Splashdown

Splashdown is the method of landing a spacecraft or launch vehicle in a body of water, usually by parachute. This has been the primary recovery method of American capsules including NASA's Mercury, Gemini, Apollo and Orion along with the private SpaceX Dragon. It is also possible for the Boeing Starliner, Russian Soyuz, and the Chinese Shenzhou crewed capsules to land in water in case of contingency. NASA recovered the Space Shuttle solid rocket boosters (SRBs) via splashdown, as is done for Rocket Lab's Electron first stage.

As the name suggests, the vehicle parachutes into an ocean or other large body of water. Due to its low density and viscosity, water cushions the spacecraft enough that there is no need for a braking rocket to slow the final descent as is the case with Russian and Chinese crewed space capsules or airbags as is the case with the Starliner.

The American practice came in part because American launch sites are on the coastline and launch primarily over water. Russian launch sites such as Baikonur Cosmodrome are far inland, and most early launch aborts would descend on land.

History

The splashdown method of landing was used for Mercury, Gemini, and Apollo (including Skylab, which used Apollo capsules) missions, and is used for Artemis missions. Soyuz 23 unintentionally landed on a freezing lake with slushy patches of ice during a snowstorm.

On early Mercury flights, a helicopter attached a cable to the capsule, lifted it from the water and delivered it to a nearby ship. This was changed after the sinking of Liberty Bell 7. All later Mercury, Gemini and Apollo capsules had a flotation collar (similar to a rubber life raft) attached to the spacecraft to increase their buoyancy. The spacecraft would then be brought alongside a ship and lifted onto deck by crane.

After the flotation collar is attached, a hatch on the spacecraft is usually opened. At that time, some astronauts decide to be hoisted aboard a helicopter for a ride to the recovery ship and some decided to stay with the spacecraft and be lifted aboard ship via crane. All Gemini and Apollo flights (Apollos 7 to 17) used the former, while Mercury missions from Mercury 6 to Mercury 9, as well as all Skylab missions and Apollo-Soyuz used the latter, especially the Skylab flights as to preserve all medical data. During the Gemini and Apollo programs, NASA used MV Retriever for the astronauts to practice water egress.

Apollo 11 was America's first Moon landing mission and marked the first time that humans walked on the surface of another planetary body. The possibility of the astronauts bringing pathogens from the Moon back to Earth was remote, but not ruled out. To contain any possible contaminants at the scene of the splashdown, the astronauts donned special Biological Isolation Garments and the outside of the suits were scrubbed prior to the astronauts being hoisted aboard USS Hornet and escorted safely inside a Mobile Quarantine Facility.

Both the SpaceX Dragon 1 and Dragon 2 capsules were designed to use the splashdown method of landing. The original cargo Dragon splashed down in the Pacific Ocean off the coast of Baja California. At the request of NASA, both the crew and cargo variations of the Dragon 2 capsule splash down off the coast of Florida, either in the Atlantic Ocean or the Gulf of Mexico.

The early design concept for Orion (then known as the Crew Exploration Vehicle) featured recovery on land using a combination of parachutes and airbags, although it was also designed to make a contingency splashdown if needed. Due to weight considerations, the airbag design concept was dropped for Orion, and it conducts landings via splashdown in the Pacific Ocean off the coast of California.

Disadvantages

Perhaps the most dangerous aspect is the possibility of the spacecraft flooding and sinking. For example, when the hatch of Gus Grissom's Liberty Bell 7 capsule blew prematurely, the capsule sank and Grissom almost drowned. Since the spacecraft's flooding will occur from a location in its hull where it ruptures first, it is important to determine the location on the hull that experiences the highest loading. This location along the impacting side is determined by the surrounding 'air cushion' layer, which deforms the water surface before the moment of impact, and results in a non-trivial geometry of the liquid surface during first touch-down. Soyuz 23 was dragged under a frozen lake by its parachutes. The crew became incapacitated by carbon dioxide and were rescued after a nine-hour recovery operation.

If the capsule comes down far from any recovery forces, the crew may be stranded at sea for an extended period of time. As an example, Scott Carpenter in Aurora 7 overshot the assigned landing zone by 400 kilometers (250 mi). These recovery operation mishaps can be mitigated by placing several vessels on standby in different locations, but this can be an expensive option.

Exposure to salt water can have adverse effects on vehicles intended for reuse, such as Dragon.

Launch vehicles

Some reusable launch vehicles recover components via splashdown. This was first seen with the Space Shuttle SRBs, with STS-1 launching in 1981. Out of 135 launches, NASA recovered all but two sets of SRBs.

SpaceX has conducted propulsive splashdowns of the Falcon 9 first stage, Super Heavy booster, and Starship spacecraft. These vehicles are designed to land on land or modified barges and do not always survive intact after tipping over in the water; SpaceX has mainly conducted propulsive splashdowns for development flights. After the launch of CRS-16, the booster experienced a control issue and splashed down in the ocean instead of making an intended landing at Landing Zone 1.

Rocket Lab intended to catch the first stage of their Electron rocket with a helicopter as it descended under parachute, but abandoned this idea in favor of parachute splashdown. In 2020, Rocket Lab completed their first booster recovery.

List of spacecraft splashdowns

Crewed spacecraft

Uncrewed spacecraft

Gallery

• The Apollo 15 spacecraft splashed down safely despite a parachute failure. (NASA)
• Apollo 15 splashdown (NASA)
• Apollo 11 after splashdown (NASA)
• Apollo 13 hoisted onto ship (NASA)
• Gemini water egress training
• Recovery of the Dragon C2+ on May 31, 2012
• Recovery of the EFT-1 Orion, December 5, 2014
• Landing of SpaceX Demo-2, 2 August 2020
• Artemis II Orion capsule well dock Underway Recovery Test 10 (URT-10)

See also

• Apollo program – 1961–1972 American crewed lunar exploration program
• Apollo–Soyuz Test Project – First international crewed spaceflight missionPages displaying short descriptions of redirect targets
• Helicopter 66 – Individual United States Navy helicopter flown in support of NASA
• Project Gemini – 1961–1966 US human spaceflight program
• Project Mercury – Initial American crewed spaceflight program (1958–1963)
• Skylab – First space station launched and operated by NASA (1973–1979)
• SpaceX Dragon 1 – Partially reusable cargo space capsule
• SpaceX Dragon 2 – 2020s class of partially reusable spacecraft
• Water landing – Aircraft landing on a body of water
• Zond program – Series of Soviet robotic space probes launched between 1964 and 1970

Notes

Bibliography

• Ezell, Linda Neumann (1988), (PDF), vol. II Programs and Projects 1958 - 1968 (NASA SP-4012), (PDF) from the original on October 9, 2022
• Ezell, Linda Neumann (1988), (PDF), vol. III - Programs and Projects 1969 - 1978 (SP-4012), (PDF) from the original on October 9, 2022
• Orloff, Richard W., (PDF), p. 143, (PDF) from the original on October 9, 2022

External links

• The dictionary definition of splashdown at Wiktionary