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SpaceX is set to send its first full crew of astronauts into space for NASA, in a newly certified launch system for manned spaceflight. The Falcon 9 rocket is upright on the launch pad, a Crew Dragon spacecraft securely secured to its nose. The engines have been tested. Four astronauts eagerly await the countdown: The launch is scheduled for Sunday at 7:27 pm ET.
Since SpaceX’s first human launch, a demonstration that sent NASA astronauts Bob Behnken and Doug Hurley to the International Space Station (ISS), the company has fixed several problems with its system.
On that mission, called Demo-2, the fierce crash of the Crew Dragon spacecraft through Earth’s atmosphere wore down its protective shield more than expected. Their parachutes were deployed a bit late too, and then ships full of spectators swarmed the tan capsule once it landed. Additionally, a few weeks after the astronauts returned, another Falcon 9 launch revealed that a nail polish-like substance was clogging the engine vents.
NASA and SpaceX have worked quickly to correct these flaws, adapt their processes, and upgrade the hardware. As a result, the next mission, called Crew-1, will look different than Behnken and Hurley’s.
“We are making a lot of improvements to this flight compared to Demo-2,” Steve Stich, manager of NASA’s Commercial Crew Program, said in a briefing Tuesday. “So we continue to evolve and be safer as we move towards these flights.”
This is how SpaceX changed its system.
Checking small holes for nail polish-like build-up
SpaceX was scheduled to launch a routine satellite mission on October 2, but seconds before takeoff, a flight computer detected a problem and automatically shut everything down.
The problem turned out to be with the Falcon 9’s Merlin engines: a small hole in a relief valve had been clogged with a lacquer that is used to coat certain parts of the rocket while applying a treatment to prevent corrosion in other areas. This could have resulted in an explosion that would have vibrated and damaged the engines, like a car failing.
So SpaceX examined all of its engines for similar traces of the nail polish-like substance.
“SpaceX and the NASA team looked through the launch vehicle for any other areas that might have a small passageway that could be blocked by this similar masking process. And we cleaned up all that hardware,” Stich said.
Separately, the engines also have new bladed turbine wheels, similar to jet engines, that pump the liquid fuel. The upgrade makes the wheels less prone to vibrations called “resonances,” which can damage hardware.
“These wheels are a little more robust for the type of acceleration profile that Merlin engines fly,” Stich said. “So we are happy to have that as a security enhancement.”
New and durable solar panels
The crew for the next mission, called Crew-1, consists of NASA astronauts Mike Hopkins, Victor Glover and Shannon Walker, and Japan Aerospace Exploration Agency astronaut Soichi Noguchi. They are scheduled to dock at the space station around 11 p.m. ET Monday after a 27-hour journey. After that, they will spend six months in the orbital laboratory.
His Crew Dragon capsule will also remain on the ISS for that entire time. Keeping a spacecraft in orbit may seem easy, but while there, the rover soaks up solar radiation and endures extreme temperatures. In fact, the capsule Behnken and Hurley flew, which they named Endeavor, likely would not have survived a six-month-long space mission. Its solar panels would likely have degraded significantly after 110 days in orbit.
So Resilience, as the new capsule is known, has a set of solar panels that can last 210 days (almost seven months).
New software allows Crew Dragon to change ports on the ISS
Docking to a space station port requires Crew Dragon to perform a series of complex maneuvers. But you may not be able to stay berthed at the same location for the full six months. Unlike the capsule used in the Demo-2 flight, this one is programmed with the ability to move to another port to make room for other incoming spacecraft.
“It’s a bit crowded in space. And that’s a really good thing,” NASA astronaut Suni Williams said at a briefing on Friday.
Williams is ready to fly the first operational mission of Boeing’s CST-100 Starliner, Boeing’s spacecraft for astronauts, which was funded and designed through the same NASA program that gave rise to SpaceX’s Crew Dragon. The Starliner is set to retry an unmanned test flight to the space station in 2021, as the first test failed. That might require Crew Dragon to move to a different port.
To relocate the spacecraft, the crew will go back up and run new software that should move the Crew Dragon away from its original docking point, the forward port, and re-dock at the station’s Zenith port.
The flight is scheduled to be autonomous, but the crew will oversee the process. They can manually maneuver the spacecraft if something goes wrong.
A fortified heat shield to return to Earth
After Behnken and Hurley entered the Gulf of Mexico and a recovery team removed them, SpaceX studied the tan Endeavor spacecraft closely. Examiners found something unusual: deep erosion on the Crew Dragon’s heat shield.
This thermal protection system is a collection of heat resistant mosaics that line the underside of the spacecraft. It deflects and absorbs heat that can reach 3,500 degrees Fahrenheit when the space capsule plummets through the atmosphere on its return to Earth.
One of the heat shield tiles suffered “a little more erosion than we wanted to see,” Hans Koenigsmann, SpaceX vice president of build and flight reliability, said in September.
So SpaceX reinforced the heat shield of the new Crew Dragon with stronger materials. Next, NASA tested five samples of the new tile in a wind tunnel that simulates the reentry environment.
“I’m sure we have solved this particular problem very well,” Koenigsmann said.
The parachutes should open higher
As Crew Dragon approaches Earth towards the end of its descent, traveling at 350 miles per hour, it should deploy its first two parachutes at about 18,000 feet. But on Behnken and Hurley’s reentry flight, that happened closer to the ground than NASA and SpaceX expected.
As it turned out, a filter that vents the air in the sensor that measures atmospheric pressure had become clogged.
“That particular filter has been opened a little bit so it’s less restricted,” Koenigsmann said. “That has the effect that we measure the barometric pressure more accurately and lower and deliver the parachute just in time.”
Also, Stich said, “We have made some improvements to the [spaceship] structure so that we can handle a little more wind in the landing zone, which gives us a few more opportunities to land. “
Keep boats away from the landing site
When the Endeavor capsule crashed into the Gulf of Mexico, a straight line of spectator ships flooded the tanned spacecraft. Some passed alarmingly close.
That’s a danger for astronauts and a danger for navigators, since after passing through Earth’s atmosphere, the capsule was enveloped in low levels of a poisonous gas called nitrogen tetroxide.
To keep would-be bystanders away from the Resilience capsule when it finally returns to Earth, SpaceX and NASA plan to establish a 10-mile, boat-free perimeter around the landing site. They also hope to have more Coast Guard ships there to enforce the law.
“We ask that all mariners abide by all notices and guidance from our partners with the Coast Guard and the Navy,” Benji Reed, senior director of manned spaceflight programs at SpaceX, said in a briefing Tuesday. “Any distraction or interference with those operations can cause significant delays and, in fact, can put the crew themselves and our recovery teams at risk.”