Giant asteroid vesta
NASA undated handout image obtained by the framing camera on the Dawn spacecraft shows the south pole of the giant asteroid Vesta. Scientists are discussing whether the circular structure that covers most of this image originated by a collision with another asteroid, or by internal processes early in the asteroid's history. The image was recorded from a distance of about 1,700 miles (2,700 kilometers). The image resolution is about 260 meters per pixel. Reuters

NASA, in preparation for a worst-case scenario, has formalised a joint research programme with nuclear weapons experts, and steps for an initial design for a nuclear asteroid killer. Scientists are conducting research into the nuclear option against the estimated one million asteroids in the solar system that have the potential to strike Earth, the agency said.

NASA stated the primary concern of the research programme is to block an asteroid from the 10,000 known near-Earth objects from hitting the planet. The space agency considers the worst-case scenario of an asteroid might be discovered only a couple of weeks away from slamming into the Earth.

With these in mind, Brent Barbee, flight dynamics engineer at NASA’s Goddard Space Flight Centre, and Bong Wie, founding director of Asteroid Deflection Research Centre at lowa State University, conducted a three-year study on the feasibility of rapidly intercepting and nuking an incoming asteroid. The two experts proposed a ready-to-launch spacecraft called Hypervelocity Asteroid Intercept Vehicle, or HAIV, that they believe may deflect an asteroid through penetrating on its surface.

Barbee and Wie designed the two-piece spacecraft considering the scenario of having a few days to deflect an approaching asteroid. The spacecraft has a kinetic interceptor at the top and a second craft that contains the nuclear explosive. The purpose of the interceptor is to create a crater in the asteroid where the explosive will detonate before hitting the bottom, the experts explained.

The HAIV, according to the experts, will be carried by an expendable rocket that will turn the spacecraft into a missile that can travel out to space within a three-week warning. Experts said the spacecraft could intercept and destroy an asteroid as large as 140 metres in diameter, and disperse the fragments away from Earth.

However, scientists warn the possible threat of “disruption” or blowing an asteroid with nuclear weapons. NASA stated the event could create a “shotgun effect,” which multiple asteroid fragments “could rain devastation across a vast area” on Earth.

The possible solution to the problem, according to experts, is “energy coupling.” The method of measuring how much energy is transferred to the target by the explosive and the effect of that energy as it travels through the asteroid.

Upon considering the measurement of proper energy to obliterate an asteroid, Megan Syal, a researcher working on planetary defense scenarios at the Lawrence Livermore National Laboratory in California, stated there are factors that scientists must check. The variables of “the composition, the porosity, the strength of the material, the way it sustains damage, the shape, its rotational state, and its internal structure” are all needed in dealing with the scenario, Syal said.

NASA, however, is using supercomputer simulations to study the process of deflecting and destroying asteroids. The simulations are also a joint project between NASA and the National Nuclear Security Administration, or NNSA, a semi-autonomous government agency that manages some of the Department of Energy’s National Labs, which have previously conducted studies on scenarios for stopping asteroids.

With all the prospected scenarios, according to Barbee, NASA will be providing the nuclear asteroid killer’s flight and mission design together with the trajectory parameters, and the data on asteroid physical properties. He added the nuclear labs will be running computer codes to assess the effects of both kinetic impacts and nuclear devices on the hypothetical asteroids.

The initial cost of the programme would be $500 million for the test-fly of the HAIV. The HAIV will be loaded with ballast as a stand-in for the nuclear device, and will target an actual asteroid, according to Barbee and Wie.

However, to date, NASA has not funded any activity regarding the programme, but in 2016, the agency plans to launch OSIRIS-REx, which will survey the asteroid Bennu, to gather a tiny sample of the asteroid. Bennu, which is chosen for the study, has the chance to collide with Earth sometime between 2175 and 2196 AD, according to NASA. The spacecraft's measurements will also help astronomers more precisely predict the orbits of other near-Earth objects.

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