Centauri Dreams
Imagining and Planning Interstellar Exploration
Marc Millis on Mach Effect Thruster, EmDrive Tests
Marc Millis spent the summer of 2017 at the Technische Universität Dresden, where he taught a class called Introduction to Interstellar Flight and Propulsion Physics, a course he would also teach at Purdue University last November. The former head of NASA’s Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, Marc participated in the SpaceDrive project run by Martin Tajmar in Dresden, an effort that has been in the news with its laboratory testing of two controversial propulsion concepts: The Mach Effect Thruster and the EmDrive. Marc’s review comments on modeling for the former were almost as long as Tajmar’s draft paper. Described below, the SpaceDrive project is a wider effort that includes more than these two areas — neither the EmD or MET thruster had reached active test phase during the summer he was there — but the ongoing work on both occupies Millis in the essay that follows.
by Marc Millis
You may have noticed a renewed burst of articles about the EmDrive. What prompted this round of coverage was an interim report, part of the progress on Martin Tajmar’s ‘SpaceDrive’ project to carefully test such claims. Tajmar’s conference paper [citation below] is one of the early steps to check for false-positives. I expect more papers to follow, each progressing to other possibilities. It might take a year or so more before irrefutable results are in. Until then, treat the press stories about certain conclusions as highly suspect.
On Tajmar’s work, this quote from his conference paper:
Within the SpaceDrive project [6], we are currently assessing the two most prominent thruster candidates that promise propellantless propulsion much better than photon rockets: The so-called EMDrive and the Mach-Effect thruster. In addition, we are performing complementary experiments that can provide additional insights into the thrusters under investigation or open up new concepts. In order to properly test the thruster candidates, we are constantly improving our thrust balance facility as well as checking for thruster-environment interactions that can lead to false thrust measurements.
The Mach Effect Thruster is a different approach to the goal of a non-rocket spacedrive, but one that is rooted in unsolved questions in physics where there is a chance for new discoveries. Its theory led to a testable prediction that then evolved into an idea for a propulsive effect.
The unsolved physics question is: “What is the origin of inertial frames?” One attempt to answer that is called “Mach’s Principle” (term coined by Einstein to describe Ernst Mach’s perspective), which is roughly: “inertia here, because of matter out there.” The idea is that the phenomenon of inertia is an interaction between that mass and all the surrounding mass in the universe (presumed gravitational in nature). Jim Woodward picked up on a version of this from Dennis Sciama, and noticed that the inertial mass of an object can fluctuate if its energy fluctuates (think energy in a capacitor). That led to an idea for a propulsive effect by varying the distance between two fluctuating inertias. Unlike the EmDrive, this idea has been in the peer-reviewed literature from the beginning, with some of the more relevant papers being:
Woodward, J. F. (1990). A New Experimental Approach to Mach’s Principle and Relativistic Gravitation, in Foundations of Physics Letters, 3(5): 497-506.
Woodward, J. F. (1991). Measurements of a Machian Transient Mass Fluctuation, in Foundations of Physics Letters, 4(5): 407-423.
Woodward, J (1994), “Method for Transiently Altering the Mass of an Object to Facilitate Their Transport or Change their Stationary Apparent Weights,” US Patent # 5,280,864.
Woodward, J. (2012). Making Starships and Stargates, Springer.
Fearn, H. & Wanser, K. (2014). Experimental Tests of the Mach Effect Thruster. Journal of Space Exploration, 3: 197-205.
Martin Tajmar’s laboratory results can be summarized this way: False positive thrusts were observed under conditions where there should be no thrusting or only minor thrusting. More systematic checks have to be made prior to testing the thrusters at their nominal and maximum operating parameters. The mismatch was more pronounced for the EmDrive than for the Mach Effect Thruster. In both cases it is premature to reach definitive conclusions since this is a work in progress. And if any thrusters do pass all those tests, then more tests will commence to figure out how the thrusters operate (varying conditions to see which affect the thrust levels).
