A common tool that is used by the aerospace technician is the torque wrench. The purpose of the wrench is to precisely place the required amount of torque or tightening of a nut on a bolt without under or over torquing the nut. It is a misconception that people believe that “the tighter the better” applies to all nut/bolt arrangements. That is not true. Over-tightening a nut can crush the gaskets underneath, warp the bold threads, or cause the nut to be difficult to remove. Under-tightening can result in the nut coming off at an inopportune time. Using a torque wrench, you ensure that the nut is at the proper torque that is required avoiding damage or breakage.
There are four major types of torque wrenches an aerospace technician can use: Flexible beam, Rigid frame with a dial indicator, preset or “clicker” torque, or digital.
Flexible beam is used by grasping the center of the handle, turning the nut until the needle points to the torque desired.
Rigid Frame torque wrenches use a dial indicator to read the torque being applied.
Preset or “Clicker” torque wrenches can be set to the desired torque and will “click” when the proper torque is reached. The unit showed above can be set for either english standard or metric.
Digital torque wrenches will show the torque being applied via a digital readout and some models will actually beep when you have achieved the torque desired.
When using a torque wrench, keep these things in mind:
- Select the proper wrench for the measurement being called for. If inch/lbs are called for, then you select a inch/lb wrench. If inch/grams are called for, then select a wrench that is measured in grams.
- Check the calibration date on the wrench. If it is outdated, return to logistics and get a wrench that is within the calibration date.
- Always test the torque wrench on a torque measuring device to ensure that it is still calibrated and reading accurately.
- Never jerk the wrench, but pull on it slowly keeping close eye on the torque being applied.
- Always set the wrench back to it’s lowest torque setting after use to ensure that the spring does not compress and end up with “memory.”
- Always handle torque wrenches with care. Do not drop them or bang them around. Return them to their foam case once finished.
Torque is determined by the formula:
Torque=force X distance
For example if a an engineering drawing requires a 120 lb inch pound torque for a specific nut and you have a 10 inch torque wrench, you would figure out the following:
120 inch/lb=force X 10 inches
120 inch/lb divided by 10 inches=force X 10 inches divided by 10 inches
or 120 inch/lb divided by 10 inches= force
Therefore you need 12 lbs of force to achieve 120 inch/lbs using a 10 inch torque wrench.
This formula is very useful in determining the torque required.
Some technicians have been known to alter the length of their torque wrench by adding an extender. If that is done, then the force required to achieve 120 inch/lb of torque is changed. Let’s look at the same problem again and assume the aerospace technician has decided to add a 15 inch extender on his wrench.
120 inch/lb=force X (10 inches (wrench length) + 15 inches (extension length))
120 inch/lb=force X 25 inches
120 inch/lb divided by 25 inches=force X 25 inches divided by 25 inches
120 inch/lb divided by 25 inches=force
Note the difference in force required! If you had not taken into account the added length of the wrench, you would have over torqued the nut possible resulting in damage to the aerospace hardware.
With good care and timely calibrations, your torque wrench should last and be an invaluable tool in your work.
Today we are going to wrap up our safety series. We have covered the purpose of safety in the workplace, appropriate safety dress, and housekeeping. Now we will cover safe work practices and fire prevention.
Safe work practices always involve knowing your surroundings. You should always keep your “head on a swivel” so to speak. Who is near you? What are they doing? Is there a potential for their work or your work interfering and causing a safety hazard? Do you have some form of safety barrier up such as a rope or sign while doing a hazardous function to prevent other workers from inadvertently walking into your work area? If working at a height, are you tied off with a harness and rope? Do you have a catch basin or net below to catch falling objects?
When lifting a heavy object, are you using safe lifting practices? Don’t be a “he-man” when lifting a heavy object. Ask for help. Always protect your back. You only have one. Safe lifting practices include:
- Check your immediate area to ensure it’s clear of any obstacles that may cause tripping.
- Assume a squatting position with the knees bent and the back straight.
- Pull the object you are lifting in towards your body. Don’t keep it extended out from you causing an imbalance.
- Lift using your leg muscles and not your back.
- If you must set the object back on the floor at another location, do the safe lifting practice in reverse keeping your back straight and using your legs.
Another way to protect your back is to always try to do your work at a waist level or slightly higher bench. Some parts that you’re working on can be placed on a bench and is more favorable to your back then bending over constantly doing the work. If the part you’re working on is below your waist and you cannot lift it onto a bench, then consider kneeling or squatting while doing the work, taking frequent breaks to stretch your legs.
Though we might enjoy working with our co-workers, horseplay is just out of the question. In an industrial setting, there is just too many opportunities for an accident. People do get hurt during horseplay and is not appropriate for the workplace. I once saw a young woman who was employed at a water park get injured during horseplay. It was the last day of the season and a group of employees were horsing around chasing each other with squirt guns. The girl slipped on the wet pavement and ended up getting reconstruction surgery on her face due to her injuries. A bad ending to an otherwise celebratory day for the crew.
Also make note where the eye wash and shower stations are. Do you know how to operate them? If not, request an inservice on it.
Do you know where the fire extinguishers are at your workplace? Do you know how to work one? Are the extinguishers visible or hidden by clutter? Are their inspection stickers up to date?
You should also know where the ELSA masks, exits, and marshaling areas are. In the event of an emergency requiring evacuation, you should already have an idea where to go and how to get there.
Safety is an everyday practice for the aerospace technician. Though it is the responsibility of your employer to provide safety equipment, training, etc., it is your responsibility to practice safe habits and to expect it of your co-workers. Remember, the ultimate goal of each and every work day to return home to your loved ones unharmed after each shift.
Housekeeping: Organization and tidiness in general, as of an office, shop, etc. – Collins English Dictionary
For many people, when the term “housekeeping” comes up, they usually have a vision of chasing dust bunnies around the house, but housekeeping is not just for the home. Your workplace is your “home away from home” and housekeeping carries a much more important role for it affects not only your safety, but the safety of others and has a direct impact on the quality of work being produced.
Housekeeping is an essential task in the workplace for the aerospace technician. Proper housekeeping ensures safety, mitigates fire hazards, increased work productivity, reduces unnecessary repairs, and helps with tool control. Without housekeeping the workplace would eventually come to a grinding halt. Poor housekeeping encourages trip hazards, FOD hazards, fire hazards (both by being possibly flammable itself and/or blocking access to fire fighting equipment and exits). Oil and grease not cleaned up could ignite if exposed to a hot area of a machine or be a slip hazard if left on the floor.
Housekeeping is not something that is just done at the end of the shift. It is an ongoing task that you do alongside your job. The term “Clean as you go” refers to proper housekeeping while doing a job. If you pick up trash, put away tools when not being used anymore during the job, and keep your work area trip and hazard free during your task, you are practicing “Clean as you go.” No one wants to work beside the person who’s standing knee deep in his trash with his tools scattered all about and even encroaching into your workspace interfering with your task.
So how can you “clean as you go” in the aerospace workplace? Ensure you throw away all trash created during your job as you produce it. That requires having some sort of trash receptacle nearby that is designated for trash only. Cap all open bottles/cans when you are not using them at that moment to avoid accidental spills. Clean up all grease and oil spills as they occur; don’t leave them on the ground or hardware with the intention of “getting to it later.” Put tools away or return to logistics if your not using it anymore for the job. Stage equipment and supplies for your job that you will need later near, but not in, your work area in a orderly grouping out of the way of traffic and other people’s work areas.
If you are operating a machine in a shop, there are a set of housekeeping rules that apply to it as laid out by the book Technology of Machine Tools:
- “Always stop the machine before you attempt to clean it.
- Always keep the machine and hand tools clean. Oily surfaces can be dangerous. Metal chips left on the table surface may interfere with the safe clamping of a workpiece.
- Always use a brush and not a cloth to remove any chips. Chips stick to cloth and can cause cuts when the cloth is used later.
- Oily surfaces should be cleaned with a cloth.
- Do not place tools and materials on the machine table. Use a bench near the machine.
- Keep the floor free from oil and grease.
