you can use to do the gruntwork for you. So that was about the only math I plan to
bring up and you do not need to have followedit to follow the basic principle. Some of the systems we will be looking at
today provide way higher exhaust velocitiesbut take longer to do it, others provide higher
velocities and just as fast as a chemicalrocket. Now I have been asked a lot to cover the EM
drive or EmDrive many time recently so I willget to that at the end so I can give it a
little more time but I want warn people inadvance that I am not going to be pronouncing
it a working or non-working system, I am justgoing to be filling in some explanation of
the terms and concepts involved so folks knowwhat all this Q-cavity this and reactionless
drive that stuff is talking about. This is a broad survey of mechanisms for space
propulsion, some of which we have alreadycovered in more detail in other episodes,
not a focused in look at all of them let alonea declaration of which is best or impossible. It is also worth mentioning that a spaceship
does not have to have a single drive, it mightemploy multiple types, in particular it might
use different methods to take off or land. We have discussed launch assist options like
Space Elevators, Orbital Rings, Sky Hooks,Mass Driver, Launch Loops, and Space Fountains
way back at the beginning of the megastructuresseries. We have not discussed landing and braking
mechanisms much so I will give a quick overviewof those in a minute. If you want to know more about those launch
assist mechanisms you can go back and checkout those episodes but in summary form, rockets
use a lot of fuel, and they use almost allof it getting out of our atmosphere. Getting a team of astronauts to Mars and back
home to us uses a lot of fuel and most ofthat gets used up in the first few minutes
getting all that into orbit. Fuel is also expensive, so anything that lets
us get things into orbit with less fuel andenergy, or let’s use do the same for ships
leaving anywhere, is obviously quite handy. Of course once you get to your destination
you have to slow down too. A problem not helped by both how fast you
are going while making the journey and thatas you approach the target, if it is massive,
you will start picking up speed from its gravity. Good timing can arrange to help reduce your
relative speed but you will always arrivewith an awful lot of it. For Earth that is not too big a deal. Earth has a lot of gravity but it also has
a lot of atmosphere, so we can brake our speedoff the air, unsurprisingly called aerobraking. What is a big problem for leaving Earth, getting
through all that air, is quite handy for gettingback down to Earth. If you have a lot of speed, or the place has
a thin atmosphere, you can make multiple wideelliptical orbits, passing through the upper
atmosphere repeatedly, until you slow enough. Even on places without much air this sort
of trick can work, as can more conventionalconcept like parachutes or hybrids of them
like Ballute, a mix of a balloon and parachute. Of course you can also use balloons like airbags,
as we did when Pathfinder landed on Mars. Trying to slow down after interstellar voyages
at relativistic speeds can also be done usingequivalents of aerobraking, in theory you
can loop around a solar system using the dustin space and solar wind to slow down. Space is not a vacuum, even in the intergalactic
void, but solar systems are much less a vacuumthe interstellar space which is in turn less
than intergalactic space. It’s not much but it would help you slow
down somewhat without using as much fuel. And of course you need to slow down before
reaching your destination or you will smashinto it. Though lithobraking, ramming into something
at high speed to stop, is also a method oflanding if your ship is sturdy enough. Generally to save fuel and mass you can always
hit with some speed and anything that savesfuel and mass is worth doing, assuming you
do not overdo it and turn yourself into apancake. Saving on board fuel takes us onto our next
subject which is reactionless and quasi-reactionlessdrive. Now you will often hear folks say a reactionless
drive is impossible but this is an oversimplificationand an incorrect one unless you are careful
with your definition. As mentioned, rockets work by spitting matter
out in one direction and shoving the shipin the other, conserving momentum in the process. Many of the other systems we will look at
work the same way, and many others are doingit by hiding the matter that is going in the
opposite direction. For instance when I brake using the air during
re-entry, momentum is all being conservedbut we do not notice it since all that air
goes flying away and eventually settles inas heat, with the entire planet being shoved
just a little bit. If you jump up in the air the planet actually
does go the other direction, it is just thatthe planet out masses you by around a 100
billion trillion, so even though you addedjust as much momentum to it when you jumped
up as it did to you, you move up a couplefeet and it in turn moves distances that would
make an atom look large. You also do not have to lose your reaction
