Sunday, May 17, 2015
Thank You
Before the next proper post, I'd like to take a few lines to thank those who took a look at the previous posting on Eagleworks. I've been keeping this blog on-and-off for about a year now with I think scarcely anyone looking at it but me. I don't mind that, since it's a labor of love and not a quest for fame, but it's nice to log on to my email and see a fellow left a comment saying "good article" and then see that over thirty people viewed the page in one day! Anyone's a sucker for a little praise and I'm flattered so many more than the usual amount of folks stopped to consider my opinion. Thanks to you guys and now on to more rocket science!
Thursday, May 7, 2015
A New low for 'Eagleworks' and Space Journalism
Well folks, it's back like a bad dream. Another summer, another blizzard of media hype for a crackpot propulsion concept out of the self-named 'Eagleworks' lab at NASA's Johnson Space Center. Around this time last year I posted a rant about how they were using the conference structure to effectively 'publish' a paper without peer-review, the paper in question being hosted on an AIAA server and being typeset as an AIAA paper, all while the AIAA claimed to have 'not published' the seriously flawed work. The central outlandish claim was that they had found an object (I do not glorify it with the title 'thruster') which produced thrust without using any propellant--a 'reactionless' drive. The true fact that any such device would contradict the basic laws of physics was also widely reported, but instead of using this knowledge to come to the correct conclusion that the measurements were flawed, the media instead decided to pan the conservation of momentum, an unorthodox but evidently acceptable target for tabloid hatred.
Of course even a cursory review of the conference paper revealed gaping flaws. Among many others was that measurements of micronewton thrusts were performed at atmospheric pressures! For those who are not engineers, a micronewton is a very small amount of force. If you softly blow on a piece of paper, you are still generating about 10-100 MILLInewtons of force (1 millinewton = 1000 micronewtons), and so the idea of performing such sensitive measurements under atmospheric pressure is laughable. This is likely the reason Eagleworks, in true crackpot fashion, obfuscated this fact by changing their abstract to falsely say the tests were performed in vacuum conditions when they weren't.
Although little more than a quick laugh in the real space community, Eagleworks' nonsense infected social media for a couple of weeks. When I came to Purdue University last fall, I even found undergraduates (in Engineering) who told me their greatest ambition was to work for Eagleworks and Harold White--a dismal thing to hear from what is supposedly a top Aerospace engineering school. And now it's back in what has become the third episode in this saga of ridiculous claims and media hype.
The newest episode is the most pathetic yet. Faced with the challenge of coming up with yet another piece of garbage to float around the ocean of public discourse and evidently failing to come up with anything original, Eagleworks has instead decided to sew together, in what resembles a Frankenstein's Monster of propulsion claims, their two previous pieces of nonsense regarding 'warp drive' and their 'reactionless' drive--that's right folks, a reactionless warp drive! Instead of even dignifying those of us who work on legitimate propulsion research with something resembling what a real researcher might do, e.g. submit a paper to a conference or give a talk, they've decided to spit in the face of the entire community by posting an announcement on an online forum.
From the media hype however, you'd think this amateur, non NASA affiliated forum might as well have been a major aerospace journal! Left and right there were claims that "NASA has gotten one step closer to warp drive" or that they had now somehow validated their "reactionless" drive. Perhaps the most widely cited is this post on the unaffiliated nasaspaceflight.com. The conceited and almost offensively wrong article is simply too bad to not address, and actually I found that the main arguments against Eagleworks' nonsense can be summarized nicely by rebutting the ridiculous claims made in this post. The rest of this article will just be quotes from their article with anything anyone with a real background in physics would say following the quote
-------------------------------------------------------------------------------------
Thrust measurements of the EM Drive defy classical physics’ expectations that such a closed (microwave) cavity should be unusable for space propulsion because of the law of conservation of momentum.
So they must be wrong. Classical physics in the classical regime is not debatable. Momentum conservation in any measurable regime is not debatable. If you find your measurements disagree with momentum conservation, they are wrong. Period.
Last summer, NASA Eagleworks – an advanced propulsion research group led by Dr. Harold “Sonny” White at the Johnson Space Center (JSC) – made waves throughout the scientific and technical communities when the group presented their test results on July 28-30, 2014, at the 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference in Cleveland, Ohio.
And it was the worst piece of nominally serious work in propulsion I've ever seen. It was a laughing stock within the major university laboratory where I was an engineer and even the AIAA did not want to take responsibility for it, denying it was ever published by them.
Those results related to experimental testing of an EM Drive – a concept that originated around 2001 when a small UK company, Satellite Propulsion Research Ltd (SPR), under Roger J. Shawyer, started a Research and Development (R&D) program.
And it was a crackpot idea which the British Government foolishly spent money trying to develop to no avail. Shawyer is not an engineer and his unpublished 'paper' on this concept is ridiculous.
This lack of expulsion of propellant from the drive was met with initial skepticism within the scientific community because this lack of propellant expulsion would leave nothing to balance the change in the spacecraft’s momentum if it were able to accelerate.
