GUADALAJARA, Mexico--Elon Musk founded SpaceX in 2002 with the goal of colonizing Mars. And for months he’d been saying he’d finally provide details of his plans at the International Astronautical Congress here.

In an event that that had the feel of a Apple product unveiling, with delirious fans who rushed into the conference hall as soon as the doors opened, he spoke for more than an hour about a new, immensely powerful rocket, powered by a staggering 42 engines and a spacecraft designed to fly 100 passengers, or more, to Mars and even destinations beyond.

It is a bold endeavor that drew a range of reaction, especially given that SpaceX has yet to ever fly humans, has had two of its rockets blow up in just over a year and has not yet launched the rockets that it says would get people to Mars.

Still, Bill Nye, chief executive of the Planetary Society, praised Musk, calling him “Iron Man,” and saying his plan was “very cool.” But he said he worried about the possibility of “breathing and spitting” humans contaminating Mars and interfering with any life that may already be there. (In a press conference after his presentation, Musk said he didn’t think protecting Mars would be that difficult.)

Gentry Lee, the chief engineer for Solar System Exploration at NASA’s Jet Propulsion Laboratory and a science fiction writer, told The Post's Joel Achenbach that Musk’s plan “would be a gigantic human engineering endeavor, greater in scope, scale, and cost than the Manhattan Project.” To be successful it “would have to develop and infuse new technologies at a much faster rate than we have ever achieved before on any project.”

Scott Pace, the director of George Washington University’s Space Policy Center, said he was skeptical.

“His approach is plausible but not probable,” he said. “The resources required are beyond those of individual or group of individuals, no matter how wealthy they may be. It is unclear however why any governments or corporations would underwrite the massive effort described.”

But let’s give Musk the floor and hear what he has to say. Here’s an edited transcript of his remarks:

Musk on his long-term goals for space:

“What I really want to achieve here is to make Mars seem possible, make it seem as though it's something that we can do in our lifetimes and that you can go. And is there really a way that anyone can go if they wanted to? I think that's really the important thing.

“So, I mean, first of all, why go anywhere? Right? I think there are really two fundamental paths. History is going to bifurcate along two directions. One path is we stay on Earth forever and then there will be some eventual extinction event. I don't have an immediate doomsday prophecy, but eventually history suggests there will be some doomsday event. The alternative is to become a space-faring civilization and a multi-planet species, which I hope you agree that is the right way to go.”

Why it’s better to colonize Mars over the Moon:

“Just to give some comparison between the two planets, there are actually -- they're remarkably close in a lot of ways. In fact, we now believe that early Mars was a lot like Earth. And, in fact, if we could warm Mars up, we would, once again, have a thick -- a thick atmosphere and liquid oceans.

“So, where things are right now, Mars is about half again as far from the sun as Earth. So it has decent sunlight. It's a little cold, but we can warm it up. It has a very helpful atmosphere which, in the case of Mars being primarily CO2 with some nitrogen and argon and a few other trace elements, means that we can grow plants on Mars just by compressing the atmosphere. And it has nitrogen, too, which is also very important for growing plants.

“It will be quite fun to be on Mars, because you will have gravity which is about 37 percent that of Earth, so you will be able to lift heavy things and bound around and have a lot of fun. And the day is remarkably close to that of Earth. So we just need to change that bottom row, because currently we have 7 billion people on Earth and zero on Mars.”

On how his Mars plan is like “Battlestar Galactica”:

“Now, over time there would be many spaceships. You would ultimately have, I think, upwards of a thousand or more spaceships waiting in orbit. And so the Mars colonial fleet would depart en masse. Kind of like “Battlestar Galactica,” if you have seen that thing. Good show. So it's a bit like that.”

On why it’ll be "fun and exciting" to fly to Mars:

“I just want to give you a sense of what it would feel like to actually be in the spaceship. I mean, in order to make it appealing and increase that portion of the Venn diagram of people who actually want to go, it's got to be really fun and exciting, and it can't feel cramped or boring. But the crew compartment or the occupant compartment is set up so that you can do zero-G games, float around. It would be like movies, lecture halls, cabins, a restaurant. It will be, like, really fun to go. You are going to have a great time.”

On how the cost of a ticket to Mars could drop below $100,000:

“If we can get the cost of moving to Mars to be roughly equivalent to a median house price in the U.S., which is around $200,000, then I think the probability of establishing a self-sustaining civilization is very high...So we're right now estimating about $140,000 per ton to the trip to Mars. So if a person plus their luggage is less than that, take into account food consumption and life support, then we think that the cost of moving to Mars ultimately could drop below $100,000.”

On his problems with deadlines, affinity for mariachi bands and the early days of SpaceX:

“Time lines. Not the best at this sort of thing. But just to show you where we started off. In 2002, SpaceX basically consisted of carpet and a mariachi band. That was it. That's all of SpaceX in 2002. As you can see, I'm a dancing machine. And, yeah, I believe in kicking off celebratory events with mariachi bands. I really like mariachi bands.

“But that was what we started off with in 2002. And really, I mean, I thought we had maybe a 10 percent chance of doing anything, of even getting a rocket to orbit, let alone getting beyond that and taking Mars seriously. But I came to the conclusion if there wasn't some new entrant into the space arena with a strong ideological motivation, then it didn't seem like we were on a trajectory to ever be a space-faring civilization and be out there among the stars. Because, you know, in '69 we were able to go to the moon and the space shuttle could get to low-Earth orbit, and then after the space shuttle got retired.”

On how the first people going to Mars might die:

“Well, I think the first journey to Mars is going to be really very dangerous. The risk of fatality will be high. There's just no way around it. So I would not suggest sending children. It would be basically are you prepared to die, then if that's okay, then, you know, you're a candidate for going.

“But really this is -- this is less about, like, you know, who goes there first or -- it's -- the thing that really matters is making a self-sustaining civilization on Mars as fast as possible.”

On how what SpaceX is doing is a lot like the early days of the United States railroad system:

“The goal of SpaceX is really to build the transport system. It's like building the Union Pacific Railroad. And once -- once that transport system is built, then there's a tremendous opportunity for anyone who wants to go to Mars and create something new or build the foundations of a new planet. So it's like who wants to sort of be, you know, among the founding members of a new planet and, like I said, build everything from iron refineries to the first pizza joint. You know, we will want them all.

“And then things on Mars that people can't even imagine today that might be unique or would be unique to Mars. And -- but that's really where a tremendous amount of entrepreneurship and talent would flourish. Just as happened in California when the Union Pacific Railroad was completed. And when they were building the Union Pacific, a lot of people said, ‘Well, that's a super-dumb idea because there's no -- you know, hardly anybody lives in California.’ But now, I mean, today, [it's] the U.S. epicenter of technology development and entertainment. And it's the biggest state in the nation. But you need that transport link. If you can't get there, then none of those opportunities exist. Our goal is just to make sure you can get there.”

On why the return trip to Earth will be free:

“I think it's pretty important to give people the option of returning. The number of people who would be willing to move to Mars is much greater if they know that they have the option of returning, even if they never actually return. I mean, most of the people that went to the original English colonies in North America, they never returned to Europe, even once.

“But some did. And just knowing that if you don't like it there, that you can come back, I think makes a big difference in people's willingness to go there in the first place.

“In any case, we need the spaceship back. So it's coming. You can jump onboard or not. It's cool. You get a free return trip, if you want.”

See the strangest questions asked to Elon Musk after SpaceX's presentation of their new Mars colonization rocket.