Dilemmas Of Engineers Faced With Defective Design

Engineers toil hard to create products and processes for the benefits of the human race. They also improve the convenience in our everyday living and beautify our environment. They are the people who turn technological fantasies into reality.

However, while engineers may strive to reduce the hazards brought about by the application of new technologies, they are not always successful. Very often, it is not the technological barriers that they cannot overcome, but rather the obstacles placed by fellow human beings.

Major engineering projects in aeronautical and aerospace applications are normally very costly and time sensitive. Correcting a design defect can be very costly and time consuming. Economic cost consideration may not always permit major redesigning to be performed. In order to better appreciate the dilemmas faced by engineers when they are faced with design faults, we shall discuss two well-known cases. The first case is involving the Challenger Space Shuttle and the second case involves the DC-10 Jumbo Jet.

The Challenger Space Shuttle Case

For a better appreciate this case, some of the background information will be useful.

The main vehicle in the space shuttle is the orbiter. There are three rocket engines in the orbiter, which also contains a huge cargo bay for the space lab or for satellite that will be launched from the space shuttle. Most of the liquid hydrogen fuel needed by the rocket engines is stored in a huge external tank (which also carries oxygen to support fast combustion). The external storage tank is jettisoned after about eight and a half minutes from lift-off when the fuel is used up.

The rockets in the orbiter cannot provide sufficient power to send the shuttle into space because of the huge weight. The additional thrust during lift-off is provided by two external solid rocket boosters. Since the booster rockets are huge and long, they are manufactured in segments and the 5 segments are joined together at the launch site. These joints are called field joints since they are put together at the launch site.

The field joints are not as sturdy as those performed in the factory and the sealing is also not as reliable. The lower performance of these field joints was apparent from the various tests. Of particular was the concern that the sealing at the joint to prevent the hot rocket air from leaking at low temperature. However, the redesigning process was slow and no new design was available.

On the night before the Challenger space shuttle was to be launched on Jan 28, 1986, Morton-Thiokol, the maker of the solid rockets boosters, were worried that the solid rocket boosters might cause problem due to the cold weather. They held a teleconference with NASA managers to present their concerns and recommended that the launch be postponed till the temperature rose to a more suitable level.

The NASA managers rejected the recommendation as they believed the solid rocket boosters would be able to perform well, even at the expected low temperature of 26 degree Fahrenheit as their design called for performance at as low as 31 degree Fahrenheit. Under the pressure from NASA manager, Morton-Thiokol managers changed their recommendation to proceeding with the launch, despite the strong protests from their engineers who could not prove conclusive that the filed joints were indeed faulty.

The DC-10 Jumbo Jet Case

In 1974, the first fully loaded DC-10 jumbo jet exploded over the suburbs of Paris, killing 346 people, a record at that time for a single-plane crash. This was said to be an accident waiting to happen because it was known to the designers that the design of the plane was defective because the cargo door could burst open during flight.

The fuselage of the DC-10 jumbo subcontracted to Convair by McDonnell Douglas. Dan Applegate worked as a senior engineer in Convair directing the project. Dan wrote a memo to the vice president of Convair identifying the various dangers that could arise from the design of the fuselage. He highlighted a few potential dangers, especially with regards to the possibility of disaster due to the failure of the cargo door. He detailed how the cargo doors could burst open during flight resulting in the decompression of the cargo space, leading to the collapse the floor of the passenger cabin above. When that happens, the control lines running along the cabin floor would be damaged and the plane could not be controlled.

The senior engineer therefore recommended that the doors be designed and at the same time strengthen the cabin floor. He warned that such making the changes as he recommended would lead to some of the DC-10 cargo doors being forced open during flight and plane crash would result.

While the top management at Convair did not disagree with technical analysis or warning by Applegate, they maintained that Convair might face possible financial liabilities if they were to pass on this information to McDonnell Douglas. These liabilities could be severe since the cost of redesign and the delay to make the necessary safety improvements would be very high and would occur at a time when McDonnell Douglas would be placed at a competitive disadvantage.

Observations:
There are close parallels between the two cases. Both designs were known to be flawed by the engineers who tried to alert the management but the management decisions were clouded by monetary considerations which led to the eventual loss of the crafts and the lives of the occupants. In both cases, engineering hats were removed and management hats put on.

The Role of Private Enterprise in Putting Man into Space

Has NASA, the monolithic space agency, failed in it's quest to put man out into the cosmos? Will profit coupled with man's need to explore be the driving engine which sends man into the cosmos? Think about what has moved technology forward within the American society over the past 100 years or so. Was Orville and Wilbur Wright employed by the government. Of course not. Most of their research and development for the invention of the airplane took place within a small bike shop in western Dayton, Ohio, the birth place of aviation. Thomas Edison, who is accredited with 1,093 patents earning him the nickname "The Wizard of Menlo Park" used his own money to build the Menlo Park research labs in New Jersey. In 1889, Thomas Edison established the Edison General Electric Company. Thomas Edison is considered the most prolific inventor of our time and his inventions were created within the realm of private enterprise.

