Comments on: Links 12/14: Come Ye To Bethlinkhem

By: Trivial Gravitas

Trivial Gravitas — Mon, 22 Dec 2014 15:22:46 +0000

Really your argument is that SSTO NTR wouldn’t work?

Of course SSTO NTR is bunk, its the worst possible application of NTR. Even chemical SSTO is a bad idea.

NTR is there for *after* you break free of the Goddard problem.

Report comment

By: AlphaCeph

AlphaCeph — Sat, 20 Dec 2014 20:13:57 +0000

I think there are better ways to get *very* large amounts of payload/year from earth to LEO.

For example, if you were willing to invest in a huge mass driver, you could have a fleet of easily reusable vehicles.

Or you could have a tether-based system such as a bolo.

Report comment

By: vV_Vv

vV_Vv — Sat, 20 Dec 2014 11:37:03 +0000

My criticism is even more radical
I argue that manned space missions are a dead end technology, at least for the foreseeable future: there is nothing valuable that humans can currently do in space better than machines can do.

Report comment

By: Andrew Hunter

Andrew Hunter — Sat, 20 Dec 2014 00:34:14 +0000

Hey John – really enjoying this discussion as a non-rocket expert.

Question: what do you think of nuclear saltwater rockets? In principle the scheme seems much saner than NERVA but with similar theoretical advantages on SPI and thrust.

But I’m not enough of an expert to tell if it’s just bullshit.

Report comment

By: Bakkot

Bakkot — Wed, 17 Dec 2014 01:38:30 +0000

(Scott’s not the one who manages the script; I am. It lives over at github and I will be much more likely to see comments and issues there.)

This is unintentional, and there’s not really a good fix – it’s not practical to consistently tell the difference between “reloaded the page” and “submitted a comment” from the client side, which is where the script works.

As for the date issue, I’m not doing any of the parsing manually; to the extent that it’s wrong, it’s because your browser isn’t parsing input the same way it’s formatting output. I might at some point write some custom parsing, but in the mean time you might try another browser.

Report comment

By: BenSix

BenSix — Tue, 16 Dec 2014 22:01:25 +0000

Villagers in Kazakhstan Are Falling Asleep En Masse for No Apparent Reason

Report comment

By: Nornagest

Nornagest — Mon, 15 Dec 2014 19:14:43 +0000

at 1000 dollars a pound, space is never going to be more than a side show. we’ll have some some scientific missions and communications satellites, but no real human presence.

That’s within spitting distance of what passage to the earliest American colonies cost in contemporary money. I think you might be underestimating the kinds of resources people are willing to throw at relocation if there’s a good reason for it.

Of course, there’s nothing in space right now or in the foreseeable future that’d make a $200,000 ticket worthwhile for your average schlub without scientific or technical skills, but that might change.

Report comment

By: Art

Art — Mon, 15 Dec 2014 18:45:47 +0000

My understanding is that conventional and well accepted economic theory predicts that minimum wage does increase unemployment.
It could be that the theory is wrong, or that it is incomplete, or that in aggregate the positives outweigh the negatives, etc.
But by omitting this piece of information you leave readers with the false impression that there is about equal amount of evidence in either direction.

What we do have is lots of studies where some of them support the conventional theory, and some that do not.

Report comment

By: Tom Womack

Tom Womack — Mon, 15 Dec 2014 12:15:06 +0000

Yes, this is Smitherwood-Woodcock ‘Space Transportation Infrastructure Supported By Propellant Depots’. The viewgraph on page four certainly seems to be showing three Delta IV Heavy launches as the per-mission cost to take the propellant for the LEO-to-GEO tug up to a pre-existing propellant depot; there is no viewgraph for the initial launch (or in-orbit assembly) of the depot and the tug.

The crucial question is how much cheaper a device for delivering twenty tons of hydrazine or RP1 or LOX or liquid xenon to a pre-existing propellant depot in LEO can be than a device for delivering twenty tons of fuelled-up general-purpose spacecraft to LEO, and I don’t see Smitherman/Woodcock addressing that.

The relevance of the robots is that a robot for repairing a GEO satellite doesn’t need to be attached to twenty tons of life-support and re-entry equipment, and (assuming there’s enough thickness of polythene and tantalum around the CPUs and the flash memory) doesn’t mind if it takes a month to spiral up to GEO. So it can be small enough to go up on Falcon 9, it can probably be small enough that the propellant for refuelling it per-mission can go up on Falcon 9, it doesn’t mind living on-orbit, and you just give it enough extra xenon each time to take itself from GEO back to being docked at the propellant depot.

Report comment

By: Tom Womack

Tom Womack — Mon, 15 Dec 2014 11:59:43 +0000

There is an actual bug here, which I only didn’t notice because I was posting on December 12th!

It appears that the dates are read in locale format and then parsed in US format, so if it is 14 December it will give me a list of everything posted since the 12th day of month 14, IE nothing, unless I manually change to 12/14/2014.

Report comment