NASA wants to go to Mars in the 2030s, but there are some technical challenges it’ll have to address. Such as landing.

Engineers know how to land roughly a ton of equipment on Mars — that’s how much the Curiosity Mars rover weighs. But a much more robust landing system will be needed for a manned space vehicle to touch down, said Josh Hopkins, space exploration architect at Lockheed Martin Space Systems. Lockheed Martin is a NASA contractor currently working on the Orion crew vehicle.

“Right now we know how to land a small car on Mars,” Hopkins said, “and we need to learn how to land a house.”

Technologies used to land payloads in robotic exploration pale in comparison to what will be needed to land a two story house, said Bobby Braun, a professor at Georgia Institute of Technology, who was chief technologist at NASA in 2010 and 2011.

To land a payload that’s 40 times the size of the Curiosity Mars rover, a parachute would have to be substantially larger and deploy at a higher velocity, Braun said.

But the bigger the parachute the longer it takes to open, and on Mars, time is valuable because of the planet’s thin atmosphere, he said.

Using the same technology as robotic missions would result in hitting the ground before the parachute even opens, he said. And if it opened at a higher velocity, a parachute would burn up and rip apart.

There’s also the danger of exposure to radiation during the couple of years that a human mission to Mars is expected to take, as well as the several months it would take the crew just to reach the neighboring planet.

Help couldn’t be shuttled over if something goes awry, and radio communication would be delayed, even at the speed of light.

“We need to build systems that are more reliable and don’t require as many replacement parts,” Braun said.

And once the new Space Launch System gets astronauts to Mars, a secondary propulsion capability would be needed to maneuver around the planet.

And with existing technology, Braun said, “You’d literally need rocket after rocket after rocket just to launch all the fuel.”