Did the seed for the invention of the personal computer germinate within a government lab? The invention of the personal computer came from an assortment of various inventions and from the tinkering of Steve Jobs and Steve Wozniak in Job's garage in an area now called Silicon Valley, the southern part of the San Francisco Bay Area in northern California. Their tinkering led to the development of Apple Computers. The story of Bill Gates and the development of the Microsoft family of operating systems took place within private enterprise. The Windows family of operating systems is the most widely used on earth and has been a major player in bringing information technology to the developed world.

Examples of major technological advancement within the realm of private enterprise are numerous. Most major technological advancements within society have occurred outside the purview of government intervention. Governments were intended to govern the people. The government's role is to preserve the environment of freedom and democracy so that intellectual curiosity can flourish within this environment. The government's role is also to provide funding, and should not be in the nuts and bolts operation of putting man into space. The ingenuity of man within the realm of private enterprise has resulted in most of the technological advancements we enjoy today.

The cosmos will be explored by man operating from the base of private enterprise and the technology needed to explore the cosmos will be developed within that enterprise. Why is this so? NASA is an agency driven by fear of tragedy. More mishaps will decrease the probability of sufficient government funding. This cycle of fear, mishaps, and the hope for continual funding is one that seems to have no end. But mishaps are part of the business of putting explorers into space. What can better withstand the expected mishaps. A government agency or private enterprise. If a private enterprise fails, it's competitor can step in to fill the gap and the engine of private enterprise can continue to push man into space. NASA is not a private enterprise competing within the world market place.

NASA is not what it used to be during the Apollo days. Given it's current mind set and culture, it will be difficult within this framework to send man out into the cosmos as true explorers. They have given the nuts and bolts of putting man into space to private contractors. But these NASA contractors have the same NASA mind set because they are under the dominion of NASA. There is a fear of mishaps within contractors without true competition within the market place. NASA awards contracts to the lowest bidder. Does the lowest bidder provide the highest level of safety. Once a company is awarded a contract, they remain a NASA contractor for many years and simply become an extension of NASA. Therefore NASA becomes a autocratic agency with it's arms extending outward to many companies. NASA's manned space flight program can do no more then low earth orbit. Year after year of low earth orbit does not excite the American people. Astronauts today are no longer household names. An American president here and there will give a speech saying we are going to Mars. Even President Bush's January 14, 2004 speech seems to have already been forgotten by the American public.

When we went to the moon this was the start of an exploration. A goal was set on May 25, 1961 by President John F. Kennedy, during a speech before a Joint Session of Congress, to reach the moon before the end of the decade. NASA kicked into high gear and achieved one of the greatest accomplishments in the history of mankind. We took the first step into space and then just stopped. Since then all of the manned space missions have never gone beyond low earth orbit, and the American public becomes bored easily. To gain the American interest and support of the Apollo days, we must send true explorers out into space. NASA wants to take such small, time consuming incremental steps that by the time comes when the really exciting work begins, the American support and interest may be eroded to the point where NASA may no longer have the financial means by which to accomplish such an endeavor. Hence, the need for private enterprise to accomplish such an endeavor. If we are going to go into the cosmos, then lets do it and stop the futile activity.

A private enterprise is not a bureaucracy. If safety issues arise from qualified personnel within a bureaucracy, these issues may not resonate to the proper people within the organization. A case in point, the knowledge of a strong potential for a O-ring failure at low temperatures between the segments for the solid rocket boosters of the space shuttle, existed within the bureaucracy of NASA before the Space Shuttle Challenger explosion. More specifically, this critical information in terms of probability of O-ring compromise was expressed by engineers at Morton Thiokol, the contractor for the development and production of the solid rocket boosters. This information never percolated upward from Morton Thiokol to the proper people within the NASA organization.

In private enterprise, which is non-bureaucratic by nature, a relatively small group of people are working toward a common goal. In this situation, safety issues which arise will be known by all members of the organization. Safety issues will not get lost in a bureaucracy. NASA depends on it's contractors to deliver a high level of safety. A private enterprise depends on itself to provide a high level of safety. The structure of a private enterprise is more suited to the endeavor of sending out explorers into space. The government should award grants to the most promising companies with the understanding that the sending out of explorers into space does indeed benefit mankind.

