Top Ten Posts of 2014

With the end of 2014 upon us, I figured it was time to look back over this year’s material on Drew Ex Machina and see which of the 70 essays I posted during this site’s first year on the Web proved to be most popular. Part of this exercise is an attempt to figure out what kinds of articles my readers prefer so that I can focus my attention on similar topics in 2015. I was also just plain curious to see which articles were the most popular. What follows is a review of the Top Ten most popular articles posted on this site during 2014 based on a raw tally of their page views. If you are interested in reading any of these articles, they can be accessed by clicking on the titles or the feature images.


A picture of Zond 3 which was very similar to the Mars-bound Zond 2. (NASA)

#10 Zond 2: Old Mysteries Solved New Questions Raised

For over thirty years I have been a serious observer of the Soviet (now Russian) space program and have been particularly interested in their lunar and planetary exploration efforts. While there are a fair number of mysteries surrounding these programs, the one mission that has kept my interest the longest has got to be the Zond 2 mission launched fifty years ago. For a time, analysts and historians like myself believed that Zond 2 might have been an attempt to land on Mars a full decade ahead of America’s Viking mission (see “The Mystery of Zond 2”). But with the revelation two decades ago that Zond 2 did not carry a lander but an advanced photographic imaging system instead, the conventional wisdom has been that it was a flyby mission in competition with the American Mariner 4 mission to Mars despite the odd choice of its trajectory. This essay in Drew Ex Machina reviewed the latest evidence from a variety of sources to show that Zond 2 was neither a flyby nor a lander mission.


A view of the Martian surface by NASA’s Curiosity rover inside Gale Crater. (NASA)

#9 The New Search for Life on Mars

With the steady stream of discoveries coming from spacecraft in orbit and roving on the surface of Mars about it potential habitability past and even present, interest in looking for life on our neighbor is as great as it ever has been. Work on developing instruments to detect life on the Red Planet stretches back more than a half a century to the beginnings of planetary exploration (see “The Automated Biological Laboratory”) but, as the ambiguous results from Viking’s biological experiments of 1976 demonstrate, finding proof of life on another world is turning out to be more difficult than scientists originally expected. This essay reviews an article from Scientific American that presents some of the latest methods currently under development to detect life on Mars. With luck, some of these new techniques might be employed on a future Mars lander or rover mission for the first in situ search for life on Mars since Viking.


An artist’s depection of Kepler 186f. (NASA Ames/SETI Institute/JPL-CalTech)

#8 Habitable Planet Reality Check: Kepler 186f

One of my pet peeves going back nearly twenty years to the discovery of the first extrasolar planets orbiting Sun-like stars has been overblown claims of the potential habitability of some of these planets made by their discoverers and especially wildly optimistic enthusiasts. The media has then happily repeated and far too often distorted these frequently dubious claims without bothering to check their veracity. Being the first to discover a habitable planet and the first to report that discovery has all too often trumped good science and journalism. Do not get me wrong: I am an enthusiastic believer that our galaxy is teaming with habitable worlds but I can not in good conscience repeat a claim that a planet is “potentially habitable” when the observations and the science obviously does not support the claim.

In response to this unhealthy trend in the scientific community and media, I started the “Habitable Planet Reality Check” series of articles on Drew Ex Machina (see this site’s Planetary Habitability page for a complete listing of these and related articles). In these articles I have attempted to cut through the hype to give an honest assessment on the potential habitability of various extrasolar planets based on the best available analysis of the observations and the current scientific understanding of planetary habitability. For the first in this series of articles, I examined the case of Kepler 186f whose discovery was announced in 2014. Kepler 186f is an Earth-size planet found in the data of NASA’s Kepler mission orbiting inside the habitable zone of a nearby red dwarf star. While I started out with the intent of debunking the claim, it turns out that Kepler 186f appears to be one of only a couple of currently known extrasolar planets to have a scientifically reasonable claim of being a “potentially habitable planet”.


Launch of the first Apollo orbital test flight on SA-6. (NASA)

#7 50 Years Ago Today: The First Apollo Orbital Test Flight

One of the major space-related news stories of 2014 was the launch of the first Orion test flight, EFT-1. While NASA is currently working to rebuild the capability it once had with Apollo using the latest technology, it seems difficult to believe that it has already been a half a century since the first Apollo test flights which coincidentally started using the same launch complex as EFT-1 (see “From Apollo to Orion: Space Launch Complex 37”). This essay retells the story of the first orbital test flight of Apollo hardware designated A-101. Launched on May 28, 1964, this mission was the first of a series of test flights of Apollo hardware and technology that culminated with the first landing on the Moon only a half a decade later. Also included in this popular post is a 1964 NASA documentary video about this mission. A companion piece, “50 Years Ago Today: The Second Apollo Orbital Test Flight”, recounts the A-102 mission launched September 18 later that year.


Artist depiction of Alpha Centauri Bb. (ESO/L. Calçada/Nick Risinger)

#6 The Search for Planets Around Alpha Centauri

Ever since I was a kid, I have been fascinated by the nearby α Centauri system and the prospects of its twin Sun-like stars having habitable planets. Considering the number of science fiction stories over the decades set in this star system, it is a safe bet that I am not alone. But with the announcement of the discovery of α Centauri Bb two years ago, professional interest in this system has increased like never before. In this first of a series of articles, the events leading to the discovery of α Centauri Bb and the current status of the work to confirm its existence is examined. In a follow up article, “The Search for Planets Around Alpha Centauri – II”, the history of past searches for planets in the α Centauri system are examined with an assessment of the limits for the maximum size of planets that might exist. Future searches and what they might find are also examined.


