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KHAN:
Goodbye, Admiral. Oh, and don't
count on the Beagle. She can't
move. My next act will be to blow
her out of the heavens.

KIRK:
KHAAAN!

(Obscure Star Trek reference craves moderation of the Funny type from hip Gen-Xer with a softspot for nostalgia.)
Michael.

KHAN:
Goodbye, Admiral. Oh, and don't
count on the Beagle. She can't
move. My next act will be to blow
her out of the heavens.

KIRK:
KHAN!

Michael.

I've been programming perl for almost a decade, after learning it for a system administration job at UnixOps at the University of Colorado.

For those who work in Linux, Unix, or MacOS, I have a useful collection of well documented perl scripts for manipulating data and metadata from the command line.

Most useful are newpl, which creates a full-featured template as a starting point for new perl scripts, and ren-regexp which can manipulate filenames on the command line using a chain of regular expressions. Happy birthday perl!

Michael.

I've been programming perl for almost a decade, after learning it for a system administration job at UnixOps at the University of Colorado.

For those who work in Linux, Unix, or MacOS, I have a useful collection of well documented perl scripts for manipulating data and metadata from the command line.

Most useful are newpl, which creates a full-featured template as a starting point for new perl scripts, and ren-regexp which can manipulate filenames on the command line using a chain of regular expressions. Happy birthday perl!

Michael.

I've been programming perl for almost a decade, after learning it for a system administration job at UnixOps at the University of Colorado.

For those who work in Linux, Unix, or MacOS, I have a useful collection of well documented perl scripts for manipulating data and metadata from the command line.

Most useful are newpl, which creates a full-featured template as a starting point for new perl scripts, and ren-regexp which can manipulate filenames on the command line using a chain of regular expressions. Happy birthday perl!

Michael.

I've been programming perl for almost a decade, after learning it for a system administration job at UnixOps at the University of Colorado.

For those who work in Linux, Unix, or MacOS, I have a useful collection of well documented perl scripts for manipulating data and metadata from the command line.

Most useful are newpl, which creates a full-featured template as a starting point for new perl scripts, and ren-regexp which can manipulate filenames on the command line using a chain of regular expressions. Happy birthday perl!

Michael.

I purchased a wire shelving unit on wheels from the Container Store. I keep the rack in my closet. When I need to get to the wiring, the entire unit rolls out. Total cost was about $150 US.

Michael.

I purchased a wire shelving unit on wheels from the Container Store. I keep the rack in my closet. When I need to get to the wiring, the entire unit rolls out. Total cost was about $150 US.

Michael.

Unlike reality, at least they're not thinking of randomly forcing people to play the game.

Michael

Ugh. What a hideous file selector. After installing and taking MacOS X Panther for a spin last night, I'm just amazed how backwards and unprofessional GTK's file selectors are.

If it's not possible to compete with commercial operating systems, why not make a radically different file selector as an option. Imagine a command-line interface where the user 'cd's into the appropriate directory and does a 'put'? Of course, I'm of the mind that Evolution and Open Office should have a "vi" input mode.

Michael.

Sorry. I'm just having fun.

By the way there were no books used. All that stuff is in my head! (For better or worse.)

You have demonstrated a understanding of the topic and you do have a good point that was underscored by the new post you linked to above.

My "Consumers Unite!" post was phrased in a manner consistent with anticapitalist protesters of the mid 1800s, who attempted to address the proletariat en masse with simple messages typically in the form of a call to action.

This issue is classic class conflict. The corporation is attempting to maintain control over its means of production, which is in this case is a music distribution network. The primary source for maintaining control comes from the State in the form of legislation. Thus, while I agree that you have a point when you refer to public relations, this issue will ultimately be decided in the courts regardless of public opinion. Much like copyright laws, it is only a matter of time until the means of production is litigated back into the control of the music industry.

I submit, that policing comments on Slashdot to present a good attitude serves only to create a docile community. Such a community is exactly the most vulnerable to a slow march towards legislation. We need action.

Michael.

I will analyze the grammar of the following post for your reading pleasure.

Ah, but I was not speaking to logic.

