Centauri Dreams
Imagining and Planning Interstellar Exploration
Radio Map of Jupiter Anticipates Juno Findings
Interesting news about Jupiter this morning even as the Juno spacecraft crosses into the realm of Jupiter’s gravity. It was six days ago that Juno made the transition into Jupiter space, where the gravitational influence of Jupiter now dominates over all other celestial bodies. And it will be on July 4 of this year that Juno performs a 35-minute burn of its main engine, imparting a 542 meters per second mean change in velocity to the spacecraft for orbital insertion.
The spacecraft’s 37 flybys will close to within 5000 kilometers of the cloud tops. I only wish Poul Anderson could be alive to see some of the imagery. I always think of him in relation to Jupiter because of his stunning 1957 story “Call Me Joe,” describing the exploration of the planet by remote-controlled life forms (available in Anderson’s collection The Dark Between the Stars as well as various science fiction anthologies).
Image: Launched in 2011, the Juno spacecraft will arrive at Jupiter in 2016 to study the giant planet from an elliptical, polar orbit. Juno will repeatedly dive between the planet and its intense belts of charged particle radiation, traveling from pole to pole in about an hour, and coming within 5,000 kilometers of the cloud tops at closest approach. Credit: NASA/JPL-Caltech.
Our view of Jupiter has changed a lot since 1957, and Anderson’s low temperature, high pressure surface conditions have been ruled out, but the tale still carries quite a punch. As to Jupiter itself, today we get news that data from the Very Large Array (New Mexico) have been used to create the most detailed radio map ever made of its atmosphere. The work allows researchers to probe about 100 kilometers below the cloud tops using radio emissions at wavelengths where the clouds themselves are transparent.
Recent upgrades to the VLA have improved the array’s sensitivity by a factor of 10, a fact made apparent by the new Jupiter maps. Working the entire frequency range between 4 and 18 gigahertz, the team from UC-Berkeley supplements the Juno mission, anticipating its arrival to create a map that can put the spacecraft’s findings into context. Because the thermal radio emissions are partially absorbed by ammonia, it’s possible to track flows of the gas that define cloud-top features like bands and spots at various depths within the atmosphere.
We’re learning how the interactions between internal heat sources and the atmosphere produce the global circulation and cloud formation we see in Jupiter and other gas giant planets. The three-dimensional view shows ammonium hydrosulfide clouds rising into the upper cloud layers along with ammonia ice clouds in colder regions, while ammonia-poor air sinks into the planet amidst ‘hotspots’ (bright in radio and thermal infrared) that are low in ammonia and circle the planet just north of its equator.
“With radio, we can peer through the clouds and see that those hotspots are interleaved with plumes of ammonia rising from deep in the planet, tracing the vertical undulations of an equatorial wave system,” said UC Berkeley research astronomer Michael Wong.
Image: The VLA radio map of the region around the Great Red Spot in Jupiter’s atmosphere shows complex upwellings and downwellings of ammonia gas (upper map), that shape the colorful cloud layers seen in the approximately true-color Hubble map (lower map). Two radio wavelengths are shown in blue (2 cm) and gold (3 cm), probing depths of 30-90 kilometers below the clouds. Credit: Radio: Michael H. Wong, Imke de Pater (UC Berkeley), Robert J. Sault (Univ. Melbourne). Optical: NASA, ESA, A.A. Simon (GSFC), M.H. Wong (UC Berkeley), and G.S. Orton (JPL-Caltech).
Fine structure becomes visible in this work, especially in the areas near the Great Red Spot. The resolution is about 1300 kilometers, considered to be the best spatial resolution ever achieved in a radio map. “We now see high ammonia levels like those detected by Galileo from over 100 kilometers deep, where the pressure is about eight times Earth’s atmospheric pressure, all the way up to the cloud condensation levels,” says principal author Imke de Pater (UC-Berkeley). The work is reported in the June 3 issue of Science.