mass in all cases, same as you don’t whenjumping in the air. If I am standing on ice and bounce a basketball
off a wall and catch it, I will be shovedthe other way by tossing it then shoved again
when it bounces back and I catch it. You can use tricks like this as a launch assist
mechanism when you are near something to pushthings off of, and that would include laser
beams. Light has momentum and kinetic energy, indeed
that is essentially all it has. So bouncing stuff back and forth, be it basketballs
or photons, is an example of a system essentiallywithout propellants, or at least a propellant
you can reuse, but you can only get so manybounces before it is not practical anymore
and it still costs energy. But we also have the notion of propellants
that just are not internal. I mentioned earlier that one of the problems
with rockets is that you need more and morefuel to get to higher speeds because you have
to accelerate not just the ship but the fuelyou will be using to accelerate more with
later and the fuel you will use to slow down. That is core problem of any system with an
internal propellant. If you are pushing something with a laser
generated elsewhere for instance, you do nothave to pay all that extra energy to push
on board fuel up to speed too. I will discuss this a bit more when we get
to photons rockets. Hybrids of this, where you are carrying a
propellant but the energy is coming from outside,like a ship that has solar panels it uses
to heat up propellant to plasma temperatures,lets you get a lot more thrust from the same
mass. This is the basic concept to a lot of the
new propulsion concepts we will look at andthe big problem is that external sources like
this tend to mean you can get to a higherspeed, which is great, but that it takes a
long time, which means it is no good for takeoffor landing. Ion drives, electrodynamic tethers, or electric
propulsion just does not give you the thrustyou need to climb out of a steep gravity well
like a planet particularly when you need toclaw your way through several kilometers of
air. This is the exact opposite of various nuclear
powered drives which can often give you allthe thrust you need you just do not want to
use them in your own atmosphere. We spent a lot of time in the Interstellar
Colonization video talking about Project Orionand Daedelus, which basically operate by propelling
a ship by blowing up nukes behind it. That’s great in deep space but not for taking
off from Earth. That is not the only nuclear option though. First you can just use it to power the electrical
propulsion drives we will get to momentarily,but you can also use what is called a Nuclear
Thermal Rocket, backwards of a ThermonuclearBomb. These come in a lot of variations and are
devices we have actually built and tested,and essentially you have a fission reactor
that you are cooling with some substance,usually liquid hydrogen, then venting the
hot hydrogen out the back. Thermal Rockets are themselves, nuclear or
not, are a fairly classic type of propulsion. You externally heat some gas rather than combusting
it, or in the case of a cold gas thrusterare just letting something warm up and shift
from being a solid or liquid into a gas, nodifferent from putting dry ice in a bottle. In a nuclear thermal rocket you are just letting
fission do the heating. They are decently more efficient than chemical
rockets but usually seen as not enough tojustify the additional hazards and risks. That is debatable but Nuclear has bad Public
Relations issues and a Nuclear thermal rocketsare not the safest device in the world. Same issue for Nuclear Electric propulsion,
and that is just where nuclear is the powersource. Electric propulsion is neither new as a concept
or a technology. The option was kicked around by Robert Goddard
over a century ago. They tend to offer a nice slow thrust that
is good for stationkeeping and a lot of Russiansatellites use this, and it is the basis for
concepts like the ion drive. One alternative before we get to ion drives
though is electrodynamic tethering. Way back in the Skyhooks episode I mentioned
this in comments, annotations, and FAQ asa way to re-generate momentum and altitude
on skyhooks but I skipped including it inthe episode because I was trying for shorter
episodes then and it still holds the recordfor shortest video on the channel. It is pretty novel concept though. Objects with powerful magnetic fields, like
our planet, can be pushed off of, and whilethis is not a good approach for take off vehicles
it works just fine for things in orbit wherethey just need a little thrust here and there
for station keeping. Lots of thrust is good but often we just want
small amounts that use little or no propellant. Which brings us to ion thrusters. These actually come in a lot of types but
the two most well-known are HET, the HallEffect Thruster, and VASIMR, the Variable
Specific Impulse Magnetoplasma Rocket, andwe will focus on those two. But in a nutshell you are taking power, whether
it is obtained from solar or nuclear powersources, and using that to speed up ions and
shoot them out as your propellant. These are almost always very slow systems
