Saturday, February 16, 2019

Lost Wax Casting, ancient technology, still in service

The process goes like this.  Make a wax version of the desired part or artwork.  Then cover the wax master  with clay.  The clay was fired (like pottery) to make it hard and tough.  In the firing the wax melted and ran out.  Then molten metal was poured into the clay mold and allowed to cool and harden.  When cool, the clay mold was broken off and you had a shiny new part or art object.  And no mold parting marks.  Aviation Week claims the lost wax process is 5000 years old.
   Today we call the process "investment casting"  and a lot of key aerospace parts are still made that way.  In fact Aviation Week was complaining about a lack of investment casting capacity  slowing production in the aerospace industry.   One key part made by investment casting is the turbine blades for jet engines.  The tougher you can make the turbine blades, the hotter you can run them which gives better fuel mileage, which translates into better range and better carrying capacity.  Modern turbine blades are very tricky, they have cooling passages up the center, they are cast from secret alloys involving a lot of nickel, and who knows what else, and they are cooled slowly and carefully so that they come out as single crystals of metal.  Some one commented "There are nine countries in the world that can make nuclear bombs, but only two, the US and the UK, that can make modern jet engine turbine blades."

Wednesday, February 13, 2019

USAF manages the KC-46 tanker contract

The KC-46 tanker job should have been a straight forward contract.  Take a well proven airliner which has been in production and flying for decades, take out the seats and install fuel tanks, plus an air-to-air refueling boom in the tail.  No high risk new technology.   Piece of cake, right?
   Well, first the Air Force decided that it knew more about how to wire an aircraft than Boeing did.  Air Force insisted that Boeing re do all the aircraft wiring "to bring it up to Air Force standards".  Good cost enhancer that was. 
   And then, the Air Force wanted a fancy remote vision system, rather than a plain old reliable glass window, to let the refueling boom operator see his boom and steer it into the receptacle of the receiving aircraft.  Now Air Force is complaining that the remote vision system  lacks contrast and looses detail when the receiving aircraft is backlighted by the sun.  (Beware the Hun in the Sun).   For the last two years USAF has refused to accept new KC-46 tankers 'cause of  the remote vision system and 40 brand new KC-46 tankers have piled up at Boeing's  Everett field.  Now, the Air Force has agreed to accept the aircraft, but they will withhold $28 mil per aircraft until the remote vision system is fixed. 
   How to screw up a simple procurement.   Way to go USAF. 
   Note: I am a USAF veteran. 

Monday, February 11, 2019

Green New Deal, or New Green Deal

Speaking as an electrical engineer, let me address one part of the Green New Deal, electric power generation.  We need to keep the power on for customers, all night, and all day.  "Alternate energy" (windmills and solar cells) won't do that.  For example, I live up in the north country where it gets very cold (20 below) and stays cold for days.  My oil burner won't run without electricity.  Should the power go off, my heat goes off, and my pipes will freeze after a couple of hours.  Lots of industrial processes, from traditional ones like baking bread to high tech ones like fabbing semiconductors need the power to stay on while the batch, be it loaves or LSI semiconductors is in the oven.  If the power quits while a batch is in process, that batch is ruined.  Loss of a batch of loaves is a loss of hundreds of dollars, loss of a batch of semiconductors is tens of thousands of dollars.  Plenty of other batch processes will be ruined if the power fails while the batch is in process.
   Solar cells stop making electricity when the sun goes down.  Which happens every evening.  Windmills stop making electricity when the wind stops blowing, which happens less predictably, but often enough. My house is high in the White Mountains of New Hampshire, and I get plenty of dead calm days.  In fact it's a dead calm as I write this.  A power system based on solar and wind will suffer frequent power outages, like every night.  Which is unacceptable, except for those who advocate a return to the Hiawatha life style, teepees heated by wood fires. 
   The greenies have poisoned the waters concerning nuclear power.  We have built dams on all the rivers.  Just the middle sized Connecticut river has six power dams on it starting with Moore Dam in Littleton.  If we want the power to stay on all night, we need to burn natural gas.  Fortunately we have plenty of natural gas.  It's becoming a waste product of fracking.  Out on the Bakken they are paying people to take the gas away.  Natural gas is out competing coal in the power generation business.  
   So, Alexandra Occasional-Castro's call for elimination of fossil fuel ain't gonna happen, not unless we put up with power failures on a daily basis. 

