SpaceTEC® Resource Blog for Aerospace Technicians

Archive for December, 2010

Can You Measure Up?

A Weights and Measures office in England

When I watch the International Space Station fly overhead, I am always amazed at what a piece of craftsmanship it truly is.  Is it because of its large size or how high up it is?  No, not really.  It’s the fact that each and every piece was built in over 1 dozen countries by thousands of people and brought together for the first time 250 miles up in low Earth orbit.  The chances of everything fitting together the first time would be astronomical (and it did fit together the first time!) if it wasn’t for one thing, the standardization of measurement.

With things such as the ISS, the various countries involved use the United States Customary System of measurement.  In fact, as stated on the ISS tour at KSC, the ISS is the last international space project involving the USA that will use this system of measurement.  Afterwards, all international space projects are to be done in the metric or SI system.

Currently the USA uses the United States Customary System as its standard of measurement.  The rest of the world uses the International System of Units (SI or commonly known as “metric.”)  In 1959, an international standard was agreed upon so that both standards could be easily translated back and forth.  The table below shows a good example of conversions for common measurement between the American and SI standards.

Unit Divisions SI Equivalent
Exact relationships shown in boldface
inch (in) 2.54 cm
foot (ft) 12 in 0.3048 m
yard (yd) 3 ft 0.9144 m
mile (mi) 1760 yd 1.609344 km

The standardization of measurement is a basic building block of a successful civilization.   You cannot have trade, buildings, or complicated machinery without an agreed upon standard of measurement.   From standards on length, volume, etc. societies cannot function without some standard of measurement.  The next time you go to fuel your car, look at the gas pump.  Somewhere on the pump will be a stamp from an official state office certifying that the pump meter is in accordance with standards of measurement when it calculates flow of gasoline being pumped into your car.  This ensures the fair trade in your purchase of gasoline.

Many ancient societies had standards of measurement.  Some small villages that dealt in trade would post their “standards of measurement” on a board in the village square, while larger governments and cities would actually set up standards of measurement by decree and have officials to enforce the standards.

The earliest known examples of standards of measurements came from the 4th and 3rd mellennia BC from the civilizations of Indus Valley (covering modern day parts of Pakistan, India, Iran, and Afghanistan, Egypt, and Mesopotamia (covering modern day parts of Iraq, Syria, Turkey, and Iran).  Probably the most common story of government setting standards of measurement is the story of King Henry I of England, who ruled England from 1100 to 1135.  The standard for the “foot” was supposed to have been made by measuring the King’s foot.  This practice had been going on before his rule, but it appears that new rulers would frequently want to leave their “mark” in some way in the culture, and this was one way of doing it, hence the “foot” and quite likely the term “ruler” for the stick showing a foot.

So what can happen if standards are ignored or the wrong standard is applied?   Much can happen such as unfair trade practices, building collapses, machinery that cannot have interchangeable parts, and one famous example of a multi-million dollar spacecraft being lost.

Aerospace technicians working on the Mars Climate Orbiter. Credit

The Mars Climate Orbiter was launched on December 11th, 1998 as part of a two spacecraft team (the other being the Polar Lander which was also lost) and was declared lost September 23rd, 1999.  It was discovered that the loss of the spacecraft (total program cost of $327.6 million) was due to the wrong measurement standard being used.  Lockheed Martin was responsible for the thrusters and had used United States Customary Units to calculate the thrust in pound force.  The main computer was expecting the calculations to be in newton’s based on SI standards resulting in the spacecraft underestimating it’s thruster effects by a factor of 4.5 (1 pound force is equal to 4.5 newton’s) .  The software error was never caught during ground testing and the entire spacecraft ended up dipping too low into Mar’s atmosphere during orbit insertion causing the spacecraft to burn up.

The importance of having a standard of measurement cannot be stressed enough.  Because of these standards, a meter or foot means the same throughout the world ensuring fair and accurate trade, collaboration on international projects, and someday a human return to the Moon and on to Mars.

For more information try:


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Friday, December 31st, 2010 History, Introduction to Aerospace, Tests and Measurements Comments Off on Can You Measure Up?

Dr. Al Koller on The Space Show

Dr. Al Koller

Dr. Al Koller, of SpaceTEC, was recently interviewed by Dr. David Livingston on The Space Show.  Dr. Koller spent the 1 and ½ hour interview discussing the founding and purpose of SpaceTEC, the importance of aerospace technicians and the need for national certification, and also discussed the uncertain future of America’s Human Space Flight program.  You can listen to the interview here.


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Tuesday, December 28th, 2010 SpaceTEC Comments Off on Dr. Al Koller on The Space Show

Liquid Fueled Rocket Engine Basics

Bi-propellant rocket motor Credit NASA

As an aerospace technician you may find yourself around liquid fueled rocket engines daily or as in some cases of SpaceTec alumni, actually working on them.  Either way, it is a good idea to know some basics about these engines, especially the more common bi-propellant engines.


