Category Archives: NASA

Eclipse Postscript

In a previous blog in June , I described the August 21, 2017 eclipse and what to expect from it, along with the many resources available at the NASA website that fill-in the details of this event as we were expecting it to unfold.  This website, by the way,  went crazy for the eclipse and got over 2 billion hits from tens of millions of daily visitors. For myself, I was not prepared for the surge of emotions I would feel even after glimpsing only 15 seconds of this event between gaps in the clouds over Carbondale, Illinois. Why Carbondale? I described in a 2014 Huffington Post article how this would be the place where the eclipse lasted the longest, 2 minutes and 40 seconds, and so this is where NASA Edge decided to park us for our major public outreach activities and NASA TV interviews.

I had been interviewed by a number of TV and radio reporters as well as a memorable Facebook interview with Curiosity. My article at NASA on the airline flights that would see the eclipse got quite a bit of traction. It was fun to see my articles on smartphone eclipse photography get so much press like this one at BuzzFeed, or this one at WIRED.  I even presented my smartphone tips to 1000 students at a local high school, which was carried by the local TV station WSIL-TV. Amazingly, despite my public ‘expertise’ on the matter, I did not bother using my smartphone at all in the brief time that the eclipse showed itself!

I mentioned in an interview with Carolyn Cerda also on WSIL-TV how I had brought along my cameras and hoped to grab just one image of this event. This was after many weeks of debating with myself whether I should even bother with photography at all. I knew how easy it was to get lost among the f/stops and exposure speeds in pursuit of a trophy to commemorate this event. I certainly didn’t want to waste precious time wrestling with the very finicky smartphone telephoto lens set up. But I also wanted to spend as much time as possible letting the emotions wash over me, just as they had done for millions of other people down through the thousands of years of human history. Could I, too, experience the fear that had so commonly been the popular experience? Or would my science protect me from these irrational feelings like some coat-of-armor? I had no idea, and in many of my TV interviews I said as much.

So I compromised.

I would run my digital, Sony camcorder during totality, and on the same tripod bracket, I would set my Nikon D3000 to a fixed f/stop and exposure speed selected to highlight the dazzling bright inner corona and any prominences or blood-red chromospheric light that may be present. I would hold the shutter release down so that the camera took bursts of a dozen photos, and periodically snap photos at mid-eclipse, and on each side of the 2.5-minute window to catch Baily’s Beads and anything else going on. It sounded like a good plan, and one in which I could still spend all of my eyeball time looking at totality and not at my camera!

This turned out to be a very good choice!

The clouds did roll in and cover the entire eclipse except for the last 15 seconds of totality. I snapped a few pictures like the one above using the clouds themselves to filter the intense sunlight, revealing a diminishing crescent sun. Had my NASA activities allowed us to be located a mile east rather than by Saluki Stadium at the Southern Illinois University, Carbondale campus, I would have been treated to a full 2.5 minutes of eclipse. But 15 seconds was just enough time to send chills down my spine and have the experience of a lifetime.

My photos turned out not to be too bad. The montage below was posted on my Facebook page within an hour or so, and although a bit fuzzy for the clouds, it was clear I had seen the entire circumferential inner corona, several red spots along the solar limb as the chromosphere peaked through, and the delightful Diamond Ring of sunlight streaking through a deep lunar canyon! My camcorder also showed the emergence of the sun from totality, capturing the dense clouds and the screams from the thousands of people looking on. This also went up on my Facebook page to the delight of dozens of my friends and family!

But how did I feel?

It was frustrating to see the crescent sun dip in to the dense clouds at the start of totality, and to watch the clock tick out the next few minutes, but as we reached mid-eclipse the scenery around me turned to twilight so quickly that I actually gasped in amazement! Hopefully, and with cameras at the ready I waited and then suddenly the brightening of a small portion of the cloud heralded that the eclipsed sun was about to make its appearance. When it did, everyone shouted and I watched with amazement, not really understanding what it was I was seeing. I immediately placed my finger on the shutter button, let the camera’s machinery take a series of 100 images, and hoped for the best. Again I was not dissappointed.

A dark object appeared surrounded by an intense ring of light. I thought this was just the reflection of sunlight on the cloud, but in an instant I realized this was no sun glint for there was no brilliant solar disk to illuminate it. Instead, it was the corona itself, brighter to the naked eye than I ever could have imagined! Within a few seconds the moon began to move off the western edge of the solar disk and slowly but steadily a single bright point of light appeared and grew in brightness until I could no longer stare at it with my eye through the digital display of my camcorder.

