Supersonic Flight: The Shape of Things to Come (Part 2) December 12, 2012Posted by Lofty Ambitions in Aviation.
Tags: Airshows, Concorde, Museums & Archives
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In last week’s blog post, we discussed one of the great impediments to commercially successful supersonic aircraft: the sonic boom. A theory based on shaping of supersonic booms in order to reduce the pressure wave—the noise—began to emerge in the late 1960s.
The theoretical models—first developed by two Cornell University aerospace engineers, Richard Seebass and Albert George—focused on techniques for the reduction of the first or front part of the supersonic N-wave. Despite the development of Seebass-George theory in the late 1960s, it wasn’t until the early 1990s that the computational resources—in the form of more capable Computational Fluid Dynamics software enabled by faster hardware—necessary to design the shape of the test aircraft in accordance with the dictates of Seebass-George theory became available. Nearly thirty-five years passed before this theory was subjected to flight-testing in August 2003 and January 2004 as a part of the DARPA Quiet Supersonic Platform (QSP) program.
During the QSP program, Seebass-George theory eventually met practice in the guise of the SSBD aircraft, a heavily modified F-5E. The F-5E was chosen after flight test program proposals based on modifying a Firebee II drone or an SR-71 were rejected for technical risks and costs. The F-5E worked because of the wide range of nose shapes already flown as a part of the F-5 family (the nose of the reconnaissance version RF-5 differs from the F-5E, and the two-seat F-5F is different still) and because of the familiarity of one of the QSP contractors, Northrop Grumman, with the F-5. Prior to its merger with Grumman, Northrop manufactured more than 900 of the F-5E/F series of aircraft and more than 2000 of the closely related T-38 and first-generation F-5 airframes.
SSBD design work began in late 2001. Construction of the Seebass-George glove to replace the F-5E’s nose took place at Northrop Grumman’s El Segundo operation in California, and the glove was installed on the F-5E airframe in January 2003 at Northrop Grumman’s St. Augustine facility in Florida. Prior to testing, the SSBD’s fuselage was emblazoned with a paintjob that graphically depicted two N-waves superimposed upon each other, one, in red, an unmodified waveform and the other, in blue, with the “flat-top” signature that indicates a reduced sonic boom.
Most of the SSBD flight test program consisted of identical runs through Edwards Air Force Base airspace by the SSBD and an unmodified Navy F-5E. The two aircraft, flying at Mach 1.36 and 32,000 feet, were separated by 45 seconds, a timeframe deemed long enough to allow the shockwave from the SSBD to dissipate, but short enough so that the unmodified F-5E passed through an atmosphere that hadn’t evolved enough to invalidate comparisons between the two runs. Other test runs involved collecting pressure measurements from a NASA F-15B flying in the SSBD’s shockwave. A glider flying beneath the test flight path also collected test data. By the end of the two test sequences, more than 1300 sound and pressure measurements were taken on the ground and in the air.
The flight test sequence confirmed the nearly one-third reduction in the leading portion of the pressure wave by the reshaped nose (the glove), as predicted by Seebass-George theory. The test team exhibited a high degree of confidence in the theory from the beginning of the program. The results indicated that the shape of the new nose prevented the bunched pressure waves from forming into one large shock wave.
After completion of the flight tests, the SSBD aircraft was given over to the Valiant Air Command (VAC) Warbird Museum located just a stone’s throw from NASA’s Kennedy Space Center on the grounds of the TICO airport in Titusville, Florida. The VAC’s mission dictates that its collection only include warbirds. VAC Public Affairs Officer Terry Yon, a retired Army colonel and helicopter pilot who flew in Vietnam, says that the museum happily made a “squishy argument” based on the SSBD’s origins as a Navy aggressor aircraft to include it in the museum’s collection. After all, few truly unique aircraft exist, and this modified F-5E is indeed one of a kind.
If supersonic transports and business jets are ever to reach the air, let alone their potential, it must be demonstrated that they can fly over land at supersonic speeds without causing a ruckus. By confirming the potential for shaping supersonic shockwaves in a manner that diminishes their impact, the SSBD program took the first step toward accomplishing sonic boom-lite flight. As such, the SSBD program is destined to have long-lasting effects.
Bernard Roussett, COO of HyperMach, one of the companies announcing an super-sonic business jet at Le Bourget 2011, told us in an email about the SonicStar: “Yes, our solution for reducing significantly the sonic boom at high mach number (still supersonic!) is partly inspired from the DARPA program.” Only months before Concorde flew its final commercial flights, the SSBD aircraft made a supersonic future seem possible again.
