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Comment: Re:Expectations (Score 1) 76

by brambus (#47962695) Attached to: Trouble In Branson-Land, As Would-Be Space Tourists Get Antsy Over Delays

Your weight estimates could be correct but there is no way you're gonna fit a 140-seat glider in the Falcon 9 fairings.

Of course it won't and I explicitly said to replace the entire second stage as well. I would have hoped it to be obvious that I was talking about reengineering large parts of the system.

Anyways 5 minute weightless suborbital flight is so 1961. I would just make a stretched version of Dragon that seats 20 people (no cargo) and send them into orbit for $50k each.

Or to Mars for perhaps $500k, I agree. I was just thinking out loud about the possibilities here, just to show that Virgin Galactic's system is an overpriced toy that could be done much cheaper by the likes of SpaceX.

Comment: Re:Expectations (Score 1) 76

by brambus (#47961229) Attached to: Trouble In Branson-Land, As Would-Be Space Tourists Get Antsy Over Delays

Real zero-g (not Vomit Comet or theme park rides) would be pretty damn cool.

Well, the Vomit Comet is exactly the same as LEO zero-g, it's just much shorter. All the Virgin Galactic guys are doing is extending that time from 30s to 300s. And at tremendous cost, I might add.
As for 140 people for a suborbital flight on Falcon 9, that sounds about right, maybe even a bit pessimistic. By my reckoning, the second stage with propellant and max payload masses somewhere in the vicinity of 100 tons, more than the MTOW of a Boeing 737-800 and at that mass, the first stage is enough to give them around 2 km/s at burnout and an arc of well above 100km. And that includes the spare fuel to fly the spent booster back to the launch pad and land it, so no loss there either. So replace the entire second stage & payload with a hypersonic glider and you're done, basically. It might even be conceivably possible to use this to actually travel somewhere at hypersonic speeds without having to muck about with all that ramjet/scramjet business, though I'm not sure it'd be worth it.
Assuming capital costs per flight of $1M (20% of which is fuel, the rest being O&M, equipment amortization and profit), one such ticket could cost as little as ~$5k. Not chump change by any means, but still 20x lower than what Virgin Galactic are charging. It's about 1st class-type money on some long-haul flights.

Comment: Success for me; depends on definition (Score 1) 182

by virve (#47901709) Attached to: The MOOC Revolution That Wasn't

I've followed three online courses. One I completed and did all the assignments. Two where I watched all the material but did not attempt the assignments (one required I rigged up a video camera to submit; could not be bothered).

Quite frankly, I got what I wanted out of these courses. So how is this a failure?

I have to balance effort with other commitments. I trust I am not the only one. Signing up is cheap. I've signed up for a few more but other real life took precedent. No big deal.

On the other hand, I don't see online courses replacing traditional educational settings but that was pretty naive to being with.

So: nothing to see here. Yawn!

Comment: Re:Electrolysis still required, says TFA (Score 4, Informative) 113

by brambus (#47892043) Attached to: Liquid Sponges Extract Hydrogen From Water
It's still an interesting article. It seems they've found a way of cheaply producing ammonia from hydrogen. Not sure they meant ammonia exactly, but they mention "liquid-based inorganic fuel" and later talk about how ammonia is important for fertilizer, so I'm kinda guessing that's what they're making. Ammonia can then be used to either make fertilizer, liquid fuel substitutes and a bunch of other interesting processes.

Comment: Electrolysis still required, says TFA (Score 4, Informative) 113

by brambus (#47891853) Attached to: Liquid Sponges Extract Hydrogen From Water

The process uses a liquid that allows the hydrogen to be locked up in a liquid-based inorganic fuel. By using a liquid sponge known as a redox mediator that can soak up electrons and acid we’ve been able to create a system where hydrogen can be produced in a separate chamber without any additional energy input after the electrolysis of water takes place.

Comment: It's not horseshit. It's happening. (Score 5, Insightful) 444

I teach physics. The most depressing part of my job is teaching a general-education class where I have to explain global warming.

Scientists don't have a private agenda. We would LOVE to be wrong about this, but:
- Temperatures are going up worldwide
- Global temperatures are historically very well correlated to CO2 concentrations
- CO2 concentrations have a straightforward and well-understood effect on infrared light produced by
earth's blackbody radiation
- Even small changes to global temperature will create big changes to local climates
- We can stop this, but only if radical action is taken right now
so
- We're all fucked.

This is not the time for the debate about whether the effect is real. This is the time for debate about just how MUCH we should be panicking. We're in the deep shit here. We're talking about large proportions of humanity not having enough food to eat. The resulting warfare and hardship will be devastating.

Comment: Re:Not just Reno (Score 3, Interesting) 444

by brambus (#47888143) Attached to: If Tesla Can Run Its Gigafactory On 100% Renewables, Why Can't Others?

He focused on energy sources, and his point that the increase in usage of brown coal is neglegtible, is correct.

