TEDxUCLA 2017: Gravity

Can weak plasma rockets get us to Mars?


About Gary

Gary Li is a third year Ph.D. candidate majoring in Aerospace Engineering at UCLA. As a National Defense Science and Engineering Graduate Fellow, he conducts research on miniature ion thrusters in the UCLA Plasma and Space Propulsion Lab in order to enhance the capabilities of future space missions. He has also performed research on advanced plasma thrusters at both the NASA Jet Propulsion Laboratory and the Air Force Research Lab.


This is me sitting next to the Saturn 5 rocket at the NASA Johnson Space Center. Now I don’t think this picture does the Saturn 5 justice because you can’t see all the amazing things that it’s accomplished. The Saturn 5 was the only rocket to have ever gotten humans to the moon, and it still holds the record as being the most powerful rocket ever built.

What really amazed me was how large this rocket really was in person. I mean it literally took up this entire hangar the size of a football field. But rockets weren’t always this big.

Here’s a look at a few rockets from the past with the Statue of Liberty there to give you a scale for how large rockets really are. Now the smallest rocket here was actually the very first to get us into space.

But just getting to space wasn’t enough for us. We wanted to travel further from the edges of the atmosphere to the moon and beyond. And then we wanted to send heavier cargo, like humans or even space stations. So to meet all of these challenges, we had to build these rockets bigger and stronger over time until eventually we got to the Saturn 5, a rocket so big we could get humans to the moon and back.

Now today we’re looking beyond the moon to an even more ambitious goal: sending humans to Mars. Mars is over two hundred times further away than the moon, so humans will need a massive amount of cargo if they want to survive the journey there and back.

So NASA is now building an even larger rocket called the Space Launch System, or SLS for short. The SLS delivers a second rocket into space which is what ultimately takes you and your cargo to Mars.

Now I hope that you can see that throughout history we’ve just made rockets bigger and stronger to solve all our problems, and it’s worked out pretty well for us so far. We’ve even landed humans on the moon.

But today, we finally hit a ceiling. Even the gigantic SLS won’t be able to deliver the massive amount of cargo that we need for getting humans to Mars. And it’s just not feasible to build a rocket even larger than this.

So what we need to do is think of a different approach, and that’s the focus my talk today. I want to share with you a new rocket technology that’s revolutionizing the way we travel in space.

For the past three years, at the UCLA Plasma & Space Propulsion Lab, I’ve been researching plasma rockets. Plasma rockets are fundamentally different than the conventional ones that we’ve been talking about, which are known as chemical rockets, because instead of creating chemical explosions they create plasmas which are basically gases composed of positively-charged particles called ions and negatively-charged particles called electrons. By shooting these ions out the back, your rocket can move forward very efficiently.

Now the main downside to this technology is that plasma rockets are extremely weak. Now they’re barely strong enough to even lift up a single piece of paper. And that should seem bizarre to you, because you typically associate rockets with being explosive and powerful.

Well plasma rockets are exactly the opposite. They’re so weak they can’t even lift themselves off the surface of the earth, and that means they can only be used in space. That also means we still need the old chemical rockets for launching off the earth.

So with this in mind, how can rockets this weak even be useful to us? Well plasma rockets have one big thing going for them: they can be as much as ten times more fuel efficient than traditional chemical rockets.

So let’s take a second to understand what fuel efficiency really means. I’m sure that most of you already know that a Prius is much more fuel efficient than a big rig. Well plasma rockets are basically the Priuses of space, while these chemical rockets are your big rigs.

But what does this have to do with sending cargo to Mars? Well let’s compare these two rockets. Assume that they’re about the same size and mass, and for simplicity composed of only cargo and fuel. The chemical rocket requires an enormous amount of fuel to deliver a relatively small amount of cargo. I told you in the beginning that this amount wasn’t enough.

Now the plasma rocket, on the other hand, requires less fuel, allowing to take significantly more cargo. And that bonus cargo is exactly what you need if you want to get humans to Mars.

So somehow a weak plasma rocket can deliver more cargo than a powerful chemical rocket. How does that make sense? You don’t normally see people moving cargo with Priuses, right? Well that’s because transportation in space is very different from transportation here on Earth.

In space, you’re not chained to the ground by gravity. You’re basically floating. So a plasma rocket can be weak and still move very heavy objects. And that’s why the plasma rocket’s fuel efficiency is the deciding factor for moving heavier cargo to Mars.

Now moving cargo to Mars isn’t the only thing that plasma rockets can do, of course. They can even get you to Mars faster than a chemical rocket. Now how does that make sense? Because how does a weaker rocket beat a more powerful one in a race? Or in other words, how does the space tortoise beat the hare?

This all goes back to the original idea of fuel efficiency. The chemical rocket requires use up its fuel very quickly so it can give a spacecraft one explosive push to send it to Mars. And this one push does give it the speed that it needs to get there. But the problem is, after you run out of fuel, you still have to cruise through space for at least six months before arriving. And that’s a pretty long time.

Now these plasma rockets, on the other hand, don’t have the same limitations. Because they’re more fuel efficient, they can slowly and steadily push you for a longer period of time. And you can imagine that if you speed up fast enough you can actually pass the chemical rocket and get there even quicker.

And studies have already shown that future plasma rockets could get you there and as little as a few weeks. And we’re well on our way to getting to that point.

But the main idea here is that these chemical rockets that we’re using today have this hard ceiling of a six-month travel time. That’s the best we can do. While these plasma rockets have the potential to break through that ceiling and get there significantly faster. And this means everything for astronauts and future passengers like you or me who might otherwise die of radiation poisoning or even extreme boredom.

Plasma rocket technology is only improving with time. One day, we’ll be able to send heavier spacecraft anywhere in the solar system and get them there faster. So you can just imagine the possibilities.

We can have an interplanetary taxi shuttling humans between the Earth and Mars in just a few weeks, or even send space stations to orbit around the moons of Jupiter where NASA thinks there might be life. And this is just not possible with the chemical rockets we have today. So you can already see that plasma rockets are just beginning to revolutionize the way we travel in space.

And now I want to take a step back so we can look at the bigger picture. Because they’re more fuel efficient, a weak plasma rocket can deliver more cargo than a powerful chemical rocket. And as a bonus, it can even get you to Mars faster.

So I hope that this shows you that a weak rocket can do incredibly useful things in space. And none of this would’ve been possible without a major change in perspective.

Maybe bigger and stronger is not always better. Because in the right situations, sometimes something weak can do unexpectedly powerful things. It could even bring us to Mars.