Wednesday, January 1, 2014

Eastern Air Lines Flight 980

On New Year's Day, 1985, a Boeing 727 en route from Asuncion to La Paz crashed near the peak of Illimani, a mountain in the Cordillera Oriental subrange of the Andes. You can read more about that here:
Eastern Air Lines Flight 980

At 19,600 feet above sea level, the impact point remains the highest and one of the most remote airplane crash sites in the world. Due to the remoteness of the location, the airplane's wreckage wasn't found until more than 20 years after the crash, and neither the flight data recorder nor the remains of the passengers and crew have been recovered. The airplane seemed to be healthy when the crew last checked in with Bolivian air traffic controllers, and it seems the crash was a controlled flight into terrain due to poor visibility in the region on the day of the crash and spatial disorientation on the part of the crew. There are few places on Earth where the topography of Earth challenges pilots at 20,000 feet, but the Andes range is one of them, and it seems the ship's, crew's, and passengers' luck ran out as they wandered through a pass in the wrong direction in low visibility.

Besides the height of the crash site, flight 980 is notable for being the first fatal aviation accident of 1985. It was a harbinger of something wicked on its way. 1985 turned out to be the most horrific year in the history of civil air transport to date. Over 2,000 passengers and crew would be lost in aviation incidents, including the worst single-airplane accident ever and the worst terrorist bombing of a single airplane. Something had to change, and over the last three decades it has. The crash of an Asiana 777 last summer was the first fatal accident for an airplane that has been in service for 18 years and the first on US soil in four years. There will always be risk in slipping the surly bonds of Earth, but the management of this risk over the history of aviation is one of the greatest success stories of modern engineering. Thank goodness 2014 is unlikely to be much like 1985.

Tuesday, December 31, 2013

Admiral Grace Hopper to ZMC-2

Image credit

So far I've written 149 entries in this blog. Some of those were basically content-free, but others covered multiple topics, so that's a reasonable estimate for the number of things we've talked about. Some of the topics I focused on were predictable (for me anyway), like space history and structural failure, while some were a bit of a stretch, like nuclear physics and the Iranian hostage crisis. Some were fun and crossed over between multiple topics, like space, history, and nuclear bombs, or geology, natural history, and nuclear engineering. Some stuff was just weird. I think that I gave a passable description of orthodox Christian things, which is cool because that's not at all my area of expertise.

The top-five most popular posts of 2013 are as follows:
1) Naked mole rat
2) Space elevator
3) Aloha Airlines flight 243
4) The Hyatt Regency walkway collapse
5) Project Azorian

Given that greatest hits list, it sounds like animals, advanced space concepts, plane crashes, failure, and spy stuff are popular topics. Should I write more about these things? I mean, I can write about whatever I want, but presumably I do this for a reason. Feedback is appreciated, especially since the comboxes on this blog are typically pretty quiet.

The idea when I first started this blog was that I'd post daily, or as close to daily as feasible. That's probably not very realistic, and my actual on-base percentage was closer to 40%. That seems reasonable, and my objective for next year is to achieve something close to that but more evenly-spaced throughout the year. Thanks to everyone who's read this space so far, and I hope to see y'all back in 2014.

Monday, December 30, 2013

The Megatons to Megawatts Program

Over the last two decades about 10% of the electricity generated on the American power grid came from decommissioned bomb material produced by the Soviet Union during the Cold War. The program to convert Russian bomb-stuff into American power-stuff was officially known as the "Agreement between the Government of the Russian Federation and the Government of the United States of America Concerning the Disposition of Highly-Enriched Uranium Extracted from Nuclear Weapons," but its unofficial title had a catchier ring to it. You can read more about the program here:
The Megatons to Megawatts Program

Less than 1% of natural uranium on Earth is useful for unleashing nuclear power. Some reactor designs can get by with the natural scarcity of fissile uranium, but most require the ratio of (fissile) uranium 235 to (fertile, but non-fissile) uranium 238 to be artificially enriched to about 5% to run. Bombs require enrichment to 90% U-235 for the explosive chain reaction to work, and during the Cold War the Soviet Union stockpiled an enormous quantity of highly enriched uranium (HEU) as a precursor to the manufacture of nuclear and thermonuclear bombs.