Supersonic Flight: The Shape of Things to Come (Part 1) December 6, 2012Posted by Lofty Ambitions in Aviation.
Tags: Airshows, Concorde, Dryden Flight Research Center, Museums & Archives
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Concorde, known for its supersonic, trans-Atlantic flights of yesteryear, was in the news just past week, as a French court overturned manslaughter convictions and upheld civil damages in relation to the Air France 4590 crash in 2000. To some, this story might seem an afterthought to the dashed hopes for supersonic flight.
The dream of commercial, supersonic transports capable of safely and cheaply whisking business passengers through a geographically dispersed day, breakfast in London, lunch in New York City, and back to London for dinner, is nearly as old as supersonic flight itself. By the mid-1950s, mainstream publications like the Saturday Evening Post were breathlessly predicting, “No doubt we’ll be flying faster than sound by the thousands in a few years.”
The closest that commercial aviation ever came to realizing that prediction was Concorde. But Concorde, never able to fly profitably even in the best of times, was done in by steadily increasing fuel costs, decreased travel after 9/11, and a deadly accident. It’s been nearly a decade since Concorde’s last revenue flight in 2003.
Less than a decade ago, test flights by the Shaped Sonic Boom Demonstration (SSBD) aircraft renewed hope for commercially viable supersonic flight. New designs for commercial supersonic aircraft turn up at the major international air shows regularly and increasingly target the lucrative business-jet market, the so-called supersonic business jets (SSBJ). These designs owe much to the ground-breaking technology established by the SSBD.
In the days prior to this year’s Farnbourough International Airshow, media outlets were rife with rumours of an announcement that had NASA joining forces with some combination of Gulfstream, Boeing, or Lockheed-Martin to bring a version of the X-54 SSBJ to market by 2030. Despite the frenzied anticipation, no such announcement was made.
At Le Bourget 2011, the Euro-conglomerate European Aeronautic Defence and Space Company (EADS), the parent company of Airbus, announced the Zero-Emission High Speed Transport (ZEHST), a technology demonstrator featuring three separate propulsion systems—turbofan, ramjet, and cryogenic rocket engines—that will take to the skies in 2050. A second design, the SonicStar, a supersonic business jet with a more immediate timetable of first flight in 2021, was also announced at Le Bourget 2011, presented by British aerospace startup HyperMach. Both designs claimed to incorporate engineering solutions for addressing an aspect of the fundamental physics of supersonic flight that has accompanied every breaking through the sound barrier since Chuck Yeager’s 1947 flight, the sonic boom.
The passage of an aircraft through our planet’s ocean of air is often likened to a boat moving across the water. The boat’s passage is marked by waves of reflected energy as its hull pushes through the water. Visualizing a boat’s wake is misleading to a degree because we only see the two-dimensional “V” spreading out from the boat on the water’s surface. In reality, the mechanical wave and its associated pressure increase are also spreading out underneath the boat. In physics, a mechanical wave is one that requires a medium—water for the boat, air for the airplane—in which to travel, as opposed to an electromagnetic wave, which can propagate in a vacuum.
The mechanical waves generated by an aircraft are sound waves, miniscule increases in pressure generated by the aircraft’s body pushing and compressing air molecules as it passes. Below the speed of sound, these pressure waves radiate outward from the aircraft in three dimensions. As an aircraft approaches the speed of sound (761 mph at sea level and 59 F), the pressure waves are only moving slightly faster than the aircraft, so they bunch up together just in front of the aircraft’s surfaces (cf. “Supersonic Revolution” by Richard Hallion, Aviation History, July 2011): the nose, the wing leading edges, and the empennage. As an aircraft reaches the speed of sound, the bunched pressure waves actually combine into a big single shock wave. That shock wave is heard as a sonic boom.
The sonic boom is characterized by the dramatic increase in pressure at the aircraft’s nose and by a steady decrease in pressure to below atmospheric levels at the aircraft’s tail. After the supersonic aircraft passes, the pressure sharply increases to return to atmospheric levels. The two pressure increases—one at the aircraft’s nose and the other after it passes—produce the sonic boom’s double-bang sound. This sequence of increase–linear decrease–increase in pressure gives the wave its characteristic shape (up, down, up) and name: the N-wave.