- Sweep up the metal chips on the floor frequently (clean as you go!). They become embedded in the soles of shoes and can cause dangerous slippage if a person walks on a terrazzo or concrete floor. Use a scraper, mounted on the floor near the door, to remove these chips before leaving the shop.
- Never place tools or materials on the floor close to a machine where they will interfere with the operator’s ability to move safely around the machine.
- Return bar stock to the storage rack after cutting off the required length (clean as you go!).
- Never use compressed air to remove chips from a machine. Not only is it a dangerous practice because of flying metal chips, but small chips and dirt can become wedged between machine parts and cause undue wear.”
As you now know, housekeeping is an essential part of safety in the workplace and should be practiced at all times. There is no need for a maid’s uniform to be a good housekeeper in the shop, just an awareness that everything has it’s place and and should be clean and ready for use the next time.
“Accidents don’t just happen; they are caused. The cause of an accident can usually be traced to carelessness on someone’s part.” – Technology of Machine Tools 5th Edition
Before an aerospace technician starts working a new job, he or she must know what is the required dress code for safety in that work area. Most companies will address that issue during orientation or you can inquire about it with your supervisor or manager. Most aerospace technicians will be working in an industrial setting and there are some typical considerations you have to make when dressing for safety.
Being a man that is follicle challenged, I have always envied my fellow co-workers who actually had to carry a comb and knew how to use it. But, in a shop setting I had one major advantage over them; I didn’t have to worry about my hair being caught in moving machine parts. Getting your hair caught in a moving machine part not only results in a suddenly becoming follicle challenged, but can also result in the loss of your scalp and/or having your entire head pulled into the moving part resulting in a very bad day. If you’re working around moving machine parts, you should use a hair net, hat, or some other way of ensuring your hair is well out of the way and not at risk of being caught up in the machinery. And since it is likely you will be working around aerospace components as an aerospace technician, it is good work practice to keep those components free of contamination from loose hair.
Eye protection is imperative when working in an industrial setting. The risk of your eyes being struck by a flying piece of debris such as a burr while using a drill press to the risk of a chemical splash is too great. You have only two eyes and your vision needs to be jealously protected. Your employer should tell you what particular type of eye protection you should be wearing for a particular job (safety glasses, goggles, face shield, etc.), but it is always prudent to at least wear safety glasses in an industrial setting even if you’re not doing any work with machinery at the time.
One thing that should be mentioned about safety glasses. Your safety glasses should always be marked as such, don’t think just any old pair of glasses will do. Safety glasses are usually made of tempered glass that has been tested to withstand impacts up to a certain force and usually has side guards to prevent debris from entering your eyes from the side. If the glasses are not certified as safety glasses, then don’t use them. The glass in your ordinary eyeglasses will not do.
I was watching a “Do it yourself” type show the other night and they were featuring people that probably should never pick up a hammer, let alone operate power tools. One young man was working with a hazardous chemical to strip some furniture and I will give him credit for reading the instructions, but that is the only credit to his favor he got. The instructions called for safety goggles and other protective safety clothing to prevent chemical splashes from getting on his body and he decided that his dark sunglasses were good enough for the job and the only thing he needed. He looked cool while doing the job, but when the inevitable chemical splash that resembled a tidal wave occurred while he was transferring the chemical from the large awkward container to a smaller container without the use of a funnel and assistance, he ended up with chemical burns to his eyes, face, and arms resulting in a trip to the hospital.
How you dress your body will impact your safety. If you are working around moving machine parts, you should not be wearing loose clothing that can get caught up in the part. Same goes for long sleeves. Roll up those sleeves or wear a short sleeved shirt. Shop aprons should be tied in the back where the strings can be kept away from the machine and work area. Though gloves are an integral part in your safety wardrobe for many jobs, they should NOT be worn when working with moving parts. If you are unsure as to what to wear in your work setting, talk with your manager.
Jewelry: simple, leave it at home or in your work locker. The shop floor is not the place to make a fashion statement and jewelry, especially rings, have been the cause of many lost fingers and other injuries. Jewelry can also become a FOD hazard if they come off. It is just best to leave it off the shop floor.
What you wear on your feet in the shop setting is important. No open toed shoes should ever be worn in an industrial setting. You may be allowed to wear tennis shoes depending on the work setting, but steel toe safety shoes or boots are usually best practice. Also, make sure your shoes are tied. That may sound funny, but think how many times other people had to tell you your shoes were untied because you weren’t aware of it. Double knot the laces to ensure you don’t end up tripping and falling to the floor, into machinery, or onto flight hardware, etc.
Remember, your goal at work is not only to get the job done, but to ensure that you and your workmates all get to go home at the end of your shift. Make sure your mode of dress helps you achieve that goal.
I grew up in West Virginia known for its coal mines. Accidents at coal mines were a fact of life, but I noticed personally working as a paramedic during those days, and had also read in various accident studies, that the majority of fatal accidents occurred to two distinct populations most of the time inside a coal mine: the very new employee and the very experienced employee that was near retirement.
The new employees were susceptible to accidents. Coal mines are dangerous places with a large amount of safety rules to learn and follow. New employees would sometimes forget those rules or not take them too seriously with fatal results.
What surprised me were the older and more experienced employees being involved in these types of accidents. It was found out that complacency played a large role in that. Men closer to retirement had gotten to the point that they thought they knew it all and didn’t have to be as careful as the new guys.
My father worked nearby at a large power plant that could be an unsafe place if you didn’t follow the safety rules. He had seen 3 or 4 men get killed because of safety lapses during his 35 plus years there. When he chose to retire early, I asked him why. He said, “I don’t want to be carried out feet first from work someday on a stretcher.” He knew that complacency was sneaking up on him and thought it was time to leave.
When I started at KSC, it was the first time I had worked in an industrial setting and I found that I spent more time in safety classes than all my other classes combined. With all the dangerous propellants there such as Mono Methyl Hydrazine (2 breaths, 2 steps, you’re dead.), large equipment, heights, etc., there, you had to know quite a bit about safety.
But KSC took it further. It was ingrained in their culture, and a normal farewell saying done by everyone was, “Be safe.” We had safety meetings, daily safety tips, safety emails, constant safety classes, and on and on. You could bring an entire job to a skidding stop by just saying, “I have a safety concern.” My old manager, Jay Barati, told me once that each day that everyone finishes their shift and goes home to their families is a good day.
I kidded with a co-worker one day after I had been there for about 2 months, “that these guys treat safety like a religion!” After my first brush with a MMH leak while working near the forward reaction control system, I became a staunch convert myself.
Safety begins with you. You are not only responsible for yourself, but for your co-workers. Nothing could be worse than to know that your lapse in safety caused an injury to your co-worker. Everything from your dress, conduct, and work habits should have safety as the guiding force.
We are going to start a series on safety. Of all things you take away from your aerospace courses, safety is the most important. The lessons you learn can literally save your life. Stay tuned!
Continuing our series on measurement devices, today we are going to discuss Gage Blocks. Gage blocks are rectangular blocks usually made of hardened steel or zirconia ceramics. The surfaces are flattened and polished to a tolerance of only 2 to 8 millionths of an inch.
The purpose of gage blocks is to measure things to an astonishing accuracy. Gage blocks are used to determine the accuracy of fixed gages while checking to see if those gages have experienced excess wear or any other form of alteration, calibrate various adjustable gauges, to set up machine tool settings, and to measure the accuracy of finished parts.
There are three classes of gage blocks:
- Class AA – also known as the laboratory or master set. They are accurate to within +/- 0.000002 in and +/- 0.00005 mm. These gages are used in climate controlled settings to ensure the accuracy of lower class gage blocks.
- Class A – used for inspection purposes, they are accurate to within +/- 0.000004 in and +0.00015/-0.00005 mm.
- Class B- are commonly known as a “working set” and are used most often in shop settings for machine tool setups, layout work, and measurement. They are accurate to +/- 0.000008 in and +0.00025/-0.00015 mm.