In the case of the EmDrive, only 2 W of the more normal 60 W of power was made available to the thruster. Even at that low power level, thrusts of about 4 µN were observed, which is more than the 2.6 µN expected from the claims from Sonny White’s tests. The more revealing observations were that thrusts were observed when the EmDrive was not supposed to be thrusting. When the EmDrive was pointed to a non-thrusting direction, thrusts were still observed. When the power to the thruster was sent to an attenuator to further reduce the power to the thruster by a factor of 10,000, thrusting at the prior level was still observed.
These observations do not bode well for the EmDrive’s claims of real thrust, but it is too early to firmly dismiss the possibilities. One suspect for the false positive is the interaction with the current to the device and the Earth’s magnetic field, where a current of 2-amps in a few cm of wires can produce a thrust in the µN range. Further tests are planned after adding more magnetic shielding and operating over different power levels.
In the case of the Mach Effect Thruster – which by the way, none of the press articles mentioned – the findings were less pessimistic. Again there were thrusts measured in excess of what was expected for the low power levels (0.6 versus 0.02 µN). Unlike the EmDrive’s mismatch, no thrust was observed when the Mach Effect Thruster was pointed to a non thrusting direction. There was, however, a case where the thrust direction did not change when the thruster direction was flipped. The suspected causes to be further investigated include both magnetic and thermal (expansion) effects.
A word of advice: if you plan to look at Tajmar’s paper. When I tried my usual “rush read” through the paper by reading the abstract and scanning the figures, I misled myself. Read the full text that accompanies the figures to know what you are really looking at. It’s a short article.
Regarding some representative press articles, here is a quick assessment
(1) David Hambling, New Study Casts Doubt on the “Impossible” EmDrive, But this weird propulsion idea isn’t dead yet
This one goes into more detail than the other articles about what was actually done and not done and does link to its information sources. It does not mention the Mach Effect Thruster.
(2) Mike Wall, ‘Impossible’ EmDrive Space Thruster May Really Be Impossible
This one mentions the doubt, but leaves the door open just a bit. Although it does not mention the Mach Effect Thruster also under test, it does at least give a link to the core article and mentions where it came from.
This article talks more about the old claims and expectations than what was really in the new paper. It does not mention the Mach Effect Thruster.
(4) Mike Wehner, NASA’s ‘impossible’ fuel-free engine is actually impossible
More short-hand opinion, and again, no mention of the Mach Effect Thruster.
The takeaway: Science does not proceed by proclamation. Despite what headlines may say, laboratory work is a matter of refining techniques and bringing precision to bear on prior claims. At the moment, evaluation of the EmDrive and Mach Effect thruster continues, with no guarantee that either of these effects may prove genuine, but let’s let the process play out.
The Tajmar paper is Tajmar et al., “The SpaceDrive Project – First Results on EMDrive and Mach-Effect Thrusters,” presented at the Space Propulsion 2018 conference in Seville, Spain (full text).
Enter the ‘Clarke Exobelt’
It’s interesting to consider, as Hector Socas-Navarro does in a new paper, the various markers a technological civilization might leave. Searching for biosignatures is one thing — we’re developing the tools to examine the atmospheres of planets around nearby stars for evidence of life — but how do we go about looking for astronomical evidence of a technological society, one found not by detection of a directed radio or laser beacon but by observation of the stars around us?
Various candidates have been suggested, the most famous being the Dyson sphere, in which an advanced civilization might choose to trap the energy output of its entire star, and we’re in the era of searches for such objects, as witness the Glimpsing Heat from Alien Technologies effort at Penn State. But there are many other suggestions, ranging from detecting antimatter used for power or propulsion, analyzing Fast Radio Bursts for evidence of manipulation as a propulsion system, and looking at depletion of metals in a stellar disk (asteroid mining).
Image: Astronomer Hector Socas-Navarro (Instituto de Astrofísica de Canarias). Credit: IAC.
