Mission to Mars Page 9

  NEOs have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter Earth’s solar system neighborhood. We should learn more about these extraterrestrial wanderers in both scientific and practical terms. I believe my USV essentials of exploration, science, development, commerce, and security fit well with NEOs.

  In recasting the U.S. space exploration program in April 2010, President Obama called upon NASA, early in the next decade, to carry out piloted flights to test and validate the systems needed for exploration beyond low Earth orbit. He expected, by 2025, new spacecraft intended for long journeys that would permit America to begin the first ever crewed missions beyond the moon into deep space—starting with sending astronauts to an asteroid for the first time in history. Those deep space assaults are prologue to placing humans in orbit around Mars, returning them safely to Earth, with a human landing on Mars to follow.

  In stepping up to Obama’s space plan, NASA has begun planning an asteroid mission as the first part of a “capability-driven” approach to explore multiple deep space destinations, acknowledging that the space agency’s ultimate destination for human exploration is Mars.

  Success requires viable asteroid targets. NASA has identified two accessible space rocks—asteroids 2009 HC and 2000 SG344, NEOs for space travelers to examine in the 2023–2025 time period. But getting there is technology demanding, supported by advanced in-space propulsion, a deep space exploration module that provides adequate habitation for crews, radiation protection, and autonomous operations. A dedicated crewed NEO mission will check out and validate new deep space systems. What is most important, in my point of view, is to ramp up our ability for NEO exploration crew members to perform at demanding destinations while, at the same time, advance our technological skills with each step forward.

  So let’s look at the exploration, science, development, commerce, and security pieces that are tied to NEOs.

  Number one is that near-Earth objects have thumped our world over the ages, and assuredly will in the future. NEOs can shake up but also shape our life-sustaining ecosystem. To assure the survival and guarantee the movement of humanity into space, I feel it is vital we come to terms with NEOs that may have Earth within their crosshairs. Doing so harnesses the technological muscle to not only encounter but also counter these objects, and it also allows us to use space objects as resource and exploration stepping-stones to Mars, thereby helping to extend the human presence into space.

  Earth on the receiving end of a large asteroid

  (Illustration Credit 5.2)

  Over the eons, it has been a celestial slugfest. Comets and asteroids have struck Earth since its formation 4.5 billion years ago, bringing seeds of life to Earth early in its history and shattering life by altering the globe’s ecosystem, such as hypothesized as the cause for the extinction of dinosaurs.

  First of all, I’m not saying you should lose sleep worrying about a giant space rock hitting our world. However, experts that I’ve listened to advise that, while the chances of a destructive impact here on Earth in the near future are small, they are not zero—and the consequence of a hefty NEO colliding with the planet would be extreme.

  Itokawa, a large asteroid surveyed by Japan’s Hayabusa probe, contrasted with the International Space Station

  (Illustration Credit 5.3)

  For the moment, put aside that mental image of movie star Bruce Willis and his team wrestling with a massive space rock in the hit film Armageddon. It turns out that smaller “airbursters” are the more disconcerting sky-slamming flotsam from space. They can cause localized destruction and may infringe upon our air space with surprisingly little warning time.

  For example, the 1908 Tunguska event is a saga in which a rocky impactor detonated over remote Siberian real estate, knocking down about 500,000 acres of forest. Supercomputer simulation work led by Sandia National Laboratories principal investigator Mark Boslough suggests that the incoming object was roughly 130 feet in diameter. The object broke up in a cascading way, leading to a rapidly expanding fireball and subsequent blast wave that hit the ground, stirring up a wind strong enough to actually blow over trees. Because smaller asteroids approach Earth statistically more often than larger ones, efforts to detect smaller NEOs would appear to be in order. It is estimated that these smaller objects could impact Earth on average every 2 to 12 years.

