[thelambentonion]

I'd encourage everyone reading the AMA to take a lot of what Musk is saying with a grain of salt. The Interplanetary Transport System (ITS) is a wildly ambitious project that is attempting to accomplish more things in a shorter period of time than the Apollo program (and on a substantially smaller budget to boot).

Check out Robert Zubrin's article, which presents a much more salient critique of SpaceX's current plans than I could [0].

[0] http://www.thenewatlantis.com/publications/colonizing-mars

[manicdee]

Zubrin starts by misrepresenting the Spaceship as two inseparable stages, and overestimates the mass of the motors by a factor of three.

He then claims that ISRU is impractical due to hypothetical resource constraints.

Zubrin then claims that the Spaceship is a "habitat" that should only go one way. SpaceX has decided that the habitat should be built on Mars from indigenous materials. A one-way Spaceship is vastly more expensive than a reusable one.

Zubrin dismisses fast transit to Mars entirely on the basis of not being a free-return trajectory with a symmetric time span (6 months out, 6 months back). The free return is only if use if the spacecraft is not going to land. The number of failure modes where the Spaceship can't land on Mars but can still manoeuvre into Earth orbit are very small. The Spaceship is designed for aerobraking and landing, not orbital capture.

He then goes on to criticise the four-month express crew transfer as having no payload capacity, when the intent was only to show that rapid crew transfer is possible. The benefit of the shorter trip is less exposure to harmful radiation. The assumption is that sufficient resources already exist on Mars to house and feed the new arrivals.

A multi-component system as proposed by Zubrin with an Earth-Mars transport with separate craft for leaving Earth and landing on Mars adds far more complexity, more moving parts, more ways for things to fail.

The SpaceX monolithic approach us safer simply because there are fewer things that can go wrong.

Zubrin's supposed improvements are to split the Spaceship into propulsion and habitation modules, with the habitation module having its own vacuum engines for Mars intercept and landing, and then some way of splitting those motors away from the habitat upon landing so they can be cannibalised or returned to Earth.

Which is to say, Zubrin has spent so much time evangelising Mars Direct that he no longer considers any other option as valid.

SpaceX are pursuing the engineering goal of sending large payloads to Mars and back to Earth with best use of resources. They want the incremental cost of moving people and things around the solar system to be as low as possible. Zubrin wants a single transit to be as low cost as possible, meaning use of disposable spacecraft, meaning higher costs overall.

[1457389]

Zubrin thinks we can get to Mars with current tech. He has thought that for decades, and his outreach efforts was one of the things that inspired Musk in the first place. He disagrees with the timespan for colonization, yes, but his post here is mainly around optimizations for Musk's proposal, not an outright rejection:

>Still, with some corrections, a system using the core concepts Musk laid out could be made attractive — not just as an imaginative concept for the colonization of Mars, but as a means of meeting the nearer-at-hand challenge of enabling human expeditions to the planet.

[M_Grey]

It's good to see that the initial nearly religious fervor has worn off, and comments like yours can survive the voting process here. There are a number of issues with the "colony" concept, even beyond that excellent article, but until recently such a point was met with some version of fury. The general theme seems to have been that getting people excited, even with empty promises, was somehow virtuous and might lead to something good (for parties other than Musk's and SpaceX's bottom line).

[pm]

I think people getting excited about space and space travel again is a good thing. It's the first step to getting people involved again, even if only to remember what we're capable of as a species, despite all our flaws and all the other problems we've yet to solve. Whether you agree with Musk's methods or not, I enjoy living in a time where we dream about the possibilities of new worlds, rather than reminiscing about a golden age of space travel long past.

[M_Grey]

I think that's a little sad, because it implicitly gives up on the notion of real progress in favor of PR and imagination. I'm excited about SpaceX, but not because of their "Mars Colony" PR. I don't think the situation is so dire that we need to suspend our skepticism and become mindless cheerleaders in the name of "dreams".

[kitsunesoba]

It's definitely a good idea to keep expectations grounded, but at the same time there's no reason why the current mind-numbingly slow crawl that space travel has come to should be taken as some kind of rule or requirement or inevitability. Musk's timeframes are overwhelmingly optimistic at best, but the current pace of development is also unacceptably slow.

[M_Grey]

...And when people realize that this was PR and hype, you think there won't be a cynical backlash?

[aptwebapps]

I think that's a bit of a false dichotomy. I don't think some portion of the public being swayed by PR is going to stop SpaceX (or other entities) from making real progress. Musk is definitely not giving up on that notion.

If you just mean that it's sad that people need this kind of hyperbole to get excited about space, well, different strokes for different folks. You don't need it, they do.

[M_Grey]

The thing about false hope, is that it doesn't last, and in its wake you get cynicism and apathy. In the long run, lying to gin up excitement backfires.

[pm]

Agreed, what's required is solid discourse, to fill in the endless details of a plan that will no doubt take longer than expected. However, the broad strokes are there, the goals have been set, and action is being taken. This is what makes me excited - not SpaceX, not Elon Musk, but that someone is trying to make commonplace space travel in my lifetime a possibility.

[nickik]

What I don't understand about people like you is how you can still talk this crap.

Musk has done incredible stuff already, he has shown multiple prototypes of what they are building. Sure, maybe they will fail, but I don't understand how you can call everything "empty promises".

He promised a orbital rocket landing, he delivered.

He promised a reusable rocket, this he is very close to as a used rocket was already did multiple full duration test fires.

He promised a new engine, he shows this new engine and its first tests.

He actually delivered a prototype of a carbon-fiber tank that literally nobody in the community was expecting.

Will people like you only be happy if there are 1 Million people living on Mars?

It seems to me that you have never read the actual communication and you are just going of on statements by third parties.

[M_Grey]

It seems to me that you've decided I fit some kind of preconceived archetype "people like you", which largely seems to consist of a lack of faith. "He's done X, why not Y?" Because when he promised X, he did so with a plan which accounted for the issues inherent in X. This is not the case for the orders-of-magnitude more ambitious Y.

"He's done incredible stuff, so take him at his word" is the kind of nearly religious suspension of logic I'm talking about, mixed with equally unfortunate hostility at the "unbelievers" (aka 'people like me'). That you end with a note of incredulity at the notion that I could have arrived at my viewpoints while fully informed walks the fine line between insulting me, and insulting yourself.

[verytrivial]

I would be most interested hearing exactly how many catastrophic launch failures the project is expecting to sustain whilst still going forward. SpaceX today has a somewhat above average launch success rate but the last two failures got the markets into a tizz, which is very significant here if this is meant to be at least a partially commercial venture.