June 24, 2015 • 41 mins
What is a solar sail and how does it work? We explain the technology and talk about current and future uses of solar sails.
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Episode Transcript
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Speaker 1 (00:00):
Brought to you by Toyota. Let's go places. Welcome to
Forward Thinking. Hey there, and welcome to Forward Thinking, the
podcast that looks at the future and says, I'm sailing away.
I'm Jonathan Strickland, I'm Lauren Bocan, and I'm Joe McCormick.
(00:20):
And guys, I thought today we could talk about solar sales.
We've mentioned them a few times in past episodes, and
I will probably talk about them in future episodes too.
But the reason why I specifically wanted to bring it
up is because, not too long ago, in the news
we're recording this in June, there was a story about
a crowd funded solar sale projects. So we're gonna talk
(00:43):
about that a little bit later in the episode. But
in order for that conversation to even make sense, we
need to just kind of talk about what these things
are in general and what their purpose is. Now we're
solar sales, the vessels that Sailor Moon and the other
sailor scouts sail I don't know, because Lauren had not
gotten that far into the explanation of what Sailor Moon
(01:06):
is all about for us. Can you help us out here, Lauren,
um I believe they are not, although I'm sure the
magical cats Luna and Artemis are very fine sailors. We
we honestly were having Lauren explained to us what sailor
Moon is all about earlier. So so, yeah, that's just
a peak in the inner working, so forward thinking. But
(01:29):
of course solar sales are not a component of a cartoon.
They are a reality. Yeah. Yeah, it's a propulsion system
that doesn't require fuel. Now, we just recently on this podcast,
talked about a supposed propulsion system that doesn't require fuel
in our podcast on the M drive and the microwave
(01:50):
oven that makes rockets go, well, yes, supposedly, no, no,
makes a vessel go without the need for rockets, and
the appeal of the M drive as it is supposed
to work. Now, we ended that podcast with a lot
of hesitation about whether something like this could actually work.
But if you take the M drive proponents at their word,
what they're saying happens is they've got a method for
(02:13):
making a spaceship go through space without a chemical reaction,
shooting stuff out the back of it without any kind
of propellent. Yeah yeah. And and the reason why that's important,
obviously is that you can't carry an infinite amount of
fuel on your spacecraft, right you. You are limited by
the volume of whatever vessel you have, and the reality
(02:35):
that fuel is a three dimensional thing that you have
to lug around, right yeah, And that it adds weight
to the spacecraft, which means the more weight you add,
the more fuel you need in order to escape the
gravitational poll of the Earth I mean. And then once
you're out into space, then you need more fuel to
get to where you're going to accelerate to whatever the
top speed is. You can only accelerate so much with fuel.
(02:58):
Of course, if you had some sort of system that
could gather fuel while you are sailing through space, then
that would help solve it. And there are ideas like
that you can travel along through space picking up tiny
particles and ions and and heaving those out the back
of a spacecraft. There's not much mass in those, so
(03:19):
you don't get a lot of acceleration, but slowly over
time you can build up speed with the method like that.
And another method similar is solar sales, and that it's
again one something that has a steady but but low acceleration,
so you're you're consistently accelerating at least until you get
to really kind of the top speed of whatever mass
(03:41):
you are you are using. Uh, but you are accelerating
steadily up to that point. It's just that it's a
low level of acceleration. And the reason why we call
them solar sales is that they're very similar, at least
in concept, to the sales that we use here on
Earth to propel things like oats and ships, right, which
are I suppose technically fueled by the sun because the
(04:04):
Sun heats the Earth which makes the wind blow. That's true. Yeah,
if we go far enough back, it is. It is
kind of a solar powered means of propulsion. But surely
you're not suggesting that there is wind in space. Well,
it's similar into wind in space. We're specifically talking about
photons in the case of solar sales. But before I
(04:25):
get too far, I do want to make one distinction
clear for any of our sailing friends out there. It's
more a solar sales more like a an Earth sail
if you were sailing directly downwind. Uh. This is an
important distinction because sales can actually be used to sail
sort of into the wind, which seems counterintuitive. But it's
(04:46):
because the construction of sales is such that they act
kind of like a airplane wing does, so you can
actually yeah, yeah, Otherwise you could only go in the
same direction that the wind is blowing, which would not
be terribly that would be inconvenient. I've actually always wondered
about that. I have no idea how that works. It's
very much like a like an airplane wing. It's designed
(05:07):
so that the airflow is different across one surface than
the other, and it's it's similar to generating left except
you're generating thrust essentially, So solar sales are more like
if you're sailing directly down wind, you're catching the wind
to push you forward. In this case, a solar sale
is capturing or or is acting as kind of a
(05:28):
surface for photons to bounce off of. And photons, as
we have talked about many times on this show, are
particles of light. Sure, A photon is a a quantum
of light. It's the smallest indivisible unit of light energy
that transfers the electromagnetic force throughout the universe. So yeah,
(05:48):
the Sun is of course putting out lots of photons
all the time, shining them out into the universe. That
shining is of course electromagnetic radiation, and it turns out
you can use that shine, meaning the sunshine, the electromagnetic
radiation coming off of the Sun to push a sail
in the same way the wind would push a sail
on Earth. But that's kind of weird because the wind
(06:12):
that pushes a sail on Earth is made up of
particles of air. It's gas, it's massive particles, and it's
very easy to see how that imparts a force, how
that gives momentum to the craft that's attached to the sail, right,
because yet again the air that we are breathing is
not open empty space. It's soup. Right. But if you
(06:35):
remember from like a high school physics class, what is momentum,
There's that equation P equals m v, so that will
tell you that momentum is mass times velocity. So you
take the you know, the mass of the wind hitting
the sail and how fast it's hitting the sail on
that vector. That's important. And I was about I was
(06:56):
about to throw in the direction, but you you covered
it exactly. Velocity is is a is a vector, and
that you need both a magnitude in a direction for
that particular measurement. But yes, exactly. You take that mass,
you take the velocity, you multiply them together, you get
the momentum. This is sort of a way of describing
the movement energy of UH an object in motion and
(07:21):
with massive objects. That makes it pretty simple to understand.
You know. You think, oh, if I'm running at a
speed of eight miles per hour, I have a certain
amount of momentum. It's going to take a certain amount
of energy to stop me because of the the energy
that I that that represents. If a semitruck is traveling
(07:42):
at eight miles per hour, it's going to need more
energy to stop it because it is a much more
massive object, all right, And in the stopping of it,
it's going to transfer some of that momentum to the
object of stopping. Yeah. So if you if you have
something that is has less uh potential force there, then
you probably aren't going to stop this in my truck,
(08:02):
but you will definitely alter the stopping whatever it was,
like a wall or fence. Yeah. But photons, the makeup
of the sunshine don't have any mass. They don't have
a rest mass or variant mass, right, Yeah, so this
makes it a little tricky because you would think, well,
we just talked about how that that equation is mass
(08:25):
times velocity, So how could a photon that has no
mass transfer momentum, I mean, momentum depends on mass, right, Yeah,
But one way I've seen of explaining this is to
say that momentum isn't really fundamentally mass times velocity. That's
just sort of the Newtonian level shortcut for describing how
(08:45):
things work, and and it makes sense because for most
of us that's i mean, that's the world we live in,
I'm sure in the macro level, or at the macro level.
Rather if we're going to use prepositions correctly, which we are, Uh,
that's completely valid. But photons are are in that strange
little little less than big. Yeah, we're talking quantum level
(09:10):
on there. Yeah. So you could look at this in
terms of quantum mechanics or in terms of relativity. But
either way, what this works out too is that the
energy of a photon sort of plays the role of
mass that we would usually think about in this equation.
And Einstein pointed this out right, there's the famous equation
E equals mc squared. This tells you the relationship between
(09:33):
energy and mass. So a small amount of mass is
equivalent to an enormous amount of energy because you're multiplying
at times the constant of the speed of light squared. Well,
that also means that mass is equal to energy divided
by c squared. You know, you just change around the
the equation there. So that photon, that representation of a
(09:56):
of an amount of energy of light is equivalent to
a certain amount of mass. It's just a very small
amount of mass. But that small amount of mass doesn't
think you know, the fact that it's small doesn't really
matter because of two big things. Really. One is that
in space you don't have gravity to work against. So, uh,
any amount of momentum transferred to the solar sale is
(10:19):
going to have some effect the the solar sale is
going to end. Whatever is attached to it is going
to move in the opposite or or is going to
move in the same direction as the impact. Secondly, it's
not like it's a single photon that's saying the solar sale.
