Could We Blow Up An Asteroid With A Nuclear Bomb?

You've seen it plenty of times on the big screen: Scientists spot an enormous asteroid hurtling toward Earth and the only hope for mankind is to send a team to plant a nuclear bomb inside the looming monster. Despite several suspenseful setbacks, the intrepid team is ultimately successful, and the asteroid explodes into millions of pieces. Earth is saved yet again from certain doom. Yahoo. Movies like "Deep Impact" and "Armageddon" make it seem so easy. Surely nuclear weapons that can obliterate entire cities contain enough destructive power to blow a giant space rock to bits, right?

The answer is yes and no. To start with, asteroids come in all shapes and sizes. Ceres, the largest known asteroid, stretches 580 miles (933 kilometers) in diameter, while one of the smallest on record, 1991 BA, measures 20 feet (6 meters) across. An asteroid larger than 6.2 miles (10 kilometers) in diameter is considered "extinction class," or powerful enough to destroy life on Earth if it collides with our hapless planet [source: NASA].

Technically, a nuclear bomb could obliterate a smaller asteroid, but it's not these smaller entities that pose a threat to Earth's safety. The asteroids that would be really worrisome -- those larger than 1,312 feet (400 meters) -- wouldn't be easily wiped out by such a bomb. Sure, great hunks of one might break off, but not enough to neutralize the danger. A 2007 NASA report indicated that planting a nuclear bomb on or under the surface of an asteroid would most likely cause it to fracture into several pieces -- and large pieces of an even larger asteroid can still be pretty dangerous if they're hurtling toward the Earth [source: NASA].

So while yes, a nuclear bomb could be used to blow up a small asteroid, it's unlikely that world leaders would waste expensive resources on that endeavor. As for large, Earth-threatening asteroids, a nuke likely wouldn't succeed at blowing it up completely.

 There's Ida. She's roughly 32 miles (52 kilometers) across. An asteroid like her would spell big trouble for our planet if she ever got the notion to visit

  

NASA's Asteroid Defense Plan

So a nuclear bomb would be essentially useless at disintegrating an asteroid several miles wide, but scientists at NASA think that a nuclear weapon could be used in a different way to defend the planet.

In 2005, U.S. Congress asked NASA to develop plans for preventing an asteroid-Earth collision. In 2007, the space agency presented its ideas at the Planetary Defense Conference in Washington, D.C. (which sounds like something out of a sci-fi flick). In its report, NASA outlined several options, a few of which involved using nuclear explosives to deflect the asteroid away from Earth. The force from the explosions would (hopefully) provide enough momentum to nudge the asteroid in a different direction, preventing disaster.

In the explosions category, NASA discovered that nuclear explosives are way more effective for asteroid deflection than non-nuclear explosives, due to the sheer amount of energy they produce. NASA tested four nuclear scenarios: a surface explosion, a delayed surface explosion, a subsurface explosion and a standoff explosion (where the bomb doesn't come into contact with the asteroid). The surface and subsurface explosions are the most effective, but there's a good chance of splitting the asteroid. In the end, the space agency determined that a series of standoff nuclear explosions would be the most effective way to deflect an asteroid headed for Earth.

The best option in the non-nuclear category is a kinetic impact (a nice way of saying they would ram objects into the asteroid), but doing so would require detailed knowledge of what the surface of the asteroid is like. Some other non-nuclear options that NASA considered include using a laser or a giant mirror to focus energy on a spot on the asteroid and "boil off" parts of it, or using a spacecraft to tug the asteroid in a different direction.

So, will we ever know in our lifetime if it's possible to deflect an asteroid? Maybe. In December 2009, the director of the Russian Federal Space Agency, Anatoly Perminov, announced that Russia was considering making plans to deflect the 270-meter (885-foot) asteroid Apophis from its possible collision course with Earth. While NASA claims that the chances of Apophis colliding with Earth are only about 1 in 250,000, it does demonstrate that shooting objects at asteroids to knock them out of the way is a definite possibility [source: Discovery News].

 by "environment clean generations"

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Posted in: Apophis,asteroid,Could We Blow Up An Asteroid With A Nuclear Bomb?,nuclear blast,space

Human mission to an asteroid: Why should NASA go?

Imagine, if you can, the first time human eyes see Earth as a distant, pale blue dot. We’ve dreamed of deep space missions for centuries, and during the Apollo era, space enthusiasts assumed we’d surely be out there by now. Nevertheless, given the current state of faltering economies and potential budget cuts for NASA and other space agencies, sending humans beyond low Earth orbit might seem as impossible and unreachable as ever, if not more.