Americans are at their best when they compete. Competition is an integral component of American society. What was the driving force that put us on the moon. It was the competition with the Russians. At the present moment in time, this type of competition does not exist. Although, it appears as if China may be a future competitor. Americans need to compete to accomplish something. It is competition which drives the advancement of technology. Why not let companies compete for government funding and let the research and development occur within these companies, and most importantly let them compete. These companies can have the same characteristics of any company that wants to produce a viable product. They will not be under contract from NASA and will operate as a separate private enterprise entity. A company can make money from space tourism and the same company can be involved in sending explorers out into space. Government grants can be awarded based on how strong the potential exists for space exploration. A company can be involved in space tourism, exploration, or can provide a research and development platform. This is the future of man's endeavor into space.

Man will be exploring the cosmos with private enterprise being the driving engine. If one enterprise fails, one of the competing enterprises will win out. Sure there will be some disasters and risks will be taken because that is the nature of the business. But when unfortunate disasters or mishaps do occur, the private enterprise engine will not grind to a complete halt. Burt Rutan and his Scaled Composites team have taken the first steps toward this archetypical dream of exploring the cosmos, and they did it with a fraction of the budget that NASA uses and with a team of 130 or so people to boot. They won the Ansari X-Prize by sending a man into space and returning him safely to earth and then they repeated this within two weeks. An absolutely unbelievable accomplishment given the facilities and resources which were available to them. This could only occur within a society where freedom and democracy are regarded as a right to all individuals. The United States is such a society.

Burt Rutan has said that he has never worked a day in his life. He only plays. His passion for his work is what produces results. Burt Rutan and his team represent the core of what makes the United States the greatest country in the world. May be terrorist can get it through their thick heads that freedom does work. Most importantly, Scaled Composites has shown the world what private enterprise can accomplish. Even if Scaled Composite's endeavors never go beyond earth orbit, they have taken the first step within the proper mind set and culture, and this is what will put man into the cosmos. This mind set and culture of pure unadulterated intellectual curiosity is what really will put man into the cosmos. Not NASA's mind set of fear.

NASA has played it's important role by lighting the torch in sending man to the moon. We are now at a point in the history of mankind where that torch should be passed to private enterprise. The developer of the Ansari X-Prize I'm sure shares my thoughts. God has placed the planets and all the stars within the universe there for a reason. It is God's intention for us to move outward into the final frontier. We do this to fulfill the natural curiosity that God has given to us and in the process we better the lot of mankind. Lets go...

Science - The Space Shuttle Design Concept - Idealized Functionality!

Stripped to the essentials, NASA's Space Transportation System (STS), the Space Shuttle, needed an Orbiter vehicle to accommodate crew and mission requirements, plus the propulsive power to accelerate many millions of pounds of personnel, hardware and fuel to orbiting velocity; plus all back-up, contingency and emergency equipment that could conceivably be necessary for foreseeable and unforeseeable exigencies. Among the forcing-functional-considerations (after the primary concern for safety and reliability) was cost and the minimization of factors which would necessitate long preparation periods between flights (the "shuttle" concept).

The Orbiter vehicle would house the astronauts as they circled Earth, containing also all requisite systems, materials, supplies and equipment for: life support during the voyage; communication with Earth; mission objectives (space experiments to be carried out); and requirements for the return to Earth: mechanisms for de-celeration from orbital speed, critical insulation or heat protection for the reentry phase, and means for flight control and landing upon a standard length runway (glider modus operandi, no propulsive power), and conventional control surfaces: wing flaps, rudder flaps, wheels and brakes.

The propulsive system evolved into a three engine configuration (providing increased reliability and stability), integrated into the Orbiter vehicle structure; engine fuel contained in a large central tank attached to the Orbiter (droppable when empty, with altitude-opening parachutes) and two strap-on solid rocket boosters (reliable gigantic "fire-crackers), droppable and recoverable from the ocean (similar parachutes). The propulsion system requirement was extremely demanding, to achieve lift-off and acceleration to reach orbit velocity, lifting over seven million pounds of total weight.

The most reliable and efficient configuration for assembly of the elements and for optimum launch sequence was quickly determined to be the two giant solid rockets bolted to the launch pad (huge explosive bolts anchoring the rocket flanges to the concrete pad); the Orbiter vehicle attached (removably) to the rockets; finally the gigantic fuel tank (removably) attached to the Orbiter. The launch sequence was initiated by firing of the on-board engines, then the firings of the solid rockets and their flange bolts exploded - separating the STS assembly from Earth. The Space Shuttle system would then rise, slowly at first and vertically, increasing in speed and altitude until clear of the Cape Canaveral launch facility, then adjusting to an angled horizontal climb; taking advantage of the direction of Earth's rotation (reducing the STS requirement to reach orbit speed) by about 1000 miles per hour. As the solid rocket boosters complete their firing, they are dropped, to be salvaged from the ocean for reuse. The orbiter engines continue to power the system until orbit is reached and the fuel tank is depleted, when it also is blasted free of the orbiter.

