Did the Moonwatch need hesalite?

Kmmdad57 · Apr 4, 2026

I have heard so many times now that the original Moonwatch had to have a hesalite not sapphire crystal because if one breaks, it wouldn't be an issue of small fragments of sapphire floating around the spaceship that could get into components or be inhaled by the astronauts. However now, all the crew is wearing the Speedmaster x33, which has a sapphire crystal. Does anyone know why it's ok now or was this just an old wives tale for the reason for Hesalite?

Evitzee · Apr 4, 2026

Sixty years ago no one knew what effects shards of a shattered crystal would have on the delicate systems, so they were very conservative. Now it's not that big of a deal to have a sapphire crystal on a watch. Experience rules.

Duckie · Apr 4, 2026

Evitzee
Sixty years ago no one knew what effects shards of a shattered crystal would have on the delicate systems, so they were very conservative. Now it's not that big of a deal to have a sapphire crystal on a watch. Experience rules.

Let's not forget the potential for glass fragments to get into eyes or damage a suit or seal.
I did read of one instance where they spent a good number of hours vaccuming the entire interior of the craft to capture the pieces of glass that had been released after a glass cover on an instrument broke. I think it may have been a shuttle mission from memory.
With being time poor i expect it's also something they wouldn't necessarily be wanting to deal with. So there's that as well.

Experience will indeed show the folly of their ways, one way or another.

alam · Apr 4, 2026

Kmmdad57
I have heard so many times now that the original Moonwatch had to have a hesalite not sapphire crystal because if one breaks, it wouldn't be an issue of small fragments of sapphire floating around the spaceship that could get into components or be inhaled by the astronauts. However now, all the crew is wearing the Speedmaster x33, which has a sapphire crystal. Does anyone know why it's ok now or was was this just an old wives tale for the reason for Hesalite?

Not according to NASA specification requirements. It only stated shatterproof.

5. The chronograph must be shockproof, waterproof, and anti-magnetic. In addition, the face cover must be shatterproof.

frank.mooney@yah · Apr 4, 2026

I think shatterproof glass is an essential requirement for space flight . sapphire as any man caught out will know his wife will put hammer through his collection.

Donn Chambers · Apr 4, 2026

Probably not, but remember … the Speedmasters used in the Apollo missions were off the shelf watches and those watches only came with hesalite. In fact, most sports watches (even those by Omega, Rolex, Heuer, etc) were only offered with acrylic crystals.

It would have been difficult to find a chronograph with a sapphire crystal in the 1960s.

reggie_v · Apr 4, 2026

I’d have guessed the actual x33s submitted to nasa may have been modified to use hesalite still

Meme-Dweller · Apr 4, 2026

The Moonwatch is flight-qualified for all manned space missions. The X-33 is only qualified for wear inside a spacecraft (IVA).

Apparently, the fear isn't the crystal shattering from an astronaut hitting something with his/her wrist, but rather, shattering from sudden temperature shifts in the vacuum of space.

ErichPryde · Apr 4, 2026

Meme-Dweller
Apparently, the fear isn't the crystal shattering from an astronaut hitting something with his/her wrist, but rather, shattering from sudden temperature shifts in the vacuum of space.

I think there was also a lot of legitimate concern around an electronic watch failing in space dur to temperature changes. The X33 is designed to avoid this and has some internal heating system iirc.

padders · Apr 4, 2026

reggie_v
I’d have guessed the actual x33s submitted to nasa may have been modified to use hesalite still

You’d have guessed wrong.

padders · Apr 4, 2026

The Speedmaster was selected in an era when sapphire crystals were incredibly rare and certainly not seen in the size needed for a 41mm chrono. The idea of one didn’t even enter the minds of the NASA selection panel.

The X-33 is prob a better watch than the speedy for space travel today but try owning one. They chew through batteries every 2-3 years and changing them is not DIY. It truly is a tool watch in the military sense ie very expensive to buy and run compared to, say, a G-Shock or Apple watch. Space or perhaps an Americas cup yacht is the only place where an X-33 is the right choice. Otherwise anything else is a better one.

Dan S · Apr 4, 2026

Wouldn't mineral glass have been the main option to acrylic? I don't think that sapphire was really a plausible option at the time.

ErichPryde · Apr 4, 2026

Dan S
Wouldn't mineral glass have been the main option to acrylic? I don't think that sapphire was really a plausible option at the time.

I think mineral glass/rock crystal had already been pretty consistently replaced with acrylics after/during World War II (since it can shatter) for serious use. I think it just followed that Omega used acrylic for the same reason that acrylic had replaced previous minerals in hard environs.

The idea that it is better than specifically Sapphire though, is definitely a modern misconception of what was actually being primarily used in the mid 20th century.

Vinz Clortho · Apr 4, 2026

padders
The X-33 is prob a better watch than the speedy for space travel today but try owning one. They chew through batteries every 2-3 years and changing them is not DIY. It truly is a tool watch in the military sense ie very expensive to buy and run compared to, say, a G-Shock or Apple watch. Space or perhaps an Americas cup yacht is the only place where an X-33 is the right choice. Otherwise anything else is a better one.

This is another reason I've been hesitant of grabbing a X33, the battery life issue. But will probably breakdown at some point if the right deal comes along.

Donerix · Apr 4, 2026

I can say from personal experience that fragments of sapphire glass are no joke. I still have some pieces lodged under my thumbnail when that damn Spiralwinder caseback shattered 6 weeks ago. Now imagine no gravity and that stuff flying around the cabin ....

pascs · Apr 4, 2026

The Gen1 X33 is pretty straight forward to change the battery, I've changed mine a few times and I think its only been to Omega once for service. I've been wearing it the last few days 😎

JimInOz · Apr 4, 2026

pascs
The Gen1 X33 is pretty straight forward to change the battery, I've changed mine a few times and I think its only been to Omega once for service. I've been wearing it the last few days 😎

Ditto, I've changed my batteries a few times.

gbesq · Apr 4, 2026

NASA just knows that hesalite looks much cooler than sapphire. ::facepalm1::

Kmmdad57 · Apr 5, 2026

D Duckie
Let's not forget the potential for glass fragments to get into eyes or damage a suit or seal.
I did read of one instance where they spent a good number of hours vaccuming the entire interior of the craft to capture the pieces of glass that had been released after a glass cover on an instrument broke. I think it may have been a shuttle mission from memory.
With being time poor i expect it's also something they wouldn't necessarily be wanting to deal with. So there's that as well.

Experience will indeed show the folly of their ways, one way or another.

But they use the x33 now. It has sapphire

Kmmdad57 · Apr 5, 2026

alam
Not according to NASA specification requirements. It only stated shatterproof.

5. The chronograph must be shockproof, waterproof, and anti-magnetic. In addition, the face cover must be shatterproof.
[/QUOT sapphire

alam
Not according to NASA specification requirements. It only stated shatterproof.

5. The chronograph must be shockproof, waterproof, and anti-magnetic. In addition, the face cover must be shatterproof.

But the x33 will shatter. I don't get it.

Did the Moonwatch need hesalite?

Kmmdad57

Evitzee

Duckie

alam

frank.mooney@yah

Donn Chambers

reggie_v

Meme-Dweller

ErichPryde

padders

padders

Dan S

ErichPryde

Vinz Clortho

Donerix

pascs

JimInOz

gbesq

Kmmdad57

Kmmdad57

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