There was so much noise and ruckus from everyone else cheering that it was hard for me to collect and reflect on my thoughts – a process that took several days and repeated sharing of my experiences with family and friends. I had only experienced the ‘tip of an iceberg’ in the emotions that had hit me, and some were no doubt muted by the confusion of what I was seeing so briefly. I could only imagine what the full two minutes would have brought to mind.

I was not prepared for the days to follow. My sense of loss was something ineffable that I could not quite shake. I drifted from day to day, occasionally gawking at the many gorgeous online photos taken by more savvy photographers and old-hands at totalities. But you have to start somewhere, and at least for the first time in my life as an astronomer I can describe to my students,not only why we have eclipses and how our ancestors regarded them, but as with the Northern Lights, I can now add my own tiny voice to describing them in purely human terms!

Eclipse!!!

In nine weeks, on August 17, 2017, residents of the continental United States will be treated to a total solar eclipse as they enjoy their noon-time repast. If you are standing along the line of totality, which stretches from Oregon’s Pacific coast to South Carolina’s Atlantic surf, and if you have a good telescope, you may even be treated to a view such as the one below photographed by Luc Viatour ( www.Lucnix.be) during the August 1999 total solar eclipse over France!

In this blog, I am going to mention some of the work I am doing to help the public enjoy this once-in-a-lifetime event through my various projects at NASA. NASA, as part of its informal education programs, has adopted this event as a major national PR effort to focus its many assets on the ground and in space. In early-2016, my group at the NASA Goddard Spaceflight Center called the Heliophysics Education Consortium (HEC) was asked to lead the charge organize this event. Led by Dr. Alex Young, the HEC team has created the Official Eclipse website, and I have had the great pleasure and honor to have written many of its resources. So, think of this Blog as an introduction to the What, Where, When and How of this eclipse, and a personal tour by me for how you can enjoy this rare and magnificent event!

First, you probably have a lot of questions about solar eclipses, so I wrote a FAQ Page that covers most of the common ones. I also wrote an essay about the many Eclipse Misconceptions that people have had about solar eclipses. Some are quite bizarre, but seem to be passed on from generation to generation despite our deep scientific understanding of them!

Take a look at the picture at the top of this blog. During most total eclipses of the sun, you are guaranteed to see the brilliant solar corona. With a telescope or a good telephoto lens, you may even glimpse the reddish hue of the solar chromosphere following along the darkened limb of the moon. Here and there, you may even see a solar prominence also glowing in reddish light. These features are hard to see because they are rather small and with the naked eye you just don’t have the natural magnification to see them well.

I will be writing a number of  essays that discuss particular aspects of the sun and post them at the Eclipse SCIENCE page. Topics will include the corona, prominences, chromosphere and the dramatic helmet streamers  so far as astronomers understand them today. It’s all about solar magnetism and how this interacts with the 100,000 degree plasma in the solar atmosphere. The corona, itself, has a temperature of several million degrees! It is about a million times fainter than the disk of the sun, which is why you only get to see it during an eclipse. But astronomers can use instruments called coronagraphs to artificially eclipse the sun, and allow us to study coronal features at our leisure.

There are many things you can do while waiting for the eclipse to start, and a few non-invasive things you can do while the eclipse is in progress. I have tried to collect these ideas into two areas called Citizen Explorers and Citizen Scientists depending on how serious you want to be in exploring eclipses. If you have a mathematical mind, I have even created a dozen or so curious Math Challenges that help you look at many different aspects of the event.

Just about everyone is going to want to use their smartphones to photograph the eclipse, so in my article on Smartphone Photography I try to outline some of the things you can do, what kinds of technology you need like inexpensive telephoto lenses, and what to expect. Below is a photo taken by a smartphone with no other technology from Longyearbyen, Svalbard in 2015. Your camera phone will give you a brilliant, over-exposed corona but don’t expect detailed resolution because your lens is simply not good enough to show details like those in the photo above. If you use an inexpensive smartphone telephoto with 15x or higher, you need a camera tripod too. Also, be careful that you do not use the telephoto on the sun while the brilliant photosphere is visible to avoid camera damage. (Credit: Stan Honda/AFP/Getty Images)

Some people may be interested in uploading their images, and in my essay on Geotagging I describe two ways that you can upload your selfies so that others can enjoy your efforts. The first is to use GOOGLE Maps but you can only upload your photo to  preexisting ‘tagged’ locations in GOOGLE Maps (nearby businesses, monuments, parks, etc). This is unlike the discontinued Panoramio/GOOGLE Earth feature where you could upload your picture to any geographic location on the planet. The second way is to send your pictures to a NASA site that is collecting them.