Sentence fragment. The sentence begins with a coordinating conjunction.
Improper colloquial preposition. In colloquial speech the use of "to" as the preposition implies, that the object of the preposition is a recipient of the dialog (a person, animal, or recording device). A good substitute would be "of".

The point is that history has proven logic alone cannot win the day.

No errors.

PR will first, then we hit them with logic.

Sentence fragment. The first coordinate clause lacks a required second verb.
Temporal disagreement. The coordinate clause is in the future tense while the subordinate clause is in the present tense, even though the coordinate clause occurs first.

Your whole post was lacking in logic (and a point or evidence, really) and could be construed exaclty (sic) as I described.

Faulty parallelism. The verbal element "was lacking" is incorrectly used as both an intransitive ("in logic") and transitive verb ("a point ...").

I seek not to defend the RIAA but to make sure we portray a movement against them in the proper light to gather support.

Improper coordinate conjunction. In sentences where the first coordinate clause is negated by the second coordinate clause the coordinating conjunction, "rather", should be substituted for "but".

Your tone will do nothing but to turn people off.

Unnecessary subordinate conjunction. The subordinate conjunction, "to", is unnecessary and without the coordinate conjunction, "but", risks negating the intended meaning of the sentence.

But I'm glad you took freshman English and learned some simple logical fallacy terms! Congrats.

Sentence fragment. The sentence begins with the coordinating conjunction, "but".
Improper adjectival form The nounal element "simple logical fallacy terms" contains the adjectival form of "logic" ("logical") which ambiguously modifies "terms". It should be replaced with the genitive construction, "terms of logic". The use of "fallacy" is awkward and should be omitted. The revised nounal element would read "simple terms of logic".

P.S. - This was English. The prior was Logic.

Michael.

An analysis of the logical flaws of the above reply, submitted for your reading pleasure.

From what you just said, it doesn't matter how many people they sue, you have already made up your irrational, vindictive little mind on the issue.

Ad hominem. The reply attacks the author instead the position through the derogatory use of "irrational" and "little".

I (and they) guess you haven't bought a CD in 3 years nor were likely to for the forseeable (sic) future anyway.

Speculation. There is no evidence in the post of past or future purchasing habits.

If you actually understood the issue, you would know that:

Ad hominem. The reply attacks the author instead of supporting the position through the implication that the author lacks understanding.

1. The RIAA does not represent all artists. This is a problem because they pretend to. Find out which of the bands/artists you like is represented indirectly by the RIAA and stop buying those CD's. Continue to buy CD's from independent bands. I do not download music, but I have bought CD's from my favorite bands online. These are often in the $6-$10 range. If the CD has 15 tracks, thats even better than iTunes.

Logical. This is the kernel of your argument and is well put.

2. Your tone and phrasing does not indicate you will stop listening to new music, only that you will stop buying CD's. This casts you in the light of someone who is not about what's right, but is instead about what you can get for free. By doing this you have marginalized yourself, potentially hurting the cause. The RIAA can point to your mentality and explain to people (as I saw them do on TechTV this morning) that because of people like YOU they have to sue. Is that true? Probably not, but by spouting off like this you move yourself to the fringe and drag the rest of us with you ever so slightly.

Speculation. There is no information in the "tone and phrasing" which conclusively conveys the complex idea of halting CDs purchases while continuing to listen to new music. The continuing train of logic builds upon the preceding speculative argument.

Please people, if we want to do something right here, we have to come across as educated adults and not spoiled children. Though I know Mr. Foreman is not in such a position currently, please keep that in mind if you are ever in a position to represent the group. (And bear that in mind when you mod someone like this up.)

Ad hominem. Attacking the author instead of supporting the argument, through the omission and inclusion of the author from the groups of "educated adults" and "spoiled children" respectively.
Special pleading. The act of "coming across as educated adults and not spoiled children" to achieve the goal of "do(ing) something right" is special pleading disguised as a logical statement. It provides no support for the argument.

My proposal? A no-CD && no-p2p week. A show of boycott AND good faith. If you stop buying CD's but keep trading songs online, you help the RIAA PR campaign. If you stop both, they can't point to p2p as your only reason for not buying CD's anymore.

Non sequitur. It does not follow that a simultaneous boycott will eliminate p2p as a source of contention, given that p2p sharing will resume after a boycott.