in terms of their acceleration so you woulduse them on things already in orbit, not to
get up in orbit. They get up to a higher speed than a chemical
rocket but take way longer to do it. Let us start with the Hall Effect Thruster. The Hall Effect was discovered by Edwin Hall
of John Hopkins University way back in 1879before we even knew what an electron was,
so it is old tech and designs for using itfor spacecraft propulsion go back to the early
days of the Space race, but the designs wereso inefficient it mostly got shelved. Now in a nutshell a Hall Effect Thruster uses
a magnetic field to accelerate plasma up tomuch higher exhaust velocities than chemical
rockets produces. It just does this as a thin trickle for days
or months instead of seconds or minutes likea rocket thruster. No good for launch but great for interplanetary
work. The preferred fuel is xenon, which is fairly
abundant on Mars, and which we usually geton Earth, or Mars, by distilling it out of
the atmosphere. Xenon is a good fuel because it has a high
atomic weight, about 130 times hydrogen’s,and a low ionizing potential, meaning it is
easy to strip an electron off so it will havea charge and respond to the electric field. There’s other things you can use but Xenon
has numerous advantages. The ionization is achieved by slamming electrons
off the Xenon so it knocks free an electron. VASIMR, the Variable Specific Impulse Magnetoplasma
Rocket, uses radio waves to ionize its propellantand to heat it too. Proposed by Franklin Chang Díaz is 1977,
this system does not use an anode which isgood because anodes tend to corrode quickly
during use, a problem with many similar typesof ion thrusters. It heats the propellant by radio waves, usually
Xenon again though most testing is done withArgon because it is cheaper. In a nutshell VASIMR works off concepts developed
for nuclear fusion and it heats its plasmato around a million kelvin, and it can launch
those particles at speeds of up to 50 km/s,faster than other ion thrust systems. Unfortunately it also builds up a lot of heat. You can also vary the specific impulse it
gives off which is handy. VASIMR is a very attractive system but is
not without its problems, and Robert Zubrinof the Mars Society has been strongly critical
of the system on several points, and one ispower consumption. With both systems, or any of the other variants
essentially running on electricity, the questionis always where you get your power supply. Which mostly comes down to how do you squeeze
the most energy out of the least mass. This usually excludes chemical fuels because
we could just set them on fire like a classicrocket, and also batteries since we have yet
to develop one that can push out as much energyper unit mass as chemical fuels. This leaves us solar power or nuclear power. Ideally a nice compact fusion reactor would
be great, and we have talked about fusiona lot in previous episodes, but we do not
have that yet. So the question is, what is better, solar
or nuclear?The answer to this is not as obvious as it
might sound like. In space the sun is always shining, there
is no night or clouds. Nuclear reactors produce huge amounts of power
from tiny amounts of fuel, around a milliontimes what chemical fuels release, but they
tend to be massive when you include all theequipment and shielding. For a ground based reactor we do not care
about mass, so they are quite massive, butyou could possibly get reactors potentially
generating around a kilowatt per kilogramof reactor, maybe more. In practice, as Zubrin pointed out, the largest
reactor ever put in space only produced about10 watts per kilogram. Solar power on the other hand, in our general
region of the sun, can do a few hundred wattsper kilogram with the newest systems. Of course they are also more exposed to damage
in space from micro-meteors since they arerather large and fragile, while a fission
reactor is mostly shielding already. Both of these technologies have tons of rooms
for improvement and it will be interestingto see who wins the race on power to mass
ratio. If and when fusion gets made practical it
would probably replace both, but we couldeasily see both win, after all solar gets
rather ineffective the deeper you go out inspace away from the sun, so you might see
fission powered ion drives out there and solarnearer in. Ion Drives are very promising technology though
especially as we improve our power to massratio of both solar and nuclear systems. Now before we get to the EM Drive, I wanted
to cover some other hypothetical high-techdrive systems. Quite a few of these we have talked about
before in greater depth, for instance we dida whole video on the Alcubierre Warp Drive
in the FTL, Faster Than Light, series. Similarly we did a video on using artificial
black holes to power starships. So I will just refer you to those if you are
interested. In the episode on black hole powered starships
I mentioned that they give similar performanceto antimatter but are less prone to explode. Antimatter is often regarded as the ultimate
rocket fuel, though of course it is actuallya bipropellant fuel, matter and antimatter. Antimatter, when combined with normal matter,
