[LINK] Waitbutwhy article on the history and future of space exploration, SpaceX and more

post by LizzardWizzard · 2015-09-08T11:14:43.067Z · score: 3 (6 votes) · LW · GW · Legacy · 26 comments

Epic work, it's always fascinates me when author explores the topic so deep, that doesn't know where to begin, so finally starts with the whole history of the universe or the existence of human race.

http://waitbutwhy.com/2015/08/how-and-why-spacex-will-colonize-mars.html

 

26 comments

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comment by MarsColony_in10years · 2015-09-08T23:41:30.115Z · score: 3 (3 votes) · LW(p) · GW(p)

I enjoyed the article, and it does a good job explaining SpaceX. However, it glosses over a lot of complicated things.

  • Existential risk and the Fermi paradox: It barely scratches the surface on these as reasons why going to Mars is such an important thing for humanity. I assume most LessWrongers are already familiar.

  • How to actually get to Mars: The $450 Billion price-tag he mentions is significantly inflated. That came from something called the "90 day report", which wound up just being a wish-list for all the big aerospace companies. When it became obvious how ridiculous things were getting, Martin Marietta put together a minimum-viable architecture called Mars Direct, which NASA subsequently used as the basis for their Design Reference Missions 3.0 and up. Basically, it's a $20-30 Billion program, spent over 20 years. Half the money would go toward 10 years of adapting existing technology for the job, and the other half would launch 5 missions with 6 people each spread over another 10 years. That's ~$500 million per person, for a round trip flight and a year on Mars. Using the previous mission's habitat module instead of bringing another one would likely cut the costs further. One of the original leaders of the design team subsequently expanded it into a book, called The Case For Mars, which I highly recommend reading. He starts firmly grounded in the near term, then explores options for eventually expanding into colonization, and discusses how realistic terraforming might be and calculates specifically what it would require based on current climate models.

And, while I'm at it, I'll drop a couple more links:

  • More on SpaceX: If you want to follow the details, /r/SpaceX has a lot of intelligent discussions, and frequently leans toward more technical aspects with minimal fanboying. (People who tend to make overly optimistic statements are expected to have to justify them. For example, a running joke is that Elon's timescales are measured in Mars years, not Earth years, which certainly would explain a lot. SpaceX’s competitor, United Launch Alliance, is looked on much more kindly than Wait But Why makes them out to be.)

  • More on spaceflight in general: http://www.nasaspaceflight.com/ has good technical articles on a range of topics, but they fund the site by restricting some content to "L2" subscribers.

comment by Lumifer · 2015-09-09T01:07:47.364Z · score: 0 (0 votes) · LW(p) · GW(p)

Martin Marietta put together a minimum-viable architecture called Mars Direct

That happened 24 years ago. Also the Zubrin paper gave no cost estimates.

comment by MarsColony_in10years · 2015-09-09T02:38:25.142Z · score: 0 (0 votes) · LW(p) · GW(p)

True on both counts, although I believe the Mars Direct price-tag came from the same agency/group that priced out the 90 day report.

Design Reference Mission 3 was remarkably similar to Mars Direct, but DRM 4 and 5 have grown a bit from the minimalist approach, although they still revolve around In Situ Resource Utilization, just as Mars Direct did. DRM 5 is especially confusing, and it will be a year or two until we see DRM 6, so I actually think the 2011 edition of The Case For Mars is about the best book out there for demonstrating that it can be done. Obviously the rocket he describes was based on minimally altered space shuttle manufacturing capabilities and architecture which no longer exist, but the design principles haven't changed. Zubrin currently endorses a couple versions of Mars Direct based around SLS and/or Falcon Heavy. If you are looking for modern, the most modern Mars architecture I know of is Buzz Aldrin's current version of his Mars Cycler concept. I haven't read his new book yet, but as I understand it that's a grand architecture for a massive project, rather than a minimalist approach. I'm sure we could do it for a fraction of the cost of the Iraq war or the bank bailouts, but that's still many times larger than NASA's current budget. I haven't looked into the political viability, but I suspect that anything over a quarter of a percent of the federal budget isn't likely. I was trying to discuss how it can be done, rather than how to do it best. I'm definitely all in favor of Buzz and Elon if they can make their visions a reality.

comment by Lumifer · 2015-09-09T02:50:07.766Z · score: 0 (0 votes) · LW(p) · GW(p)

I was trying to discuss how it can be done

I don't think there are any serious technical issues that would necessitate inventing something major -- all you need is a lot of engineering. The actual problem is in finding a big pile of money and that, to a large degree, is a function of "What will we get out of it?". The usual answer "But it sooooo cool!" isn't very convincing.

comment by V_V · 2015-09-09T08:23:51.003Z · score: -1 (1 votes) · LW(p) · GW(p)

I don't think there are any serious technical issues that would necessitate inventing something major -- all you need is a lot of engineering.

If I understand correctly, a round trip mission (land, plant a flag, pick up some rocks, take pictures and return) is currently technologically feasible. It's pretty much a matter of scaling up Saturn V / Apollo. The main technical issue is cancer risk from radiation, but I suppose that even if that was ignored there would be no difficulties finding astronauts who would be willing to fly.