In that respect, that is correct, the increase might indeed be just noise.

You focus on TWh production of elictricity, where you clearly see there is a noticeable increase in terra watt hours of electricity produced ... however no one can deduce how much more brown coal was used for that.

This data is pretty hard to come by, I agree, so I had to make some assumptions (elaborated below). Can you cite your sources?

so bottom line the "record usage" of brown coal is still nearly 20% below the 1990 level (in primary energy) and roughly 10% below 1990 level in electric power production

While it is true that some efficiency offsets might be made, your numbers simply do not add up to the graph Dunkelfalke linked. It lists lignite at 3201 TJ in 1990 and 1645 TJ in 2012. That is not "[usage] of brown coal is still nearly 20% below the 1990 level (in primary energy)", that is a 50% reduction in primary energy. All of that also happened before the year 2000 - since then, pretty much no reduction in lignite use has occurred. If powerplant efficiency were indeed rising while electrical generation remained mostly flat during the 2000-2011 period, that would imply that a rising proportion of that input lignite energy (which flatlined during that time period too) is being used for heating and other uses. However that doesn't appear to be the case either (coal use outside of electricity is falling rapidly) - this leads me to believe that there hasn't been such a dramatic increase in efficiency as to be able to confidently say that the recent increase in generation is due to an increase in powerplant efficiency. Also, how can you claim use in electrical generation is 10% below 1990, when even you said yourself just a few moments before that "no one can deduce how much more brown coal was used for that". I'd really appreciate if you could cite your sources, that would allow us to clear up the situation. If you have access to figures on lignite consumption by coal fired power plants, that would be great. Otherwise, the only reliable thing we can say is that electrical generation from lignite is at an all time high since 1990.

Comment: Re:Not just Reno (Score 2) 444

by brambus (#47887637) Attached to: If Tesla Can Run Its Gigafactory On 100% Renewables, Why Can't Others?

Stop spreading lies.

Maybe you should start with your own advice. The poster was referring to electrical generation here, not overall energy use. Your graph is for overall energy use (and I'm not sure about the proportions there either, they seem a bit off). You might have been clued into that by the units being petajoules (customarily used for overall energy production) not watthours (customarily used for electrical generation). Another thing that might have ticked you off is that mineral oil is a good 1/3 the energy share there. And natural gas about 1/4. In actual fact, when you look at the right graphs, in electrical generation, oil accounts for a meager 1% and gas about 11%. In relative proportions lignite has remained mostly stable since 1990, however in absolutes, 2013 (161 TWh) was indeed a record year since 1990 (171 TWh). Hard coal has also picked up in the last 5 years.

Comment: Re:above, below, and at the same level. ZFS is eve (Score 1) 366

by brambus (#47887459) Attached to: The State of ZFS On Linux
I think you misunderstood my reply. I was replying to the poster talking about iSCSI having to be implemented in ZFS. That's what I was addressing.
You talk about a different thing altogether - ZFS backing. The zvol-on-another-zpool solution should work, although performance will suck. The zvol-on-the-same-zpool solution can and will hang for obvious reasons.

Comment: Re:Proformance (Score 1) 366

by brambus (#47881983) Attached to: The State of ZFS On Linux
Keep perspective. Are you really going to build a box like that with just one 2 GHz quad-core CPU?
I have pushed 4GB/s through a SAS SSD array on ZFS, but even so I maxed out on other stuff way before the CPU and much less checksumming ever began to be an issue (e.g. had to go through two LSI SAS 9200-8e HBAs, because one maxes out the PCI-e 2.0 x8 lanes; with two HBAs I maxed out on the two 6G SAS links to my JBOD). That the point of my post. I've yet to see a system which is constrained by the checksumming in any meaningful way.

Comment: Re:License mismatch (Score 1) 366

by brambus (#47881559) Attached to: The State of ZFS On Linux
Sun still had closed bits in the OS kernel when OpenSolaris was CDDL'd, so GPL was a non-starter because of GPL's "infectious" nature of spreading to all source that makes up a project. CDDL is more permissive in this - it simply forces you to keep the free bits that you got free, but doesn't expand to anything outside of the source files you got.

Comment: Re:Magic (Score 2) 366

by brambus (#47881415) Attached to: The State of ZFS On Linux

it updated zfs code, updated a disk format encoding but you could not revert it

You can thank your package maintainer for this. ZFS never ever ever upgrades the on-disk format silently. You always have to do a manual "zpool upgrade" to do it. It'll tell you when a pool's format is out of date in "zpool status", but it'll never do the upgrade by itself.

updating a disk image format and not allowing n-1 version of o/s to read it is a huge design mistake and I'm not sure I understand the reasoning behind it, but until that is changed, I won't run zfs

Again, this is not ZFS' fault, it's your package maintainer for auto-upgrading all your imported zpools. ZFS never does this by itself.

Adapt. Enjoy. Survive.

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