{"id":12176,"date":"2024-07-10T22:00:00","date_gmt":"2024-07-10T22:00:00","guid":{"rendered":"https:\/\/modernsciences.org\/staging\/4414\/?p=12176"},"modified":"2024-06-28T03:44:12","modified_gmt":"2024-06-28T03:44:12","slug":"the-science-behind-splashdown-an-aerospace-engineer-explains-how-nasa-and-spacex-get-spacecraft-safely-back-on-earth","status":"publish","type":"post","link":"https:\/\/modernsciences.org\/staging\/4414\/the-science-behind-splashdown-an-aerospace-engineer-explains-how-nasa-and-spacex-get-spacecraft-safely-back-on-earth\/","title":{"rendered":"The science behind splashdown \u2212 an aerospace engineer explains how NASA and SpaceX get spacecraft safely back on Earth"},"content":{"rendered":"\n
\n
\n \n
\n The Orion capsule from NASA\u2019s Artemis I mission splashes down.\n NASA via AP<\/a><\/span>\n <\/figcaption>\n <\/figure>\n\n Marcos Fernandez Tous<\/a>, University of North Dakota<\/a><\/em><\/span>\n\n

For about 15 minutes on July 21, 1961, American astronaut Gus Grissom<\/a> felt at the top of the world \u2013 and indeed he was.<\/p>\n\n

Grissom crewed the Liberty Bell 7 mission<\/a>, a ballistic test flight that launched him through the atmosphere from a rocket. During the test, he sat inside a small capsule and reached a peak of over 100 miles up before splashing down in the Atlantic Ocean.<\/p>\n\n

A Navy ship, the USS Randolph, watched the successful end of the mission from a safe distance. Everything had gone according to plan, the controllers at Cape Canaveral were exultant, and Grissom knew he had just entered a VIP club as the second American astronaut in history.<\/p>\n\n

Grissom remained inside his capsule and swayed on the gentle ocean waves. While he waited for a helicopter to take him onto the USS Randolph\u2019s dry deck, he finished recording some flight data. But then, things took an unexpected turn.<\/p>\n\n

An incorrect command in the capsule\u2019s explosives system caused the hatch to pop out<\/a>, which let water flow into the tiny space. Grissom had also forgotten to close a valve in his spacesuit, so water began to seep into his suit as he fought to stay afloat. <\/p>\n\n

After a dramatic escape from the capsule, he struggled to keep his head above the surface while giving signals to the helicopter pilot that something had gone wrong. The helicopter managed to save him at the last instant.<\/p>\n\n

Grissom\u2019s near-death escape remains one of the most dramatic splashdowns in history. But splashing down into water remains one of the most common ways astronauts return to Earth. I am a professor of aerospace engineering<\/a> who studies the mechanisms involved in these phenomena. Fortunately, most splashdowns are not quite that nerve-racking, at least on paper.<\/p>\n\n

\n \"Two<\/a>\n
\n Navy personnel retrieve the crew from the Apollo 11 return capsule after splashdown on July 24, 1969.<\/span>\n AP Photo\/Barry Sweet<\/a><\/span>\n <\/figcaption>\n <\/figure>\n\n

Splashdown explained<\/h2>\n\n

Before it can perform a safe landing, a spacecraft returning to Earth needs to slow down<\/a>. While it is careening back to Earth, a spacecraft has a lot of kinetic energy. Friction with the atmosphere introduces drag, which slows down the spacecraft. The friction converts the spacecraft\u2019s kinetic energy to thermal energy, or heat.<\/p>\n\n

All this heat radiates out into the surrounding air, which gets really, really hot. Since reentry velocities can be several times the speed of sound, the force of the air pushing back against the vehicle turns the vehicle\u2019s surroundings into a scorching flow that\u2019s about 2,700 degrees Fahrenheit (1,500 degrees Celsius). In the case of SpaceX\u2019s massive Starship rocket<\/a>, this temperature even reaches 3,000 degrees Fahrenheit (nearly 1,700 degrees Celsius)<\/a>. <\/p>\n\n

Unfortunately, no matter how quickly this transfer happens, there\u2019s still not enough time during reentry for the vehicle to slow down to a safe enough velocity not to crash. So, the engineers resort to other methods that can slow down a spacecraft during splashdown. <\/p>\n\n

Parachutes are the first option<\/a>. NASA typically uses designs with bright colors, such as orange, which make them easy to spot. They\u2019re also huge, with diameters of over 100 feet, and each reentry vehicle usually uses more than one for the best stability. <\/p>\n\n

The first parachutes deployed, called drag parachutes, eject when the vehicle\u2019s velocity falls below about 2,300 feet per second (700 meters per second).<\/p>\n\n

Even then, the rocket can\u2019t crash against a hard surface. It needs to land somewhere that will cushion the impact. Researchers figured out early on that water makes an excellent shock absorber. Thus, splashdown was born.<\/p>\n\n

\n