I'm sure you're right - it should be possible. But the point is that we don't know how to do it, and we'd have to spend some considerable amount of time and money to figure it out... in addition to all the other time and money requirements to build a starship. Who's paying for all this?
Well, at the moment, the University of Arizona is. At the moment the Biosphere 2 facility is being used to do research into climate change, among other things. The researcher I was talking to was doing research on soil ecologies, IIRC. There are lots of practical Earth-bound applications for this kind of application.
Also, the second Biosphere 2 mission (1994) was a success, in that the crew managed to achieve self-sufficiency in food (and oxygen) production...
As Elon Musk regularly points out in his press appearances: the land was not a "nice place to live" for fish, but eventually proto-amphibians crawled out of the oceans, overcoming the many challenges of adapting to such a hostile environment. The moon and Mars are not "nice places to live" for our species, but we already have the tools we need to tackle and eventually overcome the challenges that they present.
The Concorde was not grounded because of technical difficulties, it was grounded because of economics. No-one wanted to pay for the luxury of supersonic flight.
This is actually a drastic simplification of the rather complex reality. Firstly, the crash on in July 2000 was not due to a Concorde design or maintenance fault, but its robustness to future FOD damage was nevertheless greatly increased by some subsequent modifications. Secondly, the "return to flight" coincided with the massive slump in all air travel following the September 2001 terrorist attacks, which reduced consumer confidence, but most indications suggested that demand for Concorde resumed relatively quickly. However, the slump for all air travel created the perception of lack of demand for Concorde. Thirdly, both Air France and Airbus were, in fact, profiting from Concorde operations, but felt that profits could be increased by retiring the aircraft and concentrating on subsonic services. Finally, Air France was concerned about potential liability in the case of future accidents. Note that Richard Branson's attempt to purchase and continue to operate the Concorde fleet was stymied by Airbus refusing to provide continued maintenance, not by lack of demand.
Demand was present, and it was feasible to provide supersonic air travel at an economically viable price point. I think that the EADS/Japanese collaboration on NEXST/ZEHST is a good example of how the industry is still looking at ways to meet that demand.
The second problem is a ship going that fast will accrue mass as it gains speed. Even if we handwave away the issue of powering it, you still get to the point where you're flying a black hole. As you make your way through the cosmos you'll be causing all sorts of mayhem in the solar systems you pass.
Sounds awesome.:-P
Also sounds like you've read Tau Zero by Poul Anderson.
The space station in Earth orbit has one big problem: radiation. It'll require a lot of shielding to be safe for long-term habitation.
This is one reason why space stations for long-term habitation aren't a great idea, and why building long-term basis on asteroids or low-mass moons (e.g. Phobos) is much more viable, since you can just bury your habitat in a couple of metres of regolith and have all the shielding you need. For short-term habitation, low levels of shielding plus heavily shielded "storm shelters" on spacecraft and stations are a reasonable approach.
1) It seems a stable biosphere is bigger than "biosphere II" which was pretty freaking big for just a couple people.
Recently, I discussed Biosphere II with someone who worked on it. It rapidly became biologically stable -- the problem was that it didn't stabilise at a equilibrium point compatible with human life! There's no fundamental reason why a similar project couldn't work properly, but some tuning is clearly needed.
As far as "inbreeding" is concerned, see this article. It says:
Following Frankham et al., estimates of the population numbers required to overcome these effects (known as the effective population, Ne) are 50 to avoid inbreeding depression, 500-5000 to retain evolutionary potential, and 12 to 1000 to avoid the accumulation of deleterious mutations. Franklin proposed the 50/500 rule used by conservation practitioners, whereby an Ne of 50 is required to prevent an unacceptable rate of inbreeding, while a long-term Ne of 500 is required to ensure overall genetic variability. Given that the average Ne/N ratio is roughly 0.10 these rules of thumb translate to census sizes of 500 to 50,000 individuals.
This will only change when deep-space telescopes find a definite extrasolar planet for human resettlement.
We've found a huge number of candidate planetary star systems, with confirmed planets in the habitable zone, using the Kepler telescope. But now we need JWST to look more closely at them. But JWST was underfunded, so it got delayed and went over budget, which caused it to get delayed some more, in a sort of destructive spiral. And now NASA's caught between a rock and hard place. Congress orders NASA to build SLS and JWST and run the ISS and collaborate with other countries and do technology research and do educational outreach and launch and run geoscience projects and... Congress doesn't provide the funds necessary to do all those things.
