Using nuclear devices to deflect or disrupt an asteroid. Sounds a bit crazy, no? Maybe a little too Hollywood? And yet, detonating nukes in space may be necessary someday for the sake of planetary defense. In order for this method to be effective, scientists need to work out all the particulars in advance. That means knowing how much force will be necessary depending on the mass and trajectory of the asteroid.
Recently, a research collaboration between Lawrence Livermore National Laboratory (LLNL) and the Air Force Institute of Technology (AFIT) investigated how the energy output of a nuclear detonation could affect the path of an asteroid. This consisted of modeling different nuclear reactions (fission or fusion) to determine the neutron energy generated, which could potentially pave the way for a new type of asteroid redirect mission (ARM).
Next week, asteroid researchers and spacecraft engineers from all around the world will gather in Rome to discuss the latest in asteroid defense. The three-day International AIDA Workshop, which will run from Sept. 11th to 13th, will focus on the development of the joint NASA-ESA Asteroid Impact Deflection Assessment (AIDA) mission.
The purpose of this two-spacecraft system is to deflect the orbit of one of the bodies that make up the binary asteroid Didymos, which orbits between Earth and Mars. While one spacecraft will collide with a binary Near-Earth Asteroid (NEA), the other will observe the impact and survey the crash site in order to gather as much data as possible about this method of asteroid defense.
Finding examples of intelligent life other than our own in the Universe is hard work. Between spending decades listening to space for signs of radio traffic – which is what the good people at the SETI Institute have been doing – and waiting for the day when it is possible to send spacecraft to neighboring star systems, there simply haven’t been a lot of options for finding extra-terrestrials.
But in recent years, efforts have begun to simplify the search for intelligent life. Thanks to the efforts of groups like the Breakthrough Foundation, it may be possible in the coming years to send “nanoscraft” on interstellar voyages using laser-driven propulsion. But just as significant is the fact that developments like these may also make it easier for us to detect extra-terrestrials that are trying to find us.
Not long ago, Breakthrough Initiatives made headlines when they announced that luminaries like Stephen Hawking and Mark Zuckerberg were backing their plan to send a tiny spacecraft to Alpha Centauri. Known as Breakthrough Starshot, this plan involved a refrigerator-sized magnet being towed by a laser sail, which would be pushed by a ground-based laser array to speeds fast enough to reach Alpha Centauri in about 20 years.
In addition to offering a possible interstellar space mission that could reach another star in our lifetime, projects like this have the added benefit of letting us broadcast our presence to the rest of the Universe. Such is the argument put forward by Philip Lubin, a professor at the University of California, Santa Barbara, and the brains behind Starshot.
In a paper titled “The Search for Directed Intelligence” – which appeared recently in arXiv and will be published soon in REACH – Reviews in Human Space Exploration – Lubin explains how systems that are becoming technologically feasible on Earth could allow us to search for similar technology being used elsewhere. In this case, by alien civilizations. As Lubin shared with Universe Today via email:
“In our SETI paper we examine the implications of a civilization having directed energy systems like we are proposing for both our NASA and Starshot programs. In this sense the NASA (DE-STAR) and Starshot arrays represent what other civilizations may possess. In another way, the receive mode (Phased Array Telescope) may be useful to search and study nearby exoplanets.”
Using these as a template, Lubin believes that other species in the Universe could be using this same kind of directed energy (DE) systems for the same purposes – i.e. propulsion, planetary defense, scanning, power beaming, and communications. And by using a rather modest search strategy, he and colleagues propose observing nearby star and planetary systems to see if there are any signs of civilizations that possess this technology.
This could take the form of “spill-over”, where surveys are able to detect errant flashes of energy. Or they could be from an actual beacon, assuming the extra-terrestrials us DE to communicate. As is stated in the paper authored by Lubin and his colleagues:
“There are a number of reasons a civilization would use directed energy systems of the type discussed here. If other civilizations have an environment like we do they might use DE system for applications such as propulsion, planetary defense against “debris” such as asteroids and comets, illumination or scanning systems to survey their local environment, power beaming across large distances among many others. Surveys that are sensitive to these “utilitarian” applications are a natural byproduct of the “spill over” of these uses, though a systematic beacon would be much easier to detect.”
