Since 2016, SpaceX has been developing experimental techniques to recover payload fairings after launch. Payload fairings are designed to protect the launch vehicle payload from atmospheric pressure, acoustic effects and aerodynamic heating during launch. Once free of Earth's atmosphere these effects are no longer experienced so the fairing is jettisoned, splitting into 2 halves and falling back to Earth.
Each fairing half costs around $3 million dollars to manufacture and after jettisoning, it falls back to earth and is lost. Because of the manufacturing expense, SpaceX has experimented with ways to recover and re-use fairings to save money and bring down launch costs, just like they do with their Falcon 9 boosters.
The recovery method eventually chosen by SpaceX was to equip fairings with thrusters and a steerable parafoil to control and slow the descent after jettison. A ship, equipped with a sizeable net, would then attempt to position itself underneath the falling fairing and catch it before it hits the ocean surface. This process is best shown in the below video by u/KerbalEssences on Reddit.
On early attempts, SpaceX did not commit to using a ship to try and catch fairings. To test, adapt and improve the parafoil guidance system, different ships were sent downrange to monitor the success of the procedure and then, if possible, haul the fairings from the water and bring them back to land for analysis. SpaceX started doing this in 2016 using a ship by the name of GO Searcher.
GO Searcher was originally used for fairing recovery operations. The ship was sent out multiple times to observe the parafoil-controlled descent of the fairing and then attempt to recover them from the ocean surface
In 2017 the ship was re-assigned to Crew Dragon recovery but saw fairing recovery action again, being sent out twice more in 2019 to recover fairings whilst GO Ms. Tree was modified/repaired.
Early recovery attempts by GO Searcher did not prove very successful. It took 4 missions for the ship to manage to return anything to land. During the 4th attempt (SES-10) the ship recovered 2 sizeable chunks of fairing debris but nothing more, suggesting a failure with the parafoil or rapid destruction once the fairing was floating on the ocean surface.
In October 2017 a new ship named Mr. Steven arrived at Port Canaveral. Mr. Steven was the ship that would ultimately be fitted with a net and attempt to catch the payload fairings. Before any modifications started, the ship was sent out during the KoreaSat-5A mission to perform GO Searcher's role of observing the fairing's descent and then recover from the water. The ship returned to Port Canaveral with a largely intact fairing half - the first major success of the program. Shortly after this success, SpaceX moved Mr. Steven to the West Coast of the United States to develop the catching system closer to their Hawthorne headquarters.
Fairing Recovery Attempts
SpaceX has been sending ships downrange since 2016 to attempt recovery of payload fairings, with varying success. We've collated a list of all these attempts and their outcomes.
With Mr. Steven now on the West Coast, and with GO Searcher now re-assigned to Crew Dragon recovery, a 3rd ship was needed to continue recovery operations on the east coast. GO Pursuit was brought in to perform the same role as GO Searcher did. Throughout the first half of 2018, GO Pursuit was sent out 4 times, recovering 2 halves.
Mr. Steven was first fitted with arms and a net back in December 2017 in the Port of Los Angeles. Mr. Steven's first attempt at catching a fairing half was during the PAZ mission in February 2018 but was unsuccessful. After little success, the vessel's net and arm structure were significantly upgraded to be 4x larger, totaling an estimated 3.600 square meters. Mr. Steven continued to make attempts at catching fairings throughout 2018 with no success. The ship was, however, frequently able to recover them from the water shortly after. For the full story of Mr. Steven's mission history take a look at the dedicated page here.
GO Ms. Tree (Previously Mr. Steven)
GO Ms. Tree is a fast, highly maneuverable vessel that was chartered by SpaceX in 2017 to support their fairing recovery program. The ship has been heavily modified by SpaceX so that it now has a large net structure designed to catch fairing halves as they descend.
GO Ms. Tree has made a number of catching attempts during West Coast SpaceX missions throughout 2018. The ship was repositioned to the East Coast in early 2019 to continue development of the catching program.
Mr. Steven was renamed GO Ms. Tree in June 2019.
In response to the catching attempt failure during the Iridium-5 mission, Elon Musk announced that helicopter drop-tests were being prepared to help improve the parafoil system and as practice for Mr. Steven's crew. The announcement was made in March 2018 with the test conducted in June. Mr. Steven continued these tests throughout the second half of 2018.
For the test, a fairing half was placed onto a barge and towed out to sea. A Black Hawk helicopter would then pick up the fairing and ascend with it up to ~3.25km in altitude before releasing it. Mr. Steven, waiting below, would then follow the fairing and attempt to catch it as it descended downwards. Mr. Steven was reportedly not successful during any of the tests but came very close. SpaceX released two videos of the process on Twitter.
Mr Steven was moved to the East Coast at the start of 2019. The first catch attempt out of Cape Canaveral had to be unexpectedly aborted in the hours before the mission. Right before the Nusantara Satu launch the vessel stopped and turned around. Arriving back in Port Canaveral 24 hours later, the ship has been visibly damaged - two arms and the net were completely missing, one of the antenna radomes and the boarding bridge had also been damaged and were covered up.
The remains of the catching structure were quickly removed by SpaceX technicians and the vessel was left without its catching system for 3 months whilst a replacement was engineered. Finally, in May 2019 the catching system was re-instated and thoroughly tested both offshore and during net load tests in Port.
Mr. Steven was renamed GO Ms. Tree in June 2019 because of a suspected ownership change. Read more about it here.
GO Ms. Tree successfully caught a fairing half for the first time during the STP-2 mission on June 25th, 2019. The fairing recovery zone for the mission was at a record distance of 1350km downrange. The weather was excellent and the ship was successful in catching a fairing half for the first time. The fairing half was lowered from the net and delivered back to Port Canaveral for processing and potential re-use in the future.