[nostrademons]

> My limited understanding is they are avoiding an IPO because their financials are not up to snuff.

My understanding is that they're avoiding an IPO because it would jeopardize SpaceX's mission of getting to Mars. When they're privately held, Musk can vet investors to be sure that they're aligned with SpaceX's mission, or ensure that they're powerless enough that they can't make problems if they're not (eg. no board seats). When they're publicly held, things like unveiling Starship when NASA is pissed about Crew Dragon not being ready yet is just inviting a shareholder lawsuit. Wall Street tends to take a dim view of long-term highly risky bets, and going to Mars with privately funded R&D is precisely that.

[hilbertseries]

I highly doubt going to Mars is the reason space x is still private. Given that astronauts have shown somewhat serious issues after being in space for six months, it’s unlikely the human body could survive three years in zero gravity without serious damage. Which means that a space flight to Mars would also require some form of artificial gravity and so for our lifetimes, is likely going to remain science fiction.

No, Musk is going to keep SpaceX private because he hates public oversight, like the kind he’s gotten with Tesla.

[ceejayoz]

Where'd you get the idea that a Mars trip is going to involve three years of zero-G?

A Hohmann transfer orbit (minimum energy) will get you there in nine months. SpaceX is targeting a higher energy, shorter trip that'll probably wind up being about six months each way (with Mars gravity in the middle).

[semi-extrinsic]

I agree with you that the no-gravity part is likely doable with an acceptable risk.

What I haven't seen are actual solutions for how to deal with the radiation. Yes, there is ongoing research from NASA, ESA, JAXA and others, and lots of interesting proposals like hydrogenated boron nanotubes, electromagnetic force fields, lithium shields etc. But no solutions even close to implementation.

Here's from an ESA blog post on the topic earlier this year:

> As it stands today, we can’t go to Mars due to radiation. It would be impossible to meet acceptable dose limits.

http://esa.int/Science_Exploration/Human_and_Robotic_Explora...

Are we going to send astronauts who have accepted they will likely die from the mission? Is getting a person quickly to mars worth such a suicide trip?

The final issue I believe will be a hurdle is the psychology. It's one thing sending people to the moon for a few days, or to the ISS for half a yesr where they can look out the window at Earth every day. But I'm not sure the human mind is going to stand up well to the type of extreme isolation a trip to Mars requires. It's certainly never been tested before.

[ceejayoz]

> What I haven't seen are actual solutions for how to deal with the radiation.

https://www.nytimes.com/2013/05/31/science/space/data-show-h...

"According to the National Cancer Institute, the lifetime risk of dying from cancer is 21 percent; the two-thirds of a sievert from a round-trip mission to Mars would raise that risk by three percentage points, to 24 percent."

Mars advocates like Zubrin argue the "acceptable dose limits" are exceedingly conservative, and that NASA willingly permitted far more dangerous operations (like the Shuttle) than radiation incurs.

> It's certainly never been tested before.

Sure it has. https://en.wikipedia.org/wiki/MARS-500

[kiba]

I don't think you understand space and space technology well enough to evaluate SpaceX if you think there's no way to 'generate' gravity in space without using space magic gravity generation.

[nostrademons]

Or physics - how to generate artificial gravity on an accelerating spaceship is literally an intro physics homework question.

[hilbertseries]

We've currently never built a manned space ship for month long travels in outer space. We've never built a space ship that uses centrifugal force to simulate gravity and done longitudinal studies to verify that this doesn't have an adverse impact on Humans. SpaceX is has a market capitalization of 33.3 Billion. SpaceX which was founded 17 years ago has never had a manned flight. SpaceX has also never had a flight leave the atmosphere so far. But yes, it's entirely believable that they will go to Mars in our lifetime.

[ceejayoz]

> SpaceX has also never had a flight leave the atmosphere so far.

Uh, what?

[FireBeyond]

I can only assume he meant a manned flight.