An autonomous spaceport drone ship (ASDS) is a modified ocean-going barge developed by SpaceX and equipped with propulsion systems to maintain precise position and a large landing platform.They were developed to recover the first stage (also called the booster) of its launch vehicles. By recovering and reusing these boosters, SpaceX has significantly reduced the cost of space launch.
SpaceX operates three ASDS: Just Read the Instructions (II) (JRTI), A Shortfall of Gravitas (ASOG), and Of Course I Still Love You (OCISLY). JRTI and ASOG operate from Port Canaveral supporting launches from Kennedy Space Center and Cape Canaveral Space Force Station landing in the Atlantic Ocean, while OCISLY operates from the Port of Long Beach supporting launches from Vandenberg Space Force Base landing in the Pacific Ocean.
Depending on mission requirements, SpaceX can return the booster to the launch site for a ground landing, land the booster at sea on an ASDS, or discard it. While a ground landing is the least expensive option, it requires the most fuel and thus reduces payload capacity. Sea landings offer a balance of cost and performance, making them the most common choice, used on approximately three-quarters of missions.
History
Falcon 9 v1.1
In 2009, SpaceX CEO Elon Musk articulated ambitions for "creating a paradigm shift in the traditional approach for reusing rocket hardware".In October 2014, SpaceX announced that they had contracted with a Louisianashipyard to build a floating landing platform for reusableorbitallaunch vehicles.Early information indicated that the platform would carry an approximately 90 x landing pad and would be capable of precision positioning so that the platform could hold its position for launch vehicle landing.[1][2] On 22 November 2014, Musk released a photograph of the "autonomous spaceport drone ship" along with additional details of its construction and size.
As of December 2014, the first drone ship used, the McDonough Marine Service's Marmac 300 barge, was based in Jacksonville, Florida, at the northern tip of the JAXPORT Cruise Terminal, where SpaceX built a stand to secure the Falcon stage during post-landing operations. The stand consisted of four 6800 kg, 270 cm tall and 244.5 cm wide pedestal structures bolted to a concrete base. A mobile crane would have lifted the stage from the ship and placed it on the stand. Tasks such as removing or folding back the landing legs prior to placing the stage in a horizontal position for trucking would have been undertaken while the booster was on the stand.[3]
The ASDS landing location for the first landing test was in the Atlantic approximately 320 km northeast of the launch location at Cape Canaveral, and 266 km southeast of Charleston, South Carolina.[4][5]
On 23 January 2015, during repairs to the ship following the unsuccessful first test, Musk announced that the ship was to be named Just Read the Instructions,[6] with a sister ship planned for West Coast launches to be named Of Course I Still Love You (OCISLY).[7] On 29 January 2015, SpaceX released a manipulated photo of the ship with the name illustrating how it would look once painted.[8]
The first Just Read the Instructions was retired in May 2015 after approximately six months of service in the Atlantic Ocean, and its duties were assumed by Of Course I Still Love You.The former ASDS was modified by removing the wing extensions that had extended the barge surface and the equipment (thrusters, cameras, and communications gear) that had been added to refit it as an ASDS; these items were saved for future reuse.[9]
In 2018, Elon Musk announced plans for an additional barge, A Shortfall of Gravitas (ASOG), to support East Coast operations[10] but the build of the droneship was delayed, and instead JRTI was moved to the East Coast and began operations in June 2020. ASOG was completed in July 2021.
By June 2020, SpaceX had received the ability to use "its own private Automatic Identification System (AIS) aids to navigation (ATON) to mark the temporary exclusion areas it uses during rocket launches [from] Cape Canaveral, Florida", the first such use of dynamic restricted area ever approved by the U.S. Coast Guard.[11]
Fleet
Just Read the Instructions (I)
SpaceX's first ASDS was named Just Read the Instructions (JRTI). Converted from the existing Marmac 300 barge, JRTI served as a testbed for just two landing attempts, SpaceX CRS-5 and SpaceX CRS-6, the latter of which ended with the booster toppling over and exploding, damaging JRTI beyond repair on 14 April 2015.[12]
Of Course I Still Love You
SpaceX's second ASDS, Of Course I Still Love You (OCISLY) was constructed in a Louisiana shipyard beginning in early 2015 on the Marmac 304 hull.[7] While the dimensions of the ship are nearly identical to the original JRTI, OCISLY incorporated improvements including a steel blast wall. Initially intended for West Coast operations, OCISLY's role shifted after the loss of the original JRTI in April 2015. The ship entered service in late June 2015, based in Jacksonville, Florida, before relocating to Port Canaveral later that year.