There are lots of photons hitting the solar sale. They're
doing so at the speed of light. Uh, So you
(10:40):
are getting a transfer of momentum in that way. Light
itself can have momentum, as can other types of electromagnetic radiation,
so that's kind of exciting. So each individual photon imparts
only a very slight amount of momentum, but there's enough
of them that you can build up a traveling force
over time, right. And the amount of moment to possessed
(11:00):
by any individual photon is dependent upon that photons wavelength
and frequency. So if you were to take a photons
frequency and its wavelength and multiply them together, the product
would be the speed of light, all right. So in
other words, if you have a longer wavelength of light,
(11:20):
it's going to have a lower frequency. Though those two
have to change, right, because the end product has to
be the speed of light with a photon. If you
know one of these variables, you know the other one, right.
So higher frequencies have shorter wavelengths, and they also have
higher energy levels. So a high frequency, short wavelength photon
has more energy than one that has a lower frequency
(11:42):
but longer wavelength. Uh, that's important as well. And Uh,
there's an astrophysicist that actually, Joe you had had clued
me in on that. I had read some of his
work before, but didn't know him by name and his
explanations of this sort of stuff really made it a
lot easier to understand. Yeah, his name is Ethan Siegel.
(12:03):
He's one of my favorite science bloggers on the internet.
He's on Twitter as at starts with the Bang. He's
really worth reading. And he also, for me, has made
a lot of sort of astrophysics concepts much easier to grasp. Yeah,
and he's also he's also kind of an eccentric guy,
and I dig that. It's pretty awes Yes, he does. Yeah,
(12:24):
like his Twitter handle, he's got horns coming out of
his head and stuff. It's pretty pretty cool. Cool. Yeah,
So now we've we've got up the the physics behind
why solar sales could work as a means of propelling
a spacecraft without using any actual fuel. Uh. Now, to
actually take advantage of it, you have to build your
(12:48):
spacecraft in a very strategic way. You want to minimize
the amount of mass you're using so that the propulsion
from the solar energy is max smized, because the more
massive it is, the more solar energy you're going to
need to you know, it's going to it's going to
accelerate slower and slower, or as the mass increases, the
(13:09):
rate of acceleration is lower, so it takes longer to
accelerate to those incredible speeds. Alright, same principle is if
you have a heavier car, it takes more gas to
move it, right yeah, yeah, very similar to that. But
you also want the largest possible surface on which the
sun can push right yeah. Yeah. It doesn't do you
much good if your solar sale is you know, a
(13:31):
couple of square inches, then it's not going to capture
enough photons for that to really be worthwhile. So you
want a lot of surface area, uh, and not a
lot of mass. So that also means that whatever material
you're using, you want it to be super thin. Uh.
Tends to be reflective, so the photons hit it, they
bounce off, and the momentum is transferred to the solar sale,
which in turn transfers that momentum to the spacecraft itself. Uh. Now,
(13:55):
this acceleration, like we said, is small, but and it
is continuous. So the longer the spacecraft is capturing the
solar energy, the faster it is moving. It's accelerating slowly
over time, but it keeps going until you've reached the
maximum speed that spacecraft can go according to its uh mass,
(14:18):
or you are no longer able to capture a significant
amount of photons to continue accelerating. But either way, at
that point, you're traveling at an incredible, incredible speed and
you're not going to slow down unless you encounter something
that makes you slow down, like an asteroid, yeah, or
a planet or a moon or something that has a
gravitational effect on your spacecraft. Right, or you know those
(14:40):
jerk aliens. I hate the jerk aliens, always clinging onto
stuff much before rotisserie. Oh nice, Okay, so moving on.
Typically this super thin solar sale is only a few
microns thick. So to get an idea of how thin
we're talking about, I you get a plastic bag from
(15:01):
grocery store, you know, your typical thin plastic bag. Those
tend to be twice as thick or more than twice
as thick as the solar sale material. So this is
really thin, delicate stuff. Yeah. That material is typically a
polymer film that's capable of withstanding the high temperature fluctuations
of space because it can be pretty chilly and it
(15:23):
can also be pretty warm, depending on how much radiation
is hitting you at the time. Some researchers have also
investigated using carbon fiber woven to be you know, hundreds
of times thicker than these films would be, but just
as a light due to their structure, their holy holy structure. Ye,
holy as in lots of holes in it. Yes, yes,
(15:44):
you really can't say holy twice without saying it thrice,
holy holy holy, Right, let's hear it again, holy holy
holy structure. Um, that's my high Church of technology talking.
That's fair, thank you, thank you. So if you're wondering
what kind of fantastic speeds were actually talking about, well,
(16:06):
Planetary Society co founder Lou Friedman once told the UK's
Royal Society of Chemistry, and by once, I mean back
in two thousand nine that the contemporary technology should allow
acceleration rates of about point zero zero zero five meters
per second. Well, all right, so what's the miles per hour?
That's point zero one miles per hour. This is the
(16:28):
acceleration rate. Yes, yes, um, I mean, of course, given
a probable size of sail and weight of vehicle that
you would expect to be launching like the kind of
things that they were thinking about in two thousand nine,
which we will get into a little bit later here,
um to to get that up to a sort of
range that's a little bit more understandable. Over the course
(16:49):
of the of a day, that's about a hundred and
sixty kilometers per hour a k A about a hundred
miles per hour, and that means that in a year
it could hit thing like fifty eight thousand kilometers per
hour or thirty six thousand miles per hour, which is
something like three times the speed of our current interplanetary missions.
(17:10):
That's that's now, that's incredible because again, just through the
fact that it is continuously accelerating, it's able to hit
these speeds. And sure it takes a long time to
hit those amazing speeds, but it can and it doesn't
require the use of fuel. That's why it's so attractive. Now,
what would you actually be using these solar sales for,
I mean, what would it be propelling? Obviously, uh, we're
(17:34):
not necessarily talking about manned missions here, where we'd have
people aboard a uh some form of transport and using
solar sales to move. That's a possibility, but it's not
necessarily what they'd be used for. Well, they have very
few moving parts because you really just need to be
able to deploy the solar sale right, unfurl the sail,
(17:57):
and and then you end up there. There needs to
be some means of controlling the the attitude, the the
the position. Yeah, the position of the spacecraft in relation
to whatever source of photons you're talking about. You need
that as well. But apart from that, you're you're pretty
much set. So they're great candidates for reuse. So instead
of having to build a spacecraft for every single mission,
(18:19):
you could have a solar sale craft that could potentially
be used multiple times before ever needing to be replaced.
So they'd make really great delivery or cargo vehicles in
this way, I've seen one of the big ones. One
of the big use cases that has been put forward
is it could be used to deliver cargo and supplies
to Mars. Now, you wouldn't have a solar sales spacecraft
(18:41):
land on Mars. That would not be good for anybody there.
