An autonomous spaceport drone ship (ASDS) is an ocean-going vessel derived from a deck barge, outfitted with station-keeping engines and a large landing platform. Construction of such ships was commissioned by aerospace company SpaceX to allow for recovery of rocket first-stages at sea for high-velocity missions which do not carry enough fuel to return to the launch site after lofting spacecraft onto an orbital trajectory.
SpaceX has two operational drone ships and has a third under construction as of early 2018. Just Read the Instructions operates in the Pacific for launches from Vandenberg; Of Course I Still Love You operates in the Atlantic for launches from Cape Canaveral. A Shortfall of Gravitas is under construction. As of 11 May 2018, 20 Falcon 9 flights have attempted to land on a drone ship, with 14 of them succeeding.
The ASDS ships are a key component of the SpaceX reusable launch system development program which aims to significantly lower the price of space launch services through "full and rapid reusability." Any flights going to geostationary orbit or exceeding escape velocity will require landing at sea, encompassing about half of SpaceX missions.
Video Autonomous spaceport drone ship
History
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 publicly announced that they had contracted with a Louisiana shipyard to build a floating landing platform for reusable orbital launch vehicles. Early information indicated that the platform would carry an approximately 90-by-50-meter (300 ft × 160 ft) landing pad and would be capable of precision positioning so that the platform could hold its position for launch vehicle landing. 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 (30.409144°N 81.582493°W / 30.409144; -81.582493) where SpaceX built a stand to secure the Falcon stage during post-landing operations. The stand consists of four 15,000 lb (6,800 kg), 107 in (270 cm) tall and 96.25 in (244.5 cm) wide pedestal structures bolted to a concrete base. A mobile crane will lift the stage from the ship and place 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 will occur here.
The ASDS landing location for the first landing test was in the Atlantic approximately 200 miles (320 km) northeast of the launch location at Cape Canaveral, and 165 miles (266 km) southeast of Charleston, South Carolina.
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, with a sister ship planned for west coast launches to be named Of Course I Still Love You. On 29 January, SpaceX released a manipulated photo of the ship with the name illustrating how it would look once painted. Both ships are named after two General Contact Units, spaceships commanded by autonomous artificial intelligences, that appear in The Player of Games, a Culture novel by Iain M. Banks.
The first Just Read the Instructions was retired in May 2015 after approximately six months of service in the Atlantic, 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.
The active ASDS fleet
In early 2015, SpaceX leased two additional deck barges--Marmac 303 and Marmac 304--and initiated refit to construct two additional autonomous-operation-capable ASDS ships, built on the hulls of these Marmac barges.
Of Course I Still Love You
The second ASDS barge, Of Course I Still Love You (OCISLY), had been under construction in a Louisiana shipyard since early 2015 using a different hull--Marmac 304--in order to service launches on the east coast. It was built as a replacement for the first Just Read the Instructions and entered operational service for Falcon 9 Flight 19 in late June 2015. As of June 2015, its home port was Jacksonville, Florida, but after December 2015, it was transferred 160 miles (260 km) further south, at Port Canaveral.
While the dimensions of the ship are nearly identical to the first ASDS, several enhancements were made including a steel blast wall erected between the aft containers and the landing deck. The ship was in place for a first-stage landing test on the CRS-7 mission, which failed on launch on 28 June 2015.
On 8 April 2016 the first stage, which launched the Dragon CRS-8 spacecraft, successfully landed for the first time ever on OCISLY, which is also the first ever drone ship landing.
In February 2018, the Falcon Heavy Test Flight's central core exploded upon impact next to OCISLY that damaged two of the four thrusters on the drone ship. Two thrusters were removed from the Marmac 303 barge in order to repair OCISLY.
Just Read the Instructions
The third ASDS barge, using the Marmac 303 hull, was built during 2015 in a Louisiana shipyard, and the barge transited the Panama Canal in June 2015 carrying its wing extensions as cargo on the deck because the ASDS, when complete, would be too wide to pass through the canal.
The home port for the Marmac 303 is the Port of Los Angeles, at the AltaSea marine research and business campus in San Pedro's outer harbor. The landing platform and tender vessels began docking there in July 2015 in advance of the main construction of AltaSea which is scheduled for 2017.
