Tag Archives: NASA

Where are AREE Rovers Going?

NASA is planning new types of rover explorers for observing extreme environments, such as the surface of Venus. They plan to build simple yet robust vehicles. AREE is their acronym for Automaton Rovers for Extreme Environments.

NASA’s Curiosity Rover on Mars has been roving and exploring the planet’s surface for the last five years. Among rovers, Curiosity is at the top position. It uses special systems for rejecting heat, X-band receiver and transmitter for communicating directly with Earth, an Electra-Lite radio (UHF) for communicating with the Mars Orbiters, instruments for mineralogy and chemistry, instruments for simple analysis, and much more.

According to Jason Derleth, NASA prefers to do the absolute maximum when sending a rover into space, such as making sure the rover can contribute as much to science as is possible. Jason is the head of NASA’s Innovative Advanced Concepts Program (NIAC).

However, Venus is vastly different from Mars. Although very similar to Earth in its size, mass, and density, Venus has an incredibly thick atmosphere—a mix of carbon dioxide, nitrogen, and sulfur dioxide. This raises the temperature on the surface of Venus to over 450°C, which is hot enough to melt lead or high enough for paper to spontaneously combust. The atmospheric pressure at the surface is 92 bar or 1,334 psi, with a density enough to crush a submarine.

In the past, some robots have succeeded in reaching Venus. These were the Soviet Union’s Venera and Vega landers, and the Pioneer probe from NASA. Although they were successful in reaching the planet’s surface, they could function only between 23 and 127 minutes before the oppressive environment snuffed out their electronics.

With the AREE rovers, NASA is trying a new concept, inspired by mechanical clockwork computers and tanks used in World War I. A NASA program, NIAC, is funding the AREE rovers. It is offering small grants for developing early stage technology, which allows engineers to work on long-term ideas for properly developing the technology.

For instance, the most recent funding from NASA related to the development of a rough prototype of the rover concept, which will take about three years. Jonathan Sauder was the first to propose the concept. In 2015, Sauder had observed mechanical computers using levers and gears for performing calculations rather than rely on electronics.

The AREE rovers would be using these analog techniques mainly to survive the harsh environments on Venus. They would traverse the planet’s surface moving on tank treads that overcame the rough terrain. As wind gusts on Venus are high, they would turn wind turbines located at the center of the rover to supply it with the necessary power. The robot would capture the power from the turbines inside springs before distributing it to the other subsystems of the robot. Think of a windup watch, the idea is very similar.

Curiosity has several cameras to measure, map, and guide it over the Marian terrain. However, the electronic functionality of the AREE rovers will be purposely kept simple. Although AREE’s design will make it robust enough to withstand unexpected bumps and drops, it will integrate a simple optical reflector to transmit data to the orbiting satellite.

Why do Speakers use Ferro-fluids?

Speakers reproduce sound by moving a diaphragm to displace air. The mechanism resembles a permanent magnet electric motor. The major difference is the voice coil in a speaker moves linearly instead of in a circular motion. As the coil moves back and forth in step with the electrical signals fed to it, it moves the attached diaphragm. To prevent spurious movements and unwanted oscillations of the diaphragm, conventional speakers generally use a damper. To produce sound from such speakers, extra energy is necessary to overcome the resistance of the damper.

Additionally, the damper has its own natural frequency of vibration that restricts the speaker from reproducing sound accurately at all frequencies. A new technique using a magnetic fluid to replace the damper claims to correct this anomaly by reducing energy consumption and allowing louder and clearer sound across the entire range of frequencies the speaker is capable of reproducing. To quantify the advantages, the new speaker reduces energy consumption by 35% for reproducing the same loudness of sound as from conventional speakers and the improvement in sound quality is nearly 3dB.

NASA originally developed the magnetic fluid in the 1960’s, using it for space exploration and called it Ferro-fluid. It responds to applied magnetic fields because the fluid is infused with Nano-sized magnetic particles. They do not agglomerate or cluster together because of a coating of suitable surfactants. The unique characteristic of ferro-fluids makes them useful in a range of applications. Using applied magnetic fields to control flow or movement, ferro-fluids can replace mechanical parts such as vehicle suspensions, flow of fuel in a reactor and more.

In a conventional speaker, the damper holds several components such as the diaphragm and spring in place, even when the speaker is vibrating. However, the damper causes friction while moving, thereby distorting the original sound waves with secondary vibrations, which are manifest as noise. To overcome the friction requires additional energy while driving and that reduces the speaker’s total volume output by a few decibels.

When replacing the damper in a speaker, the ferro-fluid used has a thickness of only a few microns. The magnets of the speaker create a permanent magnetic field to which the ferro-fluid responds by holding the diaphragm and the coil in place while allowing them to move linearly without any friction. As there are no secondary vibrations from the ferro-fluid, the sound is clearer. The lack of friction allows the speaker to save about 35% of the energy as compared to conventional speakers with dampers.

Ferro-fluids used for the audio field are usually based on two classes of carrier liquids – synthetic enters and hydrocarbons. Both oils are low in volatility and high on thermal stability. The environmental considerations dictate the choice of the fluid used, along with the best balance of viscosity values and magnetization for optimizing the acoustical performance.

Using different carrier liquids and by varying the quantity of magnetic material in the ferro-fluid, it can be tailored to meet different needs. The saturation magnetization depends on the nature of the suspended magnetic material and its volumetric loading. Care is taken to use material whose density and viscosity correspond closely to that of the carrier fluid.