What is generally not known is that once the Shuttle drops its fuel tank, the orbiting vehicle no longer has propulsive capability - coasting along at 18,000 miles per hour in the vacuum of space. The mechanisms aboard the vehicle for maneuvering are the Space Shuttle Orbital Maneuvering System (OMS), a system of rocket engines used for final orbit injection, modification or maneuvering at the Space Station. The OMS consists of two protrusions at the back of the Shuttle, on either side of the vertical stabilizer. Each contains a hypergolic engine with 6,000 lb thrust and a specific impulse of 313 seconds. The OMS pods also contain the rear set of small reaction control system engines.

For the initial ventures into space, the Mercury and Apollo programs, the reentry approach was for "over-kill" - to protect the astronauts from the extreme heat of reentry by covering the bottom of the circular capsule (the face to reentry) with many inches of ablatable material, fiber-glass and resin, which melts and vaporizes, the transformation from a solid to a gas dissipating the enormous heat of reentry, protecting the astronauts. As the slowing capsule falls to a low altitude, a trio of parachutes is deployed - the capsule drops into the ocean, with a quick pick-up by naval vessels on close standby.

Plasma Engines - How The Workings Of The Everyday Fluorescent Light Gets Us To Other Planets

Everyone has seen a fluorescent tube light, the kind that are used in your kitchen or office and are more energy-efficient than the standard filament light bulbs.

The light itself uses a number of electrical processes that are similar to those used to generate thrust from a plasma engine in space, yet few of us would make the connection between the two. A way to look at it is this: the process that lights a lot of public and private spaces is almost identical to the process that can propel a spacecraft towards another planet or in the case of the NASA probe, Deep Space 1, can propel a craft to speeds never achieved previously in space travel. Plasma engines are viewed as next-generation technologies, with large-scale thrusters currently being developed for possible use on interplanetary missions; however ion thrusters, a class of plasma engines, are currently being used on missions to provide station-keeping duties or as the primary propulsion for spacecraft.

In other words: the age of plasma engines is already here!

What are the similarities between a fluorescent light and a typical plasma engine?

The biggest similarity is that both devices turn the gas that they contain into a conductor, so that current flows through it, and then use this to produce either light or a source of charged particles.

In a fluorescent light, the electrical circuit and the internal filaments turn the inert gas (usually Argon) into a plasma, which in turn heats mercury inside the tube so that it becomes a gas.
Once the mercury has become a gas it is excited by the moving electrons and emits light.
This light is mostly in the ultra-violet range and so is absorbed by a phosphor coating on the inside surface of the tube, which re-emits light in the visible range.

The light needs the plasma so that the mercury is evaporated; heating the mercury on its own would take more time and more power.

The fluorescent light can therefore stay cooler by creating the plasma than it can by just heating a filament on its own as in the case of the standard filament bulb, or by having to heat the mercury. In addition, it can run using less relative power than a standard bulb, which is why fluorescent bulbs are often used to provide bright light in larger rooms and spaces.

A typical plasma engine creates a plasma using a similar process. Electrons are introduced into a flowing inert gas, either Argon or Xenon, under the influence of either an electric field; both an electric and a magnetic field; or an electromagnetic wave in the radio or microwave frequency range. This produces the plasma, the quality of which is determined by lots of factors such as dimensions of the plasma chamber, amount of gas flow and applied power.

Once a plasma is created ions are extracted using electrical fields, often using grids or orifices that have been designed to produce an optimal ion beam for operation periods of more than 10,000 hours. Plasma creation and ion extraction occur concurrently with the ions being made neutral once they leave, by emitting electrons into the beam.

A plasma engine can only run efficiently by generating a source of ions in this way. Some other types of electric propulsion heat gas to increase its exhaust speed, hence increasing thrust, but they do not reach the same power efficiency or "specific impulse" that plasma engines can achieve using ions.

Plasma engines, then, are only suitable candidates for space missions because they utilise plasma for thrust.

Specific impulse, or the thrust per kilo weight (on Earth) of propellant over a time period of 1 second, is a quantity used frequently in space missions. Essentially, it relates to how much thrust can be produced by a device relative to the total mass of the fuel that can be carried on board a spacecraft.

High specific impulses are much preferred to lower specific impulses, as at times the cost of having more fuel for the mission can be the cost of having to upgrade to a bigger rocket.

You can see how both devices rely heavily on plasma in their design and that both types of device can be much more energy-efficient and useful only because they contain plasma.
Yet when you hear about plasma, plasma engines or plasma thrusters, the mind turns more to science fiction than to the light above your head in the kitchen.