This is strictly speaking wrong. EM waves carry momentum, and so they could in principle be used for propulsion, but the amount of momentum they carry is so tiny compared with the power required to produce them that it is an extremely inefficient way to do business. This is called a Photon Rocket and has been used for years as a way to understand the limitations of propulsion systems.
However, in 2010, Prof. Juan Yang in China began publishing about her research into EM Drive technology, culminating in her 2012 paper reporting higher input power (2.5kW) and tested thrust (720mN) levels of an EM Drive.
Dr. White proposed that the EM Drive’s thrust was due to the Quantum Vacuum (the quantum state with the lowest possible energy) behaving like propellant ions behave in a MagnetoHydroDynamics drive (a method electrifying propellant and then directing it with magnetic fields to push a spacecraft in the opposite direction) for spacecraft propulsion.
And as usual Dr. White is speaking nonsensical technobabble. There are no ions in the qft vacuum, and the charged particles which are produced disappear so fast that they could never even feel an applied electric field much less be accelerated through one. The qft vacuum is also, like everything else in the universe, relativistic, which is to say you can't really push against it. For White's claim to be true, all of physics starting with Newton would have to be wrong. There is so much evidence to the contrary, it is appealing to suggest that it is instead Eagleworks' shoddy laboratory skills which has produced this erroneous result.
This model was also met with criticism in the scientific community because the Quantum Vacuum cannot be ionized and is understood to be “frame-less” – meaning you cannot “push” against it, as required for momentum.
oh wow, they actual get something right. So now you should conclude that since relativity is known to be correct, this explanation is garbage.
The tests reported by Dr. White’s team in July 2014 were not conducted in a vacuum, and none of the tests reported by Prof. Yang in China or Mr. Shawyer in the UK were conducted in a vacuum either.
you wouldn't know this from their abstract, but yes, this is likely to be one source of error. On a side note, not knowing you have to test microthrust devices in vacuum is the sort of abysmal ignorance that would be expected of a freshman in the lower half of his or her physics 101 class, not the leader of a NASA "research" group.
The scientific community met these NASA tests with skepticism and a number of physicists proposed that the measured thrust force in the US, UK, and China tests was more likely due to (external to the EM Drive cavity) natural thermal convection currents arising from microwave heating (internal to the EM Drive cavity).
To just name one source of possible error (probably the most egregious). This DOES NOT mean this is the ONLY source of error. Proper microthrust measurements take months if not years for new devices. If you get the result that your device violates known physics, you should check your apparatus because there is a mistake. If the device is not in vacuum you are not measuring microthrust, you are measuring small perturbations on the device due to the environment.
However, Paul March, an engineer at NASA Eagleworks, recently reported in NASASpaceFlight.com’s forum (on a thread now over 500,000 views) that NASA has successfully tested their EM Drive in a hard vacuum – the first time any organization has reported such a successful test.
Could you imagine if this was true? "Hey guys, I just found out all of physics starting from Newton must be wrong! Should we try and retake our measurements and, if we find they're good, submit our revolutionary findings to a peer-reviewed journal?" "Nah, let's just post something on an online forum, it's basically the same thing."
To this end, NASA Eagleworks has now nullified the prevailing hypothesis that thrust measurements were due to thermal convection.
No they haven't. A couple of idiots have just posted some piece of crackpot garbage on a forum. If this were a real lab we'd like to see some kind of data first. Knowing that Eagleworks disingenuously makes things up or obfuscates their flawed procedures to support their absurd claims however, I would not trust anything they produce.
A community of enthusiasts, engineers, and scientists on several continents joined forces on the NASASpaceflight.com EM Drive forumto thoroughly examine the experiments and discuss theories of operation of the EM Drive.
I didn't wade through the >100 page sewer that was that forum post, but I'm guessing everything was as hilarious and wrong as White's bizarre claims. I also like how we're now giving "enthusiasts"--i.e. amateurs--the same amount of say in this as engineers and scientists. Though if these were Eagleworks' "engineers" and "scientists" the amateurs might actually be better than them.
This synergy between NASASpaceflight.com contributors and NASA has resulted in several contributions to the body of knowledge about the EM Drive.
Yep, advanced propulsion is officially in the toilet. Of course they don't name a single contribution made by the amateur forum posters, although if they had it wouldn't matter since everything involved in this refuse is about as legitimate as Douglas Adams' Impossibility Drive--and not half as entertaining.
The NASASpaceflight.com group has given consideration to whether the experimental measurements of thrust force were the result of an artifact. Despite considerable effort within the NASASpaceflight.com forum to dismiss the reported thrust as an artifact, the EM Drive results have yet to be falsified.
Probably because these are amateurs and not professional engineers. If you want to really claim acceptance you should submit to peer-review (whence the wonderful phrase "peer-review or it didn't happen"). From how the article sounds it seems like a lot of the amateurs had the good sense to understand Eagleworks' claims are nonsense though, so that makes me feel a little better. Lastly, it's not the amateurs' (or anyone else's) responsibility to "falsify" the Eagleworks nonsense, it is Eagleworks' job to prove it. If they are doing ridiculous things like testing for microthrust without using a vacuum it is exceedingly likely their results are garbage because they are obviously incompetent.
