A Teacher in Space

What a sad week. More than usual I've been thinking about, and grateful for, teachers. Looking for a distraction from the news out of Connecticut, I read about the role teachers have played in space exploration. So, if you're looking for a distraction too, that's what this post is about. 

Teachers in Space: Barbara Morgan and Christa McAuliffe.
Source: Wikipedia

Neil Armstrong returned home from the moon to teach at the University of Cincinnati, and there are many other examples of college professor astronauts in the years since he walked on the moon. But, today's post explores the history of primary school teachers in space ... aside from their obvious, fundamental role: laying the foundation of math and science education necessary to become a rocket scientist or astronomer or an astronaut!

NASA announced its first Teacher in Space project in 1984, to build enthusiasm for space exploration, math, and science among U.S. students. Over 11,400(!) teachers applied to be picked as citizen astronauts in NASA's Teacher in Space program, and two women were chosen. Christa McAuliffe, who launched and died aboard Challenger's last mission, and her backup, Barbara Morgan.

The NASA Teacher in Space Project Logo
Source: Wikipedia.

In pretty much every single photo of Christa McAuliffe I came across while researching this post, she's got a huge grin on her face. It's obvious how excited she was to be picked for the Challenger mission. Christa was a high school history teacher when she was selected in 1985. It's interesting that she wasn't a math or science teacher, isn't it? It sounds like she was picked based on her character more than her background. According to NASA administrators and her former students, Christa's enthusiasm for learning rubbed off on everyone she encountered.

Barbara and Christa, aboard a KC-135
Source: NASA.

As a history teacher, Christa had a unique view of space exploration: "I think just opening up the door, having this ordinary person fly, says a lot for the future ... you can always equate astronauts with explorers who were subsidized. Now you are getting someone going just to observe. And then you'll have the settlers, the space station is not too far down the road."

Christa with her son and daughter, July 1985.
Source: MSNBC.

As the first private citizen in space, Christa planned to document her trip aboard Challenger with daily journal entries, so that "like a woman on the Conestoga wagon pioneering west, I too would be able to bring back my thoughts and my journal to make that a part of history." And, if she had lived to make it into orbit, the plan was for Christa to teach classes of school kids live via TV from outer space. 

Christa McAuliffe in an astronaut jet trainer.
Source: NASA.

Christa believed that her space flight would be safe. She told a reporter in 1985 that the "space shuttle isn't the type of thing, I think, that anybody really looks at with fear that there's going to be an accident ... I feel, probably, safer doing something like that than driving around the New York streets." Christa's life insurance company had some doubts, though. It cancelled her policy after she was selected to fly. She was only insured when she died because a private aerospace company donated a $1 million dollar policy before her flight.

Others at NASA shared Christa's belief that space travel had become routine and safe. History of course tells a different story: that sense of complacency, along with bureaucratic bungling and a bad decision to launch, killed all seven Challenger astronauts on January 28, 1986.

Christa McAuliffe training for microgravity in a KC-135.
Source: readplatform.com.

What became of the other NASA Teacher in Space participant, Barbara Morgan? Barbara left NASA a few months after Christa died, returning home to teach second and third grade in Idaho. But, she was not done with outer space! Over a decade after the Challenger tragedy, Barbara was selected to serve as a NASA Mission Specialist. She began training for a space mission, just like any other astronaut candidate. For several years, she served as CAPCOM, communicating with space crews from Mission Control in Houston. 

Barbara flew in space once, on a mission to the International Space Station in 2007. Her primary tasks were operating the shuttle's robotic arm, and overseeing the transfer of supplies between the shuttle and the ISS. In orbit, she also took questions from students in Idaho and at the Challenger Center for Space Science Education.

Barbara Morgan, a teacher in space.
Source: Collect Space.

The Teacher in Space program was cancelled a few years after Christa died, but other primary school teachers have flown as educators in space in the years since, as part of subsequent NASA Educator in Space initiatives. These include Dorothy Metcalf-Lindenburger, who was a Washington science teacher when she was selected as an astronaut candidate in 2004. In 2010, she became the first Space Camp alumna to fly in space. :-) Other teacher astronauts include Richard Arnold, a high school science teacher who flew to the International Space Station in 2009, and Joe Acaba, the first Puerto Rican astronaut and the first middle school teacher in space. He has flown several missions to the ISS, including one this year.

One of Joe Acaba's mission photographs (Expedition 31).
Source: Wikipedia.

