The results and interpretation of the results are equally ridiculous. A 2-inch fall in a padded chair causes 2.24 gs, "a considerable load for the human spine to bear." One should note that roller coasters often sustain 4 gs for brief periods. The human spine bears the entire load. Most people emerge unscathed.

The Shock and Vibration Handbook, 3rd ed., states that the vertical acceleration from a sitting position which will leave the subject "uninjured, undebilitated" is 15 gs. Aircraft ejection seats are designed to impart accelerations of up to 15 gs.

In the article, Herman M. Giesen was quoted as saying, "It was remarkable to see the reverberation in very high mechanical frequency rippling up and down the backbone." A high-frequency vibration in the human spine would be remarkable indeed. The soft discs between each vertebra would prevent a high-frequency vibration from occurring. The human spine does not transmit frequencies above 20 Hz without substantial attenuation (Shock and Vibration Handbook, 3rd ed., Harris). The species of humans with straight spines might also have rigidly connected vertebrae.

Now if you will excuse me, I will get off my soapbox and sit down very gently so as not to injure my spine.

The engineer prepared a report and offered opinions outside his area of expertise. The engineer is quoted, "Since I am not an expert in mechanical analysis of this sort, I sought counsel from mechanical analysis experts I respect." Although it is admirable that the engineer sought opinions of others, representing oneself as an expert and offering professional opinions outside one's area of competence is contrary to the National Society of Professional Engineers' code of ethics, which states engineers shall "perform services only in areas of their competence." (NSPE Code of Ethics for Engineer, Fundamental Canon 2). A biomechanical engineer is necessary to opine in this field.

Another problem with the engineer's conclusions is that no attempt was made to verify the results of his simulation with real-world data.

The article writer uses the misnomer "g-force." A first-year college physics course would teach the difference between acceleration and force. Mixing and matching terms as is done in this common news media misnomer should not be acceptable in a technical publication.

Not only do I agree with him, but in school we were taught two systems of measurement:

S.I. = Systeme Internationale.

S.U. = Stupid Units (English system).

He says, "Interactive graphics technology goes back to the mid-1950s and the U.S. Air Force's SAGE Project." In fact, graphic displays on the CRT and interaction with the light pen were first demonstrated in the late 1940s on the Project Whirlwind computer in the Digital Computer Laboratory at MIT, directed by Jay Forrester. The Whirlwind computer made the concept of a semi-automatic ground environment for air defense feasible, and MIT and the Air Force brought the Lincoln Laboratory into existence to realize SAGE.

As Robert R. Everett, co-director of Project Whirlwind, when president of the MITRE Corp., put it in his foreword to a history of Whirlwind: "In the beginning MIT begat Whirlwind. Whirlwind begat SAGE."

Weisberg also attributes "large magnetic core memories" to SAGE, whereas Forrester invented the magnetic core memory at MIT as part of the Whirlwind Project.

On the origins of CAD, I first observed Whirlwind's graphics capabilities as an undergraduate on the GI Bill in the mechanical engineering department of MIT. My several years of drafting experience at the Bell Telephone Laboratories before and after my military service made evident the advantages of designing, not with pencil, paper, and eraser, but through CRT interaction.

With mechanical engineering faculty colleagues Steven A. Coons and Dwight B. Baumann and master's and doctoral theses students in mechanical engineering, starting in 1959, we fleshed out the fundamentals of graphics interaction, including originating the label "computer-aided design," taking care to insert the dash between "computer" and "aided" to express our conviction that while the computer was becoming a powerful assistant, the performance of design was (and is) a human endeavor.

In the early 1990s, I was asked by L. Piegl, the editor of Fundamental Developments of Computer-Aided Geometric Modeling to author a chapter on the MIT mechanical engineering experience, where I developed more thoroughly the contributions of individual faculty and students.

Truck and trailer springs are designed to carry the maximum load the vehicle is expected to carry. Also, springs are more efficient in reducing vibration when they are more heavily loaded.

The problem arises when cargo is relatively lightweight. Since the springs are not nearly fully loaded (compressed), their vibration isolation characteristics are reduced, and increased vibration can damage certain cargo.

Specific examples of lightweight cargo are air-conditioning units which, by their very nature, are mostly air space. Significant physical damage, including abrasions and fractures, has occurred to air-conditioning equipment.

Are there any industry standards or publications that deal with this subject? Can ASME stimulate some action toward researching and publicizing the problem and developing appropriate mitigation standards?

If this is so, then we don't need maglev or any other form of old-fashioned transportation. All we need is Star Trek's transporter, and we can travel about electronically with no moving parts.

Beam me up, Scotty. There are no intelligent life forms here.

I hate to nitpick, but there is a slight historical inaccuracy on the last page of the article. Wicks writes that Goddard died on Aug. 10, 1945, and was buried on August 14, the day that Japan surrendered on the battleship Missouri. It is true that Japan ceased fighting on Aug. 14, 1945, but the official surrender on the battleship Missouri took place in Tokyo Bay on September 2.

Aside from that, it was a wonderful article.

Correction

An article in the November 2000 issue carried an incorrect description of a Swagelok product. A new tube fitting is available in sizes up to 0.5 in. or 12 mm. The company plans to add larger sizes.

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