You too can detect Baloney!

Michael.

Excellent point. For that matter purchasing online music as opposed to CDs from RIAA labels is equally bad.

Here are some of my independent sources:

A Different Drum
Emusic

Where do you go?

Michael.

I find it unacceptable that a minor has been bullied into paying $2000 by the RIAA.

Leaving the analyses to others, I would like to say concisely that in retribution for this behavior, I from this day forward will never again purchase another compact disc. Ever.

If you would like to demonstrate your disapproval of their harassment and extortion, reply to this message and show your solidarity.

Michael.

"Color psychologists believe that certain hues generate specific, and often very strong responses in people. For example, black can foster strength and encourage independence, while red empowers and can stimulate the mind."

Although many qualities were mentioned, the single most import quality of any voting machine was omitted. That quality is equal access. All members of a democracy must have equal access to and equal ability to use the voting machine.

As an example, currently in California there is controversy over the decision to reduce the number of voting booths in Los Angeles County from the normal 4922 voting booths to 1800 booths for the recall election. Because of the increase in the commute time required to reach a voting booth, portions of the population may find it difficult to vote.

At the risk of drifting off topic, equal access should apply to the basic education required of all citizens as well. To have a true democracy, a society must provide in basic education the tools for any citizen to become a politician. Thus the argument that Gray Davis is uniquely qualified for the role of Governor would be moot. All citizens should be provided with an education that would allow them to hold a political office.

Michael.

"A little ironic that this article on a world wide power grid was published in the September issue of Wired."

It's not ironic rather it's a timely and coincidental. Thanks for the lesson on irony Slashdot!

Michael.

You're treating the symptom not the disease. What you need is to replace your accounting software (and maybe even your OS) with something that meets your business's requirements.

Worried about the cost of new software are you? How much money is your company hemorraging because your using a single-user accounting program that deletes all of your data? How much more will it lose when you try to patch it up with an IM program?

Michael.

Hmm. Interesting. There's more than one way to skin a cat. I think I'll track down dvipdfm right now and give it a try. Thanks for your persistence.

Michael.

• Store vector-based graphics in PDF form.
  If you happen to have PostScript files, use epstopdf to convert them. It is easy to modify my Makefile to make PostScript files a dependency on the target and convert them to PDF on the fly, when you build the document.
• Store raster-based graphics in PNG form.
  Avoid alpha layers in PNG files, as they can cause problems (black lines on the right border of the image).

If you downloaded either file before 15 July 2003 15:00 MST (15 July 2003 21:00 UTC), download the files again. Aparently listings.sty is no longer part of the standard distribution and has been commented out.

Michael.

Below is a link to the article referenced in the parent post.

The Economics of Empire

Michael.

For the technical writer, who plans on publishing conference papers or building large professional documents, such as a dissertation, there is no substitute for LaTeX. It is not a word processor or mark-up language but rather a true professional typesetting package. There really is no alternative (that you can afford).

Given that you're a CS major, you might be interested in looking at my LaTeX source code for a conference paper and my dissertation. Because LaTeX is so much like a programming language, I created a package containing subdirectories with the class file, images, and source code and perform the build using a Makefile. If you can code and you're familiar with Unix, it is a must have. To build the document, simply type make preview in the base directory. A word of caution -- don't even bother downloading this if you run Windows. It runs like a peach in all Unices and MacOS provided pdfLaTeX is installed.

Michael.

For the technical writer, who plans on publishing conference papers or building large professional documents, such as a dissertation, there is no substitute for LaTeX. It is not a word processor or mark-up language but rather a true professional typesetting package. There really is no alternative (that you can afford).

Given that you're a CS major, you might be interested in looking at my LaTeX source code for a conference paper and my dissertation. Because LaTeX is so much like a programming language, I created a package containing subdirectories with the class file, images, and source code and perform the build using a Makefile. If you can code and you're familiar with Unix, it is a must have. To build the document, simply type make preview in the base directory. A word of caution -- don't even bother downloading this if you run Windows. It runs like a peach in all Unices and MacOS provided pdfLaTeX is installed.

Michael.

• It is wrong to capitalize on group-exclusive hatred.
• The game serves as a vehicle for propaganda.

