Author Archives: The National Air and Space Museum

Chicken Little Was Right

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Yes, the sky is falling. The asteroid impact that took place in Chelyabinsk, Russia, on February 15, 2013, has jump-started an international conversation about planetary protection and whether or not there is a really big asteroid/meteor/comet out there with our name on it. There is, we just haven’t found it yet. Miniscule objects enter the atmosphere all the time; occasionally larger objects come down—the Tunguska (1908) and Chelyabinsk (2013) events are prime examples of this—and once in a very great while a mass extinction impact takes place as in the Cretaceous–Paleogene extinction event of 66-65 million years ago that wiped out the dinosaurs.

chelyabinsk object orbit

The estimated orbit around the Sun of the Chelyabinsk object. It illustrates the orbits of Venus, Mars and Earth, together with the Sun and Earth at impact. The illustration is based on data provided by Dr Peter Brown.

I first heard a scientist talk about this in 1992 when he explained that several thousand interplanetary objects were on collision courses with Earth, and that several small pieces entered the atmosphere every day. It is only a matter of time before a really large one hit the Earth, and the results could be catastrophic. The scientist urged the cataloging of all possible Earth-crossing asteroids, the tracking of their trajectories, and the beginning of research and development on countermeasures to deal with those objects heading for Earth.

Most of the audience departed this speech with mixed feelings, recognizing the reality of what had been said and also denying that it bore any relationship to reality. Indeed, while the scientific theory that a great galactic meteor slamming into the Earth had created a form of “nuclear winter” that made the dinosaurs extinct was gaining currency at the time, few believed a real threat existed in the present. After all, at that time the United States had just achieved the most impressive triumph of its history, defeat of the Soviet Union in the Cold War and stood essentially omnipotent in the world as a superpower. Now another threat is before us: this time it’s from space and there is currently no technology to defeat it.

Now with the Chelyabinsk event as a modern object lesson, there is reason to take seriously the need to mitigate asteroid, comet, or meteor impacts in the future. A major divergence of opinion concerns how the United States should respond to this threat of impact. Most scientists conclude that there is a significant risk and that governments should take some action (especially in searching for Earth-crossing asteroids), but that it is premature to expend enormous amounts of funds for defense systems in the absence of a specifically identified threat. Military leaders argue strongly for a more aggressive approach to asteroid defense. Many assert that the United States must start immediately to develop technology to deflect an object heading for Earth.

This policy debate makes for excellent news stories, and reporting has tended to state the extremes rather than the middle ground that actually dominates. What is taking place is actually quite appropriate for the level of the potential threat to the planet. Efforts are underway to catalog all potentially threatening objects and to strategize on how to prevent cosmic-induced chaos through such means as evacuation or the use of weapons of mass destruction to shift an incoming object’s path away from Earth.

Could viable options be developed to mitigate any threat were it detected years or even decades ahead of time? With that much advance notice, we might be able to reach an asteroid with a robot that could nudge it enough to cause it to miss Earth. Changing the asteroid’s speed by only a small fraction of one mile per hour would be sufficient if action were taken early enough. Some proposed schemes include:

  • Crash a rocket into one side of the asteroid to deflect its course. This plan would be most feasible for asteroids less than about 300 feet wide.
  • Explode a neutron bomb in space at some distance from the asteroid. The explosion would almost instantly heat one side of the asteroid, causing chips of rock to explode away. By the principle of action and reaction, the asteroid would begin to drift slowly in the opposite direction.
  • Land some kind of rocket engine on the surface of the asteroid and operate the engine for several years, pushing the asteroid gently into a new orbit.

Rapid advances in technology in the coming decades may reveal other, better methods that cannot be foreseen for dealing with these possibly threatening objects.

Can human efforts prevent catastrophe from a large asteroid or comet? The answer is yes, if it is detected sufficiently early. A rocket full of (probably nuclear) explosives would have to be launched. One would not try to destroy the object since this would cause it to fragment into pieces leading to an equally destructive “multiple warhead,” much like the case of comet Shoemaker-Levy 9 that blasted Jupiter in 1994. Instead, the explosion would need to take place next to the object. This would create a small change in its direction of motion, causing a significant deviation in its orbit over time and distance.

Jupiter

Comet Shoemaker-Levy 9 was a comet that broke apart and collided with Jupiter in July 1994. Brown spots mark impact sites on Jupiter’s southern hemisphere.

With current technologies, an Earth-striking asteroid or comet would have to be detected years, perhaps decades, in advance for preventative measures to be effective. The lead time is determined by the size of the object and its trajectory. It is yet to be determined if the technology is sufficient to meet this very real possibility. Concerning this, the late Congressman George Brown stated in 1993: “If some day in the future we discover well in advance that an asteroid that is big enough to cause a mass extinction is going to hit the Earth, and then we alter the course of that asteroid so that it does not hit us, it will be one of the most important accomplishments in all of human history.”

