Forget the moon. The next giant leap for mankind could be building a habitat on Mars.
The fourth planet from the sun may be cold -- Martian winters can reach -190 degrees Fahrenheit
(-87 degrees Celsius) -- full of deserts and lacking in oxygen, but for Behrokh Khoshnevis
it's humans' next destination.
The pioneering professor in engineering at the University of Southern California has been working with NASA on the possibility of building a colony on Mars since 2011.
In 2004, Khoshnevis unveiled a revolutionary 3D-printing method dubbed Contour Crafting
(CC), which made it possible to print a 2,500-square-foot building in less than a day on Earth.
Then, in 2016 he took first prize in the NASA In-Situ Materials Challenge
, for Selective Separation Sintering -- a 3D-printing process that makes use of powder-like materials found on Mars and works in zero-gravity conditions.
Here, Khoshnevis tells CNN why he believes humans will soon build on Mars.
You're not the first person to suggest building on Mars. What makes your plans better?
When I read about the moon and Mars -- the conditions, the habitats -- I realized that almost all of the existing ideas involved taking materials and components from Earth and building with those materials. Taking 1 kilogram of material from Earth to the moon would cost hundreds of thousands dollars. It was clear to me that these ideas were not economically viable.
Other approaches, like taking inflatables, also wouldn't work. Inflatables are made of polymeric material, like vinyl, so they won't survive long because the radiation on Mars is pretty intense. Radiation is the enemy of polymers, causing it to become weak and fragile.
The Space Exploration Architecture and Clouds Architecture Office took home first prize for their "ice House" design in NASA's 2015 3D-Printed Habitat Challenge. Credit: Space Exploration Architecture and Clouds Architecture Office
So what did you propose to NASA?
(I wanted) to 3D-print structures using materials on the moon, and later on Mars. With my own pocket money, I did some experiments, and purchased materials that looked very similar to the lunar and Martian materials, both in terms of the shapes, and percentage of different oxides -- all the characteristics were comparable.
I built some very primitive things, melting the materials to see if I could use the heat to change the sand into rock. I wanted to see if the stimulants could be melted and extruded, and if I could use them in my 3D printing idea.
Then I wrote a proposal to NASA to build structures and infrastructure on other planets, entirely using in situ material, so we wouldn't be taking material from earth.
What is the biggest barrier to doing this?
Getting the technology to Mars. We will have to place the construction machines inside the payload compartment of a rocket. For that, we have to be mindful of the size. It can't be too large or too heavy. Otherwise, it would need bigger rockets -- and the cost of building such a rocket would be pretty significant.
But once the compartment has landed on another planet, then its contents can start working autonomously. We don't want to send human astronauts as construction workers.
More than 165 submissions were received and the winning team took home $25,000 for their ice house design, pictured here. Credit: Space Exploration Architecture and Clouds Architecture Office
In space, the environments are so hostile to humans that robotics will have to play a major role in preparing those places for the future of humanity.
Of course, humans will try to control (robotic) construction on Mars from Earth. And in the case of the moon, some control is possible -- we can tell the robotics what to do. But on Mars, because the distance from Earth is so far (401 million km apart, at their greatest opposing positions) you don't have real-time controls. There is a big delay.
It will be like moving a joystick on a video game, but it takes 8 minutes for the cursor to move.
Before we start building, what will the robots need to set up?
On Earth, there would be people to install the 3D printers, connect them to an energy line of some sort -- like a power grid. But in space, it all has to be done autonomously.
So you'd need a source of power to be installed (by robots), like solar panels. And to use Martian materials, there has to be some kind of processing plant to create the materials. Then you need a way to transport materials to the machine and an automated machine has to print the material into the shape you want.
Then basic infrastructure such as landing pads, roads, radiation protection walls and hangars can be built. Human habitats can follow next.
And that's how you go about colonizing another planet.
Does the weaker gravity on Mars pose a problem?
The gravity on Mars is a third of that on Earth, and the moon's is a sixth. But actually that's beside the point, because my 3D printing processes don't depend on gravity. The printers extrude by force, with pressure -- like a glue gun. A glue gun doesn't need gravity. If you push it out upside down, or downside up, the glue still comes out.
What's the time frame for all this?
I believe building in space is going to become commonplace in less than 50 years. There's an abundance of energy and materials (in space) -- all we have to do is design self-replicating factories and build a lot of objects. In a short time, our capability to manufacture in space will be many times what we can do on Earth.
The design competition challenged participants to propose architectural concepts for 3-D printing on Mars. Team Gamma came in second place for there habitat design, pictured here. Credit: Team Gamma
One reason that NASA and the European Space Agencies are paying attention is that there are more capable rockets that can take bigger payloads and can do more serious work there.
Commercial interest and space tourism is becoming serious, too. Remember that there are people who will pay $10 million per trip to go on a space shuttle, revolve around the earth, and look at the universe from space shuttles.
But wait -- Mars isn't hospitable for humans. Is it realistic to think we can ever live there?
I think that it's a hard initiative but humans are very capable. It's about making it a priority of governments, commercial entities, scientists -- it all depends on how many people work on it in parallel, right?
One hundred years ago ... no one imagined that 300 people would be sitting in a metallic airplane going from one side of the world to the other in a few hours.
It's hard to imagine what we will have 100 years from now, or 50 years from now.
But I have full confidence that we will conquer Mars and this solar system, and even beyond.
This interview has been edited for brevity.