Though it is true that only a handful of plasma engines are operational today compared to the ubiquity of fluorescent lights, the next time you look at that light in your kitchen or in your office, take a moment to reflect on how the glow that you can see is founded on the same process that is used to propel spacecraft to other planets.

If you need a fresh perspective consider this: the European Space Agency / Japanese Space Agency mission to the planet Mercury, called "BepiColombo", is using T6 ion thrusters, provided by QinetiQ, on its transfer module to get to the planet rather than using more conventional chemical thrusters. These ion thrusters use an internal circuit, that is different but not unrelated to the filaments in the fluorescent tube, where electrons are introduced into the gas to produce ions.

Engineering Business - Office Location Can Keep Your Expenses Low

Have you reviewed the company's budget recently? Does it need to be reevaluated? Has the staff stayed within the budget or are they over budget? What are you doing to get back in budget? These are all questions that need to be answered regularly to ensure a profit at the end of the day. If you have revenues then you want to keep as much of it as possible.

The purpose of the budget is to control the expenses and to make sure that they do not exceed the revenues. As long as the company has a greater quantity of incoming cash versus outgoing there is positive cash flow. Many of the businesses in the professional service industry that go out of business have a profit on the books, but have a negative cash flow. This is because invoices in account receivables show as earned income, but that does very little good until the payments are received. You need incoming cash to pay the bills and the salaries.

There are several financial strategies that can be implement that will keep your expenses in check. In Part 1, we covered 4 key strategies your engineering company can utilize to trim costs without touching your core business.

Key 1: Recording Your Expenses
Key 2: Using the Internet over the Postal Service
Key 3: Making use of Telecommuting
Key 4: Negotiate better Lease Terms and Rates

In this article we are addressing one more key financial strategy for reducing expenses; the location of the business. The location of the business is important for the flexibility of the business to adjust to the expansion and contraction of the workload. The more flexible the more likely the business can make adjustment depending on the economic conditions.

Key 5: Office Location - Depending on the size of your business certain locations are more suited. Trying to operate a business with gross annual revenue of $300,000 from a 4,000 square foot building may not be appropriate. There are many different locations to operate an engineering business; home-office, virtual office, executive suites, professional office space, or an office building. Each has their advantages and disadvantages.

Home-Office - If you company is very small and you are able to obtain a business license for a home office, it can be a very good way to keep your expenses low. Obviously there are no leasing expenses and the space used is usually tax deductible. Check with your city or government agency to make sure they will allow a business in your home. You will need to obtain a business license in order to render any professional services. In most cases professional services entrepreneurs can obtain a license to operate out of their home, since clients will not be at the office or large delivers of supplies will not be showing-up at the front door every day and disrupting the neighborhood.

But the question always arises when someone should leave the home office and open a business in a commercial building. This really depends on the revenues one is able to generate and whether one has outgrown their available space. The best answer is probably to stay in your home as long as possible to keep the over-head expdnses as low as possible. Initially, a professional license alone may be sufficient to grow the client list and establish enough revenue to operate the business. The disadvantage to the home office is that clients when visiting your office will not consider it as a real business, and may question the credibility of the firm.

Virtual Offices - These companies literally lease a space on the wall. The physical presence of the company is actually somewhere else. The basic package is nothing more than an address, a place to hang the business license, and mail service. Usually the business that lease virtual offices also offer additional services to the basic package such as phone service, fax service, community office, community conference rooms, and so on. This type of service is meant to be for a short period of time, but in some cases can be a more permanent situation. Leases are usually month to month. Again, the disadvantage to a virtual office is that clients when visiting your office may not believe that your community office or conference room is a real business, and may question the credibility of the firm.

Executive Suites - A business that leases out individual offices with common uses such as rest rooms, break areas, lounges, conference rooms, spare office, mail service, parking, custodial service, secretarial staff, and phone answering service. In addition, the lease may also include the utility bills and phone book ad service. There are some major advantages to executive suites. First, you have a real commercial address, which adds credibility to the company. Clients can meet you in your office or in a conference room. Most lease agreements are for a fairly short period of time usually one to three months, which has an advantage if the business does not do well and you need to move or terminate the lease. Disadvantage executive suite leases are higher than a traditional office space, usually two to three times per square foot. When it comes time to expand your business to include additional office space for new staff, the executive suite option may not be attractive any longer. Also if you move the business to another executive suite complex or an office space, you may loss your company phone and fax numbers. To overcome this scenario try to find a building that has both executive suites and traditional offices for lease. Then when it comes time to expand you can move the business to a different location in the building and possibly maintain the address, and phone and fax numbers.

