My First Rocket Motor Test

written by David Mixson

When I started at NASA, the project I worked on was called the Technology Test Bed (TTB). In this program, we tested a highly instrumented Space Shuttle Main Engine (SSME) liquid rocket motor. I’m not sure the tests made the rocket better, but they certainly made good engineers BETTER engineers.

And when we fired the motor, Huntsville, Alabama came alive! It’s hard not to notice a rocket throwing out enough energy to convert thousands of gallons of water into steam in an instant. And it boldly reminded folks in North Alabama why Huntsville is called “Rocket City.”

I thought it was neat that I had the credentials to be inside the control room when we tested the rocket. With the confidence of a fresh-out engineering graduate who thought the world was his for the taking, I reminded my friends as often as I could that I worked inside the blockhouse during tests.

Looking back now through the lens of a fifty-something-year-old, I realize the senior engineers never let me do anything that would blow up if I screwed up.

My small part of the test was to help configure the thirteen locomotive engines that pumped water onto the massive steel flame bucket. The bucket had thousands of tiny holes, and we pumped water from a water tower through pipes big enough to stand inside to the flame bucket. We did this to keep the steel from melting and to absorb the sound from the rocket exhaust.

The more experienced engineers configured the cryogenic Liquid Hydrogen and Liquid Oxygen systems that fed the motor.

Thinking about my first full-scale rocket motor test gives me goosebumps. Feeling a rocket roar was better than any drug I could imagine. But, in full disclosure, I always took the random drug testing mandate seriously when I was working at NASA. So, I can’t know for sure.

In 1998, this test stand was deactivated, and MSFC hasn’t tested a rocket motor that launched humans into space since. In the name of politics, the Stennis Space Center got the nod to do ALL full-scale liquid motor tests.

In the end, this turned out to be a horrible idea—and MSFC has never been the same. I’ll expand on that topic in other articles.

More tomorrow.



In 2019, Blue Origin signed a Commercial Space Act Agreement (SAA) with MSFC to use the 4670 test stand to test their non-NASA BE-3U and BE-4 rocket motors. Blue is refurbishing the test stand and facilities as part of the agreement. “Rocket City” (Huntsville, Alabama) was certainly a more exciting place to live when rocket motors roared in the distance. Thanks to Blue Origin, that excitement is about to return.

* This article originally appeared on LinkedIn as part of the “Make NASA Great” series.

Rocket Motor Test at MSFC

There's nothing quite like watching a rocket motor roar.

About the Author

David Mixson writes about Old Space and New Space. He worked as an engineer at NASA for more than thirty years and is the author of three books.

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