What Socas-Navarro has in mind is a technology we have already begun to deploy and will presumably see in accelerated use. Delightfully, he has named his idea ‘the Clarke Exobelt’ (CEB) in a nod to the father of the communications satellite, an apt choice given that he defines the idea as the collection of objects, including non-functional ones, in geostationary and geosynchronous orbits around a planet. An astronomer at the Instituto de Astrofísica de Canarias, Socas-Navarro believes that because there is no natural ‘preference’ for this orbit, the detection of a population of objects within it would be highly suggestive of an artificial origin.
Published in The Astrophysical Journal, the paper has caught the eye of enough Centauri Dreams readers that I have five copies of it in my inbox. Seeing the Clarke name associated with it is enough to pique my interest — would that we had Sir Arthur’s own thoughts on the matter! Socas-Navarro points out that there is a certain economy in searching for Clarke Exobelt objects, in that current techniques to detect exoplanets and exomoons should also be able to detect a large enough cluster of technologies in geosynchronous orbits.
The paper, then, is a suggestion that we begin looking for this kind of technosignature amongst the other possibilities. The challenge is in the extrapolation, for to be detectable with our current and near-future technologies, such an Exobelt would have to be densely populated. Our own Clarke belt is relatively sparse, with two-thirds of existing satellites in low orbits. Socas-Navarro believes, however, that the realm of geostationary and geosynchronous satellites is destined to grow, and his simulations show that if it does, it will at some point become detectable:
The geostationary orbit, often named after Clarke, who explored its practical usefulness for communication purposes (Clarke 1945), is specially interesting because satellites placed there will remain static as seen from the ground reference frame. However, the available space in that orbit is limited. A moderately advanced civilization might eventually populate it with a relatively high density of objects, making it advisable (cheaper in a supply-and-demand sense) to use geosynchronous orbits when possible for those satellites whose requirements are less strict and allow for some degree of movement along the North-South direction on the sky. Over time, one might expect that societal needs would eventually drive an increase of object density in a band around the geostationary orbit, forming a CEB.
Using Earth’s current satellite population as a reference, the author creates a Clarke Exobelt model using as parameters radius, width, face-on opacity and inclination of the equatorial plane with respect to the plane of the sky (a CEB viewed edge-on would have an inclination of 90 degrees). The model excludes eccentric orbits and assumes all objects at the same orbital altitude. Using it, Socas-Navarro explores a Clarke Exobelt as it appears in the light curve of a star.
Our current Clarke belt would be orders of magnitude below the detection threshold for observers around other stars if they were using technologies similar to ours. Socas-Navarro argues that the Clarke belt around Earth is showing exponential growth, such that extrapolating it into the future would make it visible to other-world observers by the year 2200. The author considers this a reasonable extrapolation, though one highly dependent on future technology choices including, for example, space elevator systems, which could dramatically change access to these orbits and accelerate the emergence of a detectable signature.
As I read the Socas-Navarro paper, I was struck by its reliance on finding a civilization in a state of development close to our own. He is quite clear on this, saying his intention is “to explore the consequences of a direct extrapolation of our current trends,” acknowledging that even in our own near-future, we may take a different route in the population of our own Clarke belt.
Thus far, searches for technosignatures have assumed advanced technologies of the sort needed to dismantle planets and build Dyson spheres, although there is some discussion of atmospheric change through pollution or other civilizational activities. Despite the odds against finding a civilization just at the stage when it relied heavily on a Clarke Exobelt to maintain its essential services, the author thinks it prudent to keep our eyes open for this technosignature because of the deep uncertainties of forecasting what far more advanced cultures would do.
And we are improving the methods that might help us find such a Clarke Exobelt, even though they are not fine-tuned for such. Noting the difficulty of distinguishing between a CEB and a natural planetary ring system, the paper adds this:
While the similarity between a CEB and a ring system poses an initial difficulty, it also opens new opportunities. Existing interest in the physics of exorings and exomoons means that large efforts will be devoted in future photometric missions to examine rocky planet transits for evidence of such objects. This paper shows how future positive detections of orbital material may be further scrutinized for evidence of CEBs, making the search for moderately advanced technologies “piggyback” on such missions.