SpaceX announced that the Marmac 303 would be the second ASDS to be named Just Read the Instructions (JRtI) in January 2016, shortly before its first use as a landing platform for Falcon 9 Flight 21.
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. The booster successfully landed on the deck, however, a lockout collet failed to engage on one of the legs causing the rocket to tip over, exploding on impact with the deck. On January 14, 2017, SpaceX launched Falcon 9 Flight 29 from Vandenberg and landed the first stage on the JRtI that was located about 370 km (230 mi) downrange in the Pacific Ocean, making it the first successful landing in the Pacific.
Under construction
SpaceX began construction of a fourth deck barge in early 2018.
A Shortfall of Gravitas
The fourth ASDS barge was announced to be under construction in February 2018 and it will become the second active east coast-based ASDS. It will be homeported at Port Canaveral. This future simultaneously usable ASDS, along with OCISLY, is called A Shortfall of Gravitas (ASoG) and like the rest of the fleet, its naming is based on names used in the Culture series.
Maps Autonomous spaceport drone ship
Characteristics
The ASDS are autonomous vessels capable of precision positioning, originally stated to be within 3 meters (9.8 ft) even under storm conditions, using GPS position information and four diesel-powered azimuth thrusters. In addition to the autonomous operating mode, the ships may also be telerobotically controlled.
The azimuth thrusters are hydraulic propulsion outdrive units with modular diesel-hydraulic-drive power units and a modular controller all manufactured by Thrustmaster, a marine equipment manufacturer in Texas. The returning rocket 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 shelf GoPro cameras.
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.
Naming
The two ASDS names used so far, Just Read the Instructions (JRtI), and Of Course I Still Love You (OCISLY), pay homage to the works of the late science fiction author Iain M. Banks by being based on his Culture fictional universe. Both JRtI and OCISLY are names of enormous, sentient starships, which appeared in the novel The Player of Games. The third name that will be used for the fourth ASDS will be A Shortfall of Gravitas (ASOG) that is similarly drawn from the Culture-milieu of Iain M. Banks. The Culture series has a running gag on having some starships that include "Gravitas" within their names.
Just Read the Instructions (Marmac 300)
The landing platform of the upper deck of the first barge named Just Read the Instructions was 52 m × 91 m (170 ft × 300 ft) while the span of the Falcon 9 v1.1 landing legs was 18 m (60 ft). The vessel was retired in 2015.
Of Course I Still Love You (Marmac 304)
Of Course I Still Love You was built as a refit of the barge Marmac 304 for landings in the Atlantic Ocean. Its homeport is in Port Canaveral, Florida since December 2015, after being ported for a year at the Port of Jacksonville during most of 2015.
Just Read the Instructions (Marmac 303)
Just Read the Instructions, the second barge with that name, was built as a refit of the barge Marmac 303 in 2015 for landings in the Pacific Ocean. Its homeport is the Port of Los Angeles, California.
A Shortfall of Gravitas (under construction)
The fourth ASDS is named A Shortfall of Gravitas, under construction as of early 2018, will be used on the east coast to support high flight rates for Falcon 9 and tandem ocean landings for Falcon Heavy side boosters.
Operation
A tug is used to bring the ASDS to its oceanic position, and a support ship stands by some distance away from the crewless ASDS. The vessels initially used on the east coast were Elsbeth III (tug) and Go Quest (support). 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. The rocket stage is secured to the deck of the drone ship with steel hold downs welded on to the feet of the landing legs. 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. Fans call the robot "Optimus Prime" or "Roomba," the latter of which has been turned into a backronym for "Remotely Operated Orientation and Mass Balance Adjustment."
Vessel missions
The first flight test was 10 January 2015 when SpaceX conducted a controlled-descent flight test to land the first-stage of Falcon 9 Flight 14 on a solid surface after it was used to loft a contracted payload toward Earth orbit. SpaceX projected prior to the first landing attempt that the likelihood of successfully landing on the platform would be 50 percent or less. The landings went from being landing tests towards being routine parts of missions.
See also
- List of Falcon 9 and Falcon Heavy launches
- Reusable launch system
- Vertical Take-off, Vertical Landing
References
External links
- Thrustmaster drive unit specifications
Source of the article : Wikipedia
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