You do not have to look very hard to find another exciting success from SpaceX. It’s a company defined by big and bold moves, and when something goes right, they make sure you know about it. From the launch of a Tesla in deep space to the captivating test flights of their next-generation Starship spacecraft, the private company has turned high-stakes aviation research and development into a public event. A personality cult has developed around SpaceX’s strange CEO Elon Musk, and as long as he’s at the helm, we can expect bigger and brighter glasses as he directs the company towards his ultimate goal of putting humans on Mars.
Of course, things do not always go right for SpaceX. While setbacks are inevitable in space, the company has had a few particularly embarrassing failures that can be directly attributed to their rapid pace of development or even operational inexperience. A perfect example is the loss of the Israeli AMOS-6 satellite during a static launch of the Falcon 9 engines on the launch pad in 201
But sometimes the failure is not so much a technical problem as an inability of the company to achieve their own lofty goals. Occasionally, one of Musk’s big ideas ends up being too complex, dangerous, or expensive to put into practice. For example, despite having spent years and countless sums of time perfecting the technology involved, propulsion landings for the Crew Dragon were nixed before the idea could ever be fully tested. NASA was reportedly uncomfortable with what they saw as an unnecessary risk compared to the more traditional sea spray under parachutes; it would have been an impressive sight to be sure, but it did not provide a significant advantage over the simpler approach.
A similar fate befell SpaceX’s twin fairing recovery ships recently Mrs. Tree and Mrs. Chef, who quietly retired in April. These ships were designed to capture Falcon’s school bus size on payload as they drifted to the ground using massive nets suspended above their decks, but in the end the process proved more difficult than expected. More importantly, it was apparently not even necessary in the first place.
Credit where credit is due, both Mrs. Tree and Mrs. Chef successfully captured fairings during their time at SpaceX. The ships proved that the concept was viable, and on two missions in 2020 even managed to capture both mantle halves. But overall, their success rate was pretty poor. According to a figure from SpaceXFleet.com, of the 37 missions where one or both ships attempted to recover the frames, only a total of nine catches were successful. It’s already a pretty bad average, but when you realize that each mission actually has two fairings to catch, it’s creepy.
The low success rate is bad enough, but even when the ships actually nipped one of the fairings in the air, it did not always end well. During the Starlink mission on October 18, 2020, the live video feed is off Mrs. Tree briefly showed a cloak that ripped through the net and smashed down on the deck. With each casing half estimated to weigh approximately 950 kg, a lost break poses a clear danger to the crew and equipment on board the recovery vessel not to say anything about the casing itself. After all, the goal is to restore them intact so they can be used on a subsequent flight.
It may seem strange that SpaceX had so much trouble catching these relatively large and docile objects as they drifted to the surface beneath their parafoil, especially compared to the fire and rage from the Falcon 9’s first floor landing. Over the last three years, SpaceX has managed to maintain a success rate of around 90% for booster recovery at sea, and at least on the surface, it seems that both procedures are more alike than they are different.
But in the end, it’s a matter of command. The active grille fins and pressure vector functions in the Falcon 9 make it far more manoeuvrable on the descent than the steerable parafoils used by the hoods. Even with the recovery ship actively communicating with the fairing’s own aircraft electronics and trying to plan an intersection, a strong gust of wind at the wrong moment was all it took to knock them off course.
Make a splash
From the beginning, SpaceX believed that they would have to catch the robes with a net because it would damage them outside of economic repair to let them come in direct contact with salt water. While specific details are hard to come by in public, it is widely believed that the concern stems not so much from the electronics on board that could presumably be waterproof, but the unique construction of the frames themselves. Made of an aluminum honeycomb structure sandwiched between layers of composite material, water penetration can be a serious problem; as when salt water entered the structure of the cabinet itself, it may not have been possible to get it out quickly and economically.
But in light of a recovery program that apparently is not going anywhere, the engineers at SpaceX have apparently figured out a way to make it work. Close-ups of newly constructed jackets show that various vents and openings have been moved so that they will be higher from the surface of the water, and rumor has it that the internal sound-absorbing panels are now considered consumable and discarded after each mission rather than trying to wipe them out. What, if any, steps were taken to prevent water from seeping into the aluminum / composite construction of the cladding are currently unknown.
While the refurbishment process for these “wet” jackets is undoubtedly more expensive and time consuming than if they were trapped in the net, the difference is clearly not enough to justify the continued operation of Mrs. Tree and Mrs. Chef. Instead, the SpaceX Charter has it much larger Shelia Bordelon to take over as the primary fairing recovery vessel. The 78 m long ship is intended for underwater research and has wide open decks, a built-in crane and a Triton XLX remote controlled vehicle (ROV) that can dive down to 3,000 m (9,840 feet).
The integrated crane makes it easier to pull jackets out of the water and drop them on the quay, but otherwise this ship does not seem very suitable for the current task. First, its underwater features are completely wasted. But more importantly, the rapid launch cadence required by the Starlink missions means that the recovery vessel should ideally be able to hold four mantle halves before returning to port. So either it Shelia Bordelon will soon get some custom changes, or SpaceX will only use it temporarily until they can come up with a long-term solution.