Monday, February 4, 2019

Better double check your yearbook, while you are in the school

A 30 year old yearbook is causing Virginia governor Northam all sorts of grief today.  Lesson to all graduates,  better double check your year book page while you are still at the school.  Remove anything that might cause you grief in the future, should you be successful in your career.  I would recommend strongly against gag photos, photos in any kind of costume, nick names, any kind of sexting, any kind of political remarks.  Keep it down to a professional portrait of yourself, honors, sports played, club memberships, good simple stuff that will look good 20-30 years in the future. 

Sunday, February 3, 2019

MAGA hats show support for our president and the administration

Which is a good thing.  Americans ought to support their president.   As a symbol, the Make American Great Again slogan was created by the Donald Trump campaign in 2016 as part of his effort to win the election.  The acronym and the hat were created a few weeks later.   The MAGA hat means support of the sitting president, nothing more.
   There has been plenty of opining on the tube about the MAGA hat representing racism, white supremacy, un-Americanism, Satan worship, and other malarky.  That's all a crock.  We elected Donald Trum p to be our president in 2016.   To see high school students wearing MAGA hats is a goodness.  The current administration, under attack from the media and the democrats, needs all the support it can get. 

Monday, January 28, 2019

900 year New England temp record meets Shannon's sampling theorem

A post in claims to have used a new method to find and plot the temperature recorded in the bottom of a deep Maine lake.  They perform some unspecified analysis of a chemical that I have never heard of to determine the temperature of long ago.  They don't explain this bit of chemistry at all.  They claim to have taken 136 measurements over some 900 years of lake bottom sediments.  And they claim to have discovered previously unknown temperature variations of 50-60 year duration.
Good paper,  the authors feel they have made a breakthru.
I think they have not taken enough samples.  Temperature in Maine can get up to 90F in the summer, I've been there, I know, and Maine winter runs 20F with cold snaps down as far as -40F.  And  this temperature variation, 70 to 130 degrees, happens quite regularly, summer and winter happen every year.  So we only take 136 samples over 900 summers and winters.  Suppose our samples hit mostly summer for a few years?  Bingo, a heat wave wave, global warming strikes early.  Suppose our samples only hit winter for a few more years in a row?  Bingo, a mini ice age.  
   To do this right, you have to take at least two samples for every year.  That's Shannon's Sampling Theorem, you have to sample twice in the period of the highest frequency  in the signal you are sampling.  If you don't take enough samples, you get aliasing.  That is what causes the wheels of the stagecoach to start turning backwards as the stage gathers speed on the way out of Deadwood.  The movie camera samples the wheels 24 frames per second.  When the wheel spokes move too much in between camera frames, the wheel appears to move in reverse. 
   This paper claims to find 10  different 50-60 year periods of heat or cold.  Since they are not taking enough samples, they could well be seeing an alias.  Their samples  just happen to hit summer for a long stretch of years, or just happen to hit winter for a long stretch of years.  That's aliasing, and will show you imaginary hot spells and cold spells.  Just as imaginary as the stagecoach wheels running backwards.
  About the best you can do with this under sampled data is divvy it up into convenient slices, say 100 years each, and take the average over each 100 year slice.  Then you can look for temperature changes from century to century. 

Saturday, January 12, 2019

Microbrewers hung up by the Shutdown

According to today's Wall St Journal, micro brewers need approval from some federal bureau or other before they can market new brews or new labels.  The brewers have thousands of gallons of suds sitting in tanks, waiting for that bureau to come back to work and do their paperwork.
   Sounds like a severe case of micromanagement to me.  I don't see why brewers, or any other company, except maybe drug companies,  need federal bureaucrats to approve labels, recipes, packaging, or anything else.  If the customers don't like the new recipe or label or whatever, they will stop buying the product.  That ought be enough to keep the brewers and other companies  making good stuff.