After consistent reports of thrust measurements from EM Drive experiments in the US, UK, and China – at thrust levels several thousand times in excess of a photon rocket, and now under hard vacuum conditions – the question of where the thrust is coming from deserves serious inquiry.
No it doesn't. It deserves to be mocked and shamed. It's an absurd degree of professional incompetence and ignorance coupled with conceited media showboating which makes me weep for humanity. All of these 'experiments' are riddled with basic flaws and have produced widely divergent results, which are inconsistent not only with all physics but with each other. There was nothing in the claims of Shawyer, Guido Fetta, the Chinese (I don't remember their names and honestly don't care), and Eageworks the first time. There still isn't anything except a new low for NASA's biggest embarrassment and yet another insult to those of us who put in a lot of effort and sacrifice a lot of time to try and produce real propulsion devices.
------------------------------------------------------------------------
The article goes on for a while after this, but honestly I'm so tired and so depressed that I have to stop here, shut down my computer, and walk to the liquor store to buy a bottle of Bourbon. After actually reading this drivel I'm going to have to spend the rest of the night drinking and weeping for my nation's sick and failing national civilian space agency.
To the hope of better times ahead...
Tuesday, February 3, 2015
Mach Number Versus Speed and Velocity
I've just a quick post today clearing up a simple misunderstanding I see all the time in amateur/layperson discussions of AEROnautics (taking a break from spaceflight for just a little bit). This is the difference between the mach number and speed/velocity of an aircraft. Quite frequently people confuse mach number for speed--e.g. talking about how fast or agile an aircraft is by talking about what mach number it can fly at--when the truth is a bit more complicated than this.
While the meaning of an aircraft (or rocket's) speed is clear to most people, its mach number is often treated as an equivalent substitute. Saying you're moving supersonically is a euphemism for going fast. But the mach number of an aircraft--and which side of the sonic boundary it's on-- is equal not to just the the speed of the aircraft but rather the speed of the aircraft divided by the local speed of sound. As an equation this is written
\begin{equation}
M = V/a
\end{equation}
where M is the mach number, V is the speed, and a is the speed of sound. At first glance, especially to those new to aerospace, this may seem pointless; the speed of sound is constant, right? Well, actually no, it isn't. The speed of sound in a fluid varies as a function of three parameters: (1) the temperature of a fluid, (2) something called the specific gas constant of a fluid and (3) something called the specific heat ratio of the fluid. The first parameter has to do with the actual state of the fluid, while the second two only have to do with what kind of fluid is used and therefore are true constants for the atmosphere; at least to a good approximation.
Most people know that as you go further upward into the atmosphere, the pressure decreases. This is because there's less air molecules the further you go from the surface of the earth and thus there's less of a force per unit area pushing on you. What many people forget is that temperature too changes, as can be seen in the image below.
While the meaning of an aircraft (or rocket's) speed is clear to most people, its mach number is often treated as an equivalent substitute. Saying you're moving supersonically is a euphemism for going fast. But the mach number of an aircraft--and which side of the sonic boundary it's on-- is equal not to just the the speed of the aircraft but rather the speed of the aircraft divided by the local speed of sound. As an equation this is written
\begin{equation}
M = V/a
\end{equation}
where M is the mach number, V is the speed, and a is the speed of sound. At first glance, especially to those new to aerospace, this may seem pointless; the speed of sound is constant, right? Well, actually no, it isn't. The speed of sound in a fluid varies as a function of three parameters: (1) the temperature of a fluid, (2) something called the specific gas constant of a fluid and (3) something called the specific heat ratio of the fluid. The first parameter has to do with the actual state of the fluid, while the second two only have to do with what kind of fluid is used and therefore are true constants for the atmosphere; at least to a good approximation.
Most people know that as you go further upward into the atmosphere, the pressure decreases. This is because there's less air molecules the further you go from the surface of the earth and thus there's less of a force per unit area pushing on you. What many people forget is that temperature too changes, as can be seen in the image below.
In everyday, low altitude flying, this change in temperature is not enough to significantly change the speed of sound, and thus in principle the mach number might be okay to use for a rough speed comparison, but there are actually only very few low altitude planes where the mach number matters, mostly because the speed of sound is so much faster than the aircraft at sealevel. At higher altitudes the speed of sound drops off. At still higher altitudes it grows again, drops off again, and finally grows strongly as you exit the planet. Thus the altitude an aircraft is flying at strongly influences the meaning of its mach number with respect to its velocity!
A Boeing 747, for instance, cruises at roughly 20-30,000 ft--safely within relatively sealevel like conditions. Its mach number will be a good approximate indication of how fast it would be going at sealevel, but an SR-71 cruises at 85,000 ft, where the local speed of sound is almost 10% less! This means the mach number of the SR-71 would be greater than its mach number at the same speed at sealevel. There may even be flight regimes where the aircraft is operating supersonically in the altitude it was designed for and subsonically in a lower altitude.