A colony that doesn't depend on frequent supply launches, on the other hand, seems beyond current technology.

comment by katydee · 2015-09-07T20:33:31.029Z · score: 3 (5 votes) · LW(p) · GW(p)

This post seems better suited for the Discussion section.

comment by Vladimir_Nesov · 2015-09-08T11:18:46.991Z · score: 2 (2 votes) · LW(p) · GW(p)

Moved to Discussion.

comment by CellBioGuy · 2015-09-07T19:02:32.016Z · score: 3 (3 votes) · LW(p) · GW(p)

Saw this a few weeks ago. The fanboying, overoptimism, and geophysical ignorance causes me great pain.

comment by gwern · 2015-09-08T01:07:31.699Z · score: 9 (9 votes) · LW(p) · GW(p)

Is there any good writeup on the 'geophysical ignorance' anywhere? I checked out some of the comments but they all seemed to be along the lines of 'hydrogen rules, batteries drool', and I can't take hydrogen-car proposals very seriously given Tesla's demonstrated success.

In any case, I read this a few days ago and found it very interesting. He's at least up front about the fanboying, and the overoptimism seems to come from Musk directly (before I read this, I assumed that Musk's talk of going to Mars before 2030 was so much PR intended to keep his mystique alive and stock prices & valuations high and, among other things, deflect attention from the extent to which his companies are still dependent on subsidies; after, I began to take seriously the idea he might actually believe all that), and if nothing else, it seems like this is the closest thing to a comprehensive Musk manifesto - which is interesting all on its own.

comment by CellBioGuy · 2015-09-09T15:24:55.372Z · score: 3 (3 votes) · LW(p) · GW(p)

I was referring to the grand future presented with Mars terraforming in a ridiculously short time, and talking about terraforming the moons of Jupiter and Saturn.

As for Mars terraforming... we can't control a 200 parts per million problem in our own atmosphere with a whole civilization's resources. Mars has at LEAST a 200,000 parts per million problem, and toxic salts in the soil. And it's covered in crust that has never seen much O2 and will react with and suck it out of the air at a pretty good clip unless compensated for by massive biogenic carbon burial rates.

It is utterly beyond me that anyone could ever consider it possible to terraform Ganymede or Titan. They're not made of the kind of stuff that is even solid at human temperatures, they're so cold that according to my calculations boosting the upper ten kilometers of Titan's crust to human-compatible temperatures would take 50,000 years assuming it was pitch-black and did not radiate any heat to space which is physically impossible (its blackbody temperature would be something like 90 kelvin, you need a hell of a greenhouse...), and the sunlight on Ganymede is 4% that of here and at Titan it's 1% that of here so I don't think you could even do that in the first place. These bodies would also have atmosphere lifetimes at human temperatures of single or double digit kiloyears as well as near as I can calculate, especially around Jupiter with the crazy radiation environment.

comment by The_Jaded_One · 2015-09-14T22:38:33.904Z · score: 0 (0 votes) · LW(p) · GW(p)

Isn't this a bit of a "straw musk"? I haven't seen it claimed by Musk or anyone competent/high up at Spacex or their fan communities that Mars could be terraformed in a "ridiculously short" time, i.e. < 30 or so years.

Perhaps we should be more precise about what counts as "ridiculously short", quantify the disagreement, etc.

comment by Douglas_Knight · 2015-09-08T19:11:59.805Z · score: 1 (1 votes) · LW(p) · GW(p)

What's going on in your first paragraph? How did we get from spaceflight to cars?

Without bothering to read these comments, my understanding is that fuel cells are bad for cars but good for spaceships. Batteries win on energy per volume, but lose on energy per mass. Also, fuel cells can store energy for a longer period of time, but that is relevant to the outer system, not for Mars.

comment by gwern · 2015-09-08T20:09:57.844Z · score: 1 (1 votes) · LW(p) · GW(p)

What's going on in your first paragraph? How did we get from spaceflight to cars?

The linked articles cover pretty much everything, from cars to spaceflight.

comment by passive_fist · 2015-09-09T22:11:27.092Z · score: 0 (0 votes) · LW(p) · GW(p)

Batteries win on energy per volume, but lose on energy per mass.

No, the issue is power density. Fuel cells win over batteries in terms of energy per mass but lose in terms of power per mass and power per volume. Fuel cells are still an order of magnitude or so behind batteries in terms of deliverable power. This is why they are best suited to applications that require power drain for an extended period of time without the possibility of recharging.

It's difficult to directly compare batteries and fuel cells, though, because in the fuel cell the actual fuel tank is separate from the electrodes and can be made as large as desired. In the limit of a very large fuel tank, huge energy densities of 20 MJ/kg or 15 MJ/L are possible with methanol. Compare this with about 1 MJ/kg for the best lithium-ion batteries. However, in the same limit, fuel cell power density drops to near zero.

comment by V_V · 2015-09-08T12:51:01.361Z · score: -2 (2 votes) · LW(p) · GW(p)

very seriously given Tesla's demonstrated success

I don't know much about electric cars, but AFAIK the general consensus was that battery-powered EVs are largely infeasible unless there is some breakthrough in battery technology. Did Tesla achieve that or did they just use bigger and more expensive Li-ion batteries?