turns both of them into raw energy, and youcould source your normal matter from the containment
system for the antimatter or by sucking inrandom space gas. As fuels go, when you have to carry your fuel
with you, nothing beats antimatter. The issues with antimatter are two-fold, production
and containment. It currently takes huge amounts of energy
to produce antimatter, orders of magnitudemore than it releases, and storing it is a
tricky proposition usually assumed to involvekeeping it in a magnetic bottle. Obviously you cannot keep it in a normal bottle
or it would explode when it touched the matterin the bottle. If you had a way to produce antimatter for
similar amounts of energy to what it released,and if you could safely store it, then this
is the ultimate rocket fuel and allows speedsgenuinely close to the speed of light. Other than production and containment it is
the same as any other rocket fuel too, thoughit is arguably a photon rocket since it is
releasing its energy as photons. A photon rocket, sometimes jokingly calleda flashlight drive, is where you are just
emitting photons to push you away. If you drifted away from your spaceship you
could use your flashlight to push you backtoward it, same as you could vent some air
from your tanks to push you back too. The problem is it take a lot of energy to
do this and a battery does not have much. Batteries do not store as many joules of energy
in them as an equal weight of gasoline forinstance or other rocket fuels. The other problem is the produce virtually
no thrust at all. A flashlight, say a 30 watt flashlight, and
one that also radiates all that light in thesame direction, produces a thrust of its power
divided by the speed of light. Conveniently that would be 30 Watts divided
by 300 Million meters per second, or one tenten millionth of newton. 10^-7 newtons or 100 nano newtons or . 1 micronewtons. Now if you and your spacesuit have a combined
mass of 100 kilograms, f = ma, force = masstimes acceleration, or acceleration equals
force divided by mass. 10^-7 divided by 100
equals 10^-9 m/s² or a nano-meter per secondsecond. Not very fast. If I had been drifting
away at a meter per second it would take mea billion seconds, or a few decades to bring
myself to a relative stop, all the while I’vebeen drifting further away. Obviously my battery
and oxygen ran out way before that. But there are two tricks of note for this.
First, I don’t need any fuel on board,I can just have solar panels drinking in sunlight.
Let say I had nice thin efficient solar panelof a couple square meters giving me 3000 watts
of power out of my bigger flashlight, andthe whole thing only weighed a kilogram. One
hundred times the power as our last examplepushing one hundredth of the mass, that gives
me 10,000 times the acceleration. Now thatis not as bad. After a few decades you are
not going one meter per second but 10 kilometersper second.
Some of you might be saying now, “Hey, whyeven bother with solar panels and a flashlight,
why not just use a mirror? You could makethat even thinner and not even need the flashlight?”
and that is true, except it’s even bettersince when light hits and reflects off something
you get double the effect. So a very thinmirror being hit by sunlight has a much higher
acceleration than the flashlight since youcan use all that mass as just simple thin
mirrors, getting more light, and getting doublethe push from it. You can also bounce that
light at an angle to produce thrust in differentdirections.
But that’s not the end of it, because wecould bounce more than once. Sort of like
our earlier example where we bounced a basketballoff the wall then caught it and threw it again,
just with light instead. If I have a nicereflective surface, and a laser with a reflective
surface around it to, I can shine that laseron the first mirror which bounces it back
to the mirror around the laser which bouncesit back to the first mirror and so on.
A spaceship and some space station bouncinga laser back and forth between them could
get that ship up to a pretty good speed ifyou can keep that beam contained, which of
course gets harder and harder the more timesit bounces and the further apart they get
from scattering and diffusion, plus each bouncetakes longer.
But such a thing as a launch assist systemhas some possibilities, and we explored laser
and light propulsion in the Interstellar Colonizationand Nicoll-Dyson Beam episodes in more detail.
I discussed there the notion of a laser highwaybetween solar systems where you have many
stations along the way using fusion to powerthemselves and bouncing laser off ships as
they passed by, possibly back and forth afew times if you can aim and focus the reflected
laser well enough. Now if we have the ability to alter either
what the physical constants are, like gravity,or make them not work symmetrically, say gravity
that emitted like a cone not a sphere, otheroptions become available. Imagine for the
moment that a large and massive object didnot emit gravity in all direction but just
in one direction. Something like a gravityflashlight or laser. We have no idea how to
do such things yet and maybe never will, butit may be possible in the future.