Other than speed, what is the mach number good for? Well, all sorts of things. In compressible fluids, like air, the equations governing aerodynamic and thermodynamic behavior are strongly related to the mach number, and the way they affect the structure and forces on an aircraft change considerably as it breaks the sound barrier. For instance, the heating which takes place behind a supersonic shockwave is significant, and thus an aircraft flying supersonically must have a well designed nosecone if it is to withstand this heating (since the nose is for all intents and purposes behind a supersonic shockwave as the plane is in flight).
So next time someone quotes a mach number at you when talking about how fast an aircraft is going, ask them if it is a high altitude or low altitude aircraft. A large mach number for a high altitude aircraft may not correspond to a hugely greater speed than a low (or even subsonic) mach number for a lower altitude aircraft.
Monday, January 26, 2015
A Mathematical Vocabulary for Modern Engineering
My adviser and I sat down today for one of our typical meetings. After we had talked about some of my new results and discussed a paper (not mine, thankfully) which he referred to simply as "a mess", the discussion shifted. He started asking me about my background and what sort of math and physics courses I had taken while an undergraduate. We have similar backgrounds in a way--both physicists turned engineers, both interested in the more scientific side of engineering, and both less persnickety about obtaining rigorous numerical results in any given calculation than we are about making sure our concept is right. But one huge difference in our backgrounds is where we were educated. I went to an American public university while he was educated in the Soviet Union. I graduated just over a year ago, having the full blessing (and curse) of powerful computing tools at my side, while most of his computations were done with pencil, paper and a lot of careful thought. I knew the main point in his asking me about my education was to try and estimate the skill level of the students in a course he is currently teaching in plasma physics, and his realization that many American engineering students today are woefully uneducated or undereducated in the physics and math they need to understand and solve modern "high-tech" engineering problems.
He asked me how many semesters of general physics were typically included in our curriculum, I said three. He was clearly disappointed and said "there should be five." He then asked me what sort of math most engineers take. I said "three semester of calculus, one of linear algebra, and one of differential equations."
Him: Any probability or statistics?
Me: Not required.
Him: What about PDEs? How many semesters of ODEs?
Me: PDEs are also optional and only one semester of ODEs.
Him: Complex variables?
Me: A few weeks in some math methods class if at all.
He frowned again. "when I was an undergraduate we had two semesters of both PDEs and ODEs, and another for complex variables." My heart sank with his as I too realized how little most American engineers are taught about math. I chose not to inform him of how little regard most of them even have for math--useful math like series expansions, special functions, and complex integration; not just obscure modern mathematics, which can only rarely be used to gain useful results. He told me some students in the class couldn't even understand how to compute the average of a function, that others had no idea what Bayesian probability meant, that still others had no idea what the divergence or curl of a vector field was. This meant he would have to tailor his discussion of concepts involving these basics to a level far below that of a graduate course, something that myself as a student enrolled in the course found disappointing. It is a sad state of affairs.
On my way home I started thinking about how this could be changed. There's certainly no shortage of stuff to do on this count, but I thought that the first step might be establishing a basic mathematical vocabulary for modern engineering. This would be a list of mathematical topics to serve as an educational guide for people who want to be good engineers (as opposed to marginal, unqualified, or simply bad engineers) and would include actually "advanced" topics rather than the basic topics of calculus, power series, rudimentary linear algebra and ODE theory--which are typically taught in upper-division engineering math courses, but in reality should be assumed knowledge from freshman courses and high school. I've decided to list these topics and post them here. If I get enough time I might try to find good resources for learning what you need to know about the topics I've listed, but for now you're on your own. In order to be complete, I'll go ahead and list the basic topics under "Basic Math" but hopefully everyone with an engineering degree has at least seen those. The highly recommended (but not typically taught) subjects are classified as "Mid-Level Math"; these are math topics which can be learnt once the courses in Basic Math are completed and should be the bulk of the higher level math knowledge of the typical good engineer. Finally comes "High-Level Math" which may not be extremely useful for every engineer but is a good idea to learn to get more of a math background and is essential for some of the more advanced parts of engineering.
Basic Math (currently required at most schools):
--High School Math (basic algebra, geometry, trigonometry, and "precalculus", e.g. analytic geometry and some properties of functions.)
--Calculus (3 semesters worth hopefully with an introduction to vectors and multivariate functions).
--Linear Algebra including the concept of a vector space.
--Ordinary Differential Equations.
--Rudimentary probability and statistics (even this is not always required however)
Mid-Level Math (optional or not taught at most schools but needed frequently):
--Calculus-based probability and statistics.