Thus we have a technosignature to add to our roster. One thing finding a CEB would imply is a still-functioning civilization — active maintenance would be required to keep objects in a crowded CEB within their proper orbits over long time-periods — which could not necessarily be said of a detected Dyson sphere, conceivably a relic of a long-dead culture. CEB detection is, as the author acknowledges, a ‘long shot.’ But having the widest range of technosignatures examined in the literature is only prudent. After all, who knows what we’ll find next?
The paper is Socas-Navarro, “Possible Photometric Signatures of Moderately Advanced Civilizations: The Clarke Exobelt.” The Astrophysical Journal Vol. 855, No. 2 (13 March 2018). Abstract / Preprint.
On Those Ceres Organics
I set off an interesting conversation with a neighbor when organic material was detected on Ceres, as announced last year by scientists using data from the ongoing Dawn mission. To many people, ‘organics’ is a word synonymous with ‘life,’ which isn’t the case, and straightening that matter out involved explaining that organics are carbon-based compounds that life can build on. But organic molecules can also emerge from completely non-biological processes.
So with that caveat in mind about this word, it’s still interesting that organics appear on Ceres, especially since water ice is common there, and we know of water’s key role in living systems. A new paper looks again at data from Dawn, whose detections were made with infrared spectroscopy using its Visible and Infrared (VIR) Spectrometer. The instrument, examining which wavelengths are reflected off Ceres’ surface and which are absorbed, detected organic molecules in the region dominated by Ernutet Crater on Ceres’ northern hemisphere.
Image: Last year, the Dawn spacecraft spied organic material on the dwarf planet Ceres, largest denizen of the asteroid belt. A new analysis suggests those organics could be more plentiful than originally thought. Credit: NASA / Rendering by Hannah Kaplan.
The paper’s lead author is Hannah Kaplan, now a postdoc at the Southwest Research Institute. What Kaplan and team did was to contrast the Dawn data with laboratory spectra from both terrestrial and extraterrestrial organic materials, the latter derived from meteorites. Comparing these materials with known composition, the researchers looked anew at the Ceres spectra to gain a better picture of their composition and abundance. This analysis could help us make the call on the origin of these organics, whether natural to Ceres or delivered by an impactor.
When they contrasted the VIR data from Ceres with the laboratory reflectance spectra of organic materials formed on Earth, the scientists found that between 6 and 10 percent of the spectral signature on Ceres could be explained by organic material. But folding in comparisons with organic material from carbonaceous chondrite meteorites, the team found a spectral reflectance that differed from the terrestrial.
“What we find is that if we model the Ceres data using extraterrestrial organics, which may be a more appropriate analog than those found on Earth, then we need a lot more organic matter on Ceres to explain the strength of the spectral absorption that we see there,” Kaplan said. “We estimate that as much as 40 to 50 percent of the spectral signal we see on Ceres is explained by organics. That’s a huge difference compared to the six to 10 percent previously reported based on terrestrial organic compounds.”
As to the question of origins, the impact theory would seem to favor a cometary solution, comets being known to display higher abundances of organics than asteroids. The accompanying problem here is that a cometary impact would produce enough heat to destroy such organics. On the other hand, formation on Ceres itself is problematic, because other than the small patches in the northern hemisphere region already noted, organics do not appear.
“If the organics are made on Ceres, then you likely still need a mechanism to concentrate it in these specific locations or at least to preserve it in these spots,” said Ralph Milliken, an associate professor in Brown University’s Department of Earth, Environmental and Planetary Sciences and a study co-author. “It’s not clear what that mechanism might be. Ceres is clearly a fascinating object, and understanding the story and origin of organics in these spots and elsewhere on Ceres will likely require future missions that can analyze or return samples.”
Thus a major lesson: The results depend on what kind of organic material you use to make sense of the Ceres data. The comparison with extraterrestrial organics seems sensible, and it’s one we’ll doubtless invoke again as we move toward upcoming asteroid encounters. It’s worth noting in that regard that Kaplan has recently joined the teaming operating OSIRIS-REx. The spacecraft will arrive at asteroid Bennu in August of this year, while the Japanese Hayabusa 2 is expected to reach asteroid Ryugu in a matter of weeks.
