Top Ten Posts of 2016

Now that we are at the end of 2016, I figured it was time to look back over this year’s material on Drew Ex Machina and see which of the 45 new essays I posted during this site’s third year online, along with earlier published material, proved to be most popular to my readers. In addition to satisfying my curiosity, 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 over the coming months when possible. What follows is a review of the Top Ten most popular articles on this site during 2016 based on a raw tally of their page views. If you are interested in checking out any of these articles for yourself, they can be accessed by clicking on the titles or the feature images in the reviews that follow.


An artist's depiction of the X-20 Dyna Soar during reentry. (NASA)

An artist’s depiction of the X-20 Dyna Soar during reentry. (NASA)

#10 The Future That Never Came: The X-20 Dyna Soar

When one thinks about “space planes”, vehicles like the USAF’s automated X-37B or NASA’s now-retired Space Shuttle come to mind. But long before these spacecraft ever flew, there was the grand daddy of all American space planes known the X-20 Dyna Soar. The #10 ranked essay on Drew Ex Machina in 2016 recounts the history of this cutting edge craft which started as a series of studies stretching back to before the dawn of the Space Age. And when the US was formulating its plans to send people into space in response to the launching of the first satellite by the Soviet Union, the X-20 Dyna Soar was one of the many projects that was funded to help the nation gain the lead in what would turn out to be a space race between Cold War adversaries. Unfortunately for its many supporters, the X-20 Dyna Soar program was cancelled in December 1963 when the USAF was unable to define a mission for this craft to justify the expense of its development. Instead, the USAF shifted the focus of its man-in-space efforts to utilizing NASA’s Gemini technology for the Manned Orbiting Laboratory (see “The USAF Manned Orbiting Laboratory Test Flight“). While the X-20 Dyna Soar would never fly, it did start the development of the key technologies that future space planes would need.


This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. (ESO/M. Kornmesser)

This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. (ESO/M. Kornmesser)

#9 Habitable Planet Reality Check: Proxima Centauri b

One of the biggest space-related stories of 2016 has got to be the announcement on August 29 by an international team of astronomers of the discovery of an Earth-size planet orbiting inside the habitable zone of the closest known star to us, Proxima Centauri. The #9 ranked essay on Drew Ex Machina in 2016 took a close look at the events which led to the discovery of this exoplanet now known as Proxima Centauri b as well as the claims about the potential habitability of this newly discovered world. This high ranking is not too surprising given that the second most popular article on Drew Ex Machina in 2015 was about the on going search for exoplanets orbiting Proxima Centauri (see “The Search for Planets Around Proxima Centauri”).

Although there is still much to learn about our new neighbor and doubts linger among some about the ability of small red dwarfs like Proxima Centauri to support habitable worlds, it appears that Proxima Centauri b has the best prospects of being potentially habitable out of all the extrasolar planets currently known (see “The Top Five Known Potentially Habitable Planets”). But even if it does not prove to be habitable, the future study of this and other nearby, potentially habitable exoplanets (and even the “near misses”) promises to provide scientists with the data they need to sort through all of the predictions being made to help determine the true limits of planetary habitability.


The Apollo-Little Joe II A-004 as it appeared on the launch pad at WSMR before its launch on January 20, 1966. (NASA)

The Apollo-Little Joe II A-004 as it appeared on the launch pad at WSMR before its launch on January 20, 1966. (NASA)

#8 The First Launch of Apollo Flight Hardware

The news in recent years has been filled with stories about the testing of a new generation of crewed spacecraft like Orion, CST-100 and the Dragon to take people to low Earth orbit and beyond. But the success of all of these spacecraft programs owes much to the tests conducted by NASA and its contractors a half century earlier as part of the process to develop and build Apollo. The #8 ranked essay on Drew Ex Machina in 2016 took a close look at the series of launch abort tests flown in support of the Apollo program during 1965 to the beginning of 1966. This series of flights culminated in the first test flight using a production Apollo spacecraft, CM-002, which stressed the new spacecraft to its design limits during the Apollo A-004 abort test launched on January 20, 1966. These were followed in 1966 by first suborbital test flights of the Apollo-Saturn IB (see “The First Flight of the Apollo-Saturn IB” and “AS-202: The Last Test Flight Before Apollo 1“) as well as a unique orbital test flight of the Saturn IB (see “AS-203: NASA’s Odd Apollo Mission“) before the crewed Apollo 1 test flight was to be attempted.


Engine used in Saturn launch vehicles (NASA)

Engines used in Saturn launch vehicles (NASA)

#7 A History of American Rocket Engine Development

It is not too surprising that the #7 spot for the Top Ten posts of 2016 was also the most popular post on Drew Ex Machina in 2014 and 2015. With the ongoing issues of the Russian-built RD-180 engines used by ULA’s Atlas V and efforts to develop engines for new families of American launch vehicles, the state of rocket engine development in the US has been a subject of much interest recently. This essay recounts the origins of the most important large rocket engines of the early Space Age developed during the 1950s and 1960s. After the development of the Space Shuttle SSME in the 1970s (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 two totally new engines have been developed in the US for satellite launch vehicles 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.



The launch of SA-5 from LC-37 on January 29, 1964. (NASA)

#6 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 post (which also ranked #3 in the Top Ten of 2014), 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 Aircraft, presenting details and excellent video of this historic mission.


