NASA’s HAMMER will destroy Asteroid Bennu approaching Earth and prevent future collision
NASA is preparing for a nuclear attack, not on Earth, but on a large asteroid that has some chances of colliding with Earth in future. The asteroid, named Bennu, has a 1 in 2,700 chance of crashing to Earth on September 21, 2135. So, NASA is planning to destroy this potentially dangerous asteroid through nuclear bombing before it reaches our Earth.
Although the chances of Bennu asteroid hitting Earth is negligible, still, NASA wants to ensure that the potential threat is neutralized well in advance. NASA scientists are not thinking of directly destroying the asteroid. They are of the notion that if the asteroid is found to coming too close to earth, then it should be destroyed with nuclear bombs to ensure the safety of Earth. Currently, Bennu is orbiting the Sun at about 54 million miles away from Earth. The asteroid is about 1,600 foot wide and weighs around 74 billion pounds.
The asteroid Bennu will come very close to Earth in September 2135 and NASA scientists predict that there might be a chance of collision of the asteroid with Earth. So, NASA along with the National Nuclear Security Administration, and two Energy Department weapons labs are planning to design and develop a spacecraft called HAMMER. HAMMER stands for Hypervelocity Asteroid Mitigation Mission for Emergency Response.
NASA believes that through HAMMER spacecraft it would be able to deliver nukes to the asteroid. The scientists are thinking of two ways in which they can obstruct Bennu from coming very close to Earth. If the asteroid is found to be small enough, then the HAMMER spacecraft will use an 8.8-ton “impactor” to smash the asteroid. If the asteroid is found to be massive, then the HAMMER will destroy it with nuclear bombs before it reaches Earth.
Physicist David Dearborn from the Lawrence Livermore National Laboratory is thinking a different plan which does not need any nuclear bombing. Dearborn suggested that the asteroid could be slowed down and its course could be changed by bombarding it with multiple HAMMER crafts. The HAMMER mission concept is not a new thing, as the idea was earlier introduced in a 2010 report published in the journal Acta Astronautica. The report stated that 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. Well, the future of HAMMER project is uncertain and NASA is currently focusing on its OSIRIS-Rex mission that is on its way to Bennu to collect samples and bring them back to Earth.
According to the US space agency NASA, OSIRIS-REx is continuing outbound cruise operations, en route to arrive in December of 2018 at the asteroid Bennu, with approach operations starting in August. The spacecraft is currently 29.6 million miles (47.6 million kilometers) from Earth and is executing a program designed to study and reduce the presence of water on the spacecraft.
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. Retention of water in blanketing and other materials – and the subsequent outgassing of this water – occurs with all spacecraft. For OSIRIS-REx, it was determined that when the SRC was exposed to the Sun at a distance of less than 1 Astronomical Unit (1 AU = approximately 93 million miles), this trapped water escaped and imparted a small thrust. While this small thrust would not be a problem for other missions, the gravity at the target asteroid Bennu is low enough that even this small amount of thrust could make orbital operations more difficult for OSIRIS-REx.
To better understand the outgassing effects on the spacecraft’s trajectory – and to bake out much of the remaining water before the spacecraft arrives at Bennu – the OSIRIS-REx mission team designed an outgassing program for execution starting earlier this fall. The choice of timing took into account both the spacecraft’s proximity to the Sun (less than 1 AU) and the fact that there were no science activities planned during this period. The outgassing program is being run concurrently with outbound cruise operations and does not affect the timing of the spacecraft’s arrival at Bennu.
Starting in mid-October, the spacecraft has been placed into various attitudes to expose different parts of the SRC to direct sunlight and initiate outgassing. Priority is given to the portions of the SRC that will face the Sun during asteroid proximity operations. The mission team has been able to detect and measure the rate of outgassing at each attitude and has determined that water is being removed as expected. The goal is to reduce the outgassing to the point where the spacecraft can fly the planned baseline trajectories around Bennu without modifications, and preliminary indications show that the program is progressing toward this goal. The program is scheduled to run through early January 2018.
101955 Bennu (provisional designation 1999 RQ36) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on September 11, 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table with the third-highest rating on the Palermo Technical Impact Hazard Scale, due to a cumulative 1-in-2,700 chance of impacting Earth in the late 22nd century. It is the planned target of the OSIRIS-REx mission which is intended to return samples to Earth in 2023 for further study.
Asteroid Bennu has a roughly spheroidal shape, which resembles a spinning top. The direction of rotation about its axis is retrograde with respect to its orbit. Bennu has a fairly smooth shape with one prominent 10–20 m boulder on its surface, in the southern hemisphere.
There is a well-defined ridge along the equator of asteroid Bennu. The presence of this ridge suggests that fine-grained regolith particles have accumulated in this area, possibly due to its low gravity and fast rotation.
Observations of this minor planet by the Spitzer Space Telescope in 2007 gave an effective diameter of 484±10 m, which is in line with other studies. It has a low visible geometric albedo of 0.046±0.005. The thermal inertia was measured and found to vary by ±19% during each rotational period. The data suggest that the regolith grain size is moderate, ranging from several millimeters up to a centimeter, and evenly distributed longitudinally. No emission from a potential dust coma has been detected around asteroid Bennu, which puts a limit of 106 g of dust within a radius of 4750 km.
On average, an asteroid with a diameter of 500 m (1,600 ft; 0.31 mi) can be expected to impact Earth about every 130,000 years or so. A 2010 dynamical study by Andrea Milani and collaborators predicted a series of eight potential Earth impacts by Bennu between 2169 and 2199. The cumulative probability of impact is dependent on physical properties of Bennu that were poorly known at the time, but was not found to exceed 0.071% for all eight encounters. The authors recognized that an accurate assessment of 101955 Bennu‘s probability of Earth impact would require a detailed shape model and additional observations (either from the ground or from spacecraft visiting the object) to determine the magnitude and direction of the Yarkovsky effect.
The publication of the shape model and of astrometry based on radar observations obtained in 1999, 2005, and 2011, made possible an improved estimate of the Yarkovsky acceleration and a revised assessment of the impact probability. The current (as of 2014) best estimate of the impact probability is a cumulative probability of 0.037% in the interval 2175 to 2196. This corresponds to a cumulative score on the Palermo scale of −1.71. If an impact were to occur, the expected kinetic energy associated with the collision would be 1200 megatons in TNT equivalent.