For a rare event like this, you might also want to create a time capsule of your experience. I have suggested that you write a letter to yourself about who you are today, and what you think the future holds for you. On April 8, 2024 there will be another total solar eclipse across the continental United States and you might set that date as the time when you next read your letter being at that time 7 years older!

People have observed total solar eclipses for centuries, and in my Eclipse History area I have a number of essays that describe earlier observations in the United States. There is even an archive of newspaper articles since the early 1800s in which you can read  first-hand accounts. Some music has also been written and performed with solar eclipses in mind! In my Music Page I list many of these pieces both in classical and pop music over the years. Who can forget Carly Simon’s ‘…You flew your Lear Jet to Nova Scotia to see the total eclipse of the sun’ about the March 7, 1970 eclipse!

One thing I find interesting is that since the 1500s there have been over a dozen eclipse paths that have crossed the one for August 21, 2017. I created several resources that describe these ‘magical’ crossing points and what history was going on in North America during these dates. I also created a set of math problems where you can calculate the latitude and longitude for these crossing points  if you are in-to math!

Where should you go to see this eclipse? In one essay I discussed how  there are dozens of airline flights on that day from which passengers may be able to see the total solar eclipse out their windows if the Captain gets you to the right place and time along the route. For folks on the ground, you can check out NASA’s Path of Totality maps and see if your travels on that day take you anywhere close. For the rest of us, no matter where you are in North America, you will at least see a partial solar eclipse where a small ‘bite’ is taken out of the solar disk. With a pair of welder’s goggles or solar viewing glasses, you can look up anytime around noon and see the eclipse in progress.

Created with GIMP

NASA plans to collect stunning images from some of its available spacecraft, so on this page I collected information about which spacecraft will participate. After the eclipse, you will see in the News Media many of these images as they are produced during the days after the event.

Myself, I will be joining the NASA Eclipse Team in Carbondale, Illinois for a huge public celebration of the total solar eclipse. This will be televised through numerous NASA feeds all along the path of the eclipse so you can view it on your smartphone or laptop screen wherever you are. I will be involved with this telecast between 11:45 and 1:45 CDT as a panelist on several of the program segments. When I return from this event, or perhaps even during it, I will upload a follow-up blog about what it was like from ‘Ground Zero’. I have never experienced a total solar eclipse before, so I am prepared to be stunned and amazed!

Stay tuned!

Martian Swamp Gas?

Thanks to more than a decade of robotic studies, the surface of Mars is becoming a place as familiar to some of us as similar garden spots on Earth such as the Atacama Desert in Chile, or Devon Island in Canada. But this rust-colored world still has some tricks up its sleave!

Back in 2003, NASA astronomer Michael Mumma and his team discovered traces of methane in the dilute atmosphere of Mars. The gas was localized to only a few geographic areas in the equatorial zone in the martian Northern Hemisphere, but this was enough to get astrobiologists excited about the prospects for sub-surface life. The amount being released in a seasonal pattern was about 20,000 tons during the local summer months.


The discovery using ground-based telescopes in 2003 was soon confirmed a year later by other astronomers and by the Mars Express Orbiter, but the amount is highly variable. Ten years later, the Curiosity rover also detected methane in the atmosphere from its location many hundreds of miles from the nearest ‘plume’ locations. It became clear that the hit-or-miss nature of these detections had to do with the source of the methane turning on and off over time, and it was not some steady seepage going on all the time. Why was this happening, and did it have anything to do with living systems?

On Earth, there are organisms that take water (H2O) and combine it with carbon dioxide in the air (CO2) to create methane (CH3) as a by-product, but there are also inorganic processes that create methane too. For instance, electrostatic discharges can ionize water and carbon dioxide and can produce trillions of methane molecules per discharge. There is plenty of atmospheric dust in the very dry Martian atmosphere, so this is not a bad explanation at all.