Gage block sets can come with only three or four blocks to sets that number up to 115 blocks. The typical English gage block set consists of 83 blocks and two wear blocks. The wear blocks can be either 0.050 in or 0.100 in. The most common metric sets consist of 88 pieces with two 2 mm wear blocks.
Wear blocks are stacked on each end of the gage block set when measuring and are designed to take all the wear and erosion that occurs during the lifetime of measuring using the set therefore prolonging the set’s usefulness. NEVER place a non-wear block on a work surface that you are measuring. Work surfaces can contain minute amounts of abrasives that will degrade the accuracy of your blocks over time. Always use wear blocks on each end of the stack, with the same face of the wear blocks touching the surfaces all the time. Most wear blocks are marked so you not put the wrong face on the item you are measuring.
Gage blocks are designed to be used in environments that are climate controlled. Most blocks dimensions are set in a temperature of 68 degrees F (20 degrees C). For every increase of 1 degree F (0.5 C), a typical 4 in stack of gage blocks will expand approximately 0.000025 in. With the human body temperature being about 98.6 degrees, it is important that not only a climate controlled facility be used when measuring, but that the aerospace technician limit his contact with the blocks either by holding them by your finger tips as little as possible or using insulated tweezers. The work area that is being measured should also be the same temperature as the blocks in order to obtain the best accuracy. Some manufacturers suggest you go the extra step and use insulated gloves along with the insulated tweezers. If the part being measured and the blocks are not the same temperature, some books suggest you immerse both items in kerosene until they are equalized. That of course may not be practical due to fire hazards or the size of the part being measured.
To save time and reduce the chance of error when using gage blocks you should use as few blocks as possible. There is an actual procedure advocated by the authors of the book, Technology of Machine Tools, to use when calculating the exact blocks you will need to make a measurement.
Step One: Write the dimension required on a a piece of paper.
Step Two: Deduct the size of two wear blocks.
Step Three: use a block that will eliminate the right-hand digit.
Step Four: Use a block that will eliminate the right-digit and at the same time bring the digit to the left of it to a zero or a five.
Step Five: Continue to eliminate the digits from the right to the left until the dimension required is attained.
Now to see this in action, here is an example in the table below:
As you see in the left hand column, you are subtracting the blocks from the desired measurement while in the right hand column you are adding the block’s measurements together. You should achieve a “0″ in the left hand column and the desired measurement in the right hand column if you have done your math correctly.
Gage blocks surfaces are flattened so accurately, that they can actually “stick” together and withstand a pull of up to 200 lbs! It is not known exactly why that is though some have suggested it is either a molecular bond or due to the slight film of oil left over due to cleaning. To stack or “wring” gage blocks together, you must first clean the blocks with a clean, lint free, and soft cloth. Wipe the contact surface area of the block on the palm of your hand or wrist. This has two functions; One, to wipe any remaining particulates from the block onto your hand using the oil from your skin to “grab” the particulates, and two, also using the oil from your skin to “lube” the blocks. Place the end of one block onto the end of the other block and while using pressure, slide the blocks together. They should stick together. If they don’t, then the blocks were not properly cleaned.
To take care of your gage blocks and ensure that they have a long life, you should:
- Keep the case closed at all times except when you are getting a block or placing back a cleaned block.
- Do not play dominoes with them.
- Do not unnecessarily finger the surfaces of the block to avoid rusting and tarnishing due to your skin oils and moisture.
- Do not drop the blocks or scratch the surfaces of the blocks.
- Do not use them in your juggling act at the comedy club.
- Immediately after use, each block should be cleaned, oiled, and placed back into the box. (Don’t forget to close the box!)
- Never leave your gage blocks wrung together! Leaving them this way will encourage rusting from the oils and moisture from your skin.
The Quality Technician’s Handbook (Griffith, 2003)
Technology of Machine Tools (Krar & Check, 1997)
The most common and overlooked measuring tool is the steel rule or ruler. Steel rules can be in inches or metric with sub-markings as precise as 1/64 of an inch or one millimeter. Steel Rules come in 4 types: spring tempered, flexible, narrow, hook, and short-length rules.
Spring tempered steel rules are the most commonly used in aerospace shops. These rules are usually 6 inches in length and made for quick reading. Usually they are broken into 4 scales, two on each side. For English measurements, one side of the rule will have graduations in eighths and sixteenths, and the back is graduated in thirty-seconds and sixty-fourths. Some spring tempered rules will have English measurements on one side and metric on the other.
Flexible steel rules are more commonly found in construction and in the home. They are also commonly called tape measures.
Narrow steel rules are used to reach tight and hard to access places to measure.
Hook steel rules have a “hook” on the end that you can butt up flat against a corner or protrusion while measuring to ensure the rule doesn’t move.
Short-length rules are small rules that come in sets of four and range in size from 1/4 inch to 1 inch in length. These rules are placed in a holder and used to measure small parts or openings.
There are two major rules to follow when using steel rules to ensure accuracy:
1. Due to rules being worn on the edge over time and use, it is best to start your measurement from the 1 inch or 1 centimeter mark. Once you have your measurement, subtract the 1 unit you started at to get the final measurement.
2. Make sure the graduated markings are as close to the area of the part you are measuring to ensure accuracy. It is best if the graduated markings are actually touching the area your measuring to make it easier to obtain the correct measurement.
Steel rules can also be used to determine the flatness of a material. Lay the steel rule on it’s edge on a part, hold the rule and part up to a light. If light shows through between the part and the rule, then the part is not flat. If there is no light showing, then the part is flat.
Don’t underestimate the usefulness of the steel rule. It will be the most often used measuring tool in your tool box.
The Quality Technician’s Handbook (Griffith, 2003)
Technology of Machine Tools (Krar & Check, 1997)
That’s a good question for the student studying to become an aerospace technician and current aerospace technicians. With the ending of the Space Shuttle program, tens of thousands of aerospace technicians, engineers, scientists, and managers have been thrust into the job market in one large mass with limited jobs available. Many unemployed or soon to graduate aerospace technicians prefer to stay in Human Space Flight, but it is quite probable that our nation will not be launching astronauts on American launch vehicles for the foreseeable future, quite likely 10 years or more for a myriad of reasons. Though there is a deep well of talent in this workforce, it is difficult for the aerospace industry to absorb these workers all at once, especially the fledgling commercial HSF industry. The competition for jobs is fierce with so many thrust into the labor market in such a short time span. So where do you go from here?
There are always options available to the aerospace technician that they can pursue. Some are not as preferred as others in the beginning, but they do exist. We will explore some of those options in this post.
Look outside of HSF. Though Americans are not being launched anymore on American launch vehicles, unmanned launches are still occurring. Satellites, planetary probes, cargo vessels, and telescopes are still being designed, built, and prepared for launch. The rockets used to launch these payloads still require aerospace technicians. You may not think it is as glamorous as HSF, but it is still a job that falls within your education and experience. Not many aerospace technicians in this world can say over dinner conversation that they helped prepare or launch a rover to Mars. Why can’t you be that aerospace technician?
Look outside your area. There are many spaceports throughout the nation and the world. Those spaceports are covered in the previous post here. Continuing your career sometimes requires relocation. It is a fact of life for many professionals in this economy and should not be looked upon as a burden but as an opportunity. Many companies look favorably upon an employee who is willing to relocate to help the company succeed and it helps them to find the best talent in a larger pool than just the local communities.
Continue your education while waiting for the number of people looking for work to thin out. This serves two purposes: 1. It makes you more marketable by having more education, and 2. It buys you time as new aerospace programs get started and as the labor pool shrinks due to people moving away, being hired, retiring, or changing careers. This would be a good time to supplement your aerospace credentials with an A&P license, a B.S. degree, additional certifications, etc. SpaceTEC would be a good place to start in seeking additional certifications.