What the Soviets actually planned to do with all this uranium isn't exactly clear. By the breakup of the union, Russia had a stockpile of 500 metric tons of HEU, enough to build at least 20,000 nuclear warheads. Short of fending off a fleet of invading alien starships, it's difficult to conceive of any possible justification for that much firepower, and weapons-grade uranium sitting inert in a warehouse wouldn't have done much good strategically or tactically had the Cold War ever gone hot. Since evil invading aliens don't seem to be on the way, American diplomats proposed downblending the weapons-grade stock to reactor-grade uranium, and consuming the converted explosive material in reactors across the United States. Isaiah wasn't far from the mark when he talked about beating swords into plowshares. For the last 20 years Americans have been lighting our houses with the weapons that were meant to destroy them.

Earlier this month the last shipment of downblended reactor fuel arrived from Russia. Since about half of the nuclear industry's supply of low-enriched uranium since 1993 has come from the Megatons to Megawatts program, another source of uranium will need to be found soon to keep the price of nuclear fuel from climbing. A small amount of the American stockpile of HEU has been converted into reactor uranium since the end of the Cold War, but much of it remains the stuff that makes mushroom clouds and fallout rather than the stuff that runs lightbulbs and air conditioners. Both sides of the former Iron Curtain still have hundreds of tons of plutonium, used in the primary stages of thermonuclear weapons, and this has potential for power generation as well. For now, there are many more swords in the arsenal that would better serve us as plowshares.

Monday, December 2, 2013

Advanced Gas-cooled Reactor

Once nuclear chain reactions were understood and harnessed for bombs and ships, nuclear engineers on both sides of the Iron Curtain turned their attention to the mundane but practical task of making electricity. Most nations adapted their submarine engines to the task, but the British found a different solution. 15 of the UK's 16 commercial nuclear power plants use high-temperature carbon dioxide rather than water to cool the reactor's core and heat its steam generator. You can read more about that here:
Advanced Gas-cooled Reactor

Mark's Standard Handbook for Mechanical Engineers has this to say about the thermodynamics of nuclear reactors:

...A nuclear reactor must be treated as a heat source which differs from a chemical heat source in that no oxygen is required and the heat does not have to be removed from gaseous combustion products which possess poor heat-transfer properties.

Most nuclear reactors in the United States, France, Japan, and the former Soviet Union (the largest producers of nuclear power) use water to channel the immense heat released when uranium atoms split to engines that convert some useful fraction of this heat into electricity. Liquid water is conductive, stable, nontoxic, and abundant where most (but not all) nuclear reactors operate, and its ability to absorb tremendous amounts of energy per unit volume lends compactness to any design using water as a coolant. Since most reactors used for commercial power share a heritage with ship and submarine propulsion systems, where space and power are precious things, much of the nuclear world gets its power from pressurized- and boiling-water reactors. The British decided to go a different route.

All else equal, the hotter a heat engine runs, the more efficient it is. Though water-cooled reactors are compact, they suffer a major problem here since water boils at a temperature well below the allowable temperatures of the structural metals that reactors are made of. Steam is far less dense than liquid water, and is impractical for use inside the reactor's core, so the boiling temperature of water imposes an upper limit on how hot water-cooled reactors can run. Increasing coolant pressure (standard practice in the pressurized-water reactors that make most American nuclear power) delays water's boiling to higher temperatures, but there are practical limits to this approach as well. The British technique of using carbon dioxide as coolant allows the reactor to run at much higher temperature and efficiency than can be achieved by the American, Russian, and French water-cooled designs. The AGRs are bulkier than their water-based cousins, but that poses little issue for powering the grid.

An interesting design feature of the AGR is that it outputs steam at exactly the same temperature, pressure, and power as previous coal-fired power plants built in the UK. This allows the generator-driving turbine to be agnostic to its power source. Heat from uranium is indistinguishable from heat from coal, but you'll breathe a little easier without all that soot in the air. If only someone would remind the the power that be in London of this...

