There’s been all kinds of buzz lately about some new space tech that could send a spacecraft
to Mars in 3 days, and maybe even get spaceships to exoplanets that are light-years away.
Which kind of sounds like something out of a science fiction novel.
But a group of researchers from the University of California, Santa Barbara is working on
a new way to travel in space.
Known as photonic propulsion, it would use a giant set of lasers to push ships along.
And if it works, it could eventually be used to explore other star systems.
But that’s a big if.
The project is called DEEP-IN, and its goal is to use electromagnetic acceleration to
get ships close-ish to the speed of light -- fast enough that interstellar travel could
actually make sense.
These days, our spaceships use chemical acceleration -- in other words, they burn fuel -- and they
are fast.
They’re just not fast enough to travel to other stars in any reasonable amount of time,
which is where electromagnetic acceleration comes in.
Instead of using chemical energy to push itself forward, a DEEP-IN spaceship would use the
energy from electromagnetic radiation -- more specifically, the energy a huge set of lasers,
powered by sunlight.
That laser array technology is a whole project all by itself, called the Directed Energy
System for Targeting of Asteroids and exploRation, or DE-STAR, and being developed by the same
research team.
And as you might have noticed from the first part of that acronym, DE-STAR would be a laser
system with multiple uses.
Like, destructive uses.
DE-STAR is mainly being designed to protect Earth -- both by diverting asteroids that
are headed for us, and by vaporizing space debris.
This photon-driven propulsion thing is just a bonus -- a pretty huge one.
It’s based on the idea that light has a lot of pushing power, which comes from its
momentum.
We might not feel that push from just walking around on Earth, but a giant reflector screen
in space does feel it.
That’s the science behind solar sails, and we’ve already built spaceships that use
them.
When the photons in light bump into a solar sail, their momentum is transferred and the
spacecraft is propelled forward a little bit.
DE-STAR’s lasers would provide lots of light that we could use to take the solar sails
concept one step further, and start building spacecraft that use laser sails.
See, solar sails are limited, because the light coming from the sun only comes with
so many photons.
But this laser sail will have a concentrated beam of photons shooting directly at it.
It’s like the difference between a sprinkler and a fire hydrant.
When it gets hit by that laser beam, the laser sail -- and anything that happens to be attached
to it, like a spaceship -- is going to start zooming through space.
A ship that used a laser sail wouldn’t have to carry as much fuel, which would mean that
it could have a much lower mass.
It could, also, in theory, go very, very fast.
With a huge laser array putting out 50-70 gigawatts of power, a 100 kilogram ship -- about
the size of Voyager 1 -- could travel at around 1.5% of the speed of light -- nearly 300 times
Voyager’s top speed.
But there are still challenges to solve, when it comes to making spaceships powered by giant
lasers.
We /could/ send a smaller probe to Mars in 3 days, or a larger craft on a trip that would
take about a month.
But we’d need a giant, square laser array that’s 10 kilometers long on each side -- which
presents some obvious problems.
Getting stuff to space is expensive, let alone 100 square kilometers’ worth of high-powered
laser equipment.
And even if we did get everything to the right spot, it would be incredibly difficult to
assemble.
Building a laser sail for this super-fast trip to Mars would also be tough.
According to the researchers, it would have to be only a micron thick -- that’s a thousandth
of a millimeter.
But to work properly, that whisper-thin laser sail would have to weigh about as much as
the spaceship itself!
Meaning that it would have to be a huge, thin sail, but strong enough to be stable while
the ship is moving ridiculously fast.
And … we also have no idea how to slow the spacecraft down once it gets to wherever it’s
going.
So if we’re talking about sending ships to Mars in 3 days, we’re probably getting
ahead of ourselves a little bit here.
Really, the first step to making this research a reality is building a much smaller set of
lasers.
The team’s plan -- assuming NASA chooses to move forward with their idea -- is to start
with a laser array that’s only one meter square.
Then we’d just keep building bigger sets of lasers, until we eventually figured out
how to build one that’s 10 kilometers on a side.
Then, we could use that to launch what are known as wafer sats.
These miniature spacecraft would weigh no more than a gram, but they’d have sensors,
a power source, teeny-tiny thrusters, and communications equipment.
That giant set of lasers could accelerate these wafer-sats to about 25% of the speed
of light, sending them light-years away, where they could tell us all about interstellar
space and exoplanets.
They might even be able to reach the nearby star system Alpha Centauri only 15 years after
they launch.
So, there’s still a huge amount of research, technology development, and testing needed
before we use lasers to propel any sort of spaceship -- even a little wafer one.
And it’s going to be a very long time before we’re zooming over to Mars in just a few
days.
But it probably is possible.
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