Interstellar spacecraft: Our nearest star is closer than you think

5 min readSep 23, 2019

How can we explore our neighboring stars within the next few decades?

I’m glad you asked! One of the most realistic ways that we could propel a spacecraft to the nearest star, Alpha Centauri, at a reasonable speed of 20 years (With Voyager 1, Nasa’s fastest spacecraft, it will take 40,000 years to cover this distance.) is through photonic propulsion. Photonic propulsion uses photons and a reflective surface to move spacecraft. Photons are particles that make-up light. Yes, light can be used to move things. Photons do not have any mass, but they generate momentum. When these light particles hit a reflective surface, the particles bounce back from the surface and cause said surface to move. Another way to envision this is with a wall on a set of wheels and a basketball; if you throw a basketball at the wheel-bound wall, the ball will bounce back to you and the wall will move. So when we concentrate light onto the spacecraft for a certain amount of time (Millions of basketballs!), it will eventually reach the required speeds needed (25% the speed of light) to reach Alpha Centauri within 20 years.

Proof of concept: https://www.youtube.com/watch?v=QICCrlmBjvY

Diagram of Laser-Powered spacecraft for exploring Mars.

The spacecraft itself:

Technical hurdles that we need to consider:

Power (Easier to solve: The spacecraft needs power outside of our solar system. This can be done with solar or nuclear batteries.)
Smaller Electronics (Easier to solve: Since this idea has been around since the '80s, our modern electronics should be small enough to jump over this one.)
Weight…

But why weight? Since there is no gravity in space, why should weight matter?

Well weight, according to our good friend Isaac Newton, is a factor in his Second Law of Motion. According to his law (Force = Mass * Acceleration), heavier spacecraft require more energy (Force) to gain acceleration. So as long as the spacecraft is light enough to accelerate and wide enough to catch the energy that helps it gain momentum, we should be able to reach the desired speed. There’s also no resistance in deep space, so a spacecraft can retain it’s speed for as long as it wants!

WELL JEEZ! How much energy does the laser require to move the probe?

Quite a bit of energy is needed to power the giant laser (100 Gigawatts is equivalent to 72 million tons of coal… OH GOD!), but we could build hundreds or thousands of lasers on earth’s surface to divide the power requirement for the space probe. For example, 100 1-gigawatt lasers, or 100,000 1-megawatt lasers, etc.

**LOOK AT ALL THE LASERS!!! YES, THE ALIEN TOO, BUT LOOK AT THE LASERS!!!**

We are now traveling faster than any spacecraft has traveled before. But how’s the spacecraft going to change direction or slow down enough to get a decent picture?

A brief history of interstellar space travel:

Yup, we have already left our solar system about 5 times (HOPEFULLY 6 WITHIN THE NEXT 20 YEARS!) at the time this article was written.

Interstellar spacecraft that we know of (from fastest to slowest):

Voyager 1 (17 KILOMETERS A SECOND!!!)
Voyager 2 (15 KILOMETERS A SECOND!!!)
New Horizons (14 KILOMETERS A SECOND!!!)
Pioneer 10 (12 KILOMETERS A SECOND!!!)
Pioneer 11 (11 KILOMETERS A SECOND!!!)

**JUST THINK OF THE FAR RIGHT… 7,000 TIMES THAT.**

Compared to 25% the speed of light, (74,948 KILOMETERS PER SECOND… OH MY, 7,000 TIMES THE SPEED… WOW!!!) this is nothing.

What all of our modern interstellar explorers had in common: No lasers, just a set of chemical tubes that went boom and some gravity.

Gravity was probably the largest factor as it enabled all of these spacecraft to achieve their speeds to escape the solar system and accomplish stuff like this:

“Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there-on a mote of dust suspended in a sunbeam. — **Carl Sagan** **(Earth photo, 40.5 AU by Voyager 1, 1990)**

**YES, PLUTO HAS COLOR!!! Surprised yet? (Taken by New Horizons space probe in 2015)**

How gravity assists work:

So we now know that gravity can be used to speed up spacecraft and change their direction. But how did the gravity speed up these craft in the first place? When the Voyager probes approached planets with large amounts of gravity such as Jupiter, they would commence a fly-by. As the Voyager space probes become overtaken by Jupiter’s gravity, they suddenly change in direction. When the sudden change in direction is applied, a large amount of velocity (A positive change in speed and direction) is added to the space craft’s movement.

If you didn’t notice, a negative change in speed can also be made!!!

That’s right, our probe could also be slowed down while changing direction! On a hill, you can run down and gain momentum, but on the way up you will have the counteracting effect of slowing down. As we slow down, our spacecraft will also change direction and become caught by the next star or heavenly body. The idea is that the craft will catch a ride on each pod of gravity until it eventually makes its way across our neighboring solar system.

Now all we need to do is get Alpha Centauri’s stars and planets to say cheese.