In an interview for the NOVA program Supersonic Dream on Concorde, James Hamilton, at one-time the Director-General of Concorde, compared the sound of an aircraft approaching at subsonic speeds with the surprise arrival of sound associated with a supersonic aircraft: “You hear nothing until you get all the noise collected together, as it were, and when that happens, instead of a getting a continuous rumble of noise, you get a very sharp boom.”
Federal Aviation Regulation 91.817 prohibits flying over land at supersonic speeds for civil aircraft in the United States. The regulation specifies that aircraft “will not cause a sonic boom to reach the surface within the United States.” In the mid-1960s, the FAA, NASA, and the U.S. Air Force conducted a six-month experiment into the effects of sonic booms on a human population by performing supersonic overflights of Oklahoma City. Using a mixture of F-101s, F-104s, F-106s, and B-58s, the experiment, initially designed to provide favorable support for continuing the development of an American version of Concorde, the supersonic transport (SST), subjected the residents of Oklahoma City to 1,253 sonic booms. In the end, public outcry led to the early cessation of the experiment and, ultimately, a class action suit that the government lost.
After it was prohibited by law, the inability to conduct overland supersonic flight restricted the usefulness and profitability of Concorde by limiting it to a handful of transatlantic routes.
The X-54, ZEST, and SonicStar are being designed to make use of sonic boom mitigation techniques, techniques that will attempt to reduce the pressure wave that reaches the ground by shaping the shock wave that emanates from an aircraft traveling faster than sound, techniques that were pioneered by the SSBD.
Next Wednesday, we’ll take a closer look at this aircraft with looks that only an engineer could love.
Tags: Apollo, Concorde, Dryden Flight Research Center, GRAILTweetup, Movies & TV, Museums & Archives, Space Shuttle
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A clear and consistent message was delivered at both the #DrydenSocial and last fall’s GRAIL Tweetup: NASA wants to use social media to help spread the word of its achievements. To that end, NASA trots out its best and brightest to address event attendees and then mixes in the kind of moments that only NASA can deliver.
To that end, the morning session of the May 4th NASA Social event at NASA’s Dryden Flight Research Center (DFRC) offered a broad overview of Dryden’s historical and continuing role in aeronautics research. David McBride, Center Director for DFRC and Christian Gelzer, Chief Historian, provided a wealth of contextual information in the day’s first two talks.
The wonderful Neil deGrasse Tyson, Director of the Hayden Planetarium and whose book, Space Chronicles: Facing the Ultimate Frontier, Anna has just finished reading, has been making some interesting comparisons regarding NASA’s budget of late. According to Tyson (watch the video HERE), the $850 billion spent on TARP, the Troubled Asset Relief Program, is greater than NASA’s budget for the fifty-plus years that NASA has been in existence.
In no particular order, here are some the achievements that NASA’s budget has funded in that five-decade span:
• the Hubble Space Telescope and its associated increase in our understanding of the universe;
• a significant portion of the International Space Station (ISS);
• the Space Transportation System (the shuttle) that carried Hubble and the ISS’s pieces into orbit;
• deep space probes such as the Voyagers, planetary landers and rovers such as Spirit, Opportunity, and Curiosity;
• myriad Earth-orbiting satellites that have taught us much about our planet’s weather, composition, and history;
• and of course, the Apollo program and the astronauts who landed on the moon.
Note that all of these scientific and engineering achievements have something to do with space. Space is sexy, space gets people’s attention.
That said, the first A in NASA is for Aeronautics. In recent years, aeronautics has been a remarkably small piece of NASA’s little pie. In his introduction to the NASA Social #DrydenSocial attendees, David McBride, Dryden’s Director, pointed out that aeronautics research receives about 2.5% of NASA’s roughly $18 billion dollar budget in any given year. Those monies go towards funding the four dedicated NASA Aeronautics Research Centers: Langley, Glenn, Ames, and Dryden. At the end of that quickly narrowing financial funnel, Dryden Flight Research Center (DFRC) receives less than 1% of NASA’s budget.
It turns out, however, that the first A in NASA is a really important part of the United States’ overall economic picture. McBride indicated that the manufacture of aircraft and its associated industries were the single greatest positive contributor to the U.S. balance of trade. NASA’s own web pages put the scope of aviation’s influence in the U.S. economy as follows:
“Aviation generates more than $400 billion in direct economic activity, supports more than 650,000 jobs and accommodates more than 600 million passengers every year in the United States.”
At last fall’s GRAIL Tweetup, Charlie Bolden also addressed the importance of aeronautics, when he said that he would like a part of his legacy as NASA Administrator to include leaving funding for aeronautics research on a “upward trend” in order to return NASA to its traditional status as the “premier aeronautics research organization in the world.”