According to Lubin, this represents a major departure from what projects like SETI have been doing during the last few decades. These efforts, which can be classified as “passive” were understandable in the past, owing to our limited means and the challenges in sending out messages ourselves. For one, the distances involved in interstellar communication are incredibly vast.
Even using DE, which moves at the speed of light, it would still take a message over 4 years to reach the nearest star, 1000 years to reach the Kepler planets, and 2 million years to the nearest galaxy (Andromeda). So aside from the nearest stars, these time scales are far beyond a human lifetime; and by the time the message arrived, far better means of communication would have evolved.
Second, there is also the issue of the targets being in motion over the vast timescales involved. All stars have a transverse velocity relative to our line of sight, which means that any star system or planet targeted with a burst of laser communication would have moved by the time the beam arrived. So by adopting a pro-active approach, which involves looking for specific kinds of behavior, we could bolster our efforts to find intelligent life on distant exoplanets.
But of course, there are still many challenges that need to be overcome, not the least of which are technical. But more than that, there is also the fact that what we are looking for may not exist. As Lubin and his colleagues state in one section of the paper: “What is an assumption, of course, is that electromagnetic communications has any relevance on times scales that are millions of years and in particular that electromagnetic communications (which includes beacons) should have anything to do with wavelengths near human vision.”
In other words, assuming that aliens are using technology similar to our own is potentially anthropocentric. However, when it comes to space exploration and finding other intelligent species, we have to work with what we have and what we know. And as it stands, humanity is the only example of a space-faring civilization known to us. As such, we can hardly be faulted for projecting ourselves out there.
Here’s hoping ET is out there, and relies on energy beaming to get things done. And, fingers crossed, here’s hoping they aren’t too shy about being noticed!
Over the past month, about a half dozen rather large asteroids have careened nearby our home planet and in one case caused significant injury and property damage with no forewarning – showcasing the hidden lurking dangers from lackluster attitudes towards Asteroid Detection & Planetary Defense.
Now in a prescient coincidence of timing, NASA is funding an experimental asteroid radar detection array called ‘KaBOOM’ that may one day help thwart Earth’s untimely Ka-boom – and which I inspected first-hand this past week at the Kennedy Space Center (KSC),following the SpaceXFalcon 9 blastoff for the ISS.
“KaBOOM takes evolutionary steps towards a revolutionary capability,” said Dr. Barry Geldzahler, KaBOOM Chief Scientist of NASA Headquarters, in an exclusive interview with Universe Today.
If successful, KaBOOM will serve as a prelude to a US National Radar Facility and help contribute to an eventual Near Earth Object (NEO) Planetary Defense System to avert Earth’s demise.
“It will enable us to reach the goal of tracking asteroids farther out than we can today.”
First some background – This weekend a space rock the size of a city block whizzed past Earth at a distance of just 2.5 times the distance to our Moon. The asteroid – dubbed 2013 ET – is noteworthy because it went completely undetected until a few days beforehand on March 3 and measures about 460 feet (140 meters) in diameter.
2013 ET follows close on the heels of the Feb. 15 Russian meteor that exploded violently with no prior warning and injured over 1200 people on the same day as Asteroid 2012 DA 14 zoomed past Earth barely 17,000 miles above the surface – scarcely a whisker astronomically speaking.
Had any of these chunky asteroids actually impacted cities or other populated areas, the death toll and devastation would have been absolutely catastrophic – potentially hundreds of billions of dollars !
Taken together, this rash of uncomfortably close asteroid flybys is a wake-up call for a significantly improved asteroid detection and early warning system. KaBOOM takes a key step along the path to those asteroid warning goals.