But NASA has been given a presidential directive to land astronauts on an asteroid by 2025, a mission that some say represents the most ambitious and audacious plan yet for the space agency.

“The human mission to an asteroid is an extremely important national goal,” Apollo astronaut Rusty Schweickart told Universe Today. “It will focus both NASA’s and the nation’s attention on we humans extending our capability beyond Earth/Moon space and into deep space. This is an essential capability in order to ultimately get to Mars, and a relatively short mission to a near-Earth asteroid is a logical first step in establishing a deep space human capability.”

And, Schweickart added, the excitement factor of such a mission would be off the charts. “Humans going into orbit around the Sun is pretty exciting!” said Schweickart, who piloted the lunar module during the Apollo 9 mission in 1969. “The Earth will be, for the first time to human eyes, a small blue dot.”

But not everyone agrees that an asteroid is the best destination for humans. Several of Schweickart’s Apollo compatriots, including Neil Armstrong, Jim Lovell and Gene Cernan, favor returning to the Moon and are concerned that President Obama’s directive is a “grounding of JFK’s space legacy.”

Compounding the issue is that NASA has not yet decided on a launch system capable of reaching deep space, much less started to build such a rocket.

Can NASA really go to an asteroid?

NASA Administrator Charles Bolden has called a human mission to an asteroid “the hardest thing we can do.”

Excited by the challenge, NASA chief technology officer Bobby Braun said, “This is a risky, challenging mission. It’s the kind of mission that engineers will eat up.”

A human mission to an asteroid is a feat of technical prowess that might equal or exceed what it took for the US to reach the Moon in the 1960’s. Remember scientists who thought the moon lander might disappear into a “fluffy” lunar surface? 

That reflects our current understanding of asteroids: we don’t know how different asteroids are put together (rubble pile or solid surface?) and we certainly aren’t sure how to orbit and land on one.

“One of the things we need to work on is figuring out what you actually do when you get to an asteroid,” said Josh Hopkins from Lockheed Martin, who is the Principal Investigator for Advanced Human Exploration Missions.

Hopkins leads a team of engineers who develop plans and concepts for a variety of future human exploration missions, including visits to asteroids. He and his team proposed the so-called “Plymouth Rock” mission to an asteroid (which we’ll discuss more in a subsequent article), and have been working on the Orion Multi-purpose Crew Vehicle (MPCV), which would be a key component of a human mission to an asteroid.

“How do you fly in formation with an asteroid that has a very weak gravitational field, so that other perturbations such as slight pressure from the Sun would affect your orbit,” Hopkins mused, in an interview with Universe Today. “How do you interact with an asteroid, especially if you don’t know exactly what its surface texture and composition is? How do you design anchors or hand-holds or tools that can dig into the surface?”

Hopkins said he and his team have been working on developing some technologies that are fairly “agnostic” about the asteroid – things that will work on a wide variety of asteroids, rather than being specific to an iron type- or carbonaceous-type asteroid.

A weak gravity field means astronauts probably couldn’t walk on some asteroids – they might just float away, so ideas include installing handholds or using tethers, bungees, nets or jetpacks. In order for a spaceship to stay in orbit, astronauts might have to “harpoon” the asteroid and tether it to the ship.

Hopkins said many of those types of technologies are being developed for and will be demonstrated on NASA’s OSIRIS-REx mission, the robotic sample return mission that NASA recently just selected for launch in 2016. “That mission is very complimentary to a future human mission to an asteroid,” Hopkins said.

Benefits

What benefits would a human asteroid mission provide?

“It would add to our body of knowledge about these interesting, and occasionally dangerous bodies,” said Schweickart, “and benefit our interest in protecting the Earth from asteroid impacts. So the human mission to a NEO is a very high priority in my personal list.”

Space shuttle astronaut Tom Jones says he thinks a mission to near Earth objects is a vital part of a planned human expansion into deep space. It would be an experiential stepping stone to Mars, and much more.

“Planning 6-month round trips to these ancient bodies will teach us a great deal about the early history of the solar system, how we can extract the water known to be present on certain asteroids, techniques for deflecting a future impact from an asteroid, and applying this deep space experience toward human Mars exploration,” Jones told Universe Today.

“Because an asteroid mission will not require a large, expensive lander, the cost might be comparable to a shorter, lunar mission, and NEO expeditions will certainly show we have set our sights beyond the Moon,” he said.