Of course, there is another answer. If we find something coming toward us, we could round up a bunch of oil riggers from the Gulf, put them under the command of Bruce Willis, fly a space shuttle up to rendezvous with the object, plant bombs on it, and blow it up. After all a blockbuster feature film, Armageddon, was based on this premise. For so many reasons this scenario is not an option. It is actually a ridiculous storyline. It is not ridiculous, however, to undertake appropriate steps to mitigate this interplanetary threat. Increasing funding for research and development toward the deployment of countermeasures, as well as all sky surveys to find and track near Earth objects, is an appropriate response.

Roger D. Launius is a senior curator in the National Air and Space Museum’s Department of Space History .

Vulcan? But that’s not logical…

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The news that “Vulcan” topped the poll results taken by the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, California as a possible name for one of the two tiny moons newly discovered to be orbiting Pluto has gotten quite a bit of press this week. In 2012, Mark Showalter of SETI, working with scientists on the New Horizons mission sending a probe to Pluto, found a tiny fifth moon orbiting the icy world. Showalter was also the lead author of the discovery of a fourth moon in 2011 using observations from the Hubble Space Telescope.

Pluto

This image, taken by NASA’s Hubble Space Telescope, shows five moons orbiting the distant, icy dwarf planet Pluto.

As SETI contemplated what names to propose for these two newly-discovered moons, they opened the question to the public in an on-line poll.  Inspired by a tweet from William Shatner, the actor who became famous playing Capt. James T. Kirk in the original Star Trek television program (1966-69), Vulcan, Pluto’s mythological nephew and the name of a fictional world in Star Trek’s imagined universe, became the top vote getter.  Leonard Nimoy, who played Spock, the most famous Star Trek Vulcan, reportedly tweeted that naming one of the two moons “Vulcan” would be the “logical choice.”

shatner

nimoy

But did you know that there already was a Vulcan?  Or, actually, there wasn’t.  But astronomers thought that there was.

Since the 18th century, astronomers worried that the orbit of the innermost planet in the solar system, Mercury, did not behave the way that they expected.  By the mid-nineteenth century they knew that perturbations in the orbit of Uranus had just (in 1846) resulted in the discovery of Neptune, the first planet to be predicted mathematically before it was confirmed through observation.  Could that also apply to Mercury? Was there another planet orbiting between Mercury and the Sun that could explain Mercury’s orbit?  Urbain Jean Joseph Leverrier, whose calculations had been used to discover Neptune, thought so.  By 1859, amateur and professional astronomers started searching.

And they found some things.  Some scientists reported seeing a bright, star-like object orbiting near the Sun.  And others saw circular shapes transiting (or crossing) the face of the Sun. It must be Vulcan, they thought!  Some textbooks printed in the 1860s and 1870s even listed Vulcan as a planet. (For, indeed, Pluto is not the first body to have been considered a planet and then reclassified. Ceres, the spherical body in the asteroid belt, was also called a planet when it was discovered in 1801 but then reconsidered when the many other bodies discovered in that same region of space became known as the asteroid belt.)  But the observations of Vulcan did not compute.  They were not consistent.  According to Newton, and to vast experience, planets, above all, were predictable in their orbits. Any deviation was not acceptable.  That’s how Kepler decided that planets did not travel in circular orbits. So when scientists looked for Vulcan where it was predicted to be visible and they could not find it, they started to doubt that Vulcan existed.

When something does not move as predicted, astronomers start looking for a perturbing mass.  That is in fact how dark matter was detected, and after almost 50 years, finally accepted as a major factor in controlling the motions of things like stars and galaxies in the universe.  In the early 20th century, astronomers thought that the existence of a faint disk of material around the sun, called the Zodiacal Light, might be massive enough to make Mercury’s orbit shift in the way it appeared to do.  But in the end, Einstein solved the problem (literally) and Vulcan was no more.  In 1915, Einstein’s General Theory of Relativity explained the shifts in Mercury’s orbit without the presence of another world orbiting nearer to the Sun.  Vulcan, which had never existed, entered the history books.  But astronomers still use the name: NASA’s project to detect new planets has been called “Project Vulcan.”

The names of Pluto’s moons have still not been decided.  The International Astronomical Union, the worldwide professional organization of astronomers, will make the final choice.  They may choose “Vulcan.” Or they may decide that there was already a Vulcan. Except that there wasn’t.

Margaret Weitekamp and David DeVorkin are curators in the Space History Department of the National Air and Space Museum.

