What Sunita Williams Will Experience During Spacecraft Reentry To Earth

Astronauts Sunita Williams and Butch Wilmore, stranded at the International Space Station (ISS) for over nine months, have finally begun their journey home. According to NASA, their SpaceX Dragon spacecraft undocked from the ISS at 10:35 am IST and is expected to splash down off the Florida coast around 3:27 am IST on Wednesday.

Reentering Earth's atmosphere is one of the most intense phases of space travel. NASA explains that as a spacecraft plunges into the atmosphere, it encounters extreme conditions, including temperatures reaching up to 7,000 degrees Fahrenheit. The spacecraft must be engineered to withstand hypersonic speeds and an enormous slowdown before landing. From the astronaut's perspective, the view from a window during reentry is nothing but a wall of fire. Follow Sunita Williams Homecoming Live Updates Here

How NASA Prepares For Reentry

NASA's Entry Systems & Technology Division plays a crucial role in designing materials and systems that ensure a safe return to Earth. The Ames Research Centre in California has been at the forefront of reentry technology since 1961. Using heat shields, parachutes, and advanced software, NASA engineers develop solutions that help spacecraft survive the fiery descent.

Reentry Technologies

• Heat Shields - These protective barriers absorb and dissipate heat. Materials like Avcoat (used in Apollo missions and the Orion Crew Capsule) and Phenolic-Impregnated Carbon Ablator (PICA) help prevent overheating. SpaceX even developed its own version, PICA-X, for the Dragon capsule.
• Arc Jet Testing - At Ames' Arc Jet Complex, NASA scientists recreate the scorching heat of atmospheric entry, subjecting heat shields to plasma hotter than the Sun's surface.
• Computer Simulations - Supercomputers model reentry dynamics to predict and solve technical challenges before missions launch.
• ADEPT and HEEET - New materials and deployable heat shields, like HEEET (Heatshield for Extreme Entry Environment Technology) and ADEPT (Adaptable, Deployable Entry Placement Technology), aim to enhance spacecraft protection for missions to Mars, Venus, and beyond.

Lessons from Past Missions

NASA has learned invaluable lessons from past missions, from the Apollo moon missions to the Mars Science Laboratory and Stardust comet sample return mission. Even the Space Shuttle programme, which featured reusable orbiters, provided valuable insights into reentry aerodynamics.

The Apollo, Challenger, Columbia Lessons Learned Programme (ACCLLP), established in 2016, ensures that insights from critical missions are shared across generations to prevent past failures from repeating.

The Apollo 13 mission, famously called a "successful failure," demonstrated the importance of contingency planning and problem-solving when an oxygen tank explosion jeopardised the crew's survival. 

NASA's Lessons Learned Information System (LLIS) supports knowledge-sharing, allowing engineers to make informed decisions and mitigate risks in future missions.

NASA's Space Shuttle Programme

NASA's Space Shuttle program, which ran from 1981 to 2011, was the first to use reusable spacecraft for human spaceflight. The fleet included Columbia, Challenger, Discovery, Atlantis, and Endeavour, designed to carry up to seven astronauts and various payloads into low Earth orbit. 

The Shuttle launched like a rocket, operated in space, and returned to Earth like a glider. It played a crucial role in deploying satellites, conducting scientific experiments, repairing the Hubble Space Telescope, and assembling the ISS. The program completed 135 missions but faced major tragedies - the Challenger disaster in 1986 and Columbia in 2003 - leading to critical safety improvements.

The Shuttle consisted of an orbiter vehicle, two solid rocket boosters, and an external fuel tank, with all components except the tank being reusable. After the programme ended in 2011, NASA shifted focus to new spaceflight technologies and partnerships, using lessons from the Shuttle era to develop future exploration missions, including Artemis and commercial crew programmes.