Ares I-X Launch Scrub: Can You Say Triboelectrification?

by Nancy Atkinson on October 27, 2009

NASA's Ares I-X rocket is seen on Launch Pad 39B at NASA's Kennedy Space Center. Photo Credit: NASA/Bill Ingalls

NASA's Ares I-X rocket is seen on Launch Pad 39B at NASA's Kennedy Space Center. Photo Credit: NASA/Bill Ingalls

The test flight for the Ares I-X rocket was scrubbed on Tuesday after a roller coaster of repeated delays which included weather, a stuck cover on a probe, a cargo ship straying into the launch hazard zone, weather, and weather. “We had some opportunities, but just couldn’t get there,” launch test director Ed Mango said to the team. “Weather didn’t cooperate.” The biggest issue with weather was the launch commit criteria of avoiding possible static discharge called “triboelectrification” created by the outer coating of the rocket rubbing against cloud vapor or precipitation that is colder than -10 degrees C (14 deg. F). This static electricity could disrupt the transmission of flight test data from the rocket, and getting data is one of the main desired outcomes for the test flight.

Another 4-hour launch window opens at 8 am EDT (1200 GMT) on Wednesday.

The 5-hole probe on the top of the Ares I-X rocket. Credit: NASA

The 5-hole probe on the top of the Ares I-X rocket. Credit: NASA

On Tuesday, when the weather improved enough to remove the 5-hole probe cover, then came a problem with removing it. This difficulty was not anticipated.

“After hundreds of tests with the probe, that’s the first time we’ve seen that failure mode,” said NASA engineer Jon Cowart on NASA TV. On Twitter, a NASA engineer shared that they gave the pad crew the recommendation to pull the lanyard attached to the cover “as hard as you can.” It worked.

Then came a cargo ship that entered the hazard area in offshore waters. The ship was notified and it turned around quickly.

But by that time the weather had deteriorated. Good on their word that they could quickly restart the countdown clock, the launch team tried several times to coordinate a hole in the clouds with acceptable (less than 20 knots) ground and upper level winds. It was a roller coaster of “go” and “no-go,” but ultimately the weather cards never fell into the fight configuration to allow the launch to take place.

Tomorrow the weather is better but not great. The chance of unacceptable conditions drops to 40% no go for Wednesday, as opposed to 60% no go today. Forecasters predict somewhat quieter winds at ground level, upper level winds are expected to be lighter and clouds will be decreasing, with more breaks in the clouds.

The test flight will last six minutes from liftoff to splashdown, with the Ares I-X reaching a maximum altitude of 46,000 m (153,000 feet) and a top velocity more than 4.7 times the speed of sound.

And if you are still wondering about triboelectrification, it basically is static electricity such as what you might encounter when you rub a balloon on your shirt, or rub your feet on a dry carpet or brush up against a cat and then touch a metal surface. Zap!

In the case of Ares I-X, flying through high-level clouds can generate “P-static” (P for precipitation), which can create a corona of static around the rocket that interferes with radio signals sent by or to the rocket. This would create problems when the rocket tries to transmit data down to the ground or if the Range Safety Officer at Cape Canaveral Air Force Station needed to send a signal to the flight termination system (a.k.a. blow up the rocket because of a big problem.)


Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

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