This is what a "max damaged" rocket looks like. Would you fly on it? Image source: SpaceX.

Give props to Elon Musk: In back-to-back space launches to GTO -- geostationary transfer orbit, roughly 10 times the height of a low-earth-orbit, or LEO, launch -- the SpaceX CEO has his sent rockets hurtling toward space, then turned them around for high-speed, high-friction atmospheric reentries, and landed them successfully aboard drone ships floating at sea.

Counting SpaceX's most recent rocket landing, which took place on the evening of May 27, SpaceX has now landed four rockets safely back on Earth -- one on land, one at sea after an LEO mission, and two at sea following GTO missions. This is a feat that no other company, or country, had ever accomplished before.

Yet as the successes mount up, we're already beginning to see a potential flaw in the program.

The after-action reports

Following the successful landing of its first GTO rocket on May 6, Musk tweeted out the following damage assessment: "Most recent rocket took max damage, due to v high entry velocity. Will be our life leader for ground tests to confirm others are good."

Three weeks later, Musk made a similar statement regarding the May 27 GTO mission: "Rocket landing speed was close to design max & used up contingency crush core."

Max damage? Crushed cores? These certainly sound like scary things to happen to a rocket ship. But what do they really mean? More important, what do they mean for folks who would like to invest in SpaceX in the future, or who may unknowingly have already invested in SpaceX today, through ownership of Alphabet (NASDAQ:GOOG) (NASDAQ:GOOGL) stock?

For the benefit of those who may not be aware, Alphabet, the company formerly known as Google, owns a 7.5% stake in SpaceX. It's not a large part of Alphabet's business by any means, comprising less than 0.2% of Alphabet's $505 billion market capitalization. But for investors looking for any way at all to participate in SpaceX's success, at a time when the company remains privately owned, Alphabet is really the only way in at this time.

"Max damage"

Seeking answers, I reached out to SpaceX with these questions. Here's what I've learned:

When Musk refers to "max damage," the "design max" of his Falcon 9 rockets, and calls them his "life leaders," he's basically saying that the missions these two rockets performed are at the upper end of SpaceX's capability today. They put satellites up about as high as SpaceX can currently go, and after delivering their payloads, they returned to Earth about as hot and fast as SpaceX thinks it's possible for them to come back and still land safely.

SpaceX's May 6 rocket, for example, hit Earth's atmosphere traveling at Mach 5.7 (6,300 km/hr) and experienced "peak deceleration" of 6.6 times Earth's gravity -- that's 6.6 Gs -- as it slowed down for its sea landing. Upon landing, the Falcon's retro rockets fire to set it down as gently as possibly, but even so, the landings compress the Falcon's "contingency crush core," an aluminum honeycomb material designed to absorb the energy of the rocket's impact.

Aerospace aluminum honeycomb shock absorber. Image source: Steve Jurvetson via Wikimedia Commons.

Again, the word "crush" seems to conflict with the concept of a "reusable" rocket. If SpaceX's Falcons are getting "crushed" on impact, this would seem to raise the question of how reusable they really are.

The important thing to note here, though, is that the "max damage" that SpaceX's Falcon 9s are incurring is damage they're designed to absorb. The "crush core" gets crushed to prevent the rest of the rocket from incurring structural damage. The core can then be replaced as part of the rocket's refurbishment for reuse -- and the rocket may still be reusable.

What it means to SpaceX -- and its investors

The upshot of all this, then, is that four Falcon 9 rockets have now landed safely, albeit not unharmed. Recovered and brought back to the SpaceX mother ship, these rockets can now be examined to determine how much damage was done, to establish an upper limit on how much punishment the Falcon 9 can take, and to plan improvements that might strengthen Falcon 9 to mitigate such damage in future launches.

What would be really interesting to see, though -- and what we have not yet seen -- is whether SpaceX can, in fact, recondition and refly one of these max-damaged rockets. That's the test that will prove that SpaceX's reusable rockets are not just reusable in name only, but in actual fact, and thus actually capable of cutting the cost of SpaceX's satellite launches by 30%.

For more on that score, tune back in to tomorrow.

Unless it starts actually reusing them soon, SpaceX is going to need to build bunk beds to house its growing supply of reusable but un-reused rockets. Image source: SpaceX.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.