--Partial differential equations, including eigenfunction expansions and special functions
--Linear operator theory
--Detailed theory of function spaces, Fourier theory, integral transforms, and completeness
--Complex variable theory
--Detailed vector calculus theory
--Basic numerical analysis
--Basic optimization techniques
High-Level Math (typically not offered for engineers):
--Tensors and tensor calculus
--Applied group theory (do not learn this from a pure math book. Instead look for a physics book)
--Differential forms and curvilinear spaces
--Stochastic processes and measure theory (again making sure it is not from a pure math book)
--Classical and modern theory of the Calculus of Variations (could really be "Mid-Level")
--Topology and mathematical analysis (needed mostly in control theory)
--Numerical methods for ODEs and PDEs (CFD or other computational fields)
Is this a lot? Well, yes. Unfortunately it doesn't change the fact that modern engineering problems typically deal with math from at least the "Mid-Level" category, if not the "High-Level" category (I recently was surprised to find the group at Purdue which focuses on tracking Space Debris using hard-core measure theory to construct their models of the debris field.) High school, as you see, barely teaches you the most rudimentary aspects of the most basic mathematics which you will use as an engineer. The math courses you are forced to take in college cover less than a third of what you will probably have to use and less than a quarter of what you might have to know to be a top engineer in your field. To circumvent this failure of the typical engineering curriculum you will have to put in quite a bit of elbow grease and more than a few nights of voluntary studying. But if you are patient, dedicated, and reasonably intelligent you will find the benefits to understanding real engineering mathematics are enormous. With a definite and extensive mathematical vocabulary we will make the first step toward building much more widespread mathematical literacy in engineering, but the hard parts are yet to come.
Good night and good luck, folks.
He asked me how many semesters of general physics were typically included in our curriculum, I said three. He was clearly disappointed and said "there should be five." He then asked me what sort of math most engineers take. I said "three semester of calculus, one of linear algebra, and one of differential equations."
Him: Any probability or statistics?
Me: Not required.
Him: What about PDEs? How many semesters of ODEs?
Me: PDEs are also optional and only one semester of ODEs.
Him: Complex variables?
Me: A few weeks in some math methods class if at all.
He frowned again. "when I was an undergraduate we had two semesters of both PDEs and ODEs, and another for complex variables." My heart sank with his as I too realized how little most American engineers are taught about math. I chose not to inform him of how little regard most of them even have for math--useful math like series expansions, special functions, and complex integration; not just obscure modern mathematics, which can only rarely be used to gain useful results. He told me some students in the class couldn't even understand how to compute the average of a function, that others had no idea what Bayesian probability meant, that still others had no idea what the divergence or curl of a vector field was. This meant he would have to tailor his discussion of concepts involving these basics to a level far below that of a graduate course, something that myself as a student enrolled in the course found disappointing. It is a sad state of affairs.
On my way home I started thinking about how this could be changed. There's certainly no shortage of stuff to do on this count, but I thought that the first step might be establishing a basic mathematical vocabulary for modern engineering. This would be a list of mathematical topics to serve as an educational guide for people who want to be good engineers (as opposed to marginal, unqualified, or simply bad engineers) and would include actually "advanced" topics rather than the basic topics of calculus, power series, rudimentary linear algebra and ODE theory--which are typically taught in upper-division engineering math courses, but in reality should be assumed knowledge from freshman courses and high school. I've decided to list these topics and post them here. If I get enough time I might try to find good resources for learning what you need to know about the topics I've listed, but for now you're on your own. In order to be complete, I'll go ahead and list the basic topics under "Basic Math" but hopefully everyone with an engineering degree has at least seen those. The highly recommended (but not typically taught) subjects are classified as "Mid-Level Math"; these are math topics which can be learnt once the courses in Basic Math are completed and should be the bulk of the higher level math knowledge of the typical good engineer. Finally comes "High-Level Math" which may not be extremely useful for every engineer but is a good idea to learn to get more of a math background and is essential for some of the more advanced parts of engineering.
Basic Math (currently required at most schools):
--High School Math (basic algebra, geometry, trigonometry, and "precalculus", e.g. analytic geometry and some properties of functions.)
--Calculus (3 semesters worth hopefully with an introduction to vectors and multivariate functions).
--Linear Algebra including the concept of a vector space.
--Ordinary Differential Equations.
--Rudimentary probability and statistics (even this is not always required however)
Mid-Level Math (optional or not taught at most schools but needed frequently):
--Calculus-based probability and statistics.
--Partial differential equations, including eigenfunction expansions and special functions
--Linear operator theory
--Detailed theory of function spaces, Fourier theory, integral transforms, and completeness
--Complex variable theory
--Detailed vector calculus theory
--Basic numerical analysis
--Basic optimization techniques
High-Level Math (typically not offered for engineers):
--Tensors and tensor calculus
--Applied group theory (do not learn this from a pure math book. Instead look for a physics book)
--Differential forms and curvilinear spaces
--Stochastic processes and measure theory (again making sure it is not from a pure math book)
--Classical and modern theory of the Calculus of Variations (could really be "Mid-Level")
--Topology and mathematical analysis (needed mostly in control theory)
--Numerical methods for ODEs and PDEs (CFD or other computational fields)
Is this a lot? Well, yes. Unfortunately it doesn't change the fact that modern engineering problems typically deal with math from at least the "Mid-Level" category, if not the "High-Level" category (I recently was surprised to find the group at Purdue which focuses on tracking Space Debris using hard-core measure theory to construct their models of the debris field.) High school, as you see, barely teaches you the most rudimentary aspects of the most basic mathematics which you will use as an engineer. The math courses you are forced to take in college cover less than a third of what you will probably have to use and less than a quarter of what you might have to know to be a top engineer in your field. To circumvent this failure of the typical engineering curriculum you will have to put in quite a bit of elbow grease and more than a few nights of voluntary studying. But if you are patient, dedicated, and reasonably intelligent you will find the benefits to understanding real engineering mathematics are enormous. With a definite and extensive mathematical vocabulary we will make the first step toward building much more widespread mathematical literacy in engineering, but the hard parts are yet to come.