So in a way, Christa was right after all. She was a pioneer. Others followed after her, and they traveled to a space station. It just didn't work out quite the way I wish it had. 

Christa McAuliffe and Barbara Morgan watch the Space Shuttle Challenger launch in October 1985.
Source: NASA.

So, that's the story of the first American teachers in space. Writing it was a nice break from the sad reality I've been thinking about all weekend. And speaking of Sandy Hook Elementary, if you're looking for a way to help out, here are a few ideas:

• United Way has set up a fund for victims' families. 
• As always, the Red Cross is helping out in Newtown.
• If you support restoring the assault rifle ban and limiting access to guns by mentally ill folks, you can support the Coalition to Stop Gun Violence.
• And, there's the Brady Campaign to Prevent Gun Violence named for former assistant to President Reagan James Brady.

Sources: NASA; New York Times; Los Angeles Times; Washington Post; Wikipedia; Educationworld.com; Christa McAuliffe: Reach for the Stars.

A Moonwalker Invents a Mars Cycler

Before he traveled to the moon, Dr. Buzz Aldrin completed a PhD thesis exploring how to dock spaceships in the event of instrument failure. Since returning from the moon, Dr. Aldrin has been working to get humans to Mars...

Our future?
Source: NASA.

There are many, many, many obstacles to establishing a human colony on Mars. One huge challenge is the cost of ferrying people and the supplies they'll need between the two planets. Another challenge is the length of the trip to Mars. It took four days for Dr. Aldrin to travel from the Earth to the moon; it took the Curiosity Rover nine months to travel from the Earth to Mars.

Mars Science Laboratory, on its way to the red planet.
Source: Wikipedia.

Dr. Aldrin's "Mars cycler" plan comes in handy in addressing both of these challenges. Dr. Aldrin formulated this plan in the mid-1980s. He called for the establishment of a permanent human base on Mars, supplied by a fleet of of uniquely tasked spaceships. Some of these spacecraft would be used to ferry people and supplies between the surface of Earth and Earth orbit; some would transport people and supplies between the surface of Mars and Mars orbit. Meanwhile, traveling between Mars and Earth there would be a continuous cycle of interplanetary spacecraft: "cyclers."

These cyclers would essentially be space stations orbiting a path that would take them between Earth and Mars every few months. They'd be similar to the international space station, but with heavy-duty rockets attached, more radiation shielding, and maybe a big centrifuge creating artificial gravity. You could have two of these cyclers, with one always going towards Earth and one away. Or you could launch even more cyclers, allowing for more frequent trips between the two planets.

A Mars cycler approaches Mars.
Source: Scientific American, March 2000.

One upside to the cycler is that it makes a faster trip to Mars than traditional spaceships. In contrast to Curiosity's nine month trip to Mars, the cyclers could make the same trip in just five months. Cyclers are faster because they take advantage of a gravity assist. Meaning, they are aimed for a close encounter with Earth and then Mars, hurtling around each planet before shooting out back towards the direction they came from, picking up a bit of the planet's momentum as they go. Gravity assisted spacecraft (like the Voyager spacecraft) can build up much higher speeds than just firing a rocket.

Voyager 1 gained the momentum needed to escape the Sun's gravity via a gravity assist from Jupiter and Saturn.
Source: Wikipedia

The cyclers have other advantages. You don't have to pay for the fuel to repeatedly accelerate or decelerate the spacecraft when they reach Earth or at Mars, and you aren't constantly building giant spaceships capable of leaving Earth's atmosphere and landing on Mars. In these multi-stage spacecraft, almost every stage gets discarded after accelerating and decelerating between Earth and Mars.

The little bitty command module, that I've circled in red, is the only bit of Apollo 11 that made it home to Earth.
Source: Universe Today.

Are there downsides to the Mars cycler? Yes... maintaining the Mars-Earth orbit requires more than just the occasional course correction boost that the International Space Station gets to maintain its Earth orbit. As Dr. Aldrin acknowledges, "moderately large" maneuvers are required at irregular intervals to keep cyclers from smashing into a planet or zipping out of orbit into empty space. But, that said, the cycler is still essentially an orbiting space station: it is not having to expend massive amount of propellant to escape Earth or Mars gravity every time it flies to those planets.