‘KaBOOM’ – the acronym stands for ‘Ka-Band Objects Observation and Monitoring Project’ – is a new test bed demonstration radar array aimed at developing the techniques required for tracking and characterizing Near Earth Objects (NEO’s) at much further distances and far higher resolution than currently available.
“The purpose of KaBOOM is to be a ‘proof of concept’ using coherent uplink arraying of three widely spaced antennas at a high frequency; Ka band- 30 GHz,” KaBOOM Chief Scientist Geldzahler told me.
Currently the KaBOOM array consists of a trio of 12 meter wide radar antennas spaced 60 meters apart – whose installation was just completed in late February at a remote site at KSC near an alligator infested swamp.
I visited the array just days after the reflectors were assembled and erected, with Michael Miller, KaBOOM project manager of the Kennedy Space Center. “Ka Band offers greater resolution with shorter wavelengths to image smaller space objects such as NEO’s and space debris.”
“The more you learn about the NEO’s the more you can react.”
“This is a small test bed demonstration to prove out the concept, first in X-band and then in Ka band,” Miller explained. “The experiment will run about two to three years.”
Miller showed how the dish antennae’s are movable and can be easily slewed to different directions as desired.
“The KaBOOM concept is similar to that of normal phased arrays, but in this case, instead of the antenna elements being separated by ~ 1 wavelength [1 cm], they are separated by ~ 6000 wavelengths. In addition, we want to correct for the atmospheric twinkling in real time,” Geldzahler told me.
Why are big antennae’s needed?
“The reason we are using large antennas is to send more powerful radar signals to track and characterize asteroids farther out than we can today. We want to determine their size, shape, spin and surface porosity; is it a loose agglomeration of pebbles? composed of solid iron? etc.”
Such physical characterization data would be absolutely invaluable in determining the forces required for implementing an asteroid deflection strategy in case the urgent need arises.
How does KaBOOM compare with and improve upon existing NEO radars in terms of distance and resolution?
“Currently at NASA¹s Goldstone 70 meter antenna in California, we can track an object that is about 0.1 AU away [1 astronomical unit is the average distance between the Earth and the sun, 93 million miles, so 0.1 AU is ~ 9 million miles]. We would like to track objects 0.5 AU or more away, perhaps 1 AU.”
“In addition, the resolution achievable with Goldstone is at best 400 cm in the direction along the line of sight to the object. At Ka band, we should be able to reduce that to 5 cm – that’s 80 times better !”
“In the end, we want a high power, high resolution radar system,” Geldzahler explained.
Another significant advantage compared to Goldstone, is that the Ka radar array would be dedicated 24/7 to tracking and characterizing NEO’s and orbital debris, explained Miller.
Goldstone is only available about 2 to 3% of the time since it’s heavily involved in numerous other applications including deep space planetary missions like Curiosity, Cassini, Deep Impact, Voyager, etc.
‘Time is precious’ at Goldstone – which communicates with some 100 spacecraft per day, says Miller.
“If/when the proof of concept is successful, then we can envision an array of many more elements that will enable us to reach the goal of tracking asteroids farther out than we can today,” Geldzahler elaborated.
A high power, high resolution radar system can determine the NEO orbits about 100,000 times more precisely than can be done optically.
So – what are the implications for Planetary Defense ?
“If we can track asteroids that are up to 0.5 AU rather than 0.1 AU distant, we can track many more than we can track today.”
“This will give us a better chance of finding potentially hazardous asteroids.”
“If we were to find that a NEO might hit the Earth, NASA and others are exploring ways of mitigating the potential danger,” Geldzahler told me.
Kaboom’s ‘First light’ is on schedule for late March 2013.
Planetary Defense is a concept very few people heard of or took seriously – that is until last week’s humongous and totally unexpected meteor explosion over Russia sent millions of frightened residents ducking for cover, followed just hours later by Earth’s uncomfortably close shave with the 45 meter (150 ft) wide asteroid named 2012 DA14.
