Go at Throttle Up!

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If you know the meaning of this phrase, Go at Throttle Up!, it is because you are familiar with terminology associated with the launch of a Space Shuttle. Or at least you were back when that was a going concern. It is no longer; a going concern – that is. I have heard the phrase myself scores of times, but that’s because I am, or at least was, an Aerospace engineer. In fact the Space Shuttle program was my first job out of college as a recent graduate.

For as many times as I have heard the phrase I’ve always experienced it with a certain measure of awe, but for three times in particular it represents moments crystallized in time. More on that later.

First, let me describe what the phrase means, practically. As any rocket ascends though the atmosphere, the shuttle included, it accelerates towards the target height and velocity that is required to achieve orbit. In other words it has got to get high enough and fast enough to stay in orbit, otherwise it will simply fall back to earth. Since it started with zero velocity and has to get to a fast velocity, at each point in the ascent it is going ever faster. As for the atmosphere, it represents a continuum, from thick and dense at sea level, and becomes thinner as altitude increases until, it vanishes altogether, thus defining the boundary to space. So, the shuttle starts out slow, in a dense medium, and ends up going really fast in a vacuum. Problem is that between those extremes there is a phase when the speed is just fast enough, and the atmosphere just thick enough that, left unmitigated the vehicle will suffer structural damage. In proper aerospace engineering terminology, this region of flight is called Max Q, or maximum dynamic pressure.

space shuttle - DRAWING - go at throttle up

(original art by the author, cross-posted at http://larueart.blogspot.com/2012/06/goodness-knows.html )

The mitigation strategy is two-fold; the flight trajectory includes a roll maneuver shortly after liftoff to minimize angle-of-attack related drag, and, the three main engines are commanded to a reduced throttle setting, just low enough to slightly decrease acceleration until the Max Q region has passed. Once out of Max Q the engines are commanded back to full throttle, hence the in-flight confirmation over the mission control voice link – “Go at Throttle Up!”

It is important to note that when they come, those words are kind of a celebration – remember spaceflight is dangerous – spoken with a measure of relief. They denote that the most risky part of the ascent is over. Steady on to MECO (main engine cutoff), but the worst is behind us.

As for my moments of awe, the first came very early on an April morning, seemingly, a lifetime ago. A student of Aerospace Engineering at the time, I remember clearly the excitement of the launch, filled with anticipation of what it might be like to actually work on such a majestic project. Remember, this was at a time when the nation still brimmed with excitement at America’s accomplishments in space, and this was the dawn of a new era; I was certainly caught up as well – “Go at Throttle Up!

My second remembrance, which was symbolic of a handful more, came when I, a recent graduate, and new-hire, had the privilege of actually supporting day-of-launch activities, monitoring the Shuttle first-stage ascent, real-time from the Rockwell International (my first employer) mission support room in Downey California. Imagine my excitement, watching strip charts showing telemetered data, live, from the launch, and hearing those words, first-hand over the official voice link – “Go at Throttle Up!

Finally, in horror, disbelief and sorrow I heard the playback on the news, the day of the Challenger tragedy, in the winter of 1986. I had since taken a new job with Northrop to work on the B-2 Bomber, so I heard the news second-hand. Still, I had my roots in the Shuttle Program, and I had worked with several of the astronauts who perished that day. Ironically, the cause of that accident was traced to an o-ring failure in which solid rocket booster leakage acted as a torch to burn through the external fuel tank. This led to the catastrophic failure, after Max Q had passed, when the riskiest part of the ascent was supposedly behind, and everyone was relieved have already heard the words – “Go at Throttle Up!

When I took the job with Northrop I had switched disciplines to that of systems engineer, no longer involved with the hard science aspects of aerodynamics, flight control and propulsion. I was happy to fill the role of the systems engineer tackling a different part of the problem space. I was happy and privileged once again for the chance to work the premier aerospace project of its time. Fact is now though, I am no longer an Aerospace engineer, sub-discipline notwithstanding… I am simply me, an engineer by training, but no longer a professional in the field.

I am wondering if, in the continuum of my life, if that was the moment I stopped being an Aerospace engineer, that day in 1986. Many years of gainful employment and legitimate contributions and accomplishments followed, but still… was that the moment I was left to discover my future on my own, for myself, just as I am now, discovering my future, recreating myself. Was that the moment, the moment of passage? From present to future, from the realm of our atmosphere to the unknown that is space… was that that moment? – “Go at Throttle Up!

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2 Responses to “Go at Throttle Up!”

  1. David Dalton says:

    Great article. Thanks for clearing some things up for me…