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Spacecoaches and Beamed Power

by Paul Gilster | Apr 29, 2016 | Missions | 35 Comments

If you're planning to make it to the International Space Development Conference in San Juan, Puerto Rico next month, be advised that Brian McConnell will be there with thoughts on a subject we've discussed in several earlier posts: A 'spacecoach' that uses water as a propellant and offers a practical way to move large payloads (and crews) around the Solar System. Based in San Francisco, Brian is a technology entrepreneur who doubles as a software/electrical engineer. In the essay below, he looks at the spacecoach in relation to the Breakthrough Starshot initiative, where synergies come into play that may benefit both concepts. by Brian McConnell The spacecoach is a design pattern for a reusable solar electric spacecraft, previously featured on Centauri Dreams here and developed in A Design for a Reusable Water-Based Spacecraft Known as the Spacecoach (Springer Verlag), which I wrote with Alex Tolley. It primarily uses water as its propellant. This design has numerous benefits, chief...

Light’s Echo: Protoplanetary Disk Examined

by Paul Gilster | Apr 28, 2016 | Exoplanetary Science | 2 Comments

The star YLW 16B, about 400 light years from the Earth, has roughly the same mass as the Sun. But unlike the Sun, a mature 4.6 billion year old star, YLW 16B is a scant million years old, a variable of the class known as T Tauri stars. Whereas our star is relatively stable in terms of radiation emission, the younger star shows readily detectable changes in radiation, a fact that astronomers have now used in combining data from the Spitzer space telescope with four ground-based instruments to learn more about the dimensions of its protoplanetary disk. Image: This illustration shows a star surrounded by a protoplanetary disk. Material from the thick disk flows along the star's magnetic field lines and is deposited onto the star's surface. When material hits the star, it lights up brightly. Credit: NASA/JPL-Caltech. The method is called photo reverberation, and it takes advantage of the fact that when the star brightens as material from the turbulent disk falls onto its surface, some of...

Beneath a Methane Sea

by Paul Gilster | Apr 27, 2016 | Outer Solar System | 17 Comments

Back when Cassini was approaching Saturn and we all anticipated the arrival of the Huygens payload on the surface, speculation grew that rather than finding a solid surface, Huygens might 'splash down' in a hydrocarbon sea. I can remember art to that effect in various Internet venues of the time. In the event, Huygens came down on hard terrain, but since then Cassini's continuing surveys have shown that seas and lakes do exist on the moon. Over 1.6 million square kilometers (about two percent of the surface of Titan) are covered in liquid. Image: Ligeia Mare, shown here in a false-colour image from the international Cassini mission, is the second largest known body of liquid on Saturn's moon Titan. It measures roughly 420 km x 350 km and its shorelines extend for over 3,000 km. It is filled with liquid methane. The mosaic shown here is composed from synthetic aperture radar images from flybys between February 2006 and April 2007. Credit: NASA/JPL-Caltech/ASI/Cornell. The liquid, of...

Gravitational Lensing with Planets

by Paul Gilster | Apr 26, 2016 | Astrobiology and SETI | 27 Comments

As we've been talking about the Sun's gravitational focus, it's interesting to reflect on the history of its study. Albert Einstein's thinking about gravitational lensing in astronomy was explicitly addressed in a 1936 paper, but it wasn't until 1964 that Stanford's Sydney Liebes produced the mathematics behind lensing at the largest scale, working with the lensing caused by a galaxy between the Earth and a distant quasar. Dennis Walsh, a British astronomer, found the first actual quasar 'image' produced in this way back in 1978, with Von Eshleman's study of the Sun's lensing the following year including the idea of sending a spacecraft to 550 AU. SETI was on Eshleman's mind, for he pondered what could be done at the 21 cm wavelength, the SETI 'waterhole,' and so did Frank Drake, who presented a paper on the concept in 1987. If you have a good academic library near you, its holdings of the Journal of the British Interplanetary Society for 1994 will include the proceedings of the...

Starshot and the Gravitational Lens

by Paul Gilster | Apr 25, 2016 | Missions | 54 Comments

Although the idea of a mission to the Sun's gravitational lens has been in Claudio Maccone's thinking for a long time, it has never been linked with the financial resources of a concept study like Breakthrough Starshot. The Italian physicist led a conference on mission concepts in the early 1990s and submitted a proposal for an ESA mission in 1993. What's striking to me is that throughout that time, Maccone has explored aspects of the mission he calls FOCAL that at one point seemed far too futuristic for our era. Could we, for example, do SETI with a FOCAL mission? Could we use it to enhance communications with an interstellar probe? The answer to both is yes, but the problem was pushing a spacecraft out to 550 AU in the first place, a challenge involving flight times of many decades. Then the Breakthrough Starshot initiative emerged and suddenly Maccone found himself in Palo Alto talking about a well-funded study, one that looked to FOCAL to support interstellar probes both in terms...