Certain hypothetical materials, like negativematter, a type of exotic matter we have discussed
before in the Faster Than Light Series, couldlet us achieve such effects or equivalent
ones. These sort of ideas are used for conceptslike the Diametric Drive or Pitch or Bias
Drives. These are totally hypothetical craftrelying on science we do not have yet but
I feel they deserve a mention. Lastly we have the idea of picking up fuel
in route, gathering up either space gas ordark matter to use as fuel. This is the basic
idea of the Bussard Ramjet, which we discussedin the Interstellar Colonization episode,
and for how to refuel a black hole poweringa spaceship, which we discussed in Black Hole
Spaceships. Using Dark Matter as a potentialfuel is something we looked at in the Dark
Matter episode and has to be classified astotally hypothetical since we still do not
know the properties of Dark Matter or anyway to manipulate it, but we discussed it
more in that episode if you are curious. Okay, on to the EM Drive at last. I saved
this one till the end so we could spend abit more time on it since it is a big news
item with an awful lot of confusing and oftencontradictory reporting. It hit the news again
recently when someone said that NASA wouldbe releasing a peer-reviewed paper on it.
At the time of this episode that paper hasnot been confirmed to be released, let alone
released, but the assumption it was beingreleased is what rekindled interest.
Now the EM drive, or just EmDrive, is oftencalled a radio frequency, or RF, resonant
cavity thruster. Its sibling device, the CannaeDrive or Q-Drive works off the same concept.
This is a type of electromagnetic thrusterin which electromagnetic radiation, photons,
are confined to a microwave cavity, and providesthrust to the cavity in a particular direction
as the radiation reflects within the cavity. Now what is a Microwave cavity? Well basically
a box with mirrors inside that reflect thatfrequency of radiation, in this case microwaves.
You probably have one in your kitchen, a microwaveoven is a simple microwave cavity.
There are two special notes about this though. First, a terminology one. Whenever we discuss
cavities you will hear people refer to itsQ-Factor, and irritatingly most do not bother
explaining what this mundane thing is so manyfolks assume it is some weird physics thingy.
A Q-Factor is just short for Quality Factor,and it basically measures how good the cavity
is at keeping the waves bouncing around insideit rather than dissipating as heat.
It isn’t quite as simple as just sayingthat a perfectly reflective mirror would have
infinite Q, but for basic conceptual purposesit amounts to how good a reflector the cavity
is. That’s important since as I mentionedback when we were discussing reflecting lasers
repeatedly, every time you can get it to bounceyou get more thrust imparted. So higher Q
is good, it is also very hard to get froma practical standpoint when you are trying
to dump tons of power into a cavity. Somethingwith really high Q would make an excellent
battery for instance. You could just keepdumping more and more microwaves in and lose
very little of it to heat dissipation. Now the other difference is that these kind
of cavities are usually cylinders, for theEmDrive though it is a tapered cylinder, wider
on one side than the other, and the basicnotion is that the wider end will get more
force exerted on it, generating a net thrust. Now in principle this device produces thrust,
but it does not seem to have any sort of propellant,which would make it violate conservation of
momentum. Remember even our laser or solarsail drives use photons as their propellant.
The EM drive is not supposed to be emittingany, just bouncing them around inside. So
this drive got dismissed as total nonsenseby most until one got built by NASA and seemed
to produce some thrust. Now it wasn’t much thrust, so little it
might even be noise, and actually less thanyou would get by shining a flashlight using
the same power. Indeed there is a concernthat it is just asymmetrically emitting radiation,
again like a flashlight, since it is hardlya nice symmetric sphere.
At this point many would say “Okay, so evenif it does produce thrust, it is less than
a flashlight or laser, so what good is it?”. Fair point, BUT, it would still be interesting
until we knew how it was producing any thrustand the notion is that this device does not
necessarily scale its thrust linear to itspower. By which I mean, if we double the power
to it we would expect to get more than doublethe thrust.
So you would next say, “Why have we notjust done that then, this experiment was only
using around a kilowatt of power, why notthrow in 10 kilowatts, or a 100, and see what
happens?”The simple answer is that high Q-factor cavities
than can also handle tons of power withoutmelting are very, very hard to make. Which
obviously also means very expensive. Now a few more notes. First, the EmDrive is
not the quite the same as the Cannae Drive,but the two get used synonymously a lot so
you should probably treat them that way whenreading about either one, because folks use
them interchangeably. Second, it is in noway a warp drive. That was just bad reporting.
