When Little Joey Went Kablooie!

SpaceX's successful In-Flight Abort test of its Crew Dragon last week was a huge milestone in returning human spaceflight to the US, everyone at the office was pretty pumped (here's the official SpaceX press release on the demonstration; unfortunately as a SpaceX employee I'm not allowed to say much more than that). But understandably, a lot of lay people who don't regularly follow spaceflight were confused - how could the mission be successful, we literally watched a Falcon 9 booster explode before my very eyes!

Falcon 9 intentionally exploding after Crew Dragon separation (Credit: SpaceX)

Since SpaceX won the NASA contract to launch US astronauts to the International Space Station, they've gone through the lengthy process of "human-rating" their existing Falcon 9 rocket and Dragon spacecraft. Among other modifications, this includes installing an abort system that can safely eject astronauts in the event of booster failure, because unlike regular cargo, actual lives are at stake. Since the advent of human spaceflight, all manned rockets have had some form of abort system in place - notice how in the below image, the manned versions of the two rockets have the pointy spike at the top, unlike the unmanned versions. That pointy spike is the launch escape tower; if the rocket were to fail, powerful thrusters at the top that would automatically ignite, detaching the crew compartment from the exploding rocket and pulling it to safety

Different rockets, different countries, different eras - same essential capability needed for a human-rated rocket!

However, while the designs are broadly similar, some in-flight abort tests have been far more exciting than others! As the Apollo Program was ramping into full swing, NASA conducted numerous in-flight abort tests of the Apollo Command Module that would carry astronauts to the moon. But given how enormously expensive the Saturn V rocket was (plus the fact it wasn't ready yet in 1965), they weren't about to blow up an entire rocket stack just for a single test; instead, they attached dummy Command Modules to a mini rocket called Little Joe II that was designed to shut down mid-flight and give the launch escape tower a chance to prove its worth!

Little Joe II on the launchpad | Size comparison versus the Saturn V, as well as the smaller Saturn I and IB

The 4th flight of Little Joe II was the most spectacular - when it lifted off on May 19, 1965, it turned out someone had accidentally made a real mistake on the rocket's roll gyroscope, causing it to spin wildly out of control as it ascended into the sky. The rapid rotation resulted in catastrophic aerodynamic stress that disintegrated the rocket, turning what was supposed to be a simulated rocket failure into an actual explosion. Thankfully, the launch escape tower worked flawlessly, detecting that an actual booster failure was occurring and automatically yanking the dummy spacecraft to safety. For the engineers, it was the perfect test flight, the epitome of the phrase, "task failed successfully"! 

It's not an explosion, it's just a "rapid unscheduled disassembly!" | Original video here

While launch escape towers mounted to the top of manned rockets are the most common abort system, that's not to say others haven't been used. Believe it or not, the Titan II rocket used for the Gemini Program (the predecessor to Apollo) had ejection seats, similar to fighter aircraft! Thank goodness no Gemini flight had to be aborted mid-flight; many engineers suspected the design was inherently flawed, as firing the pyrotechnics of an ejection seat in the pressurized oxygen of the spacecraft likely would've resulted in a massive fireball that would've cooked the astronauts

No thanks! I'll take my chances with the exploding rocket! | Credit: The Everyday Astronaut (full video here)

And due to its unconventional stack with its huge solid rocket boosters and external fuel tank, the Space Shuttle couldn't be easily aborted after launch. NASA developed numerous contingency plans that could be attempted at various altitudes, but they weren't very safe or reliable. For example, Challenger exploded in 1986 at an altitude where no abort option was feasible, a major criticism of the design. So I'm glad we're sticking with launch escape towers going forward!


  1. Great article!

    I believe it was the Gemini capsule that contained the ejector seats - the Titan II booster had no IFA systems.

    1. Agreed! Look up the Gemini 6 mission - the first launch attempt got shut down right on the pad, and thankfully Commander Wally Schirra had both the right intuition and the steely nerves to know he didn't need to activate the ejection seats, otherwise he and Tom Stafford likely would've been severely injured