After a two-day readiness review, NASA managers gave SpaceX the green light Friday to make final preparations for the launch on Wednesday, May 27, of a commercial spacecraft carrying astronauts Doug Hurley and Bob Behnken to the International Space Station on the first space flight orbit from American soil since 2011.
A few hours later, SpaceX fired the 65-meter-high Falcon 9 rocket that will propel Hurley and Behnken into orbit aboard the company’s Crew Dragon spacecraft.
The conclusion of the Flight Readiness Review on Friday kicked off a busy Memorial Day weekend at the Kennedy Space Center. Dragon astronauts will don their FlightX-made flight suits on Saturday and ride in a Tesla Model X automobile to launch ramp 39A, where the Falcon 9 and Crew Dragon capsules were placed on their launch mounts by the sea on Thursday.
Hurley and Behnken – both veterans of two space shuttle flights – will board the Dragon capsule with the help of half a dozen SpaceX crew technicians, practicing the steps to follow on launch day.
SpaceX will hold a launch readiness review on Monday to review the data and results of the test fire on Friday and the crew rehearsal on Saturday. If all goes well, preparations will continue for the launch of the first orbital crewed mission from the Kennedy Space Center in nearly nine years at 4.33 p.m. EDT (2033 GMT) Wednesday.
Assuming the mission takes off on Wednesday, the Crew Dragon is expected to slide into an automated docking with the International Space Station at around 11:40 a.m. EDT (1540 GMT) Thursday. Hurley and Behnken are expected to spend months of an hour at the research outpost in orbit before returning to Earth for a parachute-assisted splash in the Atlantic Ocean.
The flight preparation exam started on Thursday and continued on Friday. NASA officials have anticipated what might happen, given the volume of data to be discussed for the first crew flight on a completely new spacecraft design.
“We had a very successful pre-flight test, in the sense that we did a thorough review of all systems and all risks,” said Steve Jurczyk, associate administrator of NASA, who chaired the review meeting. “And it was unanimous on the board that we were leaving for the launch.
“It’s really exciting to launch American astronauts on American rockets from American soil – from the Kennedy Space Center – for the first time in nine years,” Jurczyk said at a press conference on Friday. “I know the road has been long and really tough, and I can’t say how proud I am of the NASA-SpaceX team for all their talent, hard work, dedication and persistence in achieving this. point five days after its launch. “
NASA administrator Jim Bridenstine confirms flight readiness review resulted in GO to launch May 27 for Crew Dragon test flight, first orbital crewed mission since American soil since 2011. https://t.co/Y9pANccivZ pic.twitter.com/sEAaNdz4FM
– Spaceflight Now (@SpaceflightNow) May 22, 2020
“Today was the kick-off, but it’s really a blow to the mission,” said Benji Reed, director of mission management for the SpaceX crew. “There will be much more data, much more advice in the coming days. There will be constant vigilance and monitoring of data and observations. During the mission, there will be other reviews and conversations to make sure we go there for every aspect, including going home. “
NASA managers received briefings from agency and SpaceX engineers during the Flight Readiness Review, including presentations on topics that have received attention over the past year, such as parachutes from the Crew Dragon and an interrupted propulsion system problem that led to the explosion of a capsule during a ground test in April 2019.
“We established some time ago that the original design of the chute did not have an adequate margin, based on some knowledge that we had acquired by testing the way the chutes were deployed and the loading on the chutes” said Jurczyk. “So SpaceX stepped in and made a new chute design, and we had to qualify this new chute design at higher margins than the previous chutes.
“The NASA-SpaceX team has done an incredible job of establishing a test schedule and running that test schedule,” said Jurczyk. “However, there are fewer tests than we would normally see with a parachute qualification program. So we took a lot of time in a few presentations during the exam for the team to guide us through the design, changes, qualifying tests and margins on the chute to make sure everyone was okay with how these chutes were qualified. . And we had great confidence that they will work as we need them when Bob and Doug return from the International Space Station.
