posted 02-20-2023 10:08 AM               

quote:

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Originally posted by GACspaceguy:
For me it sounded just like a Shuttle launch...

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The roar and crackle of Artemis I

Measurements taken at locations around the launch pad revealed noise levels as high as 136 decibels from 1.5 km away

When the Artemis I mission was launched by NASA's Space Launch System, SLS, in November, it became the world's most powerful rocket, exceeding the thrust of the previous record holder, Saturn , by 13%. With liftoff came a loud roar heard miles away.

In JASA Express Letters, published on behalf of the Acoustical Society of America by AIP Publishing, researchers from Brigham Young University and Rollins College in Florida reported noise measurements during the launch at different locations around Kennedy Space Center.

The data collected can be used to validate existing noise prediction models, which are needed to protect equipment as well as the surrounding environment and community. These data will be useful as more powerful lift vehicles, including the SLS series, are developed.

"We hope these early results will help prevent the spread of possible misinformation, as happened with the Saturn V," author Kent Gee said. "Numerous websites and discussion forums suggested sound levels that were far too high, with inaccurate reports of the Saturn V's sound waves melting concrete and causing grass fires."

The combination of nighttime darkness, humidity, and backlighting provided a rare opportunity to view propagating pressure waves, which can be seen in the accompanying video.

Artemis I was launched with four liquid hydrogen-oxygen engines plus two solid-fuel rocket boosters (SRBs). According to the authors, the SRBs are likely the dominant noise source during liftoff.

The investigators studied recordings at microphones located 1.5 km to 5.2 km from the launch pad. All stations were outside the blast danger area. Maximum noise levels at all five stations exceeded those predicted in a preliminary assessment.

At 1.5 km from the pad, the maximum noise level reached 136 decibels. At a 5.2 km distance, the noise was 129 decibels, nearly 20 decibels higher than predicted by a prelaunch noise model.

"This suggests a need to revisit and probably revise those models," author Grant Hart said.

A procedure known as A-weighting is often used to assess the impact of noise on humans. Because we don't hear as well in some frequency ranges as others, a filter is applied to emphasize the sounds we do hear. Using this method, the investigators found noise levels at 5.2 km from the launchpad were about as loud as a chainsaw.

A characteristic feature of rocket launches is a crackling sound from shock waves. These shocks represent instantaneous sound pressure increases that are much louder than crackling noises encountered in everyday life.

Author Whitney Coyle said, "We found the Artemis I noise level at 5 km had a crackling quality about 40 million times greater than a bowl of Rice Krispies."

"Although this study is an important step forward, we still have a long way to go to understand everything about the generation, propagation, and perception of rocket noise," Gee said.

posted 02-20-2023 10:30 AM            

As a matter of interest, do we have reliable figures for the decibel-levels at launch of the N1?

posted 02-25-2023 11:24 AM               

The SLS is also beautiful but it looks something like a work in progress. Splotchy paintwork, exposed plumbing and equipment that appears to have been added on as an afterthought.

But for all that it's still amazing. It's a knockout.

posted 03-04-2023 07:50 AM               

While the space shuttle was light enough that the ignition of the three main engines set the vehicle into motion — necessitating a hold-down system until SRB ignition — SLS is heavy enough that the only thing holding down the vehicle on launch day is gravity.

posted 04-14-2023 04:10 PM               

• Mobile Launch Tower
  
• Tracking Cameras
  
• Mobile Launcher (ML) Deck
  
• Perimeter Cameras
  
• Perimeter Cameras
  
• Launch Pad Cameras

posted 11-16-2023 11:40 AM               

At 1:47 a.m. EST (6:47 UTC) on Nov. 16, 2022, NASA's Orion spacecraft launched atop the SLS (Space Launch System) rocket from historic Launch Pad 39B at NASA's Kennedy Space Center in Florida on a path to the Moon, officially beginning the Artemis I mission.

Over the course of 25.5 days, Orion performed two lunar flybys, coming within 80 miles (129 kilometers) of the lunar surface. At its farthest distance during the mission, Orion traveled nearly 270,000 miles (435,000 kilometers) from our home planet. On Dec. 11, 2022, NASA's Orion spacecraft successfully completed a parachute-assisted splashdown in the Pacific Ocean at 9:40 a.m. PST (12:40 p.m. EST) as the final major milestone of the Artemis I mission.

Artemis I set new performance records, exceeded efficiency expectations, and established new safety baselines for humans in deep space. This is a prelude to what comes next—following the success of Artemis I, human beings will fly around the Moon on Artemis II.

We have demonstrated our ability to go farther and faster than ever before, opening the door to explore Mars and other destinations throughout the solar system. This is the story of Artemis I.

posted 10-29-2024 10:29 AM               

In the months after the Orion spacecraft returned to Earth on the uncrewed Artemis 1 mission in December 2022, NASA disclosed there had been more "char loss" on the ablative heat shield at the base of the capsule than expected. That did not pose a risk to the spacecraft itself, but agency officials said they wanted to understand what happened to prepare for Artemis 2, the first crewed flight of the spacecraft.

NASA has provided few specifics about that investigation, and the only images of the heat shield itself came in a report by the agency's inspector general in May.

At an Aug. 29 meeting of the NASA Advisory Council's human exploration and operations committee, Amit Kshatriya, deputy associate administrator for the Moon to Mars Program, said an independent review team has completed its analysis of the heat shield erosion but did not provide additional details.

Asked about the status of the heat shield at an Oct. 28 meeting of the Lunar Exploration Analysis Group (LEAG) in Houston, Lori Glaze, acting deputy associate administrator in NASA's Exploration Systems Development Mission Directorate, said those reviews had determined what caused the additional char loss.

"We have conclusive determination of what the root cause is of the issue," she said. "We have been able to demonstrate and reproduce it in the arc jet facilities out at Ames." The Arc Jet Complex at NASA's Ames Research Center can reproduce the heating conditions seen on reentry.

However, she declined to identify what that root cause is. "I'm not going to share right now," she said when asked about it. "When it comes out, it will all come out together."