Sunday, December 1, 2013

Luna 24

Image credit

On August 22, 1976, a Soviet robotic sample-return spacecraft landed on the surface of the Moon. As of this writing this is the most recent time that a human-built craft landed on the Moon, and you can read more about it here:
Luna 24

Luna 24 was the last in a long, distinguished, and problematic series of missions for the Soviet Union. The missions saw the far side of the Moon, touched its surface, and landed gently there for the first time. The early Luna program was a source of tremendous pride and achievement for Soviet science despite the frequent failures, but later it became clear that the Soviet space program would be unable to compete with NASA's effort to send astronauts to the Moon by the end of the decade. Since no cosmonauts would be going there anytime soon, a program of robotic rovers and sample return missions was launched in the late-1960s and early '70s.

Like the early Luna probes, most of these larger and more sophisticated landers failed. The Soviets knew their trade better in 1976 than they did in 1959, but there's a lot more that can go wrong when the mission entails collecting a sample and sending it back to Earth rather than simply crashing into the Moon. To be sure, shipping 170 grams of lunar regolith to Siberia is an impressive achievement, but the scientific return of the late Luna missions was dwarfed by the hundreds of kilograms of carefully-picked rocks imported by astronauts during the Apollo program. Fortunately the Apollo haul has been quite a lot to work with, since there have been no trips to the lunar surface, even robotic ones, since the last of the Lunas.

With luck, that will soon change. Earlier today the China National Space Administration launched Chang'e 3, a solar-powered robotic rover toward Sinus Iridum. If successful, it will be the first time China's landed a spacecraft on another world, and the first time any nation has done so on the Moon in 37 years. It's about time.

Thursday, November 21, 2013


Due to concerns about the potential military applications of the American Space Shuttle program, the Soviet Union developed a reusable spaceplane during the 1970s and '80s with similar capabilities. The program was called Buran, Russian for "Snowstorm," and you can read more about it here:

At one time the Space Shuttle was intended to replace every expendable launch vehicle in the United States' rocket stable and perform every government satellite launch by the time it was up to its full launch cadence. To handle the traffic, three launch pads were prepared: two at the Kennedy Space Center in Florida to handle eastbound launches to geosynchronous orbit and other low-inclination orbits, and one at Vandenberg Air Force Base in California to handle southbound launches to polar orbit. Since polar orbits cover all of Earth's land area they're preferred for reconnaissance satellites, allowing them to snoop on adversaries, frenemies, and outright enemies wherever they might roam. What delighted the White House and concerned the Kremlin was that the Space Shuttle had the capability to retrieve spacecraft as well as deploy them. In theory, a Shuttle could launch from Vandenberg at just the right moment to snatch a Soviet spy satellite over Antarctica, then return to land in California after a single orbit. Presumably the American president would then claim to know nothing about why a Soviet spacecraft just disappeared without a trace.

Diplomatic absurdity aside, the Shuttle's large payload bay and high reentry maneuverability (required to enable single-orbit aborts after polar launches) made such missions technically feasible. Cold War logic being what it was, the Soviet military establishment eventually decided that if a NATO power was going to have such a capability, the USSR had to have it, too. The Soviet space design bureaus were then told to copy the Shuttle as best they could, and so Buran was born.

At the time it was built, and possibly to this day, the Space Shuttle was the most analyzed engineered system ever built by human hands. Its mission requirements called for a significant amount of aerodynamic maneuverability and good handling qualities across speeds ranging from about 200 miles an hour at landing to over 17,000 miles an hour at the start of reentry. To guarantee that the vehicle could perform as intended, thousands of hours of wind tunnel tests were conducted at subsonic, transonic, supersonic, and hypersonic speeds across a range of gas densities and temperatures to simulate the full-scale Shuttle's launch and entry environments. Knowing that the Americans had done this, and wanting to save money wherever possible amid the stagnating communist economies of the post-Brezhnev years, the Soviets elected to just duplicate the shape of the American Shuttle rather than repeat any of this work. Given the obvious brilliance of the Soviet human spaceflight heritage, this is a bit of a disappointment.