The paper is Kaplan et al., “New Constraints on the Abundance and Composition of Organic Matter on Ceres,” Geophysical Research Letters 21 May 2018 (abstract).
Protoplanets: The Next Detection Frontier
Some 4 million years old, the star HD 163296 is about 330 light years out in the direction of the constellation Sagittarius. When dealing with stars this young, astronomers have had success with data from the Atacama Large Millimeter/submillimeter Array (ALMA), teasing out features in protoplanetary disks filled with gas and dust, the breeding ground of new planets. As seen below, the ALMA imagery can be striking, a closeup look at a stellar system in formation.
Image: ALMA image of the protoplanetary disk surrounding the young star HD 163296 as seen in dust. Credit: ALMA (ESO/NAOJ/NRAO); A. Isella; B. Saxton (NRAO/AUI/NSF).
Tantalizingly, ALMA can show us rings in such disks, and the gaps that imply an emerging planet. But how do we know we’re actually looking at planets, rather than other phenomena we’re only now learning how to detect in such disks? New work from Richard Teague (University of Michigan) as well as a second effort by Christophe Pinte and team (Monash University, Australia) points us strongly toward the protoplanet interpretation. Both papers are in process at Astrophysical Journal Letters and available as preprints (see below).
In each case, the focus is not on the dust that is so visible in the image above but the distribution of carbon monoxide (CO) gas throughout the HD 163296 disk structure. ALMA is able to detect the millimeter-wavelength light that molecules of CO emit, while wavelength changes owing to the Doppler effect make it possible to discern the movement of the gas within the disk. Calling the precision involved in these studies ‘mind boggling,’ Teague coauthor Til Birnstiel (University Observatory of Munich) notes that in a system where gas rotates at about 5 kilometers per second, ALMA detected velocity changes as small as a few meters per second.
“Although dust plays an important role in planet formation and provides invaluable information, gas accounts for 99 percent of a protoplanetary disks’ mass,” says Teague coauthor Jaehan Bae of the Carnegie Institute for Science. “It is therefore crucial to study kinematics of the gas.”
Teague and team found disruption in the Keplerian rotation that gas would be expected to show, the orderly motion of objects around a central star. The emergence of localized disturbances within the gas would provide evidence for a planet in the making. And indeed, the researchers found two distinct patterns, one at roughly 80 AU, the other at 140 AU. Meanwhile, the team led by Christophe Pinte — likewise looking at anomalies in the flow of gas through detection of CO emissions rather than dust — detected a third planet-like pattern, this one at 260 AU. All three worlds, the scientists calculate, would be approximately similar in mass to Jupiter.
Image: Artist impression of protoplanets forming around a young star. Credit: NRAO/AUI/NSF; S. Dagnello.
We’re out on the edge here, just as exoplanet hunting itself was in the early 1990s as we approached the first detections. These days we can use radial velocity, transits and gravitational microlensing to spot planets, with the number of confirmed worlds rising steadily. Protoplanets are another story altogether, although the evidence for them continues to mount. The Teague paper explains the significance of the CO studies:
We have presented a new method which enables the direct measurement of the gas pressure profile. This allows for significantly tighter, and more accurate, constraints on the gas surface density profile than traditional methods. Furthermore, as this method is sensitive to the gap profile, it provides essential information about the gap width in the gas which is typically poorly constrained from brightness profiles.
And indeed, what the work gives us is a way to measure changes in the gas velocity and density that correlate to the observed perturbations in the protoplanetary disk. Pinte’s team, meanwhile, working with measurements of CO velocity in the disk, found a 15 percent deviation from expected Keplerian flow. The possible protoplanet they detect at approximately 260 AU could conceivably be detected via direct imaging. If it is, the question of its formation is interesting:
Can massive planets form at a distance of 250 au from the star? The location of giant planets in the outer regions of discs would be broadly consistent with gravitational instability. On the other hand, the timescale for core accretion may also be reasonable given that HD 163296 is a relatively old disc (≈ 5 Myr). The planet may also have undergone outward migration, depending upon the initial profile of the disc. It is beyond the scope of this Letter to speculate further.
