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Monday, September 21, 2015

Reading List: Sacramento's Moon Rockets

Lawrie, Alan. Sacramento's Moon Rockets. Charleston, SC: Arcadia Publishing, 2015. ISBN 978-1-4671-3389-0.
In 1849 gold was discovered in California, setting off a gold rush which would bring a wave of prospectors and fortune seekers into one of the greatest booms in American history. By the early 20th century, the grizzled prospector panning for gold had given way to industrial extraction of the metal. In an age before anybody had heard the word “environmentalism”, this was accomplished in the most direct way possible: man made lakes were created on gold-bearing land, then a barge would dredge up the bottom and mix it with mercury, which would form an amalgam with the gold. The gold could later be separated, purified, and sold.

The process effectively destroyed the land on which it was used. The topsoil was ripped out, vegetation killed, and the jumbled remains after extraction dumped in barren hills of tailings. Half a century later, the mined-out land was considered unusable for either agriculture or residential construction. Some described it as a “moonscape”.

It was perhaps appropriate that, in the 1960s, this stark terrain became home to the test stands on which the upper stage of NASA's Saturn rockets were developed and tested before flight. Every Saturn upper stage, including those which launched Apollo flights to the Moon, underwent a full-duration flight qualification firing there before being shipped to Florida for launch.

When the Saturn project was approved, Douglas Aircraft Company won the contract to develop the upper stage, which would be powered by liquid hydrogen and liquid oxygen (LH2/LOX) and have the ability to restart in space, allowing the Apollo spacecraft to leave Earth orbit on a trajectory bound for the Moon. The initial upper stage was called the S-IV, and was used as the second stage of the Saturn I launcher flown between 1961 and 1965 to demonstrate heavy lift booster operations and do development work related to the Apollo project. The S-IV used a cluster of six RL10 engines, at the time the largest operational LH2/LOX engine. The Saturn I had eight engines on its first stage and six engines on the S-IV. Given the reliability of rocket engines at the time, many engineers were dubious of getting fourteen engines to work on every launch (although the Saturn I did have a limited engine out capability). Skeptics called it “Cluster's last stand.”

The S-IV stages were manufactured at the Douglas plant in Huntington Beach, California, but there was no suitable location near the plant where they could be tested. The abandoned mining land near Sacramento had been acquired by Aerojet for rocket testing, and Douglas purchased a portion for its own use. The outsized S-IV stage was very difficult to transport by road, so the ability to ship it by water from southern California to the test site via San Francisco Bay and the Sacramento River was a major advantage of the location.

The operational launchers for Apollo missions would be the Saturn IB and Saturn V, with the Saturn IB used for Earth orbital missions and the Saturn V for Moon flights and launching space stations. An upgraded upper stage, the S-IVB, would be used by these launchers, as the second stage of the Saturn IB and the third stage of the Saturn V. (S-IVBs for the two launchers differed in details, but the basic configuration was the same.) The six RL-10 engines of the S-IV were replaced by a single much more powerful J-2 engine which had, by that time, become available.

The Sacramento test facility was modified to do development and preflight testing of the S-IVB, and proceeded to test every flight stage. No rocket firing is ever routine, and in 1965 and 1967 explosions destroyed an S-IV test article and a flight S-IVB stage which was scheduled to be used in Apollo 8. Fortunately, there were no casualties from these spectacular accidents, and they provided the first data on the effects of large scale LH2/LOX explosions which proved to be far more benign than had been feared. It had been predicted that a LH2/LOX explosion would produce a blast equal to 65% of the propellant mass of TNT when, in fact, the measured blast was just 5% TNT equivalent mass. It's nice to know, but an expensive way to learn.

This book is not a detailed history of the Sacramento test facility but rather a photo gallery showing the construction of the site; transportation of stages by sea, road, and later by the amazing Super Guppy airplane; testing of S-IV and S-IVB stages; explosions and their aftermath; and a visit to the site fifty years later. The photos have well-researched and informative captions.

When you think of the Apollo program, the Cape, Houston, Huntsville, and maybe Slidell come to mind, but rarely Sacramento. And yet every Apollo mission relied upon a rocket stage tested at the Rancho Cordova site near that city. Here is a part of the grandiose effort to go to the Moon you probably haven't seen before. The book is just 96 pages and expensive (a small print run and colour on almost every page will do that), but there are many pictures collected here I've seen nowhere else.

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