Second Try Sunday for Parker Solar Probe – UPDATE

Second Try Sunday for Parker Solar Probe – UPDATE

NASA will try again to launch the Parker Solar Probe on Sunday morning at 3:31 am ET.  The first attempt was scrubbed this morning 1 minute and 55 seconds before launch because of a “gaseous helium red pressure alarm” in the United Launch Alliance (ULA) Delta IV Heavy rocket.  ULA later confirmed that another attempt will made Sunday.  The weather forecast, however, is only 60 percent “go.” [UPDATE, AUGUST 12:  Liftoff took place at 3:31 am ET on Sunday, August 12.]

Much of the 65-minute launch window, which opened at 3:33 am ET, had already elapsed due to earlier anomalies.  When this problem cropped up, ULA did not have sufficient time to troubleshoot it before the end of the window.

At the time of the scrub, NASA said the next attempt would be tomorrow (Sunday), but that was tentative pending resolution of the problem.  ULA President and CEO Tory Bruno later tweeted that ULA is good to go.

The Parker Solar Probe is named after Dr. Eugene Parker, the father of heliophysics, the science of studying the Sun and its interactions with the Earth and the rest of the solar system.  It will fly closer to the Sun than any other spacecraft — 3.8 million miles from the Sun’s surface — and spend a great deal of its time in the Sun’s corona.  NASA calls this “touching” the Sun.

Artist’s illustration of the Parker Solar Probe. Credit: NASA

NASA and project officials said in pre-launch briefings Thursday that this mission has been waiting for the technologies to enable it. Project scientist Nicola Fox of the Johns Hopkins University Applied Physics Lab said “This is a mission that has been in the making for 60 years.  We had to wait so long for our technology to catch up with our dreams.”

One of those technologies is the spacecraft’s carbon composite heat shield. JHUAPL project manager Andy Driesman said in the past a heat shield capable of protecting the spacecraft and its instruments would have been made of metal. That would be too massive to launch. By contrast, the heat shield on Parker Solar Probe is a carbon composite foam sandwiched between two carbon plates made of carbon. It is only 4.5 inches thick and weighs just 160 pounds.  The heat shield was developed by a team led by Betsy Congdon at JHUAPL, which produced a video explaining its design.

The spacecraft will make seven loops around Venus to get gravity assists that place it into the correct orbit around the Sun.  Over its 7-year mission, it will make a total of 24 orbits, but Driesman said he hopes to get an extension so it can operate until its fuel runs out.  On the last of its planned orbits it will reach a speed of 430,000 miles per hour, the fastest-ever human made object according to NASA.

Asked what will happen to the probe after its science mission is done, Driesman said the probe eventually will break into pieces. He likes to think of what remains after 10-20 years will be a carbon disk that will float around the Sun until the end of the solar system.

NASA issued a broad invitation to the public to send their names to the Sun aboard the probe on a memory card. More than 1.1 million people responded.  Asked what will happen to those names, Fox said she believes the spacecraft will become a dust cloud around the Sun so “your name will orbit the Sun forever.”

In 1958, Parker was the first scientist to theorize that the Sun creates a “wind” of particles and magnetic fields that expands outward through the solar system — the solar wind.  Angela Olinto, dean of the Division of the Physical Sciences at the University of Chicago, where Parker is on the faculty, wrote in the Wall Street Journal this week that Parker’s theory “found only doubters” at the time.  He did not waver, however, and four years later was “vindicated” when NASA’s Mariner 2 probe confirmed the solar wind’s existence.  “Great advances in science often stem from a willingness to challenge convention,” Olinto continued. “At 91, Mr. [sic] Parker still loves the unexpected. Discussing the solar probe recently, he said that ‘we have to be prepared for some surprises–things that we never thought of, or things that we thought of but were not correct.'”

Parker is the first living person to have a spacecraft named after him.  He is at Cape Canaveral for the launch.  NASA Associate Administrator for Science Thomas Zurbuchen, also a heliophysicist, posted this photo taken at Cape Canaveral Air Force Station Launch Complex 37 of himself (left), Parker (center),and ULA’s Bruno (right).

NASA TV will cover Sunday’s launch attempt beginning at 3:00 am ET.

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