But what you could do is have it fly by
Mars and do essentially a controlled drop of cargo. Or
it could rendezvous with other spacecraft like a space station
that's in orbit around on Mars. You could have a
rendezvous where cargo gets transferred and then the solar sale
(19:05):
is redirected and sent back to Earth. It can be
kind of a taxi vehicle, another another interplanetary uber. It
could be. Yeah, I wouldn't be surprised if we see
an app for that in the next five years. But
the next application would be possibly to create an early
warning system for space weather. Uh. This would be really
(19:26):
useful solar weather happens. I mean you probably are at
least familiar with solar flares. They have the potential to
disrupt electronics here on Earth. If it's a large enough
solar flare, it can cause some surges in things like
power grids, and in fact, it can even cause an
entire blackout of a region if it's powerful enough. There's
(19:48):
also coronal mass ejections, which sometimes but not always a
company solar flares that can cause some problems, uh, and
we're not always aware of them until it's pretty late
in the game. So if we were able to put
spacecraft into different orbits, then we can usually uh achieve
on our own. Then with our other satellites and other probes,
(20:10):
then we could have uh more of a a complete
look at what's going on with the Sun at any
given time, and then if we spot warning signs, we
might be able to prepare ourselves in the event of
a solar flare coronal mass ejection that could potentially cause
havoc here on Earth. It might mean being able to
balance loads or reduce loads on our electrical grids to
(20:35):
reduce the potential damage that could happen. It's really important,
and it's something that a lot of people have been
pushing for for a while, saying, you know, it's just
a matter of time before there's a big solar flare
up that could at least temporarily cause real problems for
us here on Earth or yeah, yeah, I mean the
(20:57):
and these weather patterns happen in cycles. Now, just because
they happened in cycles doesn't mean that every eleven years
we're going to get a massive solar flare that's gonna
wipe out you know, Detroit or something. It's that's not
what it means. But it does mean that they there
are periods of increased activity and then there are periods
of a lull of activity. But this sort of spacecraft,
(21:18):
a solar sales spacecraft that could go into these eccentric
orbits that normally we wouldn't be able to achieve, could
at least give us a heads up when that sort
of thing might happen. You know, what could be even
better is if we made one that was really big,
just big enough to completely block the Sun from the Earth,
and then we'd never have to worry about So you're
(21:40):
taking the Mr. Burns approach. I see, I always liked
something about him. Excellent. So it could also be used
to propel spacecraft through interstellar space, not necessarily carrying humans,
but maybe who knows, by the time we get to
the point where we were seriously talking about in interstellar travel,
(22:00):
it might be one of the more approved of ways
of doing that. UM. But what you would typically do
would you would have your spacecraft do a run near
the Sun so it could get a good boost of
energy and then uh accelerate as it moves outward to
escape the solar system. Uh. Eventually you would get to
(22:22):
a point where you would have fewer photons hit the
solar sale, so you wouldn't really receive the acceleration that
you had when you first passed by the Sun. But
by that point you're already traveling at this insane speed,
so it would be probably one of the more viable
means of propelling a spacecraft outside the Solar System. Uh,
(22:44):
in a you know, reasonable time frame. By reasonable, I'm
still talking a long long time, you know, not necessarily
something like oh, within within a year and a half
will be on the Solar System. That yeah, but but
more reasonable than the generations upon generations that it would
currently take. You get out right doing like little slingshots
around various planets and stuff. Um So, also it might
(23:07):
be used to help protect us against collisions from space rocks,
like like giant asteroids. I've actually read about this method. Yeah.
So the idea is, if you have an asteroid on
a collision course with Earth, you don't necessarily have to
destroy the asteroid to protect the Earth. You just have
to divert its path. Yeah. In fact, destroying the asteroid
(23:30):
might be not as productive in the sense that now
you've got a whole bunch of little asteroids aiming at
Earth instead of a big one. In the words of
some random guy from the movie Independence Day, you risk
turning one dangerous falling rock into many. Yeah. I think
phil Plate has referred to it as as you turn
you turn a slug into a blast of shotgun pellets um,
(23:52):
and and so the idea would be you attach a
solar sale to this, like, well, first you have to
detect it, right, you detect that there is an a
body that is on a potential collision course with Earth,
although hey, having erratic satellites up there might help with
detect and having having the enormous solar sale satellites to
(24:13):
kind of detect that sort of stuff. Plus we've got
really sophisticated uh telescopes these days that can detect stuff
from much further away than we did before. Then what
you would want to do is send up a spacecraft
that could attach itself to the asteroid and deploy a
solar sale and use that that momentum from the photons
(24:36):
to help pull the asteroid off course. And it doesn't
have to be that far, assuming you catch it far
enough away from the Earth, right, Yeah, So the idea
is you'd essentially make the sun word facing side of
the asteroid a huge mirror, and then you'd hope that
over time it gathers enough acceleration away from the Sun
(24:59):
via that huge mirror, the same principle as a solar
sale to make it miss the Earth. But like you
were saying, Jonathan, this would only work if you had
a very long lead time because that acceleration based on
the photon reflection is going to be pretty slow. Right, Yeah,
you need to make sure that you know. The earlier
you are able to deploy this, the better your chances
(25:20):
are of of diverting the pathway so that you no
longer have to worry about a collision. But again, it's
when you think about it, it really does make sense.
Like if I'm standing two feet away from you, uh,
and I have a water a water pistol in my hand,
and then I move my my hand just a little
(25:40):
bit to the left or right, I'm still gonna hit
you because I'm two feet away from you. But let's
say that this water pistol can shoot water across the
football field. First of all, you're not gonna want me
to shoot you from two feet away. But let's say
I'm I'm across the football field from you and I
move my hand that same distance. Because of the distances involved,
obviously the the trajectory, it's gonna totally miss you, you know,
(26:03):
not taking wind into account, which I never do anyway.
So uh yeah, that's the same basic idea from this
potential use case. So let's talk about some solar sale projects,
because this is not science fiction. This is actual technology
that has already been used. Well it's yeah, it's not
even science. Maybe one day it's it's science. A few
(26:25):
years ago. Yeah, yeah, the first one Okay, well the
first one was not supposed to be the first one
if things had worked out properly. But what ended up
being the first solar sale spacecraft that actually worked was
the Chorus Space Probe, which was not choros I K
A R O s uh. So this was in June
(26:48):
of so this was just a few months before another
solar sale test craft was launched by NASA. Uh it
was launched by the Japan Aerospace Exploration Agency or Jackson
and ACARUS is actually an acronym. It's not all capitalized.
It's like some other acronyms that are no longer completely capitalized,
(27:11):
but stands for interplanetary kite craft accelerated by radiation of
the Sun. I wonder how many people had to think
of the like the acronym. Yeah, but it was all
meant to just demonstrate whether or not solar sales could
could really work. Why is the acronym in English as
(27:32):
another excellent question to which I do not have an answer.
I can give you a few more details about the craft,
but I can't tell you what you know why it's
called that? Uh not interested? Sorry, Well for everyone who's
not Joe, tell me about the craft, all right. Uh So,
(27:52):
the sale itself was forty six ft wide, which is
fourteen meters, and uh Acorus had l c D p
annals on the edges of the sail. And you might
wonder why why would a solar sale have l c
D panels. And it was all to control their reflectivity
of the sales because that was how the spacecraft could
(28:12):
adjust its attitude in space. Not like it had a
bad attitude. I don't. I don't mean attitude in that
sense like mood. I'm talking about its position relative to
the sun. Oh okay, so this should be kind of
like the boom on a sail on a sailboat, where
you can sort of like adjust its attitude towards the wind. Right.
So in this case, you're adjusting the reflectivity of the sale,
(28:33):
or at least the edges of the sail, and that
is what would cause the photons to either transfer more
or less momentum to those edges, and that would adjust
the attitude of the spacecraft, which I thought was a
very elegant means of a of of creating a control system.
Um so that was pretty cool. Now. The second one
(28:55):
was the Nano Sale D two, and that too is important.
Uh So this was one that was launched by NASA.
You see, they had planned on launching the Nano Sale
D cube sat. CubeSats are tiny little satellites. They're usually
um carried along with the payload of other larger satellites. Yeah,
(29:15):
they're they're only ten centimeters square, and so they're really
handy for doing stuff cheaply in space. Yeah, usually it's all.
They're often uses test craft for platforms for for testing technology,
or they're used in various ways. A lot of crowdfunded
science uses these sort of cube satellites for various means.
(29:35):
They're really cool. Um Now, in this case, there was
going to be a launch in two thousand eight, so
this that would have been the first solar sale launched,
uh and so NASA would have been the first to
ever do it. But the satellite was lost during the launch,
so they were unable like, like, where did we put
(29:57):
the satellite. It was right here next to my key
ease like that, but more explosively. So Nano scale D
two was but that one was a success. So that
one happened in two thousand and ten. But it did
happen just a few months after uh, the Koros solar
sale satellite went up. This one was a one square
(30:18):
foot or nine point three square meter solar sale and
it was attached to a small satellite, also meant as
a proof of concept, and it orbited the Earth for
two hundred forty days and then re entered the Earth's
atmosphere and uh and burned up on It was not
was not designed to come back in one piece, but
(30:40):
was meant to just be sort of a proof of
concept to prove that the technology to deploy the sale
would work, that the sale would operate as expected, that
sort of thing. Sure. Yeah, um, but I had heard
a while back that there was supposed to be uh
something launching from NASA this year. Yeah, that was the
sun Jammer. Uh. It was supposed to launch this year.