The Crew Dragon uses a series of pilot and drug chute during the descent, then deploys four main parachutes to brake in the event of a splash. At the end of a typical mission, the Crew Dragon spacecraft will dive in the Atlantic Ocean about 24 nautical miles off the coast of Cape Canaveral.
The capsule disconnection system was also the subject of extensive discussion during the flight preparation review. In the event of a major problem during the refueling of the Falcon 9 rocket, or failure to launch during the ascent into orbit of the vehicle, the Crew Dragon can fire eight SuperDraco engines to push the capsule out of the launcher and propel the astronauts safely .
SuperDracos use a high pressure mixture of hydrazine fuel and nitrogen tetroxide oxidant. A Dragon spacecraft that flew an unmanned test flight to the space station in March 2019 was destroyed during a ground test of SuperDraco engines last April in Cape Canaveral.
Investigators found the cause of the explosion in a leaking valve inside the capsule’s high-pressure propulsion system. This leak allowed nitrogen tetroxide to infiltrate the helium pressurization lines of the propulsion system, which are designed to quickly prime SuperDraco propellants to fire in rapid response to a launch emergency .
As the pressurization system activated during last year’s ground tests, a slug of nitrogen tetroxide was forced into the defective titanium valve, triggering an explosion. Experts spent months studying the physics of the crash and learned new information about how the titanium components used in aerospace vehicles could ignite under certain conditions.
SpaceX replaced the suspect valve in the future Crew Dragon spacecraft with a single-use rupture disc designed to rupture upon activation of the SuperDraco abandonment thrusters, which would only happen if the launch.
The fix was tested during a second ground shot in November and again during a high altitude launch evacuation test in January over the Atlantic Ocean.
“Last April, I probably didn’t think I was going to fly (crew) in a year, but you can never sell this NASA and SpaceX team,” said Kathy Lueders, manager of the commercial crew program from NASA. “They have always worked miracles for me, and I am very, very proud of them right now. “
Jurczyk said NASA officials also discussed a recent “performance deficit” when testing the Crew Dragon’s internal fire extinguisher system.
“It is a system that suppresses any fire or equipment under the ground of Dragon,” Jurczyk said. “The team … analyzed the dangers there, as well as the ability to suppress a fire, and we felt the risk was very low there. “
Jurczyk replaced Doug Loverro, the former chief executive officer of NASA’s human space flights, for this week’s Flight Readiness Review. Loverro, who was to chair the FRR, abruptly resigned on Monday May 18.
In a letter to NASA employees, Loverro wrote that he had resigned because of a “mistake” he made earlier this year. Several sources said Loverro violated a supply rule in a competition to select contractors for NASA’s human landing system for the Artemis program, which aims to develop crewed lunar landing vehicles for transport astronauts to the lunar surface.
Jurczyk, NASA’s most senior public servant, became president of the Flight Readiness Review.
The Crew Dragon’s first flight with astronauts lasted for almost a decade. NASA awarded SpaceX funding for the first time to work on a human-rated spacecraft in 2011.
Funded and led by billionaire Elon Musk, SpaceX has won a series of contracts and funding agreements with NASA over the past nine years for its work on the Crew Dragon project. To date, NASA has agreed to pay SpaceX more than $ 3.1 billion to develop the Crew Dragon, and then perform at least six operational crew rotation missions to the space station.
NASA has also awarded Boeing a similar series of contracts for the development and flights of the Starliner crew capsule. The first unmanned Starliner test mission ended prematurely in December without reaching the space station, and Boeing will resume the unmanned demonstration mission later this year before the Starliner is authorized for its first launch with astronauts .
The first operational Crew Dragon flight will follow the test flight scheduled for launch next week, which is officially designated Demo-2 or DM-2. It follows Crew Dragon’s first test flight to the space station last year, which did not carry any astronauts on board.
SpaceX also performed two major tests of the Crew Dragon’s launch interrupt system – a pad interrupt in 2015 and the flight escape demonstration in January.