Ethnocentrism is a word coined by William Graham Sumner in an attempt to capture the generalized attitude that one's own group is comparatively superior. It is a generalized concept that encompasses such blights as racism, sexism, nationalism, and religious intolerance.

In our culture it is not acceptable to create a sexist game where men hunt down women nor is it acceptable to create a racist game where whites hunt down blacks. Yet we can create a video game where Americans can kill the foreigner du jour. Although currently it is unfortunately culturally acceptable among some of the population to participate in this nationalism, it is in no way different from the less acceptable forms of ethnocentrism such as racism and antisemitism.

Before you come out in support of such a game, realize that, this is group-exclusive hatred and just like McCarthyism, it is only a matter of time before it falls out of favor with the general populace. Then what will people think of your posts?

Michael.

I gave it a try. BitPass was painless to setup. I clicked on the $3 button, entered my email address as a username, a password, credit card info, and was reading the comic within 60 seconds.

How was the story? Excellent! It is an enjoyable story with moments of tension and humor tied together by an underlying theme of mathematics. Great adult geek fare. I highly recommend it, although I'm still trying to decide if it was long enough for 25 cents. (Afterall I pay nothing for my operating system!)

Michael.

I thought I'd be seeing this after my first post. Someone references measured data in the field of social sciences and another person calls them a name. (Imagine if physicists had to endure name calling whenever they used conservation of momentum!)

What I find interesting is that the person doing the name calling is in the group, whose real income is shrinking (I'm assuming that few people in the top quintile read /.) and stands no long-term personal benefit to supporting a system with such an extreme and growing (i.e. getting worse for you) disparity in wealth. If left unchecked, wealth will accumulate without bound in the top quintile.

So, before we degenerate to name calling again, follow the link, verify the data, and ask, if you are comfortable knowing that as your real wage (income adjusted for inflation) declines, a select few will soon be able to afford their own space agency. Personally, I think it's antithetical to the class-invariant prosperity that capitalism purports.

That's just my 1.72 cents (2 cents down 14% since 1973).

Michael.

This story is disturbing on so many levels.

The first is spending wealth and resources on an endeavour with no contribution to mankind other than giving us the satisfaction that yet another person has been in space. Wealth does not correlate strongly with the skills necessary to perform meaningful science in space.

Even more disturbing is, that the separation between the rich and poor in our society is so great that individuals are on the threshold of being able to afford space flight, while at the same time the real hourly wage of the average American worker fell 14% since 1973. The richest Americans are now able to do for leisure, what once only an entire nation could afford!

(Here's hoping that my moderator is not a billionaire who dreams of space flight). ;P

Michael.

Not to be a troll but I thought this would be an excellent opportunity to mention Mason for those of you who use PHP but are more proficient in Perl. All my previous web development has been performed in PHP, however, recently I've started to use Mason/Perl.

Mason/Perl provides similar functionality as PHP using in-line constructs such as "<%perl> $perl = goes($here); </%perl>", "% $perl = goes($here);", "<% $variable %>", and "<& function.html &>". Its modularity has allowed me to create a dynamic website coded completely in Perl! It provides all the power of Perl, combined with the convenience of in-line PHP, and adds a new level of object-oriented modularity.

Not that I didn't enjoy PHP, it's just that I always felt like I was coding with one hand tied behind my back. If you like Perl, check out Mason.

Michael.

Not to be a troll but I thought this would be an excellent opportunity to mention Mason for those of you who use PHP but are more proficient in Perl. All my previous web development has been performed in PHP, however, recently I've started to use Mason/Perl.

Mason/Perl provides similar functionality as PHP using in-line constructs such as "<%perl> $perl = goes($here); </%perl>", "% $perl = goes($here);", "<% $variable %>", and "<& function.html &>". Its modularity has allowed me to create a dynamic website coded completely in Perl! It provides all the power of Perl, combined with the convenience of in-line PHP, and adds a new level of object-oriented modularity.

Not that I didn't enjoy PHP, it's just that I always felt like I was coding with one hand tied behind my back. If you like Perl, check out Mason.

Michael.

Most of it is because I don't use units or use inheritence on my background colors! I'll fix it up.