(31:02):
It was supposed to be this enormous solar sale. This
was gonna be the next big step, the one saying
here's going this is going to be a propulsion technology
for the future, and this is our serious show of
what it can do. It was to have a nearly
thirteen thousand square foot sale that's twelve hundred square meters,
(31:22):
so much bigger than the previous ones, but it was
actually scrapped last year. In two thousand fourteen, NASA said
that they had quote a lack of confidence in its
contractors ability to deliver end quote. That's a quote from
Space News, not from NASA itself. So in other words,
they had partnered with a contractor to design the solar
(31:45):
sale and over the course of the partnership realized that
things were not coming together on schedule or on budget
or both, and so in fourteen they said, we're not
doing this anymore. And that pretty much ended the quest
to use solar sales for the near future in NASA,
(32:05):
But not as it turns out, for everybody. And that
brings us to the light sale project and our buddy, uh,
the science guy, Bill Nill. Yeah, Bill Knight, the science guy.
He built a solar sale. Well, he heads the group
that built the solar sale, or that oversaw the building
of the solar fine. Uh. It was on one of
(32:28):
those long lost episodes of Bill Night the sides guy. No,
so he built it, then he put it in a catapult,
shouted across the room, and then showed us a replay
and slow motion four or five times. Slight misinformation from Joe,
But here's what actually happened. So Bill Ny is the
CEO of a group called the Planetary Society, which is
a citizen funded, uh group that's dedicated to really promoting
(32:53):
science and to performing science experiments by involving citizens in
various means. Right. It was co founded by Carl Sagan
and Lou Friedman, who I mentioned earlier and one other
human person who I am forgetting right now, But at
any rate, it was it was again like great science communicators,
(33:14):
and so you know Carl Sagan an amazing science communicator, right,
Bill Night also a great science communicator. So it's it's
the continuation of that, and it's getting people involved on
various levels, including through crowdfunding. Um. So there are a
couple of companies involved in this, right Uh. Yeah, that's
Stellar Exploration Incorporated and Ecliptic Enterprises, as well as a
(33:38):
couple of universities California Polytechnic State University and also Georgia Tech. Yeah. Yeah,
In fact, Georgia Tech designed the satellite that was used
as sort of the casing for this particular solar sale.
So the light sale itself is three d and forty
four square feet or thirty two square meters, and that
(33:58):
sale is composed of four triangles of aluminum reinforced milar
that are just four point five microns thick. Yeah, that's
even thinner than the ones I was mentioning earlier, where
like before I had seen five microns, Like that was
when solar sales were first being talked about, and now
we're even developing material that's thinner than that. The whole
(34:21):
thing is packaged in a a three cube SAT configuration,
which which we just mentioned earlier, and so it's only
a couple of feet tall all things considered, right, And
so this was actually launched this year. Light sale went up. Uh,
it was part of a payload. There were some issues
(34:44):
when it was you know, detached from the rest of
the payload. Um. Yeah, there was this lovely glitch wherein Okay,
So the team wanted to see whether or not the
sale had properly unfurled. So they a light sale take
a couple of selfies, and the first one came back fine,
(35:05):
the sale looked great. Everything was really cool. From the
other side, the data that it sent back did not
actually compile into an image. It compiled into nothing. It
was gibberish. And then then the light Sale started transmitting
this continuous stream of gibberish and simultaneously stopped responding to commands.
(35:26):
I would like to think that was the moment that
the Light Sale wanted to learn how to love. I
just thought about event Horizon. I was like, oh, oh,
it unfurled into another dimension. This is bad um. But no, no,
that that is not as far as we can currently tell,
what happened. Right, They did manage eventually to reconnect with
(35:47):
the lights Sale. There were a lot of issues, but
they ended up calling the entire mission that success because
its purpose was simply to test the deployment of the
light Sale. It wasn't meant to actually use the light
Sale for propulsion. It was just to make sure that
what they had designed would work. And so this sets
(36:07):
us up for the next project. Now, if you're wondering
what happened to the Light Sale, it actually re entered
the Earth's atmosphere on June fifteen, two fifteen and approximately
one pm and burned up, and some child saw a
shooting star made a wish that was not a shooting
star child wish that will never be granted. You don't
(36:29):
know that that child might end up becoming the first
person to set foot on Mars, which would be very poetic.
But at any rate, the this this mission was all
about setting a platform upon which further missions will be built,
and the Planetary Society already has that in mind. They're
going to launch another light sale in late uh and
(36:51):
this one is actually going to go at an altitude
high enough to deploy the sales and use it for propulsion.
So this will go beyond just the employment phase to
actually zipping around a little bit out in space, which
is pretty exciting that that's part of why the first
light sale did not move anywhere, because it was in
a low enough orbit that enough of the Earth's atmosphere
(37:11):
was still in the way for it to really uh
moving again, going yeah, it was it was that would
block whatever moment timate would have picked up. This one
is the one that actually is going to be inside
the satellite designed by Georgia Tech, that it's going to
be a prox one satellite. Ah. Yeah, they're gonna launch
it on a Falcon heavy rocket from SpaceX are old friends,
and um, the prox One is going to deploy the
(37:33):
light Sale and then kind of follow along its path,
providing data on its performance and taking some pictures and
stuff like that. And it's possible that I'm just not
properly understanding the press releases, but I think it's going
to be able to like automatically nudge the light Sale
around to keep it on its proper flight path. Yeah,
so it's going to have some adjusting ability to make
(37:54):
sure that it is. Yeah, yeah, yeah, that makes sense.
And if you happen to be listening to this podcast
before Friday June, which is my birthday, oh hey, happy
early birthday. Thank you. Um you can fund light Sale
on Kickstarter. We'll try to remember to link it on
social but I have complete faith in all of you
(38:15):
to google light Sale Kickstarter and figure it out. Yeah.
So really exciting. Potentially one of the new methods of
zipping around outer space without having to worry about all
that fuel, which you know is a is an amazing possibility.
I don't know that light sales are going to be
(38:35):
used for everything, And of course they're very similar to
what we've what would be called a beam sailor. Beam
sailors would be based on almost identical principle, except instead
of capturing photons from the sun, you would aim a
beam of energy at the sale to move it along.
So that's something that people have talked about possibly using.
(38:57):
You could equip like a laser on one of these
vehicles and use it to blow air in its own
sales essentially kind of yeah yeah, Or you could use
one from directed from the ground, or from a satellite,
or from a space station. There are a lot of
different potential uses of this. Uh. So I'm really excited
that we're seeing what could be the dawn of a
(39:19):
new era of space exploration. Um, you know, it's it's
really exciting. And also to know that we could get
directly involved by and by funding it or by joining
organizations like the Planetary Society and uh and and putting
our stamp on that era of space exploration, that's really cool.
(39:43):
So I'm glad that we had chance to talk about this.
It's it's one of those things that captures the imagination,
especially like I'm a huge fan of sailing, here on Earth.
So the thought, oh yeah, yeah, I actually uh was
helmsman for the oldest sailing vessel in the Southeast a
few years ago. The Governor Stone. Uh yeah, I'll tell
(40:08):
you guys about it later anyway. Um yeah, So this
was a lot of fun to cover. If you guys
have any suggestions for future topics, maybe it's another space
related topic, or you know one of our other favorite
topics like three D printing or robots, you can let
us know, send us a message, or you just have
a question or comment about the show. You can send
(40:28):
us an email that addresses f W Thinking at how
Stuff Works dot com, or drop us a line on Twitter,
Google Plus or Facebook. At Twitter and Google Plus, we
are f W thinking at Facebook. Just search hift of Thinking.
It'll pop right up there in the search results. You
can leave us a message there and we'll talk to
you again really soon. Topic in the future of technology,
(40:54):
visit forward Thinking dot com. Brought to you by Toyota.