Image: In this animated gif, optical images of the surface clouds encircling Jupiter’s equator –including the famous Great Red Spot — alternate with new detailed radio images of the deep atmosphere (up to 30 kilometers below the clouds). The radio map shows ammonia-rich gases rising to the surface (dark) intermixed with descending, ammonia-poor gases (bright). In the cold temperatures of the upper atmosphere (160 to 200 Kelvin, or -170 to -100 degrees Fahrenheit), the rising ammonia condenses into clouds, which are invisible in the radio region. Credit: Radio: Robert J. Sault (Univ. Melbourne), Imke de Pater and Michael H. Wong (UC Berkeley). Optical: Marco Vedovato, Christopher Go, Manos Kardasis, Ian Sharp, Imke de Pater.
Earlier VLA measurements of ammonia levels in Jupiter’s atmosphere had shown much less ammonia than what the Galileo probe found when it plunged into the atmosphere in 1995. The new work resolves the issue by applying a technique to remove the blurring in radio maps that occurs because of Jupiter’s fast rotation. The UC-Berkeley team reports that it can clearly distinguish upwelling and downwelling ammonia flows using the new methods, preventing the confusion between the two that had led to the earlier mis-estimates of ammonia levels.
The paper is de Pater et al., “Peering through Jupiter’s Clouds with Radio Spectral Imaging,” Science 3 June 2016 (abstract).
Cometary Breakup and Reassembly
Yesterday’s look at organic compounds on Comet 67P/Churyumov-Gerasimenko needs to be augmented today by a just released study of the comet with implications for how all comets evolve. But first, a renewed pointer to the Kickstarter campaign for KIC 8462852, the unusual star whose light curves continue to baffle astronomers. Please consider contributing to the project, which would raise enough money ($100,000) to support a year of observations.
We’re about halfway through the campaign but not yet at the halfway point in funds. Have a look at the information provided on the Kickstarter page, or in my essay A Kickstarter Campaign for KIC 8462852, which also has the relevant links. We know the light curves of ‘Tabby’s Star’ are not periodic, so we need continuous monitoring to gain more data on what may be happening there. If we can raise the funds, the Las Cumbres Observatory Global Telescope Network, already supporting the project, can give us the multi-wavelength observations we need.
A Comet’s Evolution
The rubber-duck shape of Comet 67P/Churyumov-Gerasimenko has long been noted. The ‘neck’ of the comet is what connects the two larger lobes, as is obvious in the image below. As a new study led by Masatoshi Hirabayashi (Purdue) and Daniel Scheeres (University of Colorado) points out, two large cracks appear on the neck connecting the two larger lobes. The team simulated rotation rates for the twin-lobed assembly different from its actual 12-hour spin.
The result: Two cracks similar enough to those on 67P to show just how much stress is imparted. The rotation rate is variable in an object like this one because flybys of the Sun or of Jupiter can produce a gravitational torque. And as also appears in the photo, cometary outgassing is a factor, with compounds like carbon dioxide and ammonia sublimating from the surface. A fast enough spin produced by these factors can cause the two lobes to separate. Seven hours per rotation is what it takes for the head of the ‘duck’ to break off.
Image: Comet 67P’s distinctive shape tells us much about its history. Credit: ESA/Rosetta/NAVCAM, CC BY-SA IGO 3.0.
The researchers used numerical models that examined 1000 instances of 67P ‘clones’ under varying conditions over a 5000 year period. What Hirabayashi and Scheeres have learned is that the breakup and reassembly is an ongoing process as comets respond to these stresses. It’s also one that could last the lifetime of the comet. Says Scheeres:
“The head and body aren’t going to be able to escape from each other. They will begin orbiting each other, and in weeks, days or even hours they will come together again during a slow collision, creating a new comet nucleus configuration.”