  More recently, in October 2009, a fireball blast in daylight was observed and recorded over an island region of Indonesia. That atmospheric entry of a small asteroid, perhaps just 33 feet across, rocked their world with a projected energy release of about 50 kilotons, equal to some 110,000 pounds of TNT explosive. Eyewitnesses reported a bright fireball, accompanied by an explosion and a lasting dust cloud.

  You can easily visit an impact site of an iron asteroid by traveling to the Barringer meteorite crater, known popularly as Meteor Crater, near Winslow, Arizona. It was formed some 50,000 years ago in flat-lying sedimentary rocks of the southern Colorado Plateau. When that cosmic interloper grooved into Earth tens of thousands of years ago, more than 175 million metric tons of rock were hurled into the sky and redeposited on the crater rim and the surrounding terrain in a matter of a few seconds.

  There is an ongoing debate as to the downfall of dinosaurs at the end of the Cretaceous geologic period, 65 million years ago, and the growing consensus is that a mega-asteroid impact caused their mass extinction. That viewpoint stirred up a comment by science-fiction writer Larry Niven: “The dinosaurs became extinct because they didn’t have a space program. And if we become extinct because we don’t have a space program, it’ll serve us right!” That is insight, and I can’t say it much more directly than Niven has.

  An Arizona crater: remains of an asteroid impact

  (Illustration Credit 5.4)

  Siberian forest in ruins: aftermath of a 1908 asteroid

  (Illustration Credit 5.5)

  Getting to Know NEOs

  Take note that some 75 percent of Earth is covered by water. What are the consequences if a medium-size asteroid plowed into deep ocean waters?

  Research carried out by the late Elisabetta Pierazzo, a senior scientist at the Planetary Science Institute in Tucson, Arizona, served up some bad news. Her work indicated that an asteroid crashing into the deep ocean could have dramatic worldwide environmental effects, including depletion of Earth’s protective ozone layer for several years.

  There has long been interest in the effects of oceanic impacts of medium-size asteroids, but more focused on the danger of stirring up a regional tsunami. But Pierazzo’s approach used computer-modeling scenarios to look at the effects such a strike would have on the atmospheric ozone. The results suggest that midlatitude oceanic impacts of one-kilometer asteroids can produce major global perturbation of upper atmospheric chemistry, including multiyear global ozone lessening.

  Pierazzo found that rapidly ejected seawater from an NEO strike includes water vapor and compounds like chloride and bromide that hasten the destruction of the ozone, all of which would influence atmospheric chemistry. Indeed, the removal of a significant amount of ozone in the upper atmosphere for an extended period of time, she found, would have important biological repercussions at Earth’s surface—such as an increase in ultraviolet rays that reach terra firma.

  So be it by land, air, or sea, getting to know NEOs, I believe, is high on the space program’s to-do list. The overall message in terms of planetary defense is that there’s need to find them before they find us.

  By making use of ground- and space-based technology, humankind does have the ability to anticipate a large-scale impact. Preventing such an occurrence is another matter. Still, to protect life from such a vicious event is an environmental challenge, one that calls upon integrating technology, space policy, and international involvement to launch a global response.

  Several fellow space travelers have maintained a long-standing interest in NEOs.

  A leader in taking on the NEO challenge is
Rusty Schweickart, Apollo 9 astronaut and chairman emeritus of the B612 Foundation. That group announced last year their aim to fund-raise, build, launch, and operate the world’s first privately funded deep space telescope mission. Called Sentinel, this project would identify the current and future locations and trajectories of Earth-crossing asteroids. The mission calls for a space telescope—to be built by Ball Aerospace in Boulder, Colorado—to be placed in orbit around the sun, ranging up to 170 million miles from Earth, for a mission of discovery and mapping.

  Sentinel appears to be technically sound and on track for a 2017 launch to protect Earth by providing early warning of threatening asteroids. B612 and Ball Aerospace have developed a very viable detection method for finding and tracking near-Earth asteroids. In addition, NASA has forged a Space Act Agreement with the B612 organization to pursue innovative in-space survey skills for detection of new NEO targets.

