It was the homecoming SpaceX predicted, but certainly not the one the company wanted following the SES-9 launch on Friday. In the YouTube video below, the automated spaceport drone ship “Of Course I Still Love You” is towed into Port Canaveral with only small tarp covering what presumably are the remains of the Falcon 9 first stage.
While the landing did not go well, it did serve to confirm the company’s ability to come astonishingly close to the very small speck at sea which is the ASDS even when “coming in hot” following a stage separation event taking place both higher and faster than on most launch profiles. The last published frames of the live feed video showed the incoming booster to appear to be within meters of its target, and possibly even closer.
There are several takeaways from SpaceX’s attempts to achieve first stage landings at this point. One is that it clearly can and will be accomplished, given that it already has been, if only for the briefest of moments. As part of the Jason-3 launch from Vandenberg, California in January, the last older series Falcon 9 V1.1 did manage to land on the West Coast ASDS “Just Read the Instructions” but failed to stick it when one of the carbon fiber landing legs gave way. Newer, Full Thrust Falcon 9’s, are equipped with strengthened legs and improved latching mechanisms.
The are two remaining elements necessary for regular success. One is partially controllable, the other isn’t. The first is sufficient remaining propellant for each of the three burns of the Merlin 1-D engines; the initial deceleration burn, the secondary targeting or return burn to put the stage on path to its target, and finally the all-important descent burn to slow the booster and bring it in upright with limited angular momentum. All three were available for the December 21st 2015 Orbcomm OG-2 mission which saw a historic landing not at sea, but instead back at Cape Canaveral. The OG-2 mission however, which was the first to utilize super-chilled propellant, was also very lightly loaded, something which will not be the norm, at least not for a while.
For the time being, most missions will require a decision as to whether to attempt a landing at sea, which would be aided by the presence of extra remaining propellant, or instead to attempt a more fuel intensive flyback to landing zones where the presence of a wide, stable concrete pad will be of little comfort if the fuel is exhausted in the final second.
The critical difference of course, is the weather, which proved to be a prohibiting factor on the first high speed return attempt, which took place on the DSCOVR mission to deep space. Ocean landings bring with them not only the unpredictable nature of the sea, which can range from vaguely concerning to absolutely terrifying, but also other more predictable issues such strong offshore trade winds and accelerated corrosion from salt spray. It will be interesting to observe on a case by case basis which way SpaceX leans when the payload mass and flight profile says both returns are possible.
Looking a bit further down the road, the calculus may shift somewhat once launches begin to take place from the commercial spaceport SpaceX is developing at Boca Chica, Texas. While the Gulf of Mexico, like any body of water, can become threatening under certain conditions, it is generally a much more placid place than either the Atlantic or the Pacific, and should be generally favorable to nautical landings.
The decision will get even more interesting with the debut of the Falcon Heavy and the eventual introduction of first stage re-use. Assuming the latter, FH launches are likely to offer highly favorable odds for returning and re-flying the twin outboard boosters. In certain circumstances, such as in the recent SES-9 flight where the spacecraft’s mass and destination pushed the Falcon 9’s performance to its limit, there may be a decision to be made between foregoing any hope of recovery on a single core rocket, versus the higher cost of a Falcon Heavy launch where all three cores are returned, even if the core segment is recovered at sea.