Traveling Farther
Every time we travel, we learn more about the world around us. Columbus helped us travel farther as he set out in new waters and discovered the Americas. The Wright brothers helped us go farther by opening up the possibility that we could travel upwards toward the skies if only we could develop the right technologies. We now know that we can travel to space, but we have learned that we are just a small dot in the vast universe that has yet to be explored.
Structural dynamics plays a key role in the design of systems for traveling farther into space. Because the cost to launch a payload is proportional to the mass and volume, space structures are designed to be very lightweight and to be packed into a small volume. After reaching orbit, the structure is deployed into its operational configuration. For example, solar panels that provide electrical power to satellites are stowed for launch and are then “unfolded” to be exposed to sunlight.
Understanding structural dynamics is critical to developing the technologies that will allow us to explore our universe. See some of the technologies that got us to where we are today and learn about some developing technologies that promise to take us farther.
Moon/Mars Landing
Stepping out of Earth’s atmosphere into the vastness of space was amazing, but in July of 1969 we traveled farther yet again to land on the surface of the Moon. The Apollo 11 Command Module “Columbia” carried astronauts Neil Armstrong, Edwin “Buzz” Aldrin, and Michael Collins on their historic voyage to the Moon and back on July 16-24, 1969. This mission culminated in the first human steps on another world.
The design of the Lunar Module was a challenging engineering feat because the structure had to withstand impact for ascent from the moon’s surface. The system also had to be dynamically stable in its many configurations: separating from the Command Service Module, landing, ascending, and maneuvering for docking.
Now, scientists and structural engineers are designing launch vehicles and spacecraft to return man to the moon. Robotic missions are exploring the surface of Mars. Spacecraft are collecting data on other planets and their moons. Information from use of these systems will help in the design of vehicles for manned missions to Mars — and beyond.
Just as the sail opened up a world of adventures for nautical explorers, the same theory of sailing is now being applied to future spacecraft for the purpose of exploring our galaxy. Research is now underway to develop a new kind of sail — a solar sail.
Solar sails are composed of large flat smooth sheets of very thin film, supported by ultra-lightweight structures. The side of the film that faces the sun is coated with highly reflective material so that the resulting product is a huge mirror, typically about the size of a football field. Due to the size of the sails, it exhibits non-linear dynamic behavior that we need to fully understand to design effective and robust sails.
The force generated by the sun shining on the sail’s surface is about equal to the weight of a letter sent via first class mail (less than 2 ounces). Even though this a very tiny force, it is perpetual and over days, weeks, and months, this snail-paced acceleration results in the achievement of high velocities. So high, in fact that the solar sail may actually pick up enough speed to leave our solar system traveling farther than we have ever traveled before.
Solar Sail
Redstone Rocket
The Redstone Rocket took us farther than we had been before as the first American vehicle to travel outside Earth’s atmosphere. On January 31, 1958, a modified four-stage Restone rocket, known as Jupiter-C, lifted the first American satellite, Explorer I, into orbit. The Redstone made headlines again May 1961, when it launched the first American, astronaut Ala Shepard, into space. The Redstone gave us our first glimpse into a future of manned space exploration.
A rocket engine is one of the best examples of a structure that has to withstand substantial and sustained dynamic loading. In addition, because the weight of anything launched into space must be kept as low as possible, the structure cannot be over-designed to be able to withstand these loads; so all analysis must be as accurate as possible. The application of the discipline of structural dynamics to the design, analysis and test of rocket engines is therefore critical to their success.