Fireside Chat: Let’s talk Asbestos. Let’s talk the Space Shuttle Challenger Explosion. Let’s talk both. Lesson No. 1

The Space Shuttle Challenger explosion was so grievous that many of us remember our exact location on January 28, 1986 at 11:38 a.m. EST; for me, that was in a restaurant next to the Union Bank Building in Grand Rapids, Michigan with a bunch of the attorneys watching the launch on a big screen television. 73 seconds into the liftoff, teacher Christa McAuliffe and six other astronauts tragically lost their lives while in the pursuit of science and a teaching moment for children around the world. 

Although a remarkable number of publications exist concerning the alleged causes of the joint failure on the right-hand solid rocket booster, some assertions remain controversial or have journeyed more into the realm of mythology than fact.  My Fall 2021 thesis for the University of Colorado at Colorado Springs Masters in History Program will focus on these controversies. I am also honored to have received a 2021 Clark-Yudkin Research Fellowship and grant for my efforts in this area from The Friends of the Air Force Academy Library. The Fellowship primarily provides me access to an amazing archived collection that I will be reviewing in depth for most of next week and then later as needed. In exchange, I have committed to publish my work within a year, provide a copy to them of the publication and, if requested, make a presentation to an audience of colleagues and cadets at the Academy. I was one of two such Fellowships granted in 2021.

Let’s examine one of these assertions that has been debated on the Internet since the inception of social media: Myth or fact? Was the Challenger explosion caused by an asbestos substitute that failed?

Let’s rephrase that question in a way which is more interesting and catches the nuance of what really happened on that fateful day. Did these people horrifically die hitting the water at 200 miles per hour and was the space shuttle program crippled for two and 1/2 years all because of the need to find a substitute for an asbestos containing product that had previously worked flawlessly during the first 24 space shuttle flights? If so, then why. In attempting to answer this question, I have been participating in weekly one hour discussions with the rocket scientist now retired from Morton Thiokol who was responsible for the solid rocket booster joint and, in particular, the asbestos containing putty at issue that was used in the field joint to help the O-ring.

If you just Googled this topic on the Internet, then you have crossed the line into mythology, and I need to bring you back. On the other hand, if you just watched the four part Netflix series on the Challenger, then you have a good foundation to dig past the O-ring and into the analytical weeds of what happened. Let’s begin our conversation by eliminating many of the opinions and claims readily available over the Internet and then discussing the relevant design aspects.

First of all, let’s eliminate the crazies and the conspiracy theories. If you would like additional details on those types of claims, then read Truth, Lies, and O-rings: Inside the Space Shuttle Challenger Disaster by Allan McDonald and James Hansen published in 2009 with a focus starting on page 511 (Apple Books electronic version) in which McDonald (Thiokol rocket scientist who is the hero in this story, if there can be a hero) discusses and debunks such claims. The armchair experts claimed failure mechanisms ranged from an expert marksman shooting the shuttle at liftoff, structural failure of the solid rocket motor case, structural failure of the struts, cracks in the solid propellant grain, failure of internal insulation, leaks in the External Tank causing the solid rocket booster joint to overheat from a hydrogen fire, exhaust plume interactions, to a “hard left turn of the huge mobile transporter that moved the shuttle on the mobile launch platform to the launchpad”. Some of these are tough to disprove, but generally are not supported, per McDonald, by the flight films or telemetry data.

The area of failure as found by the Roger’s Commission appointed by the President of the United States to investigate the explosion, and at this point supported by all of the experts, involves blow holes in the vacuum putty and erosion and blow-by in the O-rings causing the two O-rings failing to seal at launch. The hole was quickly resealed by aluminum oxides before any flames could escape.  About 37 seconds into flight, wind shear tore the seal back open, resulting in the eventual explosion.

The joint which failed is the aft field-joint in the right hand solid rocket booster which is depicted below.