Measuring the velocity of carbon monoxide in a protoplanetary disk is an indication of how fine-grained the ALMA data on HD 163296 are. The comparison of these observations with computer models show a fit with the patterns that would be expected for young planets. The evidence is not yet conclusive, but it’s clear that the developing science of protoplanet detection is gaining traction. Applying these methods to other well-defined disks should tell us more.
The papers are Teague et al., “A Kinematic Detection of Two Unseen Jupiter Mass Embedded Protoplanets” (preprint) and Pinte et al., “Kinematic evidence for an embedded protoplanet in a circumstellar disc” (preprint), both accepted at Astrophysical Journal Letters.
New Horizons from Within
Chasing New Horizons, by Alan Stern and David Grinspoon. Picador (2018), 320 pp.
Early on in Alan Stern and David Grinspoon’s Chasing New Horizons, a basic tension within the space community reveals itself. It’s one that would haunt the prospect of a mission to Pluto throughout its lengthy gestation, repeatedly slowing and sometimes stopping the mission in its tracks. The authors call it a ‘basic disconnect’ between how NASA makes decisions on exploration and how the public tends to see the result.
‘To boldly go where no one has gone before’ is an ideal, but it runs up against scientific reality:
…the committees that assess and rank robotic-mission priorities within NASA’s limited available funding are not chartered with seeking the coolest missions to find uncharted places. Rather, they want to know exactly what science is going to be done, what specific high-priority scientific questions are going to be answered, and the gritty details of how each possible mission can advance the field. So, even if the scientific community knows they really do want to go somewhere for the sheer joy and wonder of exploration, the challenge is to define a scientific rationale so compelling that it passes scientific muster.
Thus Alan Stern’s job as he began thinking about putting a probe past Pluto: Get the scientific community to see why Pluto/Charon was a significant priority for the advancement of science. And as this hard-driving narrative makes clear, advancing those priorities would not prove easy. But a few things helped, including the spectacular coincidence that Charon was discovered (by Jim Christy in 1978) just before it was about to begin a period of eclipses with Pluto, a period that would not recur for more than a century. When the eclipses began in 1985, Pluto was suddenly highly visible at planetary science conferences and we were learning a lot.
Chasing New Horizons follows Alan Stern’s efforts to use ensuing discoveries like the different composition of surface ices on Pluto and Charon and the observations of Pluto’s atmosphere to draw attention to mission possibilities. Beginning with a technical session at a American Geophysical Union meeting in 1989, Stern began arguing for what would become New Horizons, brainstorming with key Pluto scientists who would become known as the Pluto Underground on a mission the authors describe as “a subversive and unlikely idea, cooked up by a rebel alliance that seemed ill-equipped to take on an empire.”
It would prove to be quite a battle. A letter-writing campaign would develop, leading to an official NASA study of a possible Pluto mission, one led by Stern and fellow Plutophile Fran Bagenal, working with NASA engineer Robert Farquhar (who would die just months after the actual Pluto flyby). From here on it was a matter of keeping the mission visible, from pieces in Planetary Society publications to continuing talks at major conferences, where attendance was growing.
I won’t go into the intricacies of such entities as the Solar System Exploration Subcommittee, which would analyze the Farquhar report, or the personnel changes within NASA that affected the work — for that you’ll need to read the book, where the action becomes something of a pot-boiler given all the roadblocks that kept emerging, including mission cancellations — but as the New Horizons mission took early form, Pluto was likewise on the mind of engineers at JPL, who began concurrent work on a mission concept. NASA’s turn toward Rob Staehle’s Pluto Fast Flyby design was just one in a series of course changes for Stern and team. A Pluto Kuiper Express concept followed, then the formation of a NASA Science Definition Team.