Comparison of Earth and Neptune along with a representatio of the relative size of a planet at the transition between terrestrial planets and mini-Neptunes.

#5 Habitable Planet Reality Check: Terrestrial Planet Size Limit

Even though the primary mission of NASA’s Kepler spacecraft has ended, the analysis of its huge database continues. One of the many outstanding questions that this analysis has begun to address for the first time is the nature of the transition from terrestrial planets like Earth to non-rocky planets like Neptune. While planets in this size range do not exist in our solar system, astronomers have been finding and characterizing the properties of dozens of such worlds orbiting stars observed by the Kepler mission. This article summarizes the most recent work in this area which now shows that planets with radii larger than about 1½ times that of the Earth (corresponding to masses greater than 4 to 6 times that of the Earth) are unlikely to be terrestrial planets but are probably mini-Neptunes instead. One of the consequences of this continuing work is that the overwhelming majority of extrasolar “super-Earths” that enthusiasts have touted in recent years as being potentially habitable are in fact not even terrestrial planets, never mind potentially habitable. This same topic with discussion of the recent discovery of the mini-Neptune in Kepler’s data, designated PH3 c,was also the subject of one of my regular posts on the popular Centauri Dreams web site (see “The Transition from Rocky to Non-Rocky Planets”).


An artist’s fanciful impression of Kapteyn b with Omega Centauri visible in the background. (PHL/UPR Arecibo)

#4 Habitable Planet Reality Check: Kapteyn b

One of the planetary discoveries that got a lot of attention in 2014 was the pair of planets found orbiting the ancient nearby red dwarf known as Kapteyn’s Star. In addition to providing insights into the planet formation process during the earliest history of our galaxy, it turns out that one of these planets, Kapteyn b, orbits inside the habitable zone of its sun. This has prompted a number of overly optimistic claims in the media that this planet is the oldest and closest potentially habitable extrasolar planet currently known. Unlike the situation with Kepler 186f which was the subject of my first habitable planet reality check (see “Habitable Planet Reality Check: Kepler 186f” which was the 9th most popular post on Drew Ex Machina this year), unfortunately it turns out that this claim is unwarranted. It is much more likely that Kapteyn b is a mini-Neptune than it is a terrestrial planet never mind a habitable terrestrial planet.


The launch of SA-5 – the coolest rocket ever. (NASA)

#3 The Coolest Rocket Ever

Like a lot of space enthusiasts, my interest in spaceflight stretches back to when I was a child (see “When I Thought My Dad Was an Astronaut”). In this popular post, I tell the story about what I think is the coolest looking rocket in history: the Saturn I SA-5. This one-of-a-kind configuration of the Saturn I Block II rocket was the first orbital test flight of America’s first heavy lift launch vehicle launched on January 29, 1964. I have had a keen interest in this rocket ever since I first stumbled upon an old Newsweek article about its launch at my grandparents lakeside cabin over four decades ago. Also included in this piece is a 1964 documentary video produced by the manufacturer of the Saturn I second stage, Douglas, presenting details and excellent video of this historic mission.


Depiction of New Horizons flying past Pluto on July 14, 2015. (JHUAPL/SwRI)

#2 The Next Mission to Pluto

With less than a year until its long awaited encounter with Pluto, NASA’s New Horizons mission has generated a significant amount of interest during 2014. Probably as a result of this, the second most popular article on Drew Ex Machina posted in 2014 has been an analysis of options for a follow up mission to this distant world. Even a repeat of the New Horizons mission, which could reach Pluto by 2039, would reveal much new information about this frigid dwarf planet especially when factoring in a quarter century’s worth of advances in technology and remote sensing techniques. Given how long it took to plan, develop, fund, build, launch and get New Horizons to its destination, it is not too early to start considering a new mission to Pluto.


Engines used in the Saturn family of launch vehicles (NASA)

#1 A History of American Rocket Engine Development

Between a spectacular failure of an OSC Antares launch apparently caused by a refurbished Russian engine and threats to the supply of the Russian-built RD-180 engines used by ULA’s Atlas V, the state of rocket engine development in the US has been a subject of much interest in 2014. This probably explains why the most popular post on Drew Ex Machina in 2014 was this essay about the history of American rocket engine development. This piece recounts the origins of the most important rocket engines of the early Space Age during the 1950s and 1960s. After the development of the Space Shuttle SSME (also known today as the Rs-25), most rocket engines used on American launch vehicles had been just incrementally upgraded and modernized versions of the earliest rocket engine designs. Only a couple of totally new engines have been developed in the US over the past couple of decades and actually flown: the RS-68 used on ULA’s Delta IV and the Merlin-series engine for the Falcon built by SpaceX. Given that it has taken decades of bad government policy, a long string of competition-killing corporate mergers and a series of bad business decisions to get us into the situation we find ourselves today, it will likely take a while for today’s issues to be resolved and for American rocket engine technology development to flourish once again.



I would like to take this opportunity to thank the 12,000-plus people around the globe who have taken time to read these Top Ten and other 60 posts on Drew Ex Machina during its first calendar year on the Web. The many comments and feedback on this site as well as in other forums have also been greatly appreciated. I intend to continue posting interesting essays on space-related topics during 2015 and hope that you continue reading and enjoying them.

Happy New Year!   Drew LePage


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