SpaceX CEO Elon Musk has now given four presentations about his company’s Starship rocket, but all of those updates mostly focused on the vehicle’s external stats. Musk has barely touched on the technologies needed to keep people alive and healthy while on Starship — technologies that need to be developed relatively soon if the spacecraft has any hope of carrying people to deep-space destinations like the Moon and Mars in the near future.

The specs that Musk has given for Starship are definitely impressive for any rocket. The vehicle will supposedly tower over 165 feet (50 meters) tall, with a diameter of 30 feet (nine meters). At his latest presentation in Boca Chica, Texas, Musk claimed the final version of the rocket will be able to launch 150 tons to Earth orbit, rivaling the capacity of the Saturn V rocket that took humans to the Moon. That would easily make Starship the most powerful rocket in the world when it becomes operational.

if SpaceX wants to put people on Starship, things become much more complicated

But if SpaceX wants to put people on Starship for an extended period of time, things become much more complicated. Life support systems add weight and complexity to the vehicle. Astronauts need places to exercise and sleep, air to breathe, and water to drink. And if Starship is supposed to start a lunar base, which Musk has proposed numerous times, then the higher radiation environment on the Moon will require advanced forms of shielding.

All of these problems will be heightened when sending crew to Musk’s dream destination: Mars. Thanks to the long distance, astronauts won’t get resupply missions for years, and they will have communication delays with Earth. Radiation exposure will become even more severe, and it’s unclear how that will affect the human body. “It’s extremely naive to think that we can send people to Mars within even the next decade,” Dorit Donoviel, director for the Translational Research Institute for Space Health, which is partnered with NASA, tells The Verge. “Realistically, it’s going to be at least 10 years or more before we feel comfortable doing that.”

Musk has addressed life support and human health in his Starship talks before, but only briefly. In his most recent presentation, the SpaceX CEO was asked twice about the types of life support systems that Starship would use. “I don’t think it’s actually super hard to do that, relative to the spacecraft itself,” Musk said. “The life support system is pretty straightforward.”

Straightforward complexity

A life support system encompasses all of the things needed for humans to fundamentally survive here on Earth. “Anything that keeps the crew alive and functioning and keeps that environment safe for them is really the life support system,” John Cover, the deputy system manager for the International Space Station’s life support system at NASA, tells The Verge. The most basic necessity is the atmosphere. Life support systems must supply the right mixture of gases for people to breathe and remove carbon dioxide from the air before it builds up to a dangerous amount. The right temperatures and atmospheric pressure have to be maintained. Astronauts will need drinking water, along with a place for water waste to go.

SpaceX already has some experience with life support systems

SpaceX already has some experience with life support systems with its new crew capsule called Crew Dragon, which is designed to take astronauts to the International Space Station. However, providing life support for a short trip to orbit is much different than one that’s needed to keep people alive for weeks and months in deep space. For one thing, both oxygen and water can be supplied in finite containers on a trip to orbit — just enough to get people to their long-term destination. On the International Space Station, though, where people live for months at a time, a “regenerative” system is in place for things like oxygen and water, meaning they’re recycled in a closed-loop system. Urine and sweat are recycled and turned back into drinking water, while some of the water is split apart into oxygen and hydrogen— in a process known as electrolysis — so that people can breathe.

Musk did say that the life support systems on Starship would be regenerative. But life support systems tend to be heavy and complex, changing how the vehicle would operate. And figuring out how to keep people safe in emergency situations is also key. “Once you start talking about putting crew in there, you need to start talking about the hazards and how those hazards unfold,” says Cover of turning a cargo ship into a crewed ship. He also notes that crew can get injured or killed if something goes wrong. “So there’s quite a bit more work that has to go into place.”

Musk claims that people will be able to fly to space on Starship as early as next year, which means figuring out the life support system should be a priority in the months ahead. The technology exists today, so it is possible that they could hit their ambitious timeline. But SpaceX does not have much documented experience with regenerative life support systems. The Crew Dragon’s life support system is not regenerative, and even so, no people have actually flown on the vehicle yet.