OCISLY achieved a historic first on April 8, 2016, successfully landing the first stage of the Dragon SpaceX CRS-8 mission.[13] Despite sustaining damage during the Falcon Heavy Test Flight in February 2018, the ship was repaired and continued operations.[14] Another notable moment came on May 30, 2020, when OCISLY captured the first stage of the Crew Dragon Demo-2 mission, marking the return of human spaceflight from U.S. soil.[15][16]
In 2021, OCISLY was relocated to the Port of Long Beach to support West Coast launches from Vandenberg.[17][18][19][20]
Just Read the Instructions (II)
The third ASDS barge was named Just Read The Instructions, using the Marmac 303 barge hull. It was converted during 2015 in a Louisiana shipyard. When the refit as an ASDS was complete, the barge transited the Panama Canal in June 2015, carrying its wing extensions (the same ones originally built for the first Just Read The Instructions on the Marmac 300) as cargo on the deck because the ASDS, when complete, would be too wide to pass through the canal.[9] The ship underwent a major refit in September 2019 to May 2020, initially in Louisiana, and finishing at Port Canaveral, including four new, much larger, positioning thrusters.
The home port for the Marmac 303 was initially the Port of Los Angeles (until in August 2019) at the Altana Sea marine research and business campus in San Pedro, California's outer harbor.[21] The landing platform and tender vessels began docking there in July 2015 in advance of the main construction of the AltaSea facilities.[22][23]
SpaceX announced that the Marmac 303 would be the second ASDS to be named Just Read the Instructions in January 2016, shortly before its first use as a landing platform for
A Shortfall of Gravitas
A fourth ASDS, A Shortfall of Gravitas (ASOG), was announced in February 2018 and was originally planned to enter service in mid-2019.[30][31] It was made by modifying Marmac 302. In October 2020, Elon Musk re-affirmed plans to build a ship of this name.[32] In January 2021, Marmac 302 was spotted at Bollinger Fourchon site.[33] On 6 April 2021, NASASpaceFlight.com spotted the Octagrabber presumed to be for A Shortfall of Gravitas at the Cidco Road facility in Cocoa Beach, Florida.It may have originated as an upgraded Octagrabber for Just Read The Instructions.[34] By mid April 2021, Marmac 302 had scaffolding to prepare for construction, which was confirmed on 9 May 2021.[35]
Characteristics
The ASDS are autonomous vessels capable of precision positioning, originally stated to be within 3 m even under storm conditions,[44] using GPS position information[45] and four diesel-poweredazimuth thrusters.[46] In addition to the autonomous operating mode, the ships may also be telerobotically controlled.[4]
The azimuth thrusters are hydraulic propulsion outdrive units with modular diesel-hydraulic-drive power units manufactured by Thrustmaster, a marine equipment manufacturer in Texas.The returning first stage must not only land within the confines of the deck surface, but must also deal with ocean swells and GPS errors.
SpaceX equips the ships with a variety of sensor and measurement technology to gather data on the booster returns and landing attempts, including commercial off the shelfGoPro cameras.[47]
At the center of the ASDS landing pads is a circle that encloses the SpaceX stylized "X" in an X-marks-the-spot landing point.[48]
Names
The ASDS have names that are the same as or similar to[49]spaceships that appear in the Culture series of science fiction novels by Iain M. Banks.[37][50]
Just Read the Instructions (Marmac 300)
The landing platform of the upper deck of the first barge named Just Read the Instructions was 170 x, while the span of the Falcon 9 v1.1landing legs was 60 ft.[51][52]
Operation
A tug is used to bring the ASDS to its oceanic position, and a support ship stands by some distance away from the unmanned ASDS.[61] Following landing, technicians and engineers typically board the landing platform and secure the rocket's landing legs to lock the vehicle in place for transport back to port.[4] The first stage is secured to the deck of the drone ship with steel hold-downs welded on to the feet of the landing legs.[62] In June 2017, OCISLY started being deployed with a robot that drives under the rocket and grabs onto the hold-down clamps located on the outside of the Falcon 9's structure after landing.[63] The robot is officially called the "octagrabber".[64]
Vessel missions
The first flight test was 10 January 2015,[65] when SpaceX conducted a controlled-descentflight test to land the first stage of Falcon 9 Flight 14 after it helped to loft a contracted payload into Earth orbit.[1][2] Before the first landing attempt, SpaceX estimated that the likelihood of a successful landing on the platform would be 50% or less.[51][2] The landings went from being landing tests to become routine parts of missions.