Another problem is actually reaching the cycler from vehicles launching from Earth or Mars. The launch craft must catch up as the cyclers make their once-every-five-months pass by the Earth or Mars. The cycler could be travelling as fast as 27,000 miles per hour as it encounters Mars. That's close to the fastest speeds that the Apollo spacecraft ever traveled. So, a rocket leaving Mars attempting to rendezvous with the cycler would expend a great deal of energy. Or, alternatively, you could significantly slow down the cycler when it reaches Mars (by aerobraking- dipping into and out of the Martian atmosphere, with the friction of Martian air slowing the craft down). Then, it would be easy for a spaceship leaving Mars to rendezvous with the slowed cycler... though the cycler would need a big rocket boost to speed up and travel back to Earth.

An illustration of Mars Reconnaissance Orbiter aerobraking on arrival to Mars.
Source: Wikipedia.

Will humans ever hitch a trip to Mars on a cycling interplanetary space station? Nearly thirty years after he first proposed it, Dr. Aldrin's cycler idea still seems like a doable approach to establishing a long-term human presence on Mars. So, whether Mars Cyclers come to pass probably depends on our dedication to exploring the solar system.

Sources: Next Big Future; March 2000 Scientific American; buzzaldrin.com; NASA; D.V. Burnes, J.M. Longuski; B. Aldrin, Cycler Orbit Between Earth and Mars, Journal of Spacecraft and Rockets (1993); Buzz Aldrin et al.; Evolutionary Space Transportation Plan for Mars Cycling Concepts.

Dr. Buzz Aldrin and the Orbital Paradox

"In the hopes that this work may in some way contribute to their exploration of space, this is dedicated to the crew members of this country's present and future manned space programs. If only I could join them in their exciting endeavors!"

--  Edwin "Buzz" Aldrin's  Thesis Dedication, January 1963

Dr. Buzz Aldrin, after his stroll on the moon.
Source: Wikipedia.

Dr. Buzz Aldrin goes down in history as the second man to walk on the moon. He was also the first PhD in space. He submitted his thesis in January of 1963; he was selected as an astronaut in October of that year.* Dr. Aldrin's dramatic and sometimes troubled life story (Dancing with the Stars, three divorces, alcoholism, etc...) sometimes seems to overshadow his scientific accomplishments. But, before walking on the moon, he was the first person on Earth to earn a doctorate in the field of astronautics. MIT actually created its astronautics program specifically for him!

*: Astronaut Jim McDivitt was awarded an honorary doctorate before he flew on Apollo 9, but Aldrin was the first astronaut hired with a ScD (equivalent to a PhD) degree.

The view from Apollo 11, leaving Earth orbit for the moon.
Source: Wikipedia.

Astronautics is the study of space navigation. Dr. Aldrin's research focused on the process of docking two orbiting spacecraft. When Dr. Aldrin was completing his coursework, humans hadn't yet docked two spacecraft in orbit. The first docking occurred on Gemini 8, in 1966. Soon thereafter, Dr. Aldrin flew aboard  Gemini 12 and was able to follow up on his doctoral work with hands-on experience.

Dr. Aldrin in his pre-PhD days.
Source: Time.

Dr. Aldrin's thesis was titled Line-of-Sight Guidance Techniques for Manned Orbital Rendezvous. It's available for download here. His doctoral work was the development a procedure for visually docking (as in, using your eyes to guide the spacecraft). That way, astronauts would be able to supplement computer models, navigational chart data, or radar data with their own visual observations. Being able to rely on a visual docking technique in addition to following computer and instrument guidance means that docking is possible even if those sources of data partially failed.

So, for example, when the rendezvous radar failed during Dr. Aldrin's Gemini 12 mission, he and  Jim Lovell docked their spacecraft to the target vehicle using the onboard computer, navigational charts, and their own observations out the spaceship windows. Such was the success of Dr. Aldrin's visual docking techniques that parts of the dissertation became standard operating procedure for NASA.

The view from the Apollo 11 Command Module: the Lunar Module approaches.
Source: NASA.

Docking spacecraft in orbit poses serious challenges not encountered when docking a boat or connecting two aircraft for a refueling maneuver  Like air travel, space travel works in three dimensions. But unlike air travel, there's the added challenge of working with craft that are in orbit. There's also the confusion created by freefalling around Earth without a feeling of "up" or "down." And, there's what Dr. Aldrin terms an "orbital paradox."