I'm curious to see if this will fix the rotten rendering I've been getting from Internet Explorer. All other browsers render it perfectly.

Michael.

Most of it is because I don't use units or use inheritence on my background colors! I'll fix it up.

I'm curious to see if this will fix the rotten rendering I've been getting from Internet Explorer. All other browsers render it perfectly.

Michael.

The diskless Linux PVR boots over the network and NFS mounts its root file system from a Linux server. The PVR then records to an NFS-mounted partition on the server.

I export the server's PVR partition to other clients in my home so I can watch the recorded/recording video where ever I want.

Michael.

The CSS support in Safari is excellent!

I have advanced CSS-generated menus and simulated CSS transparencies on my home page. This complex CSS didn't render in the first Safari releases but quickly improved as new releases came out. Currently it renders my home page as well as Mozilla does. As a matter of fact all the development of my website has moved from my Linux box to my Powerbook. (I used to use Linux, vi, and Mozilla. Now I use MacOS, vi, and Safari.)

:wq
Michael.

I'm a Linux user. No I'm really a Linux user. I currently have four machines. I'm running it at as my primary desktop at work and as a server, primary (gaming) workstation, and diskless PVR at home. I've modded my series-one TiVo. I installed slackware in the days when one had to wrangle 13 floppies.

With that in mind, I recently I purchased a maxed out 17" Powerbook on my research funds at work and have been amazed at the quality of MacOS hardware and software. I get the true Unix experience with terminals, perl, X11, ssh, vim, and the rest along with an exceptional GUI. The best part about MacOS is that it just works. I've got a Sun Blade 2000 on my desk that's a pain. I've been trying to install KDE on it for the better part of a month and I paid $3k for a graphics card that's slower than my nVidia GeForce 3. I upgraded SuSE on my home Linux workstation and once again I have to recompile the kernel to stop my mystery lockups. (One of these days I should write down my sound-card settings.) MacOS provides the best user experience of any Unix OS.

Will I get rid of Linux? No. There's a quality-cost trade off that will always guarantee the presence of both. The ratio is a function of the environment and thus the evolutionary stable strategy that the competing systems reach. When will Linux pass MacOS? Both soon and never. Linux, due to its low-cost software and hardware, will outnumber MacOS soon but Linux will never pass MacOS in quality. Ever.

Linux : MacOS :: VW : Mercedes
Michael.

I'm a Linux user. No I'm really a Linux user. I currently have four machines. I'm running it at as my primary desktop at work and as a server, primary (gaming) workstation, and diskless PVR at home. I've modded my series-one TiVo. I installed slackware in the days when one had to wrangle 13 floppies.

With that in mind, I recently I purchased a maxed out 17" Powerbook on my research funds at work and have been amazed at the quality of MacOS hardware and software. I get the true Unix experience with terminals, perl, X11, ssh, vim, and the rest along with an exceptional GUI. The best part about MacOS is that it just works. I've got a Sun Blade 2000 on my desk that's a pain. I've been trying to install KDE on it for the better part of a month and I paid $3k for a graphics card that's slower than my nVidia GeForce 3. I upgraded SuSE on my home Linux workstation and once again I have to recompile the kernel to stop my mystery lockups. (One of these days I should write down my sound-card settings.) MacOS provides the best user experience of any Unix OS.

Will I get rid of Linux? No. There's a quality-cost trade off that will always guarantee the presence of both. The ratio is a function of the environment and thus the evolutionary stable strategy that the competing systems reach. When will Linux pass MacOS? Both soon and never. Linux, due to its low-cost software and hardware, will outnumber MacOS soon but Linux will never pass MacOS in quality. Ever.

Linux : MacOS :: VW : Mercedes
Michael.

I'm a Linux user. No I'm really a Linux user. I currently have four machines. I'm running it at as my primary desktop at work and as a server, primary (gaming) workstation, and diskless PVR at home. I've modded my series-one TiVo. I installed slackware in the days when one had to wrangle 13 floppies.

