The year: 1974.
The location: outer space between Venus and Mercury.
NASA's Mariner 10 probe had a serious problem.
Because of some unplanned maneuvers,
they were running much lower on propellant than expected
and in order to maintain control of the spacecraft,
NASA had to come up with a workaround.
If they didn't do something quickly,
the probe could miss Mercury altogether.
That's when engineers came up with an ingenious plan.
And what they ended up doing
was using the solar panels of the spacecraft
and just angling those panels with respect to the sun
and letting sunlight pressure
move and position the spacecraft as needed.
And it worked.
Mariner 10 became the first probe to fly by Mercury,
giving humans the first close-up images of the planet.
This close call showed that solar pressure
could be used to keep a probe on course
just like a sailboat uses the wind.
So NASA was able to successfully
sail with Mariner 10,
even though that was not part
of the original mission design.
Solar sailing uses an existing,
almost limitless energy supply from the sun.
If you have a light on right now,
or are in the sunlight,
you might be surprised to know that that light
is pushing you.
Well believe it or not, sunlight actually
does exert a force on us.
If you go outside on a bright, sunny day,
you're probably feeling the equivalent
of maybe the same amount of force
as a very light feather might exert
resting in the palm of your hand.
It's not very much and we don't even notice it
because even the slightest breezes
will easily overwhelm our sense of
being pushed.
But in space, it's a very different story
because there is no ground to anchor yourself against.
There is no other wind or breezes
or other forces acting on you.
So, ever so slowly
but surely that sunlight pressure will build up
and will very gradually accelerate you away.
Solar sailing was first written about
by Johannes Kepler in 1610
who thought a space sail might one day capture sunlight
the way a boat sail catches the wind.
Although he didn't fully understand the mechanism
to make this a reality,
it was later theorized by physicist James Clerk Maxwell,
who mathematically showed that sunlight
carries momentum that exerts pressure on objects.
If you get in the near vacuum of space
and you have a low-mass, low-weight object
and a shiny, reflective sail
that the light can bounce off of,
you can actually use it to propel a spacecraft.
Or at least that's the theory.
Solar sailing offers a possible solution
to one of the largest obstacles facing space missions today:
a limited fuel supply.
Once you use up all of your propellant,
you've got nothing else to push with.
And that's a fundamental limitation of rockets.
But with successful solar sailing
demonstration missions by the Japanese
Aerospace Exploration Agency, NASA,
and most recently the Planetary Society,
missions could now be longer, cheaper,
quicker and go farther out into space than ever before.
It really opens up the solar system for exploration
on a scale that we cannot come close to
with our current technology.
Astronomers sometimes say that space is curved.
People like Carl Sagan,
the co-founder of the Planetary Society,
saw the potential it had for future missions.
Now what will this do?
Well, it takes you to where you wanna go.
So one mission that's being talked about
is to rendezvous with Halley's Comet.
I've always wanted to do that.
He would inspire a generation
to make his dream a reality years after his death.
But the Planetary Society's first solar sail,
Cosmos 1, never made it into orbit
after a rocket failure in 2005.
It was the Japanese Aerospace Exploration Agency's
IKAROS that became the first to demonstrate
solar sailing in 2010.
And a year later, NASA's NanoSail-D did the same
in low-earth orbit.
But it's the development of even more recent
technologies that are starting to enable real missions.
The key enabling technology behind solar sailing
isn't so much the sail,
it's making the payload
as small and lightweight as possible.
And in recent years, we've developed
what's called CubeSat technology.
We even have what's called NanoSat technology.
And these are tiny satellites
that can weigh less than a kilogram
and contain all of the electronics necessary
to conduct a mission.
Everything from your avionics, your communication,
attitude control, navigation,
everything all baked onto a few chips of silicon.
So these CubeSats, coupled with a solar sail,
make for a very effective yet very low cost payload.
This combination of solar sailing
and lightweight craft, when used together,
could make space exploration cheaper
and more accessible to everyone.
And the Planetary Society set out to prove
that it could be a practical option.
In 2019, their super lightweight CubeSat
the size of a loaf of bread, called LightSail 2,
launched aboard the SpaceX Falcon Heavy.
So LightSail 2 launched as a CubeSat that was this size.
This is a one-to-one cardboard version.
And once it got in orbit,
it opened up
solar panels exposing inside
the sail material
and some of the instrumentation, the cameras.
Then we deployed the sail,
which is about the size of a boxing ring,
32 square meters,
and it deployed these four triangular sails
that come out of the loaf of bread.
The material of the sail itself is Mylar,
so like Mylar balloons but actually thinner.