Start your own business. In difficult economies, sometimes the best way to find work is to create your own work. Some Space Shuttle Technicians have recognized various needs in the aerospace community and have started their own businesses to meet those needs. These needs may have been created by poor customer service from established companies, or it is a need that has not been recognized yet. Starting your own business is full of risks and should be approached with a well thought out business plan, additional studies on other aspects of business such as accounting and marketing, etc. The local Small Business Administration should be of assistance. Do not bet your life savings, home, etc. without a thorough understanding of what your market is and how you’re going to meet it. Most new businesses fail within the first five years, so think this through carefully before selecting this option.
Change careers. This is a radical option that not only requires you to possibly obtain new certifications or degrees outside of your area, but to be prepared to enter a new job on an entry level basis that most times include lower pay. It can be a rewarding move and you will be surprised at how many of your aerospace skills will be applicable in your new career. Everything from the aerospace culture, such as how to approach problem solving, working in large organizations, etc., to your actual skills you use on the job can benefit you in your new career. New careers to consider could be teaching industrial arts or other subjects, working in a non-aerospace industry, health care industry (especially technicians who work on medical equipment), to maintenance jobs. The possibilities are actually endless. Also, changing careers does not have to be permanent. As the job market in the aerospace world opens back up, you can return to aerospace and bring along the additional knowledge and experience you obtained while working outside of your first profession.
There are many other options out there besides the four listed and you don’t have to limit yourself to just these four. The point is to never forget that you always have options to succeed and thrive. The amount of options you have is limited only by your imagination and your drive to succeed. Treat this downturn in HSF as an opportunity to “problem solve” this obstacle to your career. It is not the end of the world and the skills you have already learned as an aerospace technician will be a strength you will always carry no matter where you go. The knowledge and experience you have obtained so far in your career is yours. You own it, you earned it, and you can use it in many varied ways.
By Dr. Al Koller
This week marks the end of an era in American space exploration. Bathed in history and befuddled with “politics as usual”, our human space flight program appears poised to take its place on the dusty shelves of the past, along with the Shuttle Program and everything that has gone before it.
Although I can understand the reasons surrounding the end of Shuttle and the beginning of new commercial activity, it’s amazing to me that folks act as though what is happening is different from anything that ever happened in the history of humankind. Bull…
How do you think Vasco da Gama felt when he was denied the chance to capitalize on his experience as the first to sail from Portugal around Africa to India? Portugal became an instant leader in the 15th century sailing world, only to fade into oblivion, never to regain the prominence it once held. Rome suffered the same kind of fate, along with dynasties and nations throughout history. If you look, you can find innumerable examples where choices that changed the world were made while ignoring what seems now as gigantic errors but which, at the time, were made with the best intentions.
While we watch in silence the choices being made today for our space program, no one really knows what paths that MIGHT have been opened to us will never see the light of day – at least not in our lifetime. What makes it even more difficult to accept are that (1) we do so with the full knowledge that our only path forward will require that we rely on an old enemy that was never a match for our best minds, and (2) we will cede to others a leadership role that was hard won and never really used to its full potential. We are better than that, and we know it… Why, then, are we allowing this to happen? We have options.
Space exploration for our country never spent one penny outside our atmosphere. Every bit of it paid salaries here on earth. Space never consumed more than it gave back in the form of spin-off technologies we all use every day without even knowing from where it came. The people who took those first steps in space were part of an adventurous few who carried the flag for the rest of us and made our country the idol of the rest of the world. Worst of all, we now have better technology than we could even dream of then, and there are no good reasons to allow ourselves to drift into complacency other than laziness and the lack of the will to lead. To surrender without a real plan for the future is madness…
If you care at all about where we are headed as a nation, take a look at a man who helped found the Civil Air Patrol a long time ago. His name is Gill Robb Wilson, and he wrote a poem called “The Will to Lead” that was published in a 1960 issue of FLYING magazine. Few will remember him or his poem, and even fewer will really care – but ignoring that lesson will leave us poorer and without any explanation for what we are about to see happen to us.
Whoever said that those living in democracy get what they deserve was probably right. That’s because we get what we choose, and we’ll have no one to blame but ourselves when history asks, as it did of da Gama, what in the world were we thinking when we abandoned our legacy in space.
R.I.P., NASA and our U. S. Space Program. What a ride it might have been.
The Will To Lead
Gill Robb Wilson
First published in Flying Magazine 1960
So long as this is a free man’s world
sombody has to lead;
Somebody has to carry the ball in word
and thought and deed;
Somebody’s got to knock on doors which
never have known a key;
Somebody’s got to see the things that the
throng would never see.
Hotter than thrust when the boost is hit,
somebody’s faith must burn;
And faster than mach when the rocket’s lit,
somebody’s mind must turn;
Somebody’s got to get the proof for what
the designers plan;
And test the dreams that the prophets dream
in behalf of their fellow man.
Somebody’s got to think of pay in terms
that are more than gold;
And somebody has to spend himself to buy
what the heavens hold;
Somebody’s got to leave the crowd and walk
with his fears alone;
Somebody’s got to accept the thorns and
weave for himself a crown.
It’s ever thus as the ages roll and the
record’s written clear–
Somebody has to give himself as the
price of each frontier;
Somebody has to take a cross and climb
to a rendezvous
Where a lonesome man with a will to lead
can make the truth shine through.
“On June 10, 2011, the SpaceTEC program received formal safety approval from the Federal Aviation Administration (FAA) Office of Commercial Space Transportation for the SpaceTEC Certified Aerospace Technician™ process, the first such approval of this kind.
Based at Brevard Community College on Florida’s Space Coast, SpaceTEC is the National Science Foundation’s National Resource Center for Aerospace Technical Education. Since 2004 SpaceTEC has offered the nation’s only performance-based, industry-endorsed certification for aerospace technicians in the United States.”
The FAA gave safety approval for the four current areas of the SpaceTEC program:
- Core Certification
- Aerospace Vehicle Processing
- Aerospace Manufacturing
The approval for all four areas is valid for five years.
You can read more of the announcement and what it means for the aerospace technician field here.
To the staff at SpaceTEC, well done!
Caliper tools are considered transfer tools because the measurement cannot be read directly. Caliper tools “make contact with the part (on the dimension being measured), are then locked in the measured position, and are measured with another tool…” such as a rule or micrometer. (Griffith 2003) With caliper tools being a transfer tool, it doesn’t matter if the part being measured is in English or metric form. The caliper tool is used to measure the part which then you can compare it to either a English or metric rule or micrometer.
Calipers can be also used as a go/no go tool. You would preset and lock a caliper against a rule or master part and do a “fit check” on your part to see if a part meets the measurement required.
Though Caliper tools are good for regular measurements they should not be used when accuracy of less than 0.015 ” or 0.39 mm is required. (Krar and Check 1997)
There are two basic types of calipers, outside and inside calipers.
Outside calipers measure the outside surface of a round or flat surface. The most common type of outside caliper is the spring joint caliper. To use a outside caliper you would:
2. Compare the caliper to a rule to determine the measurement or compare it against a Master Part.
Inside Calipers are used to measure the inside diameters of a circular object such as a pipe or to measure the inside width of a slot or keyhole.
1. Hold one leg against the bottom surface of the area your measuring with your finger.
2. Turn the adjusting nut until the second leg touches the opposite side and lock legs in place.
3. Compare the caliper against a rule or Master part, or for more accuracy, use a micrometer on the caliper.
Calipers are easy to use and very simple tools to add precision to your work. Don’t underestimate a caliper’s usefulness when it comes to your work.
If there are any other common measuring tools or some other aerospace technician subjects you would like to see covered, please feel free to email your suggestion and we will work to cover it here.
The first micrometer was invented by William Gascoigne in the 17th century to assist in measuring angular distances between stars while using a telescope. Jean Laurent Palmer of France developed the tool further in 1848 making it possible to use to measure hand held devices and therefore was originally named after him, the palmer, as it is still known today. In Spain it is still known as the palmer screw or tomillo de palmer.
By the late 1800′s the micrometer had been mass marketed into many machine shops throughout these United States. Though it’s form has changed many times and the objects it can measure can differ such as outside and inside diameters, and depth, the particular micrometer we will discuss is the one that measures in inches the outside diameter or the micrometer caliper.