Let's go places
Brought to you by Toyota. Let's go places. Welcome to
Forward Thinking. Hey there, and welcome to Forward Thinking, the
podcast that looks at the future and says, I'm sailing away.
I'm Jonathan Strickland, I'm Lauren Bocan, and I'm Joe McCormick.
(00:20):
And guys, I thought today we could talk about solar sales.
We've mentioned them a few times in past episodes, and
I will probably talk about them in future episodes too.
But the reason why I specifically wanted to bring it
up is because, not too long ago, in the news
we're recording this in June, there was a story about
a crowd funded solar sale projects. So we're gonna talk
(00:43):
about that a little bit later in the episode. But
in order for that conversation to even make sense, we
need to just kind of talk about what these things
are in general and what their purpose is. Now we're
solar sales, the vessels that Sailor Moon and the other
sailor scouts sail I don't know, because Lauren had not
gotten that far into the explanation of what Sailor Moon
(01:06):
is all about for us. Can you help us out here, Lauren,
um I believe they are not, although I'm sure the
magical cats Luna and Artemis are very fine sailors. We
we honestly were having Lauren explained to us what sailor
Moon is all about earlier. So so, yeah, that's just
a peak in the inner working, so forward thinking. But
(01:29):
of course solar sales are not a component of a cartoon.
They are a reality. Yeah. Yeah, it's a propulsion system
that doesn't require fuel. Now, we just recently on this podcast,
talked about a supposed propulsion system that doesn't require fuel
in our podcast on the M drive and the microwave
(01:50):
oven that makes rockets go, well, yes, supposedly, no, no,
makes a vessel go without the need for rockets, and
the appeal of the M drive as it is supposed
to work. Now, we ended that podcast with a lot
of hesitation about whether something like this could actually work.
But if you take the M drive proponents at their word,
what they're saying happens is they've got a method for
(02:13):
making a spaceship go through space without a chemical reaction,
shooting stuff out the back of it without any kind
of propellent. Yeah yeah. And and the reason why that's important,
obviously is that you can't carry an infinite amount of
fuel on your spacecraft, right you. You are limited by
the volume of whatever vessel you have, and the reality
(02:35):
that fuel is a three dimensional thing that you have
to lug around, right yeah, And that it adds weight
to the spacecraft, which means the more weight you add,
the more fuel you need in order to escape the
gravitational poll of the Earth I mean. And then once
you're out into space, then you need more fuel to
get to where you're going to accelerate to whatever the
top speed is. You can only accelerate so much with fuel.
(02:58):
Of course, if you had some sort of system that
could gather fuel while you are sailing through space, then
that would help solve it. And there are ideas like
that you can travel along through space picking up tiny
particles and ions and and heaving those out the back
of a spacecraft. There's not much mass in those, so
(03:19):
you don't get a lot of acceleration, but slowly over
time you can build up speed with the method like that.
And another method similar is solar sales, and that it's
again one something that has a steady but but low acceleration,
so you're you're consistently accelerating at least until you get
to really kind of the top speed of whatever mass
(03:41):
you are you are using. Uh, but you are accelerating
steadily up to that point. It's just that it's a
low level of acceleration. And the reason why we call
them solar sales is that they're very similar, at least
in concept, to the sales that we use here on
Earth to propel things like oats and ships, right, which
are I suppose technically fueled by the sun because the
(04:04):
Sun heats the Earth which makes the wind blow. That's true. Yeah,
if we go far enough back, it is. It is
kind of a solar powered means of propulsion. But surely
you're not suggesting that there is wind in space. Well,
it's similar into wind in space. We're specifically talking about
photons in the case of solar sales. But before I
(04:25):
get too far, I do want to make one distinction
clear for any of our sailing friends out there. It's
more a solar sales more like a an Earth sail
if you were sailing directly downwind. Uh. This is an
important distinction because sales can actually be used to sail
sort of into the wind, which seems counterintuitive. But it's
(04:46):
because the construction of sales is such that they act
kind of like a airplane wing does, so you can
actually yeah, yeah, Otherwise you could only go in the
same direction that the wind is blowing, which would not
be terribly that would be inconvenient. I've actually always wondered
about that. I have no idea how that works. It's
very much like a like an airplane wing. It's designed
(05:07):
so that the airflow is different across one surface than
the other, and it's it's similar to generating left except
you're generating thrust essentially, So solar sales are more like
if you're sailing directly down wind, you're catching the wind
to push you forward. In this case, a solar sale
is capturing or or is acting as kind of a
(05:28):
surface for photons to bounce off of. And photons, as
we have talked about many times on this show, are
particles of light. Sure, A photon is a a quantum
of light. It's the smallest indivisible unit of light energy
that transfers the electromagnetic force throughout the universe. So yeah,
(05:48):
the Sun is of course putting out lots of photons
all the time, shining them out into the universe. That
shining is of course electromagnetic radiation, and it turns out
you can use that shine, meaning the sunshine, the electromagnetic
radiation coming off of the Sun to push a sail
in the same way the wind would push a sail
on Earth. But that's kind of weird because the wind
(06:12):
that pushes a sail on Earth is made up of
particles of air. It's gas, it's massive particles, and it's
very easy to see how that imparts a force, how
that gives momentum to the craft that's attached to the sail, right,
because yet again the air that we are breathing is
not open empty space. It's soup. Right. But if you
(06:35):
remember from like a high school physics class, what is momentum,
There's that equation P equals m v, so that will
tell you that momentum is mass times velocity. So you
take the you know, the mass of the wind hitting
the sail and how fast it's hitting the sail on
that vector. That's important. And I was about I was
(06:56):
about to throw in the direction, but you you covered
it exactly. Velocity is is a is a vector, and
that you need both a magnitude in a direction for
that particular measurement. But yes, exactly. You take that mass,
you take the velocity, you multiply them together, you get
the momentum. This is sort of a way of describing
the movement energy of UH an object in motion and
(07:21):
with massive objects. That makes it pretty simple to understand.
You know. You think, oh, if I'm running at a
speed of eight miles per hour, I have a certain
amount of momentum. It's going to take a certain amount
of energy to stop me because of the the energy
that I that that represents. If a semitruck is traveling
(07:42):
at eight miles per hour, it's going to need more
energy to stop it because it is a much more
massive object, all right, And in the stopping of it,
it's going to transfer some of that momentum to the
object of stopping. Yeah. So if you if you have
something that is has less uh potential force there, then
you probably aren't going to stop this in my truck,
(08:02):
but you will definitely alter the stopping whatever it was,
like a wall or fence. Yeah. But photons, the makeup
of the sunshine don't have any mass. They don't have
a rest mass or variant mass, right, Yeah, so this
makes it a little tricky because you would think, well,
we just talked about how that that equation is mass
(08:25):
times velocity, So how could a photon that has no
mass transfer momentum, I mean, momentum depends on mass, right, Yeah,
But one way I've seen of explaining this is to
say that momentum isn't really fundamentally mass times velocity. That's
just sort of the Newtonian level shortcut for describing how
(08:45):
things work, and and it makes sense because for most
of us that's i mean, that's the world we live in,
I'm sure in the macro level, or at the macro level.
Rather if we're going to use prepositions correctly, which we are, Uh,
that's completely valid. But photons are are in that strange
little little less than big. Yeah, we're talking quantum level
(09:10):
on there. Yeah. So you could look at this in
terms of quantum mechanics or in terms of relativity. But
either way, what this works out too is that the
energy of a photon sort of plays the role of
mass that we would usually think about in this equation.
And Einstein pointed this out right, there's the famous equation
E equals mc squared. This tells you the relationship between
(09:33):
energy and mass. So a small amount of mass is
equivalent to an enormous amount of energy because you're multiplying
at times the constant of the speed of light squared. Well,
that also means that mass is equal to energy divided
by c squared. You know, you just change around the
the equation there. So that photon, that representation of a
(09:56):
of an amount of energy of light is equivalent to
a certain amount of mass. It's just a very small
amount of mass. But that small amount of mass doesn't
think you know, the fact that it's small doesn't really
matter because of two big things. Really. One is that
in space you don't have gravity to work against. So, uh,
any amount of momentum transferred to the solar sale is
(10:19):
going to have some effect the the solar sale is
going to end. Whatever is attached to it is going
to move in the opposite or or is going to
move in the same direction as the impact. Secondly, it's
not like it's a single photon that's saying the solar sale.
