| Engineers are the professionals who take care of the | | | | temperature rose to a more suitable level. |
| creation of new products and the processes that | | | | The NASA managers rejected the recommendation |
| create these products for the benefits and | | | | as they believed the solid rocket boosters would be |
| enjoyment of the human race. They work hard to | | | | able to perform well, even at the expected low |
| improve the convenience and beauty of our society. | | | | temperature of 26 degree Fahrenheit as their design |
| These are the folks who make possible great | | | | called for performance at as low as 31 degree |
| technological leaps that were thought possible only in | | | | Fahrenheit. Under the pressure from NASA manager, |
| science fictions. | | | | Morton-Thiokol managers changed their |
| Aeronautical and aerospace projects normally take a | | | | recommendation to proceeding with the launch, |
| long time to implement and involve great costs. | | | | despite the strong protests from their engineers who |
| Correcting a design defect can be very costly and | | | | could not prove conclusive that the filed joints were |
| time consuming. Economic cost consideration may not | | | | indeed faulty. |
| always permit major redesigning to be performed | | | | Case 2 - The DC-10 Case |
| and so sometimes only remedial actions can be taken. | | | | In 1974, the first fully loaded DC-10 jumbo jet |
| The remedial actions, if at all carried out, may not | | | | exploded over the suburbs of Paris, killing 346 people, |
| always be effective. In order to better appreciate | | | | a record at that time for a single-plane crash. This |
| the dilemmas faced by engineers when they | | | | was said to be an accident waiting to happen |
| encounter design faults, we shall focus our discussion | | | | because it was known to the designers that the |
| on the following two well-known cases: | | | | design of the plane was defective because the cargo |
| 1. Challenger Space Shuttle case | | | | door could burst open during flight. |
| 2. DC-10 Jumbo Jet Case | | | | The fuselage of the DC-10 jumbo subcontracted to |
| Case 1 - Challenger Space Shuttle Case | | | | Convair by McDonnell Douglas. Dan Applegate worked |
| In order to better appreciate this case, it is useful for | | | | as Convair senior engineer directing the project. Dan |
| us to first look at some of the background | | | | wrote a memo to the vice president of Convair |
| information. | | | | identifying the various dangers that could arise from |
| Orbiter is the main space vehicle in the space shuttle. | | | | the design of the fuselage. He highlighted a few |
| It has three main rocket engines. Most of the | | | | potential dangers, especially with regards to the |
| hydrogen fuel together with the oxygen needed to | | | | possibility of disaster due to the failure of the cargo |
| support rapid engine fire, are carried in a huge | | | | door. He detailed how the cargo doors could burst |
| external tank. The tank is jettisoned when empty | | | | open during flight resulting in the decompression of |
| after about eight and a half minutes from lift-off. | | | | the cargo space, leading to the collapse the floor of |
| Due to the heavy load and the nature of the | | | | the passenger cabin above. When that happens, the |
| hydrogen-fired rocket engines, additional thrust is | | | | control lines running along the cabin floor would be |
| needed to speed up the shuttle to escape from | | | | damaged and the plane could not be controlled. |
| gravitational pull. Two solid rocket boosters are | | | | The senior engineer therefore recommended that |
| employed. Solid fuel is used because it provides much | | | | the doors be designed and at the same time |
| greater thrust than liquid hydrogen fuel. One | | | | strengthen the cabin floor. He warned that such |
| disadvantage with the sold-fuel rocket is that once | | | | making the changes as he recommended would lead |
| fired, it cannot be stopped until the fuel runs out. | | | | to some of the DC-10 cargo doors being forced |
| The booster rockets are huge and long. While the | | | | open during flight and plane crash would result. |
| booster rockets are manufactured in the factory, | | | | While the top management at Convair did not |
| they are manufactured in segments and transported | | | | disagree with technical analysis of Applegate or his |
| to the space center in five segments. These five | | | | warning, they maintained that Convair might face |
| segments are put together at the launch site at the | | | | possible financial liabilities if they were to pass on this |
| space center. Since the segments are joined | | | | information to McDonnell Douglas. These liabilities could |
| together at the launch site, the joints are called field | | | | be severe since the cost of redesign and the delay |
| joints. The field joint design, while creative and with | | | | to make the necessary safety improvements would |
| engineering ingenuity, was found to be less than | | | | be very high and would occur at a time when |
| desired. The redesigning process was slow and the | | | | McDonnell Douglas would be placed at a competitive |
| new design was not ready. Tests had indicated less | | | | disadvantage. |
| than desired performance for the existing field joint | | | | Observations: |
| design especially when the operating temperature is | | | | There are close parallels between the two cases. |
| low. | | | | Both designs were known to be flawed by the |
| On the night before the Challenger space shuttle was | | | | engineers who tried to alert the management but the |
| to be launched on Jan 28, 1986, Morton-Thiokol, the | | | | management decisions were clouded by monetary |
| maker of the solid rockets boosters, were worried | | | | considerations which led to the eventual loss of the |
| that the solid rocket boosters might cause problem | | | | crafts and the lives of the occupants. In both cases, |
| due to the cold weather. They held a teleconference | | | | engineering hats were removed and management |
| with NASA managers to present their concerns and | | | | hats put on. |
| recommended that the launch be postponed till the | | | | |