This diagram shows possible ways that methane might make it into Mars’ atmosphere (sources) and disappear from the atmosphere (sinks). (Credit: NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan)

Still, the search for conclusive evidence for methane production and removal is one of the high frontiers in Martian research these days. New mechanisms are being proposed every year that involve living or inorganic origins. There is even some speculation that the Curiosity rover’s chemical lab was responsible for the rover’s methane ‘discovery’. Time will tell if some or any of these ideas ultimately checks out. There seem to be far more geological ways to create a bit of methane compared to biotic mechanisms. This means the odds do not look so good that the fleeting traces of methane we do see are produced by living organisms.

What does remain very exciting is that Mars is a chemically active place that has more than inorganic molecules in play. In 2014, the Curiosity rover took samples of mudstone and tested them with its on-board spectrometer. The samples were rich in organic molecules that have chlorine atoms including chlorobenzene (C6H4Cl2) , dichloroethane (C2H4Cl2), dichloropropane (C3H6Cl2) and dichlorobutane (C4H8Cl2). Chlorobenzene is not a naturally occurring compound on Earth. It is used in the manufacturing process for pesticides, adhesives, paints and rubber. Dichloropropane is used as an industrial solvent to make paint strippers, varnishes and furniture finish removers, and is classified as a carcinogen. There is even some speculation that the abundant perchlorate molecules (ClO4) in the Martian soil, when heated inside the spectrometer with the mudstone samples, created these new organics.

Mars is a frustratingly interesting place to study because, emotionally, it holds out hope for ultimately finding something exciting that takes us nearer to the idea that life once flourished there, or may still be present below its inaccessible surface. But all we have access to for now is its surface geology and atmosphere. From this we seem to encounter traces of exotic chemistry and perhaps our own contaminants at a handful of parts-per-billion. At these levels, the boring chemistry of Mars comes alive in the statistical noise of our measurements, and our dreams of Martian life are temporarily re-ignited.

Meanwhile, we will not rest until we have given Mars a better shot at revealing traces of its biosphere either ancient or contemporary!

Check back here on Thursday, March 2 for the next essay!

The Next Sunspot Cycle

Forecasters are already starting to make predictions for what might be in store as our sun winds-down its current sunspot cycle (Number 24) in a few years. Are we in for a very intense cycle of solar activity, or the beginning of a century-long absence of sunspots and a rise in colder climates?

Figure showing the sunspot counts for the past few cycles. (Credit:www.solen.info)

Ever since Samuel Schwabe discovered the 11-year ebb and flow of sunspots on the sun in 1843, predicting when the next sunspot cycle will appear, and how strong it will be, has been a cottage industry among scientists and non-scientists alike. For solar physicists, the sunspot cycle is a major indicator of how the sun’s magnetic field is generated, and the evolution of various patterns of plasma circulation near the solar surface and interior. Getting these forecasts bang-on would be proof that we indeed have a ‘deep’ understanding of how the sun works that is a major step beyond just knowing it is a massive sphere of plasma heated by thermonuclear fusion in its core.

So how are we doing?

For over a century, scientists have scrutinized the shapes of dozens of individual sunspot cycles to glean features that could be used for predicting the circumstances of the next one. Basically, we know that 11-years is an average and some cycles are as short as 9 years or as long as 14. The number of sunspots during the peak year, called sunspot maximum, can vary from as few as 50 to as many as 260. The speed with which sunspot numbers rise to a maximum can be as long as 80 months for weaker sunspot cycles, and as short as 40 months for the stronger cycles. All of these features, and many other statistical rules-of-thumb, lead to predictive schemes of one kind or another, but they generally fail to produce accurate and detailed forecasts of the ‘next’ sunspot cycle.

Prior to the current sunspot cycle (Number 24), which spans the years 2008-2019, NASA astronomer Dean Pesnell collected 105 forecasts for Cycle 24 . For something as simple as how many sunspots would be present during the peak year, the predictions varied from as few as 40 to as many as 175 with an average of 106 +/-31. The actual number at the 2014 peak was 116. Most of the predictions were based on little more than extrapolating statistical patterns in older data. What we really want are forecasts that are based upon the actual physics of sunspot formation, not statistics. The most promising physics-based models we have today actually follow magnetic processes on the surface of the sun and below and are called Flux Transport Dynamo models.