There are lots of photons hitting the solar sale. They're
doing so at the speed of light. Uh, So you
(10:40):
are getting a transfer of momentum in that way. Light
itself can have momentum, as can other types of electromagnetic radiation,
so that's kind of exciting. So each individual photon imparts
only a very slight amount of momentum, but there's enough
of them that you can build up a traveling force
over time, right. And the amount of moment to possessed
(11:00):
by any individual photon is dependent upon that photons wavelength
and frequency. So if you were to take a photons
frequency and its wavelength and multiply them together, the product
would be the speed of light, all right. So in
other words, if you have a longer wavelength of light,
(11:20):
it's going to have a lower frequency. Though those two
have to change, right, because the end product has to
be the speed of light with a photon. If you
know one of these variables, you know the other one, right.
So higher frequencies have shorter wavelengths, and they also have
higher energy levels. So a high frequency, short wavelength photon
has more energy than one that has a lower frequency
(11:42):
but longer wavelength. Uh, that's important as well. And Uh,
there's an astrophysicist that actually, Joe you had had clued
me in on that. I had read some of his
work before, but didn't know him by name and his
explanations of this sort of stuff really made it a
lot easier to understand. Yeah, his name is Ethan Siegel.
(12:03):
He's one of my favorite science bloggers on the internet.
He's on Twitter as at starts with the Bang. He's
really worth reading. And he also, for me, has made
a lot of sort of astrophysics concepts much easier to grasp. Yeah,
and he's also he's also kind of an eccentric guy,
and I dig that. It's pretty awes Yes, he does. Yeah,
(12:24):
like his Twitter handle, he's got horns coming out of
his head and stuff. It's pretty pretty cool. Cool. Yeah,
So now we've we've got up the the physics behind
why solar sales could work as a means of propelling
a spacecraft without using any actual fuel. Uh. Now, to
actually take advantage of it, you have to build your
(12:48):
spacecraft in a very strategic way. You want to minimize
the amount of mass you're using so that the propulsion
from the solar energy is max smized, because the more
massive it is, the more solar energy you're going to
need to you know, it's going to it's going to
accelerate slower and slower, or as the mass increases, the
(13:09):
rate of acceleration is lower, so it takes longer to
accelerate to those incredible speeds. Alright, same principle is if
you have a heavier car, it takes more gas to
move it, right yeah, yeah, very similar to that. But
you also want the largest possible surface on which the
sun can push right yeah. Yeah. It doesn't do you
much good if your solar sale is you know, a
(13:31):
couple of square inches, then it's not going to capture
enough photons for that to really be worthwhile. So you
want a lot of surface area, uh, and not a
lot of mass. So that also means that whatever material
you're using, you want it to be super thin. Uh.
Tends to be reflective, so the photons hit it, they
bounce off, and the momentum is transferred to the solar sale,
which in turn transfers that momentum to the spacecraft itself. Uh. Now,
(13:55):
this acceleration, like we said, is small, but and it
is continuous. So the longer the spacecraft is capturing the
solar energy, the faster it is moving. It's accelerating slowly
over time, but it keeps going until you've reached the
maximum speed that spacecraft can go according to its uh mass,
(14:18):
or you are no longer able to capture a significant
amount of photons to continue accelerating. But either way, at
that point, you're traveling at an incredible, incredible speed and
you're not going to slow down unless you encounter something
that makes you slow down, like an asteroid, yeah, or
a planet or a moon or something that has a
gravitational effect on your spacecraft. Right, or you know those
(14:40):
jerk aliens. I hate the jerk aliens, always clinging onto
stuff much before rotisserie. Oh nice, Okay, so moving on.
Typically this super thin solar sale is only a few
microns thick. So to get an idea of how thin
we're talking about, I you get a plastic bag from
(15:01):
grocery store, you know, your typical thin plastic bag. Those
tend to be twice as thick or more than twice
as thick as the solar sale material. So this is
really thin, delicate stuff. Yeah. That material is typically a
polymer film that's capable of withstanding the high temperature fluctuations
of space because it can be pretty chilly and it
(15:23):
can also be pretty warm, depending on how much radiation
is hitting you at the time. Some researchers have also
investigated using carbon fiber woven to be you know, hundreds
of times thicker than these films would be, but just
as a light due to their structure, their holy holy structure. Ye,
holy as in lots of holes in it. Yes, yes,
(15:44):
you really can't say holy twice without saying it thrice,
holy holy holy, Right, let's hear it again, holy holy
holy structure. Um, that's my high Church of technology talking.
That's fair, thank you, thank you. So if you're wondering
what kind of fantastic speeds were actually talking about, well,
(16:06):
Planetary Society co founder Lou Friedman once told the UK's
Royal Society of Chemistry, and by once, I mean back
in two thousand nine that the contemporary technology should allow
acceleration rates of about point zero zero zero five meters
per second. Well, all right, so what's the miles per hour?
That's point zero one miles per hour. This is the
(16:28):
acceleration rate. Yes, yes, um, I mean, of course, given
a probable size of sail and weight of vehicle that
you would expect to be launching like the kind of
things that they were thinking about in two thousand nine,
which we will get into a little bit later here,
um to to get that up to a sort of
range that's a little bit more understandable. Over the course
(16:49):
of the of a day, that's about a hundred and
sixty kilometers per hour a k A about a hundred
miles per hour, and that means that in a year
it could hit thing like fifty eight thousand kilometers per
hour or thirty six thousand miles per hour, which is
something like three times the speed of our current interplanetary missions.
(17:10):
That's that's now, that's incredible because again, just through the
fact that it is continuously accelerating, it's able to hit
these speeds. And sure it takes a long time to
hit those amazing speeds, but it can and it doesn't
require the use of fuel. That's why it's so attractive. Now,
what would you actually be using these solar sales for,
I mean, what would it be propelling? Obviously, uh, we're
(17:34):
not necessarily talking about manned missions here, where we'd have
people aboard a uh some form of transport and using
solar sales to move. That's a possibility, but it's not
necessarily what they'd be used for. Well, they have very
few moving parts because you really just need to be
able to deploy the solar sale right, unfurl the sail,
(17:57):
and and then you end up there. There needs to
be some means of controlling the the attitude, the the
the position. Yeah, the position of the spacecraft in relation
to whatever source of photons you're talking about. You need
that as well. But apart from that, you're you're pretty
much set. So they're great candidates for reuse. So instead
of having to build a spacecraft for every single mission,
(18:19):
you could have a solar sale craft that could potentially
be used multiple times before ever needing to be replaced.
So they'd make really great delivery or cargo vehicles in
this way, I've seen one of the big ones. One
of the big use cases that has been put forward
is it could be used to deliver cargo and supplies
to Mars. Now, you wouldn't have a solar sales spacecraft
(18:41):
land on Mars. That would not be good for anybody there.