Professional Office Space - If your company significantly grows to a size were the executive suite services are no longer economical, then it may be time for leasing a portion or all of an office building. The lease per square foot are usually low, put all of the services the executive suites provides, including the utilities, your company will now have to obtain. The leases for office buildings are also much longer; usually three years or longer. Make sure that the client base is sufficient and the market conditions are right to maintain a lease that long. The disadvantages to a professional office space is that if business drastically slows down, the property managers may not be willing to renegotiate the lease and will hold you responsible for the full term of the lease. To avoid this scenario try to lease the facilities with a clause that will let you sub-lease the property. The ability to lease a portion of your office space if the need arises may save your company.

Professional Office Building - For a large firm can either lease or purchase a professional office building. Owning the building maybe a better option than leasing. During a recession commercial buildings are sometimes priced well below the cost to build a building. Obviously the business is responsible for the mortgage, but the company can lease unused portions of the building to create additional revenues. If the market is performing poorly and the engineering company is unable to attract sufficient amount of new contracts it can lease a greater portion or all of the building. There are disadvantages to owning an office building such as a possible mortgage, property taxes, insurance, but there are plenty of advantages.

Science - Space Shuttle, NASA's Gamble on Safe Re-Entry at 3000 F (30,000 Tiles, $10K Each!)

Whereas the concept for shielding astronauts and their space vehicles from the extremes of reentry heat for the first vehicles in space, Mercury and Apollo, was "overkill" assurance, an excess of ablatable fiberglass and resin to insure safety - for the envisaged Space Transportation System, the designation "Space Shuttle" described the objective - a quick turnaround, with minimum refurbishment of primary subsystems. To insulate the Orbiter from the searing heat of reentry, the idealized solution is a "vacuum", which blocks all heat transference. The vacuum would be encased in a thin glass-wall box-like container - internal stabilization support of the thin, flat glass surfaces would be by quartz filaments (non-thermally conductive and light in weight) "scrunched" into the glass "box", which would then be vacuumized and sealed. Idealizing again, this "package" (tile - containing all functioning elements to achieve optimized thermal insulation) would be as thin as practical (and small in horizontal dimensions). This would accommodate Orbiter surface curvatures - necessary to achieve an overall aerodynamic shape so as to "fly" during the landing phase of a mission. Finally, the tile would be bonded (the cool - insulated bottom) to the vehicle's basic aluminum structure.

To achieve the insulation properties desired, vacuum processing would be essential (actually, a double vacuum became part of the production manufacturing process, developed by NASA and Lockheed Corporation). As every aspect theoretically feasible, the challenge was the smallest practical tile size that was producible in volume. The standard black (high-temperature-exposure) tile is extremely light, six by six inches in size and about an inch and three-quarters in height. The tiles are bonded to the Orbiter structure by standard RTV (Room Temperature Vulcanizing) adhesive.

Square and close-fitting to eliminate even narrow gaps between tiles, thus to preclude pockets of heated air, quartz-fabric "gap-fillers" are stuffed between tiles - a painstakingly tedious job. There are 30,000 black tiles (seen in all photos of a Space Shuttle). The end result was clearly worth the effort - including the monumental cost. The TPS tile system has proved its reliability, taming reentry heat (temperatures of from 2200 to 3000 degrees Fahrenheit).

The reentry heat develops from the compression of atmospheric gas caused by the Orbiter's speed, as it descends from the vacuum of outer space - it is not the result of friction. As the Orbiter speeds down (18,000 mph) into Earth's atmosphere, air molecules are impacted by the Orbiter, causing tiny pulses of heat and drag; this causes wing leading-edge temperatures to rise to from 2200°F to 3000°F (depending upon reentry angle) - during approximately a six minute speed-altitude transition period, and gradually slows the Orbiter down, eventually reaching ground level and landing speeds of a typical aircraft.

The TPS system made the Space Shuttle program possible.

The voice over the loudspeaker was concluding, "So congratulations to all of us on the Shuttle team, STS-2 appears to have been a great success, and - ", Another voice abruptly cut in, "Rockwell Space, Will Mr. (my name) please call Moser (my NASA counterpart) at the Cape."

At mention of my name, I rose from the conference table, looking at my boss, Chief Engineer, and his boss, president of Rockwell Space Division. The president signaled me, then pointed to the door to his office, which was open, his secretary standing in the doorway. She nodded to me and pointed to a phone. I made the call, the operator at the Cape was waiting, and promptly connected me. Our greetings were terse - Moser spoke for about five minutes, I asked a few questions. Then he said, "Cris Kraft is at Edwards, he wants you to drive up now, maybe we can get a head-start on what happened before they ferry Columbia back to the Cape." I said I'd be up at Edwards (Air Force Base) in about two hours.

Back in the conference room, I summarized the call, "Some tile damage was noted on the walk-around-inspection after landing. No indication of a TPS malfunction during reentry, but the tile damage looks unusual - Dr. Kraft (Director, Johnson Space Center at Houston) is up there - they want me to drive up now." The Chief Engineer nodded. "My secretary will call your wife."