With that in mind, I recently I purchased a maxed out 17" Powerbook on my research funds at work and have been amazed at the quality of MacOS hardware and software. I get the true Unix experience with terminals, perl, X11, ssh, vim, and the rest along with an exceptional GUI. The best part about MacOS is that it just works. I've got a Sun Blade 2000 on my desk that's a pain. I've been trying to install KDE on it for the better part of a month and I paid $3k for a graphics card that's slower than my nVidia GeForce 3. I upgraded SuSE on my home Linux workstation and once again I have to recompile the kernel to stop my mystery lockups. (One of these days I should write down my sound-card settings.) MacOS provides the best user experience of any Unix OS.

Will I get rid of Linux? No. There's a quality-cost trade off that will always guarantee the presence of both. The ratio is a function of the environment and thus the evolutionary stable strategy that the competing systems reach. When will Linux pass MacOS? Both soon and never. Linux, due to its low-cost software and hardware, will outnumber MacOS soon but Linux will never pass MacOS in quality. Ever.

Linux : MacOS :: VW : Mercedes
Michael.

Have you noticed how all proposed legislation that affects personal communications has a "chilling effect"? Sounds like a meme to me.

Given that this proposal would require rebuttals along with their requisite external link, by the principles of social network theory wouldn't that enhance communication, thus making "warming effect" a more suitable compound adjective? Perhaps the submitter of the article was referring to the fact that, although it aids overall communication, the proposed requirement would be a violation of his personal and intellectual property forcing him to personally give those, with whom he is diametrically opposed, an avenue of communication.

With that said, here is a link to a person who is in complete disagreement with this post.

Michael.

Have you noticed how all proposed legislation that affects personal communications has a "chilling effect"? Sounds like a meme to me.

Given that this proposal would require rebuttals along with their requisite external link, by the principles of social network theory wouldn't that enhance communication, thus making "warming effect" a more suitable compound adjective? Perhaps the submitter of the article was referring to the fact that, although it aids overall communication, the proposed requirement would be a violation of his personal and intellectual property forcing him to personally give those, with whom he is diametrically opposed, an avenue of communication.

With that said, here is a link to a person who is in complete disagreement with this post.

Michael.

Student loan debt is 85 percent higher among recent college graduates who took on debt while attending public four-year colleges than among graduates from a decade ago. Recent graduates owed an average of $15,100 in 1999/2000, up from $8,200 in 1989/1990. Student loan debt increased by 55 percent among recent graduates of private four-year colleges with student loan debt. These graduates owed an average of $16,500 in 1999/2000, compared to $10,600 in 1989/1990 (all figures in 2002 dollars).

Lower income students tend to owe the most money, but the biggest increase in indebtedness over the decade has been among higher income students. In 1999/2000 recent graduates of public colleges from families in the poorest two quartiles owed an average of $13,300 and $13,400, respectively. This compares with an average debt burden for indebted students from the richest quartile of $12,000. However, this debt burden represented an increase of 85 percent for the students from the richest quartile, compared to increases of 67 and 62 percent for poorest and second poorest quartiles, respectively.

It was reported that in a conversation between George Bush and James Watson, the topic of modifying genes to improve intelligence came up. President Bush wanted to know if the genes would come in a boot cut.

Michael.
Let's do a 25% split between funny, troll, offtopic, and informative, shall we?

Sir, it's bad form for a scientist to tell people that they don't know what they're talking about. If I am incorrect, exercise the option of teaching rather than insulting.

Anyway, since I don't want you holding (or refusing to hold your breath), I did a little research. For those, who are still interested, below is a wonderful set of links to websites that discuss the rocket equation. The second is my favorite. Enjoy!

Teachin' Science
Rocket Equation Applet
Wolfram

Michael.

Good points.

However, the original post is a first-order approximation of the required energy. It is meant to highlight that one system's required fuel weight is exponential while the other's is not. Let's not let excessive details (which apply similarly to both vehicles) obfuscate the elegant simplicity of the rocket equation.

Your statement that a reduction in fuel by a factor of ten is not possible is very wrong. For a given orbit, provided exhaust velocities are equal, a rocket which does not carry its fuel will always use less fuel. How much less? Well, given that one has an exponential dependence on fuel and the other does not, it stands to reason that for high orbits a factor of ten could be conservative.

A better way for you to argue against a power savings is to point out that there's no way super heated air could ever achieve the exhaust velocity equal to that of kerosine and liquid oxygen. Thus the linear function may for a range of orbits be more expensive than an exponential function.