The micrometer or “mike” can measure the diameter of an object within 0.001 inches. Some micrometers have an vernier added to them that allow the measurements to done at 0.0001. No matter the size of the frame of a micrometer, and some can get pretty large, the actual maximum area that can be measured is only 1 inch total.
The micrometer consists of the anvil (the fixed part of the measuring area), the frame, the spindle (the part that moves while measuring), the spindle lock (that locks the caliper in place after measurement in the event you are using it to compare parts or such), the barrel which has the quarter inch (0.25) lines, the sleeve, sometimes called thimble, which contains the lines for another quarter inch divided into 40 lines representing the 0.001, and the ratchet to use for fine tuning measurements.
“The scale of a micrometer ranges from 0 to 1 inch and is usually graduated in thousandths of an inch (think of 1 in. as 1000/1000). The sleeve of the mike (as it slowly pulls back) shows the numbers 0 1 2 3 4 5 6 7 8 9 0. Each of these numbers represents 0.100 (or 100 thousandths) of an inch…Now look at the thimble. Each line on the thimble represents 0.001, and there are number every five lines (or 0.005). One complete turn (revolution) of the thimble is equal to 0.025 in. So each revolution of the thimble is equal to one division on the barrel.” (Griffith, 2003)
The Stefanelli website has a great simulator of a inch micrometer that you can move with the mouse and it will tell you the readings while you practice. I would also suggest you find some old machine tool textbooks and look for exercises that will test you in reading the measurements. As I have said before, know your tool or measuring device before using it in your actual day to day use. Refer to the previous post for more general suggestions on measuring.
We are going to start a series talking about the use and type of measuring tools commonly used by the aerospace technician. In this part, we will cover the basics that are needed to keep in mind when selecting and using measuring tools.
There is an old phrase that says, “When the only tool you have in your tool box is a hammer, then every problem looks like a nail.” The same goes with measuring tools. If all you have is a ruler, then you have the tendency to measure everything with it. As we all know, various things such as surfaces, threads, thickness, etc. need to be measured which require a variety of measuring tools, from rulers, dial calipers, to gages.
Though accuracy is needed in the aerospace field, accuracy can actually be too much. When you have need of knowing the measurement of a part within 0.01 of accuracy, you do not need to use a tool that measures within 0.000001 accuracy. That much detail is wasteful and not needed for the task. “The rule of thumb is to select a measuring tool that is ten times more accurate than the total tolerance to be measured, or the tool can discriminate to one-tenth of the total part tolerance.” (Griffith, 2003) This is called the 10 % or 10-1 rule. So if you wish to measure something within 0.01 accuracy as called for by the tolerence listed on the process, you only need to measure ten times that accurate or 0.001 in order to follow the 10-1 rule.
When I took a chemistry lab in college, I had the instructor once comment that I was being too accurate in my measurements. I had taken that as a compliment at the time not understanding that his “tolerance” did not require as much accuracy as I was using in measuring my chemical compounds for the experiment. Though my outcomes were more inline with what the lab book had said we would come up with in the results of the experiment, I was always last to leave the class, and I missed the point that he wanted us to grasp the concept of the experiment, not the technique.
Know your measuring tool! What does it measure? What is the fixed end (reference) and what is the measured surface (movable)? Do you know how to read the measurement displayed? What are the divisons on it and what do they represent? You must be proficient with your tool in order to use and read the correct measurment.
Strive for accuracy and precision. “Accuracy is the difference between the average of several measurements made on a part and the true value of that part. Precision means getting the consistent results repeatedly.” (Griffith, 2003) If you are using the wrong tool during a measurement or reading it wrong, but getting consistent results, you have precision but not accuracy. That is because you are getting the same results each time, but the measurment process is inaccurate. But if you are using the right tool and reading it correctly, then you will get accuracy and precision.
Pay attention to the pressure used when measuring. If you use too much pressure or too little, you can get an less precise reading (especially if the pressure changes each time you measure) and therefore an inaccurate reading. Don’t use a micrometer like a C-clamp to hold a part in place. That is too much pressure and will affect the reading. Same goes for using too little pressure. If contact with the part is too light, then the reading is skewed. Always use consistent pressure.
Take care of your measuring tools. First of all, inspect the tool. Is there a calibration sticker on it stating when it was calibrated and when the calibration expires? Is the tool in good condition? Does all the parts of it work as expected? Is the tool clean of debris and dirt that could affect its use or the measurement? Has the tool been dropped? Have you tested the tool on a part that already has had its measurment determined? Has the tool been stored properly to prevent damage? Measuring tools should not be piled on each other and usually should be kept in individual cases. Is the tool showing any sign of wear, especially on the measuring and fixed surfaces?
Learning about and becoming proficient with your measuring tools will ensure that your work will be more consistant and error free. And, don’t forget the old adage when doing your work; “Measure twice and cut once!”
Sources: The Quality Technician’s Handbook by Griffith
Technology of Machine Tools by Krar and Check
In this video, Gordon Snyder talks with Al Koller, Carolyn Parise and Joyce McClellan from SPACE-TEC at the 2010 HI-TEC Conference in Orlando, Florida.
A recent interview with Dr. Koller from SpaceTEC.
The purpose of this blog is to be a resource for aerospace technicians and students covering various topics that relate to the profession from job issues, to a review of basic skills, etc.. We would like to invite the aerospace technicians out there to take some time and let us know what you are interested in seeing covered in Space Update. So, here is an invitation for you to send us your ideas! Remember, this blog is written with you and your profession in mind and we would like to hear from you. So, speak up and be heard!
Before you do send in your ideas please remember these guidelines:
- This is a site for aerospace technicians and students. So please no astrophysicist topics, politics, cooking questions, Dancing with the Stars applications, etc. Just aerospace technician topics folks!
- If you want to add your information/experience to the idea please do so! Just make sure you also give references if possible. We will make sure you get credit for sharing your knowledge.
- Aerospace technician instructors are welcome and encouraged to send in their ideas too.
- If you don’t see your idea show up in a blog post right away don’t worry! We are expecting and hoping for many ideas from all of you and will sort through and get your idea looked at ASAP. If you can’t wait, then feel free to join our forum and start a topic about your idea. We would love to have your participation and experienced knowledge. The Space Update Forum is also a great place to network with other aerospace technicians in your profession or just to hang out.
- Any ideas you wish to submit should be emailed to the Space Update webmaster.
So think over what it is you want to see covered on Space Update and let us know. We are looking forward to hearing from you and meeting you on the forum.
What makes up a hydraulic system? Well the simplest hydraulic system has only three parts: The pump, cylinder, and the fluid. Pumps can be of any shape or size. Some pumps are hand or foot driven while more complicated ones can be a turbo or another form of gear type pump. Cylinders can also be of any size as long as it is water tight to prevent fluid leakage.
The fluid can be just about anything, though some fluids do work better than others. In theory, you could use your nice cold ice tea you’re drinking on a hot summer day as a hydraulic fluid since all fluids are nearly incompressible, but I don’t think I would try that. I prefer to drink my ice tea after work is done instead of using it for work. Specially made hydraulic oil is usually the preferred fluid due to its slow heating (hydraulic fluids do heat up due to friction as it moves inside a cylinder) properties compared to water. Remember, it takes only 212 degrees to make water boil while hydraulic oils require higher temperatures before it will boil and fail in a hydraulic system. I have no idea what the boiling temperature of ice tea is though.
Looking at the picture below, you can see all three parts. The “pump” is placing 5 lbs. of pressure on a 1/2 inch area “cylinder” causing the “fluid” to do its work lifting a hundred lb. weight. No matter how complicated a hydraulic system can be, it will always have these three main parts.
Other parts can be added to ensure better safety and control. Parts such as:
- Check valves-To ensure a one way flow in a cylinder.
- Reservoirs – tanks that hold large amounts of hydraulic fluid that can’t all be stored in the cylinder.