It's a "No bucks, no Buck Rogers" situation. And then people have the gall to blame NASA, rather than Congress.
Because, seriously, why the fuck would we want to get to Mars?
Because, seriously, why the fuck would we want to climb Everest?
Mars is the most hospitable planet in the solar system for Earth life, and the best place available to practice and refine the technologies needed for interstellar travel and colonisation.
It's not the administration's fault, it's Congress. NASA HQ and the administration didn't even want to build SLS -- they wanted to bolster the commercial launch market instead -- and were forced to do it by the Congressional committee.
If there's someone Lou Friedman should be complaining about, it's Senators Nelson and Shelby and their fixation on providing pork to large aerospace contractors in return for bribes, I mean campaign donations.
I would have hoped that someone in his position would be better informed, frankly.
Right now, in reality, the private sector is not doing it at all, out side of some sub-orbital test flights. Whine about government all you want to, but they got to the moon in 10 years of trying, and so far a private company hasn't even orbited around the planet one time...
Note that Skylon precursor HOTOL, a project under seemingly much more reputable entities and stricter oversight, apparently came to conclusion that it would be not really operationally better than a "dumb rocket" using comparably advanced technology or materials...which for a specaplane are required to make it even barely possible.
That's exactly backward. Alan Bond headed the HOTOL project. Guess who owns Reaction Engines, the company behind Skylon? That's right, Alan Bond. The main issues with HOTOL were actually more to do with the vehicle geometry, not with the engines themselves, and with politics (specifically, the Thatcher government). Apparently, the new materials and manufacturing technology available 20 years later have made it possible to address the technical issues. Let's not forget that there have been several independent evaluations made of Skylon's feasibility, including by the ESA, and none of them have found any reasons for the spacecraft not to be feasible.
Apparently SpaceX pricing is a-la-carte. The $80-125 million dollar price tag is for the launcher itself. You have to provide transport, vehicle assembly, mission control, range safety, telemetry monitoring, recovery, etc. for yourself. Granted though, NASA has all those capabilities.
[Citation needed].
Seriously, though, I hadn't heard that before and it contradicts what I'd heard previously, so I'd love to know your sources for this information!
How is this different from the canceled Ares? Or they just trim out the LEO variant?
They painted it white.
It may seem flippant, but this comment is pretty close to the money. SLS is indeed the zombie version of Ares V with some relatively minor alterations.
If this is not correct perhaps you should educate NASA and while you're at it let me in on how to properly express 70 metric tons using the abbreviated form.
The SLS will launch between 70 Mg (7e4 kg) and 130 Mg (1.3e5 kg).
This is also a common problem with spacing: it's tempting to think, we have N passengers an hour and run a bus every 10 minutes, but N/2 totally fit in a bus, so we could really improve our finances if we just ran a bus every 30 minutes instead. But when the bus runs every 30 minutes rather than 10 minutes, a lot fewer people take it.
Doesn't matter. If you nominally run the bus every 10 minutes, what really happens is every half-hour, three buses come by at once.
"We like to drive in convoys, we're most gregarious!"
Except with a major difference: Bazaar gives you the ability to have both checkouts share the same database, so it doesn't take up twice the amount of space. Git doesn't let you do this -- you'll have to create two full copies of the repository. (Ironically, this accusation is often made towards Bazaar by people who haven't heard of shared repositories.)
git does allow you to do this, with plenty of flexibility: see man git-clone. Specifically, if cloning a git repository on the same filesystem, the common data is automatically shared using hard links (don't forget that all entries in a git repository are immutable, so this Just Works); additionally, you can use some combination of the --reference, --shared or --no-hardlinks options to control exactly how cloning should occur.
Perhaps it would have been better to say "I don't think git allows you to do this" rather than "git doesn't let you do this".;-)
Re:Git could use revision numbers
on
The Rise of Git
·
· Score: 1
Use `git describe':
[peter@harrington gaf (master)]$ git describe
1.7.1-20110619-169-gc9d4f66
This returns a string containing the most recent tag on the branch (1.7.1-20110619), the number of commits since that tag (169), and the first seven hexadecimal digits of the commit SHA-1 (c9d4f66).
Slashdot Mirror
I was talking about multiprocessing, not multithreading.
"#pragma once" is broken.
Meanwhile, this Java code will work on all platforms, processors, and compilers, forever and ever:
I'll switch to using a language other than C when a language other than C allows me to use wait-free shared-memory multiprocessing algorithms.
Yes, because that's exactly what's going on here.
Oh wait -- no it's not, it's something completely different!