I knew this was a large subject, when I started it, but wanted present the concept of the exponential rocket equation. I'm working on a full write up on my site and should have something up by the next slashback.

Michael.

A propulsion system such as this can provide a tremendous reduction in required energy.

Conventional rockets, which carry their own fuel are large consumers of energy, as not only must they lift a payload into space but all the fuel as well. The total weight of a rocket including fuel is given by an exponential function known as the rocket equation. Stated simply, a rocket of mass m0 requires fuel of mass m1 to lift it; that fuel of mass m1 requires more fuel of mass m2 to lift it; the fuel of mass m2 requires fuel of mass m3; and so on, ad infinitum. The rocket equation is given by

m = m0 exp(Vf/Vex)

where m is the total required mass, m0 is the mass of the payload, Vf is the final velocity, and Vex is the exhaust velocity of the combusting fuel.

This exponential increase in initial mass can be huge. For example a low earth orbit requires a change in velocity, Vf, of about 8 km/s. Kerosine and liquid oxygen provide an exhaust velocity of about 2.5 km/s. Thus, m/m0 = exp(Vf/Vex) = 24.5. It would take 25 times the original weight of a given payload mostly in fuel to achieve a low earth orbit with kerosine and liquid oxygen! Assuming a payload of 1000 kg and an energy density of 10^7 J/kg for the fuel, the total energy would be E = (25*10^3 kg)(10^7 J/kg) =~ 250 GJ!

The wonderful thing about rockets that don't carry fuel with them is that there is no exponential dependency on initial mass. The energy required is simply the orbital energy, given by half the gravitational potential energy (derivation mercifully omitted) of the payload, given by E = -(G m0 M)/2r. The energy in this case, omitting concerns of efficiency, would be

E = (6.67*10^-11 Nm^2/kg^2)(5.98*10^24 kg)(1000 kg)/(2*6400 km) =~ 30 GJ

The savings in energy is almost a factor of ten!

Michael.

P.S. - Lots of derivations late at night. Be merciful in the event of errors.

This article, like most articles that tout LEDs as a replacement for light bulbs, confuses efficacy and efficiency.

Luminous efficacy is defined as the power of radiated visible light (visible luminous flux) divided by the dissipated electrical power. Given in lumens per watt, efficacy provides a useful means of comparing which source provides the most useful illumination for a given power.

Efficiency on the other hand is defined as the power of radiated visible light (visible luminous flux) divided by the power of all radiated light (total luminous flux). Ideally given as a unit-less ratio, efficiency provides the ratio of useful light to wasted light and does not necessarily correlate with efficacy. It is possible to have simultaneously high efficiency and low efficacy.

The question of why LEDs haven't already replaced all lights can be answered quickly by comparing the efficacy of different sources of light. All numbers below are approximate.

Filament light: 10 lm/W
White LED: 20 lm/W
Halogen light: 25 lm/W
Red LED: 40 lm/W
Florescent light: 100 lm/W
Sodium light: 150 lm/W
It can be seen why red LEDs have replaced halogen bulbs with red filters in stop lights -- red LEDs have a much higher efficacy. Note that the efficacy of LEDs are still well below that of florescent lights. If you feel frustration in seeing how far LED technology still has to go to compete with the boring lighting technologies of yesteryear, assuage your sorrows in the knowledge that you can save billions in energy costs right now, simply by switching to florescent lighting.

Michael.

there once was a power mac
on the net i thought i'd hack
i was stunned to see
it ran bsd
my plans were thus set back


Michael.

sh: /usr/bin/fortune: not found

Jeden Tag verlieren wir immer mehr unserer Rechte, die Profite der großen Firmen zu schützen.

Michael.

Often omitted in the discussion of alternative or modified energy sources is the concept of energy return on investment (EROI). It's defined as the ratio of energy provided for useful work divided by the energy required to extract and process the fuel source.

If one expends energy overprocessesing the fuel, the net energy contributed to the system is reduced. For example, it's been published that ethanol requires 70% more energy to produce than it provides.

Given that the global economic system exists almost exclusively on the ever-diminishing stored potential energy of the earth, it seems that reducing the EROI of an energy source should be avoided.

Michael.