Solar polar magnetic field trends (Credit: Wilcox Solar Observatory)

The sun’s magnetic field is much more fluid than the magnetic field of a toy bar magnet. Thanks to the revolutionary work by helioseismologists using the SOHO spacecraft and the ground-based GONG program, we can now see below the turbulent surface of the sun. There are vast rivers of plasma wider than a dozen Earths, which wrap around the sun from east to west. There is also a flow pattern that runs north and south from the equator to each pole. This meridional current is caused by giant convection cells below the solar surface and acts like a conveyor belt for the surface magnetic fields in each hemisphere. The sun’s north and south magnetic fields can be thought of as waves of magnetism that flow at about 60 feet/second from the equator at sunspot maximum to the poles at sunspot minimum, and back again to the equator at the base of the convection cell. At sunspot minimum they are equal and opposite in intensity at the poles, but at sunspot maximum they vanish at the poles and combine and cancel at the sun’s equator. The difference in the polar waves during sunspot minimum seems to predict how strong the next sunspot maximum will be about 6 years later as the current returns the field to the equator at the peak of the next cycle. V.V Zharkova at Northumbria University in the UK uses this to predict that Cycle 25 might continue the declining trend of polar field decrease seen in the last three sunspot cycles, and be even weaker than Cycle 24 with far fewer than 100 spots. However, a recent paper by NASA solar physicists David Hathaway and Lisa Upton  re-assessed the trends in the polar fields and predict that the average strength of the polar fields near the end of Cycle 24 will be similar to that measured near the end of Cycle 23, indicating that Cycle 25 will be similar in strength to the current cycle.

But some studies such as those by Matthew Penn and William Livingston at the National Solar Observatory seem to suggest that  sunspot magnetic field strengths have been declining since about 2000 and are already close to the minimum needed to sustain sunspots on the solar surface.  By Cycle 25 or 26, magnetic fields may be too weak to punch through the solar surface and form recognizable sunspots at all, spelling the end of the sunspot cycle phenomenon, and the start of another Maunder Minimum cooling period perhaps lasting until 2100. A quick GOOGLE search will turn up a variety of pages claiming that a new ‘Maunder Minimum’ and mini-Ice Age are just around the corner! An interesting on-the-spot assessment of these disturbing predictions was offered back in 2011 by NASA solar physicist C. Alex Young, concluding from the published evidence that these conclusions were probably ‘Much Ado about Nothing’.

What can we bank on?

The weight of history is a compelling guide, which teaches us that tomorrow will be very much like yesterday. Statistically speaking, the current Cycle 24 is scheduled to draw to a close about 11 years after the previous sunspot minimum in January 2008, which means sometime in 2019. You can eyeball the figure at the top of this blog and see that that is about right. We entered the Cycle 24 sunspot minimum period in 2016 because in February and June, we already had two spot-free days. As the number of spot-free days continues to increase in 2017-2018, we will start seeing the new sunspots of Cycle 25 appear sometime in late-2019. Sunspot maximum is likely to occur in 2024, with most forecasts predicting about half as many sunspots as in Cycle 24.

None of the current forecasts suggest Cycle 25 will be entirely absent. A few forecasts even hold out some hope that a sunspot maximum equal to or greater than Cycle 24 which was near 140 is possible, while others place the peak closer to 60 in 2025.

It seems to be a pretty sure bet that there will be yet-another sunspot cycle to follow the current one. If you are an aurora watcher, 2022-2027 would be the best years to go hunting for them. If you are a satellite operator or astronaut, this next cycle may be even less hostile than Cycle 24 was, or at least no worse!

In any event, solar cycle prediction will be a rising challenge in the next few years as scientists pursue the Holy Grail of creating a reliable theory of why the sun even has such cycles in the first place!

Check back here on Friday, February 17 for my next blog!

The Rush to Mars

Even at the start of NASA’s space program in 1958, the target of our efforts was not the moon but Mars. The head of NASA, Werner von Braun was obsessed with Mars, and his Mars Project book published in 1948, was the blueprint for how to do this, which he revised in 1969. He saw the development of the Saturn V launch vehicle as the means to this end.

A major effort running in parallel with Kennedy’s moon program was the development of nuclear rocket technology. This would be the means for getting to Mars in the proposed expedition launch in November, 1981. The program was abandoned in 1972 when President Nixon unceremoniously canceled the Apollo Program and stopped the production of Saturn Vs. That immediately put the kibosh on any nuclear propulsion efforts because the required fission reactors were far too heavy to be lifted into space by any other means. He resigned from NASA once he realized that his dream would never be realized, and died five years later.