The most significant divergence between Buran and the Space Shuttle was its propulsion system. The American aerospace industry invested heavily in solid rocket motor technology during the Cold War to perfect its ballistic missiles, while the Soviets were mostly happy with the workings of liquid rocket engines. As a result, the American Space Shuttle leveraged big solid motor know-how by including two massive solid rocket boosters in the Space Shuttle's launch stack, while the Soviets used kerosene and oxygen-burning liquid boosters in their place. While liquid rocket engines tend to be more expensive than solids, this choice makes sense for a launch vehicle. Unlike ballistic missiles, launch vehicles don't need to be ready to fly at a moment's notice, so it's okay if it takes hours to fuel the vehicle before liftoff. Since liquids can launch more payload per pound of propellant and can be shut down benignly in the event of launch trouble (once lit, it's very difficult to stop solid rocket motor combustion), they're a more appropriate choice for a reusable launch vehicle. Since the hydrogen-powered main engines were mounted to the core propellant tank on the Buran stack, it had the flexibility to launch large payloads (like, say, space laser battlestations) as the semi-reusable launch vehicle Energia.

Soviet industry was strained to the breaking point by the catch-up defensive programs of the 1980s. By the end of the decade, the Communist Bloc was bankrupt and the west was declaring victory in the Cold War. Buran was one of the most expensive programs the USSR ever embarked upon, even with all the cost-cutting and corner-cutting measures in its development, and it surely played a significant role in the fall of the Soviet Union. In the end it only flew once, unmanned, before being mothballed and destroyed when the hangar housing Buran collapsed in 2002. But fly it did:

Monday, November 18, 2013

Aggie Bonfire

For almost a century, once a year students at Texas A&M University take it upon themselves to assemble a large stack of wood, douse it with jet fuel, and light it on fire. You can read more about that here:
Aggie Bonfire

Robert Gates, who at various points in his career served as Director of Central Intelligence, Secretary of Defense, and President of Texas A&M, once said of the university that "From the outside looking in, you can't understand it. From the inside looking out, you can't explain it." The former Agricultural and Mechanical College of Texas is an institution rich in tradition and ritual, and has a cult(ure) that must seem often baffling to outsiders. Among other things, upperclassmen can insist that those in newer classes do push-ups in exchange for saying certain privileged words, and are typically taken seriously while doing this (at least during football season). By comparison, the value of setting lots of stuff on fire is obvious.

For all of the 20th Century and the first decade of the 21st, A&M's  chief athletic nemesis was a certain university in Austin, and the tradition of Bonfire quickly became an annual rallying cry against the Longhorns. Few parts of the university's history better show the ferocious ambition of the Aggies than the almost Kurzweilian growth in the Bonfire stack's height in its first half-century. By 1969, while men from Earth walked upon the face of the Moon, the Bonfire reached a height of 109 feet, in what remains a record for bonfires anywhere. Surely history has shown the 1960s to be a decade ahead of its time. Cooler heads prevailed after that, and the university administration imposed clear limits on height and diameter out of concern for students' safety and the surrounding buildings' fire-suppression capabilities.

The administration's endorsement of Bonfire came to a painful, jarring halt in 1999 when the stack collapsed in the early-morning hours a week before its scheduled ignition. 12 students were killed and 27 injured when the joints holding the 5,000 logs together buckled and failed in what hopefully will remain the most traumatic single event in the university's history. An investigation revealed inadequate engineering of the structure, a lack of meaningful management accountability, and unsafe work practices to be contributing factors, and since then no Bonfire has burned on the A&M campus.

Four years after the tragedy of 1999 an independent Bonfire burned once again, this time far from campus proper, and under the supervision of professional structural engineering. A year after that a memorial was erected on the site of the collapse, and it's as much an introduction to that nebulous-but-meaningful Aggie Spirit that Gates was trying to talk about as it is a monument to the senselessness of what happened. The Aggies and Longhorns no longer play football each year, but Bonfire burns on, and the memories stay with us, and, hopefully, we learn from our mistakes.