Here's the paradox: If you're trying to pilot your orbiting spaceship to reach a spaceship in a higher orbit, the intuitive course is to (1) aim your spacecraft up, towards the higher orbit, and (2) speed up your spacecraft so it will catch up. Dr. Aldrin describes the surprising result of this maneuver. You'll "end up in an even higher orbit, traveling at a slower speed and watching the second craft fly off into the distance."

Gemini 12 and an Agena Rocket, 15 feet apart.
Source: Wikipedia.

Or, as Neal Stephenson describes it in his novel Anathem: "Things in orbit didn't behave like we were used to. Just to name one example: if I were pursing another object in the same orbit, my natural instinct would be to fire a thruster that would kick me forward. But that would move me into a higher orbit, so the thing I was chasing would soon drop below me. Everything we knew down here was going to be wrong up there."I won't tell you why the main character in Anathem was headed into space, just in case you want to read the book.... it's a great adventure story!

Apollo 9's command and service modules, docked.
Source: NASA.

Aside from PhD dissertations and science fiction, the practical result of the orbital paradox is as follows. When the International Space Station docks with a Soyuz, the Soyuz and the ISS begin their final docking maneuvers at the same altitude and velocity as each other, but with the Soyuz out in front of the ISS. Then the Soyuz will fire its rocket and move towards a slightly higher orbit, because this slows the craft down! Next, the Soyuz will slowly drop back to the lower orbit, moving faster and closer to the ISS the lower it gets. Finally, the spacecraft will back into the ISS, docking with the front of the space station.

Here's a diagram the boyfriend and I drew to explain how the Soyuz moves to that initial, higher orbit:

See how the Soyuz fires its rockets so that, if it wasn't in orbit, it would move directly away from the ISS?
But since both craft are in orbit, the effect of thrust in that direction is to move the Soyuz to a higher, slower orbit.
Then, it can drop back down towards the ISS.

Teaching folks how to achieve orbital docking by sight is not Dr. Aldrin's only academic contribution to space exploration. There's also Dr. Aldrin's novel idea for exploring Mars, called the Mars Cycler. More on that, coming soon!

Sources: Scientific American; buzzaldrin.com; Neal Stephenson's Anathem; Wikipedia.

The Story of a Noble Gas

Last week 's blog post explored the golden age of airships, and how nowadays they're used to explore outer space. As I mentioned last week, one of the few airship operators in the U.S. is going out of business because helium prices increased tenfold(!) in the past few years.

The Long Endurance Multi-Intelligence Vehicle: a U.S. military hybrid airship.
Source: Wikipedia.

Helium is the second most abundant element in the universe- why is it getting more expensive? The answer to that question can be traced back to the heyday of airships, the 1920s and 1930s. Back then, it looked likely that the wars of the future would be fought by dirigibles. So in 1925 the U.S. government began maintaining a massive stockpile of the helium gas necessary to float these airships. Ever since then, the U.S. government has been siphoning off helium from natural gas extracted beneath Texas, Kansas, and Oklahoma. The helium is stored in the National Helium Reserve just north of Amarillo, Texas.

The Federal Helium Reserve.
Source: Wall Street Journal

Since helium was essentially a war material, the U.S. banned exports of the gas to the Nazi government in the late 1930s. This meant that the Germans used hydrogen to float the Hindenburg Airship; a risky move, since hydrogen is highly flammable, while helium is inert. Infamously, the Hindenburg caught fire and exploded in the spring of 1937. And its destruction was just one in a series of hydrogen airship accidents throughout that decade.

May 6, 1937: the Hindenburg disaster.
Source: Wikipedia.

Within two years of the Hindenburg disaster, Pan Am began transatlantic passenger flights. Thus ended the demand for transatlantic airship passenger service and mail delivery via airships.  The age of airships was over. Demand for helium plummeted.

Sources of helium in the U.S.
Source: National Academies Press.

With fewer airships around to fill with helium, the Reserve became a costly government expenditure, subsidizing artificially low helium prices. By 1996 it was $1.4 billion in debt. So, that year the Helium Privatization Act was signed, requiring the Reserve to sell off all its gas and close by 2014.

The U.S. government's practice of selling helium at cut-rate prices effectively kept any other potential helium producers out of the market. The Reserve was a massive player in the helium market, accounting for a whopping 30% of the world's helium supply. Naturally, its impending closure has destabilized the world helium market. New helium producing plants in Russia, Qatar, Algeria, and Wyoming are coming online, but replacing 30% of the world's helium supply doesn't happen overnight. Hence the price increases.

The rise in helium prices, 1999-2011.
Source: Washington Post.