But Jones – and others – are concerned the Obama administration is not serious about such a mission and that the president’s rare mentions of a 2025 mission to a nearby asteroid has not led to firm NASA program plans, realistic milestones or funding.

“I think 2025 is so far and so nebulous that this administration isn’t taking any responsibility for making it happen,” Jones said. “They are just going to let that slide off the table until somebody else takes over.”

Jones said he wouldn’t be surprised if nothing concrete happens with a NASA deep space mission until there is an administration change.

“The right course is to be more aggressive and say we want people out of Earth orbit in an Orion vehicle in 2020, so send them around the Moon to test out the ship, get them to the LaGrange points by 2020 and then you can start doing asteroid missions over the next few years,” Jones said. “Waiting for 2025 is just a political infinity in terms of making things happen.”

Jones said politics aside, it is certainly feasible to do all this by 2020. “That is nine years from now. My gosh, we are talking about getting a vehicle getting out of Earth orbit. If we can’t do that in nine years, we probably don’t have any hope of doing that in longer terms.”

Can NASA do such a mission? Will it happen? If so, how? Which asteroid should humans visit?

Over the next few days, we’ll take a closer look at the concepts and hurdles for a human mission to an asteroid and attempt to answer some of these questions.

by "environment clean generations"

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Posted in: asteroid,earth,mars,nasa,Orion Multi-purpose Crew Vehicle,space

Asteroid In the Earth's Orbit

       Earth's first known Trojan asteroid follows an oddly tilted path (green) in relation to Earth's orbit (blue).

A tiny space rock that's partially tethered to Earth by a gravitational leash is our planet's first known Trojan asteroid, astronomers say.

            Trojans are objects that exist in gravitationally stable regions in front of or behind another body, so that the two share the same orbit but never collide; some asteroids

Trojan asteroids have been found around Jupiter, Neptune, and Mars, and Saturn is orbited by a few groups of Trojan moons. (See "'Dead Zone' Asteroid Found Following Neptune.")

            Earth's newfound Trojan is about 1,000 feet (300 meters) wide and sits about 50 million miles (80 million kilometers) in front of Earth.

            "It is in orbit around the sun in the same path that our orbital path is, and it is controlled partly by our gravity, but the sun's gravity controls it more," said Martin Connors, an astronomer at Athabasca University in Canada and one of the co-discoverers of the asteroid.

              Connors likens the odd asteroid to an orange held at arm's length by a person riding a Ferris wheel. In this analogy, the orange is the Trojan, the person is Earth, and the Ferris wheel is our orbit around the sun.

"The orange would be going around the Ferris wheel, but maintaining it out at arm's length is up to you," Connors explained about asteroid.

              "This Trojan asteroid is like that: There's a main thing that's dragging it around, which is the sun's gravity, but the Earth does have some control over it as well. If the Earth's gravity wasn't there, it would go off on a different course, just like if you were to let go of the orange, it would fall to the ground."

More Earth Trojans Asteroids Yet to Be Spotted?

            Scientists had long predicted that Earth should have Trojans asteroids, but such asteroids hadn't been spotted until now because they tend to be relatively small and to lie in the general direction of the sun as seen from Earth, making them hard to spot in the star's glare.

             Fortunately, the newfound Trojan asteroid's orbit takes it far enough away from the sun for telescopes to spot.

Connors and his team spotted the rocky escort, dubbed 2010 TK7, using NASA's Wide-Field Infrared Survey Explorer, or WISE, space telescope. The team later confirmed the find with the Canada-France-Hawaii Telescope on Mauna Kea in Hawaii, for the asteroid

            It's unknown how or when Earth and the asteroid coupled in the first place, but computer models suggests the Trojan's orbit will be stable for at least another ten thousand years.

Despite being relatively close to Earth, 2010 TK7 is not a good candidate for future robotic or human exploration, the scientists added. (Related: "NASA Asteroid Mission Set for 2016.")

              That's because the asteroid follows an unusual tilted path in relation to Earth's, so it's either too far above or below the plane of our planet's orbit. In this configuration, getting to the Trojan asteorid would require large amounts of fuel.

              However, there may be more conveniently located Earth Trojans asteroids that have yet to be discovered, Connors said.

             "Among Jupiter's Trojan asteroids, some of them are nearly in the plane of Jupiter," he said.

             "If we can find similar things for Earth, then they would be pretty low-energy targets to get to, and that would be an interesting opportunity to have."

          

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