Successful drone ship landing proves elusive for SpaceX
Photo Credit: SpaceX
While Sunday’s launch of the Jason-3 satellite from Vandenberg Air Force Base was successful, launch provider SpaceX’s experimental first stage booster landing attempt was thwarted by a failed landing leg. To date, SpaceX has made three attempts to land the first stage of a Falcon 9 on a drone ship, none of which have been successful (although each subsequent attempt has inched closer to achieving this goal).
In December 2015, a Falcon 9 first stage made a successful ground landing at Cape Canaveral Air Force Station’s Landing Zone 1. In fact, the flight was a massive success. During that flight, the Falcon 9 carried out its first flight since the June 28, 2015, loss of the prior Falcon 9. The rocket successfully ferried some 11 Orbcomm OG2 satellites to orbit – and then announced the opening of the reusable rocket era with powerful sonic booms – before sticking a perfect landing in the middle of an “X” painted at the landing site. This feat demonstrated that not only could it be done but also could be done with extreme precision.
Mastering ocean landings will be important for SpaceX’s goal of developing a reusable launch vehicle. For mission profiles that require a higher velocity at stage separation, the fuel remaining in the first stage booster would not be enough to bring it back to the launch site. This is why SpaceX is continuing to attempt landings on its Autonomous Spaceport Drone Ships (ASDS).
While SpaceX has repeatedly demonstrated the ability to fly a booster back to a designated target and perform a controlled descent, none of the drone ship landing attempts have been successful. Landing on the deck of a ship is more difficult than a ground landing because the pitching sea reduces stability. This was noted by SpaceX’s CEO and Founder – Elon Musk.
SpaceX infographic showing flight profile for Falcon 9 launch with first stage return and landing on Autonomous Spaceport Drone Ship (ASDS). (Click to enlarge.) Image Credit: SpaceX
“Definitely harder to land on a ship. Similar to an aircraft carrier vs land: much smaller target area, that’s also translating & rotating,” Musk noted in a tweet.
In the end, this might be one issue that SpaceX may not be able to adjust for. If, as Musk himself noted, these efforts are as challenging as carrier landings, the uncrewed Falcon 9 and ASDS would either need extremely calm seas or the precision of a military pilot with years of experience. Having said that, many within the space community scoffed at the idea of a rocket’s first stage landing back near the launch site.
SpaceX made their first attempt to land a Falcon 9 first stage on the drone ship Just Read the Instructions on January 10, 2015, during the launch of a Dragon cargo spacecraft for the fifth operational Commercial Resupply (CRS-5) mission to the International Space Station (ISS). While the first stage made it to the drone ship, it prematurely ran out of the hydraulic fluid that is used to steer the grid fins that help to control the rocket’s descent, resulting in a hard landing.
The second attempt was made on April 14, 2015, during the subsequent CRS-6 launch. The first stage landed on the deck of the drone ship with too much lateral velocity and toppled over, resulting in an explosion. This was due to a stuck bipropellant valve that prevented control system from reacting quickly enough for a successful landing.
Sunday’s third attempt came the closest to being successful. The first stage made a soft landing on the deck of Just Follow the Instructions, but the lockout collet on one of the four landing legs didn’t latch, causing the rocket to tip over. In an Instagram video post, Elon Musk stated that the root cause may have been ice buildup due to condensation from heavy fog at liftoff.
Future landing attempts will be made using the upgraded “full-thrust” Falcon 9 configuration that made the successful ground landing in December. Musk is optimistic that there will be a successful landing soon, but there may also be some more rapid unscheduled disassemblies (RUDs) still to come.
“My best guess for 2016: ∼70% landing success rate (so still a few more RUDs to go), then hopefully improving to ∼90% in 2017,” Musk said in a tweet.
Video courtesy of SpaceX
Jim Sharkey
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.
Greetings Mr. Sharkey,
I appreciated your article regarding the result of the 3rd SpaceX first stage landing attempt at sea. It was focused on facts with a little ‘rah rah’ thrown in. That is what makes for a good article.
I wanted to point out a slight discrepancy, if I may be excused for doing so. You implied that Mr. Musk’s comment comparing the sea landing to a carrier landing for a plane versus on-land landing. You did not include his follow-on tweet that made it clear that although it *is* harder to land on the sea than land, this RUD (fun acronym that) was not due to the complexities of a sea landing and had everything to do with a fault in the design of the landing strut – it was unable to lock in place due to possible ice buildup. Unfortunately you left that out and suggested that SpaceX may not be able to correct for this, which is the opposite of what we already know. This landing (sans subsequent landing gear failure) was a complete vindication of the landing-at-sea approach that SpaceX is following.
Thanks for listening,
John H.
Actually, I was just thinking Jim might have hit a critical problem here. The first stage of the F9 is tall and anyone who’s been 2-300 miles out in the ocean knows how incredibly rough it can get. While SpaceX might nail the landing they might not recover the stage all that often because the booster might topple over anyway irregardless of whether-or-not they get the landing perfect. It’s important to consider all of the factors at play and keep an open mind.
That is easy enough to fix. If the return is to land–as it will be most of the time–heavy seas will not be an issue. If the return is to sea, then the roughness of the seas at the drone ship location become a launch factor: you do not launch if the seas are too rough.
BTW, SpaceX has already said that all future Falcon-9 first stages have a heavier latch mechanism already designed in based on what they learned from earlier missions. That may not be the complete solution, but SpaceX was already taking a close look at this latch.
Bear in mind also that the centre-of-mass of an empty first stage is very low down, as the engines make up the majority of the mass. so while it looks ‘precarious’, in actual fact it will be a lot more stable
All,
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I wonder if modifications to the landing gear could help. Gear that touches sooner and absorbs more, could be made. Perhaps it could rebound intelligently.
Also, it’s possible to make the barge more stable with very deep structure to carry most of it’s weight below the level of the waves. It may wind up being more like a deep sea oil derrick than a traveling barge. But that could still work. Most shots from florida would come down in the same general area. It might not be able to be in the ideal spot, but could still be navigated to aerodynamically.