As strange as it looks, Comet 67P may not be all that unusual. So far we have imaged seven comets at high resolution, five of which are bi-lobed. The researchers have learned that all of the bi-lobed comets have similar volume ratios between each lobe, an indication that the same cycle of disassembly and reassembly is happening in them as well. In some, there are similarities to what we find in a certain kind of asteroid. From the paper:
…bilobate nuclei observed by spacecraft encounters or ground-based radar have component volume ratios consistent with their nuclei being trapped in a similar cycle to that of 67P’s nucleus. For bilobate nuclei with a volume ratio between their lobes larger than about 0.2, the total energy of these systems will be negative after fission. This means that they are bounded in a similar way to some rubble pile asteroids; however additional sublimation effects could further erode or spin up the individual lobes before re-impact.
The process may be a major factor in cometary evolution, giving us insights into how these objects change over time:
Taking material density to be constant, we computed the volume ratios of the imaged bilobate nuclei of comets 1P/Halley, 8P/Tuttle, 19P/Borrelly, 67P and 100P/Hartley 2; we found that all of these nuclei had a volume ratio higher than 0.2… Observed nuclei with a single component might either be primordial, or have been part of a multi-component object, from which smaller parts are more easily shed.
Window into the Late Heavy Bombardment?
67P/Churyumov-Gerasimenko is a Jupiter-family comet orbiting the Sun every 6.5 years; such periodic comets are thought to originate in the Kuiper Belt, far beyond Neptune’s orbit. We learn that chaotic spin rate changes and the subsequent breaking into parts and reassembling probably caused the breakup of many ancient periodic comets originating at similar distances from the Sun. Enough erosion would have been produced by the continuing reconfiguration of their nuclei to reduce their ability to survive migration into the inner Solar System.
This could explain why comets were not a strong factor in the late heavy bombardment some four billion years ago, when numerous asteroids collided with the early terrestrial planets — two recent papers have made this case. “The reconfiguration cycles of short-period cometary nuclei,” the paper adds, “constitute a new evolutionary process that could affect their ability to survive during migration into the inner solar system.”
ESA’s mission to Comet 67P may, in other words, be giving us insights into the primordial bombardment that reshaped terrestrial worlds. The paper is Scheeres et al., “Fission and reconfiguration of bilobate comets as revealed by 67P/Churyumov-Gerasimenko,” Nature 1 June 2016 (abstract).
Rosetta’s Comet: Ingredients for Life
The thought that water and organic molecules might have arrived on the early Earth from the impacts of comets and asteroids has long been provocative, and our missions to nearby comets are now paying off with insights into the possibility. It was back in 2004 that the Stardust mission flew past Comet Wild 2, collecting dust samples that showed traces of the amino acid glycine. Possible contamination of the samples during their analysis left the question open, however.
Now we have news that the European Space Agency’s Rosetta mission has also found glycine — a significant organic compound that appears in proteins — at Comet 67P/Churyumov-Gerasimenko. The spacecraft’s ROSINA instrument (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) detected glycine in October of 2014, with later measurements taken during the August 2015 perihelion event, where cometary outgassing was at its peak.
Kathrin Altwegg (University of Bern), who led the study, calls this “…the first unambiguous detection of glycine in the thin atmosphere of a comet.” From the paper:
ROSINA’s double focusing mass spectrometer (DFMS) ionizes the incoming volatiles by electron impact ionization and detects the corresponding positively charged fragments. Unlike for meteorites or Stardust grains, there is no chemical sample preparation involved. Furthermore, the absence of a terrestrial source of glycine from the spacecraft is verified from observations before arrival at the comet. Therefore, glycine detected by DFMS has to be in this form already in the coma of the comet and is clearly not the result of contamination.
Although little glycine is released from the cometary surface, the detection of precursors to glycine formation, the organic molecules methylamine and ethylamine, is also significant. Glycine is the only amino acid known to be able to form without liquid water. Says Altwegg:
“We see a strong correlation of glycine to dust, suggesting that it is probably released from the grains’ icy mantles once they have warmed up in the coma, perhaps together with other volatiles. The simultaneous presence of methylamine and ethylamine, and the correlation between dust and glycine, also hints at how the glycine was formed.”