But what you could do is have it fly by
Mars and do essentially a controlled drop of cargo. Or
it could rendezvous with other spacecraft like a space station
that's in orbit around on Mars. You could have a
rendezvous where cargo gets transferred and then the solar sale
(19:05):
is redirected and sent back to Earth. It can be
kind of a taxi vehicle, another another interplanetary uber. It
could be. Yeah, I wouldn't be surprised if we see
an app for that in the next five years. But
the next application would be possibly to create an early
warning system for space weather. Uh. This would be really
(19:26):
useful solar weather happens. I mean you probably are at
least familiar with solar flares. They have the potential to
disrupt electronics here on Earth. If it's a large enough
solar flare, it can cause some surges in things like
power grids, and in fact, it can even cause an
entire blackout of a region if it's powerful enough. There's
(19:48):
also coronal mass ejections, which sometimes but not always a
company solar flares that can cause some problems, uh, and
we're not always aware of them until it's pretty late
in the game. So if we were able to put
spacecraft into different orbits, then we can usually uh achieve
on our own. Then with our other satellites and other probes,
(20:10):
then we could have uh more of a a complete
look at what's going on with the Sun at any
given time, and then if we spot warning signs, we
might be able to prepare ourselves in the event of
a solar flare coronal mass ejection that could potentially cause
havoc here on Earth. It might mean being able to
balance loads or reduce loads on our electrical grids to
(20:35):
reduce the potential damage that could happen. It's really important,
and it's something that a lot of people have been
pushing for for a while, saying, you know, it's just
a matter of time before there's a big solar flare
up that could at least temporarily cause real problems for
us here on Earth or yeah, yeah, I mean the
(20:57):
and these weather patterns happen in cycles. Now, just because
they happened in cycles doesn't mean that every eleven years
we're going to get a massive solar flare that's gonna
wipe out you know, Detroit or something. It's that's not
what it means. But it does mean that they there
are periods of increased activity and then there are periods
of a lull of activity. But this sort of spacecraft,
(21:18):
a solar sales spacecraft that could go into these eccentric
orbits that normally we wouldn't be able to achieve, could
at least give us a heads up when that sort
of thing might happen. You know, what could be even
better is if we made one that was really big,
just big enough to completely block the Sun from the Earth,
and then we'd never have to worry about So you're
(21:40):
taking the Mr. Burns approach. I see, I always liked
something about him. Excellent. So it could also be used
to propel spacecraft through interstellar space, not necessarily carrying humans,
but maybe who knows, by the time we get to
the point where we were seriously talking about in interstellar travel,
(22:00):
it might be one of the more approved of ways
of doing that. UM. But what you would typically do
would you would have your spacecraft do a run near
the Sun so it could get a good boost of
energy and then uh accelerate as it moves outward to
escape the solar system. Uh. Eventually you would get to
(22:22):
a point where you would have fewer photons hit the
solar sale, so you wouldn't really receive the acceleration that
you had when you first passed by the Sun. But
by that point you're already traveling at this insane speed,
so it would be probably one of the more viable
means of propelling a spacecraft outside the Solar System. Uh,
(22:44):
in a you know, reasonable time frame. By reasonable, I'm
still talking a long long time, you know, not necessarily
something like oh, within within a year and a half
will be on the Solar System. That yeah, but but
more reasonable than the generations upon generations that it would
currently take. You get out right doing like little slingshots
around various planets and stuff. Um So, also it might
(23:07):
be used to help protect us against collisions from space rocks,
like like giant asteroids. I've actually read about this method. Yeah.
So the idea is, if you have an asteroid on
a collision course with Earth, you don't necessarily have to
destroy the asteroid to protect the Earth. You just have
to divert its path. Yeah. In fact, destroying the asteroid
(23:30):
might be not as productive in the sense that now
you've got a whole bunch of little asteroids aiming at
Earth instead of a big one. In the words of
some random guy from the movie Independence Day, you risk
turning one dangerous falling rock into many. Yeah. I think
phil Plate has referred to it as as you turn
you turn a slug into a blast of shotgun pellets um,
(23:52):
and and so the idea would be you attach a
solar sale to this, like, well, first you have to
detect it, right, you detect that there is an a
body that is on a potential collision course with Earth,
although hey, having erratic satellites up there might help with
detect and having having the enormous solar sale satellites to
(24:13):
kind of detect that sort of stuff. Plus we've got
really sophisticated uh telescopes these days that can detect stuff
from much further away than we did before. Then what
you would want to do is send up a spacecraft
that could attach itself to the asteroid and deploy a
solar sale and use that that momentum from the photons
(24:36):
to help pull the asteroid off course. And it doesn't
have to be that far, assuming you catch it far
enough away from the Earth, right, Yeah, So the idea
is you'd essentially make the sun word facing side of
the asteroid a huge mirror, and then you'd hope that
over time it gathers enough acceleration away from the Sun
(24:59):
via that huge mirror, the same principle as a solar
sale to make it miss the Earth. But like you
were saying, Jonathan, this would only work if you had
a very long lead time because that acceleration based on
the photon reflection is going to be pretty slow. Right, Yeah,
you need to make sure that you know. The earlier
you are able to deploy this, the better your chances
(25:20):
are of of diverting the pathway so that you no
longer have to worry about a collision. But again, it's
when you think about it, it really does make sense.
Like if I'm standing two feet away from you, uh,
and I have a water a water pistol in my hand,
and then I move my my hand just a little
(25:40):
bit to the left or right, I'm still gonna hit
you because I'm two feet away from you. But let's
say that this water pistol can shoot water across the
football field. First of all, you're not gonna want me
to shoot you from two feet away. But let's say
I'm I'm across the football field from you and I
move my hand that same distance. Because of the distances involved,
obviously the the trajectory, it's gonna totally miss you, you know,
(26:03):
not taking wind into account, which I never do anyway.
So uh yeah, that's the same basic idea from this
potential use case. So let's talk about some solar sale projects,
because this is not science fiction. This is actual technology
that has already been used. Well it's yeah, it's not
even science. Maybe one day it's it's science. A few
(26:25):
years ago. Yeah, yeah, the first one Okay, well the
first one was not supposed to be the first one
if things had worked out properly. But what ended up
being the first solar sale spacecraft that actually worked was
the Chorus Space Probe, which was not choros I K
A R O s uh. So this was in June
(26:48):
of so this was just a few months before another
solar sale test craft was launched by NASA. Uh it
was launched by the Japan Aerospace Exploration Agency or Jackson
and ACARUS is actually an acronym. It's not all capitalized.
It's like some other acronyms that are no longer completely capitalized,
(27:11):
but stands for interplanetary kite craft accelerated by radiation of
the Sun. I wonder how many people had to think
of the like the acronym. Yeah, but it was all
meant to just demonstrate whether or not solar sales could
could really work. Why is the acronym in English as
(27:32):
another excellent question to which I do not have an answer.
I can give you a few more details about the craft,
but I can't tell you what you know why it's
called that? Uh not interested? Sorry, Well for everyone who's
not Joe, tell me about the craft, all right. Uh So,
(27:52):
the sale itself was forty six ft wide, which is
fourteen meters, and uh Acorus had l c D p
annals on the edges of the sail. And you might
wonder why why would a solar sale have l c
D panels. And it was all to control their reflectivity
of the sales because that was how the spacecraft could
(28:12):
adjust its attitude in space. Not like it had a
bad attitude. I don't. I don't mean attitude in that
sense like mood. I'm talking about its position relative to
the sun. Oh okay, so this should be kind of
like the boom on a sail on a sailboat, where
you can sort of like adjust its attitude towards the wind. Right.
So in this case, you're adjusting the reflectivity of the sale,
(28:33):
or at least the edges of the sail, and that
is what would cause the photons to either transfer more
or less momentum to those edges, and that would adjust
the attitude of the spacecraft, which I thought was a
very elegant means of a of of creating a control system.
Um so that was pretty cool. Now. The second one
(28:55):
was the Nano Sale D two, and that too is important.
Uh So this was one that was launched by NASA.
You see, they had planned on launching the Nano Sale
D cube sat. CubeSats are tiny little satellites. They're usually
um carried along with the payload of other larger satellites. Yeah,
(29:15):
they're they're only ten centimeters square, and so they're really
handy for doing stuff cheaply in space. Yeah, usually it's all.
They're often uses test craft for platforms for for testing technology,
or they're used in various ways. A lot of crowdfunded
science uses these sort of cube satellites for various means.
(29:35):
They're really cool. Um Now, in this case, there was
going to be a launch in two thousand eight, so
this that would have been the first solar sale launched,
uh and so NASA would have been the first to
ever do it. But the satellite was lost during the launch,
so they were unable like, like, where did we put
(29:57):
the satellite. It was right here next to my key
ease like that, but more explosively. So Nano scale D
two was but that one was a success. So that
one happened in two thousand and ten. But it did
happen just a few months after uh, the Koros solar
sale satellite went up. This one was a one square
(30:18):
foot or nine point three square meter solar sale and
it was attached to a small satellite, also meant as
a proof of concept, and it orbited the Earth for
two hundred forty days and then re entered the Earth's
atmosphere and uh and burned up on It was not
was not designed to come back in one piece, but
(30:40):
was meant to just be sort of a proof of
concept to prove that the technology to deploy the sale
would work, that the sale would operate as expected, that
sort of thing. Sure. Yeah, um, but I had heard
a while back that there was supposed to be uh
something launching from NASA this year. Yeah, that was the
sun Jammer. Uh. It was supposed to launch this year.