According to Jurczyk, this week’s FRR has doubled as the “Human Rating Certification Intermediate Exam” for SpaceX’s Crew Dragon spacecraft.
“What I mean by acting is that we have validated that this system meets the human rating certification requirements for the Demo-2 mission, and these requirements are reflected in future missions, including the Crew- 1 (the first operational team for the Dragon rotation), ”said Jurczyk. “We will have a final human rating certification exam after the demo-2 and before the Crew-1 mission, just to certify the relatively small set of design changes between the Demo-2 system and the Crew-1 system. And at that point, we will consider that the system is certified humanely. “
NASA has also determined that the Crew Dragon meets the agency’s risk requirements for the commercial crew program. When NASA established requirements for new commercial crew spacecraft, agency officials set the program’s security threshold at 1 in 270 chance of accident during a 210-day mission that would kill astronauts on board
Lueders said Friday that SpaceX meets this risk requirement, with the help of advanced design models and inspections to guard against the threat of micrometeoroids and orbital debris when docked at the space station.
But it is difficult to determine the probability of loss of crew or LOC for a given flight. The number depends on a number of factors, including numerical and statistical data, many of which are based on assumptions.
Bill Gerstenmaier, who led NASA’s human space flight programs from 2005 to last year, said in 2017 that when the space shuttle first flew in 1981, officials had calculated the probability of a crew loss for this mission between 1 in 500 and 1 in 5000. After anchoring the loss of the crew model with the shuttle mission flight data, NASA determined that the first flight of the space shuttle had actually a 1 in 12 chance of ending in the loss of the crew.
Regardless of the inconsistent numbers, officials agree that a test flight of a new spacecraft is risky.
“Right now, we are trying to identify any risks that we know of, and we are continuing to review and redeem the risks,” said Lueders. “But neither can we deceive ourselves. Human spaceflight is really, really difficult, and that’s why we continue to look for risks and do additional assessments. We never feel comfortable because it’s when you’re not looking.
“Our teams are scouring and thinking about all the risks that exist, and we have worked hard to buy the ones we know,” she said. “And we will keep looking for and keep buying them until we bring them (Hurley and Behnken) home. “
NASA astronaut Bob Behnken, joint operations commander of the Crew Dragon Demo-2, discusses his views on the risk of the next test flight to the International Space Station. https://t.co/Y9pANccivZ pic.twitter.com/49Q3VeYSFS
– Spaceflight Now (@SpaceflightNow) May 22, 2020
Last Friday, at their last pre-launch press conference, the Dragon astronauts said they were comfortable with the risk.
“We have had the luxury in the past five years and more of being deeply grounded and understanding the trades that have been done,” said Behnken, joint operations commander of the Demo-2 mission. “There are often cases where a hardware change can be implemented, or there can be an operational change that reduces that risk, or somehow manages it.
“I think we are really comfortable with this, and we think these exchanges have been done appropriately,” he said. “Regarding the news, we probably have more of it than any other crew (has had) in recent history. “
In addition to testing the Crew Dragon spacecraft itself, SpaceX has launched 84 Falcon 9 rocket missions since the first version of the launcher debuted on June 4, 2010. Eighty-three of the flights succeeded in reaching ‘orbit.
A Falcon 9 rocket exploded in the final minutes before a test ground shot at Cape Canaveral in September 2016. SpaceX said the failure was caused when a helium pressure tank suddenly broke on the second floor of Falcon 9.
After introducing design fixes, SpaceX recorded 59 consecutive successful launches using Falcon 9 and Falcon Heavy rockets.
“It wasn’t a long story (on the Falcon 9) when we started this program, but it turned out to have a number of flights under its belt, and its evolution became more and more secure as and as it goes along, ”said Behnken. “It’s something that we really appreciate. It is remarkable to see all the other missions that have contributed to the human spaceflight program by being, in a sense, a test mission for us before we get the chance to fly on the Falcon 9. “
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