Starshot: Concept and Execution

by Paul Gilster | Apr 22, 2016 | Missions | 54 Comments

Because I get irritable when I don't get my walking in every day, I made sure when I arrived in Palo Alto to cram as much as I could into the day before Breakthrough Discuss began. That meant heading out from the hotel just after noon and putting in about five miles. Palo Alto is a very walkable place and I found myself ambling up and down shady streets past gardens bright with spring flowers. We had superb weather for the entire conference, but naturally when things got going, both days were crammed with talks and long walks were out of the question. But the day before, as I walked, I pondered the schedule of the conference, wondering how a mission to Alpha Centauri fit into the overall plan. In addition to the $100 million going toward Breakthrough Starshot, Breakthrough Initiatives has also put up $100 million for its SETI project, which has already begun operations at Green Bank (West Virginia) and is slated to operate at the Parkes dish in Australia as well, giving SETI the...

Breakthrough Discuss: SETI in the Optical

by Paul Gilster | Apr 21, 2016 | Astrobiology and SETI | 36 Comments

At the Yuri's Night party on Yuri Milner's Palo Alto estate, I found myself thinking about a novel, Allen Steele's Arkwright. Like Breakthrough Starshot, initial work on the starship in the book is funded by a wealthy man who wants to see a human future among the stars. The propulsion method is a beam-driven sail, though at that point the comparisons get strained, for Steele is assuming a much larger craft and a mission of colonization rather than a flyby. Even so, there was enough similarity to make a book I had been reading on the airplane seem prescient. The music on Yuri's Night was loud, the gathering crowd relaxed, and I had imagined it would be an entirely social event, but after a time we were called in to watch a short video about Starshot and then participated in a question-and-answer session with some of the project's principal players, including Milner himself. It was a good chance to hear some of the challenges the project faces examined, and tomorrow we'll look at many...

Alpha Centauri, SETI and Detectability

by Paul Gilster | Apr 20, 2016 | Astrobiology and SETI | 23 Comments

Heading for the hotel lobby the first night of the Breakthrough Discuss meeting, I thought about a major theme of the Breakthrough Starshot initiative: Making things smaller. Robert Forward wrote about sails hundreds of kilometers in diameter, and vast lenses deep in the Solar System to collimate a laser beam that would drive them. But Breakthrough Starshot is looking at a sail four meters across, carrying a payload more like a smartphone than a cargo ship. That big lens in the outer system? No longer needed if we can power up the sail close to home. How to Look at Alpha Centauri Digitization works wonders, and Moore’s Law takes us into ever smaller and more tightly packed realms on silicon chips. The trend affects every aspect of spaceflight and astronomy, as witness ACEsat, a small coronagraph mission with an explicit mission, the search for planets around Alpha Centauri A and B. Ruslan Belikov (NASA Ames), working with Northrop Grumman, led the team that conceived this mission,...

Focus on Alpha Centauri

by Paul Gilster | Apr 19, 2016 | Exoplanetary Science | 22 Comments

At Palo Alto's superb Amber India, I was thinking about Alpha Centauri. There are several Amber India locations in the Bay area, but the Palo Alto restaurant dishes up, among other delights, a spicy scallop appetizer that is searingly hot and brilliantly spiced. Greg and Jim Benford were at the table, Claudio Maccone and my son Miles. It was the night before Breakthrough Discuss convened. And while the topics roamed over many aspects of spaceflight, it was that star system right here in our solar neighborhood that preoccupied me. How lucky could we be to have not one but two stars this close and so similar to our own? Centauri A is a G-class star, Centauri B a K, and if we hit the jackpot, we could conceivably find planets orbiting both. Then there is Proxima Centauri, an M-dwarf that is the closest star of all to the Solar System. The presence of so many astronomers on the Breakthrough Discuss roster made it clear we'd get the latest on the hunt for planets here, a vital factor as...