A vies of Saturn 500F at Pad A at dawn on June 22, 1966. (NASA/KSC)

A view of Saturn 500F at LC-39A at dawn on June 22, 1966. (NASA/KSC)

#5 The Saturn 500F: The Moon Rocket That Couldn’t Fly

A half century ago, NASA was gearing up for the final push to land astronauts on the Moon. One of the key milestones to reach that goal was the completion of the facilities at Launch Complex 39 where the Apollo-Saturn V would be assembled, checked out and launched. On May 25, 1966 NASA rolled out a non-flight model of their Moon rocket called Saturn 500F to checkout the newly completed VAB and Pad A at LC-39. This post on Drew Ex Machina, which ranked #5 for 2016, tells the story of the Saturn 500F and the various tests that were performed during the summer of 1966. Immediately following the disassembly of Saturn 500F, work began on the first Saturn V flight article for the Apollo 4 test flight of November 1967.


Artist conceptions of various Earth-size planets. (PHL/ESA-Bubble/NASA)

Artist conceptions of various Earth-size planets. (PHL/ESA-Bubble/NASA)

#4 The Prevalence of Earth-Size Planets Around Sun-Like Stars

The primary driver for the design of NASA’s Kepler spacecraft and its mission was the ability to detect Earth-size planets in Earth-like orbits around Sun-like stars – what are commonly referred to as “Earth twins”. While thousands of exoplanets have been found using Kepler, no true Earth twins have been uncovered to date. This is not so much because such planets are rare but rather they have proven to be more difficult to detect than originally expected. In the #4 ranked essay on Drew Ex Machina in 2016, the doctoral thesis of Erik Petigura is reviewed where he determines the prevalence of Earth-size planets around Sun-like stars primarily in short-period orbits using the first three years of data from Kepler’s four-year primary mission. Extrapolations from his results suggest that maybe one in ten Sun-like stars have rocky Earth-size planets orbiting inside of their habitable zones. As the analysis of the data from Kepler’s entire primary mission continues employing ever more sophisticated data processing techniques which promise to reveal yet more new worlds, we can only hope that the discovery of the first true Earth-twin may be announced sometime soon.


A picture of a lunar railroad diorama designed by Alan Cerny and built by Bob Hayden that appeared in the April 1978 issue of Model Railroader. (MRR/Kalmbach Publishing)

A picture of a lunar railroad diorama designed by Alan Cerny and built by Bob Hayden that appeared in the April 1978 issue of Model Railroader. (MRR/Kalmbach Publishing)

#3 A Lunar (Model) Railroad

Sometimes magazine articles can have a bigger influence than their authors ever intended and one of those has got to be an article on modelling a lunar railroad which was published in the April 1978 issue of Model Railroader. Originally meant as an April Fools joke which played off of the public’s keen interest in space four decades ago, this article is still remembered by many even to this very day. The #3 ranked post on Drew Ex Machina in 2016 was a piece I wrote about this old “joke” which influenced a lot of would-be modelers over the decades including myself.


Artist's depiction of an Earth-like Kepler 186f. (NASA Ames/SETI Institute/JPL-CalTech)

Artist’s depiction of an Earth-like Kepler 186f. (NASA Ames/SETI Institute/JPL-CalTech)

#2 Habitable Planet Reality Check: Kepler 186f Revisited

In response to this unhealthy trend in the scientific community and especially the media overstating the potential habitability of newly discovered exoplanets, I started the “Habitable Planet Reality Check” series of articles on Drew Ex Machina shortly after the web site was established (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 April 17, 2014 – just three weeks after Drew Ex Machina came online

While I originally started out in my first review in 2014 with the intent of debunking the claim, it turns out that Kepler 186f appears to have among the best chances of being potentially habitable of all exoplanets currently known (see “The Top Five Known Potentially Habitable Planets”). In the second-most popular essay on Drew Ex Machina in 2016, I revisited the case for Kepler 186f and reassess its potential habitability given what we have learned about it and other exoplanets over the intervening two years. The new data presented in the updated assessment published on the second anniversary of this world’s discovery only strengthens the case for this distant exoplanet’s promising prospects.


This image shows the solar system’s eight recognized planets in order of increasing distance from the Sun to a common size scale. (Lunar and Planetary Institute)

This image shows the solar system’s eight recognized planets in order of increasing distance from the Sun to a common size scale. (LPI)

#1 Practical Limit of Trip Times to the Planets

In March of 2016, the space-related media was filled with headlines about a new laser-based propulsion technology which could allow trips to Mars in as little as a half an hour. Of course such sensational claims deserve a sober review which was the purpose of the top ranked article on Drew Ex Machina in 2016. Dusting off some calculations I did as a physics undergrad a third of a century ago, I demonstrated that any conventional cargo would be destroyed by the huge g-forces experienced during a putative half-hour trip to Mars. In fact, barring any unforeseen breakthroughs in physics which allows us to invent scifi tech such as “inertial dampers” or the like, we are not likely to ever see trip times to Mars for human passengers of less than a day. Still, if a propulsion technology is developed that permits the construction of my hypothetical “1-g ship”, calculations show that it would be possible to reach any point in the inner solar system in less than a week or any planet in the outer reaches of our system in just a couple of weeks – far faster than our current technology allows but still fast enough to open a whole universe of possibilities for the exploration (and exploitation!) of the solar system.


pic_2014_01 021_600x600I would like to take this opportunity to thank the over 135,000 people from around the globe who have taken time to read these Top Ten as well as many of the other 178 essays on Drew Ex Machina during 2016. 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 2017 and hope that all of you continue reading and enjoying them.

Happy New Year!   Drew LePage


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Related Reading

“The Top Ten Posts of 2014”, Drew Ex Machina, December 31, 2014 [Post]

“The Top Ten Posts of 2015”, Drew Ex Machina, December 31, 2015 [Post]