(31:02):
It was supposed to be this enormous solar sale. This
was gonna be the next big step, the one saying
here's going this is going to be a propulsion technology
for the future, and this is our serious show of
what it can do. It was to have a nearly
thirteen thousand square foot sale that's twelve hundred square meters,
(31:22):
so much bigger than the previous ones, but it was
actually scrapped last year. In two thousand fourteen, NASA said
that they had quote a lack of confidence in its
contractors ability to deliver end quote. That's a quote from
Space News, not from NASA itself. So in other words,
they had partnered with a contractor to design the solar
(31:45):
sale and over the course of the partnership realized that
things were not coming together on schedule or on budget
or both, and so in fourteen they said, we're not
doing this anymore. And that pretty much ended the quest
to use solar sales for the near future in NASA,
(32:05):
But not as it turns out, for everybody. And that
brings us to the light sale project and our buddy, uh,
the science guy, Bill Nill. Yeah, Bill Knight, the science guy.
He built a solar sale. Well, he heads the group
that built the solar sale, or that oversaw the building
of the solar fine. Uh. It was on one of
(32:28):
those long lost episodes of Bill Night the sides guy. No,
so he built it, then he put it in a catapult,
shouted across the room, and then showed us a replay
and slow motion four or five times. Slight misinformation from Joe,
But here's what actually happened. So Bill Ny is the
CEO of a group called the Planetary Society, which is
a citizen funded, uh group that's dedicated to really promoting
(32:53):
science and to performing science experiments by involving citizens in
various means. Right. It was co founded by Carl Sagan
and Lou Friedman, who I mentioned earlier and one other
human person who I am forgetting right now, But at
any rate, it was it was again like great science communicators,
(33:14):
and so you know Carl Sagan an amazing science communicator, right,
Bill Night also a great science communicator. So it's it's
the continuation of that, and it's getting people involved on
various levels, including through crowdfunding. Um. So there are a
couple of companies involved in this, right Uh. Yeah, that's
Stellar Exploration Incorporated and Ecliptic Enterprises, as well as a
(33:38):
couple of universities California Polytechnic State University and also Georgia Tech. Yeah. Yeah,
In fact, Georgia Tech designed the satellite that was used
as sort of the casing for this particular solar sale.
So the light sale itself is three d and forty
four square feet or thirty two square meters, and that
(33:58):
sale is composed of four triangles of aluminum reinforced milar
that are just four point five microns thick. Yeah, that's
even thinner than the ones I was mentioning earlier, where
like before I had seen five microns, Like that was
when solar sales were first being talked about, and now
we're even developing material that's thinner than that. The whole
(34:21):
thing is packaged in a a three cube SAT configuration,
which which we just mentioned earlier, and so it's only
a couple of feet tall all things considered, right, And
so this was actually launched this year. Light sale went up. Uh,
it was part of a payload. There were some issues
(34:44):
when it was you know, detached from the rest of
the payload. Um. Yeah, there was this lovely glitch wherein Okay,
So the team wanted to see whether or not the
sale had properly unfurled. So they a light sale take
a couple of selfies, and the first one came back fine,
(35:05):
the sale looked great. Everything was really cool. From the
other side, the data that it sent back did not
actually compile into an image. It compiled into nothing. It
was gibberish. And then then the light Sale started transmitting
this continuous stream of gibberish and simultaneously stopped responding to commands.
(35:26):
I would like to think that was the moment that
the Light Sale wanted to learn how to love. I
just thought about event Horizon. I was like, oh, oh,
it unfurled into another dimension. This is bad um. But no, no,
that that is not as far as we can currently tell,
what happened. Right, They did manage eventually to reconnect with
(35:47):
the lights Sale. There were a lot of issues, but
they ended up calling the entire mission that success because
its purpose was simply to test the deployment of the
light Sale. It wasn't meant to actually use the light
Sale for propulsion. It was just to make sure that
what they had designed would work. And so this sets
(36:07):
us up for the next project. Now, if you're wondering
what happened to the Light Sale, it actually re entered
the Earth's atmosphere on June fifteen, two fifteen and approximately
one pm and burned up, and some child saw a
shooting star made a wish that was not a shooting
star child wish that will never be granted. You don't
(36:29):
know that that child might end up becoming the first
person to set foot on Mars, which would be very poetic.
But at any rate, the this this mission was all
about setting a platform upon which further missions will be built,
and the Planetary Society already has that in mind. They're
going to launch another light sale in late uh and
(36:51):
this one is actually going to go at an altitude
high enough to deploy the sales and use it for propulsion.
So this will go beyond just the employment phase to
actually zipping around a little bit out in space, which
is pretty exciting that that's part of why the first
light sale did not move anywhere, because it was in
a low enough orbit that enough of the Earth's atmosphere
(37:11):
was still in the way for it to really uh
moving again, going yeah, it was it was that would
block whatever moment timate would have picked up. This one
is the one that actually is going to be inside
the satellite designed by Georgia Tech, that it's going to
be a prox one satellite. Ah. Yeah, they're gonna launch
it on a Falcon heavy rocket from SpaceX are old friends,
and um, the prox One is going to deploy the
(37:33):
light Sale and then kind of follow along its path,
providing data on its performance and taking some pictures and
stuff like that. And it's possible that I'm just not
properly understanding the press releases, but I think it's going
to be able to like automatically nudge the light Sale
around to keep it on its proper flight path. Yeah,
so it's going to have some adjusting ability to make
(37:54):
sure that it is. Yeah, yeah, yeah, that makes sense.
And if you happen to be listening to this podcast
before Friday June, which is my birthday, oh hey, happy
early birthday. Thank you. Um you can fund light Sale
on Kickstarter. We'll try to remember to link it on
social but I have complete faith in all of you
(38:15):
to google light Sale Kickstarter and figure it out. Yeah.
So really exciting. Potentially one of the new methods of
zipping around outer space without having to worry about all
that fuel, which you know is a is an amazing possibility.
I don't know that light sales are going to be
(38:35):
used for everything, And of course they're very similar to
what we've what would be called a beam sailor. Beam
sailors would be based on almost identical principle, except instead
of capturing photons from the sun, you would aim a
beam of energy at the sale to move it along.
So that's something that people have talked about possibly using.
(38:57):
You could equip like a laser on one of these
vehicles and use it to blow air in its own
sales essentially kind of yeah yeah, Or you could use
one from directed from the ground, or from a satellite,
or from a space station. There are a lot of
different potential uses of this. Uh. So I'm really excited
that we're seeing what could be the dawn of a
(39:19):
new era of space exploration. Um, you know, it's it's
really exciting. And also to know that we could get
directly involved by and by funding it or by joining
organizations like the Planetary Society and uh and and putting
our stamp on that era of space exploration, that's really cool.
(39:43):
So I'm glad that we had chance to talk about this.
It's it's one of those things that captures the imagination,
especially like I'm a huge fan of sailing, here on Earth.
So the thought, oh yeah, yeah, I actually uh was
helmsman for the oldest sailing vessel in the Southeast a
few years ago. The Governor Stone. Uh yeah, I'll tell
(40:08):
you guys about it later anyway. Um yeah, So this
was a lot of fun to cover. If you guys
have any suggestions for future topics, maybe it's another space
related topic, or you know one of our other favorite
topics like three D printing or robots, you can let
us know, send us a message, or you just have
a question or comment about the show. You can send
(40:28):
us an email that addresses f W Thinking at how
Stuff Works dot com, or drop us a line on Twitter,
Google Plus or Facebook. At Twitter and Google Plus, we
are f W thinking at Facebook. Just search hift of Thinking.
It'll pop right up there in the search results. You
can leave us a message there and we'll talk to
you again really soon. Topic in the future of technology,
(40:54):
visit forward Thinking dot com. Brought to you by Toyota.
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Fw:Thinking News
Hosts And Creators
Jonathan Strickland
Joe McCormick
Lauren Vogelbaum
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