{"id":11312,"date":"2022-09-02T01:15:43","date_gmt":"2022-09-01T17:15:43","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/nasa-proceeding-with-saturday-launch-attempt-for-artemis-1-moon-mission\/"},"modified":"2022-09-02T01:15:43","modified_gmt":"2022-09-01T17:15:43","slug":"nasa-proceeding-with-saturday-launch-attempt-for-artemis-1-moon-mission","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/nasa-proceeding-with-saturday-launch-attempt-for-artemis-1-moon-mission\/","title":{"rendered":"NASA proceeding with Saturday launch attempt for Artemis 1 moon mission"},"content":{"rendered":"
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NASA\u2019s Space Launch System moon rocket on pad 39B. Credit: Walter Scriptunas II \/ Spaceflight Now<\/figcaption><\/figure>\n

Confident that out-of-bounds engine temperature readings during Monday\u2019s Artemis 1 countdown came from a bad sensor, NASA officials gave the green light Thursday to move forward with another try Saturday afternoon to launch the agency\u2019s giant new moon rocket on an unpiloted test flight from the Kennedy Space Center.<\/p>\n

NASA engineers have also adjusted the timeline for loading super-cold propellants into the Space Launch System moon rocket, allowing more time to flow cryogenic liquid hydrogen through bleed lines to thermally condition the four main engines on the bottom of the core stage.<\/p>\n

Several days of analyses and the revised countdown timeline gave NASA managers enough confidence to develop \u201cflight rationale\u201d to proceed into another countdown Saturday.<\/p>\n

Liftoff of the SLS moon rocket is scheduled during a two-hour window opening at 2:17 p.m. EDT (1817 GMT) Saturday. The 322-foot-tall (98-meter) rocket \u2014 making its first-ever flight \u2014 is the most powerful ever built by NASA, and will produce 8.8 million pounds of ground-shaking thrust at liftoff, more than any launch vehicle ever flown from U.S. soil.<\/p>\n

The Space Launch System rocket will send NASA\u2019s human-rated Orion spacecraft on an unpiloted voyage to orbit the moon and return to Earth. If the launch gets off the ground Saturday, the Orion spacecraft will splash down in the Pacific Ocean west of San Diego on Oct. 11.<\/p>\n

The mission is known as Artemis 1, and will pave the way future crew flights around the moon on the SLS moon rocket and Orion capsule, beginning with Artemis 2 set for launch in 2024.<\/p>\n

NASA officials met Thursday to review the plan for Saturday\u2019s launch attempt. Officials agreed to accept a \u201cmarginal increase\u201d in risk going into the countdown this weekend, said Mike Sarafin, NASA\u2019s Artemis 1 mission manager.<\/p>\n

The risks stem from the thermal conditioning of the rocket\u2019s four main engines, which was the primary cause for scrubbing Monday morning\u2019s countdown. The launch team also detected, and and then resolved, a hydrogen leak in a tail service mast umbilical near the connection between the rocket and its mobile launch platform. Since Monday, technicians at Launch Complex 39B have re-torqued a line believed to be the culprit for the leak.<\/p>\n

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The tail service mast umbilical is located on the SLS Mobile Launcher deck, connecting to the base of the rocket\u2019s core stage. Credit: NASA \/ Spaceflight Now<\/figcaption><\/figure>\n

There was also an intermittent leak discovered in a vent valve system near the \u201cintertank\u201d section during Monday\u2019s countdown, but the system sealed up on its own when exposed to cryogenic temperatures, which can cause seals to contract and re-seat themselves.<\/p>\n

Teams also found a crack in part of the foam insulation on the core stage. The crack itself not a problem for the rocket, but managers evaluated the \u201cvery low\u201d chance that a piece of foam could break during launch, Sarafin said. If it did, there\u2019s a small chance it could hit and damage a motor that will help one of the solid rocket boosters cleanly separate from the core stage about two minutes into the flight.<\/p>\n

\u201cWe reviewed our risk acceptance rationale and our overall risk posture ,and we are setting up for a launch attempt on Sept. 3, Saturday,\u201d Sarafin said. \u201cWe\u2019re comfortable with our flight rationale and risk acceptance there.\u201d<\/p>\n