Liquid fueled rocket engines were first proposed by Konstantin Tsiolkovsky in his book The Exploration of Cosmic Space by Means of Reaction Devices published in 1903.  It remained a theory until the first successful flight by a rocket named “Nell”, lasting only 2 and ½ seconds and traveling 41 feet, done by Robert Goddard on March 16th, 1926.

Goddard and “Nell” Credit NASA

What is a bi-propellant liquid fueled rocket engine?  Well, as the name describes, it is a rocket engine that is fueled by a liquid fuel and a liquid oxidizer.   The entire set up is deceptively simple and consists of two tanks to hold the fuel and oxidizer, two turbo pumps, a combustion chamber, and a nozzle.

The two tanks can be small such as what was on Robert Goddard’s rocket or can be as large as the External fuel tank on the Space Shuttle system (which holds the tanks for both the fuel and oxidizer in one large shell).

The pumps are critical in pushing the fuel and oxidizer to their explosive meeting in the combustion chamber while maintaining adequate pressure to ensure proper flow rate and to prevent the combustion chamber from collapsing under its own weight due to atmospheric pressure.  As Dr. Jerry Grey wrote in his book Enterprise, “Much of the difficulty with liquid-propellant rockets arises in maintaining constant flow and rapid, efficient mixing of the propellants…the need for tanks heavy enough to withstand the pressure dictated the use of pumps instead…pumps the size of washing machines which had to have the power of a diesel locomotive…” (Grey, Ph.D., 1979)  One of the factoids listed at the Kennedy Space Center Visitor Center Launch Gantry says that one turbo pump from one Space Shuttle Engine (SSME) can actually drain an Olympic size swimming pool in just 25 seconds.  That’s a lot of fuel being pushed along the pipes leading into the combustion chamber, yet it takes all three Space Shuttle Main Engines nearly 8 minutes to drain the External Tank!

The combustion chamber is where all the action happens.  This is where the fuel and oxidizer meet and combust forming the explosive energy required to lift the rocket.  “Chamber walls less than a sixteenth of an inch thick that withstood pressures of one hundred atmospheres and temperatures of 6,000 F.” (Grey, Ph.D., 1979)  Basically an explosion occurs that is continuous as long as there is fuel or until the engine is shut down.  This is why it is said sometimes that a rocket launch is nothing but a vehicle or payload riding a controlled explosion.

After the fuel combusts the resulting energy has to go somewhere or the chamber will explode.  The resulting energy or flame exits out the familiar nozzle we see on all rockets.  Nozzles experience great heat from the flames and actually have to be made of a material that can withstand it and/or have a way of being cooled so they can maintain their shape and form during the launch.  The nozzles for the SSME’s actually have some of the liquid hydrogen routed through tiny radiator tubes lining the nozzle using the super cold liquid hydrogen to keep the nozzle cool and to warm the hydrogen before it reaches the combustion chamber making it easier to ignite.

As I said, deceptively simple but as many technicians and engineers that have worked on these engines for nearly 100 years now can attest, this “simple” system has resulted in many exploded rockets and engines (and some loss of life) during the trial and testing that still goes on today.

For further learning about this subject:

Grey, Ph.D., J. (1979). Enterprise. New York: William Morrow and Company, Inc.


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Tuesday, December 14th, 2010 History, Introduction to Aerospace Comments Off on Liquid Fueled Rocket Engine Basics

Interview Tips and Techniques For The Aerospace Technician

With the major changes in Human Space Flight due to the end of the Space Shuttle program, many aerospace technicians are dusting off and updating their resumes.  But, how many of you have gone over interview techniques lately?  A good resume can land you an interview, but it is the interview that lands you the job.  Your interview technique has to be as good as or better than your resume.  After all, this is the first time a representative from the company you’re applying too will see you face to face and it is of the utmost importance to give a great first impression.  Below are some tips and techniques I have found successful in the past and may be of some benefit to you.