Breakthrough Discuss: Initial Thoughts

by Paul Gilster | Apr 18, 2016 | Culture and Society | 26 Comments

The Breakthrough Initiatives conference I've just returned from, called Breakthrough Discuss 2016, had been a bit of a puzzle going in. Still bleary after an early morning arrival in Palo Alto, I was looking forward to getting to the Stanford campus for the first sessions the next day. Breakfasting at a small cafe near the hotel, I mulled over the possibilities. The emphasis was on astronomy, given the list of attendees, which included top names in the exoplanet hunt, but of course Breakthrough Initiatives is also funding a major SETI effort, so that would be a theme. And then there was the looming presence of the just announced Breakthrough Starshot. Balancing all this out looked to be a challenge, but as it turned out, there was a strong cross-pollination among the various themes, with the Starshot -- an unmanned flyby of Alpha Centauri and an infrastructure to sustain a further interstellar effort -- woven into the proceedings. I knew I'd come back with material for a week's worth...

On Track for ‘Breakthrough Discuss’

by Paul Gilster | Apr 14, 2016 | Culture and Society | 18 Comments

Expect no new posts until Monday and a slowdown in comment moderation as I attend the Breakthrough Initiatives event in Palo Alto. As has been my practice at previous such events, I won't try to cover the talks and discussions live. While 'live blogging' has its place and seems to work for things like product introductions, I don't find it useful for scientific conferences, where I need to take lots of notes and think about the implications of what I've written. But I'll come back from Stanford with plenty of things to talk about, and we'll use all of next week sorting them out. Dinner tonight with Jim and Greg Benford, my son Miles, and my old friend Claudio Maccone, with whom I'll be talking SETI, the FOCAL mission (to the Sun's gravity lens), and the best methods of data retrieval for a mission like Breakthrough Starshot. Many more good discussions ahead. SETI is a big part of this conference, but Alpha Centauri looms large.

The Odds on Starshot

by Paul Gilster | Apr 13, 2016 | Missions | 112 Comments

Yesterday's announcement of Breakthrough Starshot brought an email from exoplanet hunter Greg Laughlin (UC-Santa Cruz), whose work has been an inspiration to me since the early days of Centauri Dreams. One of Greg's new projects, working with Anthony Aguirre (Foundational Questions Institute) and several other colleagues, is a website called Metaculus, which bills itself as "a community dedicated to generating accurate predictions about future real-world events by aggregating the collective wisdom, insight, and intelligence of its participants." In other words, this is a kind of prediction market space for science and tech issues. Breakthrough Starshot fits the bill here exactly, because Metaculus is all about the probability of future events, some of which can be predicted to a high degree, while others are purely a matter of calculated odds. The site is open to all and contains the basic information about its methods, and any logged in user can propose a question for consideration....

Breakthrough Starshot: Mission to Alpha Centauri

by Paul Gilster | Apr 12, 2016 | Missions | 133 Comments

Here on Centauri Dreams we often discuss interstellar flight in a long-term context. Will humans ever travel to another star? I've stated my view that if this happens, it will probably take several hundred years before we develop the necessary energy resources to make such a mission fit within the constraints of the world's economy. This, of course, assumes the necessary technological development along the way — not only in propulsion but in closed-loop life support — to make such a mission scientifically plausible. I get a lot of pushback on that because nobody wants to wait that long. But overall, I'm an optimist. I think it will happen. Let's attack the question from another direction, though, and leave human passengers for a later date, as Yuri Milner's Breakthrough Initiatives, aided by Stephen Hawking, is doing today in a New York news conference. What if we talk about unmanned missions? What if, in fact, the question is: How soon can we put a scientific payload...

The Snowbank Orbit, Redux

by Paul Gilster | Apr 8, 2016 | Missions | 48 Comments

We haven't yet found Planet Nine, but the evidence for its existence is solid enough that we can start thinking about its possibilities as a mission target. That work falls in this essay to Adam Crowl, a Centauri Dreams regular whose comments on articles here began not long after I started the site. An active member of the Project Icarus attempt to re-design the 1970s Project Daedalus starship, Adam is also the author of Crowlspace, where his insights are a frequently consulted resource. Today he harkens back to a 1960s science fiction story that has given him notions about a way not only to reach Planet Nine but to establish orbit around it. by Adam Crowl Fritz Leiber is better known for his fantasy and SF-fantasy, but he could write hard-SF too. A fine example is his 1962 story, "The Snowbank Orbit", the title of which alludes to World War II tales of pilots surviving bailouts without parachutes by plunging into snow-drifts. Five spacecraft, racing towards Uranus at 100 miles per...