The technical talks at #DrydenSocial started with engineer Ed Haering, who is a superstar in the world of supersonic booms. Haering’s presentation covered work that has been done at DFRC to mitigate—sshhh!—supersonic booms. Because commercial aircraft are prohibited from flying over land at supersonic speeds (this was a huge problem for Concorde), this research is imperative if we’re ever to see another supersonic transport aircraft. The Lofty duo actually had the opportunity to see some of Ed’s work up close and personal when we visited Valiant Air Command in Titusville, Florida. Valiant is the home of the Shaped Sonic Boom Demonstration (SSBD) aircraft, a test aircraft on which Haering worked at Dryden. As its name suggest, the SSBD successfully demonstrated that a sonic boom could be shaped to reduce its impact, and by impact, we mean noise.
On the heels of Haering’s talk was an opportunity head outside and experience a sonic boom firsthand. Shortly after the #DrydenSocial attendees were led outside for a photograph beneath the wings of the X-1E, an F-18 flew overhead accompanied by the telltale crack of a sonic boom. Moments after that, the same F-18 treated us to a loud-and-low flyby.
In a day of artifacts and factoids, one that would have made a great impression on Anna, had she been there too, concerned the front of Dryden’s administration building. As we gathered around the X-1E, one of the handlers assigned to our group related that the front of the administration building had stood in for the NASA’s offices in I Dream of Jeannie. (If you want to read more about I Dream of Jeannie, click HERE.)
For Doug, though, the artifact that made the greatest impression was the insect-like Lunar Landing Research Vehicle (LLRV, in the photo above) which was located in a nearby hangar. The M2-F2 lifting body, used to validate the design of the space shuttles and located in the same storage space as the LLRV was a close second.
On This Date: Radium, Tu-144, and Earthquakes December 26, 2011Posted by Lofty Ambitions in Aviation, Science.
Tags: Airshows, Concorde, Earthquakes, Nobel Prize
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On most Mondays, we post either a piece by a guest blogger (first and third Mondays) or a video interview (second and fourth Mondays). We do have video interviews queued up for the new year (and just wait ’til you see who!), but today we take the opportunity for one of our “on this date” posts.
In 1898, just three years into their marriage, one of our favorite collaborative couples of yesteryear announced at the French Academy of Sciences that they’d isolated radium. Marie and Pierre Curie had isolated the element five days earlier, though it wasn’t named until the following year. They did come up with the term radioactivity, and radium was the second ray-producing element they’d discovered that year. The first was polonium. They continued to work with an enormous amount of pitchblende to isolate a wee bit of radium. And they didn’t patent their processes, thereby allowing the larger scientific community to readily use their work.
Radium was applied as luminescence on watch dials and aircraft switches, which, it turned out, was quite dangerous for those who painted those dials and switches. It was also added to cosmetics before such a glow was considered hazardous. Later, it was used to treat cancer, though, of course, because it is radioactive and because the body processes it like calcium, it likely caused the leukemia and related illnesses from which Marie Curie died in 1934.
Marie Curie was awarded her second Nobel Prize in 1911, this time in chemistry, in part for her role in discovering radium. (Because Pierre died in 1906, he did not share in this award.) Her earlier Nobel Prize, which she shared with Pierre and Henri Becquerel in 1903, was in physics for their work in radiation. She was the first woman to be awarded a Nobel Prize, the first person to be awarded a second, and one of just two people to be awarded Nobel Prizes in different fields. (Linus Pauling is the other.) We’ve written about Marie Curie before—click HERE to read more.
Today is also the anniversary of the Tupolev Tu-144’s entry into supersonic transport service in the Soviet Union. The Soviet government began developing this aircraft in 1963. But the first production airliner crashed at the Paris Air Show in 1973. Accusations of espionage and cover-ups surrounded the investigation. With delays after this debacle, the Tu-144 ended up first flying mail on this date in 1975, with commercial flights beginning almost two years later (and almost as long after Concorde started its commercial routes). The Tu-144, which shares so many design cues with Concorde (dropped nose, cranked wing, and slender fuselage) that its nickname in the Western press was Concordski, was riddled with problems and had only a short commercial run, flying passengers from November 1, 1977 through June 1, 1978. A more recent use of the Tu-144 was as a flying laboratory for NASA.