Staying alive on the lunar surface

Things become even hairier if SpaceX wants to establish a long-term presence on the Moon. For one thing, the longer people live away from Earth, the more exposure they have to deep-space radiation and galactic cosmic rays. These are highly energetic particles that emanate from the Sun or distant sources outside our galaxy. They can pierce through skin and other materials, causing damage to biological tissues. The Earth’s atmosphere and magnetic field help shield us from the majority of this radiation, but out in deep space and on the Moon, that protection goes away.

The Apollo astronauts only had small increases in exposure since they were on the Moon for such short periods of time. Living on the Moon will entail a completely different level of exposure, and if the Sun has a major solar flare, it could send a large dose of radiation toward the Moon. NASA and researchers suspect that heightened exposure to radiation could lead to damage to the central nervous system and affect brain function, according to Donoviel. But ultimately, we don’t know because we haven’t sent people into deep space for long periods of time.

“We don’t have a clue about radiation.”

“We don’t have a clue about radiation,” says Donoviel. “This is really a concern of mine. The way NASA handles a lot of the radiation work has been a lot of predictions. They’re trying to keep people from crossing over a certain limit. That’s the way they’re handling it. But I don’t know if that’s going to work. I think that we’re grossly underestimating the effects.”

In reality, some kind of radiation shielding will be needed, and Starship’s stainless steel exterior may not be enough to protect astronauts for a long time on the surface. Experts have proposed lining long-term lunar habitats with water or ice to slow down these particles, but there are some elements within cosmic rays — known as heavy ions — that might be able to pierce through even that. Perhaps the best option is creating habitats that are covered in lunar dirt, which will require lots of excavation and construction equipment. Musk hinted in his latest presentation that SpaceX might do this, too. But if that’s the case, decisions on that need to be made well in advance before founding any lunar city.

“You have to make all these really basic architectural questions,” Phil Metzger, a planetary physicist at the University of Central Florida, tells The Verge. “After you’ve made the basic questions, then you say, ‘Okay, these technologies are already mature. We can start building flight hardware and other technologies are not quite mature yet.’”

“You have to make all these really basic architectural questions.”

Mining equipment also becomes critical if this lunar base needs to be self-sustainable. Resupply missions to the Moon will be much more difficult than those sent to the International Space Station in Earth’s orbit, as the Moon is days away in transit time. Astronauts at a Moon base will need to rely on the resources around them, such as dirt for construction and potentially water ice to use for drinking and to turn into fuel. All of the equipment to mine this could be brought to the Moon by Starship, but it’s unclear what they would look like since no one has really operated such equipment on the Moon before.

“Here on the Earth, to set up a mine, it can take 20 years — and that’s on the Earth,” says Metzger. “So when you talk about setting up a mine on the Moon, it’s harder, especially because we have less understanding of the resource, and we have zero experience in doing mining operations in that environment.”

Lingering problems

There are still many other questions that need to be addressed. For one thing, experts don’t know if humans can live and be healthy at the low gravity environment of the Moon. Our bones and muscles are accustomed to Earth’s gravity, but these tissues might deteriorate more quickly on the Moon, which has one-sixth the gravity of our planet. Exercise could mitigate that, but researchers ultimately don’t know if that would be enough or what kind of equipment is needed. There’s also just the basic comfort of people to think about. Design decisions like lighting and the angle of chairs during launch can have impacts on how people feel and behave. Musk has talked about sending 100 people up in Starship, with each person getting about 10 cubic meters of space. “Especially in like a zero-g situation, that’s actually quite a lot of room,” claims Musk.

These problems are really just the tip of the iceberg

But that may turn out to not be enough in the grand scheme of things, negatively affecting people’s mental states. “The behavioral aspects are a major concern, and you can’t always predict how people are going to react being so far away from Earth without direct communication,” says Donoviel.

These problems are really just the tip of the iceberg, too. So much more will need to be addressed just to start a lunar base, let alone send people to Mars indefinitely. Ultimately, SpaceX can opt to tackle these problems once Starship development is complete, but that will prolong when people will actually get to fly to the Moon or on Starship at all. “We try to engage the commercial spaceflight companies on thinking about the humans, and they’re just not there yet,” says Donoviel. “They’re still trying to solve the big problems on how to get them there.”

Musk says only 5 percent of SpaceX’s resources are being used to develop Starship at the moment, which may explain why the rocket is the sole focus. At some point, the humans will need to be addressed, though. It’s just a matter of when.