A Young, Free-Floating Jupiter Analog in TW Hydrae

by Paul Gilster | Apr 7, 2016 | Exoplanetary Science | 7 Comments

A stellar association is a loose grouping of stars of similar spectral type and age that share a common motion. About 90 percent of all stars are thought to originate as members of associations. The TW Hydrae association (TWA) is a case in point: The group is made up of about thirty young stars, each thought to be roughly ten million years old. This is the youngest grouping of stars in the neighborhood of the Sun. You may recall 2M1207, which has turned up in these pages before, a brown dwarf member of the TWA that has a companion of planetary mass. Now we learn of another exotic find, a young, bright free-floating planet-like object. Jonathan Gagné (Carnegie Institution for Science) used the FIRE spectrograph on Carnegie's Baade 6.5-m telescope in Chile to measure the line-of-sight velocity of the object, known as 2MASS J1119-1137. This along with the sky motion of the object allowed researchers to make the definitive call that 2MASS J1119-1137 is indeed a member of the TW...

Supernova at Twilight

by Paul Gilster | Apr 6, 2016 | Deep Sky Astronomy & Telescopes | 8 Comments

In his novel The Twilight of Briareus (John Day, 1974), Richard Cowper, who in reality was John Middleton Murry, Jr., wrote about a fictitious star called Delta Briareus that goes supernova (true, there is no constellation called Briareus, but bear with me). Because it is only 130 light years out, the supernova showers the Earth with radiation, with consequences that are in some cases obvious, in others imaginative in the extreme. It's a good read, one that at least one critic, Brian Stableford, has compared to J. G. Ballard's early disaster novels. The novel contrasts an earthy domesticity with the celestial display that soon shatters it. It's worth quoting a patch of the book: It so happened that I, in common, no doubt, with several million others -- was among the first in England to observe that 'majestic effulgence' within seconds of its arrival. At about twenty past nine on the Tuesday evening I switched off the telly and suggested to Laura that we could do worse than saunter...

SETI: A New Kind of ‘Water Hole’

by Paul Gilster | Apr 5, 2016 | Uncategorized | 28 Comments

Some of you may recall an episode of Star Trek: The Next Generation in which the inhabitants of a planet called Aldea use a planetary defense system that includes a cloaking device. The episode, “When the Bough Breaks,” at one point shows the view from the Enterprise’s screens as the entire planet swims into view. My vague recollection of that show was triggered by the paper we looked at yesterday, in which David Kipping and Alex Teachey discuss transit light curves and the ability of a civilization to alter them. After all, if an extraterrestrial culture would prefer not to be seen, a natural thought would be to conceal its transits from worlds that should be able to detect them along the plane of the ecliptic. Light curves could be manipulated by lasers, and as we saw yesterday, the method could serve either to enhance a transit, thus creating a form of METI signaling, or to conceal one. In the latter case, the civilization would want to create a change in brightness that would...

A Transit Signature for SETI?

by Paul Gilster | Apr 4, 2016 | Astrobiology and SETI | 16 Comments

David Kipping and Alex Teachey have a new paper out on the possibility of ‘cloaking’ a planetary signature. The researchers, both at Columbia University, make the case that any civilization anxious to conceal its existence -- for whatever reason -- would surely become aware that all stars lying along its ecliptic plane would see transits of the home world, just as its own scientists pursued transit studies of planets around other stars. And it turns out there are ways to make sure this signal is masked by adjusting the shape of the planet’s transit light curves. Now this is a fascinating scenario as presented by the head of the Hunt for Exomoons with Kepler, whose business it is to know about the slightest of variations in light curves because they may contain information about exomoons or rings. Thus Kipping is a natural to look into the artificial manipulation of light curves, a study with definite SETI implications. Because methods like these work in two directions -- a...

John Ford Fishback and the Leonora Christine

by Paul Gilster | Apr 1, 2016 | Missions | 41 Comments

Like the Marie Celeste, the Leonora Christine is a storied vessel, at least among science fiction readers. In his 1967 story "To Outlive Eternity," expanded into the novel Tau Zero in 1970, Poul Anderson described the starship Leonora Christine's stunning journey as, unable to shut down its runaway engines, it moved ever closer to the speed of light. Just how a real Leonora Christine might cope with the stresses of a ramjet's flight into the interstellar deep is the subject of Al Jackson's latest, which draws on memories not only of Robert Bussard, who invented the interstellar ramscoop concept, but a young scientist named John Ford Fishback. by A. A. Jackson Project Pluto - a program to develop nuclear-powered ramjet engines - must have been on Robert Bussard's mind one morning at breakfast at Los Alamos. Bussard was a project scientist-engineer on the nuclear thermal rocket program Rover -- Bussard and his coauthor DeLauer have the two definitive monographs on nuclear propulsion...

Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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