Eagleworks is NASA’s department for lookingat novel and sometimes fringe propulsion systems,
headed up by Sonny White, so they are alwayslooking at various strange systems and Sonny
White also examined the Alcubierre Warp Drivearound then and lots of bad reporting jumbled
them together. If you see an article talkingabout EmDrive and warp drive, you can pretty
much just skip it. Either the author is usinga clickbait title or they didn’t do their
research, so either way it probably is notworth your time.
I get asked for my opinion on the EmDrivea lot and personally I do not expect it to
actually work. Or if it does then the thrustwill turn out to be something quirky where
it is being provided by photons leaving thedrive but interfering with each other so we
have problems detecting them or bouncing offQuantum Vacuum Plasma, or a Q-Thruster, where
in this case the Q is for Quantum not Quality. Sonny White tossed that notion out there as
an option but the idea of Virtual Plasma,as a type of Virtual particles which we have
discussed before, is not too popular withtheoretical physicist at the moment.
Fundamentally we are at the wait and see stage,nobody has gone and proved the EmDrive works,
that is just sensationalist journalism, butnobody has successfully killed it yet either.
I would not suggest holding your breath itwill work but I would say it is still on the
table for now. That is true of a lot of the systems we have
discussed today, and hopefully at least oneof those will turn out to be both possible
and practical so we can replace chemical rockets. I think we are justified in being optimistic
and putting some faith in human ingenuity,but we also always want to keep our exuberance
dampened and scientific. As I’ve said before, there is a big difference
between proper skepticism and naysaying, aswell as just trusting to science as a magic
wand. It can often seem like propulsion technologyis proceeding at a snail’s pace and sensationalist
journalism constantly reporting every newtheory like it was proven fact can make a
person pretty jaded, but we are making goodand constant progress.
For my part I am very optimistic about thatprogress, if properly skeptical too, and while
we could only cover the basics here you shouldhave a good place to continue your own research
into these. I’ll be placing several linksin the episode’s description to good places
like Project Rho to either follow up on theseor get more specific data, but this is where
we end for today. Some quick announcements. First I wanted to
thank Drew McTygue, he was the first winnerof our Patreon subject selection and chose
today’s topic. We spent a lot of time onthe phone discussing what to cover and what
to bypass for time constraints and we workedon the script together which was a lot of
fun, and I’m looking forward to future collaborationswith folks on such topics.
Next, we have our second winner for a topic. That topic is going to be Star Lifting, and
that winner was Bill Mains, so congratulationsto Bill and that was an excellent topic pick
and one I have been considering covering fora while.
Star lifting is term given to various hypotheticalprocesses for lifting matter of stars, as
the name implies. This has quite a few possibilitiesand uses, the two most obvious being that
99% of the matter in our solar system is inour star, so it is create source for matter,
and secondly, that you can use this processto extend the lifetime of a star. We will
look at that and some other awesome thingsyou can do with star lifting when that episode
comes out on October 6th, 2016. That will be after we take a look at Dark
Energy next week, and that will be followedby a look at Cryptocurrency and BlockChain,
then get followed by a look at the KardashevScale on the 20th, that topic was selected
by a poll over on our new Facebook group,Science & Futurism with Isaac Arthur which
Drew is now a moderator for too. I want tothank everyone who came over and joined that
last week and everyone who volunteered tomoderate and administrate it, and we will
be selecting a lot of our topics by pollsconducted over there and topics selected there
from now on, as it is a better place to discussthe ideas.
This week though, while I’d encourage youto join the Facebook group, we are also launching
the identically titled Sub-Reddit Science& Futurism with Isaac Arthur so I will be
over there after this episode comes out answeringquestions and I hope you will join us on both.
We will have one more Patreon Topic selectionin a few more weeks so it is not too late
to join and submit topic suggestions overthere, and indeed I am considering doing it
more in the future. You can opt to submitanonymously if you do not want to me saying
who you were during the videos but I preferto be able to say who’s idea it was and
to be able to sit down on the phone and discussthe idea with the person who submitted it,
that won’t affect whether or not the topicgets selected but do let me know if you do
not want your name used, or want a pen nameused, or are not comfortably chatting about
the idea on the phone. That third episodewill probably come out in Early November.
Again, next week we will look at Dark Energy,and clear up some of the confusion about this
mysterious force that seems to be shovingthe Universe apart. Until then you can try
out some of the other episodes on the channelor at the website, IsaacArthur. net, or follow
me on facebook or twitter or reddit, and ifyou enjoyed this episode, make sure to like
it and share it with others. Thanks for joining me today and until next
time, have a great day!

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