Good night and good luck, folks.
Wednesday, January 7, 2015
The Worst News a Teacher Can Ever Hear
No, it's not that one of your courses was cancelled, or that you made a mistake during the lecture which caused everyone to fail the exam, or even that your favorite student has dropped out and decided to study philosophy instead.
The worst news a teacher can ever hear is that one of their students has been killed and sadly I've just heard that news.
The first class I ever taught was a physics class for the Humboldt County chapter of Upward Bound. It was the summer of 2011 and I was getting ready to pack my bags and head down to the Bay Area to finish my undergrad at UC Berkeley. Before I left I wanted to give something back to a community I knew I would never live in again and I chose Upward Bound because it has the noble goal of empowering disenfranchised and minority youth to receive educations and help their communities. As a poor kid myself, who left high school early and began my college career at a community college, I empathized with the kids who were in this program and decided I would offer them the physics class I wish I had in high school. For five weeks we talked about everything from Newtonian mechanics and falling bodies to quantum weirdness and the hunt for elementary particles, and I was seriously impressed with how these kids--poor Whites and Native Americans who never had the benefits of good high school classes--took to the material. I remember the summer of 2011 far more vividly than a lot of my time in Humboldt, and I think I'm safe in saying it was one of the most fulfilling things I've done so far.
All these memories have flooded back to me in a bitter sweet way as I learned one of my favorite students was killed in a car accident back in September. She wasn't always the one with the answer, but she always had a smile, a good attitude, and never once complained or whined about me or the course. After I finished teaching she 'Friended' me on Facebook and I had the opportunity of following her accomplishments. She graduated high school against all odds and even began attending the community college I started at. I desperately hoped to one day see a status that she had accepted a scholarship to attend UC Berkeley and telling her of all the things she could do there. Now the only updates I will ever see are condolences and friends saying "we miss you."
To say I'm tremendously sad, upset, and in grief is an understatement. I never expected to see news this sad so few years after I taught that course and I'm at somewhat of a loss for words. The only thing I can think to say is the Hoopa Nation has lost one of its finest young women and my once pristine memories of the wonderful summer of 2011 are now tinged with a sadness I can never remove.
My thoughts are with her family and her friends.
I'm sorry for the personal post, but the this sad and unexpected news really affected me. More Rocket Science to come soon!
The worst news a teacher can ever hear is that one of their students has been killed and sadly I've just heard that news.
The first class I ever taught was a physics class for the Humboldt County chapter of Upward Bound. It was the summer of 2011 and I was getting ready to pack my bags and head down to the Bay Area to finish my undergrad at UC Berkeley. Before I left I wanted to give something back to a community I knew I would never live in again and I chose Upward Bound because it has the noble goal of empowering disenfranchised and minority youth to receive educations and help their communities. As a poor kid myself, who left high school early and began my college career at a community college, I empathized with the kids who were in this program and decided I would offer them the physics class I wish I had in high school. For five weeks we talked about everything from Newtonian mechanics and falling bodies to quantum weirdness and the hunt for elementary particles, and I was seriously impressed with how these kids--poor Whites and Native Americans who never had the benefits of good high school classes--took to the material. I remember the summer of 2011 far more vividly than a lot of my time in Humboldt, and I think I'm safe in saying it was one of the most fulfilling things I've done so far.
All these memories have flooded back to me in a bitter sweet way as I learned one of my favorite students was killed in a car accident back in September. She wasn't always the one with the answer, but she always had a smile, a good attitude, and never once complained or whined about me or the course. After I finished teaching she 'Friended' me on Facebook and I had the opportunity of following her accomplishments. She graduated high school against all odds and even began attending the community college I started at. I desperately hoped to one day see a status that she had accepted a scholarship to attend UC Berkeley and telling her of all the things she could do there. Now the only updates I will ever see are condolences and friends saying "we miss you."
To say I'm tremendously sad, upset, and in grief is an understatement. I never expected to see news this sad so few years after I taught that course and I'm at somewhat of a loss for words. The only thing I can think to say is the Hoopa Nation has lost one of its finest young women and my once pristine memories of the wonderful summer of 2011 are now tinged with a sadness I can never remove.
My thoughts are with her family and her friends.
I'm sorry for the personal post, but the this sad and unexpected news really affected me. More Rocket Science to come soon!