- Control valves – allows the operator to direct the flow and supply of hydraulic fluid traveling in the hydraulic system. With a control valve, an operator can actually open the lines to allow the fluid to flow freely and not build up pressure therefore allowing the pumps to stay on but in a neutral state. When work is needed, the control valve is engaged to a closed position causing the pressure to build inside the cylinder and allowing work to be done.
- Relief valve – Probably the most important safety feature in a hydraulic system. Pressures can increase quite quickly in a hydraulic system beyond the structural limits of a cylinder and can cause an explosive failure. Relief valves are designed to open and relive the pressure if it exceeds a certain point it is designed for causing the hydraulic fluid to exit the cylinder and return to the reservoir lessening the pressure and preventing failure. Hydraulic leaks and relief valve malfunctions are probably the most common (and possibly dangerous!) failures an aerospace technician will encounter.
Now that you have had a brief overview of hydraulic systems, go to the refrigerator or break room and get yourself some ice tea. I know you have wanted some for a few paragraphs now.
Hehn, A. H. (1993). Fluid Power Handbook Volume 1: System Design, Maintenance, and Troubleshooting. Houston: Gulf Publishing Company.
As an aerospace technician, you will likely find yourself working with or working on various hydraulic systems. “Hydraulics is the science dealing with work performed by liquids in motion…The science of hydraulics is divided into two distinct categories; hydrodynamics and hydrostatics. Hydrodynamics deals with power transmitted by liquids in motion, such as water turning a turbine. Hydrostatics deals with power transmitted by confined liquids under pressure.” (Hehn, 1993) When we refer to “hydraulics” in this post, we are referring to “Hydrostatics” only.
The first known study of hydrostatics was done in the mid to late 1600’s by the French mathematician, Blaise Pascal, who developed a law or principle that stated when pressure was applied or lowered on a confined liquid at any point, that change of pressure was transmitted equally throughout the entire fluid. This is an important principle in hydraulics and explained the large amount of work a hydraulic system could do with very little liquid and minimal pressure.
Due to the fact that liquids are practically incompressible and that any force or pressure applied is equally transmitted in all directions, you could apply a moderate amount of pressure on a small area and that same pressure would be transmitted to a larger area without losing power and doing much more work.
For example, look at the picture above. If you apply 10 lbs. of pressure into the smaller opening that is only 1 square inch, you are applying 10 psi of pressure. On the other side is a hundred pound weight that is sitting over a 10 square inch area will receive that same 10 lbs. psi pressure and the 100 lb. weight will actually be lifted! Each square inch is receiving 10 lbs. of force, but since the larger opening is larger, 10 sq. inches, 10 times the work can be performed.
Pascal’s law can be expressed in F=P*A. P is pressure (psi), F is force (pounds), and A is area (square inches). You can also use a triangle (similar to the ones discussed in previous posts to calculate electrical values) called the Relationship between Force, Pressure, and Area Triangle shown below. Using this triangle, you can calculate any value as long as you know the other two values.
Next time we will discuss the main parts of a hydraulic system and what role each one plays.
Hehn, A. H. (1993). Fluid Power Handbook Volume 1: System Design, Maintenance, and Troubleshooting. Houston: Gulf Publishing Company.
I never understood electrical technicians. Why they liked to play around with something as hazardous as electricity is beyond me. Sometimes I think they were those young toddlers we always hear of sticking the family silverware into the electrical socket just to see how straight up they could make their hair stand. Heck of a way to measure current or voltage, but I guess somebody has got to do it and they feel it has to be them. “Hmm…hair is only standing up about 90% and the convulsions are not as severe as last time…there must be a higher load on the electrical system right now…I bet it’s Mom using the washer to wash my diapers again.”
Thankfully, there has been progress made for people who like to stick pointy metal objects into sockets, probably demanded by their horrified mothers. Electrical technicians eventually gave up the silverware for other unique measuring devices that turned out to be a whole lot safer but a bit more cumbersome. Meters were created that measured many properties of electricity. There were meters for Volts, Current, and Ohms (resistance) that required the technician to carry as many as three heavy analog meters to their jobs. Eventually, someone came up with a meter that could measure all three properties. “The invention of the first multimeter is attributed to British Post Office engineer, Donald Macadie, who became dissatisfied with having to carry many separate instruments required for the maintenance of the telecommunications circuits.”
“Multi” means “multiple” and “meter” means “to measure.” The first multimeters were analog. Some were large machines that were made to sit on an electrical technician’s bench and could do detailed measurements while running off AC power. Others were smaller and used to do troubleshooting in the field. These ones ran on a battery and could be held in your hand. Both types had a needle type gauge that would move and give you the reading you were testing for. Eventually, most multimeters went digital and gave you a numeric value on a screen.
A typical multimeter will have at least four sections:
- Display screen
- Function switch
- Range selector
- Input jacks and test leads
Displays are pretty much self explanatory. It displays the value of what your measuring. If you are measuring volts, the display will show you the volts measured.
The function switch allows you set the multimeter to the property you are measuring. If you wish to measure AC volts, you would move the selector to ACV for example.
The range selector allows you to narrow down the range of what your measuring so you can get a more accurate reading. For example, if you are measuring direct current volts, and you are not sure what range to select, you would first select the maximum value of 1000. If the display reads much lower than 1000, then you can “dial down” the selector to a value just above what the volts are. This way you get a more accurate reading.
And of course, you can’t measure anything without having probes and the input jacks for them. This is where the electrical technicians get to relive their childhood experiences. You plug into the proper input jack (see your owner’s manual for which one) and you get to stick the probe into something electrical. At least your mother is not standing over you freaking out while the house lights dim again.
Seriously, as for any device, read the owner’s manual for further instructions and have a expert teach you about that particular multimeter. And please, resist the urge to stick your silverware into any sockets. Your too old now and your heart just can’t take it anymore!
Nida Series 130E Lab/Text Manual April 2002
Electronics is a major part of some aerospace technician’s workday. As an aerospace technician, it is considered a basic skill to be able to calculate voltage, current (amps), power (watts), and resistance (ohms), but remembering the formulas that go into those calculations can be difficult. This is where a “magic triangle” can help.
The first thing you need to remember is the correct formula sign. What letter or symbol represents each of these values. The table below should help and can be cut out and kept in your badge holder if you want.
|voltage||V or E||volt||V|
To calculate power (watts), voltage, and current you can try to memorize three different formulas depending on which value your looking for or you can use a Power Triangle.
To find the value your looking for, just cover up the formula sign on the triangle and do the calculation you see. Let’s say you have measured the volts and current with your multimeter, you can cover the P up on the triangle with your thumb and see that you need to multiply volts by current to get the wattage (power) that is being passed over the line. Or, say you want to find out the volts and all you can measure is the watts (P) and current (I). You cover up the V on the triangle and discover you need to divide P by I to get the answer. It’s really not that difficult using the Power Triangle and sure beats trying to remember three separate formulas.
To calculate resistance using the Ohms law, there is another magic triangle called the Ohms Law Triangle. This triangle will help you calculate resistance, current (I), and voltage. This can also help you figure out how large of a resistor you want to place in a circut to obtain a specified current and voltage.
To calculate what type of resistor you need to obtain the proper resistance in a circuit, you would cover the R on the triangle and see that you need to divide Volts by Current. If you already have a resistor on the circuit and wish to know the current, you can divide volts by the resistance to get the answer after you cover up the R on the triangle. Not too hard is it?
For more advanced calculations, you might also find this Power Wheel handy.
Overall, power calculations don’t have to keep you up at night or calling your former electronics instructor right in the middle of a job. All it takes is just a couple “magic triangles” to help you through.
Recently, Dr. Al Koller, Principal Investigator of SpaceTEC, appeared on Syndicated News, a web based journalist site. You can listen to the 15 minute interview below.
You can discuss the SpaceTEC interview or any other aerospace subject on our forum.
How many times have we heard out parents bellow out to clean our rooms? Probably far more than we care to count, but cleanliness does not end with childhood. Cleanliness is essential to good health and a safe environment. That not only applies to humans, but to spacecraft as well.