Image (click to enlarge): An ESA infographic detailing the recent work on organic compounds found at Comet 67P/Churyumov-Gerasimenko.
We also get word, in the paper published by Science Advances, that Rosetta found phosphorus at Comet 67P/C-G. The researchers argue that the number of organic molecules ROSINA has detected at the comet, now including glycine and phosphorus, make a strong case for comets as a delivery mechanism for prebiotic chemistry. This marks the first time phosphorus, an ingredient in the framework of DNA and RNA, has been found at a comet.
The presence of glycine, phosphorus, and a multitude of organic molecules, including hydrogen sulfide (H2S) and hydrogen cyanide (HCN), seen in the coma of 67P/Churyumov-Gerasimenko supports the idea that comets delivered key molecules for prebiotic chemistry throughout the solar system and, in particular, to the early Earth, drastically increasing the concentration of life-related chemicals by impact on a closed water body. The simultaneous presence of methylamine and the correlation between dust and glycine also suggest that the pathways for glycine formation on dust grain ices, as described for the ISM or the protosolar nebula, could also account for the cometary glycine.
The paper is Altwegg et al., “Prebiotic chemicals – amino acid and phosphorus – in the coma of comet 67P/Churyumov-Gerasimenko,” Science Advances, 27 May 2016 (abstract / full text).
Kepler-62f: Models for Habitability
So often planets described as ‘potentially habitable’ turn out to be over-rated — we look deeper into their composition and characteristics only to find that the likelihood of liquid water on the surface is slim. How to make more accurate calls on the matter of habitability? One way may be to combine orbital and atmospheric models, adjusting each with the known parameters of the planet in question. A new study does just that for the interesting world Kepler-62f.
About 1200 light years from Earth in the direction of the constellation Lyra, Kepler-62f has a radius 40 percent larger than Earth’s, which puts it well below the 1.6 RE demarcation line that is increasingly thought to define the difference between Earth-like worlds and planets that are more like Neptune. We’re probably looking at a rocky planet here. It’s also a planet that orbits its K-class primary at a distance that could place it in the outer regions of the habitable zone (as defined, again, by the presence of liquid water on the surface).
Image: Kepler-62f, shown here in an artist’s rendering, is far enough from its star that its atmosphere would need a high concentration of carbon dioxide to maintain liquid water on the planet’s surface. Credit: NASA Ames/JPL-Caltech/T. Pyle.
The new work on this world was conducted by Aomawa Shields (UCLA), working with Rory Barnes, Eric Agol, Benjamin Charnay, Cecilia Bitz and Victoria Meadows (all at the University of Washington, where Shields received her PhD). It examines the planet’s atmosphere to consider scenarios that could produce habitability. The team modeled climate possibilities using two different methods — the Community Climate System Model and the Laboratoire de Météorologie Dynamique Generic Model. Informing the climate modeling was the use of another computer model, HNBody, which was used to analyze and adjust the planet’s orbital parameters.
This UCLA news release calls the work the first time astronomers have combined the two different kinds of models to study exoplanet habitability. Says Shields:
“We found there are multiple atmospheric compositions that allow it to be warm enough to have surface liquid water. This makes it a strong candidate for a habitable planet.”
The necessary composition involves a great deal more carbon dioxide that we find in Earth’s atmosphere, necessary to keep the surface from remaining in a deep freeze. Remember, the planet circles a K-class star cooler than the Sun, and at a distance further away from the primary than the Earth from our star. By adjusting carbon dioxide levels in the atmospheric model, the team learned that given various orbital configurations, there were circumstances where habitability was possible. Some configurations work better than others, but the team found that even with an Earth-like level of carbon dioxide, there were rare but possible orbital configurations that allowed at least part of the year to be warm enough for liquid water.