Flash forward to 2004 when President George Bush announced his Space Exploration Initiative to include a manned trip to Mars by the 2030s. There would be manned trips to the moon by 2015 to test out technologies relevant to the Mars trip and to learn how to live there for extended periods of time.

By 2008, the lunar portion of this effort was canceled, however the development of the Orion capsule and what is now called the Space Launch System were the legacies of this program still in place and expected to be operational by ca 2019. The rest of the Initiative is now called NASA’s Journey to Mars, and lays out a detailed plan for astronauts learning how to work farther and farther from Earth in self-sustaining habitats, leading to a visit to Mars in the 2030s. Meanwhile, the International Space Station has been greatly extended in life to the mid-2020s so we can finally get a handle on how to live and work in space and solve the many medical issues that still plague this environment.

However, NASA’s systematic approach is not the only one in progress today.

The entire foundation of Elon Musk’s Space-X company is to build and make commercially profitable successively larger launch vehicles leading to the Interplanetary Transport System which will bring 100 colonists at a time to the surface of Mars in about 80 days starting around 2026. Space-X is even partnering with NASA for a sample return mission called Red Dragon in ca 2018. Meanwhile, a competing program called Mars One (see picture above) proposes a crew of four people to land in 2032 with additional crew delivered every two years. . This will be a one-way do-or-die colony, and loss of life is expected. Mars One consists of two entities: the not-for-profit Mars One Foundation, and the for-profit company Mars One Ventures with CEO Bas Lansdorp at the corporate helm.

But wait a minute, what about all the non-tech issues like astronaut health and generating sustainable food supplies? Astronauts have been living in the International Space Station for decades in shifts, and many issues have been identified that we would be hard pressed to solve in only ten more years. NASA’s go-slow approach may be the only one consistent with not sending astronauts to a premature death on mars, with all the political and social ramifications that implies.

The dilemma is that slow trips to Mars, like the 240-day trips advocated by NASA’s plan exacerbate health effects from prolonged weightlessness including bone loss, failing eyesight, muscle atrophy and immune system weakening. These effects are almost eliminated by much shorter trips such as the 80-day target by Space-X. In fact, the entire $100 billion International Space Station raison de etra is to study long term space effects during these long transits. This existential reason for ISS would have been eliminated had a similar investment been made in ion or nuclear propulsion systems that reduced the travel time to a month or less!

Ironically, Werner von Braun knew about this as long ago as 1969, but his insights were dismissed for political reasons that led directly to our confinement to low Earth orbit for the next 50 years!

Check back here on Sunday, January 22 for the next installment!

Space Travel via Ions

For 60 years, NASA has used chemical rockets to send its astronauts into space, and to get its spacecraft from planet to planet. The huge million-pound thrusts sustained for only a few minutes were enough to do the job, mainly to break the tyranny of Earth’s gravity and get tons of payload into space. This also means that Mars is over 200 days away from Earth and Pluto is nearly 10 years. The problem: rockets use propellant (called reaction mass) which can only be ejected at speeds of a few kilometers per second. To make interplanetary travel a lot zippier, and to reduce its harmful effects on passenger health, we have to use rocket engines that eject mass at far-higher speeds.

In the 1960s when I was but a wee lad, it was the hey-day of chemical rockets leading up to the massive Saturn V, but I also knew about other technologies being investigated like nuclear rockets and ion engines. Both were the stuff of science fiction, and in fact I read science fiction stories that were based upon these futuristic technologies. But I bided my time and dreamed that in a few decades after Apollo, we would be traveling to the asteroid belt and beyond on day trips with these exotic rocket engines pushing us along.

Well…I am not writing this blog from a passenger ship orbiting Saturn, but the modern-day reality 50 years later is still pretty exciting. Nuclear rockets have been tested and found workable but too risky and heavy to launch.  Ion engines, however, have definitely come into their own!

Most geosynchronous satellites use small ‘stationkeeping’ ion thrusters to keep them in their proper orbit slots, and NASA has sent several spacecraft like Deep Space-1, Dawn powered by ion engines to rendezvous with asteroids. Japan’s Hayabusha spacecraft also used ion engines as did ESA’s Beppi-Colombo and the LISA Pathfinder. These engines eject charged, xenon atoms ( ions) to speeds as high as 200,000 mph (90 km/sec), but the thrust is so low it takes a long time for spacecraft to build up to kilometer/sec speeds. The Dawn spacecraft, for example, took 2000 days to get to 10 km/sec although it only used a few hundred pounds of xenon!

