The problems with mass migration to space

The Guardian has an opinion piece up expressing scepticism about the likes of Jeff Bezos's dreams of O'Neill style massive space colonies and colonisation of Mars.   It's not at all detailed, though, on the technical issues:  it more looks at the changing motivation for space colonisation, and notes that it is pretty much now advocated out of environmental concern.

I don't think the change in motivation makes much sense, though.

As I recall (and I am not going to bother searching for confirmation just at the moment), the issues that killed off O'Neill style colonies from popular consideration were:

a. more careful engineering consideration which indicated that the structural stresses on spinning such massive objects to get any decent form of artificial gravity were much higher than initially realised, and pretty much impractical using the initially assumed materials;

b. the number of rocket launches required to put so much equipment in orbit (even assuming using a slingshot on the moon to get raw materials into a processing facility) was going to put an awful lot of pollutants into the upper atmosphere, with possibly deleterioius atmospheric effects;

c. the new technology involved for orbital processing of lunar soil is completely untested and getting that alone to work is surely going to be a big enough task in itself.

As far as point b is concerned,  I seem to recall O'Neill addressed that himself when he was alive, and argued it wasn't that many launches.   But the Falcon Heavy rocket from Space X does use kerosene and liquid oxygen, and it will be putting a significant amount of CO2 into the atmosphere.  Not sure how much compared to other things, but it is ironic that in order to escape a greehouse Earth, some now propose adding to the problem on the way out.

I don't know if point a has been reconsidered - but I suspect that it is still a very real problem.  It might be able to be addressed by using strong materials you can make on Earth, but O'Neill colonies were supposed to be made from pretty basic materials and I find it hard to envisage making more than pretty basic metals in orbit from Moon dirt.  It's yet another technological hurtle that would be ridiculously hard to overcome without launching, in pieces, manufacturing equipment made on Earth.

I see that Bezos went to Princeton when O'Neill was there - hence he caught the O'Neill dream early on.

But really, I would have to hear how he thinks the problems I listed above are supposed to be addressed before I consider it as having any real credibility.

The thing is, the problem with greenhouse gases was barely a thing when O'Neill was writing his book in the mid-1970's.  More general concerns about industrial pollution were one of the motivations for talking about moving off planet.   But now that the AGW problem has been fully realised, dreams of a "let's just move into space" solution (apart from the possibility of microwave power from orbiting solar power satelittes) just seem a fanciful and wasteful idea compared to putting a lot of technological effort into clean energy on Earth.  

(Having said that, I still think having a smallish, permanent base on the moon to act as a "lifeboat" for Earth is a good idea.   And it is so much simpler to get stuff there and back than from Mars.  Once you learn how to run a viable colony there, then you might think about going to Mars.)