The Hypervelocity Asteroid Mitigation Mission for Emergency Response (HAMMER) project is an ambitious plan, developed by NASA, designed to deflect or divert potentially hazardous asteroids before they strike Earth. Smaller objects would be targeted by the spacecraft itself, acting as a massive non-explosive projectile, while larger objects could be hit with nuclear weapons.
Destroying an incoming asteroid could be more dangerous than facing a single impact, since the rubble left behind could create a tremendous number of impactors, capable of landing over a large area of our planet, spreading damage over a large area, similar to the effect inflicted by a shotgun. Therefore, the preferred means of eliminating the threat is to divert a near-earth object (NEO) before it could become an eminent threat.
“The two realistic responses considered are the use of a spacecraft functioning as either a kinetic impactor or a nuclear explosive carrier to deflect the approaching NEO. The choice depends on the NEO size and mass, the available response time prior to Earth impact, and the various uncertainties. Whenever practical, the kinetic impactor is the preferred approach,” investigators wrote in a journal article outlining their plan.
The vehicle, weighing 8.8 tons, would be capable of impacting into a smaller NEO, or triggering a nuclear blast near a large one, in an attempt to divert the orbit of the object.
The asteroid BENNU, discovered in 1999, has a small chance of striking our planet on September 21, 2135. Due to the potential this object has of hitting Earth, HAMMER researchers are using this object as a case study of how such NEO’s could be deflected by a defensive spacecraft. The OSIRIS-Rex vehicle was launched to BENNU in 2016, where it will arrive in December of 2018. Once there, it will collect material from the surface of the object, which will be returned to Earth inside a Sample Return Capsule (SRC). Heating of the SRC from the Sun is resulting in a slight change to the path of OSIRIS-Rex as it heads toward its target.
“During routine in-flight testing of the spacecraft’s thermal properties earlier this year, the mission’s navigation team noticed an unexpected minor acceleration of the spacecraft when the Sample Return Capsule (SRC) was exposed to sunlight. The mission team determined that this small thrust was caused by the outgassing of water that had been adsorbed by the SRC’s heat shield and backshell before launch,” NASA officials reported.
Astronomers estimate the BENNU asteroid would weigh over 85 million tons if it were on Earth. If this asteroid were to strike our planet, it could explode with a force of over one billion tons of TNT.
Numerous forces affect objects, like asteroids, as they orbit around the Sun. Every planet and large asteroid alters the orbit, as does the solar wind, emanating from our parent star. In addition, heating on the body, which can result in outgassing, or the release of gases from the frozen surface.
The HAMMER plan was developed by researchers from NASA, together with the National Nuclear Security Administration, and weapons labs working under the Energy Department for the United States.