I drove automatically, knowing well the freeway route - my mind reviewing what I'd been told. NASA had taken pictures of the damaged tiles on the walk-around - NASA wanted a knowledgeable "eyeball" look before the ferry flight home. The damage looked like chunks of the tile's insides, an inch or two, was missing. And all such damaged tiles seemed to be along the left wing leading edge, at varying distances apart. There was also other typical tile damage, the pits and break-throughs of the thin black glass, as after the STS-1 flight - undoubtedly due to stray bits of gravel, churned up from the concrete launch pad (despite careful vacuuming before each flight). The number of damaged tiles was apparently not too worrisome - however, anything untoward about tiles (Thermal Protective System) had to be thoroughly understood. The cost of the TPS was almost unbelievable, but their function, protecting against fiery reentry, as well as their compactness, permitting the Orbiter to function like an airplane - was what made viable the potential of the Space Shuttle program.

As I drove, I thought of Dr. Chris Kraft and the near-disaster of Apollo 13. His was the voice of calm authority that had buoyed up America and the desperate astronauts aboard, during the hectic days when no-one knew whether the damaged capsule could be "jerry-rigged" for a safe return to Earth. There was a degree of satisfaction in his asking for me - but then NASA had given me the chore of presenting the TPS briefings at all NASA Flight Readiness Reviews for two years. As Assistant Chief Engineer, my responsibility was the Orbiter vehicle structure, everything but the engines and electronic systems: Design, Stress, Aero, Thermo, Dynamics, Weights, and Materials and Processes, which included the tiles.

I turned into Edwards Air Force Base, parked my car, then saw a jeep speeding towards me. The driver was an engineer I recognized, and a security guard. I climbed in and we took off. The Orbiter was where it had landed, roped off, with a half-dozen security people standing guard. I got out of the jeep and walked quickly to it. The sun was bright and I quickly saw what had been described, the line of damaged tiles - six by six inches of pure white, the compressed quartz fibers looking like Styrofoam - in the midst of solid arrays of black tiles.

"So, what do you think?" The voice was familiar. I turned and said, "Hi, Dr. Kraft" We shook hands.

"Never saw anything like it," I said, "nothing like it in all our tests - it's as if a chunk of the quartz filaments broke away from the inside." The engineer handed me a set of photos of the damaged tiles. Together we walked along the wing, then ducked under the ropes to look beneath the wing-fuselage - an almost flat, huge expanse of solid black, not a single damaged tile. As we walked around the vehicle seeing whatever else looked unusual, Dr. Kraft said, "We've got to make an official report to the Administrator, Congress and the press, but I want an engineering analysis first. Send us a top tile engineer to be at the Cape day after tomorrow - we'll get a NASA man also, then, plus you and Moser, I want an internal layout of possible causes in a week."

That's what happened. The investigation became a "detective" scenario, puzzling out clues, conjecturing what could have happened, verification by test. A key factor was the photos of the Shuttle on the launch pad with its adjacent work platform - the night before launch, as a rainstorm drenched platform and Shuttle.

A week later, a briefing was given to the NASA Base Directors and Administrator:

• The rainstorm was from a direction which caused a platform on the work-assembly structure to spill overflowing rain-water onto the left wing - Columbia standing vertically in the launch mode. Rainwater, therefore, would have run along the leading edge of the left wing.
• Occasionally hairline cracks were known to develop through the thin glass outer (black) coating of the tiles: either during manufacture; during the bonding process of attaching each tile to the airframe structure; when stuffing "gap-fillers"; or possibly even during the prior STS-1 flight (close packing of tiles causing occasional excess pressure on the thin glass walls during the vibration of landing).
• If, therefore, some of the running rainwater encountered a tile with a hairline crack - during the rainy night, some water therefore entered the tile.
• During the flight mission, the left wing was pointed to deep outer space for many hours, the temperatures of the wing tiles therefore dropping to extremely low values, approaching absolute zero. Water in a tile would therefore hard-freeze into ice, becoming a clump of filamentary quartz - as the ice formed from liquid water, the volumetric expansion would cause internal pressure to be exerted upon the encasing of thin glass.
• The ice-filamentary clump could therefore crack the glass casing and be ejected from the tile - occurring during one of the following events: upon freezing due to the significant volumetric expansion from fluid to ice; during reentry, when the ice began to melt, becoming a gas, the drastic volume increase bursting the glass casing; when the vehicle went through the sonic boom, the surface jolt of air pressure causing any remaining chunk of solidified filaments to be ejected from the top of the tile; or when the vehicle landed, the vibration shaking any remaining ice-quartz chunks loose.
• Conclusion: this unusual set of circumstances caused unique damage to a small number of tiles - however, the "thermal protection" function was not compromised, in fact the continued functionality of the damaged tiles adds confidence to the reliability of the overall STS program.
• Recommendation: when rain precedes a launch, a tarpaulin should be used to protect the tiles.