From the paper:
At 41% of the modern solar constant, this planet will likely require an active carbonate silicate cycle (or some other means by which to produce high greenhouse gas concentrations) to maintain clement conditions for surface liquid water. With 3 bars of CO2 in its atmosphere and an Earth-like rotation rate, 3-D climate simulations of Kepler-62f yielded open water across ?20% of the planetary surface at the upper limit of the stable eccentricity range possible for the planet, provided that it has an extreme obliquity (90°). With 5 bars of CO2 in its atmosphere, a global mean surface temperature similar to modern-day Earth is possible for the full range of stable eccentricities and at the present obliquity of the Earth. This higher CO2 level is therefore optimal, as it is below the maximum CO2 greenhouse limit, and generates habitable surface conditions for a wide range of orbital configurations throughout the entire orbital period of the planet. If Kepler-62f is synchronously rotating, CO2 concentrations above 3 bars would be required to distribute sufficient heat to the night side of the planet to avoid atmospheric freeze-out.
There is a faint chance that with CO2 levels like the Earth’s, Kepler-62f could experience surface melting of ice sheets on an annual cycle. This would depend on a high degree of axial tilt, or obliquity — the angle between the planet’s rotational axis and its orbit. The Earth’s obliquity is 23 percent. An axial tilt of 60° or higher, coupled with summer solstice at a given hemisphere occurring at the planet’s closest approach to its star, could produce this annual effect, allowing surface conditions that were at least periodically habitable.
The paper is Shields et al., “The Effect of Orbital Configuration on the Possible Climates and Habitability of Kepler-62f,” published online by Astrobiology 13 May 2016 (abstract / preprint).
Interstellar Flight in Congressional Report
I hadn’t planned the conjunction of the Breakthrough Starshot forum’s opening here on Centauri Dreams and the interesting news out of the NASA budget for 2017, but some things just fall into your lap. In any case, what happened in Washington makes a nice follow-up to yesterday’s post, considering that it calls up visions of fast probes to Alpha Centauri, and in a document coming out of the U.S. House of Representatives, of all things. As more than a few readers have noted, it’s not often that we hear interstellar issues discussed in the halls of Congress.
Call for a New Interstellar Study
The specifics are that space-minded John Culberson (R-TX), who has championed space exploration with abandon, has made sure that NASA will look at the possibilities of interstellar travel. Culberson chairs the House of Representatives sub-panel in charge of NASA appropriations, and the call for interstellar study comes in a report that accompanies the bill establishing the agency’s budget for the coming year. You can see the report as submitted by Culberson online. Let me quote the relevant paragraph. First, the statement of the problem:
Interstellar propulsion research.—Current NASA propulsion investments include advancements in chemical, solar electric, and nuclear thermal propulsion. However, even in their ultimate theoretically achievable implementations, none of these could approach cruise velocities of one-tenth the speed of light (0.1c), nor could any other fission-based approach (including nuclear electric or pulsed fission).
Now the call for study:
The Committee encourages NASA to study and develop propulsion concepts that could enable an interstellar scientific probe with the capability of achieving a cruise velocity of 0.1c. These efforts shall be centered on enabling such a mission to Alpha Centauri, which can be launched by the one-hundredth anniversary, 2069, of the Apollo 11 moon landing. Propulsion concepts may include, but are not limited to fusion-based implementations (including antimatter-catalyzed fusion and the Bussard interstellar ramjet); matter-antimatter annihilation reactions; multiple forms of beamed energy approaches; and immense ‘sails’ that intercept solar photons or the solar wind. At the present time, none of these are beyond technology readiness level (TRL) 1 or 2.
And finally, the course to follow:
The NASA Innovative Advanced Concepts (NIAC) program is currently funding concept studies of directed energy propulsion for wafer-sized spacecraft that in principle could achieve velocities exceeding 0.1c and an electric sail that intercepts solar wind protons. Over the past few years NIAC has also funded mission-level concept studies of two fusion-based propulsion concepts. Therefore, within one year of enactment of this Act, NASA shall submit an interstellar propulsion technology assessment report with a draft conceptual roadmap, which may include an overview of potential advance propulsion concepts for such an interstellar mission, including technical challenges, technology readiness level assessments, risks, and potential near-term milestones and funding requirements.