Forecasters predict a 60% chance of favorable weather during Saturday\u2019s launch window. The probability for a backup launch opportunity Monday, Sept. 5, is slightly better, with a 70% chance of acceptable weather for launch. There\u2019s also a launch opportunity available Tuesday, Sept. 6, but NASA can only use it if the launch team does not proceed into tanking of the Artemis 1 moon rocket Monday.<\/p>\n

Ultimately, the launch team called off Monday\u2019s attempt when a sensor reading on one of the four hydrogen-fueled core stage engines \u2014 Engine No. 3 \u2014 showed it was not reaching the expected cryogenic temperature during a pre-launch \u201cchilldown\u201d procedure.<\/p>\n

Engineers want the RS-25 engines to be chilled to around minus 420 degrees Fahrenheit \u2014 about the same temperature as liquid hydrogen \u2014 to be at the proper temperature for the engine startup sequence. The temperature of Engine No. 3 on Monday was around minus 380 degrees, according to sensor data, giving engineers concern that not enough super-cold liquid hydrogen was was reaching the engine through a chilldown bleed line.<\/p>\n

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Four Aerojet Rocketdyne RS-25 engines on the SLS core stage when the rocket was delivered to the Kennedy Space Center in April 2021. Credit: Stephen Clark \/ Spaceflight Now<\/figcaption><\/figure>\n

John Honeycutt, NASA\u2019s program manager for the huge SLS moon rocket, said Thursday engineers are now confident the temperature reading during Monday\u2019s countdown was erroneous, and the engines were at the correct temperature.<\/p>\n

\u201cWe have convinced ourselves, without a shadow of a doubt, that we have good quality liquid hydrogen going through the engines,\u201d Honeycutt said. \u201cThere\u2019s no fuzz on that.\u201d<\/p>\n

Honeycutt said engineers will look at five additional measurements on the engines during Saturday\u2019s countdown to assure themselves that the engines are at the right temperature, specifically moving parts like fast-spinning turbines and pumps. There\u2019s also data from the core stage itself indicating it was supplying the right amount of liquid hydrogen to the engines to chill them for ignition.<\/p>\n

\u201cWe chill engines for numerous reasons, but the primary one is for the high pressure turbopump bearing,\u201d said John Blevins, NASA\u2019s chief engineer on the SLS moon rocket. \u201cThat high pressure turbopump bearing doesn\u2019t have to be all the way as cold as the liquid, but it\u2019s got to be cold. And if we know the liquid is going through, then we know it\u2019s about that temperature.\u201d<\/p>\n

\u201cWe know we had a bad sensor,\u201d Honeycutt said. \u201cThat was our challenge early in the week, where we could not make the physics of the system line up with what we were seeing with that one sensor.\u201d<\/p>\n

The engine bleed system was not fully tested during a series of countdown rehearsals on the SLS moon rocket earlier this year. A connector associated with the bleed line leaked during a countdown test in June, and the launch team bypassed the bleed system during that rehearsal.<\/p>\n

Blevins said the launch team gains confidence about the temperature of the engines if they know the hydrogen fuel reaches the engines as a liquid, and doesn\u2019t boil off in the bleed system. If the cold liquid flows through the bleed lines for a certain of time, engineers will know the RS-25 core stage engines are at the right temperature.<\/p>\n

The Artemis 1 launch team will begin conditioning ground transfer lines for propellant loading around 6 a.m. EDT (1000 GMT) Saturday, then start flowing propellants into the rocket\u2019s core stage about an hour later. More than 750,000 gallons of liquid hydrogen and liquid oxygen will be loaded into the SLS core stage and upper stage.<\/p>\n

The \u201ckickstart\u201d bleed for the main engines will begin around 8 a.m. EDT (1200 GMT), earlier in the countdown timeline than before. The change will give more time for engine temperatures to reach the proper parameters for ignition.<\/p>\n

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This diagram illustrates the major elements of the Space Launch System moon rocket. Credit: NASA<\/figcaption><\/figure>\n

The suspect temperature sensor blamed for Monday\u2019s scrub is designed to collect engineering data to show that the engines are cooling down during the countdown. The engines also have separate \u201coperational flight instrumentation\u201d to feed data to their advanced health monitoring systems, which provide a self-check on the engine status just before ignition and in flight.<\/p>\n