I watch every episode of Top Gear and enjoy the show immensely, but even I think that segment was extremely dodgy, to say the least.
I'm sure you're right - it should be possible. But the point is that we don't know how to do it, and we'd have to spend some considerable amount of time and money to figure it out... in addition to all the other time and money requirements to build a starship. Who's paying for all this?
Well, at the moment, the University of Arizona is. At the moment the Biosphere 2 facility is being used to do research into climate change, among other things. The researcher I was talking to was doing research on soil ecologies, IIRC. There are lots of practical Earth-bound applications for this kind of application.
Also, the second Biosphere 2 mission (1994) was a success, in that the crew managed to achieve self-sufficiency in food (and oxygen) production...
As Elon Musk regularly points out in his press appearances: the land was not a "nice place to live" for fish, but eventually proto-amphibians crawled out of the oceans, overcoming the many challenges of adapting to such a hostile environment. The moon and Mars are not "nice places to live" for our species, but we already have the tools we need to tackle and eventually overcome the challenges that they present.
The lack of citations exhibited by this comment thread leaves me speechless.
The Concorde was not grounded because of technical difficulties, it was grounded because of economics. No-one wanted to pay for the luxury of supersonic flight.
This is actually a drastic simplification of the rather complex reality. Firstly, the crash on in July 2000 was not due to a Concorde design or maintenance fault, but its robustness to future FOD damage was nevertheless greatly increased by some subsequent modifications. Secondly, the "return to flight" coincided with the massive slump in all air travel following the September 2001 terrorist attacks, which reduced consumer confidence, but most indications suggested that demand for Concorde resumed relatively quickly. However, the slump for all air travel created the perception of lack of demand for Concorde. Thirdly, both Air France and Airbus were, in fact, profiting from Concorde operations, but felt that profits could be increased by retiring the aircraft and concentrating on subsonic services. Finally, Air France was concerned about potential liability in the case of future accidents. Note that Richard Branson's attempt to purchase and continue to operate the Concorde fleet was stymied by Airbus refusing to provide continued maintenance, not by lack of demand.
Demand was present, and it was feasible to provide supersonic air travel at an economically viable price point. I think that the EADS/Japanese collaboration on NEXST/ZEHST is a good example of how the industry is still looking at ways to meet that demand.
He obviously worked at CERN. Don't be sarcastic.
The second problem is a ship going that fast will accrue mass as it gains speed. Even if we handwave away the issue of powering it, you still get to the point where you're flying a black hole. As you make your way through the cosmos you'll be causing all sorts of mayhem in the solar systems you pass.
Sounds awesome. :-P
Also sounds like you've read Tau Zero by Poul Anderson.
The space station in Earth orbit has one big problem: radiation. It'll require a lot of shielding to be safe for long-term habitation.
This is one reason why space stations for long-term habitation aren't a great idea, and why building long-term basis on asteroids or low-mass moons (e.g. Phobos) is much more viable, since you can just bury your habitat in a couple of metres of regolith and have all the shielding you need. For short-term habitation, low levels of shielding plus heavily shielded "storm shelters" on spacecraft and stations are a reasonable approach.
1) It seems a stable biosphere is bigger than "biosphere II" which was pretty freaking big for just a couple people.
Recently, I discussed Biosphere II with someone who worked on it. It rapidly became biologically stable -- the problem was that it didn't stabilise at a equilibrium point compatible with human life! There's no fundamental reason why a similar project couldn't work properly, but some tuning is clearly needed.
As far as "inbreeding" is concerned, see this article. It says:
Following Frankham et al., estimates of the population numbers required to overcome these effects (known as the effective population, Ne) are 50 to avoid inbreeding depression, 500-5000 to retain evolutionary potential, and 12 to 1000 to avoid the accumulation of deleterious mutations. Franklin proposed the 50/500 rule used by conservation practitioners, whereby an Ne of 50 is required to prevent an unacceptable rate of inbreeding, while a long-term Ne of 500 is required to ensure overall genetic variability. Given that the average Ne /N ratio is roughly 0.10 these rules of thumb translate to census sizes of 500 to 50,000 individuals.
This will only change when deep-space telescopes find a definite extrasolar planet for human resettlement.
We've found a huge number of candidate planetary star systems, with confirmed planets in the habitable zone, using the Kepler telescope. But now we need JWST to look more closely at them. But JWST was underfunded, so it got delayed and went over budget, which caused it to get delayed some more, in a sort of destructive spiral. And now NASA's caught between a rock and hard place. Congress orders NASA to build SLS and JWST and run the ISS and collaborate with other countries and do technology research and do educational outreach and launch and run geoscience projects and... Congress doesn't provide the funds necessary to do all those things.
