Here’s How SpaceX’s Crew Dragon Returns to Home from the ISS
And it seems like a sci-fi movie.
Venkatapathi Raju Gangiri
Venkatapathi Raju Gangiri
Aug 1, 2020 · 6 min read
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Cargo Dragon approaching ISS | Image: SpaceX
Saturday, May 30, 2020. If not for the historic Crew Dragon launch, this day would have been just another Saturday in these dark days of the pandemic.
While the world is watching, at 3:22 p.m. EDT the SpaceX’s Falcon 9 launched Crew Dragon’s second demonstration (Demo-2) mission from Launch Complex 39A (LC-39A) at NASA’s Kennedy Space Center in Florida.
As the engines roar, the astronauts, Bob Behnken, and Doug Hurley aboard the only reusable rocket lifted off. The duo arrived at the International Space Station (ISS) the next day as the Crew Dragon docked autonomously. This is indeed an inflection point for both NASA and SpaceX.
T-0 — Ignition! Lift Off! Crew Dragon! Go NASA! Go SpaceX! Bob and Doug
This entire spectacular feat was named Launch America. Such a metaphor is justified as this moment marks the return of human spaceflight to the United States since the Space Shuttle program was called off in 2011. NASA seems to be in line with its aspirations for the Commercial Crew program. Though Boeing and SpaceX were selected by NASA in September 2014, to transport crew to the ISS, SpaceX has the head start. Thanks to Musk time — you get this if you have read Musk’s biography.
This Demo-2 test flight will help NASA certify SpaceX’s capabilities for regular trips carrying astronauts to the ISS. The test flight completes when Bob and Doug splashdown safely in the Atlantic Ocean.
Bob and Doug set to return this Sunday
The duo is looking forward to returning home to earth after a productive stay of more than two months at the ISS since their arrival. If weather permits, undocking will be at approximately 7:34 p.m. EDT Saturday, Aug. 1, and splashdown at 2:42 p.m. EDT on Sunday.
Getting back home safe is more complex than the launch
We witnessed a sci-fi kind of drama when the Crew Dragon is launched. I loved it and so does everyone. The return is undoubtedly a thriller considering the complexities involved. As the Verge reported, Garrett Reisman, a former NASA astronaut and SpaceX consultant who used to work on the Crew Dragon quoted
FROM THE LAWS OF PHYSICS STANDPOINT, WE’RE ONLY HALFWAY DONE.
He further told, “All that energy you put in [during launch], you have to take every bit of that energy out when you come home.”
Though SpaceX mastered the physics of landing the rocket boosters back to earth, be it on drone ships with bizarre names or a landing pad, this particular mission is completely different. The only reason this being the manned mission adds new but odd colors to the palette. SpaceX did get the Crew Dragon capsule back to earth from space but only once and it was just the cargo version. So this time would be challenging for SpaceX.
Adding to these, there are a lot of dynamic factors like the weather — Tropical Storm Isaias, the heat up to 3,500 degrees Fahrenheit on re-entry ensuing a communications blackout for about six minutes with the mission control. A lot of humans are involved in the whole crew recovery process after the splashdown in the ocean. Each of these has to go as planned.
The major milestones of the return
Before we explore what happens from undocking to splashdown, it is imperative to know where the capsule splashes down. There are seven potential splashdown zones chosen to facilitate a safe return. They are Pensacola, Tampa, Tallahassee, Panama City, Cape Canaveral, Daytona, and Jacksonville. NASA and SpaceX teams will choose primary and alternate splashdown locations based on set criteria.
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Image Credit: NASA
Undocking: Once the GO for undocking is received, the hooks holding the Dragon Endeavour (the name the crew gave for the capsule ) in place with the ISS will retract, letting the spacecraft go free. Two small engine burns follow immediately. At this time, the capsule together with the trunk weighs approximately 27,600 pounds.
Four autonomous engine burns: Once flying free there will be four autonomous engine burns taking the Endeavour away from the Space Station. The journey to home begins.
Departure phasing burn: Several hours later, a departure burn lasting about six minutes puts the spacecraft to the orbital path to sync with any of the possible splashdown zones.
Final deorbit burn: Once the capsule separates from the trunk, the Endeavour executes the final deorbit burn to align with the proper trajectory with the chosen splashdown zone. By the way, the separated trunk just burn up in the atmosphere, thanks to the heat of foresaid 3,500 degrees Fahrenheit on re-entry! By this time the Crew Dragon capsule weight comes down to approximately 21,200 pounds. Now there’s no going back. There is no NO GO. Just splashdown in the home waters.
Pre-Splashdown: Once the capsule is back inside the Earth’s atmosphere it needs to slow down from a speed of approximately 350 miles per hour — for a subtle splashdown. A set of two drogue parachutes deploy at about 18,000 feet in altitude. Further down the line, while the capsule is at about 6,000 feet in altitude moving approximately 119 miles per hour, four main parachutes will deploy.
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SpaceX’s Crew Dragon is guided by four parachutes as it splashes down in the Atlantic on March 8, 2019, after the uncrewed spacecraft’s return from the International Space Station on the Demo-1 mission. Credits: NASA/Cory Huston
Splashdown: SpaceX is capable of supporting splashdown at any of the seven locations. Two recovery ships, the Go Searcher and the Go Navigator split will be deployed strategically along the coast. Each ship will have more than 40 personnel from SpaceX and NASA — spacecraft engineers, trained water recovery experts, medical professionals, the ship’s crew, NASA cargo experts, and others, for the recovery.
Right after splashdown, two fast boats with SpaceX personnel from either of the two main ships will reach the target location. The team on the first boat will check the capsule integrity and the presence of any hypergolic propellant vapors — traces of the fuel which can lead to fire on oxidizing. Once cleared, the capsule will be prepared for the recovery by the main ship. The crew on the second fast boat will recover the parachutes ejected by the capsule right before splashdown.
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NASA astronauts Doug Hurley, left, and Bob Behnken rehearse crew extraction from SpaceX’s Crew Dragon, which will be used to carry humans to the International Space Station, on August 13, 2019 at the Trident Basin in Cape Canaveral, Florida. Credits: NASA/Bill Ingalls
By this time, the main ship will reach the location and the capsule will be picked up on to the deck. Then the capsule’s hatch will be opened to assist Bob and Doug out of it. The medical professionals will carry out initial health checks. This entire process will take about 45 to 60 minutes.
Bob and Doug will reach the shore either on the ship or by the helicopter, to board the waiting NASA plane to fly back to the Ellington Field, Houston.
What happens next to the Dragon Endeavour?
The capsule will be shipped to the SpaceX Dragon Lair in Florida, where the teams of SpaceX and NASA will analyze the mission data and spacecraft performance to complete the certification. This process will take about six weeks.
Once certified, SpaceX receives GO for regular tours to the space station. The first operational mission will be the Crew-1 mission carrying four crew members, three of NASA, and one of the Japan Aerospace Exploration Agency (JAXA) from Launch Complex 39A at NASA’s Kennedy Space Center in Florida.
The ground teams remain to GO for the departure this Saturday night. However, the probability for GO and NO-GO is equal considering the stormy weather over the coast. If weather permits we can watch the live coverage on NASA TV from 5:15 PM EDT, Saturday.
I suggest watching Every Astronaut channel on YouTube for detailed coverage.
Let us hope Bob and Doug return home safely asphalting the way for more collaborative private participation in the space arena.
Medium.***