This past year, one of the top news stories was the earthquake and tsunami in Japan and the subsequent damage to the nuclear power plant at Fukushima Daiichi. (Read some of that HERE and HERE.) Today is the seventh anniversary of another devastating earthquake, a 9.2 (numbers vary by source) quake in Indonesia, India Thailand, and the surrounding areas, that also produced tsunamis. It was so strong that some estimate that the entire world moved a full centimeter. As with most recent earthquakes, this one in the Indian Ocean was the result of subduction, or one tectonic plate scraping under an adjacent tectonic plate. In this case, hundreds of miles of a tectonic plate moved about 50 feet.
When this subduction occurred, the seabed rose, pushing water up. In the vast, deep ocean, that sort of wave isn’t much of a problem and is difficult to detect. But as the tsunami reaches shores, the wave can be devastating, and no warning system was in place for the Indian Ocean. The tsunami, of course, reached different shorelines at different times—several minutes or several hours—depending on the distance of the land from the earthquake’s epicenter. In some places, the waves washed a mile inland.
This natural disaster killed almost 230,000 people and is considered one of the ten deadliest natural disasters of all time. In addition to the cost of human life, it devasted coral reefs and wetlands and contaminated freshwater sources. Haiti’s earthquake, the second anniversary of which occurs next month, was even deadlier. Earthquakes change the face of the earth and the faces of the world.
Last Flight of the Concorde November 26, 2011Posted by Lofty Ambitions in Aviation.
Tags: Concorde, Museums & Archives
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Supersonic passenger flight ended on November 26, 2003, the day a Concorde made its last flight, this time back to its birthplace in Bristol, England, where it was put on outdoor display. The Concorde’s last transatlantic flight had occurred roughly a month earlier (see video below).
The Concorde, a joint venture between the United Kingdom and France was riddled with problems right from the start, right down to whether the name should be spelled with (British) or without (French) the e on the end. Still, orders for more than 100 aircraft poured in, the industry was jazzed about this revolution, and construction of the aircraft began in 1965.
The drop nose and delta wing are among Concorde’s distinctive features, the former needed for pilots to see the runway and the latter developed to allow the plane to reach a speed of more than Mach 2 (about 1320 milies per hour). But supersonic flight at high altitude presented challenges for engine design, heating and cooling, braking, and cabin pressurization. And the price of fuel was rising. Only 20 aircraft were built, 14 of which were used for passenger service. The first scheduled flight occurred on January 26, 1976. But protests led Congress to ban Concorde landings. Even after the federal ban was lifted, New York City instituted a ban.
The Supreme Court ended that prohibition, and flights from London and Paris to New York began on November 22, 1977. The record time between Heathrow and New York is 2 hours, 52 minutes. The public outrage subsided, as celebrities and the wealthy (Paul McCartney was a favorite of the crew) zipped back and forth across the Atlantic. The Concorde served more than one million bottles of champagne.
Doug toured the inside of the Concorde at the Museum of Flight in Seattle, where it sits outdoors. Anna saw the Concorde during its restoration at Scotland’s National Museum of Flight in the summer of 2004. Together, we’ve seen a Concorde sitting in the distance as we landed in Birmingham, England, and up close at the National Air and Space Museum’s Udvar-Hazy facility. The shape and size is pencil-like, as airplanes go, with the cabin ceiling just six feet from its floor and little room for carry-on baggage. When you look at this supersonic jet, you sense the speed it could achieve. But today marks the eight anniversary of its becoming an artifact.
Air France Flight 4590 July 25, 2010Posted by Lofty Ambitions in Aviation.
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Today is the tenth anniversary of the crash of Air France Flight 4590 just after take-off from Charles de Gaulle International Airport. The Concorde jet’s tire was ruptured by a small piece of titanium (Anna’s favorite metal) left on the runway after the previous plane took off. A chunk of the Concorde’s tire hit the wing, which led to a rupture in a fuel tank. The leaking fuel was ignited by electrical wiring. An article in the U.K.’s Guardian points to additional factors, such as weight, maintenance, and proximity to another aircraft carrying France’s president. One-hundred nine souls on board and five people on the ground perished on July 25, 2000.
In the wake of the accident, the supersonic jet was grounded. Almost a year later, flights were resumed, but the Concorde was retired on November 26, 2003, ending supersonic passenger service worldwide. In 1982, the price of a round-trip ticket was $3900, and by 2000, the price had more than doubled. United States astronauts outnumber Concorde pilots. It was a rare instance, this aircraft.
We’ll have more on the Concorde in future posts.