If I understand correctly, there isn't enough easily recoverable lithium in the world to replace but a small fraction of existing vehicles with Li-ion battery-powered EVs. If that's correct then, barring some breakthrough, Teslas will be forever expensive (and government subsidized) toys for rich people to signal wealth and environmental consciousness.

comment by gwern · 2015-09-08T15:33:16.092Z · score: 2 (2 votes) · LW(p) · GW(p)

Did Tesla achieve that or did they just use bigger and more expensive Li-ion batteries?

I do know that battery technology steadily, if unflashily, improves over time; from my evernotes, see for example the Performance Curves Database for some charts or https://www.quora.com/Is-it-true-that-battery-energy-density-improves-5-8-per-year or http://rameznaam.com/2015/04/30/tesla-powerwall-battery-economics-almost-there/

If I understand correctly, there isn't enough easily recoverable lithium in the world

I don't know about this specifically, but that sounds surprising: isn't lithium one of the most common elements in the universe?

comment by Vaniver · 2015-09-08T16:22:30.671Z · score: 5 (5 votes) · LW(p) · GW(p)

I don't know about this specifically, but that sounds surprising: isn't lithium one of the most common elements in the universe?

This was a minor point in Watchmen, which is where I first heard of it, so this has been the popular perception for why EVs didn't happen for at least 30 years. It appears to be a somewhat serious concern, but as our experience with oil shows, provable known reserves track price to a degree that pessimistic calculations rarely take into account. (Lithium ion batteries also appear to be easily but expensively recyclable, meaning that once the price gets high enough, the total amount of active lithium is the issue, not the demand for new lithium each year.)

comment by V_V · 2015-09-08T19:20:18.385Z · score: -2 (2 votes) · LW(p) · GW(p)

I don't know about this specifically, but that sounds surprising: isn't lithium one of the most common elements in the universe?

Hydrogen is even more common than lithium, but good luck mining it.

comment by Lumifer · 2015-09-08T19:39:12.525Z · score: 3 (3 votes) · LW(p) · GW(p)

Hydrogen is even more common than lithium, but good luck mining it.

It's just a matter of price. At a sufficiently high price for hydrogen there would be no problems in supplying very large quantities of it.

comment by gwern · 2015-09-08T20:08:12.244Z · score: 2 (2 votes) · LW(p) · GW(p)

Not even all that high - water is pretty common...

comment by Lumifer · 2015-09-08T20:14:57.913Z · score: 1 (1 votes) · LW(p) · GW(p)

Basically, the price of energy to split water into oxygen and hydrogen is a hard ceiling for the price of hydrogen.

comment by V_V · 2015-09-09T08:11:53.242Z · score: -4 (4 votes) · LW(p) · GW(p)

Sure, but if you want hydrogen in order to burn it wit oxygen and make heat and water in large scale then getting hydrogen from water is obviously not an option because of thermodynamics 101.

If you need hydrogen for something else, or if you need it to burn it with oxygen in some special application (e.g. rocket propulsion), then it may an option.

comment by Lumifer · 2015-09-09T16:28:13.401Z · score: 3 (3 votes) · LW(p) · GW(p)

is obviously not an option because of thermodynamics 101

It is a perfectly good option if you need hydrogen as energy carrier and not as energy source.

comment by tanagrabeast · 2015-09-08T01:34:20.148Z · score: 3 (3 votes) · LW(p) · GW(p)

It's possible that you are not the intended audience for such an article, which is clearly targeted at people like the author: a non-expert who is sometimes interested in technical topics. Simplifications, which were indeed abundant, are not the same thing as errors, which is what it sounds like you were implying with "ignorance".

If the author was all, "the thrust-to-weight on a Merlin is like, awesome" and you were like, "but that vacuum ISP, yo!" then you should probably be following SpaceX from nasaspaceflight.com rather than from an eclectic blog.

comment by V_V · 2015-09-08T08:05:34.931Z · score: -2 (6 votes) · LW(p) · GW(p)

Yes.

I don't get why there is so much Elon Musk fanboying in tech/libertarian circles. All the businesses the guy is involved in are heavily subsidized by the US government, and yet he gets heralded as a champion of libertarianism.

We can certainly admire Musk's talent for finding innovative ways of exploiting the system for personal gain and creating a cult of personality around himself, but a John Galt incarnate he is not.

comment by knb · 2015-09-09T00:03:56.963Z · score: 2 (2 votes) · LW(p) · GW(p)

I don't get why there is so much Elon Musk fanboying in tech/libertarian circles. All the businesses the guy is involved in are heavily subsidized by the US government, and yet he gets heralded as a champion of libertarianism.

I mostly see the fanboy stuff coming from generic technophiles and millennial liberals/environmentalists.

It wouldn't surprise me too much if some libertarians are big fans, there is a lot of overlap between technophiles and libertarians for whatever reason. And I suppose moderate libertarians wouldn't oppose subsidizing corporate R&D if there are plausible positive externalities. Not all libertarians are purists.