Two Years Ago Today

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Two years ago today, the space shuttle Discovery was launched for the last time.  My friend Nicole Gugliucci scored a quartet of tickets for the launch and shared them with me, along with our friends and classmates Joleen Carlberg and Gail Zasowski.  Facing an overwhelming load of graduate school work, we decided that a road trip from Virginia to Florida was exactly what we needed!

Kennedy Space Center

Joleen, Gail (with Buzznaut), Nicole, and myself (with Meteor Shower), at the Kennedy Space Center.

Many hours later, the six of us found ourselves in sunny Florida.  Yes, six.  The other two road trippers were the mascots for an astronomy outreach club that we helped found in Virginia.  Nicole was the only one among us who had witnessed a launch before.

Our tickets let us watch from the Visitor Center, seven miles from the launch pad.  We spent the day exploring the Visitor Center, and found a spot in the rocket garden to watch the launch.  We couldn’t see the launch pad itself from there, but we could watch final preparations on a big screen showing a close-up view.

Rock Garden

Waiting for launch in the rocket garden.

Due to a computer problem on the ground, the launch was delayed.  We knew we could still see it if it were postponed one day, but if there were further delays, we would probably have to abandon the effort and drive home.  The tension in the crowd built until the countdown clock started again, with just three seconds to spare in the launch window. The audience erupted into cheers.

The experience didn’t start to feel real to me until I saw the cap lift off the shuttle’s nose cone, leaving it free to launch.  Sparks were fired around the main engines to burn up any stray fuel, preventing accidental fires.  Then, on the screen, we saw the engines light!

launch

Ignition of main engines, as seen on a big screen from the Visitor Center. Video of Discovery’s last launch can be seen in the Moving Beyond Earth gallery or online.

The red flames from the engines focused in to sharp white points, causing the shuttle to “twang,” rocking forward a bit.  When it rocked back to a vertical position, the more powerful solid-fuel rocket boosters (SRBs) lit off.  I was expecting that, but it still made me jump.

Moments later, we felt the ground shake, and then the shuttle rose into view, the flame from its SRBs shining nearly as brightly as the Sun. It hurt to look at it.  A few moments later, as we jumped around and cheered, the rumble and roar of the launch reached us.

Discovery

My first glimpse of Discovery. The white strips are the solid-fuel rocket boosters.

It was awesome to see this feat of engineering with my own eyes, and to think that there were six people in that shuttle, with an incredible amount of flame and power below them.  As Discovery arcked out of sight into a clear blue sky, I found myself crying.

Discovery

Discovery reappears from behind its own contrail, on the last gasps of power from the SRBs. Moments later, the empty SRBs detached and fell back to the ocean.

But that was not the last flight of Discovery that I got to witness.  More than a year later, on April 17, 2012, I was working as an astronomy educator at the National Air and Space Museum. The whole city of Washington, DC was buzzing with excitement about Discovery, which was en route to its final home with us.

Riding piggyback atop a modified Boeing 747, Discovery cruised the DC area, making three loops around the National Mall before heading to Virginia.  From the top of the National Museum of American History, I was lucky enough to watch its final flight.

Discovery

Flying above the Smithsonian Castle, Discovery acquires an extra honor guard.

Anyone can now visit Discovery at the National Air and Space Museum’s Steven F. Udvar-Hazy Center.  When I visit, what impresses me most is how beaten up it looks, compared to the pristine Enterprise which used to reside there. Discovery is a well-used workhorse of a space vehicle, the one that took the Hubble Space Telescope into orbit for us.

Discovery

Visiting Discovery at its new home.

I’m not sad that the space shuttle program is over.  I believe that ferrying people and equipment from Earth to low orbit is now a routine (if still astonishing!) task, one that private industry will excel at. I can’t wait to see where scientists and engineers will take us next. What would you like to see in the future of space exploration?

Geneviève de Messières is an Astronomy educator at the National Air and Space Museum in Washington, DC. All photographs by Geneviève de Messières.

Civil War Planes

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In a recent post, Tom Paone described the plans of William Powell, a resident of Mobile, Alabama, for a Confederate helicopter. In fact, Powell’s scheme was only the tip of the iceberg. In researching a scholarly paper on Civil War Planes, I have catalogued a score of plans for powered flying machines developed on both sides of the battle lines. Perhaps the most interesting of these was the work of Colonel Edward Wellman Serrell , a professional engineer serving with the Union Army of the James in 1864. Inspired by the well-known hand-held helicopter toy, Serrell had begun studying aeronautics several years before the War. Once in uniform he conducted full-scale tests of metal rotor blades in the field, then convinced his commander, General Benjamin Butler, to order him to duty in Philadelphia, where he raised the money with which to build his Reconoiterer, a flying machine designed to conduct reconnaissance missions over enemy lines.

