Ames studies rovers' heat shield Ames studies rovers' heat shield (January 07, 2005)

Recent photos from Mars will aid future design

By Julie O'Shea

For the past year, NASA's two Mars mission rovers, Opportunity and Spirit, have been sending back extraordinary images of the Red Planet's sandy, crater-laden terrain.

Last month, however, scientists directed Opportunity to start taking pictures of something a little less alien: the crumpled heat shield that ripped apart from the spacecraft after it passed through Mars' atmosphere on Jan. 24, 2004.

The heat shield protected the rover from burning up when it entered the Martian atmosphere.

Officials at NASA Ames said they hope that by studying pictures of the heat shield, which turned inside-out when it hit the surface, they will be able to build more efficient ones for future space missions.

After studying the photos from Opportunity, NASA scientists suspect the protective heat shield had bounced just once before coming to a stop. Its impact left a crater in the planet's surface.

"Any opportunity we have to learn how well we are designing these things, we have to take it," said Bernie Laub, a project manager who conducts heat shield research at Ames.

Ethiraj Venkatapathy, a planetary technology manager at Ames, said the rover's heat shield did its job successfully. What engineers want to know now is whether there is a way to make planetary heat shields lighter, Venkatapathy said.

At 8 feet and 90 kilograms, the Mars heat shield comprised 10 percent of the rover spacecraft's total weight. Venkatapathy said engineers might have over-designed the shield. But, he added, it is better to be safe than sorry.

"The heat shield is one of those components that has no backup," Venkatapathy said. "(It) only gets one chance. If it fails, the whole mission comes to a standstill."

NASA officials said they want to find a balance between science and safety. Engineers are studying ways they can shave some of the weight off the shield so that future missions to Mars can carry more scientific instruments onboard.

"One kilogram we can take from the heat shield is one kilogram more for science," Venkatapathy said.

The pictures the Opportunity rover is beaming back over 500 million miles of space marks the first time NASA has examined a successful planetary heat shield up close.

The next Mars mission, named Phoenix, is scheduled for 2007. Ames scientists said this mission will use the same heat shield material that was used to protect Opportunity and Spirit. However, another mission set for 2009 will be using a rover much larger than the ones currently exploring Mars.

"It will be much more capable," said Laub. "It will go for miles and miles and miles and miles."

Because the 2009 mission rover will be bigger, the heat will be much more intense when the craft enters Mars' atmosphere, Laub said. And engineers responsible for building the heat shield must decide which kind of material should be used for that trip.

When Opportunity and Spirit broke through Mars' atmosphere last year, they were traveling at 1,200 mph. Outside, the temperature was at least 2,700 degrees Fahrenheit. But the heat shields kept the crafts below 200 degrees. The rovers slowed to about 200 mph in less than four minutes after entering Mars' atmosphere.

E-mail Julie O'Shea at joshea@mv-voice.com

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