  “For the first time in history, B612’s Sentinel mission will create a comprehensive and dynamic map of the inner solar system in which we live—providing vital information about who we are, who are our neighbors, and where we are going,” reports Schweickart. “We will know which asteroids will pass close to Earth and when, and which if any of these asteroids actually threaten to collide with Earth. The nice thing about asteroids is that once you’ve found them and once you have a good solid orbit on them you can predict a hundred years ahead of time whether there is a likelihood of an impact with Earth.”

  Astronaut Ed Lu, veteran of space shuttle, Soyuz, and space station missions, is the B612 Foundation chairman and CEO. The extraordinary B612 Sentinel mission extends the emerging commercial spaceflight industry into deep space—a first that will pave the way for many other ventures. “Mapping the presence of thousands of near-Earth objects will create a new scientific database and greatly enhance our stewardship of the planet,” Lu believes.

  Robotic spacecraft surveys a large asteroid.

  (Illustration Credit 5.6)

  Private Sentinel telescope eyes asteroid population.

  (Illustration Credit 5.7)

  Along with the need to come to terms with the dangers of asteroids, there are several other important outcomes of their study. The United States, Europe, and Japan have successfully hurled spacecraft to asteroids, with more robotic probes to key NEOs on the books.

  Russian engineers have been promoting the idea of an automated craft emplacing a location transmitter on asteroid 99942 Apophis, to maintain a more accurate track of this potentially hazardous 690-to-1,080-foot-diameter object. By doing that, we would obtain a very accurate orbit of this NEO, along with an early warning of whether it’s on a menacing course with Earth in the years to come.

  We already know that the Apophis trajectory places it on an extremely close flyby of Earth in 2029—it is so close, in fact, that it will zip below our geosynchronous satellites. Earth’s gravitational tug on Apophis, some worry, may alter its course in such a way as to run into our planet in 2036. But the chance of that happening, experts say, is very, very slim.

  My review of Apophis has been enlightening in several ways, specifically in picturing a rotating Earth orbit around the sun where the sun-Earth line is fixed. What an NEO does, if its semi-major axis is inside Earth: It does a series of loops around the inside of that circle, then comes back within the vicinity of Earth. Those set of loops are essentially the number of years before it comes back close to Earth.

  By Apophis whisking past Earth in 2029, that gravity-assist pass is going to change this NEO so its semi-major axis is outside Earth. Until 2036, it will do a series of loops that are outside the circle and traveling in the opposite direction. In other words, Earth’s rotating coordinate frame is moving ahead of Apophis.

  Simply, Apophis is going to be doing loop-the-loops, getting ahead of Earth, and then it’s going to buzz by Earth and do loop-the-loops outside of Earth’s orbit. That’s what the gravity swingby of planet Earth is doing to this NEO, and I was really amazed when I found that out.

  It is a good lesson learned on what an asteroid and its orbit around the sun, or period, do in terms of its availability for a revisit by a robot or a human crew, which is not a constant. It is analogous to understanding some of the inertial cycler orbits that are necessary to sustain a long-term space program.

  Getting Our Space Legs

  Visitation of NEOs by robotic craft certainly paves the way for human exploration of specific asteroids in the future.

  In understanding and coping with the hazard of devastating impacts by NEOs on Earth, we can learn about the physical nature of NEOs. Doing that, in turn, can incrementally enhance our odds of effectively dealing with an NEO, should one of these objects be discovered that could gravely affect us. Furthermore, melding human and robotic abilities at an NEO serves as a test bed to perfect our skills for working at ever greater distances.

  In my estimation, human visits to NEOs can go partway toward appreciating the challenges of travel to Mars, without invoking the most severe difficulties. Mars must remain a decisive destination, but NEOs offer a special, practical, and inspiring challenge that gives us the “space legs” to propel deeper toward the red planet.