Spacecraft of course range from satellites to planetary probes to manned spacecraft. Each type of spacecraft has its own unique reasons as to why it needs to be kept in a clean environment. Specialized equipment can be contaminated by material that is less than 100 microns big. (A human hair is about 100 microns in width) Also some planetary probes must be microbe free so that the probe will not contaminate another world and possibly endanger life on that planet or give us a false reading of life on that particular planet. If you think trying to bring a plant through customs after visiting a foreign country is a big deal, just try sending a contaminated lander to Mars and making the mistake of announcing to the world that you found life on Mars!
Human spacecraft also require a clean environment. Dust and other contaminates will not just sit idly on the floor as they do on Earth, but float in a micro-gravity environment getting into equipment, the astronaut lungs, eyes, mouth, etc. Depending on the material floating around, it can be an irritant to an astronaut or something that could be life threatening such as breathing in microscopic metal shavings. This is why you always see astronauts wearing goggles and sometimes masks as they open a new module to the International Space Station until they can confirm that the filters have completely cleaned the air of all contaminants.
As an aerospace technician, you may find yourself working in a clean room environment. Some space hardware cannot risk exposure to dust, microbes, or any other contaminant. Humans, no matter how fastidious they are in their hygiene, are the dirtiest objects to enter a clean room. So, since you are a hazard, precautions must be taken.
At the Jet Propulsion Laboratory or JPL, “The default clean room settings are determined by the project with the most stringent cleanliness requirements. Both high bays are class 100,000. This means that in every cubic foot (about 28 liters) of air there must be no more than 100,000 particles at one-half of a micron and no more than 700 particles at five microns or larger. This may sound like many particles, but they are incredibly minute; for example, one strand of human hair measures 100 microns. A typical home or school usually measures in the 200,000-300,000 class.” But it can be even more stringent. During the assembly of the Genesis spacecraft, “engineers and scientists at NASA’s Johnson Space Center in Houston, Texas, built a class ten clean room exclusively for the spacecraft to ensure that no contaminants from Earth accompanied the Genesis spacecraft to its destination in space. That means that a mere ten particles (one micron in size) are present per cubic foot of air per minute.” Genesis used “collector plates” to capture particles from a comet’s tail and return them to Earth. To ensure that only comet particles were being viewed once the collector plates were returned and examined, extraordinary efforts were made to keep the plates and spacecraft as sterile as possible.
So, as an aerospace technician, what precautions would you be required to take? Well first of all, good hygiene is a nice thing to do. (Your co-workers will thank you for that step!) Next would be collecting a “bunny suit” from logistics that is sealed in an air tight bag. This suit will end up covering your head, face, and entire body including your feet ensuring that any particles such as hair or exfoliated skin that falls off your body is contained within the suit.
Your next step would be to stop by a clerk or person that is responsible for keeping track of everyone and everything that enters and exits the clean room. For the Space Shuttle Program, these people are called Orbiter Integrity Clerks or OIC’s. You will bag up all unnecessary items on your person and place them in a bag to be kept by the clerk, sign in all tools and materials you will be taking inside with you to do your job, and of course sign yourself in too. When you exit the clean room, you will go over the list of all the items you took inside with you with the clerk and ensure you brought everything back out. You cannot leave any FOD behind in the clean room.
Once you’re done checking in with the clerk, it’s time to take a shower. Not a water shower, but an air shower. You will enter a doorway, close it behind you, and raise your arms in the air while a blast of air blows over you from several nozzles. This air blast is to knock loose any particles that may be on your clothes and tool bag. The particles are then sucked up into a filter. After the shower ends its cycle, you will exit the other door into the dressing area.
The dressing area will have a “sticky mat” (sometimes there will be sticky mats outside before you enter the air shower) that will cause your shoes to stick to the floor removing any particles that may be on the bottom of your shoes. In the dressing area you will put on your bunny suit and prepare to enter the clean room. Make sure you inspect the bunny suit for any tears or holes. There should be no openings that could possibly allow contaminants to fall out.
While in the cleanroom good work practices become even more important. Did you bring a waste bag that seals to put all your trash in? Are you practicing “clean as you go?” These things are important outside the clean room and much more so inside. You should never leave anything behind that shouldn’t be there.
Now you know how to work in a clean room. Your parents sure will be proud of you.
More information can be found about clean rooms at JPL’s website.
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.
|Exact relationships shown in boldface|
|1 inch (in)||2.54 cm|
|1 foot (ft)||12 in||0.3048 m|
|1 yard (yd)||3 ft||0.9144 m|
|1 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.
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:
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.
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.
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.
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.
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!
“Expert-a person who has special skill or knowledge in some particular field.” – dictionary.reference.com
Leading up to my appearance on The Space Show, I had stopped by the web site to check on upcoming guests. Along with other guests listed, my upcoming interview was listed and the host had titled me as a Space Shuttle expert. I was horrified! Though I had worked on the Space Shuttle fleet as a technician and had a Master’s degree in Aeronautical Science, I was no way an expert in mine or many of my peer’s eyes. Many of my peers at KSC had much more experience and had forgotten more about the shuttle systems than I would ever learn in a lifetime. I immediately wrote an email to the host and asked him to take the word “expert” off the section announcing the upcoming interview.
A week later I was recounting the story to a friend of mine whom I considered an “expert” in academia. After I told the story, he told me that he considered me an “expert” on the Space Shuttle. I protested and reviewed the reasons as to why I couldn’t be an expert. He then countered with this simple argument: “You are the only person I know that has worked on the Space Shuttle fleet and you have taught me much about something I knew little of. In my eyes, you are an “expert.””
I reflected later that evening on what he had said and he was right. In his eyes, and many other people’s eyes, I am an “expert.” And, as an aerospace technician or student in an aerospace technology program, so are you.
How many aerospace technicians do you deal with on a daily basis outside of work? How many people in your life, family, friends, internet, business acquaintances, etc. outside of work are aerospace technicians that have actually worked on space related hardware? Probably very few people. How many people inside your workplace do you encounter that would have no clue as to what you do? That makes you an expert and a teacher to anyone that is a willing student.
During my time at KSC, I sent many personal pictures and emails detailing my day to day activites, for I felt working there was truly an adventure that should be shared. The surprising part was the feedback I got. Instead of people complaining about my numerous emails and pictures, many friends and family (and some others that the emails got forwarded too) wrote back thanking me for teaching them about the Space Shuttle in such a personal way. Much of the information I shared was just common day to day stuff for the aerospace technicians, but for the general public it was all new, interesting, and educational. I would venture to say that probably 99% of the general population in our country and world has no clue as to what you do as an aerospace technician to prepare a spacecraft for its mission or what that mission is. I have had contact and questions from people literally all over the world showing an intense desire to learn more and that in turn pushed me to learn more to be a better teacher and technician.
Even at work, astronauts would approach technicians and ask what they were doing and would become the student learning from that technician. Same goes for some of the upper management and even VIP guests such as senators and ambassadors. During those times, the aerospace technicians are the expert and have a duty, in my humble opinion, to teach and hopefully give that person a positive experience during their visit.
Just getting through the first semester in the aerospace technology program has already made you an “expert” in relation to the general public. The lessons you learn on space history, aerospace culture, safety, etc. is much more than most people get in a lifetime. And, as people in your life find out that you are learning to “work on spaceships”, they will look to you with many questions they have had but never knew where to find the answers. You are now their “expert” and it is a great opportunity to teach someone about space exploration and why it is important to our country and our human race as a whole.
Getting public support for our Human Spaceflight Program doesn’t entail full page ads in the paper or busing in as many people as you can to watch a launch. It does not entail having an astronaut appearing on TV or at a public appearance. It does not entail press releases by NASA. Gaining support and understanding for what we do is done one person, one taxpayer, one politician, one child, etc. at a time and it’s done by you.
You want public support for our HSF? Then it’s up to you to garner it. Teach your family, friends, post a blog, whatever, but make time to teach about what you do. That child you see playing with a toy spacecraft at the store or on the playground, can be overjoyed at their good luck to have you talk with them and their parents for five minutes (show some pictures on your phone of your workplace) about what you do and why you do it. While you may not remember the encounter days later, they will remember it for years to come and will have passed on the news that they met someone from “NASA” who works on rockets to their family and friends and that he took time to speak with them.