But on the drawing boards even more powerful engines are being developed. Although chemical rockets can produce millions of pounds of thrust for a few minutes at a time, ion engines produce thrusts measured in ounces for thousands of days at a time. In space, a little goes a long way. Let’s do the math!

The Deep Space I engines use 2,300 watts of electrical energy, and produced F= 92 milliNewtons of thrust, which is only 1/3 of an ounce! The spacecraft has a mass of m= 486 kg, so from Newton’s famous ‘F=ma’  we get an acceleration of a= 0.2 millimeters/sec/sec. It takes about 60 days to get to 1 kilometer/sec speeds. The Dawn mission, launched in 2007 has now visited asteroid Vesta (2011) and dwarf planet Ceres (2015) using a 10 kilowatt ion engine system with 937 pounds of xenon, and achieved a record-breaking speed change of 10 kilometers/sec, some 2.5 times greater than the Deep Space-1 spacecraft.

The thing that limits the thrust of the xenon-based ion engines is the electrical energy available. Currently, kilowatt engines are the rage because spacecraft can only use small solar panels to generate the electricity. But NASA is not standing still on this.

OLYMPUS DIGITAL CAMERA

The NEXIS ion engine was developed by NASA’s  Jet Propulsion Laboratory, and this photograph was taken when the engine’s power consumption was 27 kW, with a thrust of 0.5 Newtons (about 2 ounces).

An extensive research study on the design of megawatt ion engines by the late David Fearn was presented at the Space Power Symposium of the 56th International Astronautical Congress in 2005. The conclusion was that these megawatt ion engines pose no particular design challenges and can achieve exhaust speeds that exceed 10 km/second. Among the largest ion engines that have actually been tested so far is a 5 megawatt engine developed in 1984 by the Culham Laboratory. With a beam energy of 80 kV, the exhaust speed is a whopping  4000 km/second, and the thrust was 2.4 Newtons (0.5 pounds).

All we have to do is come up with efficient means of generating megawatts of power to get at truly enormous exhaust speeds. Currently the only ideas are high-efficiency solar panels and small fission reactors. If you use a small nuclear reactor that delivers 1 gigawatt of electricity, you can get thrusts as high as 500 Newtons (100 pounds). What this means is that a 1 ton spacecraft would accelerate at 0.5 meters/sec/sec and reach Mars in about a week!  Meanwhile, NASA plans to use some type of 200 kilowatt, ion engine design with solar panels to transport cargo and humans to Mars in the 2030s. Test runs will also be carried out with the Asteroid Redirect Mission ca 2021 also using a smaller 50 kilowatt solar-electric design.

So we are literally at the cusp of seeing a whole new technology for interplanetary travel being deployed. If you want to read more about the future of interplanetary travel, have a look at my book ‘Interplanetary Travel: An astronomer’s guide’, which covers destinations, exploration and propulsion technology, available at Amazon.com.

Stay tuned!

Check back here on Wednesday, January 11 for the next installment!

Image credits:

Ion engine schematic  http://plasmalab.aero.upm.es/~plasmalab/information/Research/ElectricPropulsion.html

Star Destroyer

http://s1187.photobucket.com/user/ringa52577/media/SD-2.jpg.html

Why NASA needs ARMs

In 2013, a small 70-meter asteroid exploded over the town of Chelyabinsk and injured 3000 people from flying glass. Had this asteroid exploded a few hours earlier over New York City, the flying glass hazard would have been lethal for thousands of people, sending thousands more into the emergency rooms of hospitals for critical-care treatment. Of all the practical benefits of space exploration, it is hard to argue that asteroid investigations are not a high priority above dreams of colonization of the moon and Mars.

So why is it that the only NASA mission to actually try a simple method to adjust the orbit of an asteroid cannot seem to garner much support?

There has been much debate over the next step in human exploration: whether to go back to the moon or take the harder path to Mars. The later goal has been much favored, and for the last decade or so, NASA has developed a step-by-step Journey to Mars approach for doing this, beginning with the development of the SLS launch vehicle, and the testing out of many necessary systems, technologies and strategies to support astronauts making this trip, both quickly and safely. Along with numerous Mars mapping and rover missions now in progress or soon to be launched, there are also technology development missions to test out such things as solar-electric ‘ion’ propulsion systems.