Here’s a sample of how frustrating the on-again, off-again nature of New Horizons’ birth appeared to its proponents. Budget considerations had caught NASA’s eye and in the fall of 2000, a ‘stop-work order’ went out on all Pluto efforts:
Those of us who’d been working on it felt like we had been through a decade of hell running errands, with endless study variations from NASA Headquarters [says Stern]. How many iterations of this, how many committees had we been in front of, how many different planetary directors had we had at NASA, how many different everythings had we put up with? Big missions, little missions, micro-missions, Russian missions, German missions, nonnuclear missions, Pluto-only missions, Pluto-plus-Kuiper-Belt missions, and more…
New Horizons, as it would do repeatedly, came back to life, and we all know the result, but the first half of Chasing New Horizons is a fascinating and cautionary tale about how difficult mission design can be in a charged environment of tight money and competing proposals. Science surely had the last word again, because the need for a mission was now pressing, given that Pluto was moving further from the Sun in its orbit, its atmosphere could conceivably freeze out before a mission got there, and visibility considerations involved Pluto’s sharply tilted spin axis (122 degrees) and its effect on lighting across the globe.
As to the actual approach and flyby, you’ll find yourself back in those heady days, when the earliest images from New Horizons gradually gave way to more and more detail, and the stakes continued to rise even as the unexpected threatened to stymie the close approach. Exhaustive hazard searches helped Stern’s team scout the system, but the critical Core load — the lengthy command script that would get the spacecraft through its scientific observations — had to be uplinked. New Horizons received the Core load and then suddenly went silent.
Quick diagnosis made it likely that the spacecraft would restart using its backup computer, which did occur within a short time, but with the flyby near, timing was critical:
As more telemetry came back from the bird, they learned that all of the command files for the flyby that had been uploaded to the main computer had been erased when the spacecraft rebooted to the backup computer. This meant that the Core flyby sequence sent that morning would have to be reloaded. But worse, numerous supporting files needed to run the Core sequence, some of which had been loaded as far back as December, would also need to be sent again. Alice [Bowman] recalls, “We had never recovered from this kind of anomaly before. The question was, could we do it in time to start the flyby sequence…?”
With three days to do the job, the equivalent of weeks of work had to be done in three days. The task was completed with just three hours to spare. Exciting? Believe it. David Grinspoon’s method in Chasing New Horizons was to synthesize the thoughts of Alan Stern and others on the mission within a narrative that captures the drama of the event. Grinspoon is a fine stylist — search the archives here for my thoughts on his exceptional Earth in Human Hands (2016), and I’ve also written about his earlier book Lonely Planets (2003). Here he goes for clarity and narrative punch, presenting Stern’s insights inside an almost novelistic frame. This is a book you’ll want to read as we approach MU69.
New Horizons: The Beauty of Hibernation
I’ve always had a great interest in Iceland, stemming from my studies of Old Norse in graduate school, when we homed in on the sagas and immersed ourselves in a language that has changed surprisingly little for a thousand years. There’s much modern vocabulary, of course, but the Icelandic of 1000 AD is much closer to the modern variant than Shakespeare’s English is to our own. Syntactically and morphologically, Icelandic is a survivor, and a fascinating one.
New Horizons’ journey to Kuiper Belt Object MU69 occasions this reverie because the mission team has named the object Ultima Thule, following an online campaign seeking input from the public that produced 34,000 suggestions. The word ‘thule’ seems to derive from Greek, makes it into Latin, and appears in classical documents in association with the most distant northern areas then known. In the medieval era, Ultima Thule is occasionally mentioned in reference to Iceland, and sometimes to Greenland, and may have been applied even to the Shetlands, the Orkneys and, probably, the nearby Faroes. Northern and on the edge, that’s Ultima Thule.
The new Ultima Thule is a natural coinage, as New Horizons’ principal investigator Alan Stern (SwRI) has noted:
“MU69 is humanity’s next Ultima Thule. Our spacecraft is heading beyond the limits of the known worlds, to what will be this mission’s next achievement. Since this will be the farthest exploration of any object in space in history, I like to call our flyby target Ultima, for short, symbolizing this ultimate exploration by NASA and our team.”
