Wayne Hale’s NASA Blog: Riding the Phugoid

December 12, 2008
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Phugoid, for the non-aviators, refers to a long term longitudinal oscillation in the flight path of a flying machine. More precisely it is the exchange of altitude for airspeed with constant angle of attack. Whew, I had to look it up in my old textbooks to get it right. One of the on-line helps says that the engineer that invented the term “phugoid” took it from the Latin but got the translation wrong. That figures. Most engineers don’t know that the ancient Romans studied aircraft control.

We studied phugoidal motion a lot when analyzing shuttle re-entry. It is most pronounced on an abort entry where the shuttle’s forward motion doesn’t create enough lift until the vehicle falls into the denser part of the atmosphere and then there is too much lift so it bounces upward to where there is not enough lift and then it falls down to where the dense air creates too much lift and causes it to climb up to where there isn’t as much air where . . . . Well, you get the picture. Not exactly a roller coaster, but somewhat disconcerting.

If you are designing a re-entry vehicle with any lift at all, studying the aerodynamics so that lift and drag can be applied in the proper way at the proper time is crucial. During the early portions of the shuttle entry, phugoids are to be avoided since they can lead to high heating which is . . . not a good thing. Actually, the shuttle flies something called equilibrium glide for most of the entry phase. This term refers to a state where the lift generated is exactly equal to the orbital mechanics forces and gravity. In that state, the shuttle flies at a relatively constant altitude for a fairly long period of time, all the while bleeding off the incredible kinetic energy required to orbit the earth.

This is a good time of year to talk about how to fly through life: are you riding the phugoid or are you in equilibrium glide? I know where I am. Yesterday was a real emotional high when the snow dusted my home and the shuttle flew over on its way back to Florida; then there were the stressful lows — like when I tried to untangle the Christmas tree lights . . . .

My job has continued to move away from the purely technical to a place where people skills are increasingly important. One of my “other duties as assigned” is to represent the agency from time to time with the folks in the media. The prospect of having this kind of interaction causes a lot of people in NASA to refuse promotions . . . engineering being generally considered to be more important than talking to the public or dealing with the media.

One of the new phenomenon in media is the blossoming of the blogosphere — exactly where we are today. The neat thing about the internet and blogs is that anyone can spread a lot of knowledge and insight to many folks in a very rapid and inexpensive way. The sad thing about the internet and blogs is that there is so much misinformation and personal opinion passing for fact out there. In the last few months I have become much more involved in the new media.

Some of it makes me miss the old media. It is sad to see reputable old style news organizations in financial trouble laying off experienced and professional journalists, for example. And being over the age of . . .. (ahem) 30 . . . I still prefer the feel of a real newspaper in my hands toreading streaming news off a computer screen. But, OK, things change and we all have to learn to use the new tools.

My biggest problem with blogs and the internet — and I’m far from being the first to observe this — is the continual flame wars that go on. Seems like everything posted attracts someone with a contrary view — that’s OK, in fact, that’s a good thing — but too frequently a contrary view stated in the most vituperative and inflammatory way. A good exchange of views can be enlightening. A rude exchange of person insults is just depressing. Sigh. Makes me want to repeat the old SNL line: “can’t we just all get along?”

To participate in this new world of internet interaction, you have to develop a thick skin. Recognize the valuable components of a enthusiastic exchange of ideas and ignore the ad hominem and personal attacks and general lack of civility that seems to be rampant on the web these days.

Its hard to avoid riding the phugoid between the highs that happen because of a great and productive exchange of ideas and information, and the lows that come with depressing and inappropriate personal attacks.

So my aerospace analogy, at least for the holiday season, is to avoid the phugoid and try to stay on the equilibrium glide as long as you have the energy.

Hey, that probably applies to family get togethers for the holidays, too! Don’t sweat the small stuff.

SpaceRef staff editor.