So that's the short-term challenge. But there's a long-term helium shortage too. The Earth is running out of helium! How can that be, since it's the second most common element in the universe? Well... it's also the second lightest weight element. Helium doesn't like to bond with other elements to make heavier molecules. Helium atoms generally stay by themselves, and are so lightweight that they eventually float away from Earth, into space. You can produce helium in a lab, but there's no cost-effective way to do that on a large scale right now. Pretty much the only helium you find occurring naturally on Earth is produced inside the Earth by natural radioactive decay.

One use for the world's precious helium supply.
Source: helpmeplanit.com.

A fraction of the helium produced by natural radioactive sources is trapped below the Earth's surface in natural gas deposits. That's why the Federal Helium Reserve is located next to natural gas deposits: we extract helium from natural gas.

With Airship Ventures closing, who needs helium?  NASA has historically been the world's top industrial helium user. Helium was used to pressurize and purge rocket engines. It's used for many other practical purposes, like cooling the magnets used in MRI machines and particle accelerators.

Helium: It's better than spinach.
Source: Time.

Our supply of natural helium will run out when our supply of natural gas runs out. Given that it's not a renewable resource, some scientists have advocated for creating an international body to regulate the supply and pricing of helium. Some folks argue that the price of helium should be set even higher than it has risen, to eliminate waste (see Popeye, above, for what might be considered a waste).

Helium in action.
Source: NASA.

The short term outlook for helium prices is uncertain. This past spring, a Democratic Senator from New Mexico and a Republican Senator from Wyoming co-sponsored a bill that would stabilize the price of helium by pacing the sell-off of the Reserve's supply. But, as of this week, that bill hasn't moved out of Committee. Assuming it isn't brought to a vote in December, it'll have to be reintroduced when the new legislative session begins in 2013.

A future use for helium: pressurizing and purging the engines of the Ares 1.
Source: NASA.

Sources: NPR; American Institute of Physics; U.S. Department of the Interior; Elko Daily; Time; Wall Street Journal; Washington Post; Wikipedia.

Zeppelins: A Stairway to the Heavens?

Before the space age, there was the airship age. Dirigibles were so popular in the early 20th century that a mooring for airships was fitted to the top of the Empire State Building upon its completion in 1931!

A dirigible docked to the Empire State Building.
Source: ephemeralnewyork.

But, the mooring was only used once, and only for a couple minutes. It turns out that docking a giant blimp to a building over 1,000 feet tall is nearly impossible; the winds at that height are too strong. Soon after that first brief docking attempt, a Goodyear blimp also tried and failed to dock at the Empire State Building mooring. Its crew did manage to lower a stack of the evening newspapers down a 100 foot long line to the building roof, though! It seems the Empire State Building's airship docking port wasn't considered practical even when it was built. Its construction and attempts to use it were pretty much just a publicity stunt.

A Goodyear blimp flying over the Empire State Building.
Source: New York Times.

The failed attempt to turn the Empire State Building into a dirigible port foreshadowed the end of the airship era. The 1930s saw a rise in airship accidents (e.g., the Hindenburg disaster). Soon, airplanes overtook airships as much faster, more reliable, and safer. Since the 1930s, there's been very little need for airships as a means to transport people or objects. The few airships left in operation now satisfy a small niche market: they're an efficient way to float in place or cruise very, very slowly through the sky... and that's about all.

The view out the back of Airship Ventures' Blimp.
Source: Airship Ventures.

The evening I started writing this post on airships I found out that one of the U.S.'s few (maybe only?) private dirigible operators, Mountain View based Airship Ventures, is likely closing. CEO Brian Hall cited the tenfold increase in helium prices since the company's founding in 2007 as one of the challenges the company faced.

Airship Ventures' Eureka launches.
Source: Wikipedia.

I think airships are so neat; I'm sad to see Airship Ventures struggle to make it, much in the same way that commercial passenger space travel struggles to become a viable industry. And speaking of space travel... did you know that airships are actually useful tools for space exploration?

Pilot Katherine Board flies Airship Ventures' Eureka.
The only two female Zeppelin pilots in the world flew for Airship Ventures!
Source: Airship Ventures.

