Sandeep Shah: Materials and Manufacturing Engineer
I came to America to attend graduate school. People in my native country -- India -- admired American universities, so it was an honor to receive a scholarship to one to work on my PhD. I had already earned my bachelor's degree in metallurgy from the Indian Institute of Technology. Metals and their uses have always intrigued me. While earning my doctorate degree, I studied metals called aluminum-lithium alloys, which are light, strong materials ideal for building rockets.
After graduation, an aerospace contractor hired me to work on the super-lightweight external tank for the space shuttle. My schooling in aluminum-lithium alloys came in handy! My team helped make the new external tank out of aluminum-lithium alloy 2195, reducing the tank's weight by 7,500 pounds. The lighter tank allows the shuttle to carry heavier payloads, such as large parts of the International Space Station and science payloads.
The super-lightweight tank's metal skin is less than one-half-inch thick, yet it absorbs most of the 7 million pounds of thrust produced at liftoff. It holds more than 1.6 million pounds of propellants, enough to fill 29 swimming pools. This material amazes me. It can withstand fractures even when it's cooled to -423 degrees Fahrenheit -- the temperature for storing liquid hydrogen propellant used by rockets. That's three times colder than the coldest temperature ever recorded on Earth.
In my current job, I am a materials and manufacturing engineer at Marshall. I identify the best materials and determine how to manufacture large rockets -- taller than 30-story buildings -- and make them safe enough to carry people and cargo farther and faster.
One of the techniques we have pioneered is friction stir welding. Welds are often the weakest parts of a rocket because they are more prone to cracks or defects than are other parts of the rocket. Each space shuttle external tank has one-half mile of welds, and it's critical that these welds be strong and durable. Traditional welding, called fusion welding, heats metals to high temperatures. Instead, friction stir welding uses friction to bring metals to a butter-like consistency and blend them together. Tanks built with fusion welding usually require several repairs, which take time and money. Space shuttle tanks welded with friction stir welding have only had to have a few repairs.
Now, my team is using friction stir welding and everything else we've learned over the last 50 years to create a manufacturing and assembling plan for the next-generation of rockets. We've identified and tested the best materials. Factories across the country make the rocket parts and supply them to NASA. In our advanced manufacturing areas, we use room-size robotic welding machines to join the pieces and build fuel tanks and other key rocket components.This is how we perfect the way we build rockets and other spacecraft so that they are more affordable, yet still safe. This research is valuable not only to NASA, but also to companies that build rockets.
Building a safe launch vehicle means everything to me. I helped investigate materials failures during the Space Shuttle Columbia accident that killed seven crewmembers in 2003. I spent months at Kennedy Space Center working with other people from across NASA. As we laid out the pieces of the recovered vehicle, we worked like detectives to uncover the story the materials could tell us about why the accident happened. I will never forget this or the astronauts we lost.
I will continue striving to understand how to build the safest, most reliable rockets. I also want the U.S. to work with other countries to explore space. Recently, India sent the Chandrayann-1 mission to the Moon, and Americans joined in the research by putting some of their own instruments on the flight. I would love to be involved in international partnerships like this one aimed at exploring the solar system.