28.Just Read The Instructions arrives in @PortCanaveral! We now have 2 East Coast droneships! You can see lots of stuff on the deck, including 6 new massive thrusters for station keeping. 10 December 2019, retrieved 14 January 2020^
67.Rocket made it to drone spaceport ship, but landed hard. Close, but no cigar this time. Bodes well for the future tho. 10 January 2015Ship itself is fine. Some of the support equipment on the deck will need to be replaced... 10 January 2015Didn't get good landing/impact video. Pitch dark and foggy. Will piece it together from telemetry and ... actual pieces. 10 January 2015^
68.Rocket soft landed in the ocean within 10m of target & nicely vertical! High probability of good droneship landing in non-stormy weather. 11 February 2015^
69.Ascent successful. Dragon enroute to Space Station. Rocket landed on droneship, but too hard for survival. 14 April 2015^
70.Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing 14 April 2015^
74.First stage on target at droneship but looks like hard landing; broke landing leg. Primary mission remains nominal → http://spacex.com/webcast 17 January 2016^
75.However, that was not what prevented it being good. Touchdown speed was ok, but a leg lockout didn't latch, so it tipped over after landing. 17 January 2016^
108.Hans: Last launch had a landing failure due to the winds that the booster encountered not being as predicted. Therefore, the booster decided to divert to a water landing to protect the droneship. retrieved 28 February 2021^
124.Jonathan McDowell. Space-Track confirms the presence of four secret payloads on the Globalstar Falcon 9 launch - USA 328 to USA 331, catalog 52889 to 52892, orbital data not available. One piece of debris, probably a Starlink-style tension rod? 20 June 2022^
125.SThe four classified satellites launched together with Globalstar FM15 on a Falcon 9 rocket yesterday have been detected in a ~535 km orbit at 53 deg inclination. 21 June 2022^
On 17 January 2016, JRTI was put to first use in an attempt to recover a Falcon 9 first-stage booster from the Jason-3 mission from Vandenberg Space Launch Complex 4.[9] The booster successfully landed on the deck; however, a lockout collet failed to engage on one of the legs, causing the first stage to tip over, exploding on impact with the deck.[25] On 14 January 2017, SpaceX launched Falcon 9 flight 29 from Vandenberg Air Force Base and landed the first stage on the JRTI, which was located about 370 km downrange in the Pacific Ocean, making it the first successful landing in the Pacific.[26]
In August 2019, JRTI left the Port of Los Angeles to be towed to the Gulf of Mexico; it transited through the Panama Canal.[27] JRTI arrived in Morgan City, Louisiana in late August 2019 and stayed there until December 2019 then moved to Port Canaveral.[28]
JRTI is based at Port Canaveral and began operations in the Atlantic in June 2020, supporting the first time a Falcon 9 would land after a 5th use.
On February 18, 2025, a Falcon 9 landed on JRTI off the coast of The Bahamas, marking the first international landing of a booster.[29]
It joined the East Coast fleet in July, after sending OCISLY
On 9 July 2021, Elon Musk tweeted aerial footage of the completed drone ship in the Gulf of Mexico while undergoing its first sea-trials. According to him, this drone ship will not require a tug boat to be towed to the landing area. ASOG is used to support rocket launches from a base at Port Canaveral.[37] After completing a sea trial in Port Fourchon, transiting over the Gulf of Mexico while being towed by Finn Falgout from its construction port, Port Fourchon to its recovery base, Port Canaveral, arriving at 16:47 UTC on 15 July 2021, and completing a number of sea trials, it successfully completed its first booster landing attempt for a Falcon 9 first-stage booster B1061.4 being used in CRS-23 mission at 300 km downrange in the Atlantic Ocean, becoming the first ASDS to land a first stage booster in its maiden landing attempt.[38][39][40]
ASOG is based at Port Canaveral to support east coast recovery operations.
Of Course I Still Love You (Marmac 304)
Of Course I Still Love You is registered as 1247500 was built as a refit of the barge Marmac 304 for landings in the Atlantic Ocean. Its homeport was Port Canaveral, Florida, from December 2015 to June 2021, after being ported for a year at the Port of Jacksonville during most of 2015.Of Course I Still Love You worked successfully as a landing platform after the Falcon 9 rocket brought astronauts to space on the crewed mission Demo-2 on 30 May 2020.In June 2021, OCISLY was transported to the Port of Long Beach to begin supporting launches on the west coast.[19] On 8 July 2021, OCISLY was docked in Long Beach after transiting the Panama Canal. It is the first ASDS where 50th and 100th successful landings of a particular ASDS were first achieved.
Just Read the Instructions (Marmac 303)
Just Read the Instructions, the second barge with that name, is registered as 1245062 with MMSI 368219920, and was built as a refit of the barge Marmac 303 in 2015 for landings in the Pacific Ocean. Its homeport was in the Port of Los Angeles, California from 2015 to 2019[53] but in August 2019 it was moved to the Gulf of Mexico.[27]After undergoing upgrades and refurbishment, in December 2019 it was moved to Cape Canaveral.[54] After several months of additional work, including installation of new thrusters, Just Read the Instructions went back into service in June 2020 with booster recovery from Starlink v1.0 L7 mission.[55]
A Shortfall of Gravitas (Marmac 302)
The fourth ASDS, named A Shortfall of Gravitas,[56] is registered as 1240683 with MMSI 368219910 and was mentioned by SpaceX in February 2018 and again in October 2020 to help support East Coast launches.[32] In May 2021, conversion of Marmac 302 into ASOG began and was expected to move to the East Coast for operation in the following months.[57] A Shortfall of Gravitas underwent its first sea trials on 9 July 2021, and a short video of the ship underway was shared on Twitter by Elon Musk.[37] After completing the sea trials, it was towed by Finn Falgout from its construction port, Port Fourchon, to its recovery base, Port Canaveral, arriving 15 July 2021.[58][59][60]
