Another Old Saying

“There is nothing as expensive as a dead crew, especially one dead from a bad management decision.”  --  G. W. Johnson

The history ---

Space Shuttle Challenger:

Bad multiple-O-ring joint design based on false thinking of “if 1 is good, 2 must be better”.

Decision to fly cold when “everybody’s engineers” said not to.

Result: 7 dead, nearly 2-year stand-down costing ~$billions

Space Shuttle Columbia:

Decision not to even look for possible wing damage on Columbia before entry.

Decision not to fly tile repair kit on any Space Shuttles, prior to Columbia fatal flight.

Result: 7 dead, more than a year stand-down, costing ~$billion

Apollo 1 fire (3 dead) & loss of “Liberty Bell” Mercury capsule (none dead):

Not included because the design and operation errors were made before much experience had been obtained. With the decades of experiences doing orbital vehicle designs available today, that excuse no longer obtains!

The current dilemma ---

Artemis-2 Orion heat shield (4 crew at risk):

Cheaper-variant Orion heat shield installed on 2 capsules, without first verifying it in flight on the unmanned Artemis-1 flight. It failed to verify on that flight! See photo.

Fly Artemis-2 crewed with flawed heat shield anyway, just ease the entry trajectory a bit. This is to avoid the expense and delay of replacing it with a known-to-be-good heat shield, verified on the very first Orion flight, before the Artemis program began.

               Result? -- we will soon see!

Final Remarks:

While NASA learned a great deal from these incidents and the inquests that followed them, I fear they have not learned the very fundamental lesson embodied in my old saying: the safety of crew lives must out-prioritize unconditionally any schedule or budget considerations! If they had learned it, there would be no dilemma regarding the Artemis-2 heat shield. But there is!

NASA is not the only outfit afflicted with this lack of proper priorities on the part of decision-making upper management. We just saw it in action with the Boeing “Starliner” debacle that stranded its crew at the space station. Design practices verified over 6 decades to use when handling storable hypergolic propellants, were ignored by corporate management in favor of cheaper approaches long known not to be reliable, thus leading to the thruster failures seen during the mission. While the crew survived just fine, they were in fact endangered by these failures.

Photo:  Post Flight View of Artemis-1 Cheaper-Variant Orion Heat Shield

Here is the background:

The Apollo heat shield was epoxy novolac Avcoat ablative, hand-gunned into the cells of a fiberglass hex honeycomb bonded to the capsule substrate. This is very labor-intensive, and thus expensive, and it consumes considerable schedule time. This flew on Apollo and on the first Orion flight test before there was an Artemis program, quite successfully, but was even more expensive and time-consuming than Apollo, because Orion is substantially larger than Apollo (near 400,000 cells to hand-gun, versus Apollo’s just about 300,000 cells).

This heat shield choice was switched during the Artemis program for bonded-in-place Avcoat tiles machined from blocks of cast Avcoat, but without the reinforcing fiberglass hex in any form. That saved a lot of time and money, and was installed on the two Orion capsules intended for the Artemis-1 (unmanned) and Artemis-2 (manned) flights, without ever having been test flown! However, it showed very unexpected damage in the form of the loss of chunks of char, on that first unmanned Artemis-1 flight.

The Artemis-1 unmanned flight not only was the first test of the alternate heat shield, it was also the first flight test of a revised entry protocol involving a skip outside the atmosphere between two entry deceleration and heating events. The last time this occurred was an unintended skip during a suborbital X-15 entry, many years before. It is simply impossible to separate and quantify the effects of the skip re-entry from the lack-of-fiberglass hex, from this one flight test!

Ground tests and computer analyses would seem to indicate that eliminating the entry skip might increase the performance of the heat shield as it was installed without the hex, for the Artemis-2 flight. This is primarily based upon the contention that gas evolution deep in the heat shield blew chunks of char loose between the two entry pulses on the Artemis-1 flight.

However, in my considerable experiences with ablatives in rockets and ramjets, most char is inherently porous, being rather similar to the charcoal used in barbecue grills, and thus it is simply unable to sustain any such evolved gas pressure! It should leak through as fast as it forms.

That whole question does not matter! Actual flight test data outweighs any possible ground tests or computer analyses! It always has! And it always will!

I have since come up with a way to easily and reliably incorporate the fiberglass hex into the cast blocks of Avcoat, that can be machined into the bonded tiles that NASA really wants to use on the Orion for Artemis. I gave this concept to NASA, and they are indeed looking closely at it. But the proper prioritization of crew lives above schedule or budget requires that this alternate approach also be flown unmanned, before ever risking a crew’s lives on it!

What NASA really should do is pull the heat shield from the Artemis-2 Orion, and replace it with either the Apollo-type hand-gunned heat shield for a manned flight, or else test some sort of hex-in-tiles alternative on it, unmanned. Either way, they need another unmanned flight test to demonstrate the effectiveness of any revised heat shield, before they ever fly manned with it.

I see no NASA plans to make any of this happen! They instead will fly the existing demonstrably-flawed heat shield, manned, for Artemis-2, just with the no-skip entry trajectory that might (or might not) ease the char chunk shedding. I have seen nothing to suggest they are planning any other unmanned flight tests to properly verify any revised heat shield design.

The inevitable conclusion:

Therefore, I must assume that NASA upper management has never, ever learned the most fundamental lesson of all from two dead shuttle crews, that being the lesson specifically embodied in my saying: prioritize the safety of crew lives above any schedule or cost impacts, no exceptions!