The rocket\u2019s on-board computer takes control of the countdown at T-minus 30 seconds, and is designed to halt the countdown if the engines are not within the proper temperature and pressure parameters \u2014 called the \u201cstart box\u201d \u2014 before ignition. The four RS-25 engines on the core stage, all leftovers from the space shuttle program, will fire up in a staggered sequence at T-minus 6 seconds.<\/p>\n

When the countdown clock hits zero, assuming the RS-25 engines pass their automated health check, the SLS flight computer will issue the command to ignite the rocket\u2019s two side-mounted solid-fueled boosters, providing more than 80% of the thrust for the first two minutes of the flight.<\/p>\n

Each main engine\u2019s health monitoring system is designed to detect excessive vibrations in the event of a bad startup, allowing the engine to safely shut down before causing a catastrophic \u201cuncontained failure,\u201d officials said.<\/p>\n

Blevins said the engine turbopump can \u201cskid\u201d if it lights without being properly chilled.<\/p>\n

\u201cUltimately, that causes excess wear on startup,\u201d Blevins said. \u201cThat would manifest potentially as a shutdown during flight. It would be a redline. It wouldn\u2019t be an uncontained failure, generally, for that particular issue.<\/p>\n

\u201cWe have advanced health monitoring on the engines for a reason,\u201d Blevins said. \u201cThese are \u2026 really the highest horsepower per mass devices that\u2019ve ever been built. So we need that health monitoring. There are numerous things that we\u2019re looking for.\u201d<\/p>\n

The RS-25 engines each produce more than 400,000 pounds of thrust at sea level, and will fire for eight minutes to propel the SLS core stage, the upper stage, and the Orion spacecraft to more than 18,000 mph.<\/p>\n

Together, the core stage engines will consume 1,500 gallons propellant per second, enough to drain an average 20,000-gallon swimming pool in 13 seconds.<\/p>\n

Even with the changes to the countdown and decent weather odds, there\u2019s no guarantee the Artemis 1 mission will get off the ground this Labor Day weekend. That\u2019s a risk with any space mission, but there are 489 launch commit criteria NASA needs to satisfy for the launch team to be \u201cgo\u201d for liftoff of the first SLS moon rocket.<\/p>\n

\u201cWe\u2019ve got a whole host of things that could cause us to not get off on any given day, weather, range or technical, and those are the three big buckets,\u201d Sarafin said. \u201cWe talked about 489 launch commit criteria, those are the technical reasons we might not launch that day.<\/p>\n

\u201cWe might find a combination of technical issues, or somebody being out there on the range that shouldn\u2019t be out there from a public safety standpoint, and just a cloud cell or that kind of stuff could cause us to miss the opportunity,\u201d Sarafin said. \u201cThere\u2019s no guarantee that we\u2019re going to get off on the 3rd, but we\u2019re going to show up and we\u2019re going to try and we\u2019re going to give it our best.\u201d<\/p>\n

Ground teams replenished liquid hydrogen and liquid oxygen supplies at pad 39B since the launch attempt earlier this week to help set up for two more launch attempts before the moon moves out of reach for the SLS moon rocket and the Orion spacecraft. If the rocket doesn\u2019t blast off by Tuesday, the next launch period opens up Sept. 19, when the moon\u2019s position in its orbit again makes the mission possible.<\/p>\n

But NASA will have to roll the Artemis 1 moon rocket back to the Vehicle Assembly Building before then for more checks of its flight termination system, which would be used to destroy the rocket if it veered off course after liftoff.<\/p>\n

The time needed to return the rocket to the hangar, re-test the flight termination system, then roll the Space Launch System back to 39B and resume launch preps would likely push the Artemis 1 launch into October.<\/p>\n

Email the author.<\/i><\/b><\/p>\n

Follow Stephen Clark on Twitter: @StephenClark1.<\/strong><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

NASA\u2019s Space Launch System moon rocket on pad 39B. Credit: Walter Scriptunas II \/ Spaceflight Now Confident that out-of-bounds engine temperature readings during Monday\u2019s Artemis 1 countdown came from a bad sensor, NASA officials gave the green light Thursday to move forward with another try Saturday afternoon to launch the agency\u2019s giant new moon rocket […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[],"class_list":["post-11312","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/11312"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=11312"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/11312\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=11312"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=11312"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=11312"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}