Aaron Kolom qualifies as a "rocket scientist" with over 50 years aerospace engineering: Stress Analyst to Chief of Structural Sciences on numerous military aircraft, to Corp. Director Structures and Materials, Asst. Chief Engineer Space Shuttle Program through first three flights (awarded NASA Public Service Medal), Rockwell International Corp.; Program Manager Concorde SST, VP Engineering TRE Corp.; Aerospace Consultant.

The Improved Ion Engine

When we have discussed using ion engines to propel space craft in the past, we have talked about an engine that used two plates and electrical currents to propel particles (ions) out the exhaust which has the effect of pushing the craft. The ion engine is an engine that slowly build up speed in space. When it reaches top speed it is one of our fastest, if not the fastest, propulsion unit available. The European Space Agency is responsible for developing a new version of this new engine. It is named the Dual Stage 4 Grid ion thruster or DS4G.

There has been a break through recently in ion engines. The new engine is so fast that it could be used to travel outside the solar system. These are the words of the manager of the new project. So how fast is this new engine? The exhaust of the new engine is able to travel at the speed of 210,000 m/s. The other ion engine exhausts didn't reach a fourth of that. So how was this engine able to achieve these speeds when the other ion engines couldn't? First, you have to understand how an ion engine works. The engine is composed of three grids with micro sized holes in them. The first grid uses a high voltage. There is a chamber attached that has many thousands of charged particles. A low voltage is applied to the last grid. The voltage over the gap creates an electric field and the ions are accelerated out of the back. There is a problem with this procedure however. If too much voltage is applied than the plates began to deteriorate and the ions are bottle necked. Scientists knew that the more voltage that was used the faster the acceleration but were stymied by the deterioration factor.

What good was it to increase voltage and destroy the engine? Well this has been overcome in the new engine. The DS4G uses two pairs of grids instead of three individual ones. The engine is a two stage engine uses two grids and very high voltage in the first stage. This allows the ions to leave the grids without any problems. The other pair of grids is placed much further away and uses low voltage. The difference in the voltage powers the ions out of the exhaust.

This initial four fold + increase in speed is quite a leap forward. We may be able to have regular space travel soon because of this. The thing that is now holding up the practical application is development. While the engine is working perfectly in the lab, it must be tested exhaustively. We certainly don't want any people stranded in space because the engine fails them. Think of the possibilities, trips to Jupiter's moons may someday become routine. The ESA (European Space Agency) is even talking about flying out to the objects that lay beyond Pluto our furthest planet. Scientists were able to get 30K volts difference out of the engine so far, but this could itself be doubled or tripled in the future, increasing the thrust even more. While the engine is still a far cry from what we would need for interstellar flight, it may be perfectly suitable for our needs of flying through the solar system now.

Let's see how good my math is. Mars is 33,900,000 miles from Earth at it's closest point and 54,600,000 miles at the furthermost. We get our ship ready to fly there and it is at the furthermost point away. We know that the engine exhaust is 210,000 meters per second. Lets assume for the sake of simplicity that we can fly straight to Mars and that the ship will be flying at full speed. I know that this is impossible since it takes some time to build up the speed but let's see what we get. It looks to me that if you convert the speed to miles per hour you are talking about flying at 131 mph. I get this by taking 210,000 meters per second and dividing by 39.5 inches, the amount of inches in one meter. This gives me 8,295,000 inches per second of speed. I divide the inches by 12 and I get 691,250 feet per second. There is 5280 feet in a mile so I divide 691,250 by 5280 and I get 130.91856 miles per second.

Next I take the distance of Mars from Earth 54,600,000 and divide it by our speed of 130.91865 miles per second. The trip will last about 58 hours. This was just an exercise. We know that the engine will take a couple of months to achieve full speed but the trip will still be a very short one by current standards. The engine proves itself even more on planets that are further away. It still only takes the same time fo reach full speed so the advantage of top speed is greater the further you go.

By the way, the former ion engine would have resulted in a figure of 908 hours to Mars using the same distances, if the engine could have held together that long. It also would have required longer build up time to reach its full speed. If scientists can find a way to make this engine accelerate faster, perhaps in days instead of months, they would really have something. Can you imagine a one way trip to mars in about 3 days or the moon in a couple of hours.

I would be remiss if I didn't mention the fact that this new engine was developed in only four months. This just goes to show you what the human mind is capable of if it tries. Will this be the dawn of a new space age? Will we finally colonize other planets and moons? When this engine is fully tested and put into production it may just signal a new age for mankind.