Hence the beauty of space exploration. On Earth we eventually reach our Ultima Thule, whichever place we want to assign the name, whereas in space there’s always the next one. And indeed, New Horizons may get the chance to go after another Kuiper Belt Object after MU69. Future explorations will always find more distant targets in the cosmos.
Image: Artist’s impression of NASA’s New Horizons spacecraft encountering 2014 MU69, a Kuiper Belt object that orbits 1.6 billion kilometers beyond Pluto, on Jan. 1, 2019. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Steve Gribben.
Now 6 billion kilometers from Earth, New Horizons has exited hibernation as of 0212 EDT (0612 UTC) on June 5, with all systems in normal operation. We’re now in the process of uploading commands to the computers aboard the spacecraft to begin preparations for the Ultima Thule flyby, including science retrieval and subsystem and science instrument checkouts. Things are heating up — we’re not that far from August, when New Horizons will begin making observations of its target, imagery that will provide information about any needed trajectory adjustments.
But back to that hibernation, which this time around lasted 165 days. New Horizons is now fully ‘awake’ and will remain so until late 2020, when all data from the Ultima Thule encounter should have been sent back to Earth. Hibernation itself was an ingenious innovation that would maximize efficiency by reducing the cost of mission control staffing. After all, a sleeping bird requires only a skeleton crew to maintain basic communications during this period.
The sheer ingenuity of the New Horizons design comes across here. No other NASA mission has attempted hibernation, but the experience of missions like Voyager demonstrated how useful it could be. Voyager required about 450 people to run flight operations, according to David Grinspoon and Alan Stern in Chasing New Horizons. Contrast that with a New Horizons flight staff of fewer than 50 people.
The numbers are striking when you look at how the project team changed after launch as well. In the four years before New Horizons’ 2006 departure, more than 2500 people were involved in building, testing and launching the spacecraft. They included those working on the Radioisotope Thermoelectric Generator (RTG) that converts radioactive decay into electricity, the ground systems necessary to monitor the mission, and of course the rocket that would launch it.
Within a month after launch, all that had changed. “The big city that was New Horizons was reduced to a small town,” write Grinspoon and Stern. As the book memorably states:
During the long years of flight to Pluto, only a skeleton crew of flight controllers and planners, a handful of engineering ‘systems leads,’ the two dozen members of the science team, their instrument engineering staffs, and a small management gaggle was needed. Alan [Stern] recalls, “Just weeks after launch nearly everyone went their own way, and the project was reduced to a little crowd of about fifty belly buttons. All of a sudden I looked around and it hit me: there are just a few of us — a tiny team — and we’re the entire crew that’s going to fly this thing for a decade and 3 billion miles and plan the flyby of a new planet.”
Image: Flight controllers Graeme Keleher and Anisha Hosadurga, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, monitor New Horizons shortly after confirming the NASA spacecraft had exited hibernation on June 5, 2018. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Mike Buckley.
When New Horizons reached Pluto, 9.5 years had passed since launch, but because of hibernation, most of the craft’s primary systems only had 3.5 years of operational time clocked against them, which means the spacecraft was, for all intents and purposes, years younger than it would otherwise have been. Early hibernation periods tested out the concept not long after launch, easing into a process that soon increased hibernation periods to months at a time.
As New Horizons left its last hibernation period before the Pluto/Charon flyby, Alan Stern chose a ‘wake-up song’ for the occasion, a tradition dating back to Gemini 6 when flight controllers played ‘Hello Dolly’ to wake up astronauts Wally Schirra and Thomas Stafford. Stern chose ‘Faith of the Heart,’ a theme from the TV series Star Trek: Enterprise, with its lyric “It’s been a long road, getting from there to here.” Little did the team know at the time that the ‘heart’ of the title would be echoed by a famous feature on the surface of Pluto itself.
If you haven’t read Chasing New Horizons (Picador, 2018), I can’t recommend it strongly enough. This is the best inside account of a space mission I’ve yet read. Tomorrow I want to dig a little deeper into the book and talk about the New Horizons mission in context as we now begin the exciting process of preparing the craft for yet another encounter.
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