This ‘Cosmic Coincidence’ of potentially catastrophic space rocks zooming around Earth is a wakeup call that underscores the need to learn much more about the ever present threat from the vast array of unknown celestial debris in close proximity to Earth and get serious about Planetary Defense from asteroid impacts.
The European Space Agency’s (ESA) proposed Asteroid Impact and Deflection Assessment mission, or AIDA, could significantly bolster both our basic knowledge about asteroids in our neighborhood and perhaps even begin testing Planetary Defense concepts and deflection strategies.
After two years of work, research teams from the US and Europe have selected the mission’s target – a so called ‘binary asteroid’ named Didymos – that AIDA will intercept and smash into at about the time of its closest approach to Earth in 2022 when it is just 11 million kilometers away.
“AIDA is not just an asteroid mission, it is also meant as a research platform open to all different mission users,” says Andres Galvez, ESA studies manager.
Asteroid Didymos could provide a great platform for a wide variety of research endeavors because it’s actually a complex two body system with a moon – and they orbit each other. The larger body is roughly 800 meters across, while the smaller one is about 150 meters wide.
So the smaller body is some 15 times bigger than the Russian meteor and 3 times the size of Asteroid 2012 DA14 which flew just 27,700 km (17,200 mi) above Earth’s surface on Feb. 15, 2013.
The low cost AIDA mission would be comprised of two spacecraft – a mother ship and a collider. Two ships for two targets.
The US collider is named the Double Asteroid Redirection Test, or DART and would smash into the smaller body at about 6.25 km per second. The impact should change the pace at which the objects spin around each other.
ESA’s mothership is named Asteroid Impact Monitor, or AIM, and would carry out a detailed science survey of Didymos both before and after the violent collision.
“The project has value in many areas,” says Andy Cheng, AIDA lead at Johns Hopkins’ Applied Physics Laboratory, “from applied science and exploration to asteroid resource utilisation.” Cheng was a key member of NASA’s NEAR mission that first orbited and later landed on the near Earth Asteroid named Eros back in 2001.
Recall that back in 2005, NASA’s Deep Impact mission successfully lobbed a projectile into Comet Tempel 1 that unleashed a fiery explosion and spewing out vast quantities of material from the comet’s interior, including water and organics.
ESA has invited researchers to submit AIDA experiment proposals on a range of ideas including anything that deals with hypervelocity impacts, planetary science, planetary defense, human exploration or innovation in spacecraft operations. The deadline is 15 March.
“It is an exciting opportunity to do world-leading research of all kinds on a problem that is out of this world,” says Stephan Ulamec from the DLR German Aerospace Center. “And it helps us learn how to work together in international missions tackling the asteroid impact hazard.”
The Russian meteor exploded without warning in mid air with a force of nearly 500 kilotons of TNT, the equivalent of about 20–30 times the atomic bombs detonated at Hiroshima and Nagasaki.
Over 1200 people were injured in Russia’s Chelyabinsk region and some 4000 buildings were damaged at a cost exceeding tens of millions of dollars. A ground impact would have decimated cities like New York, Moscow or Beijing with millions likely killed.
ESA’s AIDA mission concept and NASA’s approved Osiris-REx asteroid sample return mission will begin the path to bolster our basic knowledge about asteroids and hopefully inform us on asteroid deflection and Planetary Defense strategies.
Apollo 9 astronaut Rusty Schweickart is among an international group of people championing the need for the human race to prepare for what will certainly happen one day: an asteroid threat to Earth. In an article on Universe Today published yesterday, Schweickart said the technology is available today to send a mission to an asteroid in an attempt to move it, or change its orbit so that an asteroid that threatens to hit Earth will pass by harmlessly. What would such a mission entail?