Tuesday, December 23, 2014
The Breakthrough Propulsion Concept Sanity Checker
Propulsion is, on the surface, a very simple science: I make a machine which uses stored propellants or some medium my vehicle is interacting with to generate a momentum exchange with my surroundings, thus making my vehicle move in the opposite direction. But once you dive into the details of any propulsion system you will quickly find that mastering this 'simple' science requires a lot of detailed knowledge: thermodynamics, fluid dynamics, chemistry, heat transfer physics, statistical mechanics, material science, electronics and of course rigid body mechanics and dynamics are essential. If you work with space propulsion odds are you will also need to know quite a bit about quantum mechanics, electrodynamics, and plasma physics as well. Put synoptically, it's really hard to make a completely new propulsion system which will be a fundamental 'breakthrough' in the field. Many have tried; most have failed. But that of course doesn't stop a wide variety of scam artists as well as honest-to-goodness crackpots from standing up and claiming they have a viable 'breakthrough' propulsion concept. Sadly these people can often find support both among laymen (who have little resources to distinguish viable new concepts from obviously spurious claims) and even propulsion engineers who may be specialized in a different area.
I've been getting tired of these claims being reported in the media and discussed as if they had any merit. Not only does this spread false information among non-experts, but it also takes time and reporting space away from true progress in propulsion. Imagine for instance if the coverage of the garbage NASA reactionless drive coverage I posted about in August had instead been dedicated to the co-development of a full-flow staged combustion rocket engine by NASA and SpaceX. Not only is this more interesting than a reactionless drive because it actually exists, but it's also more useful as a technology and the story gives a better picture of how the aerospace industry actually works. Thus in the hopes of assisting not only prospective inventors of 'breakthrough' propulsion concepts but also laymen and elsewhere specialized engineers, I've compiled a list of guidelines for any would-be propulsion innovator. If there's something that's not on here which should be please let me know in the comments!
The List:
6. No Unobtanium Principle: If your breakthrough propulsion concept requires propellants, power sources, or materials which either do not currently exist or have been shown to not be able to exist, it is fiction until those materials become available.
I've been getting tired of these claims being reported in the media and discussed as if they had any merit. Not only does this spread false information among non-experts, but it also takes time and reporting space away from true progress in propulsion. Imagine for instance if the coverage of the garbage NASA reactionless drive coverage I posted about in August had instead been dedicated to the co-development of a full-flow staged combustion rocket engine by NASA and SpaceX. Not only is this more interesting than a reactionless drive because it actually exists, but it's also more useful as a technology and the story gives a better picture of how the aerospace industry actually works. Thus in the hopes of assisting not only prospective inventors of 'breakthrough' propulsion concepts but also laymen and elsewhere specialized engineers, I've compiled a list of guidelines for any would-be propulsion innovator. If there's something that's not on here which should be please let me know in the comments!
The List:
1. If your breakthrough propulsion concept relies on unobserved or falsified physics, it is exceedingly likely to be spurious.
2. if your breakthrough propulsion concept achieves delta-V without expending reaction mass, it is exceedingly like to be spurious.
3. Indeed, if your breakthrough propulsion concept violates the conservation of momentum or angular momentum in a closed system in any way, it is exceedingly likely to be spurious.
4. No propulsion system can ever, ever, EVER lead to a macroscopic violation of energy conservation. EVER.
5. building on that last point, if your breakthrough propulsion concept violates ANY of the laws of thermodynamics, it is purely fictitious.
6. No Unobtanium Principle: If your breakthrough propulsion concept requires propellants, power sources, or materials which either do not currently exist or have been shown to not be able to exist, it is fiction until those materials become available.
7. Math is your friend. If you cannot present and justify simple, first-order performance calculations for your breakthrough propulsion concept, the odds are it is flawed or impossible.
8. Fallacious and unjustified reasoning is not an "approximation", it's just wrong.
9. Almost any concept relying on the "quantum vacuum" is exceedingly likely to be spurious, most likely due to the proposer not understanding the physics of the QFT vacuum.
10. Conference papers which have not been peer-reviewed are not evidence of concept validity. Neither are websites, blog posts, articles in low-impact/poor quality/obscure/for-profit journals, non peer-reviewed articles on online repositories or publications, self-published books, angry letters or emails to legitimate propulsion researchers, snarky comments on websites/blogs/online publications, or abstract macaroni portraits of your idea.
11. Your tests of your prototype of your breakthrough propulsion concept are not evidence of validity until (1) they are written up, peer-reviewed, and accepted for publication in a well-known, mainstream aerospace or propulsion journal, (2) they are successfully duplicated by other mainstream propulsion researchers, and (3) these successful duplications are themselves written up, peer-reviewed, and published in a well-known, mainstream aerospace or propulsion journal.
12. Test results reported without a rigorous propagation of uncertainty, comprehensive analysis of systematics, and a significant number of data points, are meaningless and can (and should) be dismissed without review.
13. Similarly, test results obtained at a low level of statistical significance do not validate nor falsify a concept.
14. Preparing a press release or giving a talk on your idea before submitting it for peer-review is tantamount to being so arrogant you think you don't need any feedback from your colleagues. Since the most arrogant people in any subject are usually the least capable (see the Dunning-Kruger effect) this is a valid cause for skepticism in and of itself.
15. Patents are not the same as peer-review, nor are they evidence of validity. Just because you have the legal right to patent your idea doesn't mean anyone else has to take it seriously. In truth any idea which is patented before it is constructed, tested, and peer-reviewed is likely to be spurious.