The design of this field joint included, among other components, two O-rings supported by the vacuum putty. The vacuum putty was to provide a thermal barrier to the O-rings, with the understanding that blowholes (air pockets) in the putty could contribute to the erosion of the O-rings. The details of the failure area in comparison to the re-design after the explosion is as follows:

The area discussed above as “Zinc Chromate Putty”, or otherwise referred to as the vacuum putty, is where the asbestos controversy exists. Notice that the use of the vacuum putty was eliminated in the post-explosion redesign. As stated by the NASA executive in charge of the solid rocket boosters, Lawrence Mulloy, in his May 7, 1986 testimony to the Roger’s Commission, the primary cause of the O-ring erosion was the blowholes in the vacuum putty. An extensive discussion on the putty is provided in Challenger: The Final Voyage by Richard Lewis authored in 1988 on pages starting with 79.

As to the vacuum putty, the literature is certain in one aspect: that the original putty supplied by Fuller-O’Brien which was discontinued prior to the January 28, 1986 Challenger explosion included an asbestos fiber component.  However, we currently do not know from the available literature for the type of asbestos fiber, the percentage content of the asbestos, or the specification for its asbestos content. As to why Fuller-O’Brien discontinued the putty from the market, the mythology of the situation currently trumps the facts. The Rogers Commission report and The Asbestos Racket by Michael Bennett claim that it was discontinued because Fuller-O’Brien was concerned about asbestos related lawsuits.  NASA employee Richard Cook’s July 23, 1985 memo to his supervisor claims that the putty was discontinued as being banned by the Environmental Protection Agency, a statement that Cook continues to stand behind today based on his May 5, 2021 email to me in response to my questions. 

Joseph Trento’s book entitled Prescription for Disaster: From the Glory of Apollo to the Betrayal of the Shuttle claims that the company no longer sold the putty based on a 1977 Consumer Product Safety Commission ruling which banned asbestos in certain consumer patching compounds. Trento’s book also claims that the putty was removed “from the market by NASA because it contained asbestos.” Malcolm Ross’s 2008 letter to the editor of Elements Magazine points to Fuller-O’Brien voluntarily deciding to discontinue the putty because of the 1977 Consumer Product Safety Commission ruling.

Also, still needing to be confirmed is whether the replacement vacuum putty manufactured by Randolph Products, and which was involved with the Challenger explosion, also contained asbestos fibers. Malcolm Ross in his 2008 letter referred to above claims that it did. Roger Boisjoly, a Thiokol rocket scientist who was the most knowledgeable on the solid rocket booster overall design, and now deceased, co-authored a 2002 journal article stating that “The subsequent putty used did not contain asbestos.” Brian Russell, who was responsible for the joint and putty, states that the replacement putty did contain asbestos and he supports his claim with his notes from the early to mid-1980s discussing the putty. The Internet contains other myths as at least one website claims that neither the Fuller-O’Brien or the Randolph putties utilized asbestos but, rather, that asbestos was added after the Challenger explosion for use in future flights.  That article authored by Jason Spaull and entitled “Asbestos and the space race”, states:

“…it is said that the challenger disaster could have been averted if asbestos was used in the sealant around the failed O ring which caused the disaster.  Asbestos was used on later space shuttle missions to ensure the same components did not fail again.”

As I mentioned at the beginning of this Blog, my goal in undertaking this research will be to separate the myths from the facts.

In regard to whether the Challenger explosion was caused by an asbestos substitute that failed, we will necessarily also discuss the other potential causes of the explosion, their interaction with the vacuum putty and other components of the aft field joint, and how the world might have been changed, or might not have been changed, if Fuller-O’Brien had continued to manufacture its vacuum putty which contained asbestos.

For my friends who are into either asbestos lore or the Space Shuttle Challenger explosion, or both, feel free to provide your thoughts on my research and potential avenues of additional discoveries.

The journey has just begun and I hope that you will go down this path with me. I would appreciate your thoughts in the comments or by email to me at TheAsbestosBlog@gmail.com.