It's a "No bucks, no Buck Rogers" situation. And then people have the gall to blame NASA, rather than Congress.
Because, seriously, why the fuck would we want to get to Mars?
Because, seriously, why the fuck would we want to climb Everest?
Mars is the most hospitable planet in the solar system for Earth life, and the best place available to practice and refine the technologies needed for interstellar travel and colonisation.
It's not the administration's fault, it's Congress. NASA HQ and the administration didn't even want to build SLS -- they wanted to bolster the commercial launch market instead -- and were forced to do it by the Congressional committee.
If there's someone Lou Friedman should be complaining about, it's Senators Nelson and Shelby and their fixation on providing pork to large aerospace contractors in return for bribes, I mean campaign donations.
I would have hoped that someone in his position would be better informed, frankly.
There are just so many fallacies in the parent post that I'm actually at a loss for what to say.
Right now, in reality, the private sector is not doing it at all, out side of some sub-orbital test flights. Whine about government all you want to, but they got to the moon in 10 years of trying, and so far a private company hasn't even orbited around the planet one time...
No, there's no company that's completely privately developed three new rocket engines and launched two new classes of launch vehicles into orbit with a third, even larger, on the way...
You're clearly right, private sector is not doing it at all. Oh wait, no, you're an ignorant clod.
Note that Skylon precursor HOTOL, a project under seemingly much more reputable entities and stricter oversight, apparently came to conclusion that it would be not really operationally better than a "dumb rocket" using comparably advanced technology or materials ...which for a specaplane are required to make it even barely possible.
That's exactly backward. Alan Bond headed the HOTOL project. Guess who owns Reaction Engines, the company behind Skylon? That's right, Alan Bond. The main issues with HOTOL were actually more to do with the vehicle geometry, not with the engines themselves, and with politics (specifically, the Thatcher government). Apparently, the new materials and manufacturing technology available 20 years later have made it possible to address the technical issues. Let's not forget that there have been several independent evaluations made of Skylon's feasibility, including by the ESA, and none of them have found any reasons for the spacecraft not to be feasible.
Apparently SpaceX pricing is a-la-carte. The $80-125 million dollar price tag is for the launcher itself. You have to provide transport, vehicle assembly, mission control, range safety, telemetry monitoring, recovery, etc. for yourself. Granted though, NASA has all those capabilities.
[Citation needed].
Seriously, though, I hadn't heard that before and it contradicts what I'd heard previously, so I'd love to know your sources for this information!
How is this different from the canceled Ares? Or they just trim out the LEO variant?
They painted it white.
It may seem flippant, but this comment is pretty close to the money. SLS is indeed the zombie version of Ares V with some relatively minor alterations.
If this is not correct perhaps you should educate NASA and while you're at it let me in on how to properly express 70 metric tons using the abbreviated form.
The SLS will launch between 70 Mg (7e4 kg) and 130 Mg (1.3e5 kg).
Looking at my list of SI symbols, I believe that NASA are claiming SLS will launch 70-130 milli-Teslas...
Doesn't matter. If you nominally run the bus every 10 minutes, what really happens is every half-hour, three buses come by at once.
"We like to drive in convoys, we're most gregarious!"
conclusion:
it's pretty but it's not exactly the same as GNOME 2.x so I don't like it, and I can't be bothered to type trivial questions into Google.
FTFY.
Except with a major difference: Bazaar gives you the ability to have both checkouts share the same database, so it doesn't take up twice the amount of space. Git doesn't let you do this -- you'll have to create two full copies of the repository. (Ironically, this accusation is often made towards Bazaar by people who haven't heard of shared repositories.)
git does allow you to do this, with plenty of flexibility: see man git-clone. Specifically, if cloning a git repository on the same filesystem, the common data is automatically shared using hard links (don't forget that all entries in a git repository are immutable, so this Just Works); additionally, you can use some combination of the --reference, --shared or --no-hardlinks options to control exactly how cloning should occur.
Perhaps it would have been better to say "I don't think git allows you to do this" rather than "git doesn't let you do this". ;-)
Use `git describe':
[peter@harrington gaf (master)]$ git describe
1.7.1-20110619-169-gc9d4f66
This returns a string containing the most recent tag on the branch (1.7.1-20110619), the number of commits since that tag (169), and the first seven hexadecimal digits of the commit SHA-1 (c9d4f66).