  • Dress for success.  When I first moved to Florida over 13 years ago, and started interviewing for jobs, I would show up in a nice suit as I was taught to do when I was a younger man.  I was surprised to find myself competing with other people who showed up for their interview wearing shorts, tee-shirts, and flip-flops.  Trust me, I’m not exaggerating.  These people ended up having very short interviews, usually lasting less than five minutes, and were not hired.  A good rule of thumb to use when interviewing for a job is to dress one step above the position you’re applying for.  If it is a technician’s position and their normal wear for the job is jeans and a shirt, then you should be wearing at least dress slacks and a dress shirt.  Of course, wearing a suit and tie is even better.  Don’t forget to shine your shoes either.  I’ve learned working in the aerospace industry that many managers are former military and they do pay attention to your shoes.  So learn to shine your shoes like the guys in boot camp.
  • Hygiene: Dressing for success also means showering and shaving before the interview, so don’t forget to wash behind your ears and to shave away that five o’clock shadow.  Make sure you clean your fingernails too.
  • Research the company.  If you want to work for a certain company, you should know something about them.  Go to their website and learn about the company, its type of business, its goals, mission statement, etc.  You want to be a team member, so you need to know about the team.
  • Research the job you’re applying for.  Talk with people who already do the job, research the position on the web, learn the average salary for the position as it relates to your experience level, etc.  Coming into the interview with a good, solid, basic knowledge of the job and its expectations will give you a leg up on the competition and grant you the ability to ask better and more knowledgeable questions.   This shows the interviewer that you have initiative to learn on your own.
  • Speaking of questions, make a list of questions to take in with you.  Have questions about the job, work environment, dress code, benefits, etc.  If you are interviewing with the person who would be your boss, ask him/her what they expect of you and what their management philosophy is.
  • Remember, an interview is actually a two way street.  The company is there because they want to learn more about you and you are there to learn more about them.  By asking educated questions and keeping those questions positive you will learn quickly if this company is a good match for you or not.  I’ve actually had interviewers get hostile over my questions and I have ended those interviews on my own initiative because I knew they would not be a good match for me.  Other interviewers have been pleasantly surprised at my questions and took a large amount of time to answer them fully.  Also look at the interviewer’s appearance and conduct.  Are they professional?  Do they represent their company well?  Do they treat you with respect?  If not, these should be taken as warning flags that you might want to reconsider working for them.  No one says you have to accept every job that is offered to you.
  • Be prepared to answer any question fully and in as much detail as possible.  That does not mean tell your life story, but stay on topic concerning the question.  Such questions as “What are your strengths and weaknesses?” are classic ones that are asked.  Start out with a specific weakness and what you are doing to correct it and always end on your strengths.  For example, you could say that time management is a weakness of yours, but you are currently reading a book on time management to learn new tips and techniques to strengthen that skill.  You might even ask if the company has any educational programs in house that teach better time management skills.  Never give general answers without having specific examples to back them up.  Saying, “I never call off work” and backing it up with, “At my last job I went 3 years without a sick day” is a good example.
  • Stress that you wish to continue your education.  This shows that you won’t be idle and content with “just a job” but are looking to improve yourself and in turn improve the company.  Ask about tuition reimbursement programs and if the company has an in house education department.
  • Don’t forget about hobbies.  Some employers during an interview want to know what you like to do in your spare time.  And, make sure you can point out that the skills you use in your hobby can be useful in the job you’re applying for.  For example, I think the two main reasons I got hired into the Space Shuttle program was my Aerospace Technology degree and my hobby, which is model building.  I told my interviewers that my hobby taught me how to do small precise work, and to read and follow instructions/processes to the letter.  These turned out to be skills that were very much applicable for working on the thermal protection system of the Space Shuttle as a technician.
  • Always be pleasant and rested for the interview.  Not getting enough sleep or having a bad day affect your mood will end up being reflected during your interview.  Make sure you are well rested, have eaten, and in a good mood prior to the interview.
  • Never, never speak ill of your past employer.  Even if you did not have a good relationship with your past employer, keep the hard feelings away during the interview.  If you speak ill of your past employer, then the prospective employer will assume you will speak ill of them someday.
  • Be frank about your past work history if there is something negative there.  If you were fired, and it comes up during the interview, be frank about why you were fired, and what you have done to correct that behavior to ensure it doesn’t happen again.   If you have been laid off for an extended period of time, then make sure you have something going on in your life to show you were active during that time period and not just sitting around idle collecting unemployment.  Talk about volunteer work you did, a side business you did, etc. during that time unemployed.  Never allow your resume or your interview to show you as being idle and having no initiative.
  • Always have a notebook and pen to take notes with during the interview.  Also, bring at least two copies of your resume with you, one for you to refer too and one for the interviewer to look over in case he lost his copy (It has happened many times in my experience.).
  • Always use the “King’s English” when speaking.  Other words, watch your grammar and spelling.  Fair or not, people will judge you by your grammar and spelling.  Poor grammar such as slang, cursing, etc. along with poor spelling (Learn how to use spell check!) tells an interviewer that you might not be so bright or care about your linguistic appearance.  Proper grammar and spelling are just as important as the clothes you wear to an interview.
  • Don’t be afraid to negotiate.  It never hurts to ask for a better salary, but be prepared to back it up with good solid reasons as to why you deserve a better salary than being offered.  Some aerospace companies will negotiate with you, especially if you have experience.
  • Always write your interviewer a thank-you note the next day after the interview even if you don’t get the job.  Remember, he/she took time out of their busy day to talk with you and it is only courteous to tell them “thanks.”  You may not get hired this time, but if you apply again later on for another position at that company, that interviewer will remember your courtesy.
  • Learn from the interview no matter if you’re hired or not.  What did you do right?  What can you do better?  List all the questions you can remember being asked and keep them in a notebook.  It is a good chance that many of those questions will be brought up again someday at another interview.  This way you can improve your chances by being better prepared the next time.

This is not a full list of interview techniques, but it should give you a start.  Talk with managers you know and ask them what they look for in interviews and research it on the web or in books.  And, if you have any other techniques you wish to share, please feel free to share them in the comments section.  Good luck!


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Wednesday, December 1st, 2010 Career Advice, Introduction to Aerospace Comments Off on Interview Tips and Techniques For The Aerospace Technician