 

Reconoiterer

The Serrell Reconoiterer. Credit: Greg Bryant.

The machine would be lifted into the air by twin rotary wings set above and below the fuselage, and driven forward by propellers at the front and rear. Two large flat copper plates, each measuring nine feet in span and 45 feet, 8 inches long, were to be positioned on either side of the shell. The two plates were connected to a crank running through the fuselage, so that the crew could incline or depress the wings up to six degrees above or below the horizontal to provide additional lift.

Plans called for the fuselage to be a cigar-shaped copper shell measuring 52 feet long, with landing runners on the underside. A chamber at the bottom of the shell would serve as a reservoir for the boiler water, with a second chamber above it for the coal. A light-weight, high pressure vertical steam engine with a vertical boiler were housed in the rear of the shell. A series of moveable balls were to be used to balance the Reconnoiterer. The designer estimated the total weight at take-off, with a crew of three on board and enough water and fuel for an eight-hour flight, at 8½ tons.

 

Reconoiterer

Serrell’s drawing of the rotors, steam engine and transmission of the Reconoiterer

Unlike William Powell, and most other armchair aviators of the Civil War era, Serrell conducted serious engineering tests, obtained what he thought would be a suitable steam power plant, and had large sections of the hull of a smaller three-man demonstration craft under construction when hostilities ended. He continued his effort for a time, corresponding with leading aeronautical researchers in Europe, but ultimately abandoned the venture when it became apparent that steam propulsion was inadequate.

Serrell

Edward Wellman Serrell (1826-1906)

While Serrell and others who dreamed of winged flight during this era were destined never to get off the ground, the number of flying machine projects that appeared during the middle years of the nineteenth century underscores American enthusiasm for technology, even for the possibility of a machine that most feet-on-the-ground citizens regarded as something akin to a perpetual motion machine.  Dreamers and doers like E.W. Serrell deserve to be remembered.

Fortunately, the collection of research materials regarding what might be thought of as the pre-history of aviation continues to grow. During the course of research on aeronautical experimentation in nineteenth century America, and with the help of my colleague Mark Ragan, an important cache of Edward Wellman Serrell’s papers relating to his flight experiments was discovered in the hands of his descendants. Through the generosity of the family, the records of this pioneering foray into heavier-than-air flight are now safely preserved in the archive of the National Air and Space Museum, where they will be available to researchers in generations to come.

Tom Crouch is a senior curator in the Aeronautics Department of the National Air and Space Museum.

When Worlds Collide

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A particularly bright fireball was observed earlier today over a wide area in Russia. Of even greater significance was the very strong sonic boom associated with the passage of the meteor through Earth’s atmosphere.

News out of Russia is reporting that ‘hundreds’ of casualties resulted from people being hit by falling glass, caused by the breaking of windows by the pressure wave associated with the sonic boom. Meteors are quite common around the Earth, but one of this magnitude is fortunately a rare event. The light of the meteor trail that we see in the sky is caused by friction between the incoming fragments and Earth’s atmosphere, which rapidly heats the surface of the fragments to the point that they give off visible light. The intensity of the light is a complex interplay between the speed of the object and the increasing density of the atmosphere as it moves lower into the atmosphere. The sonic boom is a clear indication that the fragments are moving much faster than the speed of sound, and just like jets that exceed the speed of sound, it is the inability of the air molecules to move fast enough to get out of the way of the fast object that generates the shock wave that we hear as a sonic boom. If the shock wave is intense enough, it can break panes of glass, which appears to have been the case today over a large area in Russia.

On June 30, 1908, a rock estimated to about 100 meters (328 feet) in diameter exploded (because of the rapid build-up of pressure as the object got lower into the atmosphere) above the Tunguska region of Siberia, which flattened trees over 2000 square kilometers (800 square miles) and produced a shock wave that knocked people to the ground at a distance of tens of kilometers (tens of miles) from the detonation point.

This image is from the Leonid Kulik expedition in 1927.

Today’s incoming rock likely was quite a bit smaller than the Tunguska rock, although it will take time for Russian scientists to assess what damage has taken place. NASA scientists are confident that the close passage of an asteroid to Earth later today and the trajectory (the flight path) of the Russia meteor were very different, so the two events are not connected, even though they will occur within hours of each other. Both the Russia meteor and the close flyby of an asteroid are reminders that space is not completely empty; whenever Earth happens to cross the path of some solid material in space, whether the size of a sand grain or a large building, the fast-moving objects are going to interact strongly with our atmosphere.

Jim Zimbelman is a geologist in the National Air and Space Museum’s Center for Earth and Planetery Studies