Following the picture-perfect launch of GovSat-1 on Wednesday afternoon, SpaceX CEO Elon Musk took to Twitter with an extremely unusual bit of news. After separating from the second stage, events relating to Falcon 9’s first stage recovery operations were heard live in the background of SpaceX’s live coverage, leading to some additional intrigue around an already odd situation.
B1032, a flight-proven (reused) booster tasked with launching GovSat-1 on its second mission, was seen with landing legs and grid fins on its sooty exterior – a confusing appearance due to SpaceX’s statement that the core would be expended into the ocean after launch. Thankfully, Elon Musk’s tweets provide at least the beginning of an answer for the several oddities.
This rocket was meant to test very high retrothrust landing in water so it didn’t hurt the droneship, but amazingly it has survived. We will try to tow it back to shore. pic.twitter.com/hipmgdnq16
— Elon Musk (@elonmusk) January 31, 2018
As stated above, GovSat-1’s Falcon 9 booster (1032) was apparently being used to test an exceptionally aggressive landing burn in lieu of a drone ship beneath it. The lack of drone ship begins to make more sense with the added knowledge that 1032 was testing experimental landing procedures: in the relatively likely eventuality that something went wrong, the massive booster would have likely impacted Of Course I Still Love You at an extremely high velocity. Similar impacts have occurred before as SpaceX gradually perfected the new technologies and operational knowledge necessary to recover orbital-class rockets, but a basic understanding of rocketry implies that 1032’s OCISLY impact would have been uniquely destructive, likely taking the ship out of action for at least several weeks of repairs.
This would pose an inherent problem for the imminent launch of Falcon Heavy, with the center of three first stages currently scheduled to attempt a landing aboard the very same drone ship in less than a week. Under optimum conditions (sans huge explosions and general destruction), OCISLY and its entourage of support vessels simply could not complete the journey back to Port Canaveral and the subsequent return to sea that would have been necessary to recovery both GovSat-1 and Falcon Heavy’s center core. Add in the potential need for repairs and expending GovSat-1 was a no-brainer for the launch company: Falcon Heavy’s center core could easily see at least one additional launch after it is recovered, whereas the twice-used 1032 effectively reached the end of its useful life after it separated from the second stage and GovSat payload earlier today.
As a result, SpaceX appears to have continued a trend of exploiting flight test opportunities to the greatest extent practicable by tasking B1032 with an experimental landing attempt. More specifically, Elon quickly added that the landing burn attempted by 1032 involved the ignition of three of the booster’s nine Merlin 1D engines during landing, whereas all SpaceX landings up to this point have occurred with a single Merlin 1D ignition. While the company already routinely utilizes three engines during some boostback and reentry burns, landing burns have always featured a single engine. However, by using three engines, it is entirely possible that SpaceX hopes to eventually move towards even more aggressive landing burns. While the obvious downsides likely include difficulty maintaining control and increased stresses on the booster, the benefits are also pretty inherent. By using more engines, the length of the landing burn could be drastically shortened, resulting in far more efficient propellant usage by minimizing losses to gravity (every second the rocket is trying to go upwards is a second fighting against Earth’s gravity, which pulls the rocket down at ~9.8 meters/second squared).
Incredibly, the booster somehow managed to pull off that three engine landing burn with some success, made apparent by the fact that it is intact and floating in the Atlantic, with some hope of being towed back to land. This is almost certainly the first time SpaceX has ever successfully landed a booster in the ocean without a subsequent breakup, an incredible achievement for a rocket that likely experienced exceptional stresses during reentry and landing. Time will tell how this impacts SpaceX’s future recovery efforts, but it is certainly promising as a method of extracting just a little extra performance from reusable Falcon 9s. In other words, future Falcon 9 missions might be able to carry heavier payloads into higher orbits while still being able to land at sea or even on land. Exciting times!