  My research colleague Anthony Genova, at the NASA Ames Research Center, is of like mind. Human exploration of NEOs offers valuable and exciting opportunities as stepping-stones to eventual Mars exploration and colonization. He, too, supports a stepping-stone approach—similar to that seen in the Apollo program—as NEO missions not only reduce the overall risk and complexity of a human space exploration program, but also decrease the wait time needed for the next “new” mission, allowing the public to lend its crucial support to the program much earlier than would otherwise be anticipated without intermediate exploration achievements.

  NASA scientists simulate an asteroid rendezvous.

  (Illustration Credit 5.8)

  Although asteroids routinely zoom by close to Earth, even within the moon’s orbit, larger and more interesting asteroids may be tens of millions of miles away. That’s a lengthy haul for people without a resupply of water, food, or air—a mission longer than has ever been attempted in space and far different from the cargo craft that routinely visit the International Space Station.

  NASA’s current goal of having astronauts on an asteroid-bound mission by 2025 is a core idea promoted by U.S. President Obama. That call represented a major shift from the space agency’s earlier plan, which was aimed at replanting U.S. astronauts on the moon.

  Since Obama’s 2010 space speech, the interest in transporting astronauts to an asteroid has picked up speed, not only at NASA but also within the aerospace community. The rationale is that such a deep space expedition not only tests out hardware but also builds confidence in humans performing long-duration journeys to other destinations, like the moons of Mars, or onward to the red planet itself. At the same time, a piloted journey to an NEO would provide the savvy to deal with a future space rock found to be on a collision course with Earth.

  I term these asteroid explorers “NEOphytes,” and they have projected that a human trek to one of those mini-worlds may involve two or three astronauts on a 90-to-120-day spaceflight. The round-trip travel includes a week or two-week stay at the appointed asteroid.

  One blueprinted NEO mission, an early human asteroid mission that uses NASA’s Orion spacecraft, has been dubbed Plymouth Rock. That plan has been scripted by Orion’s builder, Lockheed Martin, and detailed by advanced planner Josh Hopkins.

  They portray a six-month mission to an asteroid taking astronauts several million miles from Earth—many times farther away than the moon, but closer than Mars. This requires a very capable spacecraft with propulsion, living space, and life-support supplies, as well as safety features to protect the crew in the event of a problem, since they can’t return to Earth quickly.

  Frankly, stuffing a crew into the tight quarters of an Orion capsule—even two of them docked together—is not the way to go. Again, I advocate building off of
our International Space Station. We need to use our station experience to prototype both a specialized crewed interplanetary habitat and a specialized crewed interplanetary taxi. That’s the way to get down to business in projecting ourselves outward into deep space.

  What’s also urgently required is a much better survey of NEOs, using ground- and space-based assets, to greatly expand the catalog of accessible and meaningful asteroid targets for human exploration. Identification of a sufficient number of accessible and desirable asteroids is critical for future human missions. While the whereabouts of several thousand near-Earth objects are known, the number and physical makeup of space rocks that are reachable by piloted flight are highly uncertain. There’s a paucity of targets at present to assure maximum mission flexibility. Besides, when it comes to a long-haul, piloted expedition, asteroid size does matter.

  Astronauts will grasp tethers to stay close to asteroids.

  (Illustration Credit 5.9)

  Here’s my advice: No crew should travel for months on end and pull up to an NEO that’s smaller than their own spacecraft! In short, we need to know where to go.

  In July 2011 the report Target NEO: Open Global Community NEO Workshop was issued, based on a meeting held at George Washington University earlier that year. The document pointed out that programs and planned missions to asteroids may be leveraged for mutual benefit in terms of data exchange. It also recommended coordination with the European Space Agency and other space agencies on a planetary defense demonstration mission.

  Piloted space exploration vehicles might approach an asteroid.

  (Illustration Credit 5.10)

  The report points out that a target NEO will need to be discovered several years in advance to provide adequate lead time to deliver robotic precursor missions to scope out the object, plan the human mission, and then send the crew to the chosen objective.