An airship is the perfect vehicle to test a starshade. What's a starshade? It's a large disk that blocks the light from a distant star, allowing for observation of that star's exoplanets. Folks have contemplated launching a starshade to sit 80,000 miles in front of the James Webb space telescope, which will hopefully launch in 2018. An airship-mounted starshade could be tested before 2018. According to a Wired article from this past February, Airship Ventures' Eureka was going to fly a starshade in Spring 2013, to block star light for Earth-based exoplanet observations. With Airship Ventures closing, I guess that won't happen now. :-(

The Airship Eureka.
Source: Wired.

Even if the Airship Eureka doesn't fly again, it will have done its part to contribute to space exploration: it has hunted for meteorites! In April of this year, a minivan-sized meteorite exploded over northern California. Researchers were especially eager to collect fragments of the meteorite, since the asteroid it came from was of a relatively rare variety, the carbonaceous chrondite. This type of rock is full of the organic molecules that serve as the building blocks for life on Earth (and elsewhere?).

NASA and SETI paid to take Eureka out on a five-hour mission to search for bits of the exploded rock. The airship cruised slowly over the Sierra Nevada foothills, and the scientists on board looked for little impact craters, finding a dozen possible sites.

April 22, 2012 a fragment of a meteorite over Nevada.
Source: Space.com.

Circling back to CEO's explanation for why Airship Ventures is going out of business: helium prices have increased tenfold in the past five years. Why is helium getting so expensive? It's a fascinating question, actually. I'll talk about it in my next post.

*** Addendum: part two of this post, The Story of a Noble Gas, is posted here!

Sources: Wired; Airship Ventures; Zimbio; SFGate; Wikipedia; Dvice.com; Space.com.

A personal history of the space race

Happy Veteran's Day! One of my favorite vets is my father's father. Born in 1917, Grandfather served in World War II as a paratrooper with the 82nd Airborne. On June 6th, 1944, he jumped into Normandy, carrying his unit's radio on his back. He made it through D-Day unharmed, but on June 7th he stepped on a land mine. He survived, but lost a leg.

In the army, circa 1944.

Before World War II, Grandfather was studying accounting at a college near his hometown. His wartime job as a radioman sparked an interest in engineering. So, upon returning from Europe, he began a career as an engineer. He worked at Western Electric, and also briefly at Bell Labs. Eventually, at age 48, he graduated from college.

Graduation, 1966.

Counting government employees and the employees of private contractors, over 400,000 Americans worked to land 12 Apollo astronauts on the moon. My grandfather spent his career perfecting guidance systems for rockets, but technically he wasn't a part of that 400,000. His focus was primarily Nike Hercules and Nike Zeus rockets, not the rockets that took men to the moon. 

Posing at White Sands with a Nike Hercules rocket.

Nike Hercules missiles were developed to fire at airborne targets (specifically, bombers) or at targets on Earth. Some of them could be tipped with a nuclear warhead. They were first deployed in 1958, and they were all deactivated by 1979, as the military's concern turned from incoming bombers to incoming missiles.

The launch of a Nike Zeus.
Source: Wikipedia.

Nike Zeus rockets were defensive weapons, developed to intercept and destroy intercontinental ballistic missiles. Their first successful launch was in 1959; their first successful intercept was in 1962. They were phased out after the SALT I treaty was signed in 1972. The last Nike Zeus was decommissioned in 1974. Both Hercules and Zeus were replaced with the much more accurate and more mobile Patriot missile systems.

Posing with another rocket. This doesn't look like any of the Nikes I'm finding online though...

I can hardly believe how quickly the race to the moon proceeded. It can be measured in terms of one person's career: Grandfather went to work just when the U.S.'s rocket program took off. He retired right after Apollo-Soyuz. While not working directly on the Apollo program, he was fascinated by it. Like many Americans, he followed the space program with great interest. My Dad still has the newspaper clippings Grandfather saved from each NASA launch.

White Sands Missile Range, in the late 1950s.

Folks talk about the Apollo program (and Bell Labs, where my Grandfather briefly worked) as being the golden age of American invention. I've heard people say that we no longer solve problems on the same scale as my Grandfather's generation.

I just started reading this book and I highly recommend it!
Source: Boston.com.

Grandfather died before I was born, so I don't know his thoughts on the subject. My belief is that the problems we're tackling now are more complicated and thus require far more money and time to solve. The greatest generation took us to the moon, but getting people to Mars or beyond is even harder. I think we will get there, though... eventually.

Speaking of which, have you seen this news?

Sources: my dad (thanks!); Wikipedia; Space.com; Boston.com.