In a phone interview, Schweickart described two types of “deflection campaigns” for a threatening asteroid: a kinetic impact would roughly “push” the asteroid into a different orbit, and a gravity tractor would “tug slowly” on the asteroid to precisely “trim” the resultant change course by using nothing more than the gravitational attraction between the two bodies. Together these two methods comprise a deflection campaign.
“In a way, the kinetic impact was demonstrated by the Deep Impact mission back in 2005,” said Schweickart. “But that was a very big target and a small impactor that had relatively no effect on the comet. So, we haven’t really demonstrated the capability to have the guidance necessary to deflect a moderately sized asteroid.”
Most important, the gravity tractor spacecraft would arrive prior to the kinetic impactor, precisely determine the asteroid’s orbit and observe the kinetic impact to determine its effectiveness. Following the kinetic impact it would then determine whether or not any adjustment trim were required.
“You want to know what happens when you do a kinetic impact, so you want an ‘observer’ spacecraft up there as well,” Schweickart explained. “You don’t do a kinetic impact without an observation, because the impactor destroys itself in the process and without the observer you wouldn’t know what happened except by tracking the object over time, which is not the best way to find out whether you got the job done.”
So, 10-15 years ahead of an impact threat — or 50 years if you have that much time — an observer spacecraft is sent up. “This, in fact, would also be a gravity tractor,” Schweickart said. “It doesn’t have to be real big, but bigger gets the job done a little faster. The feature you are interested in the outset is not the gravity tractor but the transponder that flies in formation with the asteroid and you track the NEO, and back on Earth we can know exactly where it is.”
Schweickart said even from ground tracking, we couldn’t get as precise an orbit determination of an NEO as we could by sending a spacecraft to the object. Additionally, generally speaking, we may not know when we send an observer spacecraft what action will be required; whether an impact will be required or if we could rely on the gravity tractor. “You may launch at the latest possible time, but at that time the probability of impact may be 1 in 5 or 1 or 2,” Schweickart said. “So the first thing you are going to do with the observer spacecraft is make a precise orbit determination and now you’re going to know if it really will impact Earth and even perhaps where it will impact.”
After the precise orbit is known, the required action would be determined. “So now, if needed you launch a kinetic impactor and now you know what job has to be done,” Schweickart said. “As the impactor is getting ready to impact the asteroid, the observer spacecraft pulls back and images what is going on so you can confirm the impact was solid, –not a glancing blow — and then after impact is done, the observer spacecraft goes back in and makes another precision orbit determination so that you can confirm that you changed its velocity so that it no longer will hit the Earth.”
The second issue is, even if the NEO’s orbit has been changed so that it won’t hit Earth this time around, there’s the possibility that during its near miss it might go through what is called a “keyhole,” whereby Earth’s gravity would affect it just enough that it would make an impact during a subsequent encounter with Earth. This is a concern with the asteroid Apophis, which is projected to miss Earth in 2029, but depending on several factors, could pass through a keyhole causing it to return to hit Earth in 2036.
“So if it does go through that keyhole,” said Schweickart, “now you can use the gravity tractor capability of the spacecraft to make a small adjustment so that it goes between keyholes on that close approach. And now you have a complete verified deflection campaign.”
Schweickart said a Delta-sized rocket would be able to get a spacecraft to meet up with an asteroid. “A Delta rocket would work,” he said, “but if there is a more challenging orbit we might have to use something bigger, or we may have to use a gravity assist and do mission planning for type of thing which hasn’t been done yet. So we can get there, we can do it – but ultimately we will probably need a heavy lift vehicle.”
As for the spacecraft, we can use a design similar to vehicles that have already been sent into space.
“A gravity tractor could be like Deep Space 1 that launched in 1998,” Schweickart said. “ You can make any spacecraft into a gravity tractor fairly easily.”
But it hasn’t been demonstrated and Schweickart says we need to do so.
“We need to demonstrate it because we – NASA, the technical community, the international community — need to learn what you find out when you do something for the first time,” he said. “Playing a concerto in front of an audience is quite different from playing it alone in your house.”