14. Preparing a press release or giving a talk on your idea before submitting it for peer-review is tantamount to being so arrogant you think you don't need any feedback from your colleagues. Since the most arrogant people in any subject are usually the least capable (see the Dunning-Kruger effect) this is a valid cause for skepticism in and of itself.
15. Patents are not the same as peer-review, nor are they evidence of validity. Just because you have the legal right to patent your idea doesn't mean anyone else has to take it seriously. In truth any idea which is patented before it is constructed, tested, and peer-reviewed is likely to be spurious.
Sunday, December 21, 2014
Walter Lewin Barred From MIT After Serious Allegations of Harassment
For those who don't know already, MIT professor emeritus Walter Lewin has been barred from MIT and his ties with the University cut after a secretive investigation of Lewin claimed he had violated MIT's sexual harassment guidelines during an online course. In the wake of the decision, all of Lewin's video lectures on physics have also been pulled from MIT's open courseware site and several press statements released. There is more detail here and another blog about it here.
If these allegations are true it is truly a shame. I remember watching Lewin's now famous basic physics lectures while I learned the same stuff from my much loved but sometimes overworked physics professor, Erik Kramer of the College of the Redwoods (known simply as "CR" to any Humboldt county native). Prof. Kramer's class, unlike so many physics courses, was something students looked forward to and he put a lot of his soul into making it as good as possible. This was sometimes hard to do at a small community college where he was the only physics professor and which had no money for any new lab equipment, often making lab sessions and demonstrations minimal. Those of us who were interested in physics, including myself and my friend Noah Flemens (now a grad student in applied physics at Cornell), would supplement Kramer's lectures with Lewin's from MIT and pretty soon the small group of 'physics kids' at CR were comparing and contrasting their "two favorite Dutchmen", though of course only Kramer could truly be thanked (or blamed) for how any of us turned out.
To hear the decision on Lewin is heartbreaking and I don't think it's right that MIT is being so secretive regarding the evidence which pushed them to dismiss a legend in physics education. Sources I found say it was clear the incidents were real and serious and this may be true, but it is no more than hearsay until we are given something--anything--to back it up beyond MIT's word.
Another bizarre decision is MIT's removal of Lewin's physics lectures from their Open Courseware website. In my opinion this is one of the best ideas MIT has had in a long time and one of the only things keeping them relevant in a world where their prestige is based more and more on their brand rather than their research quality (aside: I could write multiple posts about my view on 'big' school brands but now's not the time). Lewin's lectures were undoubtably some of the best on Open Courseware and recent events don't change that. Instead it robs the world at large from hearing good, well put together lectures on basic physics, and is MIT breaking a promise they (very publicly) made to the world at Open Courseware's inception.
Thus it seems as if MIT has two responsibilities in dealing with this incident: (1) make public the evidence of Lewin's harassment; for those of us who once idolized him as a teacher, it's the least they could do. (2) restore Lewin's lectures to Open Courseware. These lectures in and of themselves have nothing to do with this incident and it is pointless to punish those who would like to learn more about basic physics for inappropriate things the presenter may or may not have subsequently done.
If these allegations are true it is truly a shame. I remember watching Lewin's now famous basic physics lectures while I learned the same stuff from my much loved but sometimes overworked physics professor, Erik Kramer of the College of the Redwoods (known simply as "CR" to any Humboldt county native). Prof. Kramer's class, unlike so many physics courses, was something students looked forward to and he put a lot of his soul into making it as good as possible. This was sometimes hard to do at a small community college where he was the only physics professor and which had no money for any new lab equipment, often making lab sessions and demonstrations minimal. Those of us who were interested in physics, including myself and my friend Noah Flemens (now a grad student in applied physics at Cornell), would supplement Kramer's lectures with Lewin's from MIT and pretty soon the small group of 'physics kids' at CR were comparing and contrasting their "two favorite Dutchmen", though of course only Kramer could truly be thanked (or blamed) for how any of us turned out.
To hear the decision on Lewin is heartbreaking and I don't think it's right that MIT is being so secretive regarding the evidence which pushed them to dismiss a legend in physics education. Sources I found say it was clear the incidents were real and serious and this may be true, but it is no more than hearsay until we are given something--anything--to back it up beyond MIT's word.
Another bizarre decision is MIT's removal of Lewin's physics lectures from their Open Courseware website. In my opinion this is one of the best ideas MIT has had in a long time and one of the only things keeping them relevant in a world where their prestige is based more and more on their brand rather than their research quality (aside: I could write multiple posts about my view on 'big' school brands but now's not the time). Lewin's lectures were undoubtably some of the best on Open Courseware and recent events don't change that. Instead it robs the world at large from hearing good, well put together lectures on basic physics, and is MIT breaking a promise they (very publicly) made to the world at Open Courseware's inception.
Thus it seems as if MIT has two responsibilities in dealing with this incident: (1) make public the evidence of Lewin's harassment; for those of us who once idolized him as a teacher, it's the least they could do. (2) restore Lewin's lectures to Open Courseware. These lectures in and of themselves have nothing to do with this incident and it is pointless to punish those who would like to learn more about basic physics for inappropriate things the presenter may or may not have subsequently done.
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