One of these test-bed missions with significant scientific returns is the Asteroid Redirect Mission to be launched in ca 2021 for a cost of about $1.4 billion. NASA’s first-ever robotic mission will visit a large near-Earth asteroid, collect a multi-ton boulder from its surface, and use it in an enhanced gravity tractor asteroid deflection demonstration. The spacecraft will then redirect the multi-ton boulder into a stable orbit around the moon, where astronauts will explore it and return with samples in the mid-2020s.

But all is not well for ARM.

ARM was proposed in 2010 during the Obama Administration as an alternative to the canceled Constellation Program proposed by the Bush Administration, so with the new GOP-dominated administration set on dismantling all of the Obama Administrations’ legacy work, there is much incentive to eliminate it for political reasons alone.

Reps. Lamar Smith (R-Texas), chairman of the HCSST, and Brian Babin (R-Texas), chairman of the HSST space subcommittee reportedly feel that the incoming Trump administration should be “unencumbered” by decisions made by the current one — like what they want to do with the ACA . They claim to have access to “honest assessments” of ARM’s value rather than “farcical studies scoped to produce a predetermined outcome.” The House’s version of the 2017 FY appropriations bill includes wording that would force NASA to fully defund the ARM program. Furthermore, Smith and Babin wrote, “the next Administration may find merit in some, if not all, of the components of ARM, and continue the program; however, that decision should be made after a full and fair review based on the merits of the program and in the context of a larger exploration and science strategy.” Similar arguments will no doubt be used to cancel climate change research, which has also been deemed politically biased and unscientific by the current, incoming administration.

But ARM is no ordinary ‘exploration and science’ space mission, even absent its unique ability to test the first high-power ion engines for interplanetary travel, and retrieve a large, pristine multi-ton asteroid sample. All other NASA missions have certainly demonstrated their substantial scientific returns, and this is often the key justification that allows them to proceed. Mission technology also affords unique tech spinoff opportunities in the commercial sector that makes the US aerospace industrial base very happy to participate. But these returns all seem rather abstract, and for the person-on-the-street rather hard to appreciate.


For decades, astronomers have been discovering and tracking 100s of thousands of asteroids. We live in an interplanetary shooting gallery, where some 15,000 Near Earth Objects have already been discovered, and 30 new ones added every week. NEOs, by the way, are asteroids that come within 30 million miles of Earth’s orbit. These asteroids measure 1 kilometer or more, and statistically over 90% of this population has now been identified. But only 27% of those 140 meters or larger have been discovered. Once their orbits are determined, we can make predictions about which ones will pose an danger to Earth.

Currently there are 1,752 potentially hazardous asteroids  that come within 5 million miles of Earth (20 times Earth-moon distance). There are none predicted to impact Earth in the next 100 years. But new ones are found every week, and between now and February 2017, one object called 2016YJ about 30 meters across will pass within 1.2 lunar distances of Earth. The list of closest approaches in 2016 is quite exciting to look through The object 2016 QA2 discovered in 2016 in the nick of time, was about 70 meters across and came within 53,000 miles of Earth. Upon impact, it would have been an event similar to Chelyabinsk. Even larger, and far more troubling very close encounters have been predicted for the 325-meter asteroid Apophis in 2029, and the 1-kilometer asteroid 2001WN5 in 2028 and well within the man-made satellite cloud that surrounds Earth.

The first successful forecast of an impact event was made on 6 October 2008 when the asteroid 2008 TC3 was discovered. It was calculated that it would hit the Earth only 21 hours later. Luckily it had a diameter of only three meters and did not cause any damage. Since then, some stony remnants of the asteroid have been found. But this object could just as easily have been a 100-meter object exploding over New York City or London, with devastating consequences.

So in terms of planetary defense, asteroids are a dramatically important hazard we need to study. For some asteroids, we may have as little as a year to decide what to do. Although many mitigation strategies have been proposed, none have actually been tested! We need to test as many different orbit-changing strategies as we can before the asteroid with Earth’s name written on it is discovered.

Honestly, what more practical benefit can there be for a NASA mission than to materially protect Earth and our safety?

Check back here on Thursday, January 5 for the next installment!