It's about
four microns in
width, micron being one millionth of a meter,
so it's very thin and to keep it from ripping,
it's got so-called rip stops,
which are strings that are in a hash pattern.
Light from the sun,
which is made up of photons,
hit the shiny Mylar material carrying momentum,
bouncing off and causing a push.
The team then used a momentum wheel to steer the spacecraft.
LightSail 2 was the first ever mission
to successfully maneuver in space using solar sailing.
The main goal with LightSail 2
was to demonstrate controlled solar sailing
in a small spacecraft, specifically CubeSat,
and we did accomplish that.
And it's still sailing.
But this is only the beginning.
In the next few years, NASA's Artemis 1
will head to the moon and on board
will be a solar sailing mission called
the Near Earth Asteroid Scout or NEA Scout.
Once in space, it will separate from Artemis,
and travel to an asteroid within three years
after its launch.
So we actually have an agreement with NASA.
So we're working directly
with their Near Earth Asteroid Scout solar sail mission
and working together to feed forward what we're learning.
But solar sailing isn't only confined
to the inner solar system
where there's plenty of sunlight.
Quite the opposite.
It could offer the best way
to reach the outer solar system and beyond.
But it will need to improve from its current technology.
One of the main disadvantages
with current solar sail designs
is that they are monolithic,
which means that you ultimately have to pitch,
roll and yaw the entire sail.
But if you can break the sail up into component parts,
you can then individually articulate
each of those components
and you can gain a lot more maneuverability.
And that's what a company called Xplore
are working on with their SunVane concept.
SunVane takes a really large sail area
and breaks it up into six or eight individual vanes.
The vanes can then be independently articulated.
That would make SunVane a highly maneuverable sail.
And the advantages of high maneuverability
mean that you can reach a target destination
that much faster,
because you can plot a more direct
and a more efficient course
to get you from point A to point B.
The SunVane will tack inward toward the sun,
like a sailboat tacking into the wind,
and then turn its vanes
toward the sun for maximum acceleration.
The technology demonstration,
which is still in the initial planning stages,
aims to reach speeds of 5 to 8 astronomical units
or AU per year.
One AU being the average distance from the Earth to the Sun.
That will make the SunVane demonstration mission
the fastest man-made probe ever launched,
reaching Jupiter in less than a year.
All without a drop of fuel.
But considering the great distances of space,
it will need to go even faster
and fly even closer to the sun
to accomplish the kind of deep space missions
scientists are hoping to achieve.
But so far the technology isn't there.
Well, the temperatures in that environment
are going to be extremely high.
So you need very lightweight yet very durable materials.
So some advanced materials that might come along
might be something like silicon nitride
or silica sails.
These materials don't yet exist,
but there are companies that are working on developing them.
Another limitation is that solar sails
won't easily be able to carry anything heavy, like a person.
To propel a larger payload,
say a crude payload,
well, you're going to need a very large sail
and a lot of time to get to a sufficient enough speed
unless, of course, you wanna send your crew
into a sun-dive maneuver.
But that might not be very good for their health.
But for smaller craft,
the possibilities are limitless.
The most ambitious mission using solar sails
even involves visiting another solar system,
and would allow us to reach our nearest star system,
Alpha Centauri, in just 20 years.
It's called Breakthrough Starshot.
So Starshot envisions using an array of terawatt lasers,
concentrating their light on a tiny sailcraft
that weighs less than one gram.
In that one-gram package contains the sail,
spacecraft, a camera, a transmission antenna,
everything, all hyper miniaturized.
The NanoSails would accelerate at something like 10%
the speed of light
and potentially reach Alpha Centauri in about 20 years.
While the technology is nowhere near
making Breakthrough Starshot a reality,
solar sailing is entering its next phase.
Missions that were once huge endeavors
because of the cost and size
will soon be able to launch as secondary payloads,
piggybacking off other missions.
That means visiting asteroids, moons of the outer planets
or even interstellar objects
that enter our solar system
could be achieved much more easily.
You get an infinite amount of sunlight
that is never ending,
so you leave your fuel on the ground
and you just continue to sail.
So it's not like sailing by sunlight
is going to replace chemical rockets,
but solar sailing will allow us to do more
than what we can do with chemical rockets alone.
This technology is important for future missions
because it's an enabling technology.
It enables you to do missions
with solar-weather monitoring
that you couldn't do otherwise,
poles sitting on planets that you couldn't do otherwise,
doing multiple encounters
and having a flexibility to adapt
that you couldn't do otherwise.
And someday maybe doing interstellar missions,
which you couldn't do otherwise.