Friday, May 15th, 2009
Students from Texas A&M recently traveled to the NASA Ames Research Center in Moffett Field, Calif., in order to design a spacecraft able to derail an asteroid from a collision course with Earth.
Professional engineers from the Ames Mission Design Center helped student engineers define a convergent design of a mission that could explore and deflect the asteroid Apophis.
The near earth asteroid (NEA) Apophis was discovered in 2004. At the time, it raised alarm, as many predicted that it could hit the Earth as soon as 2029. It was classified as high as a 4 on the Torino scale, much higher than any other celestial object. It was determined that an impact in 2029 would not occur; however, the asteroid could still crash into Earth in 2036.
Dr. David Hyland of Texas A&M University began work on an exploration mission to the asteroid Apophis in 2006. The students in three courses offered by Hyland designed APEP, the Apophis Preliminary Exploratory Platform. This mission was meant to just explore Apophis and track its movements. The end result would be a decision on whether or not the asteroid had a high chance of colliding with Earth.
In fall of 2008, the Deflect Apophis System (DAS) was designed by students in another class led by Hyland, AERO 426. The objective of the DAS was to move Apophis such that it would not collide with Earth.
The Apophis Exploration and Mitigation Platform (AEMP) is the current project, which involves a combination of both APEP and AEMP. First, the AEMP would stand some distance away from Apophis, taking of all of the necessary science measurements needed to deflect the asteroid. Then, it would employ a “gravity tractor” to begin movement. After a year, an “albedo change” substance would be adhered to the asteroid, forcing long term movement.
Pending ongoing discussions, AEMP may soon be a three-way partnership involving Texas A&M, NASA Ames and the Kingdom of Saudi Arabia, through King Abdulaziz City for Science and Technology.
The exploration part of the mission would help determine the physical characteristics necessary in order to perform the two mitigations methods. Some characteristics that would be targeted would be mass, size and which direction it is spinning.
A “gravity tractor” is a spacecraft that uses the mutual attraction between all bodies as a method of movement. Over time, the asteroid and spacecraft will slowly move towards each other. If the spacecraft is propelled away from the asteroid, then the asteroid will be moved towards the spacecraft. This effect is only useful if it is used over a long time.
The concept of changing the albedo of an asteroid is a technique that is unique to Texas A&M. No other organization has designed a mission meant to use the manipulation of albedo as a way to move an asteroid. The albedo of an object is a measure of how reflective it is. The more reflective, the less heat it absorbs, and the less heat it emits as it cools. When the heat is emitted, a small force is created on the object. If the asteroid’s albedo is changed, this force can be manipulated to move Apophis over a long period of time.
A gravity tractor is only effective for as long as the spacecraft has propellant. On the other hand, modifying the albedo of the asteroid would be a permanent change, effective essentially forever. In the case of Apophis, the gravity tractor would be used to mitigate the immediate threat of 2036. The albedo modification would slowly push Apophis further and further away, meaning it would never impact the Earth.
While the asteroid Apophis may not be considered a threat to Earth, dozens of asteroids on Earth-crossing paths have been found. Should such an asteroid threaten to impact Earth, there is no currently well-developed plan for a way to divert it. Dr. Hyland and the students of Texas A&M involved in the project are suggesting this three stage process as a template for diverting all asteroids, using Apophis as an example.