When someone sees your Boeing, Lockheed, USA, SpaceX, etc. sticker on your car or on your tee-shirt and ask about it, make time and show them some pictures and talk a little bit about your job. You are the “expert” to them and they may never have an opportunity again in their lifetime to meet someone from a space center. Is five minutes of your time worth it when you will give them a positive memory of space exploration for a lifetime? I hope so. You will find the experience just as rewarding as the person will when you make time to share your “expertise.”
Of the many things I have learned while working as a technician at Kennedy Space Center, the most important and most challenging one is managing your time. A typical shift at KSC is about 8 hours long, but if you take into account the time off for meetings, breaks, answering emails, etc. your actual workday to perform your primary tasks is about 6 hours. That’s not much time to start, work, and complete a job. I thought I would share with the technicians and soon to be technicians what I’ve learned to be successful in getting through my day.
Before doing the job:
- What jobs will you doing that day? Usually your shop lead will give you your assignment for the day and it’s up to you to get off to a good start.
- Read the Work Authorization Document or WAD. What does the job want you to do? What certifications does the job require? Are you certified to do the work? Do you have your cert card with you to prove you are certified?
- What process covers the job? Find the proper process that applies to the job and either set aside the book with your tools or print out the paperwork. Read the process; don’t assume you already know it or have it memorized.
- What paperwork will you need to print out and add to the WAD? Get the paperwork printed out and verify the process version matches the version in your process documents.
- What tools will you need to do the job? After reading the process you should have a pretty good idea what tools you need. Are all the tools in your tool bag already? Do you need to visit Logistics to pick up materials and tools? There is nothing more wasteful of your time than having to stop your job in mid-work to go find a tool, material, or another page of paperwork. Set aside the tools and materials you need for the job beside your process and paperwork.
- Where is your job going to be? Since I worked on the thermal protection system of the shuttle, I needed to know where my tile/blanket/cavity was located on the ship. After all, there are only 24,000 tiles alone on a typical shuttle! Print out a map of the location on the ship for your job and go find it before moving everything there.
- Check out the work area. Is there room for all your tools and other items? Will you have to stage some of the things nearby? If so, you will want to lay out your items in the order you need them to make the flow of the work go smoother.
- Safety. Do you need a harness, goggles, smock, etc.? Are you required to tether your tools and if so, then place tethers on all the tools you’re going to use for this job ahead of time.
- Have a bag handy to place waste material in and set it aside with your tools.
- Will you need a Quality Control Inspector for your job? If so, this would be a good time to put in a call for one. Let the QC see where you’re going to be working and have them go over the WAD and other paperwork with you. A QC is there to help you follow the process, not “ding” you. I at first had a problem with someone looking over my shoulder while I worked, but have learned to value that “second set of eyes.”
- Take all your paperwork, processes, tools, etc. to the worksite or the staging area. Set up your bag to place waste material in. Tape off and cover anything you need to avoid any accidental damage to the ship or hardware you’re working on. If you are working above the floor, then have some sort of catch/drop barrier placed below your work area and the floor to ensure nothing falls on the ship or people below.
Doing the job:
- Be aware of your surroundings while doing the job. Always be mindful of your safety and the safety of others.
- Make sure you have adequate lighting to work in. As my friend Larry Tanner used to always say, “Light is your friend.”
- Clean as you go. Nothing worse than to be standing in a pile of trash and potential FOD while working. Once you produce waste, pick it up and put it in a trash bag. You will find there is less to clean up after the job ends.
- Always refer to your process and WAD.
- Stamp as you go. Stamp the WAD as you complete each task. DO NOT STAMP AHEAD OF YOUR WORK STEPS. That can get you into some big trouble.
After the job is over:
- Go over your paperwork and ensure that everything that was to be stamped has been stamped and dated.
- Clean up your work area.
- Return all tools and unused materials to their proper places.
- Go back to your work site and do a final walk down ensuring that nothing has been left behind.
- Pat yourself on the back for a job well done!
If any other aerospace technicians would like to add to these suggestions, please feel free to do so in the comments section.
Last night Gregory N. Cecil, M.A.S., a 2003 alumni of the SpaceTec program (the Gemini Class) appeared on The Space Show hosted by Dr. David Livingston. The interview went so well that it went a half hour over the scheduled time. There were many good calls and email questions from all over the world and Kennedy Space Center.
You can download to the interview or listen online at the following link:
http://archived.thespaceshow.com/shows/1452-BWB-2010-11-03.mp3 This is the direct URL to the interview.
You can also subscribe to The Space Show podcast on iTunes and download this interview and many other worthwhile interviews to listen too.
A while back I was a guest speaker at an aerospace technician class. This was the first semester for the class in a two year program. I asked the students where they planned on working after graduation and to the man/woman, they all said “the Space Shuttle program” at Kennedy Space Center. I pointed out the program would be over by the time they graduated in two years and a look of surprise and dismay crossed their faces. I then asked if they were aware of and could name other space ports in these United States of America and they indicated they were not aware of any others. I proceeded to teach them about the other space ports and to explain that the skills they were learning will be needed there also.
Kennedy Space Center gets all the publicity because of Human Space Flight, but there are currently nine space ports in use and 3 proposed ones. The nearest space port is just right across Mosquito Lagoon from KSC at Cape Canaveral Air Force Station (CCAFS). The primary companies that launch there are United Launch Alliance and SpaceX. (SpaceX also has a launch facility at the Marshall Islands in the Pacific Ocean.) Many unmanned NASA probes, government, and commercial satellites are launched from this facility at multiple launch pads. Also Pegasus launches are conducted from there. CCAFS has been launching rockets since the 1950’s.
Further up the east coast is NASA’s Wallops Flight Facility at Goddard Space Flight Center. Wallops is responsible for launching sub-orbital and small orbital launches along with testing and research. Wallops has been in business launching these smaller rockets since 1945.
Just next door to Wallops is the Mid-Atlantic Regional Spaceport (MARS). MARS launches both commercial and government payloads. MARS has been launching rockets since 2006.
Moving out west, there is the Nevada Test and Training Range responsible for launching sounding rockets and test vehicles. It was formally known as Nellis Air Force Base and is also home to Area 51. They have been launching since the 1950’s along with many other activities.
The next launch facility is in New Mexico called Spaceport America. It’s most famous resident is Virgin Galactic which will be launching tourists into sub-orbital flight within the next year. Spaceport America also does sub-orbital commercial launches. Spaceport America has been an operating spaceport since 2006.
California has three spaceports, including one that is mobile. First is the Vandenberg Air Force Base which specializes in ballistic missile tests, along with the typical government and commercial satellite payloads. Vandenberg has been launching rockets since the 1950’s.
The second California spaceport is the privately owned Mojave Air & Space Port. This facility is famous for the two historic launches of Space Ship One. Mojave Air & Space Port has been operating since 2004.
The third California space port is Ocean Odyssey Complex owned and operated by Sea Launch. Ocean Odyssey Complex is a converted oil rig with associated support ships whose home port is in Long Beach California but does the actual launches at the equator in the Pacific Ocean. Ocean Odyssey Complex has been doing commercial launches since 1999.
If you don’t mind the cold, there is the Kodiak Launch Complex in Alaska. Kodiak is operated by the Alaska Aerospace Development Corporation and specializes in satellite and ballistic missile interceptor launches. They have been in operation since 1998.
There are also numerous spaceports throughout the world if you feel like working outside of the country. You can find a list of these spaceports along with the appropriate links here.
The point is, though Shuttle work at KSC (though some other work there continues) is coming to a standstill, there is still lots of work at CCAFS (for example SpaceX and ULA) and other spaceports throughout the country and the world for certified aerospace technicians both in government and private companies. Don’t limit your talents and skills to just one spaceport. Think outside of the box and the area when it comes to pursuing the career you have chosen.