The Deep Space Network, Part II

Two weeks ago I asked the question: how do we communicate with spacecraft operating around our solar system and beyond? The short answer is that we listen and talk to these probes via a network of giant (up to 230 feet in diameter!) radio telescopes.

The Green Bank radio telescope in wild, wonderful West Virginia.
Source: National Radio Astronomy Observatory.

Even knowing that we have dozens of large dish antennae able to work together to receive and transmit data, it is still amazing to me that we can communicate with, for example, Voyager 1. That little spacecraft is 17 LIGHT HOURS away from Earth! How do you receive a signal sent by a small transmitter hundreds of millions of miles away?

At this point, there are only two ways to communicate with the Voyagers. Our largest antennae, the 230 foot diameter dishes, are powerful enough to talk to the craft. Or, multiple dishes arrayed together can communicate with the Voyagers. Arraying dishes means aligning individual dishes so that they work together,  functioning as an even more powerful device, able to separate the weakest signals from background interference. You can array two dishes at the same Deep Space Network location. You can also array dishes at different locations. For example, dishes at the Very Large Array facility in New Mexico can work together with the dishes at Goldstone, receiving signals that would be too weak for one dish or one facility alone to discern.

Jodie Foster, putting the Very Large Array to good use.
Source: on-walkabout.com.

According to the Deep Space Network's operations manager, Jim Hodder, recent innovations made to the Network have further improved our ability to talk to the Voyagers. For example, we can now cool a dish antenna's receivers down to near absolute zero (-460 degrees Fahrenheit). This reduces interference with Voyager's radio signal, because any heat above absolute zero knocks electrons out of their lowest energy state orbits, just like radio waves from a spacecraft knock electrons out of their lowest energy state orbits. Less heat means less extraneous movement by electrons. Therefore, it's easier to pick out the one distant radio signal you're looking for.

Voyager 1, back when it was 17 light hours closer to Earth.
Source: Wikipedia.

When the Voyagers were launched in the late 1970s, we would likely not have been able to communicate with a spacecraft 17 light hours away. But now, it appears that the Voyagers will run out of the power needed to transmit messages before they leave the range of our radio telescopes!

A Voyager at the edge of the solar system.
Source: Space.com.

There's one other neat fact I've learned about communicating with spacecraft around the solar system. As I mentioned back in my first Deep Space Network post, there are three human-made satellites (Mars Odyssey, Mars Reconnaissance Orbiter, and Mars Express) orbiting Mars right now. As a result of this infrastructure in Mars orbit, our communications with the Curiosity rover are a bit more advanced than for the average interplanetary mission.

The base of Mount Sharp, as viewed by Curiosity.
Source: NASA.

In total, Curiosity has three methods of communicating with its human friends:

One, Curiosity can transmit signals directly to the Deep Space Network through a low-gain antenna. This antenna sends and receives data a slower rate in every direction, so that Curiosity doesn't have to point its antenna directly at Earth. Curiosity uses this antenna to transmit information, and, more often, to receive information.

Two, Curiosity also has a high-gain antenna that it can point at Earth to broadcast information directly there. This can send data at a faster rate than the low-gain antenna. Curiosity uses this antenna most often when it is receiving instructions from scientists on Earth.

Three, Curiosity usually communicates with Earth indirectly, via our Martian satellites! It can send and receive information to and from the Mars Reconnaissance Orbiter, Mars Global Surveyor, or Mars Odyssey via a UHF (short-range) antenna.

The deck of Curiosity, with the low-gain and high-gain antennae visable.
Source: JPL.

This third method of communication is particularly useful. Curiosity expends less energy to broadcast to our Martian satellites than to Earth, since the satellites are less than 300 miles away when passing overhead of the rover. But more importantly, the satellites enable communication with the rover much more often. Mars, like Earth, rotates approximately every 24 hours, and thus half the time the rover does not have a direct line of sight to Earth. So for about 12 hours out of every Martian day, Curiosity cannot use its high or low gain antennae to transmit data directly to Earth. But instead of only having access to Curiosity for only half of every day, thanks to the the three Martian satellites, JPL can contact the rover for about 16 hours out of any given day!

An avalanche on Mars, as seen from the Mars Reconnaissance Orbiter.
Source: Wikipedia.

As a result of these three methods for accessing the Deep Space Network, we can communicate with Curiosity across tens of millions of miles of outer space at up to half the speed of a typical modem in someone's house! 

Sources: io9, JPL, Wikipedia; Space Today; NASA; Popular Mechanics.