Notice a couple of things here. First, keying a major effort to a significant anniversary is interesting as a motivational driver. Hence the call for reaching the goal of a launch by the one-hundredth anniversary of the Apollo 11 landing. As noted in these pages at the time, Yuri Milner’s Breakthrough Starshot was announced in conjunction with another such milestone, the anniversary of Yuri Gagarin’s orbital flight. Humans love to link big ideas with major events in the past as a way of goal-setting and, I suppose, putting a new idea into a broader context.
Note as well some of the parameters. Culberson talks about a spacecraft reaching ten percent of lightspeed, while Breakthrough Starshot goes for twenty percent. And while Starshot focuses tightly on small sails driven by phased laser array, Culberson’s call to NASA incorporates propulsion concepts ranging from sails to antimatter and even Bussard ramjets. Moreover, the report makes a nod to fusion-based propulsion as studied by the NASA Innovative Advanced Concepts program (NIAC). NASA is called upon to submit a technology assessment within a year of the enactment of the budget bill.
Dr. Forward Goes to Washington
If any of this sounds familiar, it may be because the only other time interstellar flight was considered in the U.S. Congress at any level of detail was when Robert Forward made an appearance before the Subcommittee on Space Science and Applications of the House Committee on Science and Technology. That was in 1975, when interstellar flight was rarely discussed outside of science fiction magazines, and the work of scientists like Forward appeared largely at conferences where interstellar issues were only a small part of the proceedings. There was, of course, no Internet, and media attention was scant.
Forward’s “A National Space Program for Interstellar Exploration” was as ambitious as it gets, calling for the launch of automated probes to nearby stellar systems by the turn of the 21st Century, with manned exploration to commence a scant 25 years later. With a budget that today seems modest, Forward called for ‘a few million dollars a year’ during the initial study phase, climbing into the multi-billion dollar range as the program began launching its first automated probes. As always, Forward thought big, as witness this:
Development of man-rated propulsion systems would continue for 20 years while awaiting the return of the automated probe data. Assuming positive returns from the probes, a manned exploration starship would be launched in 2025 AD, arriving at Alpha Centauri 10 to 20 years later.
Image: Interstellar theorist Robert Forward, whose work on beamed propulsion began in the early 1960s.
All that is by way of placing Rep. Culberson’s call to NASA in historical context. What Forward didn’t have when he made his recommendations was an ongoing privately funded effort like Breakthrough Starshot to offer a parallel track of development. It would be fascinating to know how he would have played that card. Breakthrough Starshot aims to spend its $100 million endowment on shaking out the basic concepts involved in a sail mission to Alpha Centauri. Forward would have been all over its phased laser array concept and we’re the poorer for not having his insights, especially on the issue of Earth- vs. space-based deployment.
The parallels between Culberson’s report and the Starshot studies are interesting if only in that both make reference to Philip Lubin’s work at NIAC on beamed propulsion. Lubin (UC-Santa Barbara) is a major figure in the Starshot effort, but his work goes back several years at NIAC, and thus offers ideas to both projects. Moreover, the Starchip concept — a ‘nano-spacecraft’ — being studied by Breakthrough Starshot is heavily dependent on Mason Peck’s work at Cornell, which also has had NIAC support. So NASA can draw on NIAC.
In the broader sense, though, both NASA and Starshot owe their inspiration on the propulsion side to Forward and the many colleagues who developed the core ideas of beamed propulsion over the past fifty years. Beaming to a sail has long been under investigation, though never so publicly. In the near future, I’ll be publishing an extended take on the history of these studies and how we have arrived at today’s laser sail concepts.
Image: A beamed lightsail as envisioned by the space artist Adrian Mann.
