[♪ INTRO]
Someday, we’re going to send people to Mars,
and it’s gonna be awesome.
But for now, everyone from NASA to Elon Musk
is still trying to figure out
the best way to do it.
With today’s rockets, a one-way trip to
Mars takes somewhere around seven months,
but one company is developing an engine
that might be able to get us
there in only forty days.
It’s called the VASIMR engine, and it propels
spacecraft using a jet of plasma.
VASIMR stands for Variable Specific
Impulse Magnetoplasma Rocket,
and the idea behind it has actually
been around since the 1970s.
But engineers didn’t make
too much progress on it until 2015,
when NASA gave the Ad Astra Company a grant
to develop it as part of their NextSTEP program.
It works using a kind of electric propulsion,
and it’s a big step up from the
other engines available right now.
To get your rocket into space, you’d still
need a chemical engine, which generates thrust
with a reaction that releases tons of gas,
like combining hydrogen and oxygen.
So far, that’s the only kind of engine we have
that’s powerful enough
to get a heavy rocket to space.
But once you’re there, you can
move it with all kinds of things,
from ions to particles of light,
depending on what your mission is.
Right now, any spacecraft that would send
people to Mars would still use a chemical engine,
because we mostly have
the technology figured out.
But carrying all that fuel
also adds a lot of weight.
So newer kinds of engines use electric propulsion,
often in the form of ion thrusters,
which create a beam of charged atoms, or ions,
to push your spacecraft around.
Ion engines are a lot more efficient
than chemical engines,
but they aren’t designed to handle large payloads,
like a bunch of humans and all the
supplies they’d need for a trip to Mars.
So we mostly use ion thrusters for small satellites.
VASIMR also uses electric propulsion,
but it will be way more powerful.
It propels the spacecraft by creating plasma,
in the form of a super hot jet
of ions and electrons.
Unlike other kinds of electric propulsion,
it uses radio waves to heat the plasma,
rather than electrodes or
other electronics in ion engines.
Which among other things,
makes the engine a lot more durable.
To make the plasma, it starts by pumping a
gas like hydrogen or argon into a tube,
which is surrounded by a magnet and two couplers,
a kind of device that emits radio waves.
Most kinds of gas will work,
which makes VASIMR really versatile,
but hydrogen is a good choice
if you want a lightweight, easy-to-find fuel.
Once the gas is pumped in, the first coupler
strips some of the electrons off their atoms
and turns the gas into plasma.
At this point, it’s already very hot,
around 5500 degrees Celsius,
but then, the second coupler
makes it even hotter.
It raises the plasma to 10 million degrees Celsius,
which isn’t that far from
the temperature inside the Sun.
A magnetic nozzle then turns that super hot
plasma into a nice, controllable jet,
and it’s shot out of the end of the engine.
Besides being more durable, VASIMR is great
because it also has different settings,
like the gears on a car, which means
it can generate the right amount of thrust
for different kinds of missions.
So besides getting people to Mars,
it could also be scaled down
to send small satellites
zooming around the Earth.
But most importantly for our
future astronauts, VASIMR can be made
big and powerful enough
to move human-sized spacecraft.
Ion engines just aren’t ready to do that
yet, partly because many tend to rely on more
mechanical parts than VASIMR, some of which
aren’t designed to work on a large scale.
Although engineers are working on that, too.
Still, there is one thing we need to figure
out before VASIMR is ready to go:
the power supply.
It takes a lot of power to produce
all those radio waves,
especially if you want an engine
strong enough to push a crew of astronauts.
Solar panels can generate enough power
to propel small satellites,
but we’d need something
a lot stronger for a full-sized spacecraft.
And our best option is probably using
a small nuclear reactor.
But because those have the potential
to be really dangerous,
we’ll want to make sure that
we’re extra confident in that technology
before we start using nuclear power
to transport people through space.
Right now, the goal for the
VASIMR team is to develop an engine
so it can fire for 100 consecutive hours
at 100 kilowatts of power,
which is 10 to 100 times
more power than an ion thruster has.
To get to Mars in 40 days, you’d still need
a lot more power than that,
like, 2000 times more power.
And that’s probably where a
nuclear reactor would come in.
But for now, 100 kilowatts is a good start.
Ad Astra’s plans with NASA
are to have the engine ready
for the 100 kilowatt goal by the summer of 2018.
As of last August, they’d fired the engine
for around 10 hours, so they’re making progress.
Still, even after they meet that goal,
VASIMR will need to go through
plenty of development and tests
before we use it to go anywhere.
So when the first human steps on Mars,
we’ll probably have made it there
with a chemical engine, since that
technology is a lot more developed.
But someday, our trips to Mars
could be a whole lot faster.
Thanks for watching this episode of
SciShow Space!
If you thought getting to Mars
in 40 days sounded cool,
you can watch our episode
on photonic propulsion,
where we explain how we could someday get
to Mars in only three days … at least in theory.
But I wouldn’t hold your breath.
[♪ OUTRO]