Will NASA and Breakthrough Starshot duplicate each other’s efforts? It’s not likely given current funding constraints, and whether it’s based at MSFC Huntsville or the Jet Propulsion Laboratory, the NASA effort outlined by Culberson calls only for an assessment of an interstellar mission. But having interstellar flight’s new media prominence so prominently reinforced by its introduction into a Congressional report on the NASA budget can’t hurt as we launch a serious look at what it takes to reach Alpha Centauri. We’ll soon learn what kind of synergies may exist.
Forward’s presentation to Congress can be found in “A National Space Program for Interstellar Exploration,” Future Space Programs 1975, vol. VI, Subcommittee on Space Science and Applications, Committee on Science and Technology, U.S. House of Representatives, Serial M, 94th Congress (September, 1975).
Breakthrough Starshot: ‘Challenges’ Forum Opens
Ever since coming back from the Breakthrough Discuss meeting in Palo Alto, I have been pondering the enormous issues the Breakthrough Starshot project will encounter. Getting a tiny spacecraft up to twenty percent of lightspeed is only the beginning of an effort that has to deal with power generation, a phased laser array of enormous strength and complexity, the miniaturization of critical components, lightsail integrity under thrust and much more.
These topics were freely discussed in Palo Alto, and especially at the Yuri’s Night party that Yuri Milner threw for the assembled conference goers. When I talked to Milner at the party, he suggested an idea that we have been working on ever since. In order to keep the discussion on the critical issues involving Breakthrough Starshot in front of the interstellar community, why not set up a linkage between the discussion areas of the Breakthrough site and Centauri Dreams? This site would maintain its usual structure and separate comments, but it would then include a section specifically devoted to pursuing the Breakthrough Starshot concept.
I am the world’s poorest programmer, but a crack team from Breakthrough Initiatives, led by Stepan Torchyan and including Peter Petrov and Konstantin Efimov knew exactly what to do. As of this morning, the new section goes live. You’ll find the ‘Challenges’ forum accesible through the ‘Breakthrough Starshot’ tab at the top of the Centauri Dreams logo, Click on ‘Breakthrough Starshot’ and you’ll see it is set up as a series of forums, each of them dealing with a single major issue for the project. A ‘Challenges’ link also appears on the Breakthrough Initiatives site.
What’s happening here is that any comments Centauri Dreams readers place in one of these forums will be mirrored on the Breakthrough Initiatives site, while comments posted there will appear on the ‘Challenges’ forum pages on this site. As long-time readers know, Centauri Dreams doesn’t require a login in order to post, but ‘Challenges’ does. You can set up a password on the ‘Challenges’ page. Click the ‘Breakthrough Starshot’ tab, then click ‘Sign In’ and, on the ensuing page, ‘Sign Up.’
When you go to the new forum, you’ll see that the list of topics is lengthy, and I hope that we can continue the many good discussions we’ve already had on Centauri Dreams in this new venue, even as we follow the project with articles and comments on Centauri Dreams itself. Many of the current topics came under discussion in Palo Alto, but as Breakthrough Starshot begins its work this summer, each will come into sharper focus.
Simply put, there could be a deal-breaker almost anywhere on the list of Challenges. If we build the phased laser array to boost a Starchip up to a substantial percentage of c, would the sail be stable under the beam? Would the phased array work as we hope through the atmosphere? What about objects in the beam’s path — a bird, an airplane? What of the collision potential for a spacecraft moving at these velocities in cruise, and how do we manage to adjust the spacecraft’s course on the way? And a huge one: How do we manage data return considering the minute size of the Starchip we hope to send to Alpha Centauri?
Have a look at the Challenges forum as we begin to see how it will work. Stepan Torchyan’s team will check into any bug reports if problems arise, and after an initial shakedown, we should be able to add to the Breakthrough Starshot discussion daily. I’m happy to be able to bring these forums to the attention of the Centauri Dreams audience considering how much I’ve learned from readers here since I began the site in 2004. I have no doubt we’ll be able to make a contribution to this ongoing study to